Limited adaptive life-history plasticity in a semelparous spider, Stegodyphus lineatus (Eresidae)

Strictly semelparous animals may still benefit from retaining a plastic reproductive strategy. In cases where the current, usually single brood is too small to deplete maternal resources, females could increase their fitness through investing in another clutch. This may not always be possible if females are constrained and cannot switch between different reproductive performances, such as feeding of young and egg development. We investigated the existence of plasticity in the semelparous spider Stegodyphus lineatus by drastically reducing brood sizes at different stages of the reproductive cycle. We asked whether: (1) females will be able to produce another clutch while caring for young; (2) production of another clutch is a function of female resources; (3) small broods will be able to benefit from increased female resources. Few females re-laid and those few all had their broods experimentally reduced shortly after hatching. We could not detect a difference in life-history variables between females that re-laid and those that did not. However, producing a new clutch did not prevent females from feeding the remaining offspring from the first brood. Matriphagy occurred only in broods that were reduced shortly before the young normally consume the mother. The timing of the mother's death was a function of the resources the female had left after brood reduction, namely her body mass. Thus, the spiders are generally plastic in that they possess the potential to invest in a second brood. However, in our experiment, this occurred less often than expected. Either incomplete brood reduction occurs too infrequently to act as a selection pressure for an iteroparous strategy or our reduction was not drastic enough to achieve the expected result.