Sociality level correlates with dispersal ability in spiders

• Published in: Functional ecology Vol. 26; no. 4; pp. 794 - 803
• Main Authors: Corcobado, Guadalupe, Rodríguez-Gironés, Miguel A., Moya-Laraño, Jordi, Avilés, Leticia
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing 01-08-2012; Blackwell Publishing Ltd; Wiley-Blackwell; Wiley Subscription Services, Inc
• Subjects: Anelosimus; Animal and plant ecology; Animal nesting; Animal, plant and microbial ecology; Arachnida; Autoecology; Behavioural ecology; Biological and medical sciences; Body size; bridging; Dispersal; Ecological genetics; Evolution; evolution of sociality; feedback mechanisms; Female animals; Fundamental and applied biological sciences. Psychology; General aspects; Human ecology; Inbreeding; Invertebrates; Male animals; social spiders; Sociality; Spiders; subsocial spiders; Ability; Social spider; Araneida; Dispersion; Anelosimus; social spiders; Arachnida; evolution of sociality; feedback mechanisms; Feedback; Arthropoda; subsocial spiders; Invertebrata; bridging
• ISSN: 0269-8463; 1365-2435
• DOI: 10.1111/j.1365-2435.2012.01996.x

1. The evolution of sociality alters the genetic structure of populations, often leading to an increase in the level of inbreeding and a concomitant decrease in the ratio between the benefits and costs of dispersal. 2. The association between an absence of dispersal and sociality in spiders has so far been established indirectly from the age distribution of colonies, their genetic structure and their sex ratio. Using a functional and mechanistic approach, we investigated the dispersal tendencies and abilities of individuals of both sexes in species of spiders with different degrees of sociality. We predicted that dispersal tendencies and abilities would decrease when sociality increased. 3. In seven species of Anelosimus (Theridiidae), we tested whether there is a sharp transition between dispersing subsocial species and non-dispersing social ones, or whether dispersal ability decreases more gradually as level of sociality increases and whether both sexes are equally affected. Our assays measured the propensity and ability to bridge, a common aerial locomotion mode in spiders that is especially relevant during pre-mating dispersal. 4. We found that the tendency to disperse by bridging and, at least in males, the ability to disperse, significantly decrease as the level of sociality increases, and that this occurs without a pronounced threshold between subsocial and social species. Additionally, we detected a reduction of leg length relative to body size with increasing sociality and decreasing dispersal abilities in males, which may be mechanistically related to their reduced ability to bridge. 5. We propose that the loss of dispersal ability associated with the evolution of sociality in spiders, especially in males, could contribute to the maintenance of their inbred social systems by substantially increasing dispersal costs.