Effects of forest fragmentation on community patterns of social wasps (Hymenoptera: Vespidae) in Central Amazon

Abstract

Landscape fragmentation is one of the greatest threats to environments globally, affecting all living organisms within fragments at many assembly levels. Despite such general assumptions, very few reports exist on the diversity patterns of Amazonian social wasps (Polistinae) in response to fragmentation. Our study aims at addressing how the community patterns of social wasp change from continuous to fragmented landscapes in the Amazon rainforest. We collected social wasps for a year (11 520 trap-hour effort) in a continuous forest and a highly disturbed urban forest fragment, located in Manaus, Brazil. We attracted wasps using sardine and orange juice traps, placed in 20 sampling plots. We collected 2742 wasps from 29 species. Agelaia pallipes, Angiopolybia pallens and Agelaia fulvofasciata were the most abundant species. We detected significant differences in overall abundance, species richness and species composition of social wasps between landscapes. Conversely, no difference in species diversity (effective number of species) was found between habitats. Despite the low quantity of exclusive species, the numbers of most species declined sharply in the fragmented habitat, while for one species (Polybia rejecta), abundance increased. Regarding the percentile of species contribution to dissimilarity between landscapes, five out of the first six species were highly abundant (>100 individuals), thus demonstrating that the observed pattern was very likely driven by common species. Additionally, our findings highlight that fragmentation threatens abundant species as much as rare species. We hope that our results encourage the use of social wasps as models in basic and applied ecological surveys and further efforts for conservation of pristine forest areas in the tropical region of South America.

The Effect of Forest Fragmentation on Polistinae

“…Since it presents a larger area, the fragment F4 has a larger availability of hydric and food resources, in addition to a larger number of nesting sites. The abundance of species from the genus Agelaia in diversity studies is a side effect of a large number of individuals in these colonies (Hunt et al, 2001;Graça & Somavilla, 2018), as noted in other studies carried out in the state of Minas Gerais Souza et al, 2015b).…”

“…This is a consequence of the border effect (Lovejoy et al, 1986), which alters the abiotic and biotic factors (Lovejoy et al, 1986;Wirth et al, 2007); as a result, many species are lost (Woodroffe & Ginsberg, 1998). In the study carried out by Graça and Somavilla (2018) many species were found in both forests, with an emphasis on Agelaia fulvofasciata, Agelaia testacea, Agelaia pallipes, and Polybia rejecta, genera also present in this study. The authors point out that even if the species are present both in the continuous and in the fragmented forest, there was a significant change in the absolute abundance values.…”

“…It was observed that F1 is very similar to F2, including their sizes (Table 1), but they are different from F4, which behaved in a different way, resulting in seven exclusive species -even if F4 is more isolated from the other fragments regarding the other study areas, what can be explained due to the ability of the wasps to adapt to fragmentation better than bees (Morato & Campos, 2000). Notithstanding, according to Graça and Somavilla (2018) in their study in the Amazon rainforest, it was verified that many species have colonized not only continuous forest areas but also fragments; there is however a decrease in the number and abundance of species, which reveals a rupture in the structure of the fragmented community. Thus, the researchers concluded that the forest fragmentation is likely to threaten abundant and rare species equally.…”

“…It is vital to understand how the animal populations behave when confronted with environmental fragmentation in order to establish actions that can minimize the negative effects of this process on the biota; however, there is little to no information on a variety of animals in this context, such as wasps, both the solitary (Morato & Campos, 2000) and the social ones (Graça & Somavilla, 2018).…”

“…Studies that utilized the social wasps as ecological models to evaluate the impact of fragmentation are scarce, however, Graça and Somavilla (2018) have made an important contribution to the Amazon Biome, showing that the continuous vegetation areas are home to an abundance (common and rare), richness and diversity greater than when compared to the fragments highly affected by anthropic actions.…”