The effect of local environmental variables in the helminth parasite communities of the pointedbelly frog Leptodactylus podicipinus from ponds in the Pantanal Wetlands

Understanding the patterns of species distribution and abundance has been at the core of ecology. In general, these patterns are determined by species dispersion as well as by abiotic and biotic environmental conditions. Similarly, host–parasite relations and the structure of parasite assemblages are also shaped by environmental conditions and landscape composition. Herein, we assessed the influence of environmental variables and parasite species dispersion on the structure of helminth parasites communities in the frog Leptodactylus podicipinus. We sampled 10 ponds and recorded area, depth, altitude, pH, dissolved oxygen, salinity, temperature, and extent of soil, water, and vegetation cover as well as the distances between the ponds. We collected 121 frogs and found 9 helminth taxa; 2 of them were core species (prevalence higher than 50%), which contributed to the relatively high similarity observed among the ponds. Most of the helminths showed some variation in the frequencies of occurrence among communities from different ponds. The change in species composition among ponds was explained by the environmental variables but not by the distance between the ponds. Moreover, the results indicated that local processes (variation in environmental conditions) were more important than the regional processes (species distribution) in determining the structure of parasite communities. The variation in helminth communities among ponds in response to moderate differences in pond environmental characteristics points to the potential of helminth species as indicators of environmental conditions

How many parasites species a frog might have? determinants of parasite diversity in South American anurans

There is an increasing interest in unveiling the dynamics of parasite infection. Understanding the interaction patterns, and determinants of host-parasite association contributes to filling knowledge gaps in both community and disease ecology. Despite being targeted as a relevant group for conservation efforts, determinants of the association of amphibians and their parasites in broad scales are poorly understood. Here we describe parasite biodiversity in South American amphibians, testing the influence of host body size and geographic range in helminth parasites species richness (PSR). We also test whether parasite diversity is related to hosts' phylogenetic diversity. Results showed that nematodes are the most common anuran parasites. Host-parasite network has a nested pattern, with specialist helminth taxa generally associated with hosts that harbour the richest parasite faunas. Host size is positively correlated with helminth fauna richness, but we found no support for the association of host geographic range and PSR. These results remained consistent after correcting for uneven study effort and hosts' phylogenic correlation. However, we found no association between host and parasite diversity, indicating that more diversified anuran clades not necessarily support higher parasite diversity. Overall, considering both the structure and the determinants of PRS in anurans, we conclude that specialist parasites are more likely to be associated with large anurans, which are the ones harbouring higher PSR, and that the lack of association of PSR with hosts' clade diversification suggests it is strongly influenced by ecological and contemporary constrains

Estimates of helminth species richness to South American anurans of different body sizes.

<p>Estimates of helminth species richness to South American anurans of different body sizes.</p

Estimates of helminth parasite species richness (PRS) to South American anurans of different body sizes in response to the number of studies (study effort).

<p>Each circle represents an anuran species, the size of each circle shows the real study effort, dashed lines show the estimated PRS in response to different study effort.</p

Barplot of helminth parasite species reported to different anuran families.

<p>White bars show the number of anuran species surveyed, color bars show the amount (log transformed) of helminth parasites reported for each host family.</p

Frequency of the number of studies, body size and geographic range tested as predictors of helminth parasite species richness in South American Anurans.

<p>Frequency of the number of studies, body size and geographic range tested as predictors of helminth parasite species richness in South American Anurans.</p

Interacting network of South American anuran species and helminth families.

<p>Anuran phylogeny is adapted from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0140577#pone.0140577.ref023" target="_blank">23</a>].</p

Results from the nls model for the relationship between study effort, host size and geographic range and parasite species richness in anurans from South America.

<p>Results from the nls model for the relationship between study effort, host size and geographic range and parasite species richness in anurans from South America.</p

Results from the phylogenetic generalized least squares (PGLS) for the relationship between study effort, host size, geographic range and parasite species richness in anurans from South America.

<p>¹AIC = 667.9203, BIC = 678.3007, logLik = -329.9601.</p><p>Model fit parameters are described in the footnote<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0140577#t001fn001" target="_blank">¹</a>.</p