Five-fingers and Lancewoods

Longtime readers of this blog will know that my knowledge of plants has always been fairly rudimentary. As a young'un, I only ever learnt to distinguish some of the more common and visible varieties. As a student, I did take a few botany classes, but only really enough to learn that plant biology is complicated and terrifying. Since then, I've continued in much the same vein. But for today's post, I'm looking at something I do recall being aware of in my youth: the lancewoods and five-fingers of the genus Pseudopanax.

Horticultural variant of coastal five-finger Pseudopanax lessonii, copyright Leonora Enking.

Pseudopanax is a genus of a dozen species of small tree (mostly growing about five to seven metres in height) found only in New Zealand (Perrie & Shepherd 2009). Various species have also been assigned to the genus from locations around the Pacific (China, Tasmania, New Caledonia and Chile) but recent studies have lead to their exclusion. A handful of New Zealand species previously included in Pseudopanax have also been separated as the genus Raukaua (Mitchell et al. 1997). The historical taxonomy of the group is confusing, with species being variously attributed to genera Panax, Nothopanax, Neopanax and Polyscias. Things seem to have settled down a bit in recent years but there is still the possibility we may one day see Neopanax rise again (Perrie & Shepherd 2009).

Chatham Islands lancewood Pseudopanax chathamicus, copyright Krzysztof Ziarnek, Kenraiz.

Pseudopanax belongs to the family Araliaceae, a group that is primarily composed of tropical and subtropical shrubs and trees. Araliaceae are commonly referred to as "the ivy family", after one of their best-known members, the common ivy Hedera helix, but, as is not uncommon when a tropical family gets named after one of their European outliers, ivy is pretty weird by Araliaceae standards. Pseudopanax species are perhaps a bit more typical. They have large leaves, often more or less toothed or lobed along the margins. In a number of species, the leaves are palmately divided into three or five separate leaflets, hence the aforementioned vernacular name of 'five-finger'. In one group of species, the lancewoods, the lateral leaflets have been lost and the now undivided leaf is more or less long and narrow. Hybrids between five-fingers and lancewoods may have multiple leaflets like a five-finger but the leaflets shaped like those of a lancewood; New Zealand botanist Leon Perrie has written a post about hybridisation in this genus that you can read here. The trees are usually dioecious (male and female flowers are borne on separate trees) and the individually small flowers are borne aggregated in compound umbels. Fruits are fleshy berries.

Collection of lancewoods P. crassifolius showing the variation in leaf form, copyright Petra Gloyn. Two individuals on the left are young tress with hanging leaves; to the right is a more mature individual with spreading leaves.

Within Pseudopanax, the lancewoods are particularly renowned for their exhibition of heteroblasty, a phenomenon where the appearance of the leaves changes significantly as the tree matures. Juvenile leaves of the common lancewood P. crassifolius and toothed lancewood P. ferox are remarkably long, slender, strongly toothed along the margin, stiff and leathery, and hang downwards around the young tree like a skirt. As the tree approaches its mature height, it starts producing shorter, softer, less serrate leaves that are held in a more or less horizontal position.

Changes in growth habit with maturity seem to be surprisingly common among New Zealand plants and there has been a lot of discussion about why this might be. One suggestion that has certainly received a lot of public attention is that it is a relic of browsing by the large herbivorous birds such as moa that dominated the New Zealand environment prior to human settlement. Juvenile plants developed a habit that was energetically expensive but discouraged browsing by birds; as they grew high enough to escape the reach of such browsers, they changed to a less demanding form. I personally tend to be skeptical of these kinds of claims of historical baggage, not least because the extinction of one-half of the equation makes them very hard to test in any way, but I will admit that this case does perhaps have a bit more credibility than, for instance, claims elsewhere of giant fruits being dependent on long-extinct megafauna. Alternatively, it has been suggested that changes in growth habit may be related to climatic conditions; the juvenile leaves of P. crassifolius dissipate heat more effectively than those of mature trees (Gould 1993). Heteroblasty is less pronounced in the montane lancewood P. linearis of the South Island and almost absent in the Chatham Islands lancewood P. chathamicus, an insular derivative of P. crassifolius. Were these species insulated from the selective pressures affecting the other two? It should also be pointed out that the two proposals mentioned here are not mutually exclusive; the consideration of one as a factor does not automatically rule out the other.

REFERENCES

Gould, K. S. 1993. Leaf heteroblasty in Pseudopanax crassifolius: functional significance of leaf morphology and anatomy. Annals of Botany 71: 61–70.

Mitchell, A. D., D. G. Frodin & M. J. Heads. 1997. Reinstatement of Raukaua, a genus of the Araliaceae centred in New Zealand. New Zealand Journal of Botany 35 (3): 309–315.

Perrie, L. R., & L. D. Shepherd. 2009. Reconstructing the species phylogeny of Pseudopanax (Araliaceae), a genus of hybridising trees. Molecular Phylogenetics and Evolution 52: 774–783.

The Coutoubeines

Members of the family Gentianaceae, the gentians, are for the greater part associated with cooler climes. Residents of areas subject to heavy snowfalls have often commented on the appearance of their showy flowers with warming weather in the spring. But not all subgroups of the gentians are so temperate: some, such as the Coutoubeinae, are inhabitants of the tropics.

Schultesia guianensis, copyright João de Deus Medeiros.

The Coutoubeinae are a group of about thirty known species divided between five genera found in Central and South America (Struwe et al. 2002). A single species, Schultesia stenophylla, is found in western Africa but, as it is also found in Brazil alongside related species, it can be reasonably presumed to be a recent immigrant to that region. Like most other members of the Gentianaceae, species of the Coutoubeinae are low herbs, often found growing in open habitats. With the exception of the genus Deianira, most lack a basal rosette of leaves. Flowers are usually white or pink, and are quadrimerous (with four corolla lobes) in the majority of species (one species, Schultesia pachyphylla, has blue pentamerous flowers; Guimarães et al. 2013). Perhaps the most characteristic feature of the group is that pollen is released in tetrads (clumps of four). I haven't come across any specific comments on the functional significance (if any) of this feature in coutoubeines but it has been suggested that pollen clumping in plants may correlate with visits from pollinators being relatively uncommon (and getting a decent amount of pollen transported at a time becomes more important than increasing the chance of pollen being transported to multiple targets).

Coutoubea spicata, copyright Alex Popovkin.

The largest genus of coutoubeines is Schultesia, including about twenty species. Schultesia species are annual herbs with long-lanceolate leaves and tube-shaped, usually pink (occasionally yellow or blue) flowers with the calyx tube at least as long as the lanceolate corolla lobes. The species Xestaea lisianthoides, sometimes included in Schultesia, differs from Schultesia in the arrangement of stamens (inserted unevenly in the corolla rather than in the upper part of the tube) and the shape of the stigmatic lobes (oblong rather than rounded). Coutoubea species have white, salver-shaped flowers with triangular corolla lobes. Symphyllophyton caprifolium, a rare species restricted to southern Brazil, is a short-lived perennial with perfoliate leaves and yellow to cream salver-shaped flowers with the calyx tube shorter than the corolla lobes. Finally, Deianira includes suffrutescent herbs with a basal rosette of leaves and salver-shaped flowers with a short calyx tube.

