Intertidal colonization rates. A matched latitude, north v. south, remote v. near shore island experiment

Abstract

Colonization of artificial substrata was monitored on sheltered rocky shores at Husvik, South Georgia (54° 11′S; 36° 40′W) and Cumbrae, Scotland (55° 46′N; 4° 55′W) from mid summer to early autumn. South Georgia is a remote island (1,330km from other land); Cumbrae is only 2km from nearby coasts. Both islands were heavily glaciated for a period up to about 10,000ybp, so the intertidal fauna is of geologically recent origin. The South Georgian fauna is depauperate and consists mainly of direct developers; that of Cumbrae is rich and largely larviparous. Colonization rates at Cumbrae were one to four orders of magnitude greater than at Husvik. It is suggested that the fauna of South Georgian shores stems from colonization by rafting from remote sources, while Cumbrae has been supplied predominantly by short-range pelagic larval dispersal. The measured differences in colonization rates reflect the substantial local advantage of larval dispersal over direct development in established communities. © 1998 Blackwell Science Ltd.