Do developmental mode and dispersal shape abundance–occupancy relationships in marine macroinvertebrates?
A. Foggo, Marine Biology and Ecology Research Centre, School of Biological Sciences, Davy 617, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK. Tel.: +44 1752232914. Fax: +44 1752232970. E-mail: AFoggo@Plymouth.ac.uk
- 1Dispersal is a crucial process in maintaining population structures in many organisms, and is hypothesized as a process underlying the interspecific relationship between abundance and distribution. Here we examined whether there was a link between the dispersal and developmental modes of marine macroinvertebrates and the slopes and elevations of interspecific abundance–occupancy relationships. We predicted that if within-site retention of larvae ranks in the order brooders > lecithotrophs > planktotrophs, for any given level of mean abundance, occupancy should increase in the order brooders < lecithotrophs < planktotrophs. We also predicted that propensity to form metapopulations should be greater for planktonic dispersers (i.e. lecithotrophs and planktotrophs combined) than for non-planktonic (i.e. brooders), resulting in steeper abundance–occupancy relationships for the former.
- 2Predictions were tested using a data set for 362 subtidal marine macroinvertebrates occurring across 446 1-km2 grid squares around the British Isles; analyses were performed on the data set as a whole and for separate phyla.
- 3The total data set had a Z-transformed effect size of 0·79, within the confidence intervals described by Blackburn et al. (2006; Journal of Animal Ecology, 75, 1426–1439), and was consistently present with relatively homogeneous effect size in separate analyses of polychaetes, crustaceans, molluscs and echinoderms.
- 4In all cases, planktonic dispersing organisms showed an abundance–occupancy relationship with greater elevation than that for non-planktonic organisms; in polychaetes the elevation of slopes was in the rank order planktotrophs > lecithotrophs > brooders. No differences between the slopes of the abundance–occupancy relationship were apparent for different dispersal modes either within, or across phyla.
- 5We conclude that dispersal capacity may play an important part in determining the elevation of the abundance–occupancy relationship, the corollary of low dispersal in the marine realm being greater local retention of larvae and greater local population abundance at low extents of geographical distribution.