REFERENCES

Guimarães, E. F., V. C. Dalvi & A. A. Azevedo. 2013. Morphoanatomy of Schultesia pachyphylla (Gentianaceae): a discordant pattern in the genus. Botany 91: 830–839.

Struwe, L., J. W. Kadereit, J. Klackenberg, S. Nilsson, M. Thiv, K. B. von Hagen & V. A. Albert. 2002. Systematics, character evolution, and biogeography of Gentianaceae, including a new tribal and subtribal classification. In: Struwe, L., & V. A. Albert (eds) Gentianaceae: Systematics and Natural History pp. 21–309. Cambridge University Press: Cambridge.

Goldenrod

Growing up as a child in rural New Zealand, I remember the community social events that would sometimes be held at the local district hall. On one evening, if I recall correctly, the event being held was a quiz night modelled after then-popular game show It's in the Bag. For those unfamiliar with this long-running institution, contestants on the show who successfully answered a series of general knowledge questions asked by Selwyn Toogood, a large avuncular man with an appropriately fruity voice, would be offered the choice between a cash prize up front or a 'bag' containing an unknown prize. This prize could potentially be something worth a lot more than the money on offer, such as a trip away or a home appliance (game shows in the 1980s often included whiteware among their top tier prizes). On the other hand, it could be worth a lot less, potentially even being effectively worthless (as viewers at home, of course, we always hoped for the latter). On this occasion, one of the 'prizes' on offer was a packet of seeds from 'the pretty yellow flowers that grow so vigorously in the region'. Everyone in the audience would instantly recognise the flowers in question as ragwort Senecio jacobaea, a pernicious weed much maligned due to its toxicity to livestock. Ragwort probably arrived in New Zealand as a contaminant in grass seed, but for today's post, I'm looking at another member of the daisy family which became a weed after being more deliberately spread around.

Tall goldenrod Solidago gigantea, copyright Pethan.

Solidago, the goldenrods, is a genus of perennial herbs with a woody caudex or rhizome and usually bright yellow flowers. About 100 to 120 species are currently recognised in the genus, the great majority of which are native to North America. Other species are found in South America and Eurasia, and a number of the North American species have been spread around the world by human activity. The number of species to be recognised is somewhat disputed because, as with many decent-sized plant genera, goldenrods have a tendency to laugh in the face in clear species concepts. Differences between species can be difficult to observe and hybrids are not uncommon. Individuals belonging to the same species may vary notably with geography and growth conditions and determining whether variation is genetic or environmental has historically required extensive growth experiments cultivating seed collections at varying locations. Vegetative spreading through rhizomes may lead to isolated populations of near-clonal individuals that may come to be recognised as 'microspecies'. As a result, what one author may recognise as a number of distinct species may be treated by another author as variants of a single species. For example, a study of altitudinal variants of the European S. virgaurea in Poland by Kiełtyk & Mirek (2014) lead them to recognise two species that had previously been confused, the lowland S. virgaurea and the montane S. minuta. The two were best distinguished by relatively fine-scale features of the flower heads, most notably the number of tubular florets in each head.

Canada goldenrod Solidago canadensis, copyright Olivier Pichard.

In a review of the North American Solidago species, Semple & Cook (2006) divided the genus between two sections. The smaller section Ptarmicoidei, including only half a dozen species, is characterised by clustering of flower heads in flat-topped arrays. The remaining species in the much larger section Solidago may have heads in rounded, conical or club-shaped arrays, or bear flower heads in axillary clusters. The distinctiveness of section Ptarmicoidei is enough that some authors have placed it as a separate genus Oligoneuron. Research is ongoing concerning the phylogeny of Solidago and its precise relationships with related genera.

Historically, the European Solidago virgaurea was valued for its supposed medicinal qualities (hence the genus name, which can be translated as 'becoming whole'). But while the dried flowers may still be used in making herbal tea, goldenrod does not seem to be currently regarded as of much pharmaceutical significance. As long ago as 1597, John Gerard noted in his Herball that the once highly prized herb had plummeted in value and regard once it was found to be growing wild in England, making it a mere local weed instead of an exotic import*. In the 1920s, Thomas Edison experimented with using goldenrod as a source of rubber. Investigations in this line were later continued in the 1940s by agrarian scientist George Washington Carver (under the patronage of Henry Ford), partially to counter rubber shortages during World War II. However, rubber yield from goldenrod is low and the rubber produced of low quality, so it never became a commercially significant source.

*'...in my remembrance, I haue known the dried herbe which came from beyond the ſea ſold in Bucklersbury in London for halfe a crowne an ounce. But ſince it was found in Hampſtead wood, euen as it were at our townes end, no man will giue halfe a crowne for an hundred weight of it: which plainely ſetteth forth our inconſtancie and ſudden mutabilitie, eſteeming no longer of any thing, how pretious ſoeuer it be, than whileſt it is ſtrange and rare. This verifieth our Engliſh proverbe, Far fetcht and deare bought is beſt for Ladies.'

Woundwort Solidago virgaurea var. leiocarpa, copyright Alpsdrake.

As alluded to above, a number of North American goldenrod species have been carried to temperate regions around the world as ornamentals or to provide nectar for bees. Unfortunately, some of these species have become significant invasive weeds in their adopted homes. Canada goldenrod Solidago canadensis can have an allelopathic effect on surrounding vegetation, producing water-soluble compounds that may inhibit the germination and growth of seeds (Werner et al. 1980). It may also act as a reservoir for pathogens of crop plants. Goldenrod is also commonly accused of causing hay fever but, in this regard at least, it seems to be largely innocent. Goldenrod plants shed relatively little pollen; as the flowers are insect-pollinated, the pollen is relatively unlikely to enter the air column. Instead, it seems that the conspicuous goldenrod flowers are blamed for the more copious pollen shed by less visible plants such as ragweeds flowering at the same time.

REFERENCES

Kiełtyk, P., & Z. Mirek. 2014. Taxonomy of the Solidago virgaurea group (Asteraceae) in Poland, with special reference to variability along an altitudinal gradient. Folia Geobotanica 49: 259–282.

Semple, J. C., & R. E. Cook. 2006. Solidago Linnaeus. In: Flora of North America Editorial Committee (eds) Flora of North America vol. 20. Asteraceae, part 2. Astereae and Senecioneae pp. 107–166. Oxford University Press: New York.

Werner, P. A., I. K. Bradbury & R. S. Gross. 1980. The biology of Canadian weeds. 45. Solidago canadensis L. Canadian Journal of Plant Science 60: 1393–1409.

Canterbury Bells

Bellflowers or harebells are one of the classic plants associated with the English country garden. For today's post, I'll be covering the family of plants that bellflowers belong to.

Fairy's thimble Campanula cochleariifolia, copyright Jerzy Opioła.

