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Global climate change is one of the major driving forces for adaptive shifts in migration and breeding phenology and possibly impacts demographic changes if a species fails to adapt sufficiently. In Western Europe, pied flycatchers (Ficedula hypoleuca) have insufficiently adapted their breeding phenology to the ongoing advance of food peaks within their breeding area and consequently suffered local population declines. We address the question whether this population decline led to a loss of genetic variation, using two neutral marker sets (mitochondrial control region and microsatellites), and one potentially selectively non-neutral marker (avian Clock gene). We report temporal changes in genetic diversity in extant populations and biological archives over more than a century, using samples from sites differing in the extent of climate change. Comparing genetic differentiation over this period revealed that only the recent Dutch population, which underwent population declines, showed slightly lower genetic variation than the historic Dutch population. As that loss of variation was only moderate and not observed in all markers, current gene flow across Western and Central European populations might have compensated local loss of variation over the last decades. A comparison of genetic differentiation in neutral loci versus the Clock gene locus provided evidence for stabilizing selection. Furthermore, in all genetic markers, we found a greater genetic differentiation in space than in time. This pattern suggests that local adaptation or historic processes might have a stronger effect on the population structure and genetic variation in the pied flycatcher than recent global climate changes.
Biodiversity is unevenly distributed on Earth and hotspots of biodiversity are often associated with areas that have undergone orogenic activity during recent geological history (i.e. tens of millions of years). Understanding the underlying processes that have driven the accumulation of species in some areas and not in others may help guide prioritization in conservation and may facilitate forecasts on ecosystem services under future climate conditions. Consequently, the study of the origin and evolution of biodiversity in mountain systems has motivated growing scientific interest. Despite an increasing number of studies, the origin and evolution of diversity hotspots associated with the Qinghai-Tibetan Plateau (QTP) remains poorly understood. We review literature related to the diversification of organisms linked to the uplift of the QTP. To promote hypothesis-based research, we provide a geological and palaeoclimatic scenario for the region of the QTP and argue that further studies would benefit from providing a complete set of complementary analyses (molecular dating, biogeographic, and diversification rates analyses) to test for a link between organismic diversification and past geological and climatic changes in this region. In general, we found that the contribution of biological interchange between the QTP and other hotspots of biodiversity has not been sufficiently studied to date. Finally, we suggest that the biological consequences of the uplift of the QTP would be best understood using a meta-analysis approach, encompassing studies on a variety of organisms (plants and animals) from diverse habitats (forests, meadows, rivers), and thermal belts (montane, subalpine, alpine, nival). Since the species diversity in the QTP region is better documented for some organismic groups than for others, we suggest that baseline taxonomic work should be promoted.
Bird-mediated seed dispersal is crucial for the regeneration and viability of ecosystems, often resulting in complex mutualistic species networks. Yet, how this mutualism drives the evolution of seed dispersing birds is still poorly understood. In the present study we combine whole genome re-sequencing analyses and morphometric data to assess the evolutionary processes that shaped the diversification of the Eurasian nutcracker (Nucifraga), a seed disperser known for its mutualism with pines (Pinus). Our results show that the divergence and phylogeographic patterns of nutcrackers resemble those of other non-mutualistic passerine birds and suggest that their early diversification was shaped by similar biogeographic and climatic processes. The limited variation in foraging traits indicates that local adaptation to pines likely played a minor role. Our study shows that close mutualistic relationships between bird and plant species might not necessarily act as a primary driver of evolution and diversification in resource-specialized birds.