Diaz S Anaid, Viney Mark
School of Biological Sciences, University of Bristol Tyndall Avenue, Bristol, BS8 1TQ, UK.
Ecol Evol. 2015 Mar;5(6):1343-53. doi: 10.1002/ece3.1436. Epub 2015 Mar 2.
Organisms can end up in unfavourable conditions and to survive this they have evolved various strategies. Some organisms, including nematodes, survive unfavourable conditions by undergoing developmental arrest. The model nematode Caenorhabditis elegans has a developmental choice between two larval forms, and it chooses to develop into the arrested dauer larva form in unfavourable conditions (specifically, a lack of food and high population density, indicated by the concentration of a pheromone). Wild C. elegans isolates vary extensively in their dauer larva arrest phenotypes, and this prompts the question of what selective pressures maintain such phenotypic diversity? To investigate this we grew C. elegans in four different environments, consisting of different combinations of cues that can induce dauer larva development: two combinations of food concentration (high and low) in the presence or absence of a dauer larva-inducing pheromone. Five generations of artificial selection of dauer larvae resulted in an overall increase in dauer larva formation in most selection regimes. The presence of pheromone in the environment selected for twice the number of dauer larvae, compared with environments not containing pheromone. Further, only a high food concentration environment containing pheromone increased the plasticity of dauer larva formation. These evolutionary responses also affected the timing of the worms' reproduction. Overall, these results give an insight into the environments that can select for different plasticities of C. elegans dauer larva arrest phenotypes, suggesting that different combinations of environmental cues can select for the diversity of phenotypically plastic responses seen in C. elegans.
生物体可能最终处于不利条件下，为了在这种情况下生存，它们进化出了各种策略。一些生物体，包括线虫，通过进入发育停滞来在不利条件下生存。模式线虫秀丽隐杆线虫在两种幼虫形态之间有发育选择，并且在不利条件下（具体来说，食物短缺和高种群密度，由一种信息素的浓度表示）它会选择发育成停滞的 dauer 幼虫形态。野生秀丽隐杆线虫分离株在其 dauer 幼虫停滞表型上有很大差异，这就引发了一个问题：是什么选择压力维持了这种表型多样性？为了研究这个问题，我们在四种不同环境中培养秀丽隐杆线虫，这些环境由可诱导 dauer 幼虫发育的不同线索组合组成：在存在或不存在 dauer 幼虫诱导信息素的情况下，食物浓度的两种组合（高和低）。对 dauer 幼虫进行五代人工选择导致在大多数选择方案中 dauer 幼虫形成总体增加。与不含有信息素的环境相比，环境中信息素的存在选择出的 dauer 幼虫数量是其两倍。此外，只有含有信息素的高食物浓度环境增加了 dauer 幼虫形成的可塑性。这些进化反应也影响了线虫繁殖的时间。总体而言，这些结果深入了解了可以选择秀丽隐杆线虫 dauer 幼虫停滞表型不同可塑性的环境，表明环境线索的不同组合可以选择秀丽隐杆线虫中所见的表型可塑性反应的多样性。
