Relación de los pequeños mamíferos terrestres (Rodentia y Didelphimorphia) con la estructura de la vegetación en el Bosque Atlántico Interior – un análisis multivariado

Abstract

The ecological importance of small mammals includes their role as dispersers of seeds, spores and propagules of plants, fungi and lichens, decomposers of organic matter and controllers of invertebrates as well as prey of a great number of vertebrates. The objective of this research was to determine the relationship between non-volant small mammals (Rodentia and Didelphimorphia) to vegetation structure and the extent of degradation of the forest in an area near the western boundary of the Upper Parana Atlantic Forest, and to evaluate seasonal and interannual variation in species’ abundances. The study was conducted in the Mbaracayú Forest Natural Reserve, Paraguay. Mark-capture methodology was employed in three sites with different degrees of degradation, in two seasons of the year (dry and rainy), in 2015 and 2016. A multivariate analysis was performed with ANOVA and MANOVA, evaluating degree of habitat disturbance and annual and seasonal variation as independent variables and species abundances as dependent variables. Sixteen small-mammal species were recorded, with 1,161 captures of 598 individuals and 563 recaptures throughout the sampling. Twelve species were of the Order Rodentia (all of the family Cricetidae, subfamily Sigmodontinae), and four of the Order Didelphimorphia (family Didelphidae). Variables that were significant for the most abundant species (Akodon montensis) were interannual variation and habitat degradation. The most common didelphid species in the study was Gracilinanus agilis, which appears well-adapted to different degrees of habitat degradation, given its occurrence in all sites. Plant communities, including their composition and degree of habitat disturbance, are important for small-mammal communities which are interacting in the different habitats of the forest. In this study we observed that Akodon montensis was most abundant in the habitat of moderate disturbance in the dry season (June). This habitat was characterized by large trees with grasses predominant in the understory. Hylaeamys megacephalus was most abundant in the dry season (June) and less so in the rainy season (November). Oligoryzomys nigripes is a habitat generalist and is less specialized in food preference. Abundance of the didelphid species Gracilinanus agilis was quite variable among sampling periods, but the species was present in all three levels of habitat degradation. The various species (especially the most abundant) exhibited different responses to habitat degradation and to interannual and seasonal variations.