Refugia persistence of Qinghai-Tibetan plateau by the cold-tolerant bird Tetraogallus tibetanus (Galliformes: Phasianidae)

Phylogenetic biome conservatism as a key concept for an integrative understanding of evolutionary history: Galliformes and Falconiformes as study cases

Biomes are climatically and biotically distinctive macroecological units that formed over geological time scales. Their features consolidate them as ‘evolutionary scenarios’, with their own diversification dynamics. Under the concept of phylogenetic niche conservatism, we assessed, for the first time, the evolution of biome occupation in birds. We aimed to analyse patterns of adaptation to different climatic regimes and the determinant factors for colonization of emerging biomes by clades from different ancestral biomes. In this work, we reconstructed the biome occupation history of two clades of birds (Galliformes and Falconiformes) under an integrative perspective through a comprehensive review of ecological, phylogenetic, palaeontological and biogeographical evidence. Our findings for both groups are consistent with a scenario of phylogenetic biome conservatism and highlight the importance of changes in climate during the Miocene in the adaptation and evolution of climatic niches. In particular, our results indicate high biome conservatism associated with biomes situated in some of the extremes of the global climate gradient (evergreen tropical rainforest, steppe and tundra) for both bird taxa. Finally, the historical dynamics of tropical seasonal biomes, such as tropical deciduous woodlands and savannas, appear to have played a preponderant role during the diversification processes of these bird lineages.

No hybrid snowcocks in the Altai-Hyper-variable markers can be problematic for phylogenetic inference

A recent article in Ecology and Evolution featured the discovery of hybrid snowcocks (Tetraogallus) and speculated on the hybrid origin of an extant species (T. altaicus). Comprehensive re-analyses of original data from the latter paper reliably refute the phylogenetic hypothesis taken as firm evidence of a past hybridization event in these birds. The new re-analyses showed that there is no evidence of hybridization in these snowcocks from the data available so far.

Inter-glacial isolation caused divergence of cold-adapted species: the case of the snow partridge

Deciphering the role of climatic oscillations in species divergence helps us understand the mechanisms that shape global biodiversity. The cold-adapted species may have expanded their distribution with the development of glaciers during glacial period. With the retreat of glaciers, these species were discontinuously distributed in the high-altitude mountains and isolated by geographical barriers. However, the study that focuses on the speciation process of cold-adapted species is scant. To fill this gap, we combined population genetic data and ecological niche models (ENMs) to explore divergence process of snow partridge (Lerwa lerwa). Lerwa lerwa is a cold-adapted bird that is distributed from 4,000 to 5,500 m. We found 2 genetic populations within L. lerwa, and they diverged from each other at about 0.40–0.44 million years ago (inter-glacial period after Zhongliangan glaciation). The ENMs suggested that L. lerwa expanded to the low elevations of the Himalayas and Hengduan mountains during glacial period, whereas it contracted to the high elevations, southern of Himalayas, and Hengduan mountains during inter-glacial periods. Effective population size trajectory also suggested that L. lerwa expanded its population size during the glacial period. Consistent with our expectation, the results support that inter-glacial isolation contributed to the divergence of cold-adapted L. lerwa on Qinghai-Tibetan Plateau. This study deepens our understanding of how climatic oscillations have driven divergence process of cold-adapted Phasianidae species distributed on mountains.

The uplift of the Qinghai-Tibet Plateau and glacial oscillations triggered the diversification of Tetraogallus (Galliformes, Phasianidae)

The Qinghai-Tibet Plateau (QTP) plays an important role in avian diversification. To reveal the relationship between the QTP uplift and avian diversification since the Late Cenozoic, here, we analyzed the phylogenetic relationship and biogeographical pattern of the genus Tetraogallus (Galliformes, Phasianidae) and the probable factors of speciation in the period of the QTP uplift inferred from concatenated data of four nuclear and five mitochondrial genes using the method of the Bayesian inference. Phylogenetic analysis indicated that T. himalayensis had a close relationship with T. altaicus and conflicted with the previous taxonomy of dark-bellied and white-bellied groups. The molecular clock showed that the speciation of Tetraogallus was profoundly affected by the uplift of the QTP and glacial oscillations. Biogeographic analysis suggested that the extant snowcocks originated from the QTP, and the QTP uplift and glacial oscillations triggered the diversification of Tetraogallus ancestor. Specifically, the uplift of the mountain provided a prerequisite for the colonization of snowcocks Tetraogallus as a result of the collision between the Indian and the Arab plates and the Eurasian plate, in which ecological isolation (the glacial and interglacial periods alternate) and geographical barrier had accelerated the Tetraogallus diversification process. Interestingly, we discovered hybrids between T. tibetanus and T. himalayensis for the first time and suggested that T. tibetanus and T. himalayensis hybridized after a second contact during the glacial period. Here, we proposed that the hybrid offspring was the ancestor of the T. altaicus. In conclusion, the uplift of QTP and glacial oscillations triggered the snowcocks colonization, and then, isolation and introgression hybridization promoted diversification.