REU: Life History Evolution in Trinidadian Guppies (Poecilia reticulata)

动物生活史的各个方面都有巨大的多样性，包括成熟年龄、繁殖频率、后代的数量和大小，以及父母在个体后代上投入的努力。物种间和物种内的这些差异是由哪些环境因素选择的？拟议研究的目的是评估特定环境影响对特立尼达岛上孔雀鱼自然种群生活史进化的作用。特立尼达北部地区孔雀鱼自然种群的生活史差异与捕食行为的差异有关。与梭鱼cichlid Crenicichla Alta和其他捕食者共生的孔雀鱼成熟得更早，将更多的可用资源用于繁殖，而且往往比只与剑鱼riverus harti共生的孔雀鱼繁殖的后代更多、更小。Crenicichla和一些相关的捕食者物种主要捕食大型、性成熟大小的孔雀鱼。主要捕食体型较小、未成熟的孔雀鱼。这些捕食者的大小特异性表明，它们通过改变孔雀鱼特定年龄的存活来选择生活史上的变化。通过捕食大型孔雀鱼，Crenicichla应该会降低成年鱼的存活率。通过捕食小型孔雀鱼，小溪鱼应该会降低幼体的存活率。这种年龄差异对生活史进化的影响已经从理论上进行了研究；生活史进化中预测的反应与观察到的Crenicichla和Riverus地点之间的差异完全一致。拟议研究中的关键野外实验涉及将孔雀鱼和孔雀鱼捕食者引入以前被瀑布排除在外的溪流部分。捕食者和环境的影响，尤其是资源的可获得性，将通过对生长和存活的直接观察，以及使用耳石对生长和存活的间接估计来评估。耳石是内耳中的骨状结构，记录着每日的年轮，类似于树干横截面上常见的年轮。

There is enormous diversity in every aspect of animal life histories, including the age at maturity, frequency of reproduction, number and size of offspring, and the effort invested by parents in individual offspring. What factors in the environment selected for these differences among and within species? The goal of the proposed research is to evaluate the role of specific environmental influences on life history evolution of natural populations of guppies on the island of Trinidad. Natural populations of guppies from the Northern Range of Trinidad have life history differences associated with differences in predation. Guppies that co-occur with the pike cichlid Crenicichla alta and other predators mature at an earlier age, devote more of their available resources to reproduction, and tend to produce more and smaller offspring than guppies that co-occur with just the killifish Rivulus harti. Crenicichla and some of the associated species of predators prey predominantly on large, sexually mature size classes of guppies. Rivulus prey predominantly on small, immature size classes of guppies. The size specificity of these predators suggests that they select for life history changes by altering the age-specific survival of guppies. By preying on large guppies, Crenicichla should reduce adult survival. By preying on small guppies, Rivulus should reduce juvenile survival. The influence of such differences in age-specific survival on life history evolution has been investigated theoretically; the predicted responses in life history evolution correspond precisely with the differences observed between Crenicichla and Rivulus localities. The key field experiments in the proposed research involve introducing guppies and guppy predators into sections of stream where they had previously been excluded by waterfalls. The effects of predators and the environment, most notably resource availability, will be evaluated with direct observations of growth and survival, plus indirect estimates of growth and survival using otolith. Otolith are bone-like structures in the inner ear which record daily rings, similar to the annual rings commonly seen in cross-sections of tree trunks.