Tag Archives: review

Liguus book

Just received the new book on the genus Liguus by González et al. A contribution that put some weight (3.4 kg to be precise) and size (4 cm on your bookshelves) to the subject.

Gonzalez 2018 Liguus_Title

Leafing through the book with much attention I noticed the following which will also form my review:

This book is the third book on land snails of the first author and the second one which is confined to one genus, the previous books entirely confined to Cuban species. For this book on the Orthalicidae tree snail genus Liguus distributed from Hispaniola to Florida, Adrián González joined forces with Pete Krull and Luiz Lajonchere; the latter has published on this genus before. The book has 10 chapters on historical studies, collections, palaeogeography, taxonomy of the Cuban, Floridan respectively Hispaniolan (sub)species and colour forms, biology and ecology, and finally conservation issues. On the enclosed CD appendices to several chapters and the bibliography is found. There are 161 (unnumbered) plates of Liguus colour forms and hundreds of colour photos of live snails. 

Liguus tree snails have catched the eye of shell collectors and artists since the beginning of the 17th century till today. They have many different colour patterns and hybridisation between several colour forms does occur, as well as gigantism and dwarfism. The result is an astonishing number of names for them, either officially or unofficially introduced which can be found in both museum and private collections. The book starts with a disclaimer “not deemed to be valid for the purpose of formal taxonomic nomenclature”. Although this seems a justified action, it is perhaps also a too modest action once one realises that 161 names are available for Liguus taxa (Appendix 11), plus several unofficial varieties and a bunch of manuscript names. The authors have neatly streamlined this horrendous chaos into five species (including Liguus flamellus and L. blainianus; if the biological species concept is applied only three remain: Liguus fasciatus, L. virgineus, L. vittatus). The core of the book is thus the two taxonomic parts (Chapters 4 and 5: pp. 63-279 for Cuban taxa, and Chapters 7 and 8: pp. 304-421 for respectively Floridan and Hispaniolan taxa), in which the species, their subspecies and lineages are treated by giving for each the original publication, the type locality, the description, their distribution and concluded by remarks. Especially the many Cuban taxa have not always been properly figured, and the authors have done much effort to search for these specimens and photograph them to modern standards. Almost each is beautifully illustrated on the plates which show 24 shells each, grouped in four rows. On several pages (pp. 73-74, 132, 198, 265, 304, 345, 411-412) maps are given that help to understand how the subspecies and lineages are distributed. Several interspersed plates illustrate the living specimens of one or more morphs.

Gonzalez 2018 Liguus_Shells

Gonzalez 2018 Liguus_Maps

The introductory chapters 2 and 3 present historical data, including iconography and collecting information. Many historical photos are included, and I spotted some that I have not seen before. A brief chapter 4 presents the geological background needed to understand current distribution. Chapter 6 bridges both taxonomical parts and treats a question that several scientists have been struggling with: the connection between Cuban and Florida Liguus taxa. Although many unanswered questions remain, the authors suggest that Liguus baby shells were carried on the wind of hurricanes from Cuba to Florida. They also suggested that these were relatively recent (geologically speaking) events. Of course, these and other questions needs further confirmation and future molecular studies may hopefully at least partially solve them. The final two chapters (9 and 10) are devoted to the biology, ecology and conservation of these snails. In the first one data are compiled among others about life span, population density, predation, host plants and trees. The last chapter treats habitat destruction, introduced predators, protection regulations and laws, protected areas and some suggestions for further conservation.

Gonzalez 2018 Liguus_Appendices

The appendices have been stored on an accompanying CD, which when I inserted it in my system appeared to contain one rar-file. After decompressing a pdf-file of similar size was shown, which raises the question why it was compressed anyway. The file has several appendices showing supplementary information, e.g., historical collecting field trips by U.S.A. malacologists to Cuba, the dispute of the holotype and ‘type’ locality of Liguus fasciatus, collectors mentioned on labels of Cuban Liguus shells, manuscript names and their current status, a list of available names, and additional ecological, anatomical, and conservation data. Together these form the first 58 pages. The final 30 pages are bibliographical references, a huge list in small print.

The authors justified write in the introduction “there has never been of book about Liguus that included every named form from the Cuban archipelago, peninsular Florida, and the island of Hispaniola”. In fact they have made a revision of the genus which is easily readable for non-scientists and, together with the many high-quality photographs, have done an amazing job. Are there no critical remarks to be made? Yes, but only a few. The plates are unnumbered and therefore no link is made between the text and the illustrations. Also no index has been provided which would  have helped to locate easily both the scientific names and person names in the book and appendices. Both points make the book less useful as a reference work. While the authors say “word can fly but writings remain” (p. 497), they would have done better to replace the CD (soon outdated) with a more permanent alternative; the information in the appendices is too important to have it not available.

My overall impression is that this work will be seen as a hallmark for the decades to come. The book will serve both amateurs and professionals and should not be lacking in any relevant library. 

