J. Johannesen et al., THE SIGNIFICANCE OF RELATEDNESS AND GENE FLOW ON POPULATION GENETIC-STRUCTURE IN THE SUBSOCIAL SPIDER ERESUS-CINNABERINUS (ARANEAE, ERESIDAE), Biological Journal of the Linnean Society, 63(1), 1998, pp. 81-98
Interdemic selection, inbreeding and highly structured populations hav
e been invoked to explain the evolution of cooperative social behaviou
r in the otherwise solitary and cannibalistic spiders. The family Eres
idae consists of species ranging from solitary and intermediate subsoc
ial to species exhibiting fully cooperative social behaviour. In this
study we, in a hierarchical analysis, investigated relatedness of puta
tive family clusters, inbreeding and population genetic structure of t
he subsocial spider Eresus cinnaberinus. Five hierarchical levels of i
nvestigation ranging from large scale genetic structure (distances of
250 and 50 km level 1 and 2) over microgeographic structure (20 km(2)
and 4 km(2), level 3 and 4) to a single hill transect of 200 m (level
5) were performed. The purpose of level 5 was two-fold: (1) to investi
gate the relatedness of putative family groups, and (2) to evaluate th
e influence of both family living and sampling design on higher level
estimates. Relatedness estimates of putative family groups showed an a
verage relatedness of R=0.26. There was no indication of inbreeding. I
n contrast to social spiders, genetic variation was abundant, H-e appr
oximate to 0.10. The population genetic structure was intermediate bet
ween social and asocial spiders. Genetic variance increased continuall
y across hierarchical levels. Family structured neighbourhoods biased
differentiation estimates among level 5 samples (F-ST=0.04) and level
3 and 4 samples (0.07<F-ST<0.18), and apparent inbreeding among level
3 and 4 samples, F-IS>0, was caused by disjunct sampling from separate
neighbourhoods. Larger scale samples were highly differentiated 0.12<
F-ST<0.26, depending on level and sampling design. Due to a distance e
ffect family living did not influence estimates of the higher level 1.
Although the dispersing sex among social spiders and the subsocial E.
cinnebarinus differ, females versus males, female behaviour of both s
ociality classes lead to high genetic variance. (C) 1998 The Linnean S
ociety of London.