Disturbance differentially affects alpha and beta diversity of ants in tallgrass prairies

Diversity response of necrophagous dipteran communities and their functional groups to an anthropization gradient

The anthropization process exerts a profound effect on ecosystems, causing alterations in biodiversity, habitat structure, and species composition, ultimately disrupting the delicate balance of natural environments. The aim of the present study was to explore the ecological dynamics of necrophagous Sarcophagidae and Calliphoridae flies along an anthropization gradient. This research investigated alpha and beta diversity patterns to unravel the impact of human-induced environmental changes on these insect communities and also assesses the dynamics of functional groups in relation to their impact on medical and forensic fields. Five distinct habitats, ranging from urban to forested areas, were surveyed in two Departments in the Province of Chaco, Argentina. Necrophagous flies were collected using van Someren-Rydon canopy traps across three seasons. Two main functional groups were analyzed: oviparous flies (Calliphoridae) and larviparous flies (Sarcophagidae). Results indicated a significant negative correlation between Sarcophagidae species richness and anthropization, whereas Calliphoridae showed increased abundance in highly anthropized sites. The combined assemblage of Calliphoridae+Sarcophagidae exhibited significant relationships across all community parameters evaluated. Beta diversity analysis revealed turnover as the main process shaping dipteran communities along the anthropization gradient, with spatial species replacement dominating. This underscores the importance of interspecific spatial segregation in dipteran community composition. In conclusion, this study enhances our understanding of the ecological adaptations of necrophagous dipterans to anthropogenic disturbances. The observed shifts in diversity and abundance have implications for forensic investigations and public health, emphasizing the need for nuanced monitoring and conservation strategies. This research contributes valuable insights into the intricate ecological interactions of these insect communities within changing ecosystems.

Urban tropical forest islets as hotspots of ants in general and invasive ants in particular

Urbanization is a crucial driver of environmental and biodiversity change. It is suggested that urbanization favours generalist and invasive species and might harm specialists of natural and semi-natural habitats. In this study, we examined how an urbanization gradient and environmental gradients in the habitat area, habitat diversity, elevation, and proportion of built-up area influenced the abundance and richness of ants within tropical forest islet habitat in south India. We used abundance (proportional trap incidence) of overall ants, native ants, invasive ants, and Anoplolepis gracilipes—a globally notorious invasive ant of possible south Asian origin—and rarefied richness as the response variables. We found that native ant abundance was greater and A. gracilipes abundance was lesser in less-urbanized landscape compared to moderately-urbanized and highly-urbanized landscape. The richness of ants and abundance of overall and invasive ants were unaffected by the urbanization. We also found that none of the measured environmental gradients but habitat diversity influenced abundance of overall ants, native ants, overall invasive ants, and richness of ants; however, A. gracilipes abundance was negatively correlated with habitat diversity. Ant species composition of less-urbanized landscape was distinct from that of higher urbanization levels. The richness and abundance of native ants and abundance of non-A. gracilipes invasive ants decreased with the abundance of A. gracilipes. Because the forest islets of all three urbanization levels supported similar richness of native ants, the urbanization seems not to have an adverse effect for the native ants of native forest islets. The increasing population of A. gracilipes in urban green islets, however, is a concern. Future studies might investigate its effect on other invertebrates of epigeal and soil strata.

Gamma diversity and under-sampling together generate patterns in beta-diversity

Beta diversity represents how species in the regional pool segregate among local communities and hence forms a link between local and regional species diversities. Therefore, the magnitude of beta diversity and its variation across geographic gradients can provide insights into mechanisms of community assembly. Along with limits on local or regional level diversities, effects of local abundance that lead to under-sampling of the regional species pool are important determinants of estimated beta diversity. We explore the effects of regional species pools, abundance distributions, and local abundance to show that patterns in beta diversity as well as the mean of species abundance distribution have distinct outcomes, depending on limits on species pools and under-sampling. We highlight the effect of under-sampling in some established relationships between gamma diversity and beta diversity using graphical methods. We then use empirical data on ant communities across an elevational gradient in the Eastern Himalayas to demonstrate a shift from effect of reduction in species pool to under-sampling at mid-elevations. Our results show that multiple processes with contrasting effects simultaneously affect patterns in beta diversity across geographic gradients.

