Field of Science

Checker Mallows

The crowdfunding campaign for my research on New Zealand harvestmen is still active. So far we're about 25% of the way towards the goal! Please click on the link above, and do your part to support your favourite arachnologist.

Flowering spike of Sidalcea nelsoniana, copyright Rhiannon Thomas.

Regular readers may have noticed that it's been a bit quiet around here lately. The last few weeks at chez Christopher have been... hectic. I have been writing posts but not had the time to publish them. So over the next few days, you'll be seeing a bit of a run of short posts in quick succession. Keep your eyes out.

The handsome plant you see above is a representative of Sidalcea, a genus of about thirty species found in the north of Mexico and the western United States. Members of this genus are commonly known as checker mallows (apparently because of the pattern of veins on the petals of some species); in the British gardening trade, they are also known as prairie mallows. As indicated by their vernacular names, Sidalcea species belong to the mallow family Malvaceae, and are hence related to other flowering plants such as cotton or hibiscus. These affinities are also reflected by their genus name, which is a portmanteau of the names of two other genera of Malvaceae, Sida and Althaea. Checker mallows differ from other members of the Malvaceae in having flowers with stamens that separate from the stamineal column in two tiers, an inner and an outer ring.

Most species of checker mallow are herbs; a few may develop into subshrubs. The genus includes both perennial and annual species. Stems of checker mallows are mostly more or less erect though they are often basally reclining or decumbent towards the base;it is not uncommon for decumbent stems to become secondarily rooted into the ground and develop into spreading stolons (or 'rhizomes'). Flowers of checker mallows are usually various shades of purple; a small number of species have white flowers (or white forms may occur in usually purple species). Many species of this genus are supposed to be difficult to identify: hybridisation is not uncommon, and some species are quite plastic in their own right. Young plants may also have a quite different appearance, including differently shaped leaves, from mature plants.

Sidalcea campestris, photographed by Amy Bartow.

The primary monograph of Sidalcea was published by E. M. F. Roush in 1931. She divided the genus between three subgenera, two of which contained only a single species each with all the remainder placed in her subgenus Eusidalcea (since the publication of Roush's monograph, a third non-Eusidalcea species has been recognised). These species are all perennials that, among other features, lack the variation in leaf shape with growth seen in Eusidalcea. More recent molecular analyses have supported Roush's arrangement arangement (Andreasen & Baldwin 2003). However, they have not supported Roush's division of Eusidalcea into separate sections for the annual and perennial species; instead, it appears that one or the other habit (it is unclear which) has arisen multiple times.

Like other diverse plant genera found in the California region, Sidalcea has attracted a certain degree of research into its evolutionary dynamics. Comparison of evolutionary rates between species has found that, as might be expected, annual lineages evolve faster than perennial ones (Andreasen & Baldwin 2001). Most species within each life-history class appeared to evolve at similar rates to each other, except for three perennial species: the three non-Eusidalcea species referred to above. One of these species, Sidalcea stipularis (the only one not known to Roush in 1931) showed evidence of an unusually high evolutionary rate for a perennial; this species is restricted to a very small population (only a few hundred plants may exist in the wild) and may have been subject to a higher rate of effective genetic drift. In contrast, the other two species have diverged more slowly than expected. One of these species, S. malachroides, is a presumably slow-lived subshrub; the other, S. hickmanii, commonly germinates after fires from seeds that may have remained in the ground for a number of years. In both cases, the overall result is that particular genotypes may persist in the population longer than in species with a more rapid turnover.

Oregon checkerbloom Sidalcea oregana ssp. spicata, copyright Dcrjsr.

Another feature of Sidalcea population dynamics to have attracted interest is the occurrence in several species of gynodioecy, a phenomenon where some individuals of a population have flowers with both male and female organs whereas other individuals have female organs only. The persistence of such an arrangement raises questions: because hermaphroditic individuals have the potential to contribute to more reproductive pairings than female-only individuals, shouldn't the former end up out-competing the latter and eliminating them from the population? This has lead to the inference that some factor(s) must give the female-only individuals an advantage that allows them to persist. Ashman (1992) found in germination tests of Sidalcea oregana spp. spicata that seeds that came from female-only plants tended to germinate into healthier, more vigorous offspring than those from hermaphrodites. It may be that plants that can only produce seed by outcrossing are less vulnerable to the effects of inbreeding, or perhaps not having to invest energy in making pollen means that the parent can put more energy into producing seeds.


