5/30/2023 0 Comments Types of songbird![]() Outstanding questions regarding the role of genome architecture in ecological adaptation include whether mutations in coding or noncoding regions tend to be subject to divergent selection for adaptation (Hu et al., 2022 Lai et al., 2019 Malinsky et al., 2015 Nosil & Feder, 2012 Wolf & Ellegren, 2017), whether chromosomal inversions facilitate the accumulation of adaptive genetic differences between diverging lineages (Kirkpatrick & Barton, 2006 Poelstra et al., 2014), and whether genes related to ecological difference tend to be located in sex chromosomes or associated with those under sexual selection that hence facilitate the evolution of reproductive isolation (Bourgeois et al., 2020 Edwards et al., 2015 Malinsky et al., 2015 Qvarnström & Bailey, 2009). Studies have shown that the arrangement of mutations in the genome is important to ecological adaptation because structural genomic variations often affect multiple genes together (Malinsky et al., 2015 Zong et al., 2021). Genomic sequencing provides a powerful tool not only for reconstructing divergence history, but also for testing hypotheses regarding the origin and association of mutations that contribute to physiological and morphological adaptation to new environments (Seehausen et al., 2014), including high elevations (Hu et al., 2022 Lai et al., 2019 Martini et al., 2021 Qu et al., 2013 Qu et al., 2021 Storz, 2021). Although these phenotypic changes imply natural selection for beneficial alleles in the corresponding genes, it is difficult to tell how the evolutionary processes actually unfolded in wild populations. Temperature, together with other environmental factors such as oxygen level and high ultraviolet (UV) light that change with elevation, could have also caused physiological adaptations in respiratory, cardiovascular, immune and metabolic systems (Mishra & Ganju, 2010 Scott et al., 2008 Siebenmann et al., 2017). Animals at higher elevations may have smaller body extremities, such as bird beaks, for reducing heat loss (Symonds & Tattersall, 2010). ![]() Analysing species along this kind of gradient thus provides a simple system, ideal for examining the mechanism of ecological adaptation. For species that are distributed along an elevational gradient, populations have to physiologically and/or morphologically adapt to distinct habitats across a continuum of environmental change. However, adaptation-driven divergence (Nosil, 2012 Schluter, 2009), which seems conceptually straightforward, can be difficult to perceive and interpret in nature because ecological contexts are often intricate. When species adapt to new habitats and accumulate genetic changes that contribute to their local adaptation, they may show genomic incompatibility between diverging populations that may then evolve into new species (Nosil & Feder, 2012 Schluter, 2001). These findings improve our understanding of how ecological adaptation drives population divergence from the perspective of genomic architecture. The results reveal the genomic bases of morphological and physiological adaptation in this species to the low temperature, hypoxia and high UV light environment at high elevation. The altitudinally divergent mutations might regulate genes related to haematopoietic, metabolic, immune, auditory and vision functions, as well as cerebrum morphology and plumage development. We also found that altitudinally divergent mutations were mostly located in noncoding regions and tended to accumulate in chromosomal inversions and autosomes. We found that the montane babblers had smaller beaks than the lowland ones, consistent with Allen's rule, and identified candidate genes- COL9A1 and SOX11-underlying the beak size changes. ![]() The montane and lowland Taiwan populations diverged with gene flow between them, suggesting strong selection associated with different elevations. We focused on the genomic sequences of 43 birds from five populations to show that the Taiwan group split from its sister group in mainland China around 1–2 million years ago (Ma) and colonized the montane habitats of Taiwan at least twice around 0.03–0.22 Ma. Thus, we examined the adaptation of a widespread songbird-the rufous-capped babbler ( Cyanoderma ruficeps)-to a relatively simple system: distinct environments across elevational gradients on the mountainous island of Taiwan. However, deciphering the genomic mechanism of ecological adaptation is difficult because ecological environments are often too complex for straightforward interpretation. Organisms often acquire physiological and morphological modifications to conquer ecological challenges when colonizing new environments which lead to their adaptive evolution.
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