A multifaceted approach to species conservation


K. A. Crandall, Department of Biology, Brigham Young University, Provo, UT 84602, USA
Email: keith_crandall@byu.edu

The decline of a species to the point of endangerment is often due to a variety of problems that can range from habitat fragmentation, climate change, habitat decline due to inbreeding effects and loss of genetic variation. Species decline and endangerment is typically not due to a single issue, but rather a combination of interacting factors. Thus, studies that focus on single issues (e.g. just genetic diversity or just habitat destruction) often fail to hit the mark in terms of providing all the needed information for proper conservation management. Gebremedhin et al. (2009) provide a wonderful example of the power of combining genetic and ecological approaches to understand the complexity of issues involved in the decline and protection of the Ethiopian Walia ibex Capra walie.

When focusing conservation efforts on a taxonomic basis, it is critical to perform a thorough investigation of the taxonomic status and validity of the species in question (May & Harvey, 2009). Many conservation dollars have been wasted by focusing on inappropriate units for conservation due to a lack of a thorough taxonomic evaluation. Indeed, a solid taxonomy is the basis for exceptional biological insights, especially relative to conservation, as the taxonomy forms the basis for informative ecological studies and the best approach to a solid taxonomic study is to combine molecular and morphological approaches with appropriate taxon sampling (Wheeler, Raven & Wilson, 2004). The Walia ibex study provides a wonderful example of such a combined approach. Here the authors identify a species that is very much at risk (only 150–400 individuals and considered endangered by IUCN). They have obtained multiple genetic markers from nondestructive sampling (DNA from scat samples) for 37 individuals from the population, which seems like a small number for a population genetic study except that it represents 9–25% of the entire species! Not only is the number of samples important, but so is the geographic spread of sampling with respect to the species distribution. Here, again, the authors have done a careful job of sampling throughout the very limited distributional range of the species.

The Walia ibex study also uses appropriate genetic markers, both mitochondrial and nuclear, to establish phylogenetic positioning of the species with respect to other Capra species. The study combines these data with ecological niche data to test species status. It is often the ecological distinctiveness that is most important in terms of species divergences when dealing with recent speciation events (Crandall et al., 2000) and genetic surveys alone can be misleading both in terms of missing important ecological distinctiveness that has not developed in neutral genetic markers and the alternative of genetic distinctiveness of neutral markers but no ecological or functionally adaptive division (Meiri & Mace, 2007). Indeed, it is the combination of ecological, morphological and genetic data that is most powerful in providing robust species status designations. In addition, the authors also collected microsatellite data to test hypotheses of more recent demographic events impacting the population. The trick in conservation biology for small populations is to ask the question whether the populations where historically small or if the population size is the result of recent demographic events. The answer to this question critically informs conservation efforts and can best be addressed through this combination of ecological and genetic data.

Gebremedhin and colleagues then combine this information with sophisticated and appropriate analytical approaches to draw robust and interesting conclusions. First, their phylogenetic analysis clearly establishes the phylogenetic position of the C. walie for the first time and estimates an associated divergence time with a relaxed molecular clock approach. Their microsatellite data support the hypothesis of a recent and prolonged population decline. Finally, the ecological niche modeling showed clear separation of ecotypes corresponding to the current taxonomic designations of C. walie and Capra nubiana. Thus, this study represents an excellent example of the power of combining molecular, morphological and ecological data to gain critical insights into species status, demographic history, genetic variability and adaptation of a critically endangered species and how such insights can be effectively used to better inform essential conservation efforts. This study should serve as a model for future studies of endangered species of how multidisciplinary approaches coupled with extensive nondestructive sampling can inform conservation action for endangered species.