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.