Andreasen, K., & B. G. Baldwin. 2001. Unequal evolutionary rates between annual and perennial lineages of checker mallows (Sidalcea, Malvaceae): evidence from 18S–26S rDNA internal and external transcribed spacers. Mol. Biol. Evol. 936–944.

Andreasen, K., & B. G. Baldwin. 2003. Reexamination of relationships, habital evolution, and phylogeography of checker mallows (Sidalcea; Malvaceae) based on molecular phylogenetic data. American Journal of Botany 90 (3): 436–444.

Ashman, T.-L. 1992. The relative importance of inbreeding and maternal sex in determining progeny fitness in Sidalcea oregana ssp. spicata, a gynodioecious plant. Evolution 46 (6): 1862–1874.

Roush, E. M. F. 1931. A monograph of the genus Sidalcea. Annals of the Missouri Botanical Garden 18 (2): 117–244.

New Zealand Harvestmen: Please Help

The cave-dwelling Forsteropsalis photophaga, a remarkable harvestman species described in Taylor & Probert (2014).

As regular readers of this blog will be well aware, I've been working for several years now, off and on, on the taxonomy of long-legged harvestmen of the family Neopilionidae from Australia and New Zealand. In the past few years, this has been a bit more off than on: the necessities of earning a crust have meant that I haven't had the time to dedicate to full-time harvestman research. Nevertheless, I've been putting things together here and there where I can and an enormous amount of progress has been made. Back when I first decided to investigate this group of animals in 2000/2001, there were a handful of named species, often with descriptions amounting to nothing more than a couple of vague lines, all but unidentifiable in practice. Over time, I've redescribed each of these species in turn, as well as describing and naming a pile of new ones. We've learnt things about these animals we never knew before, such as the presence in many populations of a remarkable divergence within males to the extent that to the uninitiated they might be (and have been) mistaken for completely different species. We've seen the incredible range of forms in this group, from long-jawed monsters like to one at the top of this post, to heavily armoured cryptic soil-dwellers like in this photo by Stephen Thorpe.

After many years, I feel I'm finally approaching the point where I can put the finishing touches on my revision of the New Zealand neopilionids (for a given value of 'finish', of course, because there is no group of organisms for which the work is ever truly finished). Ideally, I would like to publish something incorporating a complete overview of this group of animals, a complete guide to all the known species offering a one-stop-shop to allow anyone, anywhere to confidently identify any specimen that might come to their hand. It's also important to me that I publish this guide in an open-access format so that it's also available at any time.

But to do that, I need your help. In order to be able to travel to the New Zealand museums that hold types and other crucial specimens that I need to examine, and to cover the publication fees of the resulting product, I've started a crowdfunding drive. Head over to and you'll be able to support my research, follow the results as they become available, and receive full acknowledgement in the resulting publication(s). Even if you can't support me directly myself, you would be helping immensely if you inform others of my campaign, whether through social media, in person, or any other medium that makes itself available. Together, we can bring this truly incredible group of animals the recognition they so richly deserve!

If you want to see some of my work on harvestmen that's already come out, check out the links below:

Remarkable things
Possibly the coolest thing I had published this year
Score one for biogeography
How to wipe out a family
The saga of Forsteropsalis fabulosa
More on the New Zealand Opiliones
Bye, bye, Spinicrus
The eater of light
New Zealand fills a biogeographical gap

Gazelles and their Kin

Female steenbuck Raphicerus campestris, copyright Yathin S. Krishnappa.

Ever since biblical times, gazelles have been a byword for a kind of watchful elegance, always on guard against unwanted advances. It is not difficult to see how such an analogy arose: on their native savannah, gazelles are indeed always on the alert, wary of the threat of predators and quick to respond to alarm. It is a habit that has served them for millions of years.

The Antilopini are an assemblage of about thirty species of mostly smaller antelope found in Africa and Asia*. The smallest are the dikdiks of the genus Madoqua which may be only a foot or so in height and weight just a few kilos; the tallest, the dibatag Ammodorcas clarkei, stands about 90 cm at the shoulder and weighs about 30 kilograms. They are mostly associated with arid or semi-arid habitats: savannahs, deserts, steppes and the like. Some species form sizeable herds; others live solitary lives.

