Avian gut-passage effects on seed germination of shrubland species in Mediterranean central Chile

摘要

Effects of avian gut-passage on seed germination are important to assess the effectiveness of frugivores in woodland regeneration, particularly in biodiversity hotspots that have a high incidence of avian frugivory. We examined the effect of avian gut-passage on seed germination in contrast to seeds that remain uneaten in five shrub species in Mediterranean central Chile and sought to determine the physiological mechanism(s) by which seed germinability is modified. Germination assays were conducted in a glasshouse for five common shrub species of the sub-Andean matorral: Azara dentata (Flacourtiaceae), Schinus polygamus and Schinus molle (Anacardiaceae), Cestrum parqui (Solanaceae), and Maytenus boaria (Celastraceae). We estimated germinability (final percent germination), dormancy length (time from sowing to first germination), mean length of dormancy of all germinated seeds, and contrasted germination rates of defecated versus manually extracted and pulp-enclosed seeds. Avian gut-passage increased seed germinability in four of the five shrub species studied—primarily through deinhibition via pulp removal. Minimum dormancy length was not modified by avian gut-passage for A. dentata, but was significantly shorter for S. molle and C. parqui. Mean dormancy length was significantly shorter in gut-passed seeds of A. dentata, S. molle and M. boaria. Avian gut-passage greatly enhanced the seed germination rates of three species, A. dentata, S. molle and C. parqui. We conclude that the positive effects of birds on seed germination facilitate the regeneration of sub-Andean shrublands, and that bird declines due to landscape change may impair recovery rates of successional or restored areas due to dispersal limitation.