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Revista chilena de historia natural

Print version ISSN 0716-078X

Abstract

VILLACIDE, JOSÉ M  and  CORLEY, JUAN C. The role of stand composition on pre-dispersal seed predation in Austrocedrus chilensis (Cupressaceae) in north west Patagonia. Rev. chil. hist. nat. [online]. 2008, vol.81, n.3, pp.387-393. ISSN 0716-078X.  http://dx.doi.org/10.4067/S0716-078X2008000300007.

We studied the variability of pre-dispersal seed predation by insects on Austrocedrus chilensis (Cupressaceae). This is a dioecious conifer endemic to southern South America (central Chile and the Chilean Argentinean Patagonia) that grows naturally in pure and mixed stands, typically in association with broadleaved Nothofagus species. Seeds are attacked while still inside the cones, mainly by larvae of Nanodacna austrocedrella (Lepidoptera: Elachistidae). Our working hypothesis was that observed variations in pre-dispersal seed damage levels were related to forest stand composition, specifically to the relative abundance of A. chilensis versus accompanying Nothofagus species. We compared seed predation levels in six pairs of sites using a block design which included a mixed and a pure stand for each paired site. At each site, we manually collected 50 closed seed cones from each of five neighbouring adult trees of A. chilensis. Pre-dispersal seed damage was highly variable among trees and sites, with values ranging between 16.7 to 73.0 % of seeds damaged. We found significant differences in predation rates among stands differing in canopy composition. In mixed stands, with Nothofagus, the proportion of seeds attacked was always greater than that observed in the paired pure A. chilensis stand. We showed that canopy composition influenced the level of pre-dispersal seed predation by insects, supporting the hypothesis that damage increases in mixed stands. Our study is the first to present data on variations of pre-dispersal seed predation in A. chilensis at a large spatial scale, examining the effects of forest type. This information may be useful in planning for commercial A. chilensis seed harvesting, as well as for the conservation this endemic conifer.

Keywords : Cupressaceae; insect herbivory; associational susceptibility; associational damage; Nanodacna austrocedrella.

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