Publications

Seed dispersal shapes ecological and evolutionary dynamics of plant populations. Here, we extend classical diversity measures to study the impact of disperser behavior on seed dispersal. We begin by extending our previous diversity structure approach, which partitioned seed source diversity within and among dispersal sites, into the more general framework of traditional diversity measures. This statistical approach allows an assessment of the extent to which foraging behavior shapes α and γ diversity, as well as the divergence in seed sources among dispersal sites, which we call δ. We also introduce tests to facilitate comparisons of diversity among dispersal sites and seed vectors and to compare overall diversity among sampled systems. We then apply these tools to investigate the diversity blend of parentage resulting from seed dispersal by two avian seed vectors with very different social and foraging behaviors: (1) acorn woodpeckers, transporting Quercus agrifolia acorns, and (2) long-wattled umbrellabirds, transporting Oenocarpus bataua palm nuts. Using these diversity and divergence measures, we test the hypothesis that different foraging behaviors generate distinctive diversity partitions for the two focal tree species. This approach provides a new tool for assessment of the impact of dispersal agents on the seed source structure of plant populations, which can be extended to include the impact of virtually any propagule vector for a range of systems.

Seed dispersal by birds is thought to profoundly impact patterns of ecological and genetic diversity in many plant species. As such, a more refined understanding of avian seed dispersal dynamics in the Neotropics is a subject of intense interest for ecologists, evolutionary biologists, and conservation biologists. We provide an overview of emerging research themes and approaches in the field of seed dispersal by beotropical birds, followed by five detailed case studies of current work. The common theme uniting our research is the integration of spatial and temporal seed deposition patterns with underlying mechanistic processes and ecological consequences. We use contemporary methods in molecular analyses, GPS-based and radiobased animal tracking, field-based observation and experimentation, and network theory to address the common theme of how avian seed dispersal impacts plant species and communities. The over-arching conclusion of this symposium is that species composition and foraging ecology of neotropical birds have important consequences (e.g., moving seeds long distances and/or to favorable microsites seedling establishment, equalizing the abundance of common and rare seeds in seed rain, increasing genetic heterogeneity of seedling populations), which in turn are likely to shape the initial template of genetic structure among seedlings, local densities of adult plants, functional traits of plant species, and even patterns of community assembly.

Pollen dispersal shapes the local genetic structure of plant populations and determines the opportunity for local selection and genetic drift, but has been well studied in few animal-pollinated plants in tropical rainforests. Here, we characterise pollen movement for an insect-pollinated Neotropical canopy palm, Oenocarpus bataua, and relate these data to adult mating system and population genetic structure. The study covers a 130-ha parcel in which all adult trees (n ¼ 185) were mapped and genotyped at 12 microsatellite loci, allowing us to positively identify the source tree for 90% of pollination events (n ¼ 287 of 318 events). Mating system analysis showed O. bataua was effectively outcrossed (tm ¼ 1.02) with little biparental inbreeding (tm ts ¼ 0.005) and an average of 5.4 effective pollen donors (Nep) per female. Dispersal distances were relatively large for an insect-pollinated species (mean ¼ 303 m, max ¼ 1263 m), and far exceeded nearest-neighbour distances. Dispersal kernel modelling indicated a thin-tailed Weibull distribution offered the best fit to the genetic data, which contrasts with the fat-tailed kernels typically reported for pollen dispersal in trees. Preliminary analyses suggest that our findings may be explained, at least in part, by a relatively diffuse spatial and temporal distribution of flowering trees. Comparison with previously reported estimates of seed movement for O. bataua suggests that pollen and seed dispersal distances may be similar. These findings add to the growing body of information on dispersal in insect-pollinated trees, but underscore the need for continued research on tropical systems in general, and palms in particular

