Desert spider community

25 p. : ill., maps ; 26 cm.Includes bibliographical references (p. 24-25)."The habitat of desert spiders is characterized, and multivariate analyses are used to assess interspecific relations among spiders inhabiting a Recent lava bed area in south-central New Mexico. General habitat types (i.e., lava bed, mixed grassland, and rangeland) account for most of the variability in species dispersion. The majority of the 90 species present in the area frequented the lava bed; the fewest species occupied the mixed grassland habitat bordering the flow. The spider community can be readily divided into eight groups within which frequent interaction is expected. Five of these groups are distinguished by general habitat association and temporal and seasonal considerations. The remaining groups consist of species that exhibit preferences toward specific habitat features (grasses and shrubs). In most, but not all cases, closely related species are separated by spatial and temporal differences. Factors of the physical environment are thought to allow the coexistence of congeneric Pellenes (Salticidae) and Dictyna (Dictynidae) for which no niche partitioning is apparent. Nine new species are described from the study area: Zorocrates karli, Theridion leviorum, Drassyllus mumai, Zelotes chicano, Zelotes anglo, Phidippus reederi, Phidippus volcanus, Metaphidippus shaferi, and Sitticus juniperi"--P. [1]

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., heterospecific) spider species that commonly exploit multi-female colonies. We (1) determined whether the phenotypic composition of colonies is associated with foreign spider abundance, (2) tested whether heterospecific spider abundance and diversity affect colony survival in the field, and (3) performed staged encounters between groups of A. studiosus and their colony-level predator Agelenopsis emertoni (A. emertoni)to determine whether asocial females exhibit more defensive behavior. We found that larger colonies harbor more foreign spiders, and the number of asocial colony members was negatively associated with foreign spider abundance. Additionally, colony persistence was negatively associated with the abundance and diversity of foreign spiders within colonies. In encounters with a colony-level predator, asocial females were more likely to exhibit escalatory behavior, and this might explain the negative association between the frequency of asocial females and the presence of foreign spider associates. Together, our results indicate that foreign spiders are detrimental to colony survival, and that asocial females play a defensive role in multi-female colonies

Game theory in the ecological context

Riechert SE, Hammerstein P. Game theory in the ecological context. Working Papers. Institute of Mathematical Economics. Vol 120. Bielefeld: Center for Mathematical Economics; 1983

Patterns of Reproductive Success Associated With Social Structure and Microclimate in a Spider System

Species that vary in social structure within and among populations can provide unparalleled insight into the evolution of sociality. The theridiid spider Anelosimus studiosus varies widely in its social structure at the northern edge of its range. Colony sizes range from the solitary/territorial female with her offspring to cooperative colonies of tens to hundreds of adult females. In previous work, we developed an assured fitness returns \u27brood-fostering model\u27 that predicts that in cooler environments mothers in multiple-female colonies will have a selective advantage over solitary female nests. According to the model, at cool sites the rate of juvenile maturation is slowed, increasing the probability that the mother will die before the brood reaches independence. In her absence, other females would foster her brood. We tested this hypothesis by manipulating colony size and by monitoring the reproductive success of naturally occurring solitary and multifemale colonies in cold and warm temperature environments. Our results indicate that while multiple-female colonies have higher fitness at cool sites, the solitary female nests achieve higher fitness at warmer sites. The higher reproductive success of multifemale colonies at cold sites further reflects the total failure of solitary female nests at these sites. Solitary female nests that survived generally had higher reproductive success than multifemale colonies at all temperatures. In natural colonies, fitness was highest for smaller multifemale colonies in the colder environments and decreased in the larger colonies. We use these data to refine the brood-fostering model and discuss the results with regard to the observed polymorphism in social structure

Parameters Affecting the Habitat Choice of a Desert Wolf Spider, Lycosa santrita Chamberlin and Ivie

Volume: 7Start Page: 155End Page: 16

Behavioural Syndromes and Their Fitness Consequences in a Socially Polymorphic Spider, Anelosimus studiosus

The temperate comb-footed spider, Anelosimus studiosus, shows a social behaviour polymorphism: individuals may defend asocial nests against intrusion by conspecifics or cooperate with them in multifemale nests. A suite of behavioural traits, including response to predators and prey, degree of superfluous killing, exploratory behaviour and general level of activity, was examined in laboratory trials to: (1) establish the extent to which these traits are correlated with social phenotype and (2) explore the potential adaptive value of this trait suite to the respective asocial and social phenotypes. Populations from the two latitudes studied, 26° and 36°, showed similar suites of correlated traits or syndromes. The individuals tested generally fell into two groups in the behavioural trials, although the asocial individuals from the mixed-phenotype population at 36° latitude were intermediate with respect to some of the measures. Individuals scored as \u27social\u27 generally showed less aggressive behaviour towards predatory cues, were less responsive to prey encountering their webs, showed little evidence of superfluous killing of prey and showed lower levels of activity than did most individuals scored as \u27asocial\u27. These results suggest linkage or pleiotropy between social behaviour and these traits. The behaviour of individuals in staged, mixed-phenotype feeding pairs indicated that social individuals may suffer fitness consequences in polymorphic populations. These results are discussed with respect to the stability and dynamics of the respective phenotypes in polymorphic populations

In the spider nursery: indifference, cooperation or antagonism?

Volume: 45Start Page: 283End Page: 28