Functional redundancy of Amazonian dung beetles confers community‐level resistance to primary forest disturbance

Morphometric changes on dung beetle Dichotomius problematicus (Coleoptera: Scarabaeidae: Scarabaeinae) related to conversion of forest into grassland: A case of study in the Ecuadorian Amazonia

The conversion of forest into grassland can induce differentiation in the functional morphology of resilient species. To assess this effect, we have chosen a dung beetle Dichotomius problematicus, as a model species. We established 20 sampling points distributed along a transect for a forest and grassland located in the Podocarpus National Park in Ecuador. Four pit-fall traps were baited with pig feces per sample point and were left open for 48 h. We sexed and measured 13 morphological traits of 269 individuals. Nonmetric multidimensional scaling was carried out to evaluate the influence of habitat and sexual dimorphism on the traits. We applied a principal component analysis to evaluate the morphological features that best explain the differences between land use and sexual dimorphism. We used generalized linear models to evaluate the explanatory variables: habitat and sexual dimorphism with respect to morphological traits. Five traits contributed over 70% body thickness, Pronotum width, Pronotum length, Head width and Elytra length, following the results of a principal component analysis. Both habitat and sex influence traits. In the forest, the individuals are larger than grassland likely due to available resources, but in grassland, the structures in charge of the burial process head, protibia are larger, displaying a strong pronotum and possible a greater reproductive capacity given by spherecity. These patterns of changes in the size of beetles and their structures could reflect the conservation state of an ecosystem.

Disappearance of an ecosystem engineer, the white-lipped peccary (Tayassu pecari), leads to density compensation and ecological release

Given the rate of biodiversity loss, there is an urgent need to understand community-level responses to extirpation events, with two prevailing hypotheses. On one hand, the loss of an apex predator leads to an increase in primary prey species, triggering a trophic cascade of other changes within the community, while density compensation and ecological release can occur because of reduced competition for resources and absence of direct aggression. White-lipped peccary (Tayassu pecari—WLP), a species that typically co-occurs with collared peccary (Pecari tajacu), undergo major population crashes—often taking 20 to 30-years for populations to recover. Using a temporally replicated camera trapping dataset, in both a pre- and post- WLP crash, we explore how WLP disappearance alters the structure of a Neotropical vertebrate community with findings indicative of density compensation. White-lipped peccary were the most frequently detected terrestrial mammal in the 2006–2007 pre-population crash period but were undetected during the 2019 post-crash survey. Panthera onca (jaguar) camera trap encounter rates declined by 63% following the WLP crash, while collared peccary, puma (Puma concolor), red-brocket deer (Mazama americana) and short-eared dog (Atelocynus microtis) all displayed greater encounter rates (490%, 150%, 280%, and 500% respectively), and increased in rank-abundance. Absence of WLP was correlated with ecological release changes in habitat-use for six species, with the greatest increase in use in the preferred floodplain habitat of the WLP. Surprisingly, community-weighted mean trait distributions (body size, feeding guild and nocturnality) did not change, suggesting functional redundancy in diverse tropical mammal assemblages.