Functional similarity affects similarity in partner composition in flea-mammal networks.

Functional signal in an interaction network is a phenomenon in which species resembling each other in their traits interact with similar partners. We tested the functional signal concept in realm-specific and regional flea-host networks from four biogeographic realms and asked whether the species composition of (a) host spectra and (b) flea assemblages is similar between functionally similar flea and host species, respectively. Analogously to testing for phylogenetic signal, we applied Mantel tests to investigate the correlation between flea or host functional distances calculated from functional dendrograms and dissimilarities in sets of interacting partners. In all realm-specific networks, functionally similar fleas tended to exploit similar hosts often belonging to the same genus, whereas functionally similar hosts tended to harbour similar fleas, again often belonging to the same genus. The strength of realm-specific functional signals and the frequency of detecting a significant functional signal in the regional networks differed between realms. The frequency of detecting a significant functional signal in the regional networks correlated positively with the network size for fleas and with the number of hosts in a network for hosts. A functional signal in the regional networks was more frequently found for hosts than for fleas. We discuss the mechanisms behind the functional signal in both fleas and their hosts, relate geographic functional signal patterns to the historic biogeography of fleas and conclude that functional signals in the species composition of host spectra for fleas and of flea assemblages for hosts result from the interplay of evolutionary and ecological processes.

Searching for common patterns in parasite ecology: species and host contributions to beta-diversity in helminths of South African ungulates and fleas of South American rodents.

We searched for common patterns in parasite ecology by investigating species and host contributions to the beta-diversity of infracommunities (=assemblages of parasites harboured by a host individual) in helminths of three species of South African ungulates and fleas of 11 species of South American rodents, assuming that a comparison of patterns in distinctly different parasites and hosts would allow us to judge the generality or, at least, commonness of these patterns. We used data on species' composition and numbers of parasites and asked whether (i) parasite species' attributes (life cycle, transmission mode, and host specificity in helminths; possession of sclerotized combs, microhabitat preference, and host specificity in fleas) or their population structure (mean abundance and/or prevalence) and (ii) host characteristics (sex and age) affect parasite and host species' contributions to parasite beta-diversity (SCBD and HCBD, respectively). We found that parasite species' morphological and ecological attributes were mostly not associated with their SCBD. In contrast, parasite SCBD, in both ungulates and rodents, significantly increased with either parasite mean abundance or prevalence or both. The effect of host characteristics on HCBD was detected in a few hosts only. In general, parasite infracommunities' beta-diversity appeared to be driven by variation in parasite species rather than the uniqueness of the assemblages harboured by individual hosts. We conclude that some ecological patterns (such as the relationships between SCBD and parasite abundance/prevalence) appear to be common and do not differ between different host-parasite associations in different geographic regions, whereas other patterns (the relationships between SCBD and parasite species' attributes) are contingent and depend on parasite and host identities.

Relationships between functional alpha and beta diversities of flea parasites and their small mammalian hosts.

We studied the relationships between functional alpha and beta diversities of fleas and their small mammalian hosts in 4 biogeographic realms (the Afrotropics, the Nearctic, the Neotropics and the Palearctic), considering 3 components of alpha diversity (functional richness, divergence and regularity). We asked whether (a) flea alpha and beta diversities are driven by host alpha and beta diversities; (b) the variation in the off-host environment affects variation in flea alpha and beta diversities; and (c) the pattern of the relationship between flea and host alpha or beta diversities differs between geographic realms. We analysed alpha diversity using modified phylogenetic generalized least squares and beta diversity using modified phylogenetic generalized dissimilarity modelling. In all realms, flea functional richness and regularity increased with an increase in host functional richness and regularity, respectively, whereas flea functional divergence correlated positively with host functional divergence in the Nearctic only. Environmental effects on the components of flea alpha diversity were found only in the Holarctic realms. Host functional beta diversity was invariantly the best predictor of flea functional beta diversity in all realms, whereas the effects of environmental variables on flea functional beta diversity were much weaker and differed between realms. We conclude that flea functional diversity is mostly driven by host functional diversity, whereas the environmental effects on flea functional diversity vary (a) geographically and (b) between components of functional alpha diversity.

Environment and traits affect parasite and host species positions but not roles in flea-mammal networks.

