Post-fire response and genetic diversity in Erica coccinea: connecting population dynamics and diversification in a biodiversity hotspot

Understanding the proceses of biological diversification is a central topic in evolutionary biology. The South African Cape fynbos, one of the major plant biodiversity hotspots out of the tropics, has prompted several hypotheses about the causes of generation and maintenance of biodiversity. Fire has been traditionally invoked as a key element to explain high levels of biodiversity in highly speciose fynbos taxa, such as the genus Erica. In this study, we have implemented a microevolutionary approach to elucidate how plant-response to fire may contribute to explain high levels of diversification in Erica. By using microsatellite markers, we investigated the genetic background of seeder (fire-sensitive) and resprouter (fire-resistant) populations of the fynbos species Erica coccinea. We found higher within-population genetic diversity and higher among-population differentiation in seeder populations and interpreted these higher levels of genetic diversification as a consequence of the comparatively shorter generation times and faster population turnover in the seeder form of this species. Considering that genetic divergence among populations may be seen as the initial step to speciation, the parallelism between these results and the pattern of biodiversity at the genus level offers stimulating insights into understanding causes of speciation of the genus Erica in the Cape fynbos.

解析生物多样化过程是进化生物学的核心议题。南非开普凡波斯（Fynbos）是热带以外的主要陆地生物多样性热点区域之一，该区域催生了多项关于生物多样性产生与维持机制的假说。长期以来，火被视为解释物种丰富的凡波斯类群（如欧石楠属（Erica））高生物多样性水平的关键因素。本研究采用微进化研究方法（microevolutionary approach），旨在阐明植物对火的响应机制如何助力解释欧石楠属极高的物种多样化水平。研究借助微卫星标记（microsatellite markers），对开普凡波斯物种红花欧石楠（Erica coccinea）的种子萌发型（火敏感型）与萌芽更新型（耐火型）种群的遗传背景展开了调查。结果发现，种子萌发型种群具有更高的种群内遗传多样性以及更高的种群间遗传分化；我们将这类更高水平的遗传多样化归因于该物种种子萌发型种群相对更短的世代时长与更快的种群更新速率。鉴于种群间的遗传分化可被视为物种形成的初始步骤，本研究结果与欧石楠属生物多样性格局的一致性，为理解开普凡波斯区域内欧石楠属的物种形成机制提供了极具启发性的见解。