Mutually beneficial host exploitation and ultra-biased sex ratios in quasisocial parasitoids

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

Casteless sociality in an allodapine bee and evolutionary losses of social hierarchies

Communal behaviour is a form of social behaviour where two or more females nest together and have no reproductive hierarchies. Communal behaviour has often been regarded as an evolutionary ‘stepping stone’ to more complex forms of sociality involving castes, as well as a social form derived from solitary behaviour with no further evolution towards eusociality. However, recent phylogenetic studies on halictine bees suggest that some instances of communal behaviour are derived from eusociality. Here, we describe social nesting in an allodapine bee, Braunsapis puangensis, which has been introduced to Fiji from southern Asia. We show that this bee has a casteless form of sociality similar to communal organization, but which has been derived from an ancestrally hierarchical social system. This is likely due to a combination of small benefits for social nesting that rapidly saturate as colonies become larger, along with low costs for dispersal. We suggest that casteless forms of sociality have frequently evolved from hierarchical societies across many insect groups, but the analyses required for recognizing such societies are often undeveloped and hampers comparative approaches. Transitions from hierarchical to casteless societies challenge the notion that eusociality is an evolutionary ‘end point’ and we argue that eusociality can, in some cases, be regarded as an evolutionary step towards egalitarian societies. We also suggest that evolutionary periods involving reproductive hierarchies could select for traits that allow individuals to better assess their social environment and subsequently enable lower reproductive skew.C. R. B. da Silva, M. I. Stevens, M. P. Schwar

Targeting the TGFβ signalling pathway in disease

Many drugs that target transforming growth factor-β (TGFβ) signalling have disease applications. Preclinical and clinical studies indicate the utility of these agents in fibrosis and oncology, particularly in augmentation of existing cancer therapies, such as radiation and chemotherapy, as well as in tumour vaccines. There are also reports of specialized applications, such as the reduction of vascular symptoms of Marfan syndrome. Here, we consider why the TGFβ signalling pathway is a drug target, the potential clinical applications of TGFβ inhibition, the issues arising with anti-TGFβ therapy and how these might be tackled using personalized approaches to dosing, monitoring of biomarkers as well as brief and/or localized drug-dosing regimens