Parasite diversity of disease-bearing rodents of Southeast Asia: habitat determinants and effects on sexual size dimorphism and life-traits

International audienceWe investigated a causal chain of relationships between habitat specialization and parasite species richness in rodent communities in Southeast Asia, and the consequences for variation in immune investment (using spleen size), the degree of sexual competition (using testes) and sexual size dimorphism (SSD). We used data gathered on rodents, their habitat specialization and their parasites (macro- and micro-parasites) in Southeast Asian landscapes. The results supported the hypotheses that parasite diversity drives the evolution of host life-traits and sexual selection. Firstly, host habitat specialization explained the variation in parasite species richness. Secondly, high parasite species richness was linked to host immune investment, using the relative spleen size of rodents. Thirdly, according to the potential costs associated with immune investment, the relative spleen size was found to be negatively correlated with the relative size of testes among rodents. Fourthly, a positive relationship between male-biased SSD and parasite species richness was observed supporting the role of parasitism in sexual selection. Finally, the variation in SSD was positively associated with the degree of habitat specialization. Highest values of female-biased SSD were associated with habitat specialization, whereas highest values of male-biased SSD concerned synanthropic or generalist rodent species. These results, also correlative, will help to facilitate selection of the species that should be thoroughly investigated at the population level to better understand the selective effects of parasites on rodent life-history and behavior

Infestations parasitaires multiples (polyparasitisme) chez les mammifères sauvages (approche comparative des déterminants et des impacts évolutifs)

Même si la majorité des études théoriques ou empiriques se sont essentiellement focalisées sur des interactions impliquant un seul hôte et un seul parasite, le polyparasitisme est la règle en milieu naturel chez les mammifères.Les déterminants potentiels de la richesse parasitaire (nombre d'espèces de parasites hébergés par un hôte), mais aussi les possibles impacts de ces multiples espèces de parasites sur les hôtes sont encore largement méconnus. En effet, les nombreuses études préexistantes sur les déterminants ont souvent été réalisées dans un cadre conceptuel trop étroit avec des données souvent restreintes à certaines zones faunistiques. Nous avons donc étendu les données et reconsidéré certains déterminants classiques (tels la latitude, la taille du groupe ou encore la taille du domaine vital pour l'ensemble des mammifères).Nous en avons également proposé de nouveaux, tels la socialité chez les rongeurs ou la nature des gîtes chez les chauves souris. Les travaux relatifs aux impacts de la diversité en tant que telle sont par contre peu nombreux et récents. Nous avons donc tenté de les appréhender à différents niveaux (immunité, métabolisme et traits de vie). En établissant les effets cumulatifs des infestations multiples, tels une augmentation de l'investissement immun ou du métabolisme basal, notre travail renforce l'idée récente et encore largement sous estimée que la diversité parasitaire puisse être un facteur de pression par elle-même sur les hôtes.Despite most sudies related to host- parasite relationships have focused on single host /single parasite systems, polyparasitism (i.e.multiple parasitic infestations or polyparasitism) is the law in natural systems at individual, populational or species level. Importantly however, may open questions arise from the reality of polyparasitism. Among them, those related to the potential impacts of parasitic diversity per se but also to the determinants of this parasitic diversity need to be furtfher explored. Infortunately, studies related to the impacts or coinfectiosn are still scarce. Moreover, the numerous available investigations of determinants may have largely suffered from a too narrow conceptual framework, leading to erroneous or naive predictrions. Focusing on macroparasites and using comparative phylogenetic approach across wild mammal species, we have then reinvestigated the determinants of parasitic diversity, notably revisiting classical determinants such as group size home range size or latitude but also exploring understudied ones such as roosting ecology of bats or sociality of rodents. The impacts of parasitic diversity have mainly been approached in our study by focusing on mammals' responses at immune, metabolic or life history trait levels. We have then found strong support for cumulative effects of polyparasitism at metabolic and immune levelsMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Parasite diversity of disease-bearing rodents of Southeast Asia: habitat determinants and effects on sexual size dimorphism and life-traits

