1 Centre for Evolutionary Biology, School of Biological Sciences, The University of Western Australia , Crawley, Western Australia 6009 , Australia.
2 Department of Biology, University of Padova , 35131 Padova , Italy.
Proc Biol Sci. 2019 Feb 27;286(1897):20182873. doi: 10.1098/rspb.2018.2873.
Traits associated with mating and fertilization success are expected to senesce with age, but limited information is available on their relative rates of senescence. In polyandrous species, male reproductive fitness depends on both mating and fertilization success. Because successful mating is a prerequisite for post-copulatory sexual selection, ejaculate traits are expected to senesce faster than pre-copulatory traits, as pre-copulatory sexual selection is often deemed to be stronger than post-copulatory sexual selection. This pattern has generally been found in the few empirical studies conducted so far. We tested this prediction in the guppy ( Poecilia reticulata), a livebearing fish characterized by intense sperm competition, by comparing the expression of male sexual traits at two ages (four and nine months). Contrary to prediction, we found that post-copulatory traits senesced at a significantly slower rate than pre-copulatory traits. We also looked at whether early investment in those sexual traits affects longevity, and the interaction between sperm age (duration of sperm storage inside the male) and male age. Our results suggest that the relative senescence rate of pre- and post-copulatory sexual traits may vary among species with different mating systems and ecology.
与交配和受精成功相关的特征预计会随着年龄的增长而衰老，但关于它们相对衰老速度的信息有限。在多配偶物种中，雄性生殖适应性取决于交配和受精的成功。因为成功的交配是进行交配后性选择的前提，所以精液特征预计会比交配前的特征衰老得更快，因为交配前的性选择通常被认为比交配后的性选择更强。到目前为止，在为数不多的实证研究中，已经普遍发现了这种模式。我们通过比较两种年龄（四个月和九个月）雄性性特征的表达，在食蚊鱼（ Poecilia reticulata）中测试了这一预测，食蚊鱼是一种具有强烈精子竞争的胎生鱼类。与预测相反，我们发现交配后特征的衰老速度明显慢于交配前特征。我们还研究了这些性特征的早期投资是否会影响寿命，以及精子年龄（雄性体内精子储存的时间）和雄性年龄之间的相互作用。我们的研究结果表明，不同交配系统和生态的物种的交配前和交配后性特征的相对衰老速度可能有所不同。
