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 effects）被认为可调控种群定殖的动态过程，尤其针对入侵物种。然而，针对寄生虫的阿利效应，在传染病定殖与传播的类似过程中却极少被纳入考量范畴。本研究历时四年，探究了体外寄生性鲑鱼虱（Lepeophtheirus salmonis）对未感染的野生幼年太平洋鲑鱼种群的定殖情况。基于涵盖67896尾鱼类的数据集，我们在1258只预成虫期雌性鲑鱼虱与611只成虫期雄性鲑鱼虱中，共观测到88次交配前配对行为。配对行为的发生概率与当地鲑鱼虱的种群密度相关，但雄性在宿主鱼类间的觅偶扩散行为，可在一定程度上缓解这种交配限制。结合本研究实证结果构建的大型寄生生物种群动态数学模型显示，种群统计学层面的阿利效应出现概率极高，该效应可导致定殖的寄生种群走向消亡。本研究结果或为大型寄生生物的阿利效应提供首个实证依据。此外，本数据集罕见地详细展现了定殖动态中的阿利效应特征，同时表明阿利效应或可抑制沿海海洋生态系统中寄生虫的传播范围。