We investigated a causal chain of relationships between habitat specialization and parasite species richness in rodent communities in Southeast Asia, and the consequences for variation in immune investment (using spleen size), the degree of sexual competition (using testes) and sexual size dimorphism (SSD). We used data gathered on rodents, their habitat specialization and their parasites (macro- and micro-parasites) in Southeast Asian landscapes. The results supported the hypotheses that parasite diversity drives the evolution of host life-traits and sexual selection. Firstly host habitat specialization explained the variation in parasite species richness. Secondly high parasite species richness was linked to host immune investment, using the relative spleen size of rodents. Thirdly according to the potential costs associated with immune investment, the relative spleen size was found to be negatively correlated with the relative size of testes among rodents. Fourthly, a positive relationship between male-biased SSD and parasite species richness was observed supporting the role of parasitism in sexual selection. Finally, the variation in SSD was positively associated with the degree of habitat specialization. Highest values of female-biased SSD were associated with habitat specialization, whereas highest values of male-biased SSD concerned synanthropic or generalist rodent species. These results, also correlative, will help to facilitate selection of the species that should be thoroughly investigated at the population level to better understand the selective effects of parasites on rodent life-history and behavior

Helminth species diversity of mammals: parasite species richness is a host species attribute

International audienceStudies investigating parasite diversity have shown substantial geographical variation in parasite species richness. Most of these studies have, however, adopted a local scale approach, which may have masked more general patterns. Recent studies have shown that ectoparasite species richness in mammals seems highly repeatable among populations of the same mammal host species at a regional scale. In light of these new studies we have reinvestigated the case of parasitic helminths by using a large data set of parasites from mammal populations in 3 continents. We collected homogeneous data and demonstrated that helminth species richness is highly repeatable in mammals at a regional scale. Our results highlight the strong influence of host identity in parasite species richness and call for future research linking helminth species found in a given host to its ecology, immune defences and potential energetic trade-offs

Parasite diversity: an overlooked metric of parasite pressures?

International audienc

Bat fly species richness in Neotropical bats: correlations with host ecology and host brain

International audiencePatterns of ectoparasite species richness in mammals have been investigated in various terrestrial mammalian taxa such as primates, ungulates and carnivores. Several ecological or life traits of hosts are expected to explain much of the variability in species richness of parasites. In the present comparative analysis we investigate some determinants of parasite richness in bats, a large and understudied group of flying mammals, and their obligate blood-sucking ectoparasite, streblid bat flies (Diptera). We investigate the effects of host body size, geographical range, group size and roosting ecology on the species richness of bat flies in tropical areas of Venezuela and Peru, where both host and parasite diversities are high. We use the data from a major sampling effort on 138 bat species from nine families. We also investigate potential correlation between bat fly species richness and brain size (corrected for body size) in these tropical bats. We expect a relationship if there is a potential energetic trade-off between costly large brains and parasite-mediated impacts. We show that body size and roosting in cavities are positively correlated with bat fly species richness. No effects of bat range size and group size were observed. Our results also suggest an association between body mass-independent brain size and bat fly species richness

Transmission ecology of rodent-borne diseases: New frontiers

International audienceRodents are recognized reservoir hosts for many human zoonotic pathogens. The current trends resulting from anthropocene defaunation suggest that in the future they, along with other small mammals, are likely to become the dominant mammals in almost all human‐modified environments. Recent intricate studies on bat‐borne emerging diseases have highlighted that many gaps exist in our understanding of the zoonotic transmission of rodent‐borne pathogens. This has emphasized the need for scientists interested in rodent‐borne diseases to integrate rodent ecology into their analysis of rodent‐borne pathogen transmission in order to identify in more detail the mechanisms of spillover and chains of transmission. Further studies are required to better understand the true impact of rodent abundance and the importance of pathogen sharing and circulation in multi‐host– multi‐pathogen communities. We also need to explore in more depth the roles of generalist and abundant species as the potential links between pathogen‐sharing, co‐infections and disease transmission