Is hybridization the reason why the Qinghai-Tibet Plateau became the "cradle of evolution"?

Qinghai-Tibet Plateau

Have a complex

Geological tectonic evolution history

Rich landforms

and changing climate conditions

For species differentiation

and the formation of biodiversity

Created the conditions

According to incomplete statistics

The Qinghai-Tibet Plateau gave birth to

At least 1500

12,000 vascular plants

More than 20% of species

Endemic to the region

This ratio

Higher in the Himalayas and Hengduan Mountains

For a long time

The Qinghai-Tibet Plateau, the "Cradle of Evolution"

How is it formed?

Evolutionary biology

and ecology

Important scientific issues of common concern

Recently, Professor Liu Jianquan's team from Lanzhou University systematically sorted out and summarized the latest research progress in the formation of species on the Qinghai-Tibet Plateau. Combining detailed evidence, they explained the important role of hybridization in the formation of plant species on the Qinghai-Tibet Plateau and looked forward to future research directions in this field.

Image source: Lanzhou University News Network

Although geographical isolation and differentiation selection caused by different habitats have always been considered to be important driving forces for species formation on the Qinghai-Tibet Plateau, a large number of population genomics analyses have found that gene flow is ubiquitous in the speciation process of many plant groups on the Qinghai-Tibet Plateau.

This may be due to the dispersal of pollen and seeds or other factors that caused the originally isolated groups to have a second contact. It is worth mentioning that interspecific hybrid individuals and even hybrid groups exist in almost all the species diversity groups investigated on the Qinghai-Tibet Plateau, indicating that many species are still on the road to species differentiation. Frequent hybridization creates opportunities for the formation of new species.

Hybrid speciation → new species formation → an important mechanism for the generation of biodiversity, which includes two methods: allopolyploidy formed by polyploidization after hybridization and homoploid hybrid speciation.

The extent and uplift history of the Qinghai-Tibet Plateau. Image source: Lanzhou University News Network

Existing evidence suggests that the polyploid species on the Qinghai-Tibet Plateau have a very complex evolutionary history, often involving the participation of extinct "ghost species".

In addition, if two diploid genetic populations fail to form morphological differentiation, but as independent evolutionary lineages, the polyploidy they form is often difficult to detect. The existence of these factors makes it easy for polyploid species to be overlooked.

As allopolyploid species are found to be widespread in more and more plant groups, studies speculate that the contribution of polyploidy to species formation on the Qinghai-Tibet Plateau may have been underestimated.

Possible driving factors for species diversity formation on the Qinghai-Tibet Plateau

Image source: Lanzhou University News Network

Homoploid hybrid speciation, the formation of new species through hybridization without changing the number of chromosomes, is considered rare and unlikely. However, on the Qinghai-Tibet Plateau, at least five species have been reported to have been formed by homoploid hybridization, including Pinus alpinus, Hippophae rhamnoides, Picea purpurogena, Cupressus chinensis, and Hazelnut, which is higher than the number of homoploid hybrid speciation cases reported in other regions of the world.

Alpine pine

Seabuckthorn

Minjiang cypress

Picea purpurogena

Image source: Plant Intelligence

In particular, the molecular genetic universal model of homoploid hybrid species formation proposed and demonstrated by the research team in the early stage only requires the recombination of at least two genes controlling reproductive isolation traits to quickly form new hybrid species, which makes the formation of homoploid hybrid species easier in theory.

Methods for identifying key genes involved in parallel adaptive divergence and speciation

Image source: Lanzhou University News Network

In summary, isolation, natural selection and hybridization may jointly drive the formation of rich species diversity in the Qinghai-Tibet Plateau.

The research team also pointed out the direction for future development in this field, which is the need to use population genomics and molecular genetics to identify key genes in the process of species formation.

At the same time, it is necessary to conduct in-depth research on the molecular mechanisms of reproductive isolation caused by parallel adaptive differentiation of different species in the specific habitats of the Qinghai-Tibet Plateau.

END

Source: Lanzhou University News Network Producer: Ma Lian Editor: Wu Nan

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