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Nematode endoparasites do not codiversify with their stick insect hosts.

ABSTRACT: Host-parasite coevolution stems from reciprocal selection on host resistance and parasite infectivity, and can generate some of the strongest selective pressures known in nature. It is widely seen as a major driver of diversification, the most extreme case being parallel speciation in hosts and their associated parasites. Here, we report on endoparasitic nematodes, most likely members of the mermithid family, infecting different Timema stick insect species throughout California. The nematodes develop in the hemolymph of their insect host and kill it upon emergence, completely impeding host reproduction. Given the direct exposure of the endoparasites to the host's immune system in the hemolymph, and the consequences of infection on host fitness, we predicted that divergence among hosts may drive parallel divergence in the endoparasites. Our phylogenetic analyses suggested the presence of two differentiated endoparasite lineages. However, independently of whether the two lineages were considered separately or jointly, we found a complete lack of codivergence between the endoparasitic nematodes and their hosts in spite of extensive genetic variation among hosts and among parasites. Instead, there was strong isolation by distance among the endoparasitic nematodes, indicating that geography plays a more important role than host-related adaptations in driving parasite diversification in this system. The accumulating evidence for lack of codiversification between parasites and their hosts at macroevolutionary scales contrasts with the overwhelming evidence for coevolution within populations, and calls for studies linking micro- versus macroevolutionary dynamics in host-parasite interactions.

SUBMITTER: Larose C

PROVIDER: S-EPMC4984516 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Nematode endoparasites do not codiversify with their stick insect hosts.

Larose Chloé C Schwander Tanja T

Ecology and evolution 20160710 15

Host-parasite coevolution stems from reciprocal selection on host resistance and parasite infectivity, and can generate some of the strongest selective pressures known in nature. It is widely seen as a major driver of diversification, the most extreme case being parallel speciation in hosts and their associated parasites. Here, we report on endoparasitic nematodes, most likely members of the mermithid family, infecting different Timema stick insect species throughout California. The nematodes de ...[more]

PMID: 27551395

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Project description:Understanding how closely related wildlife species and their domesticated counterparts exchange or share parasites, or replace each other in parasite life cycles, is of great interest to veterinary and human public health, and wildlife ecology. Grey wolves (Canis lupus) host and spread endoparasites that can either directly infect canid conspecifics or their prey serving as intermediate hosts of indirectly transmitted species. The wolf recolonization of Central Europe represents an opportunity to study parasite transmission dynamics between wildlife and domestic species for cases when a definitive host returns after local extinction - a situation equivalent to a 'removal experiment'. Here we investigate whether the re-appearance of wolves has increased parasite pressure on hunting dogs - a group of companion animals of particular interest as they have a similar diet to wolves and flush wolf habitats when hunting. We compared prevalence (P) and species richness (SR) of helminths and the protozoan Sarcocystis to determine whether they were higher in hunting dogs from wolf areas (ndogs = 49) than a control area (ndogs = 29) without wolves. Of particular interest were S. grueneri and S. taeniata, known as 'wolf specialists'. Five helminth and 11 Sarcocystis species were identified, of which all helminths and eight Sarcocystis species were shared between dogs and wolves. Overall prevalence and species richness of helminths (P:38.5% vs. 24.1%; SRmean:0.4 vs. 0.3 species) and Sarcocystis (P:63.3% vs. 65.5%, SRmean:2.1 vs. 1.8 species) did not differ between study sites. However, hunting dogs were significantly more likely to be infected with S. grueneri in wolf areas (P:45.2% vs. 10.5%; p = 0.035). The findings suggest that wolves indirectly increase S. grueneri infection risk for hunting dogs since cervids are intermediate hosts and occasionally fed to dogs. Furthermore, a periodic anthelminthic treatment of hunting dogs may be an effective measure to control helminth infections regardless of wolf presence.

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Nematode endoparasites do not codiversify with their stick insect hosts.

Publications

Nematode endoparasites do not codiversify with their stick insect hosts.

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