Cooperative breeding and long-distance dispersal: a test using vagrant records

Abstract

Cooperative breeding is generally associated with increased philopatry and sedentariness, presumably because short-distance dispersal facilitates the maintenance of kin groups. There are, however, few data on long-distance dispersal in cooperative breeders-the variable likely to be important for genetic diversification and speciation. We tested the hypothesis that cooperative breeders are less likely to engage in long-distance dispersal events by comparing records of vagrants outside their normal geographic range for matched pairs (cooperatively vs. non-cooperatively breeding) of North American species of birds. Results failed to support the hypothesis of reduced long-distance dispersal among cooperative breeders. Thus, our results counter the conclusion that the lower rate of speciation among cooperative breeding taxa found in recent analyses is a consequence of reduced vagility.

Figure 1. Species maps and vagrant records.

Maps are presented in their original datum, North American 1983. The base map is provided by the National Geospatial-Intelligence Agency .

Figure 2. Map projections and buffer calculations, using the Bushtit (Psaltriparus minimus) range as an example.

(a) North American 1983 is the original datum for the ranges and vagrant points. (b) Each range was reprojected to a customized Albers Equal Area projection for the purpose of calculating the centroid of the range. (c) Each range and set of vagrant points were reprojected to a customized Azimuthal Equidistant projection with the point of tangency at the centroid of the range. In this projection, the distances from the edge of the range to each vagrant point were measured. (d) A buffer at the distance from the edge of the range to the farthest vagrant was drawn around the range. The density of vagrants within the buffer was used to calculate an index to measure vagrant frequency. The base map is provided by the National Geospatial-Intelligence Agency .