Tag Archives: ecology

Avoiding canopy gaps

Only now a paper turned up which was already published in 2014. Bloch & Stock reported on a Puerto Rican species from the Solaropsidae related to ecological research. Unfortunately the paper is text-only…

The abstract is “Because canopy gaps are characterized by elevated temperature and decreased humidity relative to closed-canopy forest, terrestrial gastropods may be exposed to greater desiccation stress in gaps than in undisturbed forest. We placed individuals of Caracolus caracolla at the edges of canopy gaps in montane forest in Puerto Rico and observed their movements. Individuals preferentially moved out of gaps except in one gap on the first night of the study, and the proportion of individuals recaptured inside gaps decreased over time. Individuals moved, on average, farther into forest than into gaps. Juveniles and adults responded similarly. These results suggest that C. caracolla actively avoids canopy gaps, and that its activity and ability to disperse are restricted in a post-disturbance environment“.

Bloch, C.P. & Stock, M., 2014. Avoidance of Canopy Gaps by a Common Land Snail, Caracolus caracolla (L.), in Montane Forest in Puerto Rico. – Caribbean Naturalist, 8: 1-13.


Pantepui snails

Just published: a chapter on the land snails of the Venezuelan Pantepui region. It is a slightly updated summary of what was published some years ago, while in the meantime only slight progress was made.

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For the species reported hitherto from this area the taxonomy is summarised, and data on the ecology and biogeography is presented.

The rest of the book presents a lot of information on this interesting area of South America, both general and on the flora and fauna. The illustrations are plentiful and often spectacular.

Breure, A.S.H., 2019. Land snails: an updated summary: 247-261. — In: Rull, V., Vegas-Villarrúbia, T., Huber, O. & Señaris, C. (eds.) Biodiversity of Pantepui: the pristine ‘Lost World’ of the Neotropical Guayana Highlands. Academic Press, Cambridge

Ecology and conservation of Plectostylus

A recent paper by Barahona-Segovia et al. discusses the details of the ecology of a Chilean Plectostylus species. Their abstract is “Terrestrial mollusks are one of the least studied groups of terrestrial invertebrates, especially in the Neotropics. In Chile, there is scarce biological and ecological information about many genera, even though the group is quite diverse and occupies different habitats along the country. Plectostylus araucanus is the most recently described species and one of the few arboreal species found only in the coastal native forest of central-south of Chile. In this study, we recorded a new locality for P. araucanus in the del Maule Region and described ecological and physiological characteristics. The new locality is placed 204 km northwards of the type locality. Based on different records, Plectostylus araucanus is proposed as an endangered (EN) species under the distribution criterion of IUCN. Most of the specimens of P. araucanus were found living in tree cavities and away from the edge of native forest fragments. Physiological measures showed monthly differences, especially between some months of summer and fall and between months of the same season (i.e., summer). We discuss the implications of our results in the microhabitat selection, thermoregulation and habitat use by this tree snail, and the importance of this data in management and conservation for other native malacofauna”.

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This is an interesting study, as detailed ecological research on Neotropical snails is scarce and the available data gives a very partial view on the requirements of the malacofauna; the handles for conservation management are thus also extremely limited, which is a concern with the increasing threats of anthropogenic influences.

Barahona-Segovia, R.M. et al., 2019. Shelter, ecophysiology and conservation status of Plectostylus araucanus (Pulmonata: Bothriembryontidae) in the fragmented Bosque Maulino, central Chile. – Revista Mexicana de Biodiversidad, 90: e902703 (12 pp.).

Belize land snails

A new book by Dourson et al. on the non-marine malacofauna of Belize is a peculiar case, which shows that privately publishing a book including new taxa might be a tricky case.

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The non-marine malacofauna of Mexico and Central America is seemingly well-known through the work of the late Fred G. Thompson. His checklist, of which the final version appeared in 2011, listed all the currently accepted (sub)species and synonyms known from that area. It was a major milestone after the previous works by Crosse & Fischer’s Mission au Mexique et Guatemala, …Mollusques (1870-1902) and Von Martens’ molluscan part of the Biologia Centrali-Americana (1890-1901). Thompson’s publication, listing ca. 1250 taxa for this enormous area, stated that this number possibly only reflects one third of the actual malacofauna, due to the fact that most countries have only partially been surveyed for molluscs. 

Dourson et al. have concentrated on Belize, a relatively small country which borders southern Mexico and Guatemala. During the period 2006-2016 they surveyed all the seven physiographic regions of the country. And where Thompson only listed 24 species they enumerate 158 in total, of which 17 newly described in this book, with three others recently described in journals and a further eight still not formally described. This constitutes an increase of 658% for the biodiversity of non-marine snails in this country!

