Figure 1.

A) Map of the sampled shore area. Habitat points in the boulder field are shown in black, and points on bedrock in grey. Each sampled snail is represented by a yellow point, and the one‐dimensional path through the sampled area is indicated in orange. There are two main habitat transitions: arrow 1, from the boulder field to the rock platform; and arrow 2, from the rock platform to the steep cliff. The orange arrow indicates the average center of all non‐neutral clines (see Fig. 4). Note that the two large sampling gaps in the “Crab” and the “Wave” area represent intentional breaks in the sampling, while the small gap coinciding with the average cline center (orange arrow) represents a gap in the snail distribution. Insert: satellite image from Google Earth (Image © 2017 DigitalGlobe). B) Examples of phenotypic and genetic clines. The x‐axis represents the path through the sampled transect shown in (A). Vertical lines indicate the positions of the arrows in (A). The top panel shows five different phenotypic clines. Thick lines represent frequencies of different colors/patterns (beige, black, and banded); thin lines represent size and shape (scaled to vary between 0 and 1. Note that for analyses, scaling was done so that it ensured an increase from Crab to Wave. In this figure the size cline is reverted to show that the Crab ecotype is larger). The second panel shows examples of genetic clines, with grey curves representing clines consistent with neutrality and orange curves representing non‐neutral clines.