Figure
1. (A) Sites surveyed (circles) and sampled (stars) in the UK and
Ireland for the intertidal marine invertebrates Nucella lapillusand Steromphala umbilicalis . Sites are coloured according to the
presence or absence of one or both species (black = both species
present; grey = only N. lapillus present; white = both species
absent). Identified habitat “gaps” are indicated with black lines and
labelled in capitals. Water bodies are labelled in italics. (B) Release
locations of the gastropod Steromphala umbilicalis , in the larval
dispersal model, showing sample sites (labelled, red-yellow points) and
interim stepping-stones sites (blue points). The size and colour of
sample site markers indicate the degree of convergence (i.e., net sink
sites are large and yellow) or divergence (i.e., net source sites are
small and dark red) for one season of dispersal (June-September). The
“100%” legend in the bottom left corner indicates the size of a site
marker that had no net gain or loss of particles at the end of a
spawning season. The black arrows indicate the sample sites which are
connected (no year-on-year spread shown, background connectivity only).
Online version in colour.