Evolution of dispersal and life history strategies -: Tetrahymena ciliates
Evolution of dispersal and life history strategies -: Tetrahymena ciliates
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DOI：
10.1186/1471-2148-7-133
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发表时间：
2007-08-06
影响因子：
3.4
通讯作者：
Clobert, Jean
中科院分区：
文献类型：
--
作者：
Fjerdingstad, Else J.;Schtickzelle, Nicolas;Clobert, Jean
背景：关于扩散和其他核心生活史策略(生殖努力、生存能力、定居能力)的选择如何可能导致所谓的扩散综合征，已经引起了相当多的关注。对这些综合征在物种内的遗传变异的研究可以重要地增加我们对它们进化的理解，通过揭示特征是否以理论模型预测的方式在遗传谱系中共同变化，并通过激发进一步的假设来进行实验测试。然而，这样的研究仍然很少。在这里，我们研究了纤毛原生动物嗜热四膜虫，这是一种特别有趣的有机体，因为细胞能够转变为游泳速度截然不同的形态。我们研究了在10个不同克隆株中的扩散、形态反应、繁殖性能和存活率。然后，我们考察了不同品系的生活史性状是否像经典预测的那样存在协变性，考察了不同品系在短距离和假定的长距离扩散中的投资，同时还考虑了半社会性(细胞聚集、‘生长因子’的分泌)对扩散策略的可能影响。结果：品系间在扩散速率、形态承诺和可塑性方面存在非常显著的差异，几乎所有核心生活史性状(如生存、生长性能和策略)都存在显著的相关性。一些菌株表现出较高的短程传播率、较高的定植能力、较大的细胞体积、较高的生长性能和较好的生存能力。然而，这些表现良好的菌株在环境退化时产生的快速游动的扩散形态比在正常条件下表现较差的亲水性菌株要少。结论：发现了嗜热性毛虫扩散策略和核心生活史性状之间存在遗传协同变异的有力证据，与经典的定殖者模型符合观察到的性状关联。然而，表现良好的菌株具有较高的定植成功率和较短的传播距离，可能会受到远距离传播劣势的影响，这是因为与亲水性菌株相比，它们产生的快游扩散形态较少。后两个品系的细胞体积较小，承载能力较强，作为单个细胞定居的能力较差，这表明它们可能适应了对克隆配偶的更高程度的依赖(更强的社会性)。总而言之，对竞争和合作能力的不同选择，加上专门针对传播距离的选择因素，可能对形成嗜热线虫的传播和生活史进化起到了重要作用。
Background: Considerable attention has focused on how selection on dispersal and other core life-history strategies (reproductive effort, survival ability, colonization capacity) may lead to so-called dispersal syndromes. Studies on genetic variation in these syndromes within species could importantly increase our understanding of their evolution, by revealing whether traits co-vary across genetic lineages in the manner predicted by theoretical models, and by stimulating further hypotheses for experimental testing. Yet such studies remain scarce. Here we studied the ciliated protist Tetrahymena thermophila, a particularly interesting organism due to cells being able to transform into morphs differing dramatically in swim-speed. We investigated dispersal, morphological responses, reproductive performance, and survival in ten different clonal strains. Then, we examined whether life history traits co-varied in the manner classically predicted for ruderal species, examined the investment of different strains into short- and putative long-distance dispersal, while considering also the likely impact of semi-sociality (cell aggregation, secretion of 'growth factors') on dispersal strategies.Results: Very significant among-strain differences were found with regard to dispersal rate, morphological commitment and plasticity, and almost all core life-history traits (e. g. survival, growth performance and strategy), with most of these traits being significantly intercorrelated. Some strains showed high short- distance dispersal rates, high colonization capacity, bigger cell size, elevated growth performance, and good survival abilities. These well performing strains, however, produced fewer fast-swimming dispersal morphs when subjected to environmental degradation than did philopatric strains performing poorly under normal conditions.Conclusion: Strong evidence was found for a genetic covariation between dispersal strategies and core life history traits in T. thermophila, with a fair fit of observed trait associations with classic colonizer models. However, the well performing strains with high colonization success and short- distance dispersal likely suffered under a long-distance dispersal disadvantage, due to producing fewer fast-swimming dispersal morphs than did philopatric strains. The smaller cell size at carrying capacity of the latter strains and their poor capacity to colonize as individual cells suggest that they may be adapted to greater levels of dependency on clone-mates (stronger sociality). In summary, differential exposure to selection on competitive and cooperative abilities, in conjunction with selective factors targeting specifically dispersal distance, likely contributed importantly to shaping T. thermophila dispersal and life history evolution.