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.

Thistle Be The One (Taxon of the Week: Carduoideae)

The cardoon Cynara cardunculus with humans to scale. Photo from here.

The composite-flowering plants of the Asteraceae are one of the largest (23,000 species, according to Wikipedia) and most distinctive plant groups out there - even a complete botanical dunce like yours truly can usually recognise an example of Asteraceae. Asteraceae include such plants as daisies and chrysanthemums in which the "flower" is in fact a large number of tiny flowers all pressed together, hence the old name for the family of "Compositae". Different authors have proposed different classifications within Asteraceae over the years, but twelve subfamilies were recognised by Panero & Funk (2008). The subfamily Carduoideae as recognised by these authors includes the three tribes Dicomeae, Tarchonantheae and Cardueae (earlier authors had used the name to cover a broader paraphyletic assemblage, or restricted it to include only Cardueae). The genus Oldenburgia may be included in Tarchonantheae or it may be placed in its own separate tribe (Funk et al., 2009). No unique morphological features characterise this subfamily (though most species have a ring of papillae on the style underneath the stigmatic branches), but it is well supported molecularly.

The tribes Dicomeae and Tarchonantheae are primarily found in Africa and Madagascar (two species of Dicomeae and one of Tarchonantheae are found in Asia). The seventeen species of Tarchonantheae (including Oldenburgia) are all shrubs or trees; the 75-100 species of Dicomeae include herbs, shrubs and trees. Tarchonantheae includes the genus Brachylaena, species of which predominate in southern African and Madagascan woodlands. Brachylaena species are noted for producing dense, high quality wood, and are also among the largest of the Asteraceae, reaching 40 m in height (Beentje, 2000).


Brachylaena discolor from southeastern Africa. Photo from here.

The largest by far of the three tribes is the Cardueae*, the thistles, with some 2500 species distributed through Eurasia from the Mediterranean to central Asia. The majority of Cardueae are herbs, though there are a few small shrubs or even small trees in the tribe. Most members of Cardueae have distinctive discoid flower heads** and, of course, many have spiny leaves.

*I have just been through the painful, arduous and not-entirely-productive process of trying to decide whether 'Cardueae' or 'Cynareae' is the correct name for this tribe; both names are used regularly. Lamarck & de Candolle published the name 'Cynarocephalae' in 1806 (Reveal, 1997); Cardueae was published by Cassini in 1819 (Solbrig, 1963). The question therefore hinges on whether the '-cephalae' in Cynarocephalae represents a suffix like '-idae' or '-aceae' or whether the name is descriptive of plants with 'heads like Cynara'; if the former, Cynareae has priority from 1806; if the latter, Cynareae was not published until 1830 (and illegitimately so at that) and Cardueae has priority. Botanists still seem to be in the process of duking out which interpretation is corrent, and I suspect that it may take the ICBN stepping in to settle the matter.

**Composite flower heads may contain both 'ray' and 'disk' florets (the little individual flowers). If you think of a daisy, the 'ray' florets are the ones around the edge that carry the large petals while the 'disk' florets are the central ones without petals. Discoid flower heads like those of Cardueae contain only disk florets and no ray florets.


Side view of flower head of Atractylis cancellata, a Mediterranean thistle species in which the rosette of (particularly evil-looking) leaves around the flower head curls upwards to surround it. Photo by Manuel Ramos.

Species of Cardueae most often bring themselves to humanity's attention through the fact that a number of them are significant weed species, and very few Cardueae are regarded with any sort of affection. The Scotch thistle Onopordum acanthium is of course popular in Scotland where it is the national flower; according to legend, a Scottish encampment was saved from a sneak attack by Vikings when one of the invaders yelled out after stepping on a thistle, alerting the sentries to their presence. Also granted a certain regard is Cynara cardunculus, the cardoon/globe artichoke. Earlier classifications recognised two species, the cardoon C. cardunculus grown for its edible stalks and the artichoke C. scolymus grown for its similarly edible flower heads, but there is no doubt that the latter is a horticulturally derived variety of the former. Perhaps the best demonstration of this is that escaped seeds from artichoke fields in California and Australia have given rise to wild populations of 'cardoons' (Sonnante et al., 2007). I will also note that artichokes would also be a feature of my ideal garden - not because I'm a fan of eating artichokes (I think they're pretty tasteless) but because these two-metre tall thistles are such spectacular plants.

And that's all you'll be hearing from me for a little while - five-thirty tomorrow morning, I leave for two weeks in the field. Feel free to talk among yourselves until I get back.

REFERENCES

Beentje, H. J. 2000. The genus Brachylaena (Compositae: Mutisieae). Kew Bulletin 55 (1): 1-41.

