Intraspecific ecological niche divergence and reproductive shifts foster cytotype displacement and provide ecological opportunity to polyploids
Intraspecific ecological niche divergence and reproductive shifts foster cytotype displacement and provide ecological opportunity to polyploids
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DOI：
10.1093/aob/mcy004
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发表时间：
2018-05-11
期刊：
影响因子：
4.2
通讯作者：
Hojsgaard, Diego
中科院分区：
文献类型：
--
作者：
Karunarathne, Piyal;Schedler, Mara;Hojsgaard, Diego
背景与目的多倍体与其低倍体祖体细胞之间的生态位分化是多倍体形成和适应性分化的主要机制之一。然而，在群落生态学和生物多样性分析中，种内染色体和生殖变异通常被忽视，尽管它们在谱系的适应性多样化中起着重要作用。方法利用具有不同遗传系统（二倍体与自多倍体、异亲和与自交配、性向与无融合）的雀稗（Paspalum intermedium），研究雀稗在生物地理格局、适应性和生态灵活性方面的因果关系。染色体计数和流式细胞术用于鉴定种内遗传系统的多样性。环境生态位模型用于评价与环境和气候因素相关的种内生态属性，并评估控制物种种群动态、范围扩张、适应和进化历史的倍性、繁殖方式和生态条件之间的相关性。结果两种非随机分布的优势细胞型在局部和区域地理尺度上表现出生态位分化、生态位最优的方向性转移以及与倍性相关的环境资源开发生态倾向的破坏性选择迹象。生态专一性异交二倍体存在于温度、湿度和生产力较高的北方地区，而通才性自交无杂交四倍体存在于温度较低、生产力较低的南方地区。4个有记录的倍性转移的地点和4个生态过渡区的混合种群显示细胞型之间的不均匀替换。结论多倍体性和不同细胞型间的生殖性状差异促进了生态位最优转移，增加了生态耐受性和生态位分化。生态特化的二倍体通过取代四倍体来维持核心地区的细胞型稳定性，而更广泛的生态偏好和从性向无融合的转变有利于多倍体在二倍体被取代的外围地区定植，并为同源四倍体提供了生态机会，支持范围扩大到开放的南方栖息地。
Background and Aims Niche divergence between polyploids and their lower ploidy progenitors is one of the primary mechanisms fostering polyploid establishment and adaptive divergence. However, within-species chromosomal and reproductive variability have usually been neglected in community ecology and biodiversity analyses even though they have been recognized to play a role in the adaptive diversification of lineages.Methods We used Paspalum intermedium, a grass species with diverging genetic systems (diploidy vs. autopolyploidy, allogamy vs. autogamy and sexuality vs. apomixis), to recognize the causality of biogeographic patterns, adaptation and ecological flexibility of cytotypes. Chromosome counts and flow cytometry were used to characterize within-species genetic systems diversity. Environmental niche modelling was used to evaluate intraspecific ecological attributes associated with environmental and climatic factors and to assess correlations among ploidy, reproductive modes and ecological conditions ruling species' population dynamics, range expansion, adaptation and evolutionary history.Key Results Two dominant cytotypes non-randomly distributed along local and regional geographical scales displayed niche differentiation, a directional shift in niche optima and signs of disruptive selection on ploidy-related ecological aptitudes for the exploitation of environmental resources. Ecologically specialized allogamous sexual diploids were found in northern areas associated with higher temperature, humidity and productivity, while generalist autogamous apomictic tetraploids occurred in southern areas, occupying colder and less productive environments. Four localities with a documented shift in ploidy and four mixed populations in a zone of ecological transition revealed an uneven replacement between cytotypes.Conclusions Polyploidy and contrasting reproductive traits between cytotypes have promoted shifts in niche optima, and increased ecological tolerance and niche divergence. Ecologically specialized diploids maintain cytotype stability in core areas by displacing tetraploids, while broader ecological preferences and a shift from sexuality to apomixis favoured polyploid colonization in peripheral areas where diploids are displaced, and fostered the ecological opportunity for autotetraploids supporting range expansion to open southern habitats.