About this Research Topic
Mountainous regions (e.g. the Andes in South America, the Himalayas and the Hengduan Mountains in Asia, the mountains in the Mediterranean Basin, the Eastern Arc Mountains in Africa, or the Southern Alps in New Zealand) host a large proportion of global species diversity, and many of them are recognized as world biodiversity hotspots. It is widely agreed that the rich species diversity in mountainous regions is due to higher speciation rates compared to lowlands; such accelerated diversification is mainly triggered by tectonic driven mountain building, which gives rise in turn to highly heterogeneous topography, various climate types and wide ecological gradients. Meanwhile, mountain species need to move considerably shorter distances to track their optimal conditions as compared with lowland species, and hence they experience lower rates of extinction during episodes of large climate changes, e.g. Quaternary climate oscillations. So, mountains everywhere are generally recognized to play a dual role of ‘species museums’ and ‘species cradles’.
Evolutionary history and population genetics studies in mountainous regions have often revealed that mountain building triggered radiative speciation, resulting in the generation of many endemic species; the formation of geographic barriers to gene flow between previously continuous populations (i.e., allopatry) is a major mechanism for speciation and intraspecific divergence in mountains; hybridization and subsequent (allo)polyploidy (‘polyploid speciation’), as well as hybridization between species of the same ploidy level (‘homoploid speciation’), are also important avenues for generating new species. Mountain building may also provide many new habitats that stimulate the arising of barriers to gene flow between populations occurring on different environments (‘ecological speciation’).
These preliminary findings may serve as stepping stone to address a wide range of questions, including: (1) What is the distribution pattern of genetic variability at population level in species groups that experienced radiative speciation? (2) Is integrative taxonomy effective in delimitating closely related species in mountainous regions? (3) What is the role of hybridization and natural selection during speciation? (4) Is isolation by environment more important than isolation by distance in mountains? (5) What genetic variation and gene expression changes are related to local adaptation to altitudinal gradients? (6) How did the Quaternary climatic oscillations and geological events affect the demographic history of widespread and endemic species? (7) How did the mountain uplift processes interplay with the late Neogene climate changes in shaping the evolutionary history of mountain plants? There are much evolutionary history and population genetic questions to be explored in the mountains, and this research topic welcomes articles, opinions and reviews addressing any of these issues.
Keywords: Genetic variation, intraspecific divergence, speciation, hybridization, species delimitation
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