Caste allocation in litter Pheidole: lessons from plant defense theory

Abstract

Springer-Verlag 1995 M i c h a e l K a s p a r i • M a r g a r e t M . B y r n e A b s t r a c t The allocation to growth, defense and reproduction varies in social insects within a species' life cycle and between species. A life cycle model (Oster and Wilson 1978) generally failed to predict caste allocation in small litter-nesting colonies of NeotropicalPheidole. Two of its assumptions were often invalid:food was unlikely to be limiting in four of five populations, and sexual biomass production accelerated, not decelerated, with colony size in three of five populations. One of five Pheidole populations studied had higher caste ratios (soldiers/workers) in reproductive colonies as predicted, and in no species did caste functions conform to predictions. We also adapted three models from plant defense theory to study betweenspecies patterns of caste allocation. Among 12 litter Pheidole the amount of sterile biomass devoted to soldiers varied from 18 to 62%. Queen size, growth rate, and soldier investment positively covaried. Only one model, the cost of replacement hypothesis (McKey 1979), correctly predicted that species with costly female alates invest more in defense. The two hypotheses linking apparency to defense may also be valid if fast, growing colonies are more likely to attract the attention of predators. K e y w o r d s C a s t e •

The scaling of growth, reproduction and defense in colonies of Amazonian Termites

“…Whether this is high enough to prevent colonies from reaching their limiting size is unclear. Yet, a non-saturating increase in colony productivity with colony size has also been reported for many ants and other hymenopterans (Kaspari & Byrne, 1995;Kaspari, 1996;Billick, 2001;Bouwma et al, 2006;McGