Evidence for loss of nepotism in the evolution of permanent sociality.
Kin selected benefits of cooperation result in pronounced kin discrimination and nepotism in many social species and favour the evolution of sociality. However, low variability in relatedness among group members, infrequent competitive interactions with non-relatives, and direct benefits of cooperation may relax selection for nepotism. We tested this prediction in a permanently social spider, Stegodyphus dumicola that appears to fulfil these conditions. Sociality is a derived trait, and kin discrimination exists in sub-social closely related congeners and is likely a selective force in the sub-social route to permanent sociality in spiders. We examined whether social spiders show nepotism in cooperative feeding when genetic relatedness among group members was experimentally varied. We found no effect of relatedness on feeding efficiency, growth rate or participation in feeding events. Previous studies on sub-social species showed benefits of communal feeding with kin, indicating nepotistic cooperation. The lack of evidence for nepotism in the social species suggests that kin discrimination has been lost or is irrelevant in communal feeding. Our results are consistent with the hypothesis that the role of nepotism is diminished when cooperation evolves in certain genetic and ecological contexts, e.g. when intra-group genetic relatedness is homogeneous and encounters with competitors are rare.
Mitrani Department of Desert Ecology, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, 84990, Israel.|Aarhus University, Department of Bioscience, Ny Munkegade 116, DK-8000 Aarhus C, Denmark.|BioCircuits Institute University of California, San Diego 9500 Gilman Drive, Mail Code 0328 La Jolla, CA 92093-0328, USA.
Reut
R
Berger-Tal
Mitrani Department of Desert Ecology, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, 84990, Israel.
Yael
Y
Lubin
Aarhus University, Department of Bioscience, Ny Munkegade 116, DK-8000 Aarhus C, Denmark.
Virginia
V
Settepani
Aarhus University, Department of Bioscience, Ny Munkegade 116, DK-8000 Aarhus C, Denmark.
Marija
M
Majer
Aarhus University, Department of Bioscience, Ny Munkegade 116, DK-8000 Aarhus C, Denmark.
Trine
T
Bilde
Aarhus University, Department of Bioscience, Ny Munkegade 116, DK-8000 Aarhus C, Denmark.|Ludwig Maximilians University Munich, Department Biology II, Großhaderner Str. 2, 82152 Planegg-Martinsried, Germany.
Cristina
C
Tuni
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D003163:Competitive Behavior / Q000502:physiology*; D003468:Cultural Evolution; D019143:Evolution, Molecular; D012919:Social Behavior; D012930:Social Dominance; D013112:Spiders / Q000235:genetics* / Q000502:physiology