Moore P J, Moore A J
School of Biological Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom.
Proc Natl Acad Sci U S A. 2001 Jul 31;98(16):9171-6. doi: 10.1073/pnas.161154598. Epub 2001 Jul 24.
Females are expected to have different mating preferences because of the variation in costs and benefits of mate choice both between females and within individual females over a lifetime. Workers have begun to look for, and find, the expected variation among females in expressed mating preferences. However, variation within females caused by changes in intrinsic influences has not been examined in detail. Here we show that reproductive aging caused by delayed mating resulted in reduced choosiness by female Nauphoeta cinerea, a cockroach that has reproductive cycles and gives live birth. Male willingness to mate was unaffected by variation in female age. Females who were beyond the optimal mating age, 6 days postadult molt, required considerably less courtship than their younger counterparts. Females who were older when they mated had fewer offspring per clutch and fewer clutches than females who mated young. Thus, reduced choosiness was correlated with a permanent reduction in fertility. There was no difference in overall senescence among females, and thus the reduction in clutch size did not result in the expected increased lifespan. We suggest that reproductive aging in N. cinerea, similar to aging in general, occurs because the maintenance of oocytes is costly, and selection is relaxed after the optimal mating period. Our results further suggest that selection for continued choosiness is also relaxed and supports direct selection on female choosiness and a cost to choosiness.
由于雌性之间以及单个雌性在其一生中择偶的成本和收益存在差异，预计雌性会有不同的交配偏好。研究人员已经开始寻找并发现了雌性在表达的交配偏好方面存在预期的差异。然而，由内在影响变化引起的雌性内部的差异尚未得到详细研究。在此，我们表明，延迟交配导致的生殖衰老会使灰褐瑙蛾（一种具有生殖周期且胎生的蟑螂）雌性的挑剔程度降低。雄性的交配意愿不受雌性年龄变化的影响。超过最佳交配年龄（成虫羽化后6天）的雌性比年轻雌性所需的求偶行为要少得多。交配时年龄较大的雌性每窝的后代数量比年轻交配的雌性少，窝数也更少。因此，挑剔程度的降低与生育能力的永久性下降相关。雌性之间的整体衰老没有差异，因此窝卵数的减少并没有导致预期的寿命延长。我们认为，灰褐瑙蛾的生殖衰老与一般衰老类似，是因为维持卵母细胞成本高昂，且在最佳交配期过后选择压力放松。我们的结果进一步表明，对持续挑剔的选择压力也会放松，并支持对雌性挑剔程度的直接选择以及挑剔的成本。
