The Course of Evolution When Selection For A Behavioral Adaption Is Relaxed: Host Defenses Against Parasitic Birds

一些鸟类，如牛头鸟和杜鹃，并不照顾自己的幼鸟，而是通过在宿主的巢中产卵来寄生其他鸟类的父母的努力。这种群居或“幼虫寄生”抑制了寄主的生殖产出，一些寄主已经进化出防御措施，例如清除寄生的卵。这项研究将确定鸟类在不再被寄生时保留宿主防御的程度，方法是对目前未被寄生的种群进行卵识别实验，并通过评估DNA序列差异的水平来估计自这些种群摆脱幼虫寄生以来所经过的时间。在缺乏益处的情况下，是否保留一种适应是进化生物学的一个基本问题。保持适应的问题对于努力理解人性也是至关重要的，因为过去适应但今天不再有益的行为倾向可能仍然会被表达出来，往往对社会有害。幼虫寄生对保护生物多样性的努力具有重要意义，因为一些濒临灭绝的寄主物种受到寄生损失的影响。目前，至少有六个濒危物种受到牛鸟控制计划的保护，这些计划花费了大量的公共资金。了解在没有任何好处的情况下卵子识别被保留的程度将揭示这种特征是否有显著的成本，并将为一些濒危宿主没有产生这种行为的原因提供洞察。

Some birds, such as cowbirds and cuckoos, do not care for their own young but instead parasitize the parental efforts of other birds, their hosts, by laying their eggs in the hosts' nests. This social or "brood parasitism" depresses host reproductive output and some hosts have evolved defenses, such as removal of parasitic eggs. This study will determine the extent to which bird species retain host defenses when they are no longer parasitized by carrying out egg recognition experiments on populations that are not currently parasitized and by assessing levels of DNA sequence divergence to estimate the elapsed time since such populations became free of brood parasitism. Whether an adaptation is retained in the absence of benefits is a fundamental question in evolutionary biology. The issue of the retention of adaptations is also vital to efforts to understand human nature as behavioral tendencies that were adaptive in the past but are no longer beneficial today may still be expressed, often to the detriment of society. Brood parasitism is significant to efforts to preserve biodiversity because some endangered host species are impacted by the losses suffered to parasitism. Currently, at least six endangered species are protected from parasitism by cowbird control programs that expend significant amounts of public funds. Understanding the extent to which egg recognition is retained in the absence of any benefits will reveal whether this trait has significant costs and will provide insights into the reasons some endangered hosts have not developed this behavior.