Anthropogenic pressures such as hunting are increasingly driving the localized functional extinctions of all or most large and medium-sized wildlife species in tropical forests, a phenomenon broadly termed defaunation. Concurrently in these areas, smaller-bodied wildlife species benefit from factors such as competitive release and experience population increases. This transformation of the wildlife community can impact species interactions and ecosystem services such as seed dispersal and seed-mediated geneflow with far reaching consequences. Evidence for negative genetic effects following defaunation is well-documented in large-seeded plants that require large frugivores for long distance seed dispersal. However, how defaunation affects small-seeded (< 1.5cm diameter) plants, which are dispersed by frugivores with a wide range of body-sizes and responses to anthropogenic threats, is not well understood. To better understand the reach of defaunation’s impacts on tropical plant communities, we investigated spatial and genetic patterns in a hyperabundant small-seeded palm, Euterpe precatoria in three sites representing distinct defaunation levels. We found significantly higher fine-scale spatial genetic structure among nearest-neighbor seedlings in the defaunated site and in the recovering, partially defaunated site relative to the faunally-intact site. Defaunation was associated with shorter distances between seedlings and adults and lower genetic distance between adult and seedling cohorts. No effects were detected on inbreeding and genetic diversity; however, we caution that trends we detected indicate that defaunation influences the spatial distribution of genetic variation even in small-seeded plants that inherently have a broad suite of seed dispersal agents, and this could lead to negative downstream effects on genetic diversity.

Conspicuous female signals have recently received substantial scientific attention, but it remains unclear if their evolution is the result of selection acting on females independently of males or if mutual selection facilitates female change. Species that express female, but not male, phenotypic variation among populations represent a useful opportunity to address this knowledge gap. White-shouldered fairywrens (Malurus alboscapulatus) are tropical songbirds with a well-resolved phylogeny where female, but not male, coloration varies allopatrically across subspecies. We explored how four distinct signaling modalities, each putatively associated with increased social selection, are expressed in two populations that vary in competitive pressure on females. Females in a derived subspecies (M. a. moretoni) have evolved more ornamented plumage and have shorter tails (a signal of social dominance) relative to an ancestral subspecies (M. a. lorentzi) with drab females. In response to simulated territorial intrusions broadcasting female song, both sexes of M. a. moretoni are more aggressive and more coordinated with their mates in both movement and vocalizations. Finally, M. a. moretoni songs are more complex than M. a. lorentzi, but song complexity does not vary between sexes in either population. These results suggest that correlated phenotypic shifts in coloration and tail morphology in females as well as song complexity and aggression in both sexes may have occurred in response to changes in the intensity of social selection pressures. This highlights increased competitive pressures in both sexes can facilitate the evolution of complex multimodal signals.

Historically, bird song complexity was thought to evolve primarily through sexual selection on males, yet in many species both sexes sing. Previous research suggests competition for mates and resources during short, synchronous breeding seasons leads to more elaborate male songs at high latitudes. In contrast, we expect male-female song dimorphism and elaboration to be more similar at lower latitudes because longer breeding seasons and year-round territoriality yield similar social selection pressures in both sexes. However, studies seldom take both selective pressures and sexes into account. We examined song elaboration and sexual dimorphism in 15 populations of nine fairy-wren species (Maluridae), a Southern Hemisphere clade with female song. We compared song elaboration and sexual song dimorphism to latitude and life history variables tied to sexual and social selection pressures and sex roles. Our results suggest that song elaboration evolved in part due to sexual competition in males: male song variability was more positively correlated with temperate breeding and greater breeding synchrony than female song. We also found strong evidence that sex-role similarity contributed to male-female song similarity: male and female songs were shorter and more similar when parental care was more equal and when male survival was high. Contrary to Northern Hemisphere latitudinal patterns, songs were less dimorphic at higher, temperate latitudes. These results suggest that selection on song can be sex-specific, with male song elaboration favored in contexts coincident with sexual selection. However, selection pressures associated with sex-role similarity also appear to constrain sex specific song evolution and song dimorphism.