The Campanulaceae are a family of over 2300 plant species found almost worldwide (Crowl et al. 2016). The family is, however, divided between five subfamilies that some authors would treat as separate families, in which case 'Campanulaceae' would be restricted to the 600 or so species of the subfamily Campanuloideae. It is this subfamily that includes the bellflowers. The vernacular name, of course, refers to the shape of the flowers produced by these plants, as indeed does the botanical name: Campanula translates as 'little bell'. These flowers are radiately symmetrical with all petals more or less the same size and shape and evenly arranged in a circle. Other subfamilies of the Campanulaceae in the broad sense, the largest of which is the lobelias of the Lobelioideae, produce more bilaterally symmetrical flowers with petals differing in size and/or with some petals closer together than others. Fruits are most commonly a capsule, with the seeds dispersed by wind, but some lobelioids produce fleshy fruits that attract birds. The lobelioids are most diverse in the southern continents, and it is thought that this may have been the original home of the family as a whole when it arose sometime close to the end of the Cretaceous, possibly in Africa. At some time in the early Cenozoic, however, the campanuloids arrived in and underwent a significant radiation in the Palaearctic. This dispersal may be related to the different flower morphology of the campanuloids, as they adapted from the bird, bat and butterfly pollinators of the tropics to the bee and fly pollinators of more temperate habitats.

Glandular threadplant Nemacladus glanduliferus var. orientalis, copyright Stan Shebs.

The genetics of Campanulaceae, specifically of their chloroplasts, should also not go unnoticed. The structure of the chloroplast genome in plants is usually very stable, with few changes in gene arrangement and order. However, at various points in the history of Campunulaceae, large chunks of foreign DNA have been inserted in the original plastid chromosome, with a number of these insertions also associated with inversions in the direction of adjoining sections of the original genes (Knox 2014). This kind of insertion is unique among flowering plants: changes in the gene content of plastids more usually involve genes being transferred out of the plastid. The source of this extra DNA is uncertain: it may have come from the plant's own nucleus, or it may have come from an as-yet-unknown endosymbiont. Also unknown is the functional significance of these rearrangements, if any. Some insertions have clearly resulted in pseudogenes, with their sequences rapidly breaking down through subsequent genetic drift. But others have preserved the structure of functional genes, suggesting continued selection for their retention.

Cyanea duvalliorum, an arborescent Hawaiian lobeliad, copyright Forest & Kim Starr.

The majority of Campanulaceae are small perennial herbs. Two genera of distinctive enough to be assigned to their own subfamilies include annual herbs: the threadplants Nemacladus of southwestern North America, and the little-known Chilean Atacama desert endemic Cyphocarpus. Some members of the Lobelioideae are woody subshrubs, and at some point one of these woody lobelioids managed to make its way to the Hawaiian archipelago where it gave rise to one of the world's most remarkable insular radiations, and the single largest such radiation in plants. Over 120 species of lobeliads are known from the Hawaiian islands, varying from single-stemmed succulents to straggling vines to trees over 18 metres in height. There are inhabitants of lowland forests, of upland bogs, and of rocky cliffs. There are species producing fruit as dry capsules; others produce fleshy berries. So varied are the Hawaiian lobeliads that previous authors have inferred their origin from multiple seperate colonisations, but a study by Givnish et al. (2009) supported a single origin from a single colonist arriving about thirteen million years ago. This would have been before any of the current major Hawaiian islands existed (the oldest, Kaua'i, is a little less than five million years old); the implication is that the ancestor of the Hawaiian lobeliad arrived on a pre-existing island, perhaps corresponding to the modern Gardner Pinnacles or French Frigate Shoals. As the lobeliads diversified, they continued to disperse onto new islands as they arrived, while their original homeland eroded away.

Sadly, a depressing percentage of the species forming this incredible radiation are now threatened with extinction, the victims of pressures such as loss of habitat, the decline of their pollinators and dispersers, or grazing by introduced mammals. The cliff-dwelling pua 'ala Brighamia rockii of Moloka'i is now restricted to five locations with an estimated total wild population of less than 200 individuals. A related species on Kaua'i, the olulu Brighamia insignis, may be extinct in the wild, having last been recorded in the form of a single individual in 2014 (it still survives in cultivation). As we earlier saw with the Hawaiian honeycreepers, there is barely a single section of the Hawaiian biota not marked by tragedy.

REFERENCES

Crowl, A. A., N. W. Miles, C. J. Visger, K. Hansen, T. Ayers, R. Haberle & N. Cellinese. 2016. A global perspective on Campanulaceae: biogeographic, genomic, and floral evolution. American Journal of Botany 103 (2): 233–245.

Givnish, T. J., K. C. Millam, A. R. Mast, T. B. Paterson, T. J. Theim, A. L. Hipp, J. M. Henss, J. F. Smith, K. R. Wood & K. J. Sytsma. 2009. Origin, adaptive radiation and diversification of the Hawaiian lobeliads (Asterales: Campanulaceae). Proceedings of the Royal Society of London Series B—Biological Sciences 276: 407–416.

Knox, E. B. 2014. The dynamic history of plastid genomes in the Campanulaceae sensu lato is unique among angiosperms. Proceedings of the National Academy of Sciences of the USA 111 (30): 11097–11102.

Of Shrimp Plants and Bear's Breeches

For today's semi-random post, I drew the plant subfamily Acanthoideae. As recognised by Scotland & Vollesen (2000), the Acanthoideae is the largest of the subfamilies of the Acanthaceae by a considerable margin, including about 95% of the family's 2500+ species. Though perhaps not hugely familiar to readers in more temperate climes, the Acanthoideae are one of the dominant groups of herbs and shrubs in tropical parts of the world.

Golden shrimp plant Pachystachys lutea, copyright Dryas.

The Acanthoideae have been recognised as a morphological group since the late 1800s and their integrity has been confirmed by more recent molecular studies. They are distinguished from related plants (within the Lamiales, the order that also includes such plants as the mints and snapdragons) by having capsular fruits that dehisce explosively when mature to scatter their seeds. The seeds are attached within the capsule by hook-shaped stalks called retinacula that presumably play a role in determining how the seeds are released. A classification of Acanthaceae published in 1965 by Bremekamp restricted the family to species with explosive fruits and retinacula, dividing them between two subfamilies, the Acanthoideae and Ruellioideae, based on the absence or presence, respectively, of cystoliths. These are outgrowths of the epidermal cell walls that are impregnated with calcium carbonate. They are visible in the stems and leaves, at least in dried specimens, as hard white streaks. As phylogenetic studies have supported division of Acanthoideae in the broad sense between a cystolith-possessing and a cystolith-lacking clade, the decision whether to recognise 'Ruellioideae' as a separate subfamily comes down to a ranking choice only. At lower levels, the classification of Acanthoideae is less straightforward. Over two hundred genera of Acanthoideae are recognised but just three of those—Justicia, Strobilanthes and Ruellia—account for about half the total number of species. Each of these mega-genera is morphologically diverse and likely to be para- or polyphyletic with regard to related taxa, raising the distinct likelihood of future revisions.

Spiny bear's breeches Acanthus spinosus, copyright Magnus Manske.
Economically, few of the Acanthoideae are of great significance except for a number of species being grown ornamentally. One such species is Acanthus mollis, which goes by the vernacular name of 'bear's breeches' (why, I have absolutely no idea). Acanthus was a popular decorative motif in classical Greece and forms the basis for the design of Corinthian columns. Its use as an ornamental has lead to it becoming regarded as an invasive weed in some regions, largely because this is one of those garden plants that Just Will Not Die, spreading easily from seeds and tubers. We've got some in a pot outside that is currently flourishing despite having been burnt down to a nub by the searing Perth summer sun, metaphorically shouting its defiance at an uncaring world.

