Seasonal dynamics in a cavity-nesting bee-wasp community: Shifts in composition, functional diversity and host-parasitoid network structure

Abstract

Ecological communities are composed of species that interact with each other forming complex interaction networks. Although interaction networks have been usually treated as static entities, interactions show high levels of temporal variation, mainly due to temporal species turnover. Changes in taxonomic composition are likely to bring about changes in functional trait composition. Because functional traits influence the likelihood that two species interact, temporal changes in functional composition and structure may ultimately affect interaction network structure. Here, we study the seasonality (spring vs. summer) in a community of cavity-nesting solitary bees and wasps (‘hosts’) and their nest associates (‘parasitoids’). We analyze seasonal changes in taxonomic compostion and structure, as well as in functional traits, of the host and parasitoid communities. We also analyze whether these changes result in changes in percent parasitism and interaction network structure. Our host and parasitoid communities are strongly seasonal. Host species richness increases from spring to summer. This results in important seasonal changes in functional composition of the host community. The spring community (almost exclusively composed of bees) is characterized by large, univoltine, adult-wintering host species. The summer community (composed of both bees and wasps) is dominated by smaller, bivoltine, prepupa-wintering species. Host functional diversity is higher in summer than in spring. Importantly, these functional changes are not only explained by the addition of wasp species in summer. Functional changes in the parasitoid community are much less pronounced, probably due to the lower parasitoid species turnover. Despite these important taxonomic and functional changes, levels of parasitism did not change across seasons. Two network metrics (generality and interaction evenness) increased from spring to summer. These changes can be explained by the seasonal increase in species richness (and therefore network size). The seasonal shift from a bee-dominated community in spring to a wasp-dominated community in summer suggests a change in ecosystem function, with emphasis on pollination in spring to emphasis on predation in summer.

Seasonal variation in the ecology of tropical cavity-nesting Hymenoptera on Mt. Kilimanjaro

“…In line with hypothesis 3, the magnitude of seasonality in nest-building activity differed between functional groups, but in contrast to our assumption, it was synchronised in the colline zone with a strong peak at the end of the short rainy season for bees, caterpillar-and spiderhunting wasps. Seasonal patterns are believed to differ between species, families or other taxonomic groups (Wolda and Roubik 1986, Sirohi et al 2015, Osorio-Canadas et al 2018, but except for small differences, we rather found differences in magnitude than in seasonal timing of activity. A similar tendency was found in a leaf-roller community and herbivores seemed to fluctuate higher with seasonality than the predators (Vieira and Romero 2013).…”

“…Seasonal changes in population size and species composition are presumably also reflected in the life-history traits of insect communities (Samnegård et al 2015, Osorio-Canadas et al 2018. For example, there are seasonal changes in the body size of bee communities (Osorio-Canadas et al 2016).…”

Relative species abundance successfully predicts nestedness and interaction frequency of monthly pollination networks in an alpine meadow

“…Stress values below 0.2 indicated that the ordination adequately represented the data [32]. A measure of goodness of fit based on the Bray-Curtis dissimilarity index and distance in graphical representation was selected to evaluate the NMDS results, where the smaller the circle, the better goodness of fit [33].…”

Reviewing the use of bee trap nests for the study of interaction networks in agroecosystems: insights from its use in olive farms

“…Son bastantes y variadas las aportaciones que las redes han hecho a la ecología de estos grupos. Por ejemplo, Osorio-Canadas et al (2018), estudiaron las dinámicas estacionales en la composición y las redes antagonistas huéspedes-parasitoides en nidales artificiales y descubrieron que el servicio de polinización se veía maximizado en primavera mientras que el de depredación lo hacía en verano. En otro interesante artículo, Morris et al (2015) demostraron que las redes huésped-parasitoides pueden variar a lo largo del gradiente altitudinal en sistemas naturales.…”