Site and species contribution to β-diversity in terrestrial mammal communities: Evidence from multiple Neotropical forest sites

In a scenario where escalating human activities lead to several environmental changes and, consequently, affect mammal abundance and distribution, β-diversity may increase due to differences among sites. Using the ecological uniqueness approach, we analyzed β-diversity patterns of ground-dwelling mammal communities recorded through comprehensive camera trap monitoring within eight tropical forests protected areas in Mesoamerica and South America under variable landscape contexts. We aimed to investigate whether the contribution of single sites (LCBD) and single species (SCBD) to overall β-diversity could be explained by community metrics and environmental variables, and by species metrics and biological traits, respectively. Total β-diversity was also partitioned into species replacement and richness difference. We related LCBD to species richness, total relative abundance, functional indices, and environmental variables (tree basal area, protected area size, NDVI, and precipitation seasonality), and SCBD to species naïve occupancy, relative abundance, and morphoecological traits via beta regression. Our findings showed that LCBD was primarily explained by variation in species richness, rather than relative abundance and functional metrics. Protected area size and tree basal area were also important in explaining variation in LCBD. SCBD was strongly related to naïve occupancy and relative abundance, but not to biological traits, such as body mass, trophic energy level, activity cycle, and taxonomic category. Local β-diversity was a result of species replacements and to a lesser extent differences in species richness. Our approach was useful in examining and comparing the ecological uniqueness among different sites, revealing the regional scale current status of mammal diversity. High LCBD values comprised sites embedded within smaller habitat extents, hosting lower tree basal areas, and harboring low species richness. SCBD showed that relatively ubiquitous species that occur at variable abundances across sites contributed most to β-diversity.

An insight into the quality of sacred groves – an island habitat – using leaf-litter ants as an indicator in a context of urbanization

Sacred groves (SGs) of India are islets of forests providing ecosystem and spiritual services to man. Studies suggest that SGs are deteriorating on their quality due to urbanization, invasive species, land-use change, and religious modernization. We explored diversity, community, and abundance of overall and different functional groups of litter ants, including Anoplolepis gracilipes – an invasive ant – on paired SG-neighbouring home garden (HG) sites in rural and urban landscape to (a) assess the quality of SGs and (b) examine whether the variation in ant community of the two habitats was predicted by urbanization and abundance of A. gracilipes. We considered species and local contribution to β-diversity to identify species and sites crucial for conservation of sites. Abundance and richness of overall ants, proportional trap incidence of species, and abundance of A. gracilipes were similar on SG and HG, but species diversity and abundance of certain ant functional groups were higher on SG. Ant community of SG was different from HG, but was not affected by urbanization. A. gracilipes and rural SGs contributed the most to β diversity. A. gracilipes gave little pressure on native ant community. The study concludes that SGs, despite invaded by A. gracilipes, have potential for conserving biodiversity.

Ants of the Palouse Prairie: diversity and species composition in an endangered grassland

Grasslands are globally imperilled ecosystems due to widespread conversion to agriculture and there is a concerted effort to catalogue arthropod diversity in grasslands to guide conservation decisions. The Palouse Prairie is one such endangered grassland; a mid-elevation habitat found in Washington and Idaho, United States. Ants (Formicidae) are useful indicators of biodiversity and historical ecological disturbance, but there has been no structured sampling of ants in the Palouse Prairie. To fill this gap, we employed a rapid inventory sampling approach using pitfall traps to capture peak ant activity in five habitat fragments. We complemented our survey with a systemic review of field studies for the ant species found in Palouse Prairie. Our field inventory yielded 17 ant species across 10 genera and our models estimate the total ant species pool to be 27. The highest ant diversity was found in an actively-managed ecological trust in Latah County, Idaho, suggesting that restoration efforts may increase biodiversity. We also report two rarely-collected ants in the Pacific Northwest and a microgyne that may represent an undescribed species related to Brachymyrmexdepilis. Our score-counting review revealed that grassland ants in Palouse Prairie have rarely been studied previously and that more ant surveys in temperate grasslands have lagged behind sampling efforts of other global biomes.

Grassland harvesting alters ant community trophic structure: An isotopic study in tallgrass prairies

Disturbances have long been recognized as important forces for structuring natural communities but their effects on trophic structure are not well understood, particularly in terrestrial systems. This is in part because quantifying trophic linkages is a challenge, especially for small organisms with cryptic feeding behaviors such as insects, and often relies on conducting labor-intensive feeding trials or extensive observations in the field. In this study, we used stable isotopes of carbon and nitrogen to examine how disturbance (annual biomass harvesting) in tallgrass prairies affected the trophic position, trophic range, and niche space of ants, a widespread grassland consumer. We hypothesized that biomass harvest would remove important food and nesting resources of insects thus affecting ant feeding relationships and trophic structure. We found shifts in the feeding relationships inferred by isotopic signatures with harvest. In particular, these shifts suggest that ants within harvest sites utilized resources at lower trophic levels (possibly plant-based resources or herbivores), expanded trophic breadth, and occupied different niche spaces. Shifts in resource use following harvest could be due to harvest-mediated changes in both the plant and arthropod communities that might affect the strength of competition or alter plant nitrogen availability. Because shifts in resource use alter the flow of nutrients across the food web, disturbance effects on ants could have ecosystem-level consequences through nutrient cycling.