Iterative evolution of increased behavioral variation characterizes the transition to sociality in spiders and proves advantageous.

The evolution of group living is regarded as a major evolutionary transition and is commonly met with correlated shifts in ancillary characters. We tested for associations between social tendency and a myriad of abiotic variables (e.g.

Within-group behavioral variation promotes biased task performance and the emergence of a defensive caste in a social spider.

The social spider Anelosimus studiosus exhibits a behavioral polymorphism where colony members express either a passive, tolerant behavioral tendency (social) or an aggressive, intolerant behavioral tendency (asocial). Here we test whether asocial individuals act as colony defenders by deflecting the suite of foreign (i.e.

How within-group behavioural variation and task efficiency enhance fitness in a social group.

How task specialization, individual task performance and within-group behavioural variation affects fitness is a longstanding and unresolved problem in our understanding of animal societies. In the temperate social spider, Anelosimus studiosus, colony members exhibit a behavioural polymorphism; females either exhibit an aggressive 'asocial' or docile 'social' phenotype. We assessed individual prey-capture success for both phenotypes, and the role of phenotypic composition on group-level prey-capture success for three prey size classes.

Population differences in behaviour are explained by shared within-population trait correlations.

Correlations in behavioural traits across time, situation and ecological context (i.e. 'behavioural syndromes' or 'personality') have been documented for a variety of behaviours, and in diverse taxa.

Relatedness and genetic structure in a socially polymorphic population of the spider Anelosimus studiosus.

The evolution of sociality remains a challenge in evolutionary biology and a central question is whether association between kin is a critical factor favouring the evolution of cooperation. This study examines genetic structure of Anelosimus studiosus, a spider exhibiting polymorphic social behaviour. Two phenotypes have been identified: an 'asocial' phenotype with solitary female nests and a 'social' phenotype with multi-female/communal nests.

Frequency-dependent success of cheaters during foraging bouts might limit their spread within colonies of a socially polymorphic spider.

Although several studies have demonstrated that frequency-dependent effects can promote the maintenance of cooperative behavior in microbes, experimental evidence of frequency-dependent effects in cooperative animal societies is rare. We staged mixed phenotype feeding bouts in the spider Anelosimus studiosus, which shows a within-population social polymorphism, to determine how phenotype frequency affects the foraging success of the social (cooperative) and asocial (cheater) phenotypes. Foraging performance was inferred from average change in percent mass for the respective phenotypes after staged group foraging events.

Speciation history of the North American funnel web spiders, Agelenopsis (Araneae: Agelenidae): phylogenetic inferences at the population-species interface.

Intra- and interspecific relationships of 12 out of 13 described species as well as a potential new species in the spider genus Agelenopsis (Araneae: Agelenidae) were analyzed using sequence data from two mitochondrial genes, cytochrome oxidase I (COI) and 16S ribosomal RNA. Approximately half of the species examined formed well-supported monophyletic groups, whereas the rest of the species were part of well-supported monophyletic species groups. Rather than viewing cases where species were not identified as being monophyletic as poor taxonomy, these cases more likely represent recent speciation and offer insights into the process of speciation.

Molecular evidence for Pleistocene glacial cycles driving diversification of a North American desert spider, Agelenopsis aperta.

The influence of historical climatic vs. geological changes on species diversification patterns was investigated in a widely distributed North American desert spider, Agelenopsis aperta (Araneae: Agelenidae), with particular reference to Pleistocene glacial cycles and earlier patterns of mountain building. Levels of sequence divergence obtained from the mitochondrial gene, cytochrome oxidase I, dated to the Pleistocene, eliminating Rocky Mountain orogeny as a cause of diversification, as orogeny ended 4 million years ago.

Genetically-based variation between two spider populations in foraging behavior.

Optimal foraging theory is based on the assumption that at least some aspects of foraging behavior are genetically determined (Pyke et al. 1977; Kamil and Sargent 1980; Pyke 1984). Nonetheless, very few studies have examined the role of genetics in foraging behavior.

DISPERSAL AND POPULATION-GENETIC STRUCTURE OF THE COOPERATIVE SPIDER, AGELENA CONSOCIATA, IN WEST AFRICAN RAINFOREST.

Dispersal experiments and gel electrophoresis of allozyme polymorphisms were used to investigate the selective mode underlying cooperative behavior in the rainforest spider, Agelena consociata. Previous work has indicated that individual selection alone does not explain the cooperative and even altruistic behavior noted for this African species, which exists in groups of up to hundreds of adults. We found no evidence for active dispersal by reproductives or any age class of this spider.