*Before I go too much further, I should note that J. K. Revell over at his site Synapsida has written a number of posts about bovids (antelopes, cattle, etc.) over the the past few years that I heartily recommend. To the best of my knowledge, he hasn't gotten to antilopins yet, so I should be safe on that front.

Female and male oribi Ourebia ourebi, copyright Bill Higham.

Modern researchers largely agree on dividing the Antilopini between four major lineages, recognised as subtribes. One contains a single species, the oribi Ourebia ourebi, a smaller species with short, straight horns found in eastern sub-Saharan Africa. The Raphicerina, including the dikdiks Madoqua, the steenbucks and grysbucks Raphicerus and the beira Dorcatragus megalotis, are similar small, short-horned species. The Raphicerina and oribi are solitary species with individuals maintaining exclusive territories (at least between members of the same sex). They advertise their territories through the use of defecation sites together with the marking of vegetation using scent glands in front of the eye. The Raphicerina are exclusively browsers, concentrating on higher-quality food sources; in contrast, the oribi is a grazer and consequently must occupy a larger territory than the other species. Females of Raphicerina and oribi are hornless; in most other Antilopini (with some exceptions noted below), horns are present in both sexes though the females' horns are shorter and more slender.

Przewalski's gazelles Procapra przewalskii, copyright Yilun Qiao.

The majority of the remaining Antilopini live in herds though males of most species will claim temporary territories during the breeding season as they attempt to gather harems of females. The central Asian gazelles of the genus Procapra are placed in their own subtribe; these are three pale, medium-sized species found on steppes and high-altitude grasslands between the Himalayan plateau and Mongolia. They have rear-swept horns that make them look a bit like a gazelle that is trying to pass itself as a goat. Procapra gazelles may not be immediately related within the Antilopini to the true gazelles in the largest of the four subtribes, the Antilopina. Until recently, most authors would have treated the great majority of the Antilopina species in the genus Gazella; however, questions about the monophyly of this genus in the broad sense have lead to the recognition of three separate genera of gazelles: Gazella sensu stricto, Nanger and Eudorcas. The Nanger species, which include the dama gazelle N. dama and Grant's gazelle N. granti, are relatively large gazelles with a conspicuous white rump that is absent in the other two genera. The genus Eudorcas includes perhaps the most familiar gazelle species, Thomson's gazelle E. thomsoni of Kenya and Tanzania, which forms much larger herds than other gazelle species.

Mhorr gazelles Nanger dama mhorr at Tierpark Hellabrunn in München, copyright Rufus46.

The remaining living Antilopina species are all placed in their own separate genera. The springbuck Antidorcas marsupialis of southern Africa also forms large herds that used to number in the tens of thousands before hunting and habitat loss reduced their population. Springbucks are best known, of course, for their habit of 'pronking', a mode of bounding with all four legs held stiff and landing simultaneously, most often seen when the animal is alarmed or at play. Pronking is not unique to springbucks (other gazelles do it too) but it is made particularly noticeable in this species by a crest of white hairs towards the rear of the back that is erected at the same time.

Springbuck Antidorcas marsupialis engaged in some pronking, copyright Hans Stieglitz.

In other species of Antilopina, only the males have horns. The gerenuk Litocranius walleri and dibatag Ammodorcas clarkei are two slender species found in eastern Africa that differ from other Antilopina in being browsers rather than grazers and maintaining permanent exclusive territories. Both these species habitually feed while standing erect on the hind legs, allowing them to browse at higher levels than they could otherwise; they are even able to walk about to a certain extent in this pose, albeit perhaps not in a manner that could be called graceful. Outside of Africa, the blackbuck Antilope cervicapra is found in grasslands and woodlands of the Indian subcontinent (there is also supposed to have been a small introduced population of them near Geraldton here in Western Australia, though it may have since been eradicated). Males of this species have long, spirally twisted horns; mature males are also the only 'blackbucks' that are actually black (at least dorsally) whereas females and young males are light brown.

Pair of juvenile dibatags Ammodorcas clarkei at a rescue centre, copyright F. Wilhelmi.

