These shells are probably B. holostoma (Pfeiffer, 1846), described from Cobija. The specimens collected by Richards were found north of Caldera, under rocks near the sea. Although not explicitly stated on the label, this sounds like a locality with lomas vegetation.
Rehder (1945) already stated that this species “has a short but strong columellar lamella within the last whorl”. The shell pictured above shows the same characteristic.
Rehder, H.A., 1945. The Chilean species of the molluscan genus Peronaeus (Bulimulidae) - Revista Chilena de Historia Natural 48: 102-107.
Meanwhile I ascertained that these specimens are B. leucostictus (Philippi, 1856), a closely related species described from Paposo.
The abstract of his presentation was:
Land snails are important organisms
to understand biogeographical changes in different
regions. Their low dispersion ability produces a
particular population structure that resembles
historical patterns of genetic diversity. I compared
genetic patterns in two different species:
scalariformis (Orthalicidae) from the coast of
Peru and Systrophia
helicycloides (Scolodontidae) from the western
Amazonian basin. Both species presented a high
mutation rate in their mitochondrial genome and also
a high intraspecific divergence.
B. scalariformis shows two different lineages which correspond to its different morphotypes. El Niño Southern Oscillation ant the coastal desert could have played a key role in the modeling of the genetic structure in this land snail. On the other hand, S. helicycloides shows lineages with widely distributed and also restricted haplotypes. The actual genetic structure in S. helicycloides seems to be influenced by historical geoclimatic changes, like the rise of the Andes or Pleistocene refuges that both may have produced lineage differentiation. In this case, actual river dynamics could be influential on the distribution of the genetic diversity.
According to Romero, the
populations of Bostryx
are influenced by the
El Nino cycles and their influence on the expanding
and contracting ‘lomas’ vegetation islands in the
coastal desert. On the contrary, the
populations seem to
have been mixed under the influence of the river
dynamics in the Madre de Dios region.
From above left, clockwise: central teeth, interactie rows, detail 4th lateromarginal, 12-13th lateromarginal.
Today the species is Bostryx anomphalus Pilsbry 1944, occurring in Peru, near Lima. in the Rio Rimac and R. Santa Eulalia valleys.
From left to right, clockwise: Central teeth, first and second laterals, interactions between rows and detail of teeth 19.
The radular formula is C/3 + LM 22/2.
Valentín Mogollón sent me some pictures that he took of living specimens during a recent trip to that area. One in the natural habitat, another in the lab on the move (both pictures are enlarged).
You can see that the animal is rather translucent, with the black optical nerves shining through the body. One could wonder what the evolutionary benefit would be?
Recently, a paper was published by a Peruvian group (Ramirez et al., 2009). It describes an analysis of three species of the Orthalicidae, Bostryx scalariformis, B. sordidus and Scutalus versicolor, based on the 16S rRNA mitochondrial marker. Currently, only similar data are available on Placostylus bivaricosus. So, this paper is very useful in adding species of two more genera.
Both the tree in Neighbour-Joining (left) as Maximum Parsimony (right), and the analyses using Maximum Likelihood and Bayesian Inference (not shown here), show the orthalicoid genera as a closely related group.
Most data in GenBank are on other regions of the gene, notably CO1. Barcoding “species” becomes ‘en vogue’, but on the Taxacom list the following remark by Bob Mesibov was noted:
“I urge Taxacomers to read Roger Hyam's blog
(http://www.hyam.net/blog/archives/598) in full, but here's an
"Up to now the assumption has been that we are discovering taxa in
nature and then attempting to describe them. It is undoubtedly true that
taxa do exist in nature. However, in order to construct a usable map of
biodiversity, we need to turn this on its head. It is the act of minting
an identifier and linking it to a circumscription that creates the
taxon. We then discover which specimens in the wild fit into this taxon.
Philosophically this his how we act anyway (see Identifiers, Identity
and Me). Taxa are currently hypotheses (things we invent) that may break
down as our knowledge grows."
