In a fragmented landscape, we can model a species’ population as a set of many smaller populations occupying scattered, suitable habitat. Even if persistence in any one habitat patch is low, being connected to many other patches allows for dispersing individuals to recolonize habitat patches and create a viable metapopulation. In the simplest case, the number of patches supporting a population at any time depends on the arrangement and size of habitat patches on the landscape. In more complex cases, we must manage many species which respond to the same landscape in different ways. In a new paper, Fernández-Chacón and colleagues analyze how 73 butterfly species have responded to a fragmented landscape and yearly climate variation over 17 years. Their approach focuses on how species differ in their metapopulation dynamics, like rates of extinction and colonization, which would be important for developing conservation strategy.
For each species, Fernández-Chacón and colleagues model how environmental factors affect metapopulation dynamics using occupancy models. These environmental factors include the landscape surrounding the habitat patch; suitable area and topography of a habitat patch; and yearly variation in rainfall and temperature in the arid biome. Across all species, they generalize how two key traits, dispersal ability and specialist habitat use, alter how species respond to the environment. Colonization rate was higher in butterflies with better dispersal and generalist habitat use. Greater landscape permeability, a measure of how easily a butterfly moves through an arrangement of different fragmented land uses, typically increased colonization rate. Extinction rate depended on the local area of suitable habitat more than the surrounding landscape permeability. One surprise was the small impact of climate variation on the metapopulation dynamics compared to the landscape and habitat factors, possibly due to the mountainous landscape providing many microclimates. Another surprise was that species across the range of dispersal abilities and specialized habitat use responded to environmental factors similarly (with small differences discussed in the paper). The authors suggest that managing for both habitat suitability within protected areas and landscape permeability for animal movement between patches would ensure a diverse butterfly community in this region.
Fernández-Chacón, A., C. Stefanescu, M. Genovart, J. D. Nichols, J. E. Hines, F. Páramo, M. Turco, and D. Oro. 2014. Determinants of extinction-colonization dynamics in Mediterranean butterflies: the role of landscape, climate and local habitat features. Journal of Animal Ecology, 83: 276–285.