Primary seed dispersal by a sigmodontine rodent assemblage in a Peruvian montane forest

We examined quantity and quality components of primary seed dispersal for an assemblage of sigmodontine rodents in a high-elevation montane tropical forest in Peru. We collected faecal samples from 134 individuals belonging to seven rodent species from the subfamily Sigmodontinae (Cricetidae) over a 2-y period. We conducted seed viability tests for seeds found in faecal samples. We identified seeds from eight plant families (Bromeliaceae, Annonaceae, Brassicaceae, Ericaceae, Melastomatacae, Myrtaceae, Rosaceae, Solanaceae), nine genera and 13 morphospecies. The most abundant seeds belonged toGaultheriasp. 1 (46% of total) andMiconiasp. 1 (31% of total), while the most viable seeds belonged toGreigiasp. (84% viability) andGuatteriasp. (80% viability). We utilized relative rodent abundance, seed species diversity, seed abundance and seed viability per rodent species to calculate an index of rodent disperser effectiveness, and found thatThomasomys kalinowskiiwas the most effective disperser, followed byAkodon torques,Calomys sorellus,Thomasomys oreas,Oligoryzomys andinusandMicroryzomys minutus. Plant genera dispersed by sigmodontine rodents overlapped more with bird- and terrestrial-mammal-dispersed plants than with bat-dispersed plants. Future neotropical seed dispersal studies should consider small rodents as potential seed-dispersers, especially in tropical habitats where small-seeded, berry-forming shrubs and trees are present.

Effectiveness of Dispersal of an Ornithocorous Cactus Myrtillocactus geometrizans (Cactaceae) in a Patchy Environment

Effectiveness of seed dispersal by different species that feed on the fruits of Myrtillocactus geometrizans was evaluated, considering both quantity and quality of dispersal, in a patch of tropical deciduous forest in Zapotitlán de las Salinas. Effectiveness was estimated to be strongly influenced by the post-foraging movements of the frugivores, leading us to suggest that the quality component of seed dispersal occupies a central role in the assessment of disperser effectiveness and to expect that dispersers that stay in the tropical deciduous forest patch after foraging would have highest effectiveness. Birds were the principal dispersers of M. geometrizans. This was particularly true of Phainopepla nitens, since this species showed a high fidelity within the tropical deciduous forest. These observations emphasize that it is important to determine the post-foraging habits of seed dispersers that may move across vegetation patches over the landscape in order to obtain a complete assessment of their role in Neotropical environments.

The effect of gut processing on the quality of mistletoe seed dispersal

Disperser effectiveness is the contribution that a disperser makes to the future reproduction of a plant (Schupp 1993), and it has two components: quality and quantity of dispersal. Quantity of dispersal is a function of the number of visits that a disperser makes to a fruiting plant and the number of seeds that are dispersed during each visit. Quality of dispersal is a function of the treatment that a seed receives from its disperser and the site that the seed is finally deposited in. The quality of seed dispersal of the mistletoe Phragmanthera dschallensis (Engl.) M.G. Gilbert (Loranthaceae) by frugivorous birds was examined in this study.