Perhaps the most distinctive member of the Antilopina, however, is the saiga Saiga tatarica. This is the only species that is known to never be territorial, forming large herds in its native habitat of the central Asian steppes (technically, the social habits of the little-studied dibatag are largely unknown but it would not be unreasonable to presume that they are similar to those of the gerenuk). It is more robust than other Antilopina species; indeed, there was long uncertainty about whether saiga are more closely related to gazelle or goats. The nostrils of saiga are inflated to a hanging proboscis that is usually presumed to function as protection for the respiratory tissues from the dust of their near-desert habitat. However, there may also be a display function involved; during the mating season, the proboscis of males becomes engorged while scent glands in front of the eyes produce pungent secretions (so maybe the function of the proboscis is actually to somehow protect the saiga from its own stench). Unfortunately, the saiga (among other Antilopini species) is currently regarded as critically endangered, with only a fragment of its historical population surviving. There was a time when the saiga was thought to be something of a conservation success story: after being almost wiped out in the early 1900s, populations built up to about two million by the 1950s. But in the last few decades, the combined effects of factors such as habitat loss, disease and the demand for their horns from everyone's favourite country to turn the extermination of endangered species into a pointless investment bubble have caused numbers to crash back down to an estimated 50,000 or so (as relayed by Wikipedia).

Pair of saiga Saiga tatarica, copyright N. Singh.

Fossil species have been assigned to the genus Gazella from as far back as the Miocene though there may be grounds for debating how many of them are true Gazella. For instance, Bärmann (2014) commented on preliminary results of a phylogenetic analysis including the Pakistani Miocene species G. lydekkeri (from the well-studied Siwalik deposits) that suggested that it might be placed outside the Antilopina crown group. Other fossils of Antilopini inform us that the modern blackbuck is the sole survivor of a lineage of spiral-horned antelopes that was previously more widespread in Eurasia. The saiga was more widespread in the past as well, with either the modern or a closely related species known during the Pleistocene from more northerly parts of Siberia (at which point, presumably, there may have been saiga in the taiga) and even in northernmost North America. If they do disappear completely, it will be a sad end to a long history.


Bärmann, E. V. 2014. The evolution of body size, horn shape and social behaviour in crown Antilopini—an ancestral character state analysis. Zitteliana B 32: 185–196.

Macdonald, D. (ed.) 1984. All the World's Animals: Hoofed Mammals. Torstar Books: New York.

Peering through a Limpet's Keyhole

Keyhole limpet Fissurella latimarginata, copyright Jan Maximiliano.

In an earlier post, I introduced you to the slit limpets, conical- or flat-shelled gastropods in the family Fissurellidae that possess a longitudinal slit at the front of their shells in order to help achieve the imposrtant condition of having one's anus as far away from one's mouth as possible. The image above shows another member of the same family, but this time known as a keyhole limpet. In the keyhole limpets of the genus Fissurella, the slit has been closed off and modified into a rounded opening bound by a callus at the shell's apex. The apex is located sub-centrally on the shell which is also radially ornamented (Simone 2008). Other interesting features of the genus include a tendency for the radula to be asymmetrical with the three- or four-cusped lateral teeth larger on one side than the other. Two related genera, Amblychilepas and Macroschisma, differ primarily in having larger soft bodies that cannot be retracted under the shell whereas Fissurella species are able to seal themselves in (Aktipis et al. 2011).

Fissurella volcano, copyright Jerry Kirkhart.

Various Fissurella species are found around the world. They have been divided between several subgenera, but Fissurella taxonomy is complicated by the fact that the overall shape of the shell is strongly affected by the nature of the substrate each individual makes its home. Truly reliable identification of distinct taxa requires detailed knowledge of the soft anatomy which is apparently still little-known for many species. According to Simone (2008), there is a correlation between shell height and energy level of each species' preferred habitat: species found in higher-energy environments (such as shorelines subject to heavy surf) tend to have higher shells (which surprises me because, if you'd asked me to guess, I might have expected the opposite).

