Bergmanns's size cline in New Zealand marine spray zone spiders (Araneae: Anyphaenidae: Amaurobioides)

Abstract

Members of the spider genus Amaurobioides are restricted to the spray zone of rocky marine coasts, where they construct and hunt from silk retreats. Collecting for this study shows these spiders to be distributed around the entire New Zealand coast. A Templeton, Crandall, and Sing (TCS) analysis of the ND1 mitochondrial gene places specimens from the North Island and the northern half of the South Island into a group distinct from Amaurobioides maritima O.P.-Cambridge, 1883, which is restricted to the southern half of the South Island. Females of this northern group exhibit latitude- and temperature-related clines in body length, body mass, and residual index of condition, with larger individuals with greater indices of condition being found at cooler, southern sites. This size cline also appeared in a broader geographical analysis that included Amaurobioides piscator Hogg, 1909 from the sub-Antarctic Auckland and Campbell Islands. Thirteen ND1 haplotypes are represented in the northern group. Both independent contrast analyses and standard regressions of the mean body lengths and mean masses of these haplotypes, and the mean latitudes and temperatures of the sites where haplotypes were present, document a Bergmann's size cline, and provide evidence for an underlying genetic component. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 78–92.