Validating dispersal distances inferred from autoregressive occupancy models with genetic parentage assignments

Abstract

Dispersal distances are commonly inferred from occupancy data but have rarely been validated. Estimating dispersal from occupancy data is further complicated by imperfect detection and the presence of unsurveyed patches. We compared dispersal distances inferred from seven years of occupancy data for 212 wetlands in a metapopulation of the secretive and threatened California black rail (Laterallus jamaicensis coturniculus) to distances between parent-offspring dyads identified with 16 microsatellites. We used a novel autoregressive multi-season occupancy model that accounted for both unsurveyed patches and imperfect detection to quantify patch isolation using buffer radius (BRM) and incidence function (IFM) connectivity measures at 15 scales (1-10, 15, 20, 25, and 30km). Connectivity measures were then fit as colonization covariates in occupancy models to estimate a model-averaged dispersal distance. As predicted, colonization was more strongly related to connectivity at small spatial scales (<10km). AIC weights were greatest at 7km for BRM and at 4km for IFM. Model-averaged dispersal distances (BRM=7.46km; IFM=5.48km) showed good agreement with the mean M(±SE) dispersal distance from 23 parent-offspring dyads (5.58±1.92km), indicating reasonably accurate mean dispersal distances can be inferred from occupancy data when isolation strongly affects colonization.