Plant speciation across environmental gradients and the occurrence and nature of hybrid zones

• Published in: Journal of systematics and evolution : JSE Vol. 55; no. 4; pp. 238 - 258
• Main Author: Abbott, Richard J.
• Format: Journal Article
• Language: English
• Published: Beijing Wiley Subscription Services, Inc 01.07.2017
• Subjects: Animal behavior; Climate; Climate change; disturbance; ecology; Environmental gradient; environmental gradients; evolution; Flow stability; Gene flow; Hybrid zones; hybridization; hybrids; Indigenous species; Literature reviews; Mitochondrial DNA; Plant species; Reproductive isolation; secondary contact; Speciation; Species; Systematics; 形态形成; 性质; 植物杂交; 植物物种; 气候变化; 混合区; 环境梯度; 生殖隔离
• ISSN: 1674-4918; 1759-6831
• DOI: 10.1111/jse.12267

Environmental gradients are very common and many plant species respond to them through adaptive genetic change. This can be a first step along a continuum of change that leads ultimately to the origin of fully reproductively isolated forms, i.e., ＇biological species＇. Before complete reproductive isolation is achieved, hybrid zones may form between divergent lineages either through primary intergradation or secondary contact. Here, I review the literature on plant hybrid zones between native species and highlight： mode of origin （primary intergradation versus secondary contact）; distribution among plant families, genera and life form; type and genotypic composition related to strength and type of reproductive isolation between parental lineages; nature of prezygotic and postzygotic reproductive barriers; level and direction of gene flow; and the stability of hybrid zones in the face of climate change. The total number of plant hybrid zones detected in a literature search was surprisingly small （137）. This was the case even for areas of the world with a long history of research into plant evolution, ecology and systematics. Reasons for this are discussed, including the possibility that plant hybrid zones are naturally rare in the wild. Only for a few hybrid zones have attempts been made to distinguish between formation by primary intergradation or secondary contact, and it is assumed that most hybrid zones originate through secondary contact. From the limited information available, it appears that plant hybrid zones may frequently move in response to climate chan~e, but Ion~-term studies are required to confirm this.