T. Crouch et Y. Lubin, Population stability and extinction in a social spider Stegodyphus mimosarum (Araneae : Eresidae), BIOL J LINN, 72(3), 2001, pp. 409-417
Nests of social spiders in their natural habitat are clustered and colony c
lusters may be short-lived. Rapid growth and subsequent extinction of colon
ies and colony clusters are predicted for social spider populations; howeve
r, little quantitative data exist on the longevity of colonies. Furthermore
, processes that influence the growth and decline of social spider populati
ons are poorly understood. In this study we followed a population of over 5
50 nests of S. mimosarum from September 1994 to December 1999 and analysed
the changes in relation to abiotic (temperature and rainfall) and biotic (p
arasitism) factors. We observed two years of apparent population stability
(1994-1995), during which nest numbers remained high and constant. This was
followed in 1996 by a c. 12% decrease in the numbers of active nests. At t
he end of 1996 there was a mass dispersal event which was followed in 1997
by a steady decline of the population with no further recovery. Thus, the d
ecline was preceded by dispersal and nest failure, indicating that conditio
ns in the population were unfavourable. The population-wide synchrony of th
ese events reflects the seasonally synchronized development in S. mimosarum
. However, extrinsic factors related to climate did not explain the extreme
events of dispersal and population decline. The potential importance of pa
rasitism, on the one hand, and unknown intrinsic factors on the other, shou
ld be considered as alternative explanations that remain to be tested.(C) 2
001 The Linnean Society of London.