Abstract

Wetlands are one of the most productive ecosystems which provide a number of ecosystem functions, maintaining also a high biodiversity. Nevertheless, almost half of the wetlands in the world have disappeared in the last century due to urban development process. Along the Chilean landscape a great variety of aquatic habitats exist. Due to urban expansion those ecosystems have been exposed to strong anthropogenic pressures. In the intercomunal area Concepción-Talcahuano- San Pedro (Biobío Region), more than 23 % (1,734 ha) of the wetland areas have been lost in the last three decades. We evaluated the relationship between habitat characteristics (morphometric, limnology and vegetation) and the insect assemblage's structure in seven freshwater marshes in this intercomunal area. Our aim was to assess the influence of urbanization on the diversity patterns of these ecosystems. Insect abundance and species diversity were positively correlated to matrix pristinness and oxygen concentration of the water, this last feature was the best predictor for the structure of the insect assemblage. Of the 24 insect morphospecies included in the analysis, the abundance of only seven species was significantly related to the quantified habitat characteristics. Matrix pristinness, wetland area, vegetation heterogeneity and water oxygen concentration were positively related to species abundance, however, conductivity and water density showed a negative effect on the abundance. The insect species diversity decrease determined by the habitat characteristics associated to habitat loss, habitat fragmentation, habitat homogeneity, and wetland contamination, show that insects could be used as indicators of the urban effects on the functioning of these ecosystem. However, due to the missing biological and taxonomical information on the insect species related to freshwater marshes, only habitat characteristics with a significant effect on a high taxonomical level could be considered to establish initial recommendations for management plans. © 2006 Sociedad de Biología de Chile.