Habitat simplification affects functional group structure along with taxonomic and phylogenetic diversity of temperate-zone ant assemblages over a ten-year period

Biodiversity is declining at various scales due to habitat simplification. Nevertheless, there is scarce information on how the biotic and abiotic changes linked to simplification affect several diversity dimensions, such as taxonomic, functional, and phylogenetic diversities. This study investigated whether transforming natural oak forests into induced grasslands affected species diversity, functional group structure, and phylogenetic diversity of ant assemblages inhabiting a temperate forest in central Mexico. We placed over 1,000 pitfall traps in five sampling events covering a ten-year period. We used Hill numbers to evaluate species diversity differences between vegetation types and patterns over time. Ant species were classified into stress-related functional groups, which were analyzed for their association with vegetation types and changes to their proportional abundance over time. We calculated the standardized effect size of the mean nearest taxon distance to quantify the evolutionary history and test for non-random patterns within vegetation types and sampling years. Species richness did not differ between vegetation types, yet grasslands showed greater diversity for the q=1 and q=2 orders. Besides, we found three ant species as bioindicators for each vegetation. Regarding functional structure, cold climate specialists were associated with oak forests. In contrast, generalist species were predominant in induced grasslands. Higher phylogenetic diversity with an overdispersed structure was associated with oak forest, whereas lower phylogenetic diversity and a clustered pattern were found in induced grassland. These results indicate that habitat simplification may not affect the number of ant species but rather increases their relative abundance and reorganizes the functional and phylogenetic structure in the ecosystem, particularly shift towards the dominance of evolutionary close-related species and broad-stress tolerant groups. These results highlight the importance of integrating further dimensions of diversity to properly evaluate the reassembly dynamics after habitat simplification and understand the mechanisms driving this biodiversity loss.