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a b s t r a c tAlthough reproducing once in a lifetime (i.e. semelparity) is considered rare among vertebrates, it has evolved at least five times in two distantly related marsupial families; the Australian Dasyuridae and South American Didelphidae. The major aim of this research was to describe the population dynamics, reproductive strategy and associated life-history traits of the agile gracile mouse opossum, Gracilinanus agilis, in order to position the species along the fast-slow life-history continuum. Sampling was carried out through mark-recapture, from August 2010 to April 2013, in a Brazilian area of cerrado. Reproductive activity was seasonal and synchronized among females, and occurred from July to January/February. After mating, population size decreased due to male disappearance, which seems to be explained by postmating male die-off. Phylogenetic predisposition toward semelparity in Gracilinanus lineage and intense competition for females may contribute to male die-off, as indicated by several evidences such as malebiased sex ratio, signs of aggression in reproductive males, and a pronounced gain in male body mass and size prior to mating. Although two litters were produced, most females disappeared after weaning their young, indicating post-reproductive senescence and resulting in discrete, non-overlapping generations, characterizing semelparity in this population of G. agilis.

Space use patterns of a population are a result of the set of movements of its individuals, which are directly influenced by their attributes and environmental conditions. Understanding space use patterns and its determinants may give us insights about a species’ ecology, social and mating systems. Although echimyid rodents display a variety of mating and social systems, movements of burrowing species are poorly studied due to their cryptic habits. Hence, in this study, we evaluated the effects of body mass, sex, and palm fruit availability on space use patterns of the burrowing echimyid Clyomys laticeps, by measuring their daily home range (DHR) and intensity of habitat use. In 9 months of study in a “cerrado campo sujo” site, we tracked 14 adults with the spool‐and‐line in a backpack method. Adult males had larger DHR size than females, probably as a response to greater body mass and reproductive behavior. Furthermore, adult females had greater intensity of habitat use, presenting site fidelity, which can be due to offspring care as a response to non‐seasonal reproduction observed in our study and/or due to nest site defense strategy to avoid energetic costs associated with burrow construction. Differently from expected, food availability (i.e., Allagoptera campestris palm fruits) had no influence on the space use patterns of C. laticeps. As in other herbivorous rodents, shifts in proportion of consumed food items according to their availability may explain the lack of this influence in our study. Our findings suggest that space use patterns of C. laticeps are mainly explained by behavioral and physiological differences between sexes, including body mass and reproductive strategies. Additionally, larger male movements and female site fidelity suggest a solitary behavior and a polygynous mating system, although further studies regarding spatial organization and genetic structure are necessary to support these suggestions.

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In this study we describe and illustrate a new species, Chrysso intervales n. sp., based on males and females collected in Parque Estadual Intervales, an area of Atlantic Forest in the State of São Paulo, Brazil. We present data on habitat selection, web architecture, thread adhesiveness, diet, and mortality due to fungi for both Chrysso intervales and the sympatric species, Helvibis longicauda. Both species build webs on vegetation close to river margins, but they were not found in forest sites away from these shaded and extremely humid corridors. The webs of both species are entirely composed of viscid silk lines, occupying the space between two or more large leaves. The construction of this web type by Helvibis and Chrysso, and the large amount of viscid droplets in their threads, indicate that the investment in adhesive components in theridiids may be dependent on the ambient conditions. We suggest that the costs of maintaining viscid silk lines in humid areas may be relatively low, explaining the habitat restriction observed in the species studied. By selecting humid habitats, however, these spiders are susceptible to attacks by fungi. The webs constructed by both species intercepted mostly Diptera, especially tipulids, but H. longicauda was also observed consuming a wide variety of prey types.

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