Variation in life history and behavioral traits in the colonial spider Parawixia bistriata (Araneidae): Some adaptive responses to different environments

Widely distributed species are expected to present geographic variation in phenotypic traits (e.g., behavioral, physiological, anatomical) in order to better adapt to the variable condition they encounter. Parawixia bistriata (Araneidae) is a colonial spider distributed in different habitats in South America. Contrary to most social species found in tropical wet forests, P. bistriata's distribution expands from tropical to temperate latitudes. It also exhibits facultative group foraging, a behavioral pattern absent in territorial colonial spiders. In this dissertation, I examined the existence of geographic variation in life history and behavioral traits of P. bistriata's populations inhabiting sites with distinctive environmental conditions and estimated success of populations. I performed reciprocal transplants of colonies to evaluate the influence of genetic and environmental forces on the variation exhibited in both life history and behavioral traits in populations from different habitats. When examining behavioral traits, I focused on foraging behavior as I was interested to evaluate if the expression of this behavioral pattern could explain the success of populations in diverse habitats. Phenology of populations from the different habitats differed. The differences exhibited was a response of juvenile developmental traits to resources levels and possibly climatic factors such as temperature. Populations from the different habitats were equally successful based on the reproductive output and the size of colonies. Data from the reciprocal transplants, however, suggested that populations constituted ecotypes: while individuals from dry habitat origin were successful in both native and foreign habitat, individuals of a wet habitat origin failed at reproduction in the foreign habitat, Analysis of foraging behavior showed that while some of the behavioral aspects that differed geographically exhibited plasticity, others, such as the tendency to capture and feed on prey as a group, exhibited divergence between populations. Individuals from populations with low resources exhibited plasticity for this trait while individuals from high resource habitats did not change between solitary and group foraging in response to different prey levels. The correspondence between reproductive effort and plasticity in group foraging suggests that the expression of this behavior might be responsible of the success of populations of P. bistriata in habitats with low resources.