Much of the Taxacom discussion so far has been about species
identification, because species identification is what barcoding
promises. But Hyam says 'taxon'. Re-read the paragraph above
substituting 'genus' or 'family' for 'taxon'. Still OK? (That is, if you
thought the paragraph was OK when 'taxon' meant 'species'.) Note also
that barcodes could also theoretically be used to predefine taxa higher
than species, by relaxing the sequence requirements in ways indicated by
species sampling within the higher taxon.
Now, what strikes me as strange and wonderful is that OTTH I'm perfectly
happy with Hyam's approach when thinking about genera and families,
which are constructs with a lower-grade 'existence in nature' than
species. In fact, this is how I think genera and families get built into
classifications, traditionally. It's certainly how I go about erecting
new genera for my beloved millipedes
But OTOH, Hyam's approach just doesn't click with me when I think about
circumscribing new species. Not already recognised species, of the kind
we identify a la the Taxacom discussion, but previously unrecognised
species. Like, most of the world's species?
If I read Hyam correctly, his circumscription of new species, just like
that of old species, is by means of a barcode. Quick, simple and
unambiguous (caveats, caveats), this approach *replaces* morphospecies
with barcodes. The option of linking Hyam's Barcode Taxa to
morphospecies data (with keys, diagnoses, images, etc) is just that, an
option - to create 'secondary taxonomic products' (Hyam's phrase) or
So you could produce a 'map of biodiversity' by barcoding madly on a
field trip and recognising - excuse me, defining - heaps of new species.
Think of that as step 1. Steps 2, 3, etc would be learning the answers
to questions like 'How big is it?', 'What life stage?', 'Male or
female?', 'Associated with what [plant/animal]?'. Lotta work there, but
that would certainly make the 'map of biodiversity' more usable. Take
biological control, for example. Don't know how far I could get with
'GenBank RQ561336 a possible parasite of GenBank AE699133', but it would
be a real comfort to know that these entities had been rigorously
circumscribed right from the beginning.”
Personally, I prefer a sound morphological hypothesis to start with. Any barcoding may then falsify or corroborating the hypothesis. Not vice-versa.
Ramirez, J., Ramirez, R., Romero, P., Chumbe, A. & Ramirez, P., 2009. Posición evolutiva de caracoles terrestres peruanos (Orthalicidae) entre los Stylommatophora (Mollusca: Gastropoda). - Revista Peruana de Biologia 16: 51-56.
The type locality of Bostryx primigenius sp.n. is El Infernillo, the pass through which both the highway and the train to La Oroya passes.
There is a gradual transition to the next species in a hybrid zone near Tambo de Viso, which is the type locality of Bostryx multiconspectus sp.n.
So far, it remains unknown what drives the peculiar transition and the carinated shape at this locality. “Ecological stress”, as suggested by Craig? Or some other mechanism? And what is the evolutionary advantage? Questions that remain to be solved...
Breure, A.S.H., 2008. Carination strikes the eye: extreme shell shapes and sibling species in three Andean genera of the Orthalicidae (Gastropoda, Stylommatophora). - Zoologische Mededelingen 82: 499-514.
The first is a species of Bostryx, found near Coquimbo, Punta de Choros. It is hard to say what species precisely, because only this dorso-lateral view is available. Judging from the shell shape and the records from literature, one possibility is B. rouaulti (Hupe, 1857).
All others are Plectostylus. From the same locality is P. coquimbensis (Broderip, 1832).
The next one is from an unknown locality. It resembles P. variegatus (Pfeiffer, 1842) but, again, with only this information it is hard to be conclusive.
Again, no data on the next picture, but clearly a different species judging from the animal alone; the orange neck-stripe and rim along the foot is characteristic. If I have to make a guess, it could be P. peruvianus (Bruguière, 1789).
This looks like the same species...
Another, clearly distinct species. It looks like the photograph was taken in a more wooded part of the country. Supposing this is a more southern species, possibly P. vagabondiae Brooks, 1936 (?).
And these cristal balls are eggs of an unknown Plectostylus species, ready to hatch.
The latter publication is a synopsis of the land snails, for which detailed catalogues and group analyses were announced “to be published by parts elsewhere”. A far as I know, only a revision of Plectostylus appeared (Valdovinos & Stuardo, 1988).
