Ants (Hymenoptera: Formicidae) as an indicator group of human environmental impact in the riparian forests of the Guadalquivir river (Andalusia, Spain)

Riparian forests play multitude of fundamental roles in the preservation of the environment. In order to assess its conservation state, different indexes can be used, such as the QBR (‘Qualitat del bosc de ribera’) that estimates conservation status of the riparian forest. Another widely used way of estimating the state of an ecosystem can be based on bioindicator groups, such as ants (Hymenoptera: Formicidae). In this work we intend to demonstrate that ants are an excellent bioindicator group of the riparian forests quality, comparing them with a widely used and extend index (QBR) in the Mediterranean basin. In this study we sampled the ant communities using pitfall traps in 14 riparian forest of the Guadalquivir River. The captured ants were identified and the abundance in number of workers of each species was determined. Also, we determined the perturbation variables (QBR index, nearest urban centres and nearest urban centres >20,000 inhabitants) for each area. A total of 41 species were found in the sampled areas and high correlations were obtained between the QBR index and the Shannon index, Equitability and number of species. Using multivariate analysis (PLS and Non-Metric MDS), a strong correlation was found between perturbation variables and abundance per species in each grove, as well as a strong correlation between perturbation variables themselves.Therefore, we can affirm that ants are a good indicator to estimate the state of conservation of riparian forest, since they are highly correlated with different variables that estimate the state of conservation. In a certain way, a high QBR index will be linked to diverse ecosystems. In addition, greater distances to urban centres, which are sources of anthropic disturbance, will be linked to less diverse ecosystems. It has also been detected in the sampled groves that there is a certain amount of species that are related to a good state of conservation (QBR), such as Temnothorax pardoi, Temnothorax recedens and Camponotus lateralis. Analogously, it has been detected that Hypoponera eduardi is a common species in groves with worse state of conservation.