Reference:
González-Guillén, A., Krull, F. & Lajonchere-Ponce de Leon, L.A., 2018. Liguus. The flamboyant tree snails: 1-498 + 88 pages on accompanying CD. F. Krull, 132 1st ST. E #105, Tierra Verde, FL 33715, U.S.A. ISBN 978 0 9847140 5 6. Price US $ 189.90 net (hardcover).

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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.

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

Review of part of Hispaniolan Annulariidae

The third post on Watters’ 2016 papers concerns his review of the Paracondria (Chondropomorus) complex. “Nineteen species are recognized including eight new species: Parachondria anatolensis n. sp., Parachondria arcisensis n. sp., Parachondria daedalus n. sp., Para- chondria heatheraikenae n. sp., Parachondria isabellinus n. sp., Parachondria muchai n. sp., Parachondria silvaticus n. sp., and Parachondria stigmosus n. sp. Distributional and habitat notes are given for additional taxa. Chondropoma marinum “Weinland” Reeve, 1863, is regarded as a nomen dubium. Chondropoma (Chondropomorus) moroni Bartsch, 1946, is reidentified as Crossepoma emilianum (Weinland, 1862). Chondropoma simplex Pfeiffer, 1852, regarded by Bartsch (1946) as a Chondropomorus, is considered a Chondropoma”.

schermafbeelding-2017-02-08-om-08-29-34 schermafbeelding-2017-02-08-om-08-30-03

Reference:
Watters, G.J., 2016. Review of the Hispaniolan Parachondria (Chondropomorus) complex (Gastropoda: Littorinoidea: Annulariidae). – Zootaxa, 4127 (2): 245–275.

Diversity of Helicinidae

Although already presented at the “Magnitude of molluscan diversity – the known and the unknown” Symposium held at the 78th meeting of the American Malacological
Society (2012), Ira Richling’s excellent paper on diversity of the Helicinidae was recently published (Richling, 2014).

Richling2014f2

Presenting a history of helicinid research starting in 1801 (the first taxon described was a Jamaican species), she has analysed the development of the diversity through time and also a number of revisions to compare the number of accepted (sub)species to available names. Under ‘Drawbacks in exploration’ several aspects (listed below in the abstract) are extensively discussed, which have an importance beyond the scope of the paper.

It would be interesting to explore these issues for other (large) land snail families in the (Neo)tropics. One of these issues is the “limited availability of wet preserved material”, which is quite crucial to make advances both in morphological and molecular studies. Unfortunately, the forthcoming implementation of the Nagoya Protocol (cf. Renner et al., 2012) makes things probably worse and opens up the possibilities for unwarranted claims from local scientists and license authorithies for financial expenditures, and more (examples are known of claimed co-authorship for several papers without any content contribution). Given the ongoing crisis in natural history museums, this is an avenue leading to disasters.

Richling2014f4

The full abstract of the paper reads: “Helicinids represent a family of tropical land snails with a distribution range limited to the subtropical and tropical zones of the New World, Australasia, and the Pacific. For an estimate of diversity in this poorly systematically revised group, the total number of described taxa was determined and used for calculations based on analyses of selected case studies with regard to the percentage of valid and new taxa.
Extensive bibliographic searches identified about 1,250 available names, regardless of rank, that were described from 1801 onward. Fiftyeight percent of the names represent New World taxa whose majority (63%) was created before 1880 while the intensive study in most of the
Australasian and Pacific areas started much later with the bulk of taxa described between 1880–1930. An analysis of the distribution of the type localities and the times of descriptions allowed for identification of scarcely- and well-studied areas.
Eight potentially representative case studies of major revisions were compared with respect to changes in described versus “true” diversity. The geographic range covered Costa Rica, Cuba, Jamaica, Lesser Antilles, New Caledonia, northeast Australia, and the Hawaiian and Gambier
Islands. In these studies approximately half of the available names were regarded as synonyms (range from 37 to 72%). On the other hand, 36 to 41% of the recognized diversity represented new species depending on whether a more lumping or splitting approach was considered, the
latter simulated by simply counting subspecies as equal units of diversity. The amount of new taxa ranged from 2% (Cuba) to 90% (Gambier Islands). Under the assumption that six of the studies were representative throughout the area of distribution, worldwide diversity would
range from 770 to 1,140 species or up to 1,400 species if the studies from the Australasian-Pacifi c area were realistic. Although obviously poorly studied, in comparison with an estimate for all continental molluscs of Mexico and Central America by Thompson (2011), helicinids
would still be among the better documented snail families for this region.
The following aspects and their consequences are discussed as most significant drawbacks in the exploration of helicinids: questionable systematic concepts above species level; limited recognized differentiating characters and convergence; species complexes and last, massive
habitat loss, increasingly fragmented distribution and extinction. Another practical aspect is the rather limited availability of wet preserved material”.

References:
Renner, S.C. et al., 2012. Import and export of biological samples from tropical countries—considerations and guidelines for research teams. – Organisms, Diversity & Evolution 12: 81–98.
Richling, I., 2014. Poorly explored jewels of the tropics: Estimating diversity in non-pulmonate land snails of the family Helicinidae (Gastropoda: Neritopsina). – American Malacological Bulletin 32: 246–258.