Differential response of fire on the community dynamics of five insect taxa in a tropical mountaintop forest archipelago.

The Earth's most diverse group of organisms is facing an imminent crisis, as recent investigations suggest a remarkable decline in insect diversity. Within this context, altimontane forest islands might emerge as important refuges holding an invaluable diversity of species that would be doomed to disappear. Here, we aimed to examine the impact of fire on the temporal variation of ant, bee, butterfly, dung beetle, and wasp communities in natural and highly threatened altimontane forest islands. We predicted that fire incidence would increase the natural variation in the structure of these insects' communities over time. Furthermore, we predicted that each taxon would respond accordingly to their ability to move between forest islands (i.e., vagility). We sampled these five bioindicator taxa in the rainy seasons of 2014, 2015, 2018, and 2020 within 14 forest islands in southeast Brazil. We assessed the incidence (presence/absence) of fire occurrence on each forest island toward the end of the dry season in each sampling year. We found an influence of fire incidence on the species composition changes over time (temporal ß-diversity) in the less vagile insect groups: ants, and dung beetles. Nevertheless, we found no influence of fire incidence on shifts in species composition of highly vagile insects: bees, butterflies, and wasps. Importantly, species turnover was the primary component of temporal ß-diversity driving the interannual variation of all insect taxa examined in this study. Our results highlight the distinct responses of more-or-less vagile insect groups to fire in forested ecosystems and shed light on the drivers of vulnerability and resilience of these groups to this critical anthropogenic pressure. By understanding and elucidating the intricate responses of distinct insect communities to global stressors, we can strengthen our capacity to predict future trends in biodiversity decline and provide valuable insights for conservation efforts and environmental management strategies.

Compositional changes in bee and wasp communities along Neotropical mountain altitudinal gradient.

Climate conditions tend to differ along an altitudinal gradient, resulting in some species groups' patterns of lower species richness with increasing altitude. While this pattern is well understood for tropical mountains, studies investigating possible determinants of variation in beta-diversity at its different altitudes are scarce. We sampled bee and wasp communities (Hymenoptera: Aculeata) along an altitudinal gradient (1,000-2,000 m.a.s.l.) in a tropical mountainous region of Brazil. Trap nests and Moericke traps were established at six sampling points, with 200 m difference in altitude between each point. We obtained average climate data (1970-2000) from Worldclim v2 for altitudes at each sampling site. Nest traps captured 17 bee and wasp species from six families, and Moericke traps captured 124 morphospecies from 13 families. We found a negative correlation between altitude and species richness and abundance. Temperature, precipitation, water vapor pressure, and wind speed influenced species richness and abundance, and were correlated with altitude. ß-diversity was primarily determined by species turnover as opposed to nestedness, and Aculeate community similarity was higher for more similar altitudinal ranges. Moericke traps seem to be more efficient for altitudinal surveys compared to nest traps. We found high occurrence of singleton and doubleton species at all altitudes, highlighting the need for long-term studies to efficiently assess hymenopteran diversity in these environments.

Spatio-Temporal Distribution of Bark and Ambrosia Beetles in a Brazilian Tropical Dry Forest.

Bark and the ambrosia beetles dig into host plants and live most of their lives in concealed tunnels. We assessed beetle community dynamics in tropical dry forest sites in early, intermediate, and late successional stages, evaluating the influence of resource availability and seasonal variations in guild structure. We collected a total of 763 beetles from 23 species, including 14 bark beetle species, and 9 ambrosia beetle species. Local richness of bark and ambrosia beetles was estimated at 31 species. Bark and ambrosia composition was similar over the successional stages gradient, and beta diversity among sites was primarily determined by species turnover, mainly in the bark beetle community. Bark beetle richness and abundance were higher at intermediate stages; availability of wood was the main spatial mechanism. Climate factors were effectively non-seasonal. Ambrosia beetles were not influenced by successional stages, however the increase in wood resulted in increased abundance. We found higher richness at the end of the dry and wet seasons, and abundance increased with air moisture and decreased with higher temperatures and greater rainfall. In summary, bark beetle species accumulation was higher at sites with better wood production, while the needs of fungi (host and air moisture), resulted in a favorable conditions for species accumulation of ambrosia. The overall biological pattern among guilds differed from tropical rain forests, showing patterns similar to dry forest areas.

Dung Beetles along a Tropical Altitudinal Gradient: Environmental Filtering on Taxonomic and Functional Diversity.

Mountains provide an interesting context in which to study the many facets of biodiversity in response to macroclimate, since environmental conditions change rapidly due to elevation. Although the decrease in biodiversity with increasing elevation is generally accepted, our understanding of the variation of functional diversity along altitudinal gradients is still poorly known. The partitioning of diversity into spatial components can help to understand the processes that influence the distribution of species, and these studies are urgently needed in face of the increasing threats to mountain environments throughout the world. We describe the distribution of dung beetle diversity along an altitudinal gradient on a tropical mountain in southeastern Brazil, including the spatial partitioning of taxonomic and functional diversities. The altitudinal gradient ranged from 800 up to 1400 m a.s.l. and we collected dung beetles at every 100 m of altitude. We used the Rao Index to calculate γ, α and ß diversity for taxonomic and functional diversity of dung beetles. Climatic, soil and vegetation variables were used to explain variation in community attributes along the altitudinal gradient. Dung beetle richness declined with altitude and was related to climatic and vegetation variables, but functional diversity did not follow the same pattern. Over 50% of γ taxonomic diversity was caused by among altitudes diversity (ß), while almost 100% of functional diversity was due to the α component. Contrasting ß taxonomic with ß functional diversity, we suggest that there is ecological redundancy among communities and that the environment is filtering species in terms of the Grinnellian niche, rather than the Eltonian niche. ß taxonomic diversity is caused mainly by the turnover component, reinforcing the hypothesis of environmental filtering. Global warming may have strong effects on mountain communities due to upslope range shifts and extinctions, and these events will lead to an even larger than previously expected loss of diversity as dung beetles γ taxonomic diversity is caused mainly by the ß component.