Distribución de macroinvertebrados (Plecoptera y Aeglidae) en ecosistemas fluviales de la Patagonia Chilena: ¿muestran señales biológicas de la evolución geomorfológica postglacial?

Abstract

The Chilean Patagonia includes one of the most complex hydrological systems of South America and one of the least modified systems of the world. These systems were intensely modified by the glacial activity of the Quaternary. The objectives of this study were to determine whether or not in this area exists zones of endemic benthic fluvial macroinvertebrates, and to analyze the patterns of diversity of species composed by organisms of high (Plecoptera) and low (Aeglidae) vagility. A collection of 183 selected sites, located between the latitude 42°50' and 54°43' S, were sampled during 2006 and 2009. The sampling was focused on the main river basins and a "kicknet" was used to cover a surface of 8 m2 at the bottom of the river channel. In all sampled areas, thirty Plecoptera and two Aeglidae species were recorded. One zone dominated by endemic species was identified in the Aysen river basin, which included the Plecoptera Ceratoperla fazi and the crab Aegla neuquensis. The last species belong to an ancient population found in the river steppes of Argentina, and may have been locked in the Chilean Patagonia when the channel flow was reversed from its original discharge towards the Atlantic Ocean. A distinct latitudinal change in the diversity of species was noticed throughout the study area (R2 = 0.72, P < 0.05), showing a gradient of decreasing species richness towards the south. The regression analysis between species richness and annual mean temperature was significant (R2 = 0.67, P < 0.05). This suggests that the input of solar energy had an important effect on species diversity. In addition, the historical events would have had weaker impacts relative to current ecological requirements on organisms of high vagility. Conversely, low vagility organisms seemed to be largely affected by history. © Sociedad de Biología de Chile.