The authors have set up this book in such a way that it is aimed for a broad public, both scientists and laymen. After the introductory chapter, two chapters are dealing with general information on land snails and the value of snails in ecosystems respectively. The next chapter ‘Collecting and Identifying Land Snails’ also explains the organisation of the book. Chapters 5-12 treat land snails according to their shape and size, followed by a chapter on slugs and one on freshwater snails. The final chapter is dealing with exotic snails occurring in Belize. The book is concluded by a glossary, a species list per family, a bibliography, and an index of scientific names.

The first version of this book (Dourson et al., 2018a) was unintentionally published while the authors were still updating the text on the basis of reviews they had asked to specialists. Nevertheless, the book was distributed by several commercial companies, and the new species descriptions are thus validly available according to the International Code on Zoological Nomenclature. This date was 10 January 2018; the final, ‘official’ version came out just before Christmas on 21 December (Dourson et al., 2018b). 

The ‘unofficial’ first version was based on old classifications for several families (e.g., Orthalicidae contained both Orthalicus [Orthalicidae] and Bulimulus and Drymaeus [Bulimulidae]; no distinction was being made between Urocoptidae and Epirobiidae; Subulinidae were not included in Achatinidae). The classification of Ampullariidae is not in accordance with the authoritative papers of Cowie. In June 2018, after receiving a further draft of the book, I send a long list with additional comments to the authors. Thus it is regrettable that this version was published at all. Unfortunately part of the suggested corrections were not applied (e.g., p. 11: Morlet’s crocodile should be Morelet’s crocodile; p. 26: the ‘escargot’ of the French is not Cornu aspersum but Helix pomatia; p. 227: the correct name for the species is Brachypodella speluncae (L. Pfeiffer, 1852), and the syntype figured on p. 226 is Cylindrella costulata Morelet, 1851 [Pfeiffer’s name being a replacement name for this junior homonym]). Some figures have been updated and the list of references is somewhat extended but still contains typos and flaws, while recent literature on several groups are missing.

The following new species have been described (publication date thus January 2018), with the holotypes deposited in the Florida Museum of Natural History, Gainesville:

Family Helicinidae: Lucidella caldwelli
(Note that since authorship has not been restricted, Caldwell is co-author of his own eponym)

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Family Bulimulidae: Drymaeus tzubi
(N.B. in this version incorrectly classified as belonging to Orthalicidae)

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Family Spiraxidae: Euglandina fosteri

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Family Spiraxidae: Pseudosubulina juancho

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Family Spiraxidae: Rectaxis breweri

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Family Achatinidae: Opeas marlini
(N.B. in this version still under the family Subulinidae)

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Family Achatinidae: Leptopeas corwinii
(N.B. in this version still under the family Subulinidae)

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Family Achatinidae: Lamellaxis matola
(N.B. in this version still under the family Subulinidae)

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Family Achatinidae: Leptinaria doddi
(N.B. in this version still under the family Subulinidae)

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Family Urocoptidae: Brachypodella levisa

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Family Thysanophoridae: Thysanophora meermani

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Family Scolodontidae: Miradiscops striatae

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Family Scolodontidae: Miradiscops youngii

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Family Scolodontidae: Miradiscops bladensis

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Family Charopidae: Rotadiscus saqui

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Family Charopidae: Chanomphalus angelae

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Family Ferussaciidae: Cecilioides dicaprio

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This book is an extremely nice contribution to our knowledge of the Central American malacofauna. It is suitable both for both the ‘serious’ malacologist and for a layman, thanks to the very accessible way the book was designed. But, as the authors communicated to me, the prime audience is the general public. The lay-out will appeal to this target group, although the silly cartoons could be missed without making the book less informative.

As far as I know, the authors are now giving workshops to people in Belize to bring this fauna more to their attention. They will also develop a laminated snail card for quick identifications in the field. All this sounds as wonderful initiatives.

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Update: The final version of the book came meanwhile available, and this post has been updated. It is unfortunate that the authors have not grasped the opportunity to correct some of the errors in Thompson’s checklist and that the classification is not up-to-date. It is clear that the first, unofficial version will become a collector’s item for bibliophiles!

