Asexual freshwater snails make poor mate choice decisions

Once-useful traits that no longer contribute to fitness tend to decay over time. We address whether the expression of mating-related traits that increase the fitness of sexually reproducing individuals but are likely less useful or even costly to asexual counterparts seems to exhibit decay in the latter. Potamopyrgus antipodarum is a New Zealand freshwater snail characterized by repeated transitions from sexual to asexual reproduction. The frequent coexistence of sexual and asexual lineages makes P. antipodarum an excellent model for the study of mating-related trait loss. We used a mating choice assay including sexual and asexual P. antipodarum females and conspecific (presumed better choice) vs. heterospecific (presumed worse choice) males to evaluate the loss of behavioural traits related to sexual reproduction. We found that sexual females engaged in mating behaviours with conspecific mating partners more frequently and for a greater duration than with heterospecific mating partners...

曾经具备适应功能、但不再对适合度（fitness）产生贡献的性状，往往会随时间推移逐渐退化。我们旨在探究：那些可提升有性繁殖个体适合度、但对无性繁殖类群而言大概率无用甚至代价高昂的交配相关性状，是否会在无性类群中出现退化现象。放射拟沼螺（Potamopyrgus antipodarum）是一种新西兰淡水螺，其特征为反复经历从有性繁殖向无性繁殖的转变。有性与无性谱系的频繁共存，使得该物种成为研究交配相关性状丢失的理想模型。我们采用交配选择实验，分别设置有性与无性雌性放射拟沼螺，并以同种（被视为更优选择）与异种（被视为较劣选择）雄性作为交配对象，以此评估有性繁殖相关行为性状的丢失情况。实验结果显示，相较于异种交配对象，有性雌性个体与同种交配伴侣进行交配行为的频率更高、持续时间更长……