We studied spatial variation in the effects of environment and network size on species positions and roles in multiple flea-mammal networks from four biogeographic realms. We asked whether species positions (measured as species strength [SS], the degree of interaction specialization [d'], and the eigenvector centrality [C]) or the roles of fleas and their hosts in the interaction networks: (a) are repeatable/conserved within a flea or a host species; (b) vary in dependence on environmental variables and/or network size; and (c) the effects of environment and network size on species positions or roles in the networks depend on species traits. The repeatability analysis of species position indices for 441 flea and 429 host species, occurring in at least two networks, demonstrated that the repeatability of SS, d', and C within a species was significant, although not especially high, suggesting that the indices' values were affected by local factors. The majority of flea and host species in the majority of networks demonstrated a peripheral role. A value of at least one index of species position was significantly affected by environmental variables or network size in 41 and 36, respectively, of the 52 flea and 52 host species that occurred in multiple networks. In both fleas and hosts, the occurrence of the significant effect of environment or network size on at least one index of species position, but not on a species' role in a network, was associated with some species traits.

Host specificity of flea parasites of mammals from the Andean Biogeographic Region.

Host specificity of fleas affects their biodiversity that plays a major role in determining the potential transmission routes by pathogens through vertebrate hosts, including humans. In the Biogeographic Andean region, numerous systematic and ecological studies have been conducted, revealing a high diversity of flea taxa of mammals and the presence of pathogenic organisms transmitted by fleas; however, the degree of preference with which each flea species associates with a mammal host remains poorly understood in this region. Herein, host specificity in mammal fleas from the Andean region was analysed. We employed the number of host species for each flea species and the index of host specificity STD *. Following the literature, 144 species and 13 subspecies of fleas (31 genera and 10 families) have been described in the Andean biogeographic region; 76 taxa are endemic to this region. To carry out the analyses of host specificity, we considered 1759 records of fleas collected from 124 species and 59 genera of wild and domestic mammals, mostly rodent species (85.9%). Our results indicate that typical Andean fleas are genus or family host specific (mostly STD * less than 3.0). More diverse mammal hosts are parasitized by more diverse flea genera and families and these hosts are phylogenetically related. Otherwise, these hosts are associated with different flea lineages, suggesting the interaction of ecological and evolutionary mechanisms (host-switching, ecological adaptations and co-evolutionary alternation). The fields of disease ecology and One Health are considering the host specificity of arthropod vectors as an important point to understand the mechanisms of emergence and re-emergence of diseases. Our results allow us to estimate the risk of diseases involving fleas in the Andean region.

The species composition of local flea assemblages at a small scale in two South American regions is predominantly driven by niche-based mechanisms.

We applied a step-down factor analysis (SDFA) and multi-site generalised dissimilarity modelling (MS-GDM) to local flea communities harboured by small mammals (i.e., collected at small sampling sites over a short time period) in two South American regions (Patagonia and the Northwestern Argentina) with the aim of understanding whether these communities were assembled via niche-based or dispersal-based processes. The SDFA allows us to determine whether clusters of flea assemblages across different types of climates, vegetation and soils can be distinguished (suggesting niche-based assembly). MS-GDM allows us to determine whether a substantial proportion of the variation in flea species turnover is explained by specific climate-associated, vegetation-associated and soil-associated variables (indicating niche-based assembly) or host turnover (indicating dispersal-based assembly). Mapping of assemblages on climate, vegetation and soil maps, according to their loadings on axis 1 or axis 2 of the SDFA, did not provide clear-cut results. Clusters of similar loadings could be recognized within some, but not other, climate, vegetation and soil types. However, MS-GDM demonstrated that the effect of environmental variables (especially air temperature) on flea compositional turnover was much stronger than that of host turnover, indicating the predominance of niche-based processes in local community assembly. A comparison of our results with those on the mechanisms that drive species assembly in regional communities allows us to conclude that local and regional communities result from the joint action of niche-based and dispersal-based processes, with the former more important at a smaller spatial scale and the latter at a larger spatial scale.

Effects of host factors on the dynamics of fleas (Siphonaptera) in Sigmodontinae rodents (Cricetidae) from El Espinal Ecoregion, Argentina.