Funk, V. A., A. Susanna, T. F. Steussy, & H. E. Robinson. 2009. Classification of Compositae. In Systematics, Evolution, and Biogeography of Compositae (V. A. Funk, A. Susanna, T. F. Stuessy & R. J. Bayer, eds) pp. 171-189. International Association for Plant Taxonomy (IAPT): Vienna.

Panero, J. L., & V. A. Funk. 2008. The value of sampling anomalous taxa in phylogenetic studies: major clades of the Asteraceae revealed. Molecular Phylogenetics and Evolution 47 (2): 757-782.

Reveal, J. L. 1997. Early suprageneric names in Asteraceae. Compositae Newsletter 30: 29-45.

Solbrig, O. T. 1963. Subfamilial nomenclature of Compositae. Taxon 12 (6): 229-235.

Sonnante, G., A. V. Carluccio, R. Vilatersana & D. Pignone. 2007. On the origin of artichoke and cardoon from the Cynara gene pool as revealed by rDNA sequence variation. Genetic Resources and Crop Evolution 54 (3): 483-495.

My Flower is a Trumpet (Taxon of the Week: Solanales)

Fruit of Physalis alkekengi var. franchetii, the Chinese lantern plant. In species of Physalis, the persistent calyx that is characteristic of Solanales has become greatly expanded to form a protective covering for the (rather tasty!) fruit. Photo from here.

While intrafamilial relationships among flowering plants have a reputation for being contentious, one concept that has long been supported by most authors is a close connection between the Solanaceae (nightshades) and the Convolvulaceae (morning glories). Originally united on the basis of features such as similar flower structure and internal phloem in most species (the phloem is the nutrient-carrying tissue in a plant's stem, and in these taxa it is found mixed in with the central water-carrying xylem as well as around the outside of the stem as in other plants), molecular analyses have continued to support their relationship (Bremer et al., 2001). In the most recent APG classification, the two families form the greater part of the order Solanales, along with three smaller families - Montiniaceae (a family of trees and shrubs found in southern Africa and Madagascar) and the isolated genera Sphenoclea and Hydrolea (two pantropical families of small shrubby plants both found growing near or in water) (APG II, 2003).


Montinia caryophyllacea, a shrub of the Montiniaceae found from South Africa to Angola. Photo from Aluka.

The three small families, which remain outside the Solanaceae-Convolvulaceae clade (which I'll call the "core Solanales"), are placed in the Solanales largely on the basis of molecular analyses only, and so far few or no morphological features have been identified that support their referral. Peter Stevens' Angiosperm Phylogeny Website does suggest a couple of features - some shared secondary metabolites, and the fact that the calyx persists on the mature fruit (you've all seen this - it's the sepals around the stalk of a tomato). Erbar et al. (2005) identified features of flower development shared between Hydrolea and the core Solanales, but not the other two families. Most Solanales are, like other members of the Asteridae clade to which they belong, sympetalous - that is, the petals are to some degree joined together at their base. One of the distinctive features of many Convolvulaceae and Solanaceae flowers, in fact, is that they take sympetaly to its extreme - the petals are entirely fused to form a bowl or trumpet. However, while the core Solanales and Hydrolea are "late sympetalous", where the petals initially start growing separately in the bud and are only joined later by the growth of connecting bridges, Sphenoclea is "early sympetalous", where the petals are connected pretty much right from the start. Montiniaceae are not sympetalous at all, but have entirely separated (and not very big) petals.


Kumara or sweet potato, Ipomoea batatas. Photo from here.

Within the core Solanales, the Convolvulaceae are mostly vines (though the basalmost member of the Convolvulaceae, Humbertia madagascariensis, is a large tree), while the Solanaceae range from small herbaceous plants to large trees. As well as being a tree, Humbertia also differs from other Convolvulaceae in lacking internal phloem. This is intriguing, because Humbertia's sister relationship to all other Convolvulaceae means that it is just as parsimonious for internal phloem to have developed independently in the two families as for it to be a true synapomorphy of the core Solanales. The herbaceous vines of the Convolvulaceae are commonly referred to as morning glories, referring to the time of opening of their large but often short-lived flowers, but other common names are just as evocative - trumpet vine, or railway creeper (the latter because many species have become widely distributed as adventives inadvertently carried by human activity). They are also, somewhat less poetically, known as bindweeds. One such plant, Ipomoea batatas, grows large tubers that are the world's second-most important root crop, the sweet potato (Stefanović et al., 2002).


Dodder, Cuscuta epithymum, overgrowing a sage plant. Photo from Kingston University.

