The Changing Trinidad and Tobago Herpetofauna John C
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The Changing Trinidad and Tobago Herpetofauna John C. Murphy and Roger Downie Murphy, J.C., and Downie, R. 2012. The Changing Trinidad and Tobago Herpetofauna. Living World, Journal of The Trinidad and Tobago Field Naturalists’ Club , 2012, 87-95. The Changing Trinidad and Tobago Herpetofauna John C. Murphy1 and J. Roger Downie2 1. Division of Amphibians and Reptiles, Field Museum of Natural History, 1400 S. Lake Shore Drive, Chicago, IL 60605 USA. [email protected] 2. School of Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK. [email protected] ABSTRACT The Trinidad and Tobago herpetofauna is rich in species and the numbers of recognised species on the islands are expected to grow despite the extensive efforts previously made to study the fauna. Recent advances in molecular tech- nology and cladistics form the basis for these changes. Cryptic species have been found to be �uite common and many of these remain to be described from the islands. Here we note name changes and additions to the herpetofauna since 1997, comment on the likelihood that the island still contains species that have gone unrecognized by science; discuss the implications of cryptic species for conservation efforts; and suggest that education is the long-term solution to retain- ing the biodiversity of Trinidad and Tobago. Key words: cryptic species, cladistics, DNA, systematics, biodiversity. INTRODUCTION Classes, orders, genera, and species accounted for 4735 of Human knowledge is expanding at an incredible rate. Linnaeus’ taxa. The remaining 487 taxa were distributed Current estimates based on the growth of academic pub- among 12 categories, such as subgenera or infrasubgen- lications and an increased number of filed patents claim era. Some of these categories were later invalidated by the our knowledge base will double every 2.31 to 2.44 years, International Commission on Zoological Nomenclature, respectively (Fuller 2007). What we know today makes but a dozen or so subgeneric names were revalidated and much of what we knew a decade ago obsolete. This is are still in use (Dubois 2007). perhaps most true in scientific fields and biology is no Following Linnaeus’ work, late 18th and early 19th exception. The following addresses the herpetofauna of naturalists Josephus Laurenti, Johann Schneider, Ber- Trinidad and Tobago as seen in the light of recent molecu- nard Lacépède, François-Marie Daudin and Johann Spix, lar studies. We discuss why the species of Trinidad and scrambled to apply binomial names to Western Hemi- Tobago continue to be renamed, and why the number of sphere amphibians and reptiles in the late 18th and early species is likely to increase. 19th centuries. By the end of the 19th century, it became Trinidad and Tobago fauna continues to have names popular to consolidate organisms that had a similar ap- changed, species added, and species subtracted. We make pearance and they were often lumped together sometimes predictions here on which species may be species com- under the oldest available name, other times not. About plexes and are candidates for future name changes based the time that R. R. Mole and F. W. Urich started mak- on the distance of the type locality from the islands. We ing lists of the Trinidad and Tobago herpetofauna, Albert also discuss the importance of educating the public on the Günther and George Boulenger were lumping species unique nature of the Trinidad and Tobago herpetofauna named in the early and mid-19th century together. Günther and the need that exists to encourage local people to take and Boulenger knew much about the world’s herpetofau- the steps necessary to conserve and restore the fauna na, but without today’s understanding of the significant where it is appropriate. role geography plays in speciation, often ignored type Carl Linnaeus’ Systema Naturae was an attempt to or- specimens and their localities (Adler 1989). This, paired ganize all life forms into categories. He succeeded in rec- with the late 19th and early 20th century trend to lump spe- ognizing a startling 5222 taxa in his 10th edition published cies, led early 20th century biologists to greatly underesti- in 1758. Some life forms were recognized and diagnosed mate world biodiversity. Endersby (2009) noted the terms in the text of the book, while others were in tables that il- “lumper” and “splitter” are still in use and often applied lustrated Linnaeus’ concept of hierarchical relationships. when the user disagrees with the limits of a species used 87 88 Living World, J. Trinidad and Tobago Field Naturalists’ Club, 2012 by someone else. Darwin recognized that classification a system of classification that reflects ancestry, and how would eventually evolve into genealogies when natural- a group of related species and their most recently shared ists learned “...to discover and trace the many diverging ancestor link together. Any group of species and their im- lines of descent...” That