The Amazonian avifauna remains severely understudied relative to that of the temperate zone, and its species richness is thought to be underestimated by current taxonomy. Recent molecular systematic studies using mtDNA sequence reveal that traditionally accepted species-level taxa often conceal genetically divergent subspecific lineages found to represent new species upon close taxonomic scrutiny, suggesting that intraspecific mtDNA variation could be useful in species discovery. Surveys of mtDNA variation in Holarctic species have revealed patterns of variation that are largely congruent with species boundaries. However, little information exists on intraspecific divergence in most Amazonian species. Here we screen intraspecific mtDNA genetic variation in 41 Amazonian forest understory species belonging to 36 genera and 17 families in 6 orders, using 758 individual samples from Ecuador and French Guiana. For 13 of these species, we also analyzed trans-Andean populations from the Ecuadorian Choco´. A consistent pattern of deep intraspecific divergence among transAmazonian haplogroups was found for 33 of the 41 taxa, and genetic differentiation and genetic diversity among them was highly variable, suggesting a complex range of evolutionary histories. Mean sequence divergence within families was the same as that found in North American birds (13%), yet mean intraspecific divergence in Neotropical species was an order of magnitude larger (2.13% vs. 0.23%), with mean distance between intraspecific lineages reaching 3.56%. We found no clear relationship between genetic distances and differentiation in plumage color. Our results identify numerous genetically and phenotypically divergent lineages which may result in new species-level designations upon closer taxonomic scrutiny and thorough sampling, although lineages in the tropical region could be older than those in the temperate zone without necessarily representing separate species. In-depth phylogeographic surveys are urgently needed to avoid underestimating tropical diversity, and the use of mtDNA markers can be instrumental in identifying and prioritizing taxa for species discovery

Males of monogamous species are expected to increase their overall fitness by engaging in extrapair copulations, but the fitness implications of this behavior for females are somewhat less clear. Numerous studies have examined the potential benefits of extrapair mating to females, but the costs of extrapair mating, which may be substantial, are less well studied. Quantifying these costs is critical to understanding the evolution of extrapair mating behavior in females. We examined the costs of extrapair paternity to female Red-backed Fairy-wrens (Malurus melanocephalus) using an -year data set that allowed us to examine both short-term and long-term costs. The variability of individual extrapair mating behavior in female Red-backed Fairy-wrens allowed us to compare the parental care, fecundity, and apparent survival of faithful and promiscuous females. We found no effect of the presence of extrapair offspring on the rate at which males provisioned broods. We also found that promiscuous and faithful females did not differ with respect to apparent annual survival and four indices of reproductive success. These findings suggest that there are few or no costs to extrapair mating in females in this population. Low costs, as documented here, may contribute to the evolution of high extrapair paternity rates observed in many species; thus, our results underscore the importance of both costs and benefits in explaining the evolution of extrapair mating behavior in females. Received  October , accepted  April .

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

Although some group-living animals dynamically modify sexual signals in response to changes in social or reproductive status, this ability is often limited by constraints inherent in the mechanism of signal production. In birds, for example, inflexible moult schedules may restrict the ability to rapidly modify plumage-based signals. In such cases, more flexible secondary signals such as skin, eye, or bill coloration (e.g. soft parts) could potentially be used to achieve dynamic signalling. We addressed the degree to which free-living red-backed fairy-wrens, Malurus melanocephalus, can dynamically update both plumage and soft part signals when status suddenly changes, and how this may be achieved. In this cooperatively breeding passerine, dominant breeding males are distinguished from socially subordinate nonbreeding auxiliary males by the presence of nuptial plumage, dark bills and large sperm storage organs. Following an experimentally induced shift in status from auxiliary to breeder, males showed rapid increases in excreted androgen metabolites. Although they showed no overall change in nuptial plumage colour, several experimental males developed red nuptial feathers on the back following feather plucking, indicating that they had the capacity to develop bright nuptial plumage but were constrained from doing so by the moult schedule. In contrast, experimental males showed a rapid darkening of their bills, reflecting their newly acquired breeding status. These findings (1) provide experimental evidence that status affects physiologically controlled visual signals in free-living birds, (2) suggest that this linkage is mediated by testosterone and (3) illustrate how secondary ornaments may be used in dynamic signalling when the primary signalling modality is constrained.

The Brown Wood Rail (Aramides wolfi) is a globally threatened, poorly known species endemic to the Choco´ rain forests of South America. We provide a first report on the species’ nesting biology, home range, and habitat use. Nests (n 5 16) were open cups ,2 m above ground and were more common in secondary forest than expected by chance. Median clutch size was four eggs, incubation lasted .19 days, the precocial young departed the nest within 24 hrs of hatching, and 66% of nests successfully produced young. At least two adults participated in parental care and pair bonds appear to be maintained year-round. The home range of an adult radio-tracked for 7 months was 13.5 ha in secondary and selectively-logged forest contiguous to primary forest. This easily overlooked species may be more resilient to moderate levels of habitat degradation than previously suspected, but extensive deforestation throughout its range justifies its current status as ‘Vulnerable to Extinction’. Received 24 February 2010. Accepted 28 July 2010

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 speciesspecific 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. Keywords: animal behaviour, choco´ rain forest, gene flow, lek mating system, maternity analysis, seed movement