Data from: Allee effects may slow the spread of parasites in a coastal marine ecosystem

Allee effects are thought to mediate the dynamics of population colonization, particularly for invasive species. However, Allee effects acting on parasites have rarely been considered in the analogous process of infectious disease establishment and spread. We studied the colonization of uninfected wild juvenile Pacific salmon populations by ectoparasitic salmon lice (Lepeophtheirus salmonis) over four years. From a dataset of 67,896 fish, we observed 88 occurrences of pre-copular pair formation among 1258 pre-adult female and 611 adult male lice. The probability of pair formation was dependent on the local abundance of lice, but this mate limitation is likely offset somewhat by mate-searching dispersal of males among host fish. A mathematical model of macroparasite population dynamics that incorporates the empirical results suggests a high likelihood of a demographic Allee effect, which can cause the colonizing parasite populations to die out. These results may provide the first empirical evidence for Allee effects in a macroparasite. Furthermore, the data give a rare detailed view of Allee effects in colonization dynamics and suggest that Allee effects may dampen the spread of parasites in a coastal marine ecosystem.阿利效应（Allee effect）被认为可调控种群定殖的动态过程，对于入侵物种而言尤为如此。然而，在传染病定殖与传播的类似过程中，针对寄生虫的阿利效应却极少被纳入研究范畴。我们历时四年，针对体外寄生鲑鱼虱（Lepeophtheirus salmonis）对未受感染的野生幼年太平洋鲑种群的定殖过程展开研究。基于涵盖67896尾鱼类的数据集，我们在1258只预成年雌性鲑虱与611只成年雄性鲑虱中，观测到88次交配前配对行为。配对形成的概率依赖于当地鲑虱的种群丰度，但这种配偶限制或许会因雄性在宿主鱼类间的配偶搜寻扩散得到一定程度的抵消。结合本研究实证结果构建的大型寄生虫（macroparasite）种群动态数学模型显示，种群存在极高概率出现人口统计学阿利效应，该效应可导致定殖的寄生虫种群走向灭绝。本研究结果或可为大型寄生虫类群中的阿利效应提供首个实证证据。此外，本次研究的数据罕见地详细展现了定殖动态中的阿利效应，并暗示阿利效应或许会抑制沿海海洋生态系统中寄生虫的传播扩散。