As is also the case in other countries, the Orthalicidae are a major element of the Chilean terrestrial malacofauna. 42 taxa are listed, one doubtfully recorded for Chile (belonging to Thaumastus); the others all belong to Bostryx and Plectostylus.
While the latter genus has been largely revised, Bostryx remains quite ‘messy’ with 29 taxa. All species occur in northern Chile and seem to flourish in the desertic coastal area. An overview of the Chilean Orthalicidae can be found here.
I find deserts always interesting, providing ample niche habitats for snails ‘living on the edge’. Whether these circumstances constitute ‘ecological stress’ leading to peculiar shell shapes or not remains an open question for me (as discussed in this post). Certainly it forms a ‘playground’ for genetical research.
Stuardo, J. & Valdovinos, C., 1985. A synonimic list of Chilean bulimulids (Mollusca: Pulmonata). - Boletin Sociedad Biologia Concepcion 56: 55-58.
Stuardo, J. & Vega, R., 1985. Synopsis of the land Mollusca of Chile, with remark on distributions. - Studies on Neotropical Fauna and Environment 20: 125-146.
Valdovinos, C. & Stuardo, J., 1988. Morfología, sistematica y distribución del género Plectostylus Beck, 1837 (Pulmonata: Bulimulidae). - Gayana, Zoologia 52: 115-195.
In 1970, the paleontologist Herm described a new species, Bostryx variabilis, from Pleistocene marine sediments near Antofagasta.
Map showing the area just north of Antafagasta (from Herm, 1970)
To explain the occurrence of this terrestrial species amidst marine facies, he postulated a sea level regression-transgression. The species is carinated (keeled) and partially uncoiled.
In 1981, Alan Craig -a geographer- did field work in the same region and made some observations which questioned Herm’s hypothesis. He found many specimens of B. variabilis in nearby localitions, but they were restricted to places where also fossilized lichens occurred. Moreover he found transitions to a Recent species, B. mejillonensis (Pfeiffer, 1857).
Isotopic dating yielded an age of 2180 +/- 50 yr B.P., making the Pleistocene sea level change as postulated by Herm unnecessary for the type locality.
But how to explain the occurrence of B. mejillonensis-variabilis at this place? Eventually it appeared that Bostryx mejillonensis was only found in localities where meteorological circumstances sustained epiphytic colonies of lichens on cacti at the top of a hill nearby the type locality of Herm. At the slopes below the elevation where the seasonal fog banks have influence, the hyperarid desert constitutes a barrier for the dispersal of snails. The hill top thus forms an ecological island. This finally led Craig to hypothesize that B. mejillonensis had been forced outside their habitat into the surrounding desert from where they were unable to escape. Rapid changing environmental conditions would have ‘stress-induced’ a speciation process which led to the aberrant form of B. variabilis. Support for this hypothesis were field observations by Craig of runnels, caused by occasional winter rains, leading to downslope transportation of snails.
Area just north of Antafagasta with the localities mentioned by Herm (1970) and Craig (1985) indicated. The distribution area of lichens indicated by Craig marked on Morro Moreno in white (source: Google Earth).
Given the hypothesis briefly outlined above, my question is: is carination as observed in other places (e.g., here and here) also best explained as a ‘stress-induced speciation process’? If so, are there analogous ecological circumstances that force snails to transform into aberrant, carinated and -sometimes even - uncoiled shells?
Craig, A.K., 1985. Speciation and age revision of the Atacaman snail Bostryx variabilis Herm. - Quarternary Research 23: 382-387.
Herm, D., 1970. Bostryx variabilis n.sp., eine Landschnecke aus dem Altpleistozän von Mejillones, Nordchile. - Mittheilungen Bayerischen Staatssammlung Paläontologie und historische Geologie 10: 189-198.
Luckily, the site mentioned also who had collected the specimens. I decided to contact the collector, a befriended couple who have travelled a lot in Latin America and whose collecting data are always very precise and trustworthy. To my surprise, the answer I got was only partly corroborating. The locality was right but the habitat not! Instead collected on rocks, the specimens had been found as subfossils in a desert-like area. Quite a difference and not without importance.