We investigated the patterns of flea infestation in wild populations of eight Sigmodontinae rodent species: Akodon azarae, Calomys callidus, Calomys venustus, Holochilus chacarius, Necromys lasiurus, Oligoryzomys flavescens, Oligoryzomys nigripes and Oxymycterus rufus. Rodents were captured in systematic trapping sessions carried out along 2 years at two localities from El Espinal Ecoregion, Argentina. Mean flea intensity, occurrence (presence/absence) of flea infestation, richness and diversity were compared for different ages, body condition, sex and rodent tribes (Akodontini, Oryzomyini and Phyllotini). A total of 376 fleas of the following species and subspecies were collected: Craneopsylla minerva wolffhuegeli, Polygenis (Neopolygenis) pradoi, Polygenis (Polygenis) axius axius, and Polygenis (Polygenis) byturus. The most important factor driving flea infestation was the rodent tribe, with Phyllotini showing the highest values of occurrence, abundance and species richness. Only C. m. wolffhuegeli was affected by the sex of the host. Age and body condition of the hosts did not affect flea infestation. Our results contribute to knowledge of the ecology of fleas on rodent hosts in El Espinal Ecoregion. The relevance of host taxonomy as driver of flea dynamics highlight the importance of considering host community structures at the time of studying the ecology of parasites.

New record of Alectopsylla unisetosa (Siphonaptera: Ischnopsyllidae) from Patagonia.

Alectopsylla unisetosa (Ischnopsyllidae) from Santa Cruz province represents the second report of the species after 45 years. This new distributional record extends this species distribution 1350 km further south than previously documented. Moreover, Alectopsylla unisetosa infesting Myotis chiloensis constitutes a new flea-host association. This finding provides new insights into the biogeography and host associations within the family Ischnopsyllidae.

Ectoparásitos de importancia sanitaria de la Argentina / Ectoparasites of sanitary importance in Argentina

Los ectoparásitos parasitan animales vertebrados, incluido el hombre pudiendo provocan problemas sanitarios a sus hospedadores como parásitos propiamente dichos, como hospedadores intermediarios y/o como vectores de diversos patógenos. Dado que para muchas de las enfermedades provocadas por dichos patógenos se desconoce su presencia y efecto en la población humana argentina, es fundamental el desarrollo de estrategias de control y prevención de las ectoparasitosis. Para esto es necesario el estudio integral de los ectoparásitos, con la correcta identificación taxonómica, el conocimiento de su distribución, y de la eco-epidemiología de las especies de importancia sanitaria, y la comprensión de los sistemas ectoparásito-hospedador-ambiente y hospedador-vector-patógeno. Dado que para Argentina este conocimiento es limitado y fragmentario, el objetivo de nuestra investigación es avanzar en el estudio de las especies de ectoparásitos de varias regiones del país, estudiando parásitos de roedores y animales domésticos de localidades de Buenos Aires, NOA y Patagonia, ampliando el conocimiento de aquellas de importancia sanitaria, analizando el rol en la transmisión de patógenos e identificando escenarios de riesgo. El análisis molecular determinó nuevas especies de ectoparásitos como posibles vectores de patógenos de los géneros Bartonella y Rickettsia. La confección de mapas de distribución potencial demuestra que la franja del país que abarca el norte y centro-este es la que presenta la mayor probabilidad de ocurrencia de especies de ectoparásito de importancia sanitaria. Estos resultados tienen relevancia para la salud pública ya que se amplían el conocimiento de especies de ectoparásitos de importancia sanitaria, reportándose nuevas especies de ectoparásitos como vectores de patógenos, y a partir de los modelos de distribución potencial, se sugieren regiones del país con mayor riesgo de ocurrencia de zoonosis en las que intervienen los ectoparásitos

Host range and geographical distribution of Ixodes sigelos (Acari: Ixodidae).

Larvae, nymphs and females of Ixodes sigelos Keirans, Clifford and Corwin (Ixodidae) were collected in 13 localities of the Patagonian region of Argentina parasitizing eight species of sigmodontine rodents. We report for the first time adults of I. sigelos for Argentina. Besides, we extend the southern limit of its geographical distribution, and six species of sigmodontines are added as new host species of I. sigelos (Phyllotis xanthopygus, Euneomys chinchilloides, Calomys musculinus, Reithrodon auritus, Loxodontomys micropus and Eligmodontia morgani). The presence of larvae, nymphs and females on sigmodontines, as well as more than 50% of the individuals engorged, indicate that I. sigelos can develop the complete parasitic phase of its life cycle on these small mammals. The geographical distribution of I. sigelos is restricted to the biogeographical Andean Region in Argentina and Chile.