Dugas M B, Moore M P, Martin R A, Richards-Zawacki C L, Sprehn C G
Department of Biology, Case Western Reserve University, Cleveland, OH, USA.
Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, LA, USA.
J Evol Biol. 2016 Oct;29(10):1977-1985. doi: 10.1111/jeb.12921. Epub 2016 Jul 6.
Offspring quantity and quality are components of parental fitness that cannot be maximized simultaneously. When the benefits of investing in offspring quality decline, parents are expected to shift investment towards offspring quantity (other reproductive opportunities). Even when mothers retain complete control of resource allocation, offspring control whether to allocate investment to growth or development towards independence, and this shared control may generate parent-offspring conflict over the duration of care. We examined these predictions by, in a captive colony, experimentally removing tadpoles of the strawberry poison frog (Oophaga pumilio) from the mothers that provision them with trophic eggs throughout development. Tadpoles removed from their mothers were no less likely to survive to nutritional independence (i.e. through metamorphosis) than were those that remained with their mothers, but these offspring were smaller at metamorphosis and were less likely to survive to reach adult size, even though they were fed ad libitum. Tadpoles that remained with their mothers developed more slowly than those not receiving care, a pattern that might suggest that offspring extracted more care than was in mothers' best interests. However, the fitness returns of providing care increased with offspring development, suggesting that mothers would be best off continuing care until tadpoles initiated metamorphosis. Although the benefits of parental investment in offspring quality are often thought to asymptote at high levels, driving parent-offspring conflict over weaning, this assumption may not hold over natural ranges of investment, with selection on both parents and offspring favouring extended durations of parental care.
后代数量和质量是亲代适合度的组成部分，无法同时最大化。当投资于后代质量的益处下降时，预计亲代会将投资转向后代数量（其他繁殖机会）。即使母亲完全控制资源分配，后代也能控制是否将投资分配到生长或向独立发育，这种共同控制可能会在抚育持续时间上引发亲代与子代之间的冲突。我们通过在一个圈养群体中，实验性地将草莓箭毒蛙（Oophaga pumilio）的蝌蚪从在其整个发育过程中为其提供营养卵的母亲身边移走，来检验这些预测。从母亲身边移走的蝌蚪存活到营养独立（即变态）的可能性并不比留在母亲身边的蝌蚪低，但这些后代在变态时体型较小，并且即使自由进食，存活到成年体型的可能性也较小。留在母亲身边的蝌蚪发育比未接受抚育的蝌蚪更慢，这种模式可能表明后代获取的抚育超过了母亲的最佳利益。然而，提供抚育的适合度回报随着后代发育而增加，这表明母亲最好持续抚育直到蝌蚪开始变态。尽管通常认为亲代对后代质量的投资益处会在高水平时趋于平稳，从而引发关于断奶的亲代与子代冲突，但在自然投资范围内，这一假设可能不成立，因为对亲代和子代的选择都有利于延长亲代抚育的持续时间。