As far as humans are concerned, though, most keyhole limpets have fairly little economic impact. Larger species, which can get up to about ten centimetres in size (many are much smaller), are harvested for food around the coast of South America. I also came across a reference to a Fissurella species being regarded as a pest in abalone aquaculture, as both species are algae-grazers and compete for food. Other than that, one imagines that their pre-perforated shells could be very useful for children wanting to make a (possibly somewhat malodorous) necklace as a souvenir of a trip to the beach.


Aktipis, S. W., E. Boehm & G. Giribet. 2010. Another step towards understanding the slit-limpets (Fissurellidae, Fissurelloidea, Vetigastropoda, Gastropoda): a combined five-gene molecular phylogeny. Zoologica Scripta 40: 238–259.

Simone, L. R. L. 2008. A new species of Fissurella from São Pedro e São Paulo Archipelago, Brazil (Vetigastropoda, Fissurellidae). Veliger 50 (4): 292–304.


The Queensland pselaphine Sunorfa nigripes, from Chandler (2001).

When I began researching the taxon that was to be the subject of this post, I was surprised to discover that it had weaseled its way onto this site once before. Back in the day, I used an example of the beetle genus Sunorfa to illustrate a post about a closely related genus for which I had been unable to find an image (before a reader pointed me in the direction of one). Sunorfa is a member of that wonderful group of miniature gargoyles, the Pselaphinae (I had the pleasure/pain of sorting a handful of pselaphines at work just the other week; their minute size [usually only a millimetre or two long] makes them a real challenge to work with but their bizarre morphologies make it impossible to resent them). Most species of Sunorfa are found in tropical rainforest litter in southern Asia and Australasia from Sri Lanka to Fiji with the highest diversity of species in New Guinea. In addition, a handful of species are found in the Seychelles. I haven't come across any direct indication of what Sunorfa are doing in all these places but presumably, like other pselaphines, they are predators of even smaller arthropods.

Distinctive features of Sunorfa compared to other pselaphines include a strong transverse sulcus (groove) across the rear part of the pronotum, and a cylindrical abdomen in which the upper tergites and lower sternites are fused into single continuous rings. They also have characteristic foveae (deep depressions) on the top of the head, the base of the elytra including on each side at the 'shoulders', and in the middle of the metasternum (the rear underside section of the thorax) (Chandler 2001). Similar foveae are found in one form or another, in one place or another, on most pselaphines. They have received a lot of attention in taxonomic studies (their appearance and distribution is one of the most reliable features in distinguishing pselaphine taxa) but their function is less well known. Chandler (2001) expressed the opinion that foveae in different parts of the body serve different purposes. Those on the thorax have solitary, sensilla-like setae at their centres and probably represent sensory structures of some kind. Conversely, foveae on the head and abdomen lack such setae and commonly connect to one another internally to form solid tubes. These tubes may function as struts, providing the body with rigidity and strength as the animal is reduced down in size.


Chandler, D. S. 2001. Biology, morphology, and systematics of the ant-like litter beetle genera of Australia (Coleoptera: Staphylinidae: Pselaphinae). Memoirs on Entomology, International 15: 1–560.

All that is Silver is not Fish

Common silverfish Lepisma saccharina, copyright Christian Fischer.

The insects are deservedly recognised as one of the most successful groups of organisms on the planet. Thanks in no small part to their unlocking the ability of flight, insects can be seen today in almost every part of the planet above sea level. But not all insects, of course, are flighted; many remain firmly on the ground. A large proportion of these are the descendents of flighted ancestors that returned to a terrestrial existence but there are also some whose ancestors never took to the skies. For most people, the most familiar of these original land-huggers are likely to be the silverfish of the family Lepismatidae.

