As the dominant seed dispersal agents in many ecosystems, frugivorous animals profoundly impact gene movement and fine-scale genetic structure of plants. Most frugivores engage in some form of destination-based dispersal, in that they move seeds towards specific destinations, resulting in clumped distributions of seeds away from the source tree. Molecular analyses of dispersed seeds and seedlings suggest that destination-based dispersal may often yield clusters of maternal genotypes and lead to pronounced local genetic structure. The long-wattled umbrellabird Cephalopterus penduliger is a frugivorous bird whose lek mating system creates a species-specific pattern of seed dispersal that can potentially be distinguished from background dispersal processes. We used this system to test how destination-based dispersal by umbrellabirds into the lek affects gene movement and genetic structure of one of their preferred food sources Oenocarpus bataua, a canopy palm tree. Relative to background dispersal processes, umbrellabird mating behaviour yielded more diverse seed pools in leks that included on average five times more seed sources and a higher incidence of long-distance dispersal events. This resulted in markedly lower fine-scale spatial genetic structure among established seedlings in leks than background areas. These species-specific impacts of destination-based dispersal illustrate how detailed knowledge of disperser behaviour can elucidate the mechanistic link driving observed patterns of seed movement and genetic structure.

Frugivores exhibit considerable variation in the seed dispersal services they provide. Understanding what drives these differences is a key goal for ecologists because of the central role seed dispersal plays in shaping ecological and genetic diversity in plant populations. The lek-mating system of the Long-wattled Umbrellabird (Cephalopterus penduliger) provides a powerful lens to examine how mating behavior may impact seed dispersal outcomes. As in all lek-breeding species, male Umbrellabirds congregate in traditional sites (leks) to display, whereas females are solitary and visit leks only rarely. This study demonstrates how differences in mating behavior between the sexes drive distinctive seed movement and deposition patterns by male vs. female Umbrellabirds. Using radio tracking and gut retention trials, we documented divergent movement patterns between the sexes that are directly attributable to mating behavior differences. These movement differences led males to disperse seeds long distances from source trees and to deposit the majority of seeds they ingested within the lek; females dispersed seeds shorter distances and more evenly across the landscape. We empirically confirmed that the density of dispersed seeds was higher in leks than in control areas outside the lek, yet found no evidence that this higher density of seeds in leks reduced probability of seedling establishment. This research not only provides a mechanistic explanation for long dispersal distances and high levels of genetic diversity previously reported for seeds in Umbrellabird leks, but also highlights the importance of explicitly considering behavior in studies of animal-mediated seed dispersal.Abstract in Spanish is available in the online version of this article.

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Comunidade de Besouros Rola-Bosta (Coleoptera: Scarabaeidae) ao Longo de um Ecótono Natural Entre Floresta e Cerrado em Minas Gerais RESUMO -Variações em comunidades ao longo de ecótonos fornecem exemplos claros de como os organismos percebem e respondem a mudanças ambientais, mesmo em escalas reduzidas. Besouros rola-bosta (Scarabaeidae) têm sido usados como bioindicadores de qualidade de hábitat devido à sua sensibilidade a mudanças ambientais. Neste estudo, foram feitas amostragens de escarabeídeos ao longo de um ecótono natural entre hábitats de floresta e cerrado no Brasil e examinaram-se as mudanças associadas na estrutura da comunidade. Também foram examinados os efeitos de borda, aqui definidos como mudanças consistentes em atributos da comunidade em relação à distância da borda entre os dois hábitats. Densidades de indivíduos e espécies foram maiores na floresta do que no cerrado, porém a riqueza total foi similar entre os dois hábitats depois que as diferenças em tamanho amostral foram controladas. A composição de espécies foi bastante diferente entre a floresta e o cerrado, e as espécies compartilhadas pelos dois hábitats foram consistentemente mais abundantes em um ou outro. Efeitos de borda não foram detectados na riqueza ou composição de espécies, e apenas efeitos sutis foram observados na abundância. Conclui-se que o tipo de hábitat tem um efeito muito mais acentuado na estrutura da comunidade do que a presença da borda: escarabeídeos responderam fortemente à mudança de hábitat, mas muito mais sutilmente à proximidade da borda entre os dois hábitats.PALAVRAS-CHAVE: Biodiversidade, Mata Atlântica, efeito de borda, distribuição espacial ABSTRACT -Variations in assemblage attributes across ecotones provides clear examples on how organisms perceive and respond to environmental changes, even at small scales. Dung beetles (Scarabaeidae) have been used as bioindicators of habitat quality due to their sensitivity to environmental changes. Dung beetles were sampled across a natural forest-cerrado ecotone in Brazil, and associated changes in assemblage structure were examined. Edge effects, here defined as consistent changes in assemblage parameters in relation to the distance to the forest-cerrado border, were also examined. Density of individuals and species were higher in the forest than in the cerrado, but overall richness was similar between habitats after controlling for sample sizes. Species composition differed greatly between habitats, and shared species were consistently more abundant in one or another habitat. Edge effects were not detected on richness nor species composition, and only weak effects were observed on abundance. It is concluded that the effect of the habitat (forest vs. cerrado) has a much stronger effect on the assemblage structure than the presence of the edge: dung beetles responded strongly to change in habitats, but weakly to the proximity of the edge between these habitats.

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Environmental correlates and geographic spacing of leks were compared for six species of manakins (Pipridae) on two 100-ha study plots in eastern Ecuador. The “hotspot” hypothesis of lek evolution suggests that males should aggregate where females are most likely to be encountered. For ecologically similar species that co-occur at a site, leks are predicted to be clustered in space and, thus, to overlap in macroscale environmental characteristics. The geographic spacing and environmental characteristics of lek sites we observed were inconsistent with the hotspot hypothesis for lek evolution. In general, little geographic overlap occurred among leks, and geographic spacing of leks among heterospecifics more closely fit a regular than a clumped pattern. Further, environmental conditions of leks varied among species with respect to elevation and topography. Leks of some species were more likely to occur on hilltops or ridge tops (e.g., Machaeropterus regulus, Pipra erythrocephala), whereas others appeared to prefer highly dissected drainages (e.g., P. pipra), relatively flat terrain near streams (e.g., Chiroxiphia pareola), or seasonally inundated forests (e.g., P. filicauda). Using randomly placed leks, we found evidence that certain lek environments may be limited, which is consistent with observed levels of population abundances on the two plots. Such environmental limits may constrain lek placement and size. Further study is needed to determine the reproductive implications of placing leks in apparently suboptimal environments, though such compromises may reflect males making the best of a bad situation.Segregación Ambiental y Espacial de las Asambleas de Cortejo Entre Seis Especies Simpátricas de Saltarines (Pipridae) en el Oriente de Ecuador