Ranking the ecological causes of dispersal in a butterfly

Abstract

Dispersal, i.e. movements potentially leading to gene flow, is central in evolutionary ecology. Many factors can trigger dispersal, all linked to the social and/or the environmental context. Moreover, it is now widely demonstrated that phenotypes with contrasted dispersal abilities coexist within populations of a same species. The current challenge is to elucidate how social and environmental factors will influence the dispersal decision of individuals with distinct phenotypes. We have used the Metatron, a unique experimental mesocosm dedicated to the study of dispersal within fragmented landscapes, to analyze the relative and interactive roles played by ten potential dispersal triggers in experimental two‐patch metapopulations of butterflies. We demonstrate in our model species that some factors (flight performance and wing length) have direct effects on emigration decision, others act only through interactive effects (sex ratio), while a third class of factors presents both direct and interactive effects (weather conditions, habitat quality and sex). We also show that disperser and resident individuals have distinct behavioral and morphological attributes, revealing the existence of a dispersal syndrome. Finally, our results also suggest that the environmental context, and especially weather conditions and habitat quality, prevails over social factors and individual phenotypes in butterflies' decision to disperse. Our approach is applicable to many species facing medium to strong environmental fluctuations, and constitutes a new way to master the idiosyncrasy of the dispersal process. Our framework should also help prioritize the factors responsible for populations' spatial distribution, which is obviously crucial in the current era of global changes.

Weather explains high annual variation in butterfly dispersal

“…In agreement with our results, a number of various observations from short-term studies on butterfly movement and dispersal have suggested that weather may indeed drive dispersal rates (e.g. [22,27,29,30,42,43]). …”

Sexual differences rather than flight performance underlie movement and exploration in a tropical butterfly

“…External factors include habitat quality and abiotic conditions such as temperature (Legrand et al, 2015;Kuussaari et al, 2016). External factors include habitat quality and abiotic conditions such as temperature (Legrand et al, 2015;Kuussaari et al, 2016).…”

Selecting for invasive tendencies: the evolution of morphological, physiological, and movement behaviour traits associated with dispersal

“…Recently, the large white butterfly (Pieris brassicae) has been used to explore the drivers of dispersal (Legrand et al 2015). This species exhibits a dispersal syndrome where dispersers and residents differ phenotypically.…”

“…This behaviour, which is likely heritable, would thus increase the efficiency of movement between patches and reduce the time-and risk-associated costs of dispersal Larranaga et al 2013). Dispersers are therefore not a random fraction of the population, but are rather individuals with covarying morphological and behavioural traits that describe variation in dispersal in P. brassicae (Legrand et al 2015).…”

“…Artificial selection experiments that select for walking or flight dispersal could be valuable to compare with the phenotypic response of selection for climbing dispersal. Recently, large-scale experimental patch-based landscapes have been implemented to study flight dispersal in butterflies and other species, to provide a measure of dispersal more directly comparable with that of natural systems Bestion et al 2015;Legrand et al 2015). This type of experimental landscape could be useful to study the natural movement of species that use multiple modes of locomotion to disperse.…”