Silverfish are long-bodied insects with a covering of reflective scales—hence the 'silver' part of their name. The 'fish' part probably refers to the manner of their movement; speaking from my own experience collecting them, these buggers move fast, slipping along the ground like a silver minnow. There are over 250 known species of Lepismatidae (Mendes 2002); probably many more remain to be described. They comprise over half the known species of the insect order Zygentoma (sometimes referred to as the Thysanura though most current entomologists tend to avoid that name due to its previous history referring to a now-obsolete grouping of the Zygentoma with the superficially similar Archaeognatha); the other families in the order are commonly subterranean and less commonly encountered by the average person. The highest diversity of silverfish occurs in tropical and subtropical parts of the world, particularly in arid or semi-arid regions. Adaptations of the rectal epithelium allow silverfish to absorb moisture straight from the atmosphere (or, to put it another way, they drink through their butt), making them ideally suited to tolerating the dryness of deserts. They are also suited to tolerating the relatively dry habitats offered by the interiors of human houses and several species have become our associates (in cooler parts of the world, these synathropic species are often the only lepismatids around). These include the common silverfish Lepisma saccharina and the giant silverfish Ctenolepisma longicaudata. The firebrat Thermobia domestica is a colourfully patterned human associate that likes it particularly warm; it is usually restricted to places like the backs of stoves or alongside hot-water cylinders where it can find the heat it craves. Being detritivores (that is, they feed on dust), human-associated silverfish are usually quite innocuous though they may cause problems if their numbers get too high or if they get into stored foodstuffs.

Firebrat Thermobia domestica, copyright David R. Madison.

In areas where they are native, silverfish may be quite diverse. Watson & Irish (1998) conducted a study of an area of the Namib Desert that was home to eight different species of silverfish. They found a tendency for the species to differ in their preferred microhabitat within the area: some were restricted to the upper parts of the sand dunes dominating the region, others were restricted to the rocky hollows separating the dunes. Those found in rocky lower zones resembled the familiar human-associated species (indeed, they included members of the same genus as the giant silverfish, Ctenolepisma) in being elongate and slender. In contrast, those species found higher in the dunes themselves were shorter and more flattened with well-developed spines covering the legs. These features allowed the dune silverfish to effectively 'swim' through the sand, using the spines on the legs to dig about and their flattened form to slip between grains.

Mendes, L. F. 2002. Taxonomy of Zygentoma and Microcoryphia: historical overview, present status and goals for the new millennium. Pedobiologia 46: 225–233.

Watson, R. T., & J. Irish. 1998. An introduction to the Lepismatidae (Thysanura: Insecta) of the Namib Desert sand dunes. Madoqua 15 (4): 285–293.

Forams with Teeth

Time for another foram post. The above image (copyright Robert P. Speijer, scale bar = 100 µm) shows Turrilina brevispira, a typical Eocene representative of the foram subfamily Turrilininae.

The Turrilininae are a group of calcareous forams that first appeared in Middle Jurassic (Loeblich & Tappan 1964). In most species, the test is what is called a 'high trochospiral' form: that is, it coils in a similar manner to, and overall looks rather like, a high-shelled snail. Each of these whorls is divided into at least three successive chambers, sometimes more. At the end of the test is a loop-shaped aperture. At least one species of turrilinine, Floresina amphiphaga, is a predator/parasite of other forams, drilling into their test to extract their protoplasm.

The turrilinines are most commonly classified in a broader foram superfamily known as the Buliminoidea or Bulimnacea. Other buliminoids commonly resemble turrilinines in their overall form. The group has commonly been defined, however, on the basis of what is called a 'tooth-plate'. This is an outgrowth of the internal wall of the test that runs between the apertures of each chamber. The exact appearance of the tooth-plate differs between taxa; in Turrilina, for instance, it is a trough-shaped pillar that is usually serrated along one end (Revets 1987). I have no idea what the function of the tooth-plate is, if indeed any is known, whether it provides an anchor for some cytoplasmic structure or anything else. However, in more recent decades a number of authors have questioned whether the tooth-plate is as significant a taxonomic feature as previously thought. For instance, Tosaia is a Recent genus of foram whose overall morphology and chamber arrangement is fairly typical for the Turrilininae but which lacks any sign of a tooth-plate (Nomura 1985). Excluding Tosaia from the buliminoids on this basis alone would imply a remarkably strong evolutionary convergence of every other feature of this genus.


Loeblich, A. R., Jr & H. Tappan. 1964. Treatise on Invertebrate Paleontology pt C. Protista 2. Sarcodina, chiefly "thecamoebians" and Foraminiferida vol. 2. The Geological Society of America and the University of Kansas Press.

Nomura, R. 1985. On the genus Tosaia (Foraminiferida) and its suprageneric classification. Journal of Paleontology 59 (1): 222–225.

Revets, S. A. 1987. A revision of the genus Turrilina Andreae, 1884. Journal of Foraminiferal Research 17 (4): 321–332.