Dourson, D.C., Caldwell, R.S. & Dourson, J.A., 2018a. Land snails of Belize, Central America. A chronicle of remarkable diversity and function. — Goatslug Publications, Stanton, Kentucky, U.S.A. Hardcover, 338 pp. ISBN 978 0999 802304. [no longer available]

Dourson, D.C., Caldwell, R.S. & Dourson, J.A., 2018b. Land snails of Belize, Central America. A chronicle of remarkable diversity and function. — Goatslug Publications, Stanton, Kentucky, U.S.A. Softcover, 339 pp. ISBN 978 0999 802311. € 69. 

Physical defense strategies

Predators play of course an important role in the ecology of snails, and various groups have developed their own strategy during the evolutionary process to try to fence off their enemies. Simone just published an overview of these strategies in South American land snails in a new (privately run) digital journal, which he called ‘Malacopedia’.

Unfortunately, the website of the journal seems out of order, so I cannot provide a direct link to the paper.

In his paper he discusses apertural barriers, changes in the direction of shell growth, hyper-coiling of the shell, hyper-retraction of the animal, alterations of size, and sinistral coiling.

This review seems to me a useful start, as the topic has been treated in literature mainly regarding marine and freshwater species. The ecology, biology and life cycle aspects of land snails have received comparatively little attention, and further studies on this topic may be interesting. Especially when they are not limited to the Neotropical realm only.

Simone, L.R.L., 2018. Physical defence strategies of South American land snails. – Malacopedia, 1: 3-11.

Snails and forest relicts in Chile

Freshly pressed: a paper by Francisco Cádiz and co-authors describing how they used land snails to decipher the origin and isolation in forest relicts in northern Chile.

The abstract reads: “Among the questions surrounding the biogeographical history of the Chilean biota, none has gathered more interest than the origin of the Fray Jorge (FJ) for- est relict and its biota. Inserted in a semi‐desert area, this forest enclave exists due to the existence of a very particular microclimate in this region. The age of the disjunction and the historical relationship between the FJ biota with the remaining components of South America are explained by two distinct, competing hypotheses: the first suggests that it would have become isolated during the climatic changes of the Paleogene/Neogene, while the second suggests that the isolation is a product of Quaternary glaciations. To discriminate between these competing hypotheses, we used DNA sequence phylogeny methods and molecular genetic dating to the study of a genus of land snails (Plectostylus) that occurs in the FJ relict and throughout Chile. The phylogeny shows a clear distinction between forest and arid clades, and each of these clades is formed by many geographically circumscribed populations. The FJ fragment snails form a clade that is sister to all other forest clades. The separation between the Fray Jorge clade and the other forest clades dates back to the Paleogene/Neogene. Our data suggest that the FJ forest is a relict from the forests that occupied that landscape during the Paleogene/Neogene and retreated due to the aridification of the region. We also observe that the current taxonomy of the Plectostylus genus must be re‐evaluated”.

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An interesting paper that uses molecular data of an endemic land snail group to sort out competing hypotheses of ancient landscape genesis. More often, ecological data are used to support a hypothesis of the taxonomy of species; this time it is the other way around. While working on this study the authors also collected data on the taxonomy of this group, but this will be dealt with in a future paper.

Cádiz, F.J. et al., 2018. Phylogeography of Plectostylus Beck, 1837 (Gastropoda, Stylommatophora: Orthalicoidea): Origin and isolation of the Fray Jorge forest relicts in northern Chile. – Journal of Zoological Systematics and Evolutionary Research, doi: 10.1111/jzs.12241 (10 pp.) (advance publication).

Cuban Callonia

The family Urocoptidae is very species-rich in Cuba, and the genus Callonia is but a small representative of this family, albeit very aesthetically. González-Guillén et al. (2017) just published a paper on this group.

Specimens of all western Cuban species of Callonia are illustrated, together with images of live animals and their habitat, followed by comments about recent field work. The putative relationships among species based on the morphological characteristics of last whorl soluteness and rib shape-orientation could be biased. Seemingly ecologic equivalent pairs C.loweiC.dautzenbergiana and C.elliottiC.gemmata are much alike in external appearance although genetic similarities, which have not yet been assessed, could be higher between species sharing the same range. A co-occurrence of Callonia snails with blackish lichen is discussed, raising the inference that Callonia use lichens as food source”.

These ecological observations are worth to be further explored. The putative hypothesis about the relations between the Callonia species can only be verified with molecular analysis.

Many thanks to Gijs Kronenberg for sharing this interesting paper.

González-Guillén et al., 2017. Insights on the genus Callonia (Mollusca: Urocoptidae) from Western Cuba. – The Festivus, 49 (4): 332-338.