Ecological constraints on independent nesting in facultatively eusocial hover wasps

Abstract

Recent ¢eld experiments suggest that cooperative breeding in vertebrates can be driven by a shortage of breeding territories. We did analogous experiments on facultatively eusocial hover wasps (Stenogastrinae: Liostenogaster £avolineata). We provided nesting opportunities by removing residents from 39 nests within a large aggregation (1995), and by glueing 20 nests obtained from a distant site into a second aggregation (1996). We prevented nest-less £oaters from competing for these opportunities in 1995 but not in 1996. In both years, helpers in unmanipulated groups were given opportunities to nest independently without having to incur nest-building costs and with a reduced wait before potential helpers emerged. Helpers visited the nests we provided, but adopted only a small proportion (5% of 111 vacancies created in 1995). Others were adopted by £oaters, but a signi¢cant proportion of nests were never adopted (9 out of 20 in 1995, 7 out of 20 in 1996). Helpers that visited nests did not originate from particular kinds of social group. Nests containing older broods were more likely to be adopted, and adopting females rarely destroyed older brood. A general feature of social insect, but not vertebrate life histories, namely the long period of o¡spring dependency relative to the short life expectancy of adult carers, may be a key factor constraining independent nesting.

Survival and productivity benefits to social nesting in the sweat bee Megalopta genalis (Hymenoptera: Halictidae)

“…Although our estimate is approximate, it shows that independently nesting females face a substantial risk of brood loss that can be reduced by group living. This risk of solitary nest failure is at the lower end of the range reported in other studies of APR models (Gadagkar 1991;Queller 1994;Eickwort et al 1996;Field et al 1998;Hogendoorn and Zammit 2001).…”

Predation risk is an ecological constraint for helper dispersal in a cooperatively breeding cichlid

“…In Seychelles warblers (Acrocephalus sechellensis) helpers modify their dispersal behaviour according to the territory quality of independent breeding options (Komdeur 1992;Komdeur et al 1995). By contrast, subordinates in the hover wasp (Liostenogaster flavolineata) were unlikely to accept nearby experimental high-quality breeding sites, a free nest provided by the experimenters, which seems to relate to the high benefits of queuing for a breeding position in this species (Field et al 1998(Field et al , 1999(Field et al , 2000. Third, this study demonstrates that predators affect helper dispersal.…”

“…First, the experimental removal of breeders resulted in helpers inheriting the breeding position (Brown & Brown 1981;Hannon et al 1985;Komdeur 1992;Walters et al 1992;Komdeur et al 1995;Balshine-Earn et al 1998;Field et al 1998;Shreeves & Field 2002) or nearby helpers dispersing and filling the vacancy (Pruett-Jones & Lewis 1990). These observations show that helpers are capable of independent breeding when given the opportunity, but are prevented from doing so by aggressive exclusion of competitors.…”

“…Although ecological constraints have often been assumed to be an important factor in forcing helpers to stay at home, experimental evidence is scarce. Experiments have been confined to manipulating the availability of (high quality) breeding opportunities in the neighbourhood of helpers, and subsequently measuring helper dispersal and independent breeding (Pruett-Jones & Lewis 1990;Ligon et al 1991;Du Plessis 1992;Komdeur 1992;Walters et al 1992;Komdeur et al 1995;Field et al 1998). So far, no study has manipulated other environmental/ecological factors, for example predation risk, that may influence the occurrence and extent of cooperative breeding and whether helpers stay at home rather than disperse.…”

Cooperation between non-relatives in a primitively eusocial paper wasp,Polistes dominula

“…If an unrelated subordinate helps to rear more offspring of the current dominant, she is likely to have more helpers and be more productive if she later inherits dominance herself: group productivity is positively correlated with group size, at least at the foundress stage [7,12], and is known to also correlate with group size at the worker stage where this has been investigated in other social insects [20]. This mechanism, of course, relies on worker offspring being unable to detect that the dominant is no longer their mother, or being prepared to rear the offspring of a less closely related individual: the evidence available suggests that this is the case [12,[21][22][23].…”