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.

Study site

The study was conducted in the temperate natural protected area of Flor del Bosque State Park (FBSP). The FBSP consists of 699.2 ha and is located in Puebla, Mexico (19°01'N, 98° 20'W, 2,225–2,400 m.a.s.l.). The climate is temperate-subhumid with an annual average temperature of 14 to 16 °C and average annual precipitation of 750 to 950 mm. The rainy season occurs during the summer, and the dry season from November to April. The soil type is mainly lithosol and cambisol (Costes-Quijano et al., 2006). Its vegetation is composed of oak forest (41.71% of the park's surface), secondarily induced grassland (16.25%), and abandoned eucalyptus plantations (1.52%); the remaining 40.52% of the surface consists of thorny scrub and urban areas (Costes Quijano et al., 2006).

Ant sampling

Ant sampling was conducted in FBSP at six sampling events during the dry and rainy seasons, covering ten years. The sampling years were 2007, 2009, 2015, 2016, and 2017 (Table 1). Oak forests and induced grasslands were included in each sampling event. Pitfall traps were placed in transects. S1 shows the coordinates of transects used in this study. The number of transects, pitfall traps, and distances between them varied depending on the year, but samplings generally kept the same basic characteristics (type of trap, vegetation type, season, Table 1). At each site, 10-20 pitfall traps were placed per transect (spaced 5-20 m apart). Pitfall traps remained in the ground for 48-96 h. In total, data was obtained from 1,080 pitfalls during the ten-year period. Ants collected from pitfall traps were stored in 70% ethanol and taken to the laboratory for identification. Ants were identified to the genus level using taxonomic keys. Specimens were sent to the following specialists for their identification: L. Quiroz, J. E. Valenzuela, G. R. Pérez-Toledo (Instituto de Ecología, A.C.), and W. Mackay (the University of Texas, Laboratory for Environmental Biology Centennial Museum). Ant specimens are kept in the UDLAP Formicidae and IEXA collections. The Secretaría de Medio Ambiente y Recursos Naturales (SEMARNAT) (Bureau of Environment and Natural Resources) approved the collection permit for this study SGPA/DGV/06901/15.

Costes-Quijano, R., Meza, A. R., Macías-Juárez, A., Berriel-Mastreta, C. A., Cortés-Atílano, B., Martínez-Romero, L. E., & Hernández-Bautista, R. (2006). Plan de manejo parque ecológico recreativo General Lázaro Cárdenas Flor del Bosque. Secretaría de Medio Ambiente y Recursos Naturales. Gobierno Del Estado de Puebla, Puebla.