REFERENCE

Scotland, R. W., & K. Vollesen. 2000. Classification of Acanthaceae. Kew Bulletin 55 (3): 513–589.

Sorting Monkeys: Dissecting Mimulus

New Zealand musk Thyridia repens, one of the species previously included in Mimulus section Paradanthus, copyright Jon Sullivan.

Long-time readers of this site will know that often, when I pull out the name from the virtual hat of my subject taxon for the week, I find that the greatest challenge lies in determining just what that name applies to. I knew that I was in for another one of these challenges as soon as I established that this week's post would be on the section Paradanthus of the plant genus Mimulus.

Mimulus, as it is most commonly recognised, is a genus of about 120 species found in many parts of the world but with by far the greatest diversity in western North America (where about three-quarters of the recognised species are found). They are commonly known as monkeyflowers or muskflowers in reference to the appearance and scent of the flowers of some species. Because of their diversity (in a well-studied part of the world), monkeyflowers have attracted a fair bit of interest as a model system for studying processes of evolution and speciation. Most Mimulus species are herbs though some are small shrubs. However, even shrubby forms do not have extensive root systems, and they are mostly annual or seasonal; perennial forms usually die off above ground over winter, growing back from the rootstock when conditions improve. These perennial forms may also propagate vegetatively through drooping stems putting down new rootstock where they contact the ground (Grant 1924). Mimulus species primarily grow in damp habitats; some will even grow in standing water.

Nepal monkeyflower Erythranthe nepalensis, copyright Qwert1234.

Until fairly recently, Mimulus was primarily classified in the family Scrophulariaceae. Members of this family (including Mimulus) were united by the possession of a flower type referred to as a 'scroph'; examples of plants with scroph flowers that may be familiar to you include snapdragons or foxgloves. Characteristic features of a scroph include having the calyx and corolla each fused basally. The corolla is hence more-or-less tubular at the base, then divided towards the top into five out-turned lobes corresponding to the petals (usually with two above and three below; the flower is therefore zygomorphic or bilaterally symmetrical). This flower type is primarily adapted to pollination by insects such as bees that use the lower lobe (or lip) as a 'landing ramp' when visiting the flower. After pollination, the flower develops into a dehiscent, many-seeded capsule. The advent of molecular phylogenetic analysis has established, however, that scroph-flowered plants belong to several lineages within the order Lamiales; the scroph has apparently evolved (and been lost) on a number of occasions. As a result, Mimulus is now placed in a separate family Phrymaceae with a handful of small, closely related genera.

Muskflower Erythranthe moschata, copyright Nick Moyes.

Mimulus was divided into two subgenera and ten sections by Grant (1924); with minor modifications, her system remained in place until recently. The two subgenera, Synplacus (or Mimulus proper) and Schizoplacus, were recognised based on whether the flower's placenta was united or divided, respectively. Four of Grant's sections were placed in the subgenus Mimulus; one of these was Paradanthus. Grant's system was not entirely phylogenetic as we would understand the term today: she did provide a diagram of suggested relationships between the sections but it did not cleanly separate the two subgenera. The section Paradanthus, in particular, was explicitly established as a convenient holding-place for a number of "small closely allied associations which, however, were not sufficiently distinct to warrant being placed in sections by themselves". Most had relatively unspecialised flowers, mostly (but not always) with funnel-shaped corollas and more or less equal lobes. Grant also somewhat unceremoniously dumped the majority of non-American Mimulus species into Paradanthus. She confessed that this section was "a collection of groups not necessarily related to one another and in all probability most of them have been derived from members of the other sections".

Phak taptao Mimulus orbicularis, one of the few true Mimulus species under the system of Barker et al. (2012), from here.

It therefore came as no surprise whatsoever when later phylogenetic analyses did not uphold the section Paradanthus as monophyletic. Instead, the primary division within Mimulus found by Beardsley & Olmstead (2002) was between a clade centred on western North America and one containing the majority of species from elsewhere in the world, with the Paradanthus species falling in either clade depending on their distribution (many of Grant's other sections, in contrast, do correspond to monophyletic groups). Perhaps more unexpected was the finding that Mimulus as a whole was not monophyletic. Instead, other genera of Phrymaceae were nested in Mimulus, including Phryma, a genus of one or two species found in eastern North America and eastern Asia in which the fruit is a single-seeded achene instead of a multi-seeded capsule, and Leucocarpus, a Central American genus in which the fruit is a fleshy berry.

The non-monophyly of Mimulus raised the question of whether these other genera should be subsumed within a broadened Mimulus (in which case the genus Mimulus and the family Phrymaceae would potentially become identical in content). An alternative tack was proposed by Barker et al. (2012) who divided the 'traditional' Mimulus into several genera corresponding to monophyletic clades separated by the previously recognised segregate genera. Of the 120 or so original species, only seven remain in the restricted Mimulus (species of Grant's section Paradanthus end up divided between no less than four genera). None of the western North American species remain in Mimulus; instead, species from this region are divided between the genera Diplacus and Erythranthe.

Only time will tell whether this proposed reorganisation will gain acceptance. I can see there being a lot of resistance to the idea that many of the most familiar 'Mimulus' species should no longer be included in Mimulus, particularly in non-academic circles. Nobody likes being made a monkey by monkeyflowers.

REFERENCES

Barker, W. R., G. L. Nesom, P. M. Beardsley & N. S. Fraga. 2012. A taxonomic conspectus of Phrymaceae: a narrowed circumscription for Mimulus, new and resurrected genera, and new names and combinations. Phytoneuron 2012-39: 1–60.

Beardsley, P. M., & R. G. Olmstead. 2002. Redefining Phrymaceae: the placement of Mimulus, tribe Mimuleae, and Phryma. American Journal of Botany 89 (7): 1093–1102.

Grant, A. L. 1924. A monograph of the genus Mimulus. Annals of the Missouri Botanical Garden 11 (2–3): 99–388.

Mintbush Genus Limits

Victorian Christmas bush Prostanthera lasianthos, copyright Melburnian.

Despite (or perhaps because of) the severity of Australia's climate over much of the continent, the country has become famed for its wildflower displays. At the right time of year, the otherwise bleak landscape becomes a riot of form and colour. The display shown above belongs to a species of the genus Prostanthera, an assemblage of about 100 species of bushy shrubs (very rarely small trees) known as mintbushes, endemic to yet ubiquitous around Australia (new species continue to be described at fairly regular intervals). As suggested by their vernacular name, mintbushes belong to the mint family Lamiaceae, the same family as many well-known garden herbs such as sage, rosemary or thyme. Like these relatives, mintbushes have strongly aromatic foliage, due to the presence of glands secreting volatile oils on the leaves. However, the edibility of most species is unknown; I did find a couple of references to culinary uses of the round-leaved mintbush Prostanthera rotundifolia though it is not common (and a couple of comments in this thread suggest that it may be a bit pungent for regular use). Certainly, to push the pun in this post's title far further than it deserves, there is no evidence of mintbush gin.