So, the lesson I learned here is: if you can, always consult the original source.
Many of these tank bromeliads live in montane (cloud) forest where they can usually be found in the canopy. Out of reach of the "normal" biologist, as you need to climb high if you want to make observations. Yet they are known habitats for insects, frogs, epigeic earthworms, ostracods and also are a foraging site for birds.
Snails have also been associated with bromeliads. Basically there are two groups: one on Tillandsia sp. and one on (probably) other tank bromeliad genera. The first groups concerns Bostryx species from Peru, e.g. B. bromeliarum (Pilsbry, 1930) and the B. spiculatus-group.
The second group comprises Simpulopsis species, and although most have been described without mentioning of their habitat, given their locations and the association with bromeliads of some of them, I have a strong suspicion that several species might be associated with tank bromeliads. We know at least that S. simulus (Morelet, 1851) and S. magnus Thompson, 1957 have been found in bromeliads. The same might be true for S. corrugatus Guppy, 1866 from Trinidad and several species reported from the east coast of Brazil (Atlantic Forest, or what is left of it).
Enough of this rambling on bromeliads and snails... What about the beetles?
Merely by chance I stumbled upon the recent paper by Balke et al.* on the association between aquatic beetles and tank bromeliads. They studied a group of beetles that occurs in small water bodies in tropical forests, but a small subset of them is specialized to the water reservoirs of tank bromeliads. Extensive phylogenetic work revealed that the origin of one of the lineages was estimated to be comparable to that of the tank bromeliads. The other two lineages that are associated with these plants are thought to be more recent expansions into the tank water habitat.
The evolution of these canopy communities is far from being understood and leaves several areas open for further research. Snails being but one of them.
Balke, M., Gómez-Zurita, J., Ribera, I., Vilora, A., Zillikens, A., Steiner, J., García, M, Hendrich, L. & Vogler, A.P. (2008). Ancient associations of aquatic beeles and tank bromeliads in the Neotropical forest canopy. Proceedings of the National Academy of Sciences of the United States of America, 105, 6356-6361.
The habitat were here found them is also interesting, although doesn't look spectacular albeit scenic. Interesting, however, is the fact that it is part of a larger system of small interandean valleys, with a dry climate but occasionally flooded after rains.
Such localities often harbour endemic species and are dry pockets in an otherwise more humid environment. I remember having found similar conditions in Colombia, where Naesiotus gerenorum (Breure, 1977) and N. jullensorum (Breure, 1977) were collected in Dept. Boyacá, near Soatá.
One of the topics with progress was the Peruvian Bostryx. I wrote before on the material of Weyrauch and, although his localities are usually rather precise, I feel a bit stuck on the Rio Rimac valley material, by lack of adequate collecting data. Not only is it important to have precise localities (in this case very precise), I would recommend every collector to make additional field notes on habitat (occurrence on vertical or horizontal faces*) and other ecological data. Since all possible notes have been destroyed after his death by his ignorant spouse, we will never know where Weyrauch collected some of his material and in which habitats.
On the contrary, e.g. are the very adequate data supplied by Fred Thompson. During all his collecting trips he made extensive notes on habitats, soils and circumstances. I used some of them in a paper on enigmatic species (to be published) and in forthcoming papers on Venezuela and Hispaniola.
That being the positive side on the coin, there is also some negative news. My applications for the Synthesys programma, viz. to study type material in London, Berlin and Stockholm, have all been rejected. While decision making was separate for each museum, they have in common that it has been a nearly complete 'black box'. In London there were nearly 200 applications, which made competition stiff. The Berlin committee argued that my last publication was in the 1980s, simply ignoring my recent Zootaxa paper... Perhaps I have been just too long "out" to be able to do relevant research?
Botryx granulatus WeyrauchMS
As Weyrauch has shown*, several species are highly variable and show decollate whorls (e.g. Bostryx imeldae, B. zilchi both from Laraos), a phenomenon also observed in the valley of Rio Rimac.
