RESUMO
Traditionally, most studies have described the organization of host-parasite interaction networks by considering only few host groups at limited geographical extents. However, host-parasite relationships are merged within different taxonomic groups and factors shaping these interactions likely differ between host and parasite groups, making group-level differences important to better understand the ecological and evolutionary dynamics of these interactive communities. Here we used a dataset of 629 ectoparasite species and 251 species of terrestrial mammals, comprising 10 orders distributed across the Nearctic and Neotropical regions of Mexico to assess the species-level drivers of mammalian ectoparasite faunas. Specifically, we evaluated whether body weight, geographical range size and within-range mammal species richness (i.e. diversity field) predict mammal ectoparasite species richness (i.e. degree centrality) and their closeness centrality within the mammal-ectoparasite network. In addition, we also tested if the observed patterns differ among mammal orders and if taxonomic closely related host mammals could more likely share the same set of ectoparasites. We found that ectoparasite species richness of small mammals (mainly rodents) with large proportional range sizes was high compared to large-bodied mammals, whereas the diversity field of mammals had no predictive value (except for bats). We also observed that taxonomic proximity was a main determinant of the probability to share ectoparasite species. Specifically, the probability to share ectoparasites in congeneric species reached up to 90% and decreased exponentially as the taxonomic distance increased. Further, we also detected that some ectoparasites are generalists and capable to infect mammalian species across different orders and that rodents have a remarkable role in the network structure, being closely connected to many other taxa. Hence, because many rodent species have synanthropic habits they could act as undesired reservoirs of disease agents for humans and urban animals. Considering the reported worldwide phenomenon of the proliferation of rodents accompanying the demographic decrease or even local extinction of large-bodied mammal species, these organisms may already be an increasing health threat in many regions of the world.
Assuntos
Ectoparasitoses , Parasitos , Doenças dos Roedores , Animais , Ectoparasitoses/veterinária , Interações Hospedeiro-Parasita , Mamíferos , México , Doenças dos Roedores/epidemiologia , RoedoresRESUMO
PREMISE OF THE STUDY: Plant-herbivore networks are highly specialized in their interactions, yet they are highly variable with regard to the relative importance of specific host species for herbivores. How host species traits determine specialization and species strength in this antagonistic network is still an unanswered question that we addressed in this study. METHODS: We assessed plant cover and antiherbivore resistance traits to assess the extent to which they accounted for the variation in specialization and strength of interactions among species in a plant-herbivore network. We studied a tropical antagonistic network including a diverse herbivore-host plant assemblages in different habitat types and climatic seasons, including host plants with different life histories. KEY RESULTS: Particular combinations of leaf toughness, trichome density, and phenolic compounds influenced herbivore specialization and host species strength, but with a significant spatiotemporal variation among plant life histories. Conversely, plant-herbivore network parameters were not influenced by plant cover. CONCLUSIONS: Our study highlights the importance of species-specific resistance traits of plants to understand the ecological and evolutionary consequences of plant-herbivore interaction networks. The novelty of our research lies in the use of a trait-based approach to understand the variation observed in diverse plant-herbivore networks.
Assuntos
Ecossistema , Herbivoria , Folhas de Planta/fisiologia , Antibiose , Evolução Biológica , Cadeia Alimentar , Florestas , México , Densidade Demográfica , Estações do AnoRESUMO
Hosts and parasites interact with each other in a variety of ways, and this diversity of interactions is reflected in the networks they form. To test for differences in interaction patterns of ecto- and endoparasites we analysed subnetworks formed by each kind of parasites and their host fish species in fish-parasite networks for 22 localities. We assessed the proportion of parasite species per host species, the relationship between parasite fauna composition and host taxonomy, connectance, nestedness and modularity of each subnetwork (n = 44). Furthermore, we evaluated the similarity in host species composition among modules in ecto- and endoparasite subnetworks. We found several differences between subnetworks of fish ecto- and endoparasites. The association with a higher number of host species observed among endoparasites resulted in higher connectance and nestedness, and lower values of modularity in their subnetworks than in those of ectoparasites. Taxonomically related host species tended to share ecto- or endoparasites with the same interaction intensity, but the species composition of hosts tended to differ between modules formed by ecto- and endoparasites. Our results suggest that different evolutionary and ecological processes are responsible for organizing the networks formed by ecto- and endoparasites and fish.