Prostanthera species are most readily recognised by their flowers (Wilson et al. 2012). The calyx at the base of the flower has the sepals fused so that it is shaped as two lips, an upper and a lower. The corolla of petals has five lobes, two in the upper lip and three in the lower. There are four anthers, which often (though not always) have a distinct basal appendage; it is this appendage that gives the genus its name (from the same Greek word that gives us the term 'prosthetic'). Different species have flowers in a wide range of colours, and many Prostanthera species have become popular ornamentals.

Flower of scarlet mintbush Prostanthera aspalathoides, copyright Patrick Kavanagh.

Prostanthera is a member of a tribe of Australian Lamiaceae known as the Westringieae, members of which have a dry fruit splitting into four sections (Conn 1984). The two-lobed calyx of Prostanthera separates it from most other genera that have been recognised in the Westringieae except for a small genus called Wrixonia. The only significant difference between Wrixonia and Prostanthera is that whereas the latter retains four fertile anthers, the former has one pair of anthers sterile and reduced. A molecular phylogenetic analysis by Wilson et al. (2012) found that Wrixonia species were nested within Prostanthera, raising doubt about whether Wrixonia should be recognised as a separate genus. Also of interest was the relationship between the two sections into which Prostanthera has been divided: section Prostanthera and section Klanderia. These sections differ in characteristics of their flowers. Prostanthera section Prostanthera has flowers that are white, mauve or blue, with a corolla in which the central lower lobe is longer than the others so the overall appearance is similar to an orchid (such as in the P. lasianthos at the top of this post). In section Klanderia, the flowers are green, yellow or red, and the two upper lobes of the corolla are the longest so the appearance of the flower is more tubular (such as in the P. aspalathoides just above). Some authors have regarded the difference between two sections as enough to warrant recognised section Klanderia as a separate genus (in which case it becomes known as Cryphia, because botanical nomenclature is complicated like that). The two sections differ in flower morphology because they differ in pollinator type: flowers of section Prostanthera are pollinated by insects, whereas flowers of section Klanderia are pollinated by birds. Again, Wilson et al. (2012) found that the larger section Prostanthera, which retains the ancestral pollinator type, is paraphyletic with regard to the derived section Klanderia.

REFERENCES

Conn, B. J. 1984. A taxonomic revision of Prostanthera Labill. section Klanderia (F.v.Muell) Benth. (Labiatae). J. Adelaide Bot. Gard. 6 (3): 207–348.

Wilson, T. C., B. J. Conn & M. J. Henwood. 2012. Molecular phylogeny and systematics of Prostanthera (Lamiaceae). Australian Systematic Botany 25: 341–352.

Stars and Blessings

Yellow starthistle Centaurea solstitialis, copyright Franco Folini.

The first thing that struck me when I was looking up material on Centaurea was how evocative some of the vernacular names associated with this genus are: starthistle, blessed thistle, dusty miller, sweet sultan. Centaurea, the starthistles and knapweeds, is a genus of composite-flowered plants native to Eurasia and northern Africa, with the highest diversity of species in the Mediterranean region. A handful of species have been spread to other parts of the world in association with humans; a handful of these are significant pasture pests such as spotted knapweed C. maculosa and yellow starthistle C. solstitialis, whereas others such as dusty miller C. cineraria are grown as garden plants. Centaurea is a large genus: depending on how you count them, it may contain anywhere between 300 and 700 species. The greater number of species are perennial herbs, but the genus varies from small spiny shrubs to low spreading annuals (Wagenitz 1986). Some arise from a single central tap-root; others grow from spreading rhizomes. Some species have spiny leaves and conform to our general idea of a 'thistle'; others do not. The leaves are often deeply divided at the base of the plant, becoming entire towards the top. Flowerheads may be borne singly or in a corymbiform arrangement (a flat-topped cluster); the phyllaries (the bracts surrounding the flowerhead) often extend outwards around the head, and may be themselves tipped with spines.

Squarrose knapweed Centaurea triumfettii, copyright Kristian Peters.

With a genus of this size, it should be hardly surprising that taxonomic complications are involved. Long recognised as morphologically diverse, it has been confirmed as polyphyletic by more recent molecular analyses (Garcia-Jacas et al. 2001). The majority of Centaurea species fall within a single derived clade within the composite subtribe Centaureinae, united both by molecular data and by a number of morphological synapomorphies including adaptations for myrmecochory, dispersal of the seeds by ants (the seeds carry an attached oily body called an elaiosome; ants carry the seeds back to their nest where they may eat the elaiosome but leave the seed to sprout). A handful of species, though, lack these synapomorphies and lie in scattered segregate clades among the remainder of the Centaureinae. Some of these segregate clades, such as the former section Psephellus, have been straightforwardly promoted to the status of separate genera. One small segregate clade, however, is a little more problematic because it happens to include the north African Centaurea centaurium, the original type species of the genus Centaurea. Under normal circumstances, then (other than lumping the entirety of centaureines in a single genus), the name Centaurea would apply only to this small clade (including only about a dozen species) while the hundreds of species in the main 'Centaurea' clade would have to be renamed. In this case, the name with priority for this large clade would be Cnicus, generally used to date for only a single species, the blessed thistle Cnicus benedictus (no, I haven't been able to establish why it is called the 'blessed thistle'; I have found references to a tradition of medicinal use for this species, including its supposedly encouraging milk production in nursing mothers, but I haven't been able to confirm if this is the reason for the name). In order to stave off this nomenclatural turmoil, it has been proposed that the official type species of Centaurea be changed to a member of the main clade (Greuter et al. 2001), so this clade keeps the name Centaurea (and the blessed thistle becomes referred to as Centaurea benedicta) whereas the small clade including the prior type species becomes known as the genus Rhaponticoides. I haven't found whether a final decision has been made on this proposal (the process for such nomenclatural decisions is a bit more involved for plants than animals, requiring an open vote at an international botanical conference rather than just being decided on directly by a select committee) but it seems to have general support. Less certain is the status of the cornflowers of the section Cyanus, which some have proposed recognising as a separate genus but which is closely related to the main clade, making the case for its separation a bit less compelling.

REFERENCES

Garcia-Jacas, N., A. Susanna, T. Garnatje & R. Vilatersana. 2001. Generic delimitation and phylogeny of the subtribe Centaureinae (Asteraceae): a combined nuclear and chloroplast DNA analysis. Annals of Botany 87: 503–515.

Greuter, W., G. Wagenitz, M. Agababian & F. H. Hellwig. 2001. (1509) Proposal to conserve the name Centaurea (Compositae) with a conserved type. Taxon 50: 1201–1205.

Wagenitz, G. 1986. Centaurea in south-west Asia: patterns of distribution and diversity. Proceedings of the Royal Society of Edinburgh, Section B, Biological Sciences 89: 11–21.

Teasels and Scabious: the Dipsacaceae

Scabiosa cretica, copyright Ori Fragman Sapir.

