Evaluation of the fundamental niche under controlled conditions can provide relevant information about physiological, evolutionary, and ecological aspects of an organism, without the influence of external factors. We investigated how allometric, phylogenetic, and adaptive components contribute to arboreal walking performance by 7 sigmodontine rodents of the Brazilian savanna (Cerrado). We captured the rodents in the field and evaluated their performances by measuring stride length, stride frequency, and velocity on 5 horizontal supports: flat board and cylindrical plastic tubes with diameters of 5.0, 3.5, 2.5, and 2.0cm. Arboreal rodents exhibited higher velocities than terrestrial species by increasing stride frequency and decreasing stride length on supports with smaller diameters. However, terrestrial species decreased both stride frequency and stride length or tended to maintain stride length and vary stride frequency. Our results reveal a strong association between realized arboreal walking performances (as inferred by proportion of arboreal captures) and stride length and frequency. However, performance metrics were weakly related to body mass and exhibited no phylogenetic effects. Our results are consistent with the hypothesis that dynamically stable arboreal walking is facilitated by increased velocity. Arboreal walking performance is likely related to ecological factors rather than phylogenetic constraints. A avaliação do nicho fundamental por meio de condições controladas pode fornecer informações relevantes sobre aspectos fisiológicos, evolutivos e ecológicos de diferentes organismos, excluindo a influência de fatores externos. Considerando tal abordagem, nós investigamos como componentes alométricos, filogenéticos e adaptativos podem contribuir para a habilidade de locomoção arborícola em sete espécies de roedores sigmodontíneos do Cerrado. Os roedores foram capturados no campo e tiveram suas performances avaliadas por meio de medidas de tamanho de passos, frequência de passos e velocidade em cinco suportes horizontais distintos: tábua, e tubos cilíndricos de plástico com diâmetros de 5,0, 3,5, 2,5 e 2,0cm. Nossos resultados revelaram que roedores arborícolas apresentaram maiores velocidades em comparação com roedores mais terrestres. Adicionalmente, as espécies arborícolas mantiveram ou aumentaram a velocidade em suportes com menores diâmetros, enquanto que os roedores terrestres tenderam a reduzir a velocidade. Para as espécies arborícolas, tais velocidades foram obtidas por meio do aumento da frequência de passos e diminuição do tamanho dos passos. Entretanto, espécies primariamente terrestres diminuíram tanto a frequência quanto o tamanho dos passos, ou tenderam a manter a o tamanho de passos e variar a frequência de passos. Nossos resultados revelaram uma forte associação entre capturas acima do solo e o tamanho e frequência de passos. Contudo, tais aspectos da habilidade de locomoção tiveram fraca relação com a massa corporal e não tiveram relação com a filogenia das espécies analisadas. Nossos resultados corroboram a hipótese de que roedores necessitam aumentar velocidade como forma de manter a locomoção arborícola dinamicamente estável. Entretanto, a habilidade de locomoção é provavelmente mais relacionada com fatores ecológicos do que com restrições filogenéticas.

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To date, there have been no studies that have evaluated small mammal utilization of the understory of forests. In this study, we described the use of vertical strata by small mammals in patches of unflooded forests, known as “cordilheiras”, in the Nhecolândia sub-region of the Pantanal, Brazil. We collected all species using the ground and understory, including the terrestrial didelphid Monodelphis domestica. We suppose that local habitat features (e.g., Acuri palms), rather than intrinsic species characteristics, may be more conducive to the use of understory vegetation by small mammals in the Nhecolândia region.

South American opossums (Didelphis spp.) are definitive hosts of Sarcocystis neurona, Sarcocystis speeri, Sarcocystis lindsayi and Sarcocystis falcatula. In Brazil, diverse studies have demonstrated a high frequency of Sarcocystis falcatula-like in sporocysts derived from opossums, and high genetic diversity has been observed in surface antigen-encoding genes (SAGs). In this study, genetic diversity of Sarcocystis spp. derived from Didelphis albiventris and Didelphis aurita from the cities of Campo Grande and São Paulo, was accessed by sequencing SAG2, SAG3, SAG4, the first internal transcribed spacer (ITS-1) and cytochrome c oxidase subunit I (cox1). Molecular identification was performed for 16 DNA samples obtained from sporocyst or culture-derived merozoites. The ITS-1, cox1, and SAG3 fragments were cloned, whereas SAG2 and SAG4 were sequenced directly from PCR products. Four alleles variants were found for SAG2, 13 for SAG3 and seven for SAG4, from which four, 13 and four, respectively, were novel. Twenty-seven allele variants were found for ITS-1, all phylogenetically related to S. falcatula-like previously described in Brazil. Sarcocystis sp. phylogenetically related to Sarcocystis rileyi was evidenced by cox1 in three opossums. Further studies are needed to clarify the role of Didelphis spp. as definitive hosts of Sarcocystis spp. other than that previous described.