Range expansion drives dispersal evolution in an equatorial three-species symbiosis.
Range expansion drives dispersal evolution in an equatorial three-species symbiosis.
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DOI：
10.1371/journal.pone.0005377
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发表时间：
2009
期刊：
影响因子：
3.7
通讯作者：
Kjellberg F
中科院分区：
文献类型：
--
作者：
Léotard G;Debout G;Dalecky A;Guillot S;Gaume L;McKey D;Kjellberg F
反复的气候振荡使物种分布发生了戏剧性的变化。这一过程被认为是一种主要的进化力量，塑造了物种的许多生活史特征，并在不同尺度上管理全球生物多样性格局。在射程扩张过程中，选择可能有利于高度分散的进化，并可能影响共生相互作用。有人认为，赤道纬度气候波动驱动的范围动力学的弱点促进了更多专门物种和相互作用的持续存在。然而，极少有人研究范围动态对物种的生物学和生态有多大的影响，特别是在赤道地区。我们研究了喀麦隆沿海赤道热带雨林特有的三种共生，在那里，范围动态的影响被认为是有限的，由两个物种特有的专职互助者--一种蚂蚁植物及其保护性蚂蚁--和这种互惠关系的物种特有的蚂蚁寄生虫组成。我们结合了物种内遗传多样性和在这个蚂蚁-植物系统的南部范围限制的样带中的表型变异的分析。这三个物种都呈现出近期逐渐向南扩张的一致的遗传特征，这一结果与现有的区域古气候数据相一致。正如预测的那样，这种扩张伴随着这两个蚂蚁物种更分散的特征的进化。相比之下，我们没有发现树上终生生殖策略发生变化的证据，也没有发现它对提供给共生蚂蚁的食物资源的投资。尽管互惠蚂蚁和寄生蚂蚁对保护工蚁的投入减少，对驱散雌性蚂蚁的投入增加，但没有证据表明殖民前线的共生关系不稳定。据我们所知，我们在这里提供了赤道纬度的第一个证据，表明与扩散相关的生物特征受到一组相互作用的物种范围扩展动态的影响。
Recurrent climatic oscillations have produced dramatic changes in species distributions. This process has been proposed to be a major evolutionary force, shaping many life history traits of species, and to govern global patterns of biodiversity at different scales. During range expansions selection may favor the evolution of higher dispersal, and symbiotic interactions may be affected. It has been argued that a weakness of climate fluctuation-driven range dynamics at equatorial latitudes has facilitated the persistence there of more specialized species and interactions. However, how much the biology and ecology of species is changed by range dynamics has seldom been investigated, particularly in equatorial regions. We studied a three-species symbiosis endemic to coastal equatorial rainforests in Cameroon, where the impact of range dynamics is supposed to be limited, comprised of two species-specific obligate mutualists –an ant-plant and its protective ant– and a species-specific ant parasite of this mutualism. We combined analyses of within-species genetic diversity and of phenotypic variation in a transect at the southern range limit of this ant-plant system. All three species present congruent genetic signatures of recent gradual southward expansion, a result compatible with available regional paleoclimatic data. As predicted, this expansion has been accompanied by the evolution of more dispersive traits in the two ant species. In contrast, we detected no evidence of change in lifetime reproductive strategy in the tree, nor in its investment in food resources provided to its symbiotic ants. Despite the decreasing investment in protective workers and the increasing investment in dispersing females by both the mutualistic and the parasitic ant species, there was no evidence of destabilization of the symbiosis at the colonization front. To our knowledge, we provide here the first evidence at equatorial latitudes that biological traits associated with dispersal are affected by the range expansion dynamics of a set of interacting species.
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影响因子：
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作者：
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通讯作者：
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