Genomic heterogeneity of divergence between hybridizing species may reflect heterogeneity of introgression, but also processes unrelated to hybridization. Heterogeneous introgression and its repeatability can be directly tested in natural hybrid zones by examining multiple transects. Here, we studied hybrid zones between the European newts Lissotriton montandoni and two lineages of Lissotriton vulgaris, with replicate transects within each zone. Over 1,000 nuclear genes located on a linkage map and mitochondrial DNA were investigated using geographical and genomic clines. Overall, the five transects were all similar, showing hallmarks of strong reproductive isolation: bimodal distribution of genotypes in central populations and narrow allele frequency clines. However, the extent of introgression differed between the zones, possibly as a consequence of their different ages, as suggested by the analysis of heterozygosity runs in diagnostic markers. In three transects genomic signatures of small‐scale (~2 km) zone movements were detected. We found limited overlap of cline outliers between transects, and only weak evidence of stronger differentiation of introgression between zones than between transects within zones. Introgression was heterogeneous across linkage groups, with patterns of heterogeneity similar between transects and zones. Predefined candidates for increased or reduced introgression exhibited only a subtle tendency in the expected direction, suggesting that interspecific differentiation is not a reliable indicator for the strength of introgression. These hierarchically sampled hybrid zones of apparently different ages show how introgression unfolds with time and offer an excellent opportunity to dissect the dynamics of hybridization and architecture of reproductive isolation at advanced stages of speciation.
Questions: Is rock climbing pressure, together with microtopographic conditions, disturbing cliff plant cover and composition? What are the climbing impacts on rock specialist and non-specialist species? Can a case-control approach, not previously implemented in cliff environments, offer additional value for actual and long-term ecological research?Location: Chulilla, Levante coast, Spain. Methods:We surveyed in situ nine rock climbing routes in order to examine differences in plant species richness and vegetation cover between unclimbed and climbed transects. To evaluate the effect of rock climbing on vegetation, we implemented a case-control methodology using the two zones immediately adjacent to common climbing routes as control points (i.e. unclimbed transects). Three quadrats of 3 m × 3 m were established at different cliff heights. All identified species were categorized as either specialized rock species or non-specialized rock species based on their habitat preferences from literature. Non-specialized rock species were further differentiated as either moderately associated with rocky environments or strict generalists. The rock climbing impact on each group of species was analysed using LMM. Results:Our results provide evidence of the effects of rock climbing on a Mediterranean cliff, which has received little attention so far. Significantly fewer generalist species were present on climbed compared to unclimbed transects, while specialized and moderately specialized rock species were not significantly affected by rock climbing intensity. Furthermore, while rock-specific and moderately specialized species could cope with microsite heterogeneity, areas with fewer cracks had significantly negative effects on generalist species. Conclusions:Moderate rock climbing activity on cliff environments might not reduce the presence of specialized rock-dwelling species; however, this activity inherently impacts the biodiversity of cliff ecosystems due to its large effect on generalist species. We recommend that future conservation studies account for the degree of species dependence on rocky habitats to better understand rock-climbing impacts in these singular ecosystems. According to our experience, the implementation of an
The Anthropocene has witnessed catastrophic amphibian declines across the globe.A multitude of new, primarily human-induced drivers of decline may lead to extinction, but can also push species onto novel evolutionary trajectories. If these are recognized by amphibian biologists, they can be engaged in conservation actions.Here, we summarize how principles stemming from evolutionary concepts have been applied for conservation purposes, and address emerging ideas at the vanguard of amphibian conservation science. In particular, we examine the consequences of increased drift and inbreeding in small populations and their implications for practical conservation. We then review studies of connectivity between populations at the landscape level, which have emphasized the limiting influence of anthropogenic structures and degraded habitat on genetic cohesion. The rapid pace of environmental changes leads to the central question of whether amphibian populations can cope either by adapting to new conditions or by shifting their ranges. We gloomily conclude that extinction seems far more likely than adaptation or range shifts for most species. That said, conservation strategies employing evolutionary principles, such as selective breeding, introduction of adaptive variants through translocations, ecosystem interventions aimed at decreasing phenotype-environment mismatch, or genetic engineering, may effectively counter amphibian decline in some areas or for some species. The spread of invasive species and infectious diseases has often had disastrous consequences, but has also provided some premier examples of rapid evolution with conservation implications. Much can be done in terms of setting aside valuable amphibian habitat that should encompass both natural and agricultural areas, as well as designing protected areas to maximize the phylogenetic and functional diversity of the amphibian community. We conclude that an explicit consideration and application of evolutionary principles, although certainly not a silver bullet, should increase effectiveness of amphibian conservation in both the short and long term. K E Y W O R D Samphibians, conservation biology, conservation genetics, habitat degradation, host parasite interactions, natural selection and contemporary evolution
By combining 7077 SNPs and 61 microsatellites, we present the first linkage map for some of the early diverged lineages of the common frog, Rana temporaria, and the densest linkage map to date for this species. We found high homology with the published linkage maps of the Eastern and Western lineages but with differences in the order of some markers. Homology was also strong with the genome of the Tibetan frog Nanorana parkeri and we found high synteny with the clawed frog Xenopus tropicalis. We confirmed marked heterochiasmy between sexes and detected nonrecombining regions in several groups of the male linkage map. Contrary to the expectations set by the male heterogamety of the common frog, we did not find male heterozygosity excess in the chromosome previously shown to be linked to sex determination. Finally, we found blocks of loci showing strong transmission ratio distortion. These distorted genomic regions might be related to genetic incompatibilities between the parental populations, and are promising candidates for further investigation into the genetic basis of speciation and adaptation in the common frog.
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