Local randomness, vegetation type and dispersal drive bird and mammal's diversity in a tropical South American region

Abstract

Abstract. How dispersal, environmental filters, and local extinctions affect species diversity depends on the species requirements for habitat, dispersal limitations, and abundance. Few studies have been able to properly separate these processes and to show how they affect the beta diversity patterns for multiple organisms. We investigated how the composition of birds and mammals changed along geographical and environmental gradients in an environmentally complex South American region. Using mantel tests and a null model approach we disentangled the effects of dispersal, environment, and stochastic processes in the species beta diversities. The similarity on species composition was negatively associated with the geographical distance separating areas for both groups. The changes in bird species composition likely resulted from their dispersal limitation over large geographical regions. In contrast, the composition of mammals in a given area was a partially random subset of the regional species pool, to some extent, filtered by the vegetation. Small communities tended to have more variable species composition, whereas dispersal limited birds showed a stronger distance-decay pattern. Neither local randomness nor dispersal limitation prevented species from being filtered by the environment. Other groups are likely to show similar patterns depending on their dispersal abilities, environmental requirements and community size.

Environment and space as drivers of variation in skull shape in two widely distributed South-American Tayassuidae,Pecari tajacuandTayassu pecari(Mammalia: Cetartiodactyla)

“…However, the skull changes might also reflect phenotypic plasticity, since we detected a stronger impact of the environment on the more plastic species, P. tajacu . A wide range of moisture conditions experienced by P. tajacu inside and outside forests (Fragoso, ; Keuroghlian & Eaton, ), in the present and probably in the past, makes it more susceptible to changes in skull shape due to environmental variation, even in the existence of other spatially structured processes (Cáceres et al ., ). Conversely, the seasonal affinities of T. pecari for humid and more stable environments (Fragoso, ; Keuroghlian & Eaton, ) might not have been strong enough to affect skull shape to the same extent as in P. tajacu .…”

“…(). Furthermore, the effects of geographical space on peccaries are expected to be mainly observed in interaction with the environment since environmental variables tend to be naturally spatially structured (Cáceres et al ., ). Nevertheless, if other spatially structured processes are also determinants of skull shape variation in mammals (e.g.…”

The prevalence of temperature and dispersal limitation as drivers of diversity in Neotropical small mammals

“…The natural distribution of a species in a region is determined by its dispersal limitation and its adaptation to environmental conditions (Qian 2008; Cáceres et al . 2014). The distribution ranges of dispersal limited taxa show strong associations to geographical barriers (like mountain chains, large rivers or dry areas), whereas taxa with specific habitat requirements show strong associations with environmental gradients (Gilbert & Lechowicz 2004; Steinitz et al .…”

Vegetated highway medians as foraging habitat for small mammals

“…Given that access to the wildlife passage (and therefore the vegetated median that bisected the wildlife passage) is a function of wildlife passage openness in this area, species groups would not have had equal accessibility to the vegetated medians at each wildlife passage (Martinig and Bélanger‐Smith ). Likewise, if older wildlife passages with wider vegetated medians were more likely to experience regrowth, these vegetated medians may then support a diversity of foraging opportunities (Davis , Litteral and Wu , Cáceres et al , Crouzeilles et al ). Another possibility is that wider vegetated medians within the highway corridor may better buffer against disturbances.…”