Ants as storytellers in Mediterranean riverscapes

Doutoramento em Restauro e Gestão Fluviais / Instituto Superior de Agronomia / Faculdade de Arquitectura / Instituto Superior Técnico. Universidade de LisboaRiverscapes support high levels of biodiversity, but are increasingly threatened by global change drivers. Ants are among the most diverse and successful insects on earth and have the ability to respond well to environmental changes. There is a lack of knowledge on the factors that drive ant biodiversity in Mediterranean riverscapes. This thesis aims at studying ant communities in Mediterranean riverscapes, and understand how they respond to disturbance (e.g., land use and invasive species) and to structural attributes of the riverine landscape (e.g., patch typology, spatial configuration and habitat quality), in terms of their richness, abundance and ability to provide ecosystem services. For these purposes, we selected crop and non-crop habitats of the riverine mosaic of three main study areas: a) riparian corridors of Catalonia, Spain; b) riparian corridors and floodplain areas of central Portugal; and c) irrigated cropland of southern Portugal. Ant communities showed to be very sensitive to human-disturbance reflecting a broader perspective of the local ecological status. Based on ants’ responses to different stressors and landscapes elements, we found that land use was the main driver influencing ant communities. However, this might be dependent on the combined factors inherent to the overall disturbance of a particular land use. The Ecological Infrastructure (EI) of less disturbed systems, associated to a reduced abundance of invasive species, showed the highest capacity to provide ant-mediated services. In agricultural areas, ant species are likely recruited from ant communities of the neighbouring EI. Moreover, we found that the Argentine ant may negatively impact native ant communities, particularly in disturbed areas. This thesis has contributed to increment knowledge about ants in riverscapes by providing a biological assessment tool that takes full advantage of ants’ ability to indicate human-disturbance and by providing new insights on the role of EI in ant-diversity conservation in agroecosystems.N/

Formigas (Hymenoptera, Formicidae) associadas a pomares de citrinos na região do Algarve

Mestrado em Engenharia Agronómica - Instituto Superior de AgronomiaAnts (Hymenoptera, Formicidae) may play an important economic role in citrus orchards, either by causing damage in trees or induce pest’s outbreaks, due to interactions with injurious honeydew-producing insects, or even by being potential predators of other arthropods. In order to deepen knowledge about the ant species associated to citrus orchards, in the southern region of Portugal, Algarve, samples were collected in 49 citrus orchards, along the subregions of Litoral, Barrocal and Serra, between July and August 2007. In all, 2812 ants were identified comprising 12 different genera and 26 species. The most common species were Linepithema humile (Mayr), Plagiolepis pygmaea Latreille and Pheidole pallidula (Nylander). Nineteen species are reported for the first time in citrus, in Portugal, and ten are first records, in citrus, in the world. The higher number of species was found in the Serra subregion, with 19 species. Regarding economic importance, special attention must be paid to the phytophagous ants of Tapinoma genus, that can originate direct damage, and the argentine ant, L. humile, which interferes with the activity of natural enemies, disrupting biological control of pests