Structuring factors of the ant communities in the Segura River Basin

Abstract

Structuring factors of the ant communities in the Segura River Basin The main objetives for this Thesis were: 1) Faunistic and zoogeographic study of the ants of the Segura River Basin. 2) To study the gradients of ant Taxonomic, Functional and Phylogenetic diversity and its relationships in the Segura River Basin. To identify the main environmental drivers of ant diversity patterns. 3) To determine how changes in soil surface and vegetation caused by reforestation in Sierra del Picarcho (Región de Murcia, Spain) affect the ant assemblage. To achieve this objetives, the present Thesis is composed of four chapters: 1) Zoogeography of the Ants (Hymenoptera: Formicidae) of the Segura River Basin. We present the first checklist of the ant species of the Segura River Basin based on a review of specific literature and biological material collected during the field work. Our findings recorded 110 species that belong to 30 genera of ants and twenty two of these species have been recorded for the first time in this area. We found species with different evolutionary and zoogeographic origins (two zoogeographical zones and 14 zoogeographical elements). The zoogeographical composition is dominated by the species of the Mediterranean zone (75.2%). The species from the mixed and deciduous forest zone (19.1%) show a preference for the high-mid altitudes, where the climate is cooler, and more humid. There are only six cosmopolitan species (5.71%). 2) Environmental filtering in a semiarid region underlies ant diversity gradients and phylogenetic structure. Ant communities of the Segura River Basin were studied at two spatial scales. There is a general environmental gradient, which is an important force structuring ant diversity, from the higher, colder, and wetter areas to the lower, hotter, and dryer areas. Precipitation seems to be the more important environmental factor controlling ant taxonomic diversity. We found an overdispersed phylogenetic structure in the higher areas and a phylogenetically clustered structure at low elevations areas. The relationships between the diversity indices and the environmental factors are more evident at the coarser spatial scale because, at the lower scale, species interactions (especially competition) have a major relevance as community drivers. 3) Effect of pine reforestation associated with soil disturbance on ant assemblages (Hymenoptera: Formicidae) in a semiarid steppe. Ants were sampled in area that had been reforested and adjacent grassland using pitfall traps. Soil surface and vegetation were characterized. The disturbance of the vegetation caused by reforestation resulted in a decrease in the cover of Stipa tenacissima and Cistaceae and an increase in the cover of pine. The mechanical preparation of the site also resulted in changes in the soil surface, with an increase in the cover of stones and rocks. Ant species richness and abundance were greater at the reforested site than in the grassland and more species showed a positive than a negative response to reforestation. The underlying causes of this pattern are associated with the increase in the cover of pine, which most probably provided additional food resources, and the greater cover of stones and rocks that provided more shelter for the ant assemblage. 4) A New Ant Species, Temnothorax ansei sp.n. (Hymenoptera: Formicidae) from the Arid Environments of South-eastern Spain. We describe here a new ant species in the genus Temnothorax, species group laurae, based on morphological evidence supported by other biological information. It has been discovered at two locations in southeast Spain. This species is a member of the laurae species group. Based on the morphological measurements of the queens and the workers, as well as our observations in the laboratory, we predict that this species has a dependent colony founding.