Augusto Cesar de Aquino Ribas

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.

Abundância de Stomoxys calcitrans (Diptera: Muscidae) em diferentes subprodutos canavieiros

Increasing abundance of Stomoxyscalcitrans has been observed in organic byproducts resulting from sugar cane alcohol production. This study aimed to evaluate the abundance of S. calcitrans in such byproducts. From January to December 2011, the abundance of S. calcitrans was monitored in four byproducts: sugar cane bagasse, mulch, filter cake (FC) and mulch plus vinasse (MV), in a sugar cane mill located at the municipality of Angelica, state of Mato Grosso do Sul, Brazil. Monthly, 20 emergence traps were placed in each substrate, remaining active for the following four weeks. A total of 4,049 specimens of S. calcitrans was caught during the whole period, representing 9.22% of total amount of collected flies. The four byproducts studied showed significant differences regarding the abundance of S. calcitrans, being higher in FC (67.20%) and MV (29.19%). Abundance peaks were observed in June (PV) and October (PV and TF). The highest productivity of S. calcitrans was observed in TF (55.8 flies/mII) and PV (24.2 flies/mII) and the average monthly production of S. calcitrans at the mill was estimated at 37,000 and 24 million, respectively. The high capacity of S. calcitrans breeding in sugar cane byproducts explains the recent population explosions of this species reported in cattle ranches around sugarcane mills.

The composition of spider assemblages varies along reproductive and architectural gradients in the shrub Byrsonima intermedia (Malpighiaceae)

Abstract The presence of buds, flowers, and fruits increases structural complexity in plants, but can also attract potential prey for predators, thus determining faunistic composition. To understand how a spider assemblage living in the shrub Byrsonima intermedia (Malpighiaceae) varies with habitat structure in terms of reproductive elements and height of plant, we collected spider specimens and measured bud, flower, fruit, and leaf masses of 44 plants, as well as their height. Spider family composition was found to depend on habitat structure, following a pattern of family turnover occurring along gradients of reproductive plant elements and height, regardless of plant biomass. Theridiidae occurred in samples with the major proportions of buds and flowers, while Oxyopidae occurred only in samples with major proportions of fruits. Multiple linear regression revealed the strong relation between the composition in reproductive plant elements and the composition in families of spiders and a relation between shrub height and spider family composition. These results help us to understand the temporal dynamics between structural complexity of vegetation and spider assemblages, because during plant phenology the proportions of reproductive elements are also varying.

Floral traits as potential indicators of pollination vs. theft

Floral visitation does not necessarily mean pollination, as several animals utilize floral resources without transferring pollen. Since pollinators and thieves can affect the reproduction, morphology and diversification of flowering plants, we here investigated if attributes of flowers and flowering of plant species collected in the central Brazilian vereda would predict the pollination (pollen seeking) or theft (pollen/nectar theft) during the visits. It was hypothesized that non specialized flowers would have a higher incidence of thievery, where as specialization, for example, the presence of large and medium flowers with long corolla, making it difficult to access nectar, would lead to increased pollination. As a result, four attributes were mainly associated with illegitimate visits, and in order of importance, they are size (small), quantity of flowers per plant (large), flowering time (< 10 months) and floral type (inconspicuous). The richest and most abundant visitor groups, including bees, flies and wasps, acted mainly as potential pollinators, while cockroaches, butterflies, beetles, ants and hemipterans acted as thieves. However, further studies are required to confirm that this pattern is repeated in other larger and more diverse communities, thus confirming the possible preference for floral thieves.