The effects of seasonally variable dragonfly predation on butterfly assemblages

Abstract

Where predation is seasonally variable, the potential impact of a predator on individual prey species will critically depend on phenological synchrony of the predator with the prey. Here we explored the effects of seasonally variable predation in multispecies assemblages of short-lived prey. The study was conducted in a landscape in which we had previously demonstrated generally high, but spatially and seasonally variable dragonfly-induced mortality in adult butterflies. In this system, we show that patterns of patch occupancy in butterfly species flying during periods of peak dragonfly abundance are more strongly associated with spatial variation in dragonfly abundance than patch occupancy of species flying when dragonfly density was low. We provide evidence indicating that this differential sensitivity of different butterfly species to between-habitat differences in dragonfly abundance is causally tied to seasonal variation in the intensity of dragonfly predation. The effect of dragonfly predation could also be measured at the level of whole local butterfly assemblages. With dragonfly density increasing, butterfly species richness decreased, and butterfly species composition tended to show a shift toward a greater proportion of species flying during periods of off-peak dragonfly abundance.

Racing through life: maturation rate plasticity regulates overcompensation and increases persistence

“…Such conditions typically arise when predator densities vary in response to fluctuating environmental conditions. Examples of this include anoxia-driven mortality of predatory fish (Rao et al 2014) and inter-seasonal variability in local predator abundance due to migration or patch extinctions (Tiitsaar et al 2013). Survival variability in such situations highlights the need for a better understanding of the drivers and extent of maturation plasticity in managed populations.…”

Habitat‐related differences in the adult longevity of two ecotypes of a specialized butterfly

“…Apart from the potentially lower availability of nectar sources and nutritional values of larval food plants, shorter adult life span in the bog population could be also related to the pressure of predators, for example dragonflies, which were much more frequently observed in the raised bog habitat during our field study and are regarded as important factors affecting habitat quality for butterflies (Sang & Teder, ; Tiitsaar, Kaasik & Teder, ). Besides, the investigated populations could also be affected by specific larval parasitoids detected in some B. eunomia populations (Choutt et al ., ).…”

Host associations of Coenonympha hero (Lepidoptera: Nymphalidae) in northern Europe: microhabitat rather than plant species

“…The search for plants potentially associated with the presence of C. hero relied on comparison of the points in which a butterfly had been observed (presence points, hereafter), with control points selected within the same habitat patch (=site, hereafter; area 4-18 ha; Sang et al 2010;Tiitsaar et al 2013). In the resulting microhabitat use model, predictor variables included abundances of particular plant species: both those considered as potential hosts, as well as those indicative of abiotic parameters of the site, the latter primarily functioning as covariates in the analyses of potential host plant associations.…”

“…None of the sites occupied by C. hero were currently being managed although our preselection sample (i.e. patches of 'butterfly habitat' being surveyed by the authors: Sang et al 2010;Tiitsaar et al 2013; unpublished data) included both grazed (16 sites, with C. hero being absent from all of those) and unmanaged grasslands (45 sites). For the present study, we selected all these six sites in which C. hero was known to occur in 2007 or 2008, and was found again in both 2012 and 2013.…”