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

Abstract

Treefalls gaps contribute to the habitat heterogeneity of tropical forest floors. Previous studies have shown that these gaps play an important role in plant and bird communities, however less is known about their role in arthropod communities. Using eight Malaise traps we investigated the difference in arthropod abundance of 19 taxonomic groups between gaps and understorey for 21 wk during the rainy season and 8 wk in the dry season on Barro Colorado Island, Panama. More (33.8%) arthropods were collected in gaps during the rainy season and 32.2% more in the understorey during the dry season. To assess the possible factors contributing to these differences we measured light, plant densities and young leaf densities, as indicators of abiotic factors and food resources for insect herbivores. Arthropod abundance was negatively correlated with light in the dry season. Thus, abiotic stress may explain the pattern of abundance in the dry season. While there was no correlation with light in the rainy season, predator abundance was positively correlated with herbivore abundance. The plant and young leaf density data suggest that there is significantly higher food availability for herbivores in gaps. Thus, less stressful abiotic conditions and more food resources may contribute to more herbivores followed by more predators in gaps during the rainy season.

When rare is just a matter of sampling: unexpected dominance of clubtail dragonflies (Odonata, Gomphidae) through different collecting methods at Parque Nacional da Serra do Cipó, Minas Gerais State, Brazil

“…The familial composition is not unexpected, given that Libellulidae was the most abundant taxon, and Corduliidae and Gomphidae the rarest. In spite of the large sampling effort and high richness, which are rare in studies using this trap, Flint's (1996) results show a comparatively smaller number of specimens compared to other methods like AN used during same period, and mirrors similar studies where the capture of dragonflies was considered accidental (Johnson et al 1995;Muzón & Spinelli 1995;Askew et al 1998;Rizali et al 2002;Richards & Windsor 2007;Sartor et al 2009). An exception is Glotzhober & Riggs (1998), who focused on the biology of Cordulegaster erronea Hagen in Selys, 1878, in which a modified Townes MT sampled a total of 142 specimens during only two summer seasons with irregular numbers of days and traps.…”

“…The material from PNSC is rich when compared to other studies using insect traps, especially considering the short sampling period of only nine days (see Corbet 1981;Borisov 1990;Johnson et al 1995;Muzón & Spinelli 1995;Flint 1996;Askew et al 1998;Glotzhober & Riggs 1998;Sharma et al 2000;Rizali et al 2002;Borisov 2004;Richards & Windsor 2007;Sartor et al 2009;Umar et al 2012). Gomphidae had the highest abundance, with 76 specimens (seven species), followed by Libellulidae with 19 specimens (eight species).…”

Herbivory, growth rates, and habitat specialization in tropical tree lineages: implications for Amazonian beta‐diversity

“…Saplings in the understory are thought to be mostly light limited, waiting for a gap to allow them the chance to grow to the canopy and become a reproductive adult (Wright 2002). Insect herbivores are also less likely to be attracted to shady environments (Richards and Windsor 2007), and in general, lower overall leaf biomass and insect herbivore abundances are found in the understory of undisturbed forests compared to edges of light gaps (Whitfeld et al 2012). Further research integrating herbivory rates for the same species across different life history stages, and across light environments, will be critical to fully evaluate the true relationship between growth and herbivory rates.…”

Light intensity affects spatial distribution of Heteroptera in deciduous forests

“…Plant performance, composition and diversity change in response to changes in illumination (Pavlovic et al, 2006), which indirectly affect insect distribution and diversity (De Cauwer et al, 2006;Richards & Windsor, 2007). In addition, the intensity of sunlight affects the concentration of secondary plant compounds in leaves and therefore insect performance (Dudt & Shure, 1994;Le Corff & Marquis, 1999).…”