Competition with insectivorous ants as a contributor to low songbird diversity at low elevations in the eastern Himalaya

Free-feeding organisms and galling insects (Hymenoptera) interactions on Caryocar brasiliense (Malpighiales: Caryocaraceae) trees, a savanna plant from Brazil

Abstract Galling insects are abundant in nature, found in many ecosystems globally, with species attacking plants of economic importance. We studied the effects of free-feeding organisms on the abundance of galling insects on Caryocar brasiliense (Caryocaraceae) trees in the Brazilian Cerrado (Savanna). Percentage of defoliation and the number of phytophagous mites or number of phytophagous Hemiptera correlated negatively with percentage of galled leaves and the parasitoid Eurytoma sp. (Hymenoptera: Eurytomidae) adults, respectively. Percentage of galled leaves and the numbers of Eurytoma sp. adults and phytophagous mites correlated positively with spiders. Numbers of mites and Hemiptera phytophagous correlated positively with those of lady beetles and Sycophila sp. (Hymenoptera: Eurytomidae), respectively. The number of Ablerus magistretti Blanchard (Hymenoptera: Aphelinidae) adults correlated negatively with Sycophila sp. The number of Agistemus sp. (Acari: Stigmaeidae) correlated, negatively and positively, with those of lady beetles and phytophagous mites, respectively. Free-feeding herbivores affected the presence of galling insects (Hymenoptera) on C. brasiliense trees, competing for food and space. The same was observed between two parasitoids of Eurytoma sp. galling insect, which can reduce the natural biological control of this pest.

Intraspecific trait variability and community assembly in hawkmoths (Lepidoptera: Sphingidae) across an elevational gradient in the eastern Himalayas, India

We investigated some aspects of hawkmoth community assembly at 13 elevations along a 200- to 2770-m transect in the eastern Himalayas, a little studied biodiversity hot spot of global importance. We measured the morphological traits of body mass, wing loading, and wing aspect ratio of 3,301 free-ranging individuals of 76 species without having to collect or even constrain them. We used these trait measurements and T-statistic metrics to assess the strength of intracommunity ("internal") and extra-community ("external") filters which determine the composition of communities vis-a-vis the regional pool of species.The trait distribution of constituent species turned out to be nonrandom subsets of the community-trait distribution, providing strong evidence for internal filtering in all elevational communities. The external filter metric was more ambiguous. However, the elevational dependence of many metrics including that of the internal filter provided evidence for external (i.e., environmental) filtering. On average, a species occupied as much as 50%-75% of the total community-trait space, yet the T-statistic metric for internal filter was sufficiently sensitive to detect a strong nonrandom structure in the trait distribution.We suggest that the change in T-statistic metrics along the environmental gradient may provide more clues to the process of community assembly than previously envisaged. A large, smoothly varying and well-sampled environmental span would make it easier to discern them. Developing T-statistics for combined analysis of multiple traits will perhaps provide a more accurate picture of internal/filtering and niche complementarity. Moths are a hyperdiverse taxon and a very important component of many ecosystems. Our technique for accurately measuring body and wing dimensions of free-ranging moths can generate trait database for a large number of individuals in a time- and resource-efficient manner for a variety of community assembly studies using this important taxon.