Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America.
PLoS One. 2012;7(8):e42190. doi: 10.1371/journal.pone.0042190. Epub 2012 Aug 6.
Hosts and parasites co-evolve, with each lineage exerting selective pressures on the other. Thus, parasites may influence host life-history characteristics, such as longevity, and simultaneously host life-history may influence parasite diversity. If parasite burden causes increased mortality, we expect a negative association between host longevity and parasite species richness. Alternatively, if long-lived species represent a more stable environment for parasite establishment, host longevity and parasite species richness may show a positive association. We tested these two opposing predictions in carnivores, primates and terrestrial ungulates using phylogenetic comparative methods and controlling for the potentially confounding effects of sampling effort and body mass. We also tested whether increased host longevity is associated with increased immunity, using white blood cell counts as a proxy for immune investment. Our analyses revealed weak relationships between parasite species richness and longevity. We found a significant negative relationship between longevity and parasite species richness for ungulates, but no significant associations in carnivores or primates. We also found no evidence for a relationship between immune investment and host longevity in any of our three groups. Our results suggest that greater parasite burden is linked to higher host mortality in ungulates. Thus, shorter-lived ungulates may be more vulnerable to disease outbreaks, which has implications for ungulate conservation, and may be applicable to other short-lived mammals.
宿主和寄生虫共同进化，每个谱系都对另一个施加选择压力。因此，寄生虫可能会影响宿主的生活史特征，如寿命，而同时宿主的生活史也可能影响寄生虫的多样性。如果寄生虫负担导致死亡率增加，我们预计宿主寿命和寄生虫物种丰富度之间存在负相关关系。或者，如果长寿物种代表寄生虫建立的更稳定的环境，那么宿主寿命和寄生虫物种丰富度可能呈正相关。我们使用系统发育比较方法，在食肉动物、灵长类动物和陆生有蹄类动物中检验了这两种相反的预测，并控制了采样努力和体重等潜在混杂因素的影响。我们还测试了增加宿主寿命是否与增加免疫力有关，用白细胞计数作为免疫投资的替代指标。我们的分析显示，寄生虫物种丰富度与寿命之间存在微弱的关系。我们发现有蹄类动物的寿命和寄生虫物种丰富度之间存在显著的负相关关系，但在食肉动物或灵长类动物中没有显著的关联。我们在我们的三个群组中都没有发现免疫投资与宿主寿命之间存在关系的证据。我们的研究结果表明，寄生虫负担的增加与有蹄类动物更高的死亡率有关。因此，寿命较短的有蹄类动物可能更容易受到疾病爆发的影响，这对有蹄类动物的保护具有重要意义，并且可能适用于其他寿命较短的哺乳动物。
