DOES HIGH ADULT MORTALITY EXPLAIN SEMELPARITY IN THE SPIDER STEGODYPHUS-LINEATUS (ERESIDAE)

In life history theory, low adult survival is considered to favour the evolution of semelparity. Low adult survival could result from intrin sically high costs of reproduction or from high mortality due to extri nsic causes such as predation. In a held experiment, we removed female s of the spider Stegodyphus lineatus from their young and induced a se cond breeding event to test these hypotheses. These semelparous spider s normally die after producing a single clutch, while the young are st ill in the nest. However, females that lose their brood will produce a second clutch. Experimental females that were protected from predatio n were capable of laying a second clutch and raising the young of two clutches. During the same time, the survival of unprotected females in the field was extremely low due to predation. When females were remov ed experimentally, growth and survival of first broods were reduced. N one the less, a model revealed that only a small increment in adult su rvival would favour a second breeding attempt. We conclude that high p redation pressure resulting in low adult survival selects for a single reproductive event in these spiders.