But even when snails go less 'wild' it may become interesting, as shown by this series of shells, from two localities in the Rio Cañete valley at 2200 resp. 3300 m altitude:
Are these four different taxa (labelled as such by Weyrauch) or merely variations within one species? To what extent plays one's stand on the continuum 'splitter' versus 'lumper' a role?
Anyway, my final verdict is that these shells all belong to the same species (and a hitherto undescribed one). But indeed, it would be very interesting to be able to visit this 'living laboratory' again and investigate the biological processes behind all these shells and genes 'going wild'.
Weyrauch, W.K. (1958) Neue Landschnecken und neue Synonyme aus Südamerika, 1. Archiv für Molluskenkunde 87: 91-139.
Weyrauch, W.K. (1960) Siebzehn neue Landschnecken aus Peru. Archiv für Molluskenkunde 89: 117-132.
While in 1979* I needed some 20 species to depict this variation, in the material collected by Weyrauch I found specimens from one locality covering nearly the whole range.
Imagine that the elongated shell in the right-hand upper corner gradually becomes the lower shell through a transitional series. That is not only taxonomically relevant to observe (found apart one would call these shells separate species), but raises a number of other questions as well. What is the genetical mechanism behind this phenomenon? Are there any ecological differences?
This is apparently the material to which Weyrauch referred in his 1956 paper*: "As I will illustrate in a later paper [which he never published], the variation in a population of a new subspecies of Bostryx eremothauma (Pilsbry) comprises all forms hitherto placed in the polyphyletic 'shape-types' of Peronaeus, Ataxus, Lissoacme, Platybostryx and Discobostryx [at the time that Weyrauch wrote this, these were all considered as subgenera of Bostryx; now synonyms of Bostryx sensu lato]. This great variation of shape, not observed in any other species of land shells, agress with the still greater diversification of shapes in different species of the genus Bostryx. This is evidently due to the young age of this genus". As I recently pointed out here, it is very well possible that in some places the speciation processes is in full progress. The Rio Rimac valley, where also the specimens were collected shown above, is definitely a place of special interest to any malacologist.
Incidentally, I came across a recent paper of Cook* mentioning that high-spired shells tend to be active on vertical surfaces, while low-spired species use horizontal substrates. Differences in shape are associated with microhabitats, which would suggest that the specimens shown here have different niches within the same locality. Unfortunately the museum labels don't tell us anything about it. For me it is one of the reasons why field work is a necessary complement to museum work and why it should be well documented.
Breure, A.S.H. (1979) Systematics, phylogeny and zoogeography of Bulimulinae (Mollusca). Zoologische Verhandelingen 168: 1-215 [The variation in Bostryx is shown on p. 47].
Cook, L. M. (2008). Species richness in Madeiran land snails, and its causes. Journal of Biogeography 35, 647-653.
Weyrauch, W.K. (1956) The genus Naesiotus, with descriptions of new species and notes on other Peruvian Bulimulidae. Proceedings of the Academy of Natural Sciences of Philadelphia 108: 1-17.
The first is that a simple geographic barrier becomes inadequate to 'explain' divergence between populations. If subtle differences in climate lead to subtle difference in vegetation, which in turn leads to different behaviour. In most cases one have to think in geological timescales to imagine how these subtle differences lead to larger differences and effective speciation comes into play.
I always wonder how these general theories work out in malacology. Just an example that puzzles me, possibly speciation still at work.
Imagine you see the shells above. The only thing you know is that they all occur in the same region, more or less at the same altitude, but at two sides of a river. I have plotted the (approximate) localities (taken from labels and collected some 40 years ago) on this map:
Now the question is, what would you call it? One species? Four subspecies? Two subspecies? I'm inclined to say the latter, but this case clearly needs further investigation. It would be nice to study these populations genetically to see to what extent the morphological differences can be explained. The only problem is: these animals occur high up in the Andes, Río Rimac valley, 3300-3400m. Any volunteers for collecting?
Patten, M. A. (2008). The intersection of specialization and speciation. J. Biogeogr, 35, 193-194.