Revista Chilena de Historia Natural 83 (2): 267-287, 2010
RESEARCH ARTICLE
Distribution of macroinvertebrates (Plecoptera and Aeglidae) in fluvial ecosystems of the
Chilean Patagonia: Do they show biological signals of the postglacial geomorphological evolution?
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 m<sup>2</sup>
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 (R<sup>2</sup> = 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 (R<sup>2</sup> = 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.
Key words:
Aegla, biodiversity, biogeography, Patagonia, Plecoptera
