摘要
Group living can select for increased immunity, given the heightened risk of parasite transmission. Yet, it also may select for increased male reproductive investment, given the elevated risk of female multiple mating. Trade-offs between immunity and reproduction are well documented. Phenotypically, population density mediates both reproductive investment and immune function in the Indian meal moth, Plodia interpunctella. However, the evolutionary response of populations to these traits is unknown. We created two replicated populations of P. interpunctella, reared and mated for 14 generations under high or low population densities. These population densities cause plastic responses in immunity and reproduction: at higher numbers, both sexes invest more in one index of immunity [phenoloxidase (PO) activity] and males invest more in sperm. Interestingly, our data revealed divergence in PO and reproduction in a different direction to previously reported phenotypic responses. Males evolving at low population densities transferred more sperm, and both males and females displayed higher PO than individuals at high population densities. These positively correlated responses to selection suggest no apparent evolutionary trade-off between immunity and reproduction. We speculate that the reduced PO activity and sperm investment when evolving under high population density may be due to the reduced population fitness predicted under increased sexual conflict and/or to trade-offs between pre- and post-copulatory traits.
摘要译文
鉴于寄生虫传播的风险增加，小组生活可以选择增加免疫力。然而，它也可以选择增加男性生殖投资，鉴于女性多发交配的风险较高。免疫力和生殖权利之间的权衡是有据可查的。表型，人口密度介导了印度蛾蛾Plodia interpunctella的生殖投入和免疫功能。然而，人口对这些特征的进化反应是未知的。我们创造了两个重复种间的P.Papunctella，在高或低人口密度下饲养和交配14代。这些人口密度在免疫力和繁殖中引起塑性反应：数量越多，两性都投入更多的一个免疫指数[酚氧化酶（PO）活性]，男性更多地投入精子。有趣的是，我们的数据显示PO和生殖方向的差异与先前报告的表型反应不同。在人口密度较低的男性发展过程中，男性和女性的人口密度高于个体，PO高。这些与选择的正相关的反应表明免疫力和繁殖之间没有明显的进化权衡。在人口密度高的情况下演变的归属可能是由于性冲突增加预测的人口适应性下降和/或前后交配特征之间的权衡。
K. B. McNamara[*] and L. W. Simmons. Experimental evolution reveals differences between phenotypic and evolutionary responses to population density[J]. Journal of Evolutionary Biology, 2017,30(9): 1763-1771