title: Mutually beneficial host exploitation and ultra-biased sex ratios in quasisocial parasitoids.
abstract: Selfish interests usually preclude resource sharing, but under some conditions collective actions enhance per capita gains. Such Allee effects underlay early explanations of social evolution but current understanding focusses on kin selection (inclusive fitness). We find an Allee effect that explains unusual quasisociality (cooperative brood care) among parasitoid wasps without invoking or precluding kin selection effects. In Sclerodermus harmandi, individual females produce most offspring when exploiting small hosts alone. However, larger hosts are more successfully exploited by larger groups of females, with the per-female benefits outweighing the costs of host sharing. Further, the extremely biased sex ratios (97% female) are better explained by mutually beneficial female-female interactions that increase the reproductive value of daughters (local resource enhancement), rather than by the usually invoked local mate competition between males. Thus, atypical quasisocial behaviour in a parasitoid wasp directly enhances reproductive success and selects for very extremely female-biased sex ratios.
authors.affiliation: School of Plant Protection, Nanjing Agricultural University, No. 1 Weigang, Nanjing, Jiangsu 210095, China.
authors.forename: Xiuyun
authors.initials: X
authors.lastname: Tang
authors.affiliation: School of Plant Protection, Nanjing Agricultural University, No. 1 Weigang, Nanjing, Jiangsu 210095, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Meng
authors.affiliation: 1] School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK [2] Department of Biology, National University of Ireland Maynooth, County Kildare, Ireland.
authors.forename: Apostolos
authors.initials: A
authors.lastname: Kapranas
authors.affiliation: Forest Academy of Jiangsu Province, Dongshanqiao, Nanjing, Jiangsu 211153, China.
authors.forename: Fuyuan
authors.initials: F
authors.lastname: Xu
authors.affiliation: School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK.
authors.forename: Ian C W
authors.initials: IC
authors.lastname: Hardy
authors.affiliation: School of Plant Protection, Nanjing Agricultural University, No. 1 Weigang, Nanjing, Jiangsu 210095, China.
authors.forename: Baoping
authors.initials: B
authors.lastname: Li
mesh_terms: D000818:Animals; D061046:Biological Control Agents; D001517:Coleoptera / Q000469:parasitology; D005260:Female; D058507:Host Specificity; D007814:Larva / Q000469:parasitology; D008297:Male; D012098:Reproduction / Q000502:physiology; D012744:Sex Ratio; D012919:Social Behavior; D012931:Social Environment; D014863:Wasps / Q000502:physiology*
chemical_list: D061046:Biological Control Agents