Association of insularity to cloacal bacteria prevalence and body condition in a small shorebird

Do islands harbour less diverse disease communities than mainland? The island biogeography theory predicts more diverse communities on mainland than on islands due to more niches, more diverse habitats and availability of greater range of hosts. We compared bacteria prevalences of Campylobacter, Chlamydia and Salmonella in cloacal samples of a small shorebird, the Kentish plover (Charadrius alexandrinus) between two island populations of Macaronesia and two mainland locations in the Iberian Peninsula. Bacteria were found in all populations but, contrary to the expectations, prevalences did not differ between islands and mainland. Females had higher prevalences than males for Salmonella and when three bacteria genera were pooled together. Bacteria infection was unrelated to bird's body condition but females from mainland were heavier than males and birds from mainland were heavier than those from islands. Abiotic variables consistent throughout breeding sites, like high salinity that is known to inhibit bacteria growth, could explain the lack of differences in the bacteria prevalence between areas. We argue about the possible drivers and implications of sex differences in bacteria prevalence in Kentish plovers.

岛屿承载的疾病群落多样性是否低于大陆？岛屿生物地理学理论（Island Biogeography Theory）预测，大陆的群落多样性高于岛屿，原因在于大陆拥有更多生态位、更多样的生境以及更广范围的宿主类群。我们针对小型滨鸟环颈鸻（Charadrius alexandrinus）的泄殖腔样本，比较了其弯曲杆菌（Campylobacter）、衣原体（Chlamydia）与沙门氏菌（Salmonella）的感染率，采样对象涵盖马卡罗尼西亚的两个岛屿种群与伊比利亚半岛的两个大陆采样点。所有种群中均检出了细菌，但与理论预期相悖的是，岛屿与大陆的细菌感染率并无显著差异。雌性个体的沙门氏菌感染率，以及三种细菌属合并统计后的总感染率均高于雄性。细菌感染与鸟类的身体状况无关，但大陆种群的雌性个体体重高于雄性，且大陆种群的鸟类整体体重高于岛屿种群。整个繁殖生境中一致的非生物变量——例如已知可抑制细菌生长的高盐度环境——或可解释不同区域间细菌感染率无差异的现象。我们探讨了环颈鸻细菌感染率性别差异的潜在驱动因素与研究意义。