Abstract
Dispersal ability is key to species persistence in times of environmental change. Assessing a species' vulnerability and response to anthropogenic changes is often performed using one of two methods: correlative approaches that infer dispersal potential based on traits, such as wingspan or an index of mobility derived from expert opinion, or a mechanistic modeling approach that extrapolates displacement rates from empirical data on short‐term movements.Here, we compare and evaluate the success of the correlative and mechanistic approaches using a mechanistic random‐walk model of butterfly movement that incorporates relationships between wingspan and sex‐specific movement behaviors.The model was parameterized with new data collected on four species of butterfly in the south of England, and we observe how wingspan relates to flight speeds, turning angles, flight durations, and displacement rates.We show that flight speeds and turning angles correlate with wingspan but that to achieve good prediction of displacement even over 10 min the model must also include details of sex‐ and species‐specific movement behaviors.We discuss what factors are likely to differentially motivate the sexes and how these could be included in mechanistic models of dispersal to improve their use in ecological forecasting.
Highlights
Dispersal is a feature of animal behavior that crucially affects ecological processes across a range of spatial and temporal scales, including the persistence of species in fragmented landscapes, community dynamics, and evolutionary trajectories (Hanski, 1998; Nathan et al, 2008)
The model was parameterized with new data collected on four species of butterfly in the south of England, and we observe how wingspan relates to flight speeds, turning angles, flight durations, and displacement rates
We present a random-walk model of butterfly movement behavior that incorporates relationships between wingspan and the key aspects of the movement process, including flight speed, turning angle, and the proportion of time spent flying
Summary
Dispersal is a feature of animal behavior that crucially affects ecological processes across a range of spatial and temporal scales, including the persistence of species in fragmented landscapes, community dynamics, and evolutionary trajectories (Hanski, 1998; Nathan et al, 2008). Given the challenges of developing these more complex mechanistic models, the pragmatic approach to applied questions concerning dispersal potential has often been to use a proxy of mobility, one that is either based on expert knowledge (Burke, Fitzsimmons, & Kerr, 2011; Shreeve, 1995) or correlated with another trait, such as body size (Bejan, 2000; Berwaerts, Van Dyck, & Aerts, 2002; Dudley & Srygley, 1994; Peters, 1986; Sekar, 2012) This approach, here termed the “correlative approach,” is valid at broad scales: search rates for foragers in two dimensions, for example, increase allometrically with body mass according to a power law with exponent 0.68 (Pawar, Dell, & Savage, 2012), and home range sizes increasing with exponent 1 for mammals (Jetz, Carbone, Fulford, & Brown, 2004). The predictive success of the mechanistic approach is found to be strongly influenced by the inclusion of sex-specific behavior, and we detail why the correlative approach is less successful
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