As recognised plant families go, the Dipsacaceae is not a particularly large one. It includes only a few hundred species, of which the majority are found in arid regions around the Mediterranean and the remainder elsewhere in Africa and Eurasia. The economic significance of the family is also relatively low. Some species are cultivated as ornamental plants. Dipsacus fullonum, teasel, gets its vernacular name because its bottle-brush-like flower-heads were used to tease the fibres of woollen cloth. Various species of Dipsacaceae, particularly the genus Scabiosa, are known as 'scabious' because they were apparently once used somehow in treating scabies. I also came across a reference in Duke (2008) to Syrian scabious Cephalaria syriaca having had a certain notoriety in the past due to its seeds being similar in appearance to wheat grain, meaning that they could be inadvertently sown into fields, or impart an unpleasant taste if ground into flour.

Flowers and fruits of Sixalix atropurpurea, copyright Manuel M. Ramos. Members of this genus grow on sand; their fruits have a reduced membranous wing, and disperse by rolling.

Nevertheless, the Dipsacaceae are not without their points of interest. One intriguing characteristic of the family is that they bear numerous small flowers clustered onto a single shared receptacle, similar to those of the much more diverse Asteraceae. Like Asteraceae, there may even be a differentiation in the appearance of flowers on the inner part of the receptacle from those around the outer rim. The Dipsacaceae are not directly related to the Asteraceae; rather, the two families have developed their capitate flower-heads independently. Which is not to say that they are incomparable: species of both Asteraceae and Dipsacaceae exhibit duplications of genes that are believed to affect the development of floral symmetry (Carlson et al. 2011), and it is possible that similar processes have lead to the evolution of compound flower-heads in both.

Flowers and fruits of Scabiosa sicula, copyright Jose Rodriguez. The fruiting head in focus shows the membranous wings that function in dispersal.

Past authors have divided the Dipsacaceae into three tribes, largely on the basis of characters related to seed dispersal. Each of the small flowers on a dipsacacean flower-head develops into a dry fruit containing a single seed. The epicalyx (an outer protective layer of the flower base) persists as an outer coating of the mature fruit, like a second skin. In the largest of the three previously recognised tribes, the Scabioseae, the epicalyx is often modified for wind dispersal, either by plumose hairs on top of a dorsal tube (the same sort of set-up as seen in dandelions) or by a membranous wing around the fruit. In contrast, the fruit of the genus Knautia, widow flowers, which has been placed in its own separate tribe, bears an elaiosome, a fleshy, hemispherical lump. The elaiosome attracts ants, who carry the fruit away to their nest; after the ants have eaten the elaiosome, the remaining seed is able to germinate where they leave it. Finally, the third tribe Dipsacaceae includes only the genera Dipsacus and Cephalaria; the mature fruit of these genera lack adaptations for either wind or ant dispersal, and seed dispersal is largely controlled by the break-up of the flower-head itself.

Bassecoia bretschneideri, copyright Dave Boufford.

More recent molecular analyses, however, have not entirely supported this three-way division of the Dipsacaceae (Carlson et al. 2009). While Knautia and the Dipsaceae are both likely to be monophyletic, the Scabioseae are not. Instead, a small clade including the eastern Asian genus Bassecoia is sister to the remaining members of the family. These fall into two major clades: one, that has been referred to as the Scabioseae 'sensu stricto', includes the majority of the taxa previously included in the Scabioseae, such as Scabiosa, Lomelosia and Pterocephalus. The other clade, which has been dubbed the 'dipknautids', includes Knautia and the Dipsaceae, together with a few smaller 'ex-Scabioseae' genera. While the original Dipsacaceae may have been wind-dispersed, they have not been above looking at alternatives.

REFERENCES

Carlson, S. E., D. G. Howarth & M. J. Donoghue. 2011. Diversification of CYCLOIDEA-like genes in Dipsacaceae (Dipsacales): implications for the evolution of capitulum inflorescences. BMC Evolutionary Biology 11: 325. doi:10.1186/1471-2148-11-325.

Carlson, S. E., V. Mayer & M. J. Donoghue. 2009. Phylogenetic relationships, taxonomy, and morphological evolution in Dipsacaceae (Dipsacales) inferred by DNA sequence data. Taxon 58 (4): 1075-1091.

Duke, J. A. 2008. Duke's Handbook of the Medicinal Herbs of the Bible. CRC Press.

What is Inula verbascifolia?

By recommendation of the Committee for Spermatophyta (Brummitt 2005), this is. Photograph by L.R.

Inula verbascifolia is a herbaceous, composite-flowered plant from the eastern Mediterranean. It is mostly found in the Balkan region, but it also reaches into south-eastern Italy and Anatolia. It is closely related to another Greek species, I. candida, and the two have been treated as a single species, but they can be distinguished by features of the leaves (Tan et al. 2003).

The reason for my question, though, is that Inula verbascifolia has been the subject of an application to have its name conserved (Tan et al. 2003). The rules for naming organisms are often assumed to be complicated, and to a certain extent they are, but the underlying principles can be summed up into two rules: (1) every species should have one name that is different from all other species, and (2) when two names are in conflict, the older name is the correct one. However, like all rules of life, sometimes the best thing to do is not follow the rules. Maybe using the older name would be too confusing, if the newer name is much the better known. To account for such scenarios, all of the various bodies governing the naming of organisms (there are separate bodies for animals, plants and bacteria) make allowances for researchers on the organisms concerned to apply for the rules to be temporarily set aside in some way.

In the case of Inula verbascifolia, the plant currently known by that name was not the first to be called that. The German botanist Heinrich Haussknecht recognised the Balkan species as Inula verbascifolia in 1895. Prior to that, it gone under the name of Conyza verbascifolia, coined by Carl von Willdenow in 1803. However, in 1813 Jean Poiret of France had used the name I. verbascifolia for a plant growing the gardens of the Jardin des Plantes in Paris that had originally come from the Caucasus. 1813 beats 1895, so under strict application of the rules the name Inula verbascifolia should apply to the Caucasian plant, not the Balkan one. But the Caucasian plant had not been known by this name since 1819, whereas the Balkan plant was well-known by that moniker, so Tan et al. (2003) applied for the Balkan plant to be allowed to keep it.

I should point out that I'm an animal taxonomist by training, so I have only a basic awareness of the rules that apply to naming plants. One thing that interests me in this case is that things would have played out differently had the organisms in question been animals. The Zoological Code differs from the Botanical Code in that it doesn't regard the genus name as an integral part of the species name, so even if a species name is moved between genera, it still takes its priority from when it was first coined. In this case, for the Zoological Code the important date would not be 1895 when Haussknecht transferred verbascifolia to Inula, but 1803 when Willdenow called it verbascifolia in the first place. So under the Zoological Code, Willdenow's verbascifolia would be older than Poiret's verbascifolia, and there would be no need for the former to be specially upheld.

Another difference between the Zoological and Botanical Codes is in the process of deciding on applications. In the Zoological Code, an appointed body of taxonomists (the Commission) directly makes each decision themselves. In the Botanical Code, on the other hand, each application goes to a Committee (there are separate committees for seed plants, algae, fungi, etc.) who then vote on a recommendation whether or not to accept the application. The final decision is not made by the Committee, but is voted on by the attendees of the next International Botanical Congress, a conference that anyone is allowed to attend (if they're willing to pay the attendance fee, of course). In the case of Inula verbascifolia, the Committee on Spermatophyta recommended that the application be accepted (Brummitt 2005), but I don't know if it has been finally voted upon. I also don't know if Congress votes often go against Committee recommendations (I wouldn't expect them to, but passions can run high in the world of taxonomy).

