Homoploid hybridization of plants in the Hengduan mountains region.

Rui Yang,Ryan Folk,Ningning Zhang,Xun Gong

doi:10.1002/ece3.5393

Abstract

The Hengduan Mountains Region (HMR) is a major global biodiversity hotspot. Complex tectonic and historical climatic conditions created opportunities for natural interspecific hybridization. Likewise, anthropogenic disturbance potentially raises the frequency of hybridization. Among species studies to date, the frequency of homoploid hybridization appears in the HMR. Of nine taxa in which natural hybridization has been detected, three groups are involved in homoploid hybrid speciation, and species pairs from the remaining six genera suggest that continuous gene flow occurs in hybrid zones. Reproductive isolation may greatly affect the dynamic and architecture of hybrid zones in the HMR. Asymmetrical hybridization and introgression can primarily be attributed to both prezygotic and postzygotic barriers. The frequent observation of such asymmetry may imply that reproductive barrier contributes to maintaining species boundaries in the alpine region. Ecological isolations with environmental disturbance may promote breeding barriers between parental species and hybrids. Hybrid zones may be an important phase for homoploid hybrid speciation. Hybrid zones potentially provided abundant genetic resources for the diversification of the HMR flora. The ecological and molecular mechanisms of control and mediation for natural hybridization will help biologists to understand the formation of biodiversity in the HMR. More researches from ecological and molecular aspects were required in future studies.

Highlights

The Qinghai‐Tibetan Plateau (QTP) and its adjacent Hengduan Mountains Region (HMR) have been considered as one of the im‐ portant biodiversity hotspots in the world (Myers, Mittermeier, Mittermeier, Da Fonseca, & Kent, 2000)
The objectives of this paper are to (a) discuss the potential factors which trigger natural hybridization in the alpine region; (b) briefly review natural hybridization and homoploid hybrid speciation in the HMR; (c) discuss the effects of reproductive isolation on the level and direction of gene flow in hybrid zones; and (d) propose how natural hybridization may be important to the diversification of the HMR flora
Approximately 18 species pairs from nine genera are suggested to be involved in homoploid hybridization

Summary

Introduction

The Qinghai‐Tibetan Plateau (QTP) and its adjacent Hengduan Mountains Region (HMR) have been considered as one of the im‐ portant biodiversity hotspots in the world (Myers, Mittermeier, Mittermeier, Da Fonseca, & Kent, 2000). The HMR in particular har‐ bors the richest temperate flora of seed plants in the world and is considered to be among the areas with the high concentration of endemic species in the world (Li & Li, 1993; Wu, 1988). In the alpine zone of the HMR, the number of seed plant species is two to three times than that in other known alpine region (Xu, Li, & Sun, 2014a, 2014b). Climate shift accompanied by orogenic events may lead to geographical overlap of some species, which impel the frequent contact of plants in the HMR. The rate of species differentiation may coincide with the rapid uplift of the HMR, and the latter may have facilitated the diversification of species in the late Miocene (11.6–5.3 MYA) (Sun et al, 2017; Xing & Ree, 2017)

Objectives

Findings

Conclusion