Effect of treefall gaps on the patchiness and species richness of Neotropical ant assemblages

Abstract

Natural formation of treefall gaps plays an integral role in the ecological and evolutionary dynamics of many tropical forests, affecting the spatiotemporal distribution of plants and the animals that interact with them. This study examines the impact of treefall gaps on the spatial and temporal patchiness of ant assemblages in a moist lowland forest in Panama. Using pitfall traps and honey baits, we compared ant assemblages in five 1 to 2-year-old treefall gaps (ca 100 m) and five adjacent plots (ca 100 m) in undisturbed forest understory at three different times of year (late wet season, late dry season, and early wet season). We found little evidence that ant assemblages respond dramatically to the formation of treefall gaps and the differences in habitat qualities they produce. Ant abundance, species richness, species composition, and rates of resource discovery did not differ between gaps and forest understory. However, we did find significant differences in numerical abundance related to forest stratum (ground vs vegetation) and resource type in pitfall traps (oil-cockroach vs honey), and significant differences in ant species richness and rates of resource discovery across seasons. While habitat effects by themselves were never statistically significant, habitat and seasonal differences in species richness interacted significantly to produce complex, season-dependent differences among gap and forest habitats. These results suggest that the formation of natural treefall gaps has less of an effect on Neotropical ant assemblages compared to other groups of organisms (e.g., plants, birds) or other causes of patchiness (e.g., ant mosaics, moisture availability, army ant predation). The results of our study also have important implications for the underlying causes of habitat differences in the distribution of ant-defended plants.

Using nutritional ecology to predict community structure: a field test in Neotropical ants

“…BCI has a long history of ant studies (Levings and Franks 1982, Kaspari 1996, Feener and Schupp 1998) and a well-documented fauna of ca. 400 species (Donoso in prep).…”

Efeitos da distância entre iscas nas estimativas de abundância e riqueza de formigas em uma floresta de terra-firme na Amazônia Central

“…Muitos trabalhos investigaram os efeitos do tipo de iscas (Davidson, 1997;Feener Jr. e Schupp, 1998;Bestelmeyer et al, 2000;Yanoviak e Kaspari, 2000;Kaspari e Yanoviak, 2001) ou de variações ambientais (Cerdá et al, 1998;Bestelmeyer, 2000;Hahn e Wheeler, 2002;Silva et al, 2004) na resposta comportamental e, consequentemente, na eficiência de amostragem das espécies. No entanto, a distância entre iscas também pode afetar o forrageamento das formigas e alterar os resultados da amostragem.…”

Seasonal variation of arthropod abundance in gaps and the understorey of a lowland moist forest in Panama

“…These gaps play an important role in the species composition and diversity of plant and bird communities (Brokaw & Scheiner 1989, Hubbell et al 1999, Levey 1988, Ricklefs 1977, Schemske & Brokaw 1981, Schnitzer & Carson 2001. However, surprisingly, the role of gaps on insect communities has received little attention (Feener & Schupp 1998, Hill et al 2001, Shelly 1988. In this study, we explored differences in the arthropod communities between treefall gaps and the understorey.…”