time has now arrived. As it turns mediate ancestor is known as a clade and most changes in out, splitting species is more useful in understanding scientific nomenclature today are the result of additions modern evolutionary concepts than having broadly de- or subtractions of species to or from a given clade. fined species, because it provides more detailed evidence In the second half of the 20th century, the roots of two of the evolutionary process. scientific disciplines evolved, providing powerful new tools for understanding evolution: molecular biology and Types and Type Localities cladistics. Cladistics is a way of evaluating and compar- The specimen used to describe a new species is re- ing hypotheses as to how species and groups of species ferred to as the “holotype,” or “syntypes,” if there is more are related to each other based upon shared evolutionary than one specimen. Type specimens are deposited in a novelties. It allows for an examination of diverse sets of museum so that they can serve as a reference for the spe- characters (morphological, behavioral, and molecular) by cies, and researchers describing related species can ex- considering all the evidence simultaneously to produce amine them for comparison. When H. W. Parker of the phylogenetic trees – diagrams that show the relationships British Museum described the dwarf marsupial frog Gas- between species and groups of species. Molecular biol- trotheca fitzgeraldi in 1934, the description was based ogy examines organisms at the level of genes (and their upon the type specimen in the British Museum and was products) and makes it possible to collect much more data given a number (it is now BMNH 1947.2.22.41). The useful to discerning relationships between species and geographic location where that type specimen originated groups of species. Molecular sequence data – the genetic from is the type locality, and Parker clearly stated that the code – is the closest science has come to an unbiased as- type of Gastrotheca [now Flectonotus] fitzgeraldi came sessment of evolutionary relationships. Thus, cladistics from “…3000 ft. on Mt. Tucuche….Trinidad.” Thus, Mt. and molecular biology are at the center of reconstructing Tucuche becomes the type locality for this species. Type the tree of life. Computer technology has made a huge specimens are important because they fix the identity of contribution to this effort, handling the large amounts of a species and type localities are important because they data generated by both cladistic analysis and molecular provide a location for the origin of the type specimen. sequencing. The type locality can be re-sampled for specimens and Linnaeus was responsible for about 23% of the DNA to compare to more distant populations if the type names earlier applied to Trinidad and Tobago amphibi- specimen is lost or, as is often the case, DNA cannot be ans and reptiles (Murphy 1997). That proportion has now recovered from the type specimen due to exposure to for- decreased slightly to 21% due to additions to the fauna malin used in the specimen fixation process. and the splitting of previously named species. Thus Lin- naeus’ contributions to the herpetofauna can be expected Evolving Ideas and the Herpetofauna to continue to decline as once-thought widespread spe- Today, the intimate relationship between geography cies are divided into species with more restricted distri- and biodiversity is well understood. Topography may im- butions and new species are found. pose barriers to gene flow or create corridors that permit The Trinidad and Tobago fauna has been described it. Barriers keep individuals of a species from moving as a depauperate Venezuelan fauna (Kenny 2000). There around, preventing them from reproducing with other is some truth in this view. Both islands are continental members of that species from other populations. Barriers and they contain a flora and fauna that had their ances- differ for individual species and could be as large as a riv- try on mainland South America. However it is a mistake er or a mountain range, or as small and seemingly simple to believe that the flora and fauna of the islands are just as a small waterfall, a road, or an agricultural field. Re- remnants of South America. By definition, terrestrial spe- stricting gene flow isolates populations and the results of cies on islands are genetically isolated, in this case by the that isolation may range from the formation of a new spe- sea that creates a barrier between Trinidad and Tobago cies to the extinction of an existing one. As topography and mainland Venezuela. changes over time, gene flow changes with it. Closely But gene isolation occurs even more specifically than related species may become isolated and then reconnect, at the island level. Trinidad and Tobago are full of unique only to be isolated again. Some may hybridize and form and isolated tracts of land whose organisms are unable to new species or become extinct because they cannot re- interact with other populations of the same species.