Environmental factors, spatial variation, and specific requirements of Chironomidae in Mediterranean reference streams

Chironomidae spatial distribution was investigated at 63 near-pristine sites in 22 catchments of the Iberian Mediterranean coast. We used partial redundancy analysis to study Chironomidae community responses to a number of environmental factors acting at several spatial scales. The percentage of variation explained by local factors (23.3%) was higher than that explained by geographical (8.5%) or regional factors(8%). Catchment area, longitude, pH, % siliceous rocks in the catchment, and altitude were the best predictors of Chironomidae assemblages. We used a k-means cluster analysis to classified sites into 3 major groups based on Chironomidae assemblages. These groups were explained mainly by longitudinal zonation and geographical position, and were defined as 1) siliceous headwater streams, 2) mid-altitude streams with small catchment areas, and 3) medium-sized calcareous streams. Distinct species assemblages with associated indicator taxa were established for each stream category using IndVal analysis. Species responses to previously identified key environmental variables were determined, and optima and tolerances were established by weighted average regression. Distinct ecological requirements were observed among genera and among species of the same genus. Some genera were restricted to headwater systems (e.g., Diamesa), whereas others (e.g., Eukiefferiella) had wider ecological preferences but with distinct distributions among congenerics. In the present period of climate change, optima and tolerances of species might be a useful tool to predict responses of different species to changes in significant environmental variables, such as temperature and hydrology.

El carácter fronterizo de las identidades contemporáneas: el caso de Chiapas

The thesis or hypothesis of this paper is that the multiple connections of explicit andimplicit life styles foster the construction of hybrid, multiple or complex identities. Wemean by hybrid identities the confluence of multiple identifications in the personalbiography. If the globalization and cultural diversity are the fundamental forms ofglobal life, the mobility is its principal ingredient. We describe different cultural traitsin Chiapas. Internet, migration to United States, or the North American Free TradeAgreement (NAFTA), between North America, Canada, and Mexico, were hybridizedwith the heterogeneity of identity (ethnic, linguistic, and religious). It is discussed thesocial and political consequences of the hybrid contemporary societies