One particularly distinctive genus of Convolvulaceae are the dodders, Cuscuta, twining parasites of other plants. Dodders contain little or no chlorophyll of their own, and their roots degenerate early on in life so the mature plant is not connected to the ground. The leaves are minute, and one might be forgiven for thinking that they were not there at all. Cuscuta has been placed in its own family in the past, but most of the characters this has been based on are uniquely derived features resulting from its parasitic lifestyle. Neyland (2001) and Stefanović et al. (2002) confirmed that Cuscuta is nested among normal photosynthetic Convolvulaceae. Cuscuta also provides a remarkable example of convergent evolution - in its general appearance, it is almost indistinguishable from the genus Cassytha, also commonly called "dodder". Cassytha, however, is not closely related to Cuscuta at all, but is instead a member of the distant family Lauraceae, and so more closely related to magnolias.

The Solanaceae also include a number of significant taxa. As a group, most Solanaceae are decidedly toxic (at least from a human perspective), and the family includes such infamous plants as deadly nightshade (Atropa belladonna), Jerusalem cherry* (Solanum pseudocapsicum) and Jimson weed (Datura stramonium). On the other hand, the family also includes a number of plants widely grown for human consumption, such as potatoes (Solanum tuberosum), tomatoes (Solanum lycopersicum**) and eggplants (Solanum melongena). A few Solanaceae manage to be both toxic and grown for human consumption - most notably good old tobacco (Nicotiana tabacum). The question arose recently at the Te Papa blog as to whether the common black nightshade (Solanum nigrum) is toxic or not - while it is widely supposed to be, it is actually eaten in some parts of the world (Edmonds & Chweya, 1997). Fruit are eaten when ripe or cooked (the huckleberry of North America is either Solanum nigrum or a close relative), while leaves are boiled and eaten as a pot herb. It seems that, just to confuse matters, toxicity of this plant varies from place to place.

*No, I don't know why they're calledd that.

**For those who are wondering what happened to 'Lycopersicon esculentum', it has been well established that 'Lycopersicon' species fall phylogenetically within Solanum (as Solanum section Lycopersicum), and in fact are very closely related to potatoes (somatic hybrids between potatoes and tomatoes have been succesfully produced, though it looks like produce-wise they're a bit of a second Raphanobrassica***). If the tomato is included in Solanum, then its name reverts back to that originally given to it by Linnaeus way back in 1753.

***Raphanus (radishes) and Brassica (cabbages) are also closely related to each other, and a lot of time and effort was invested by the early Soviets into producing a hybrid between the two that would possess the root of a radish with the leaves of a cabbage - two crops for the price of one! The Raphanobrassica cross was successfully produced in the 1920s - sadly, it turned out to have the root of a cabbage and the leaves of a radish.

REFERENCES

APG II (Angiosperm Phylogeny Group). 2003. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II. Botanical Journal of the Linnean Society 141: 399-436.

Bremer, K., A. Backlund, B. Sennblad, U. Swenson, K. Andreasen, M. Hjertson, J. Lundberg, M. Backlund & B. Bremer. 2001. A phylogenetic analysis of 100+ genera and 50+ families of euasterids based on morphological and molecular data with notes on possible higher level morphological synapomorphies. Plant Systematics and Evolution 229: 137-169.

Edmonds, J. M., & J. A. Chweya. 1997. Black nightshades. Solanum nigrum L. and related species. Promoting the conservation and use of underutilized and neglected crops 15. Institute of Plant Genetics and Crop Plant Research, Gatersleben/International Plant Genetic Resources Institute, Rome, Italy.

Erbar, C., S. Porembski & P. Leins. 2005. Contributions to the systematic position of Hydrolea (Hydroleaceae) based on floral development. Plant Systematics and Evolution 252: 71-83.

Neyland, R. 2001. A phylogeny inferred from large ribosomal subunit (26S) rDNA sequences suggests that Cuscuta is a derived member of Convolvulaceae. Brittonia 53 (1): 108-115.

Stefanović, S., L. Krueger & R. G. Olmstead. 2002. Monophyly of the Convolvulaceae and circumscription of their major lineages based on DNA sequences of multiple chloroplast loci. American Journal of Botany 89 (9): 1510-1522.

Hebe or Veronica?

Veronica pimeleoides flowers. Photo from the Hebe Society.

Hebes* are some of the iconic plants of New Zealand. New Zealand doesn't have a huge diversity of flora compared to some other parts of the world, but there are some groups of plants that have just gone ballistic, achieving incredible diversity, and New Zealand is home to more than a hundred hebe species. The botanist Armstrong commented in the late 1800s that the group was so diverse that New Zealand's flora would still be of interest even if the country's vegetation was solely composed of hebes (Metcalf, 2006). Their delicate inflorescences are a common sight in the field and in the garden. This Monday's taxon of the week is a hebe - Veronica pimeleoides subspecies pimeleoides.

