The Greater Limpopo Transfrontier Conservation Area (GLTFCA) is one of the last refuges for the endangered African wild dog and hosts roughly one-tenth of the global population. Wild dogs in this area are currently threatened by human encroachment, habitat fragmentation and scarcity of suitable connecting habitat between protected areas. We derived genetic data from mitochondrial and nuclear markers to test the following hypotheses: (i) demographic declines in wild dogs have caused a loss of genetic variation, and (ii) Zimbabwean and South African populations in the GLTFCA have diverged due to the effects of isolation and genetic drift.Genetic patterns among five populations, taken with comparisons to known information, illustrate that allelic richness and heterozygosity have been lost over time, presumably due to effects of inbreeding and genetic drift. 1Genetic structuring has occurred due to low dispersal rates, which was most apparent between Kruger National Park and the Zimbabwean Lowveld. Immediate strategies to improve gene flow should focus on increasing the quality of habitat corridors between reserves in the GLTFCA and securing higher wild dog survival rates in unprotected areas, with human-mediated translocation only undertaken as a last resort.

Adaptation to different ecological environments can, through divergent selection, generate phenotypic and genetic differences between populations, and eventually give rise to new species. The fire salamander (Salamandra salamandra) has been proposed to represent an early stage of ecological speciation, driven by differential habitat adaptation through the deposition and development of larvae in streams versus ponds in the Kottenforst near Bonn (Germany). We set out to test this hypothesis of ecological speciation in an area different from the one where it was raised and we took the opportunity to explore for drivers of genetic differentiation at a landscape scale. A survey over 640 localities demonstrated the species' presence in ponds and streams across forests, hilly terrain and areas with hedgerows ('bocage'). Genetic variation at 14 microsatellite loci across 41 localities in and around two small deciduous forests showed that salamander effective population sizes were higher in forests than in the bocage, with panmixia in the forests (F st < 0.010) versus genetic drift or founder effects in several of the small and more or less isolated bocage populations (F st > 0.025). The system fits the 'mainlandisland' metapopulation model rather than indicating adaptive genetic divergence in pond versus stream larval habitats. A reanalysis of the Kottenforst data indicated that microsatellite genetic variation fitted a geographical rather than an environmental axis, with a sharp transition from a western pondbreeding to an eastern, more frequently stream-breeding group of populations. A parallel changeover in mitochondrial DnA exists but remains to be well documented. the data support the existence of a hybrid zone following secondary contact of differentiated lineages, more so than speciation in situ. Adaptation to different ecological environments can, through divergent selection, generate phenotypic and genetic differences between populations. These changes may eventually give rise to new species. The speciation process is often quantitative in nature, as illustrated by numerous studies showing that divergence during speciation varies continuously, and the sequence of genetically-based changes that occur as two lineages on the pathway to reproductive isolation diverge from one another has been coined the 'speciation continuum' 1,2. Divergent evolution and reproductive isolation are the primary elements of the speciation continuum, but many have recognized that reproductive isolation is usually a signature effect rather than a primary cause of speciation. Whereas the mechanisms underlying reproductive isolation are by now mostly well understood (such as natural and sexual selection and genetic drift due to founder events, etc.), biologists continue to struggle with understanding how and why these evolutionary processes cause the disjoined genetic connections that are integral to the emergence of new species, in particular in conditions of sympatry 3-6. Organisms that are organized in deme-structured metapopulations, w...

This Article contains a typographical error in the Author Contributions section where, "J.W.A. conceived and designed the study, and organized the species inventory. The files SI I and SI V are also available at https://www.repository.naturalis.nl/record/707616. J.v.B. collected the tissue samples and performed the laboratory work in the laboratory of S. Steinfartz, Braunschweig. J.W.A. analyzed the data and wrote the manuscript with the help of J.v.B. " should read: "J.W.A. conceived and designed the study, and organized the species inventory. J.v.B. collected the tissue samples and performed the laboratory work in the laboratory of S. Steinfartz, Braunschweig. J.W.A. analyzed the data and wrote the manuscript with the help of J.v.B. " As a result, the 'Data Availability' section, "The genotypic data for fire salamanders from Mayenne, France are presented in Supplementary Information II.