Dispersal Depression With Habitat Fragmentation in the Bog Fritillary Butterfly

Abstract

Habitat fragmentation is expected to impose strong selective pressures on dispersal rates. However, evolutionary responses of dispersal are not self-evident, since various selection pressures act in opposite directions. Here we disentangled the components of dispersal behavior in a metapopulation context using the Virtual Migration model, and we linked their variation to habitat fragmentation in the specialist butterfly Proclossiana eunomia. Our study provided a nearly unique opportunity to study how habitat fragmentation modifies dispersal at the landscape scale, as opposed to microlandscapes or simulation studies. Indeed, we studied the same species in four landscapes with various habitat fragmentation levels, in which large amounts of field data were collected and analyzed using similar methodologies. We showed the existence of quantitative variations in dispersal behavior correlated with increased fragmentation. Dispersal propensity from habitat patches (for a given patch size), and mortality during dispersal (for a given patch connectivity) were lower in more fragmented landscapes. We suggest that these were the consequences of two different evolutionary responses of dispersal behavior at the individual level: (1) when fragmentation increased, the reluctance of individuals to cross habitat patch boundaries also increased; (2) when individuals dispersed, they flew straighter in the matrix, which is the best strategy to improve dispersal success. Such evolutionary responses could generate complex nonlinear patterns of dispersal changes at the metapopulation level according to habitat fragmentation. Due to the small size and increased isolation of habitat patches in fragmented landscapes, overall emigration rate and mortality during dispersal remained high. As a consequence, successful dispersal at the metapopulation scale remained limited. Therefore, to what extent the selection of individuals with a lower dispersal propensity and a higher survival during dispersal is able to limit detrimental effects of habitat fragmentation on dispersal success is unknown, and any conclusion that metapopulations would compensate for them is flawed.

Railway tracks can have great value for butterflies as a new alternative habitat

“…Attention is usually focused on the conservation of target or rare species with specific requirements (e.g. Schtickzelle et al 2006;Bąkowski et al 2010;Wynhoff et al 2011;Kalarus et al 2013); nevertheless, other common and widespread species also are in decline (Van Dyck et al 2009). Thus, the conservation of multispecies communities has become problematic and particularly challenging (Settele et al 2009).…”

Demography of adults of the Marsh fritillary butterfly, Euphydryas aurinia (Lepidoptera: Nymphalidae) in the Czech Republic: Patterns across sites and seasons

“…This approach is widely used in butterfly ecology, but despite its venerable tradition (e.g., Ehrlich et al, 1975;Ehrlich & Hanski, 2004) few studies have been done over many seasons using flexible modern approaches (e.g., Fleishman et al, 2002;Schtickzelle et al, 2006), and none on E. aurinia has included many seasons/sites. In other species, such comparisons demonstrate that colonies within metapopulations display considerable variation in internal dynamics (Boggs, 1987;Schtickzelle et al, 2002), as predicted by metapopulation theory (Hanski, 1999); and that short-term data underestimate the magnitude of population changes (Thomas et al, 2002;Hellmann et al, 2003).…”

Coupling movement and landscape ecology for animal conservation in production landscapes

“…Individuals of better body condition or larger size typically have greater motion capacity [55]. Consequently, reductions in habitat quality in modified landscapes can decrease fitness and motion capacity, resulting in delayed or depressed dispersal [56][57][58]. Such impacts at the individual level can also translate into selective pressures at the population level because morphological traits related to movement have heritable components [59].…”