*If there's anyone who hasn't encountered the word before, "hebe" is pronounced with two long 'e's - hee-bee.

Those of my readers who are familiar with hebes may have blinked a little there. Our conception of the place of hebes in the botanical world has changed a little in recent years. Not only has there been the transfer of hebes from the Scrophulariaceae to the Plantaginaceae* (Olmstead et al., 2001), there is the small matter of their generic allocation. During the 1800s and early 1900s, most of those New Zealand (and a few South American) species that would later become recognised as hebes were included in the genus Veronica, a genus originally established for an assortment of temperate Northern Hemisphere taxa. The genus name Hebe (after the Greek goddess of youth, the daughter of Zeus and Hera, wife of Heracles after his apotheosis, and the server of ambrosia at the gods' table) was originally established in 1789, but didn't really enter use until the 1920s (Albach et al., 2004). Even after the botanical community recognised the distinctiveness of Hebe, horticulturists still tended for some time to regard the hebes as Veronica (Metcalf, 2006). Over time, everyone seems to have adjusted to the new view, and some groups of 'Hebe' species were even committed to further segregate genera - Parahebe, Chionohebe and (ha ha) Hebejeebie.

*Olmstead et al. (2001) suggested that the family including Hebe be called Veronicaceae, but the Botanical Code requires the correct name to be Plantaginaceae.

Then along came Albach & Chase (2001), ready to shake things up again. As it turns out, Veronica minus Hebe is a paraphyletic assemblage. While zoologists tend to divide genera in such a situation, botanists are more likely to combine, and Hebe has reverted back to part of Veronica - specifically, Veronica subgenus Pseudoveronica section Hebe (Albach et al., 2004; Garnock-Jones et al., 2007). So far, the re-reallocation of hebe species does not seem to have gained a huge acceptance among the general public, so this is currently a work in progress.


Another view of Veronica pimeleoides (this silver-leaved variety seems to be the most popular in cultivation). Photo from here.

The species Veronica pimeleoides is native to the South Island of New Zealand, being found pretty much along the exact midline of the island from the Inland Kaikouras south to central Otago. There are two recognised subspecies, V. pimeleoides ssp. pimeleoides and 'Hebe' pimeleoides ssp. faucicola (Kellow et al., 2003). A form that has been known as Hebe pimeleoides var. glauca-caerulea is only known from cultivation and has never been confirmed in the wild state since its original collection, so is currently regarded as of uncertain status. The two recognised subspecies are mainly distinguished by their growth form and habitat. V. p. ssp. pimeleoides, which is found over most of the species' range, is a low, creeping shrub found near lakes and rivers (Kellow et al, 2003, describe it as growing to 30 cm in height, but Metcalf, 2006, describes it as rarely more than 5 cm tall). V. p. ssp. faucicola is found on rock faces in the southernmost part of the range in central Otago, and is a much taller plant growing up to 70 cm in height. Subspecies faucicola also tends to have lighter flowers than subspecies pimeleoides - the former has flowers that are mauve to pink, while the latter is blue to mauve. The chemical signature of the two subspecies is, as far as is known, indistinguishable, sucggesting that the two have only recently differentiated from each other (Kellow et al., 2003).

REFERENCES

Albach, D. C., & M. W. Chase. 2001. Paraphyly of Veronica (Veroniceae; Scrophulariaceae): evidence from the internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA. Journal of Plant Research 114 (1): 9-18.

Albach, D. C., M. M. Martínez-Ortega, M. A. Fischer & M. W. Chase. 2004. A new classification of the tribe Veroniceae - problems and a possible solution. Taxon 53 (2): 429-452.

Garnock-Jones, P., D. Albach & B. G. Briggs. 2007. Botanical names in Southern Hemisphere Veronica (Plantaginaceae): sect. Detzneria, sect. Hebe, and sect. Labiatoides. Taxon 56 (2): 571-582.

Kellow, A. V., M. J. Bayly, K. A. Mitchell, K. R. Markham & P. J. Garnock-Jones. 2003. Variation in morphology and flavonoid chemistry in Hebe pimeleoides (Scrophulariaceae), including a revised subspecific classification. New Zealand Journal of Botany 41: 233-253.

Metcalf, L. 2006. Hebes: A Guide to Species, Hybrids and Allied Genera. Timber Press.

Olmstead, R. G., C. W. de Pamphilis, A. D. Wolfe, N. D. Young, W. J. Elisons & P. A. Reeves. 2001. Disintegration of the Scrophulariaceae. American Journal of Botany 88(2): 348-361.