Inula verbascifolia ssp. methanea, photographed by Giorgos Gioutlakis. (Update: Christine K. tells me that this photo has been misidentified. See her comment below.)

Tan et al.'s application had to save more than just the species name. Haussknecht's Inula verbascifolia shows enough variation over its range that it has been divided between five subspecies. The photograph at the top of this post, taken in Italy, shows the type subspecies I. verbascifolia ssp. verbascifolia. The photograph just above shows another subspecies from Greece. But when Tan et al. looked at the original specimens examined by Willdenow, they found that they did not belong to the subspecies that had since come to be known as the type. Therefore, they designated a new type specimen belonging to the recognised type subspecies: otherwise ssp. methanea might have had to be called ssp. verbascifolia, and ssp. verbascifolia would have had to be called something else. It is possible that Willdenow had himself seen a specimen of the type subspecies that has since been lost: according to Tan et al., he gave the distribution of Conyza verbascifolia as Sicily, Greece and Armenia. Tan et al. pointed out that Inula verbascifolia's distribution in Italy is in Gargano, not Sicily, so regarded Willdenow's record as an error. What they had evidently overlooked was that, in 1803, Gargano was still part of the Kingdom of Sicily.

And if you're still around after all of that, then you may find the newest cartoon from xkcd oddly apropos:

REFERENCES

Brummitt, R. K. 2005. Report of the Committee for Spermatophyta: 56. Taxon 54 (2): 527-536.

Tan, K., J. Suda & T. Raus. 2003. (1582) Proposal to conserve the name Inula verbascifolia (Willd.) Hausskn. against I. verbascifolia Poir. (Asteraceae) and with a conserved type. Taxon 52: 358-359.

Sending Forget-me-nots

The Chatham Islands forget-me-not Myosotidium hortensia, from here.

I haven't been able to prepare a full post lately as we're currently in the field conducting our next survey round for the day job. In the meantime, I'll just content myself with a brief introducion to the Cynoglosseae. This is a tribe in the plant family Boraginaceae, redefined by Långström & Chase (2002) on the basis of molecular phylogeny to effectively correspond to the clade of Boraginaceae with heterocolpate pollen, as well as an undivided style with a single stigma (another tribe of Boraginaceae, the Boragineae, was covered in an earlier post). In the heterocolpate pollen of Cynoglosseae, the three apertures found in the pollen of other Boraginaceae alternate with an equal number of 'pseudoapertures'. The pseudoapertures represent gaps in the outer exine coat of the pollen grain like the apertures, but lack certain other features of the latter such as a concentration of cytoplasmic vesicles, as well as being longer and narrower (Hargrove & Simpson 2003).

Flower of camelbush Trichodesma zeyanicum, photographed by Ethel Aardvark.

Perhaps the most familiar members of this usage of Cynoglosseae are the forget-me-nots of the genus Myosotis, with other members including the hound's-tongue Cynoglossum officinale and, here in Australia, the camelbush Trichodesma zeylanicum. Offhand, camelbushes are generally one of the more prominent flowering plants here on Barrow Island, my current location, though they're one a bit of a low right now. There has been a bit of rain, and camelbush doesn't like to get its feet wet.

The traditional associations of forget-me-nots, of course, are right there in their name. There are a number of stories supposedly explaining how these flowers came to be associated with the memory of loved ones (surely the most ridiculous being the one that apparently has a knight drowning under the weight of a bouquet of the things) but the true reasons are probably lost to history. My own suspicion is that it is perhaps ultimately because forget-me-nots are relatively unassuming as flowers go, making them an ideal symbol of beauty that should not be overlooked for the sake of more flashy but perhaps less reliable competitors.

Hound's-tongue Cynoglossum officinale, from here. Native to Europe, this plant has become established in many parts of North America.

Hound's-tongue, on the other hand, seems to get its name from the resemblance of its leaves to its namesake. This plant doesn't seem to have quite the same hold on human affection as the forget-me-not, and the reason for this may be indicated by some of its other vernacular names: 'monk's nit' or 'beggar's lice', in reference to its sticky seeds that adhere to clothing (perhaps 'gypsy flower' derives from the same source?) and, even more damning, 'rats and mice', referring to its unmistakeable smell.

REFERENCES

Hargrove, L., & M. G. Simpson. 2003. Ultrastructure of heterocolpate pollen in Cryptantha (Boraginaceae). International Journal of Plant Sciences 164 (1): 137-151.

Långström, E., & M. W. Chase. 2002. Tribes of Boraginoideae (Boraginaceae) and placement of Antiphytum, Echiochilon, Ogastemma and Sericostoma: a phylogenetic analysis based on atpB plastid DNA sequence data. Plant Systematics and Evolution 234: 137-153.

Ginseng and Ivy

Pate Schefflera digitata, photographed by Kahuroa.

The Araliaceae are a family of nearly 1500 species of flowering plants found around the world, but primarily in the Old World tropics. Most of its members are trees or shrubs, but there are also some herbaceous or climbing species. Many Araliaceae have palmate leaves, and they often produce inflorescences in umbels. Not that many Araliaceae hold much economic prominence: Tetrapanax papyriferus is used to make rice paper, while the genus Panax includes the ginsengs that are widely regarded as something of a wonder-drug for no apparent good reason. Some other species are well known as garden plants, such as ivy Hedera helix. Back in my home country of New Zealand, Araliaceae include some of the most familiar small native trees such as pate Schefflera digitata and the five-fingers and lancewoods of the genus Pseudopanax.

A young lancewood Pseudopanax crassifolius, photographed by Mike Hudson. Lancewood is notable for its differing growth habits over its lifespan: this individual is just beginning to change from its juvenile to its mature foliage. When the plant is young, the long, narrow, tooth-edged leaves hang down around the trunk. As the tree matures, it produces leaves that are shorter, broader and with less strong teeth, and that are held upwards and outwards. The juvenile and mature trees are so different in appearance that they were initially described as different species.

The Araliaceae have long been recognised as close relatives of the Apiaceae, the family including carrots and celery, to the extent that some authors have combined the two in a single family. Most recent researchers have maintained the distinction, but phylogenetic studies have indicated that some genera previously treated within the Apiaceae, notably the water and marsh pennyworts of the genus Hydrocotyle, are better treated as basal Araliaceae (Plunkett et al. 1997). Relationships within the Araliaceae are somewhat less straightforward, as molecular phylogenetic studies have indicated that there has been a great deal of homoplasy in morphological characters (Plunkett et al. 2004). Some of the larger genera in the family (notably the genus Schefflera, to which nearly half the species of Araliaceae have been assigned) appear to be significantly polyphyletic, some of them not even resolving in particularly proximate clades. The difficult nature of many araliaceous genera has long been realised: in 1868, the botanist Berthold Seemann referred to the then-poorly defined Panax as "one of the great lumber rooms of our science" (Wen et al. 2001).

American ginseng Panax quinquefolius, from here. Red ginseng is derived from the root of this species and the Asian P. ginseng; however, over-harvesting has lead to the endangerment of wild populations of the latter.

REFERENCES

Plunkett, G. M., D. E. Soltis & P. S. Soltis. 1997. Clarification of the relationship between Apiaceae and Araliaceae based on matK and rbcL sequence data. American Journal of Botany 84 (4): 565-580.

Plunkett, G. M., J. Wen & P. P. Lowry II. 2004. Infrafamilial classifications and characters in Araliaceae: Insights from the phylogenetic analysis of nuclear (ITS) and plastid (trnL-trnF) sequence data. Plant Systematics and Evolution 245 (1-2): 1-39.

Wen, J., G. M. Plunkett, A. D. Mitchell & S. J. Wagstaff. 2001. The evolution of Araliaceae: a phylogenetic analysis based on ITS sequences of nuclear ribosomal DNA. Systematic Botany 26 (1): 144-167.

Borage and Comfrey and Bugloss

Anchusa undulata ssp. granatensis. Photo by James Gaither.

The tribe Boragineae includes about 170 species of herbaceous flowering plants, mostly found in the Palaearctic region with only a couple of species extending into southern Africa. The group is well-distinguished by the presence of what are called fornices, the whitish lobes at the base of each petal that you can see in the photo above, as well as features of their seeds. Many Boragineae seeds have an elaiosome, a fatty plug at one end that attracts foraging ants (Hilger et al., 2004). The ants carry the seed back to their nest as food, but the plant produces enough seeds that at least some will not be eaten but will be able to germinate after being carried under the ground and away from anything else that might eat them.


Abraham-Isaac-Jacob, Trachystemon orientalis, a native of forests around the Black Sea and one of the more unusual species of Boragineae. Apparently the unusual name refers to the flowers changing colour as they age. Photo by Daniel Mosquin.

The species are divided between about fifteen genera (the exact number varies depending on whom you ask). The largest generally-recognised genus, Anchusa (the buglosses), was identified by Hilger et al. (2004) as para-/polyphyletic with a number of smaller genera also nested within the Anchusa clade, suggesting that the currently recognised constituent subgenera may need to be recognised as separate subgenera (or else the genera Lycopsis and Cynoglottis submerged into Anchusa). Other relationships within the tribe recognised by this and other studies include a close relationship between the genera Borago (borage) and Symphytum (comfrey), and between Nonea and Pulmonaria (lungwort). The basalmost member of the tribe is Pentaglottis sempervirens, which is also the only member of the tribe found in the Atlantic region of southwest Europe. The relict distribution of this species, as well as the concentration of diversity for the tribe overall, have been cited as supporting a Mediterranean origin for the Boragineae.


Green alkanet, Pentaglottis sempervirens, the sister species to all other Boragineae. Photo by Carl Farmer.

A number of members of the tribe have long been cultivated and many are even labelled by their botanical names as officinal (the Medieval Latin term 'officinalis' refers to a plant or substance that is kept in an apothecary; not surprisingly, many plants with supposed medicinal values are also eaten for their nutritional values). Borago officinalis, borage, is used as a salad or pot herb in Europe. Symphytum officinale, comfrey, has also been widely used medicinally, mainly for external uses such as soothing bruises (some of the properties attributed to comfrey verge on the ridiculous: a bath steeped in comfrey was supposedly able to restore a woman's virginity). Pulmonaria officinalis, lungwort, received its name because of the supposed resemblance of its blotchy leaves to lung tissue. Under the unabashedly loopy herbalist principle known as the Doctrine of Signatures, this outward resemblance indicated its suitability in treating lung diseases such as tuberculosis (in fact, lungwort contains toxic alkaloids that make it dangerous to take internally).

REFERENCES

Hilger, H. H., F. Selvi, A. Papini & M. Bigazzi. 2004. Molecular systematics of Boraginaceae tribe Boragineae based on ITS1 and trnL sequences, with special reference to Anchusa s.l. Annals of Botany 94 (2): 201-212.

Name the Bug: Fouquieria columnaris

Fouquieria columnaris. Photo by Josiah.

"But oh, beamish nephew, beware of the day,
If your Snark be a Boojum! For then
You will softly and suddenly vanish away,
And never be met with again!"

--Lewis Carroll, The Hunting of the Snark

Congratulations to Pat who identified the subject of the above photo right off the bat as Fouquieria columnaris (or Idria columnaris), a desert plant of southwest North America commonly known as the cirio (Spanish for 'candle') or boojum tree. The name 'boojum' comes from Lewis Carroll's allegorical* poem The Hunting of the Snark in which a company of mismatched adventurers attempts to capture a mysterious (and possibly non-existent) creature only to have one of their party disappear under puzzling circumstances.

*Many authors refer to The Hunting of the Snark as allegorical. 'Allegorical' may be shorthand for 'no, we don't know what he's on about, either'.

It is not hard to see how Carroll's eerie, creepy boojum became associated with this strange, eerie plant (though, to the best of my knowledge, F. columnaris has never been party to mysterious disappearances). The boojum has a restricted range, found on granite ranges in the Mexican states of Baja California and Sonora. Rainfall in these areas is low, averaging 120 mm per year (Bashan et al., 2007). Boojums can reach heights of up to 12 metres (Humphrey, 1935) but grow slowly, about three or four centimetres in a good year (Bashan et al., 2007). It can take 100 years for a boojum to reach maturity and begin flowering and large individuals may be more than 700 years old.

The usual growth form of a boojum is as a single tapering trunk - Pat's description of it as a "living telegraph pole" is appropriate, while Humphrey (1935) regarded it as "not unlike a greatly elongated inverted parsnip". The central stem may or may not divide into candelabra-like branches while individuals may deviate from the usual vertical growth to form strange loops or arches. The central stem is covered by short side branches arranged in a spiral pattern and carrying spines and small leaves.


An example of the unusual growth habits adopted by some boojums. From Bashan et al. (2007).

The genus Fouquieria includes eleven species of North American succulents that have been placed in their own separate family (the other Fouquieria species, the ocotillos, are low radiating shrubs). Recent studies have placed Fouquieria among the Ericales and most (but not all) molecular analyses support a sister-group relationship between Fouquieria and Polemoniaceae (the phlox family; Geuten et al., 2004).

REFERENCES

Bashan, Y., T. Khaosaad, B. G. Salazar, J. A. Ocampo, A. Wiemken, F. Oehl & H. Vierheilig. 2007. Mycorrhizal characterization of the boojum tree, Fouquieria columnaris, an endemic ancient tree from the Baja California Peninsula, Mexico. Trees 21: 329-335.

Geuten, K., E. Smets, P. Schols, Y.-M. Yuan, S. Janssens, P. Küpfer & N. Pyck. 2004. Conflicting phylogenies of balsaminoid families and the polytomy in Ericales: combining data in a Bayesian framework. Molecular Phylogenetics and Evolution 31 (2): 711-729.

Humphrey, R. R. 1935. A study of Idria columnaris and Fouquieria splendens. American Journal of Botany 22 (2): 184-207.