孤雌繁殖轮虫生活史对策中母体效应的作用的研究

Maternal effect, which may accelerate or restrain the evolution process, is an important driving source of adaptive life history variation and evolutionary dynamics. Therefore, it has become the focus of numerous evolutionary studies in recent years. The cyclical parthenogenesis monogonont rotifers, with short life span and remarkable phenotypic plasticity, often show high clone diversity in life history strategies in the same population. Moreover, sympatric cryptic species have been found in both well studied rotifer species Brachionus plicatilis and B. calyciflorus. Although maternal effect is one of the important factors that result in variations in the offspring's life history strategy, there are few reports published reveal systematically and clearly the role of maternal effect played on life history strategy, especially on its transgenerational plasticity and ultimate speciation. The present project intends to explore the following scientific questions: 1 Which characters in life history strategy are most likely to be susceptible to materal effects? 2 Which habitat factors such as temperature, food, predators etc. that the mother experienced are most likely to influence maternal control? 3 Is maternal age has a influence on life history strategies of the offspring populations? 4 How many generations the maternal effect can go through and how about its possible evolutional significance? 5 Can the 'Delayed mixis hypothesis be demonstrated experimentally and why the rotifers evolved the strategy of 'Delayed mixis'? These results may provide basic data for an insight understanding into the adaptive evolution of monogonont rotifers and the role that maternal effects may play in evolution of rotifers.

母体效应可加速或抑制生物的进化历程，是生物生活史对策变异的主要驱动因素之一,已成为近年进化生物学关注热点。营周期性孤雌繁殖的单巢类轮虫，世代周期短，表型可塑性强，同一种群内不同克隆群的生活史对策具有很高的多样性，且存在同域隐种共存现象。在单巢类轮虫生活史对策的高多样性及隐种形成、同域共存现象中，母体效应到底发挥着怎样的作用？该方面的系统研究还很少。本项目拟结合实验种群生态学与分子标记技术，探讨如下科学问题：（1）轮虫生活史性状中哪些表型更易受母体效应的影响？（2）母体所经历的温度、食物、捕食者等生境要素中哪些要素更易导致母体效应？（3）母体年龄对后代种群生活史对策有何影响? （4）母体效应可持续多少代？其累积效应及跨代传递有何进化意义？（5）对延迟的有性繁殖理论假说进行实验生物学论证。项目研究成果可为人们深入了解周期性孤雌繁殖轮虫生活史适应进化及母体效应在进化中的作用提供重要基础数据。

母体效应是导致生物进化适应的生活史对策变异的主要驱动因素之一。本项目针对诱导母体效应发生的主要生态要素、敏感表型、跨代及叠加效应等科学问题，系统探讨了萼花臂尾轮虫母体效应的特点及其功能作用,获得主要结果如下：①种群遗传结构季节变化明显， 69个单倍型形成6世系，遗传距离0.023-0.260，含4隐种；不同隐种SLAF测序共形成1,318,771个SLAF标签, 66,392个SNP位点。②母体(F0)经历的环境温度（T）、PH、种群密度(D)、捕食者 (P)、食物等外因和母体年龄(MA)等内因要素对后代的影响各不相同，其中最主要的是T、P、D和MA；而子代母体效应响应的敏感性状有卵大小、体大小、侧棘刺长（sl）等表型和混交雌体比率(mr)、有性繁殖阈值(stv)、初次性成熟时间(fmt)与内禀增长率(rm)。F0经历的T与其卵大小和子代F1体大小成反比，生活在类似F0环境T下的F1具有更高的适合度。母体环境中的捕食者密度信号（P）高低对子代表型及生活史性状影响广泛。有P经历F0，其F1的stv显著降低，mr提高，且生命周期早期(YF1)mr高于晚期（OF1）mr。无P环境下，有P经历F0的后代F1的fmt较对照显著延长，但繁殖力，世代周期，rm和成活率等生活史性状参数没显著差异。有P经历混交雌体F0所产休眠卵es显著减小；其干雌体F1的fmt在无P环境下较对照显著缩短。不同母体类型（干雌体 vs 非混交雌体）和是否经历P对子代面临不同强度P信号时sl的变化影响显著。取食小体型食物的F0，其后代bs也减小。经历高种群密度（HD）的F0，其F1数量显著低于对照，但种群的mr显著高于对照；F0经历低性比环境，会降低F1的mr。低密度环境（LD）下MA不影响F1的mr；但HD下，F0早期（YF0）所产F1中mr显著高于晚期(OF0)所产F1，且YF0的孙代F2的 mr仍显著高于OF0 F2的 mr。③母体效应的传代效应随诱导因素和子代响应性状的不同而不同，在HD下MA诱导的后代mr响应可传2代，而P诱导的防御体型响应在干雌体仅可传递一代；但P持续环境下母体效应叠加作用显著， 30个世代后，子代的防御体型和响应模式发生明显变化。④ “延迟的有性生殖”假说的实验生物学验证出现分异结果。上述成果显示叠加的母体效应在生态位分化和多样性维持，种群调节中发挥着重要作用。