Herpetology and conservation genetics


Robert Jehle
Email: r.jehle@salford.ac.uk

The idea that genetic diversity influences the survival of endangered species is almost as old as the field of conservation biology itself (Caughley, 1994 and numerous references therein). It is remarkable, then, that ‘conservation genetics’ as a recognized scientific discipline only emerged about one decade ago. One reason might be that technological advances only recently allowed us to quantify how a combination of genotypes and environments shape the demography of endangered populations (e.g. Primmer, 2009), whereas the debate on whether genetic factors are important for population persistence remained more open in the past. Two further reasons might account for the recent success of conservation genetics. Due to the progression of disturbed ecosystems, conservationists are increasingly forced to focus on the active management of populations rather than preserving them without intervention in pristine habitats. In such a framework, genetic markers offer practical conservation tools, for example aiding or even dictating the selection of individuals for translocation and reintroduction programmes, or revealing the extent of illegal wildlife trade through forensic applications. Secondly, the attractiveness of conservation genetics as a discipline is supported by its focus on well-known, charismatic wildlife species (see case studies presented in Frankham, Ballou & Briscoe, 2009).

Wildlife research centres on warm-blooded vertebrates, and it is therefore not surprising that herpetology has played a relatively small role in major outlets for conservation genetic studies, such as Molecular Ecology and Conservation Genetics (Fig. 1). Although the wide attraction devoted to the unprecedented decline of amphibians resulted in the regular consultation of genetic tools for their conservation (Jehle & Arntzen, 2002; Beebee, 2005; Storfer, Eastman & Spear, 2009), they still contribute with only 7.6% to all publications on vertebrates published in these journals between 2001 and 2009. With a corresponding figure of 9.2% for reptiles (Fig. 1), both groups are well below their representative share of species diversity (11.0 and 14.4%, respectively, assuming 6700 amphibians, 8800 reptiles and 61 000 vertebrates). This reflects a conservation genetics ‘centre of gravity’ within higher-order vertebrates and/or commercially more relevant species, and indicates that there is scope to increase the use of genetic tools to study endangered caecilians, newts, frogs, squamates, tuataras, and crocodiles.

Figure 1.

 Herpetological publications in the scientific journals Molecular Ecology (black bars, section Population and Conservation Genetics only) and Conservation Genetics (white bars) since 2001, in percentage of all publications on vertebrates. (a) Amphibians, (b) reptiles.

The conservation genetics section of this special issue presents two microsatellite-based studies devoted to pond-breeding European amphibians (Arntzen, Burke & Jehle, 2010; Ficetola et al., 2010). Although only a small part of herpetology and the available genetic toolbox is covered, these contributions take advantage of the fact that shared breeding pools translate into shared gene pools, and that demographically well-structured species offer excellent model systems to study spatio-temporal genetic effects in a conservation context.

To evaluate the general role of amphibians and reptile for emerging topics in conservation genetics, one idea is to map them onto what is discussed in another recent conference-based special issue (‘ESF-ConGen: Integrating population genetics and conservation biology’, Conservation Genetics11 (2); see also the conference report in Biology Letters6 (1), 3–6). By doing so, it becomes clear that members of our taxonomic focus groups can do an excellent job to promote the understanding of genetic problems when there is only limited potential for dispersal. Amphibians and reptiles are regularly suspected to be more prone to inbreeding (and potentially outbreeding) depression than more mobile, continuously distributed animals; however, the question of whether their genome architecture is adapted to living in pronounced population structure is still open – after all, their low vagility is not a novel evolutionary phenomenon. The comparatively large genome of many amphibians and reptiles poses difficulties, for example for genome mapping projects, but next-generation sequencing technologies should render this problem less severe. A disadvantage of some herptiles is that their complex life-histories and cryptic lifestyles pose logistical difficulties for inferring comprehensive pedigrees in wild populations, a powerful tool for an understanding of quantitative genetic variation and microevolution, for example, in view of environmental change.

Viewed from the other side, what genetic approaches and considerations would be beneficial for the future conservation of amphibians and reptiles? The main focus probably lies in the area of applied, active conservation management. Although captive breeding programmes for reintroduction are on the rise, there are so far no examples of studbooks and the genotype-informed choice of best-suited mating pairs. The emphasis in genetic management of wild populations has so far been on identifying large-scale management units in a phylogeographic framework. Although herpetology offers a textbook example for genetic rescue (the adder Vipera berus, see e.g. Frankham et al., 2009), such approaches still need to be more broadly applied across fragmented populations requiring active management. Another area where information derived from genetic markers has already proven to be crucial and will likely continue to do so is the documentation and management of emerging diseases (e.g. Fisher, Garner & Walker, 2009).