Per-capita productivity in a social wasp: no evidence for a negative effect of colony size

Abstract

Optimal colony size in eusocial insects likely reflects a balance between ecological factors and factors intrinsic to the social group. In a seminal paper Michener (1964) showed for some species of social Hymenoptera that colony production of immature stages (productivity), when transformed to a per-female basis, was inversely related to colony size. He concluded that social patterns exist in the social insects that cause smaller groups to be more efficient than larger groups. This result has come to be known as "Micheners paradox" because it suggests that selection on efficiency would oppose the evolution of the large and complex societies that are common in the social insects. Michener suggested that large colony size has other advantages, such as improved defense and homeostasis, that are favored by selection. For his analysis of swarm-founding wasps, Michener combined data from colonies of different species and different developmental stages in order to obtain adequate sample sizes; therefore, his study did not make a strong case that efficiency decreases with increasing colony size (across colonies) in these wasps. We tested Micheners hypothesis on the Neotropical swarm-founding wasp Parachartergus fraternus, while controlling for stage of colony development. We found that small colonies were more variable in percapita productivity relative to larger colonies, but found no evidence for a negative relationship between efficiency and size across colonies.

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

“…This result is contrary to the trend first noted by Michener (1964) (see discussion in Karsai and Wenzel 1998) that per capita productivity decreases as group size increases (but see Bouwma et al 2005Bouwma et al , 2006. However, some other facultatively social species show no per capita productivity decrease when moving from solitary to social nesting.…”

“…However, many facultatively and/or primitively social species show an increase in per capita productivity when moving from solitary to social groups (Schwarz 1994;Tierney et al 1997Tierney et al , 2000Tierney et al , 2002Schwarz et al 1998;Field et al 1999Field et al , 2000Hogendoorn and Zammit 2001;Coelho 2002;Joyce and Schwarz 2006;Thompson and Schwarz 2006), and even in larger-colony species, the negative relationship may not be universal (Bouwma et al 2005(Bouwma et al , 2006. Studies of per capita productivity that are based on nest collections may overestimate productivity of small groups by ignoring failed nests (douse 2001).…”

Polyethism in an Oriental Hornet (Vespa orientalis) Colony

“…Apparently, the enlargement of the nest by digging is under certain conditions a secondary activity, whereas tending to the brood and to the nest proper is preferable activities. A similar occurrence of polyethism and work assignment dependent on size of the population has been reported in various other species of wasps [14][15][16][17][18][19]. As for the appearance of age polyethism entailing initial work within the nest and subsequent activity also outside the nest, this has been widely observed in other species of social insects.…”

Why do not all workers work? Colony size and workload during emigrations in the ant Temnothorax albipennis

“…For example, previous work on communication has suggested that larger colonies may be more successful at foraging with recruitment (Beckers et al 1989;Beekman et al 2001;Mailleux et al 2003), less successful (Jun and Pepper 2003) or collect an equal amount of resource per forager with or without recruitment . Similarly, results on productivity and its relationship with colony size are also mixed (increasing- Jeanne and Nordheim 1996;Tibbetts and Reeve 2003;Sorvari and Hakkarainen 2007;decreasing-Michener 1964;Karsai and Wenzel 1998;no clear relationship-Strohm and Bordon-Hauser 2003;Bouwma et al 2006). It is thus likely that colony size may have different effects in different species-and, indeed, this is to be expected, given that selection has shaped social insects to vary in colony size.…”