Fruit production, migrant bird visitation, and seed dispersal of Guarea glabra in Panama

The relationship between bird visitation and the size of the available fruit crop was studied at an understory tree ( Guarea glabra Vahl, Meliaceae) in the tropical wet forest of Barro Colorado Island, Panama Canal Zone. Twelve resident species and seven North American migrant species fed on the Bright orange arilloids (seeds with arils), which were not depleted during the normal fruiting period. The number of individual visitors, the number of visiting species, and the number of seeds removed increased linearly with the size of the available fruit crop. The proportion of seeds removed did not increase with the size of the available fruit crop, indicating that dispersal is a function of the number of fruit available and not a disproportionate function of large fruit displays. Four species of North American migrants ( Myiarchus crinitus, Catharus ustulatus, Vireo olivaceus , and Vermivora peregrina ) accounted for 70% of the visits and 60% of the seeds removed from the trees. No resident species visited Guarea as frequently as any one of these migrants. There was no indication that any single visitor was dependent on this tree for nutrition, nor that the tree was dependent upon any single species for dispersal. We hypothesize that the fruiting season of G. glabra is adaptively synchronized with northward migration of opportunistically frugivorous North American birds.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47724/1/442_2004_Article_BF00348067.pd

Out of Amazonia again and again: episodic crossing of the Andes promotes diversification in a lowland forest flycatcher

Most Neotropical lowland forest taxa occur exclusively on one side of the Andes despite the availability of appropriate habitat on both sides. Almost all molecular phylogenies and phylogenetic analyses of species assemblages (i.e. area cladograms) have supported the hypothesis that Andean uplift during the Late Pliocene created a vicariant barrier affecting lowland lineages in the region. However, a few widespread plant and animal species occurring in lowland forests on both sides of the Andes challenge the generality of this hypothesis. To understand the role of the Andes in the history of such organisms, we reconstructed the phylogeographic history of a widespread Neotropical flycatcher (Mionectes oleagineus) in the context of the other four species in the genus. A molecular phylogeny based on nuclear and mitochondrial sequences unambiguously showed an early basal split between montane and lowland Mionectes. The phylogeographic reconstruction of lowland taxa revealed a complex history, with multiple cases in which geographically proximate populations do not represent sister lineages. Specifically, three populations of M. oleagineus west of the Andes do not comprise a monophyletic clade; instead, each represents an independent lineage with origins east of the Andes. Divergence time estimates suggest that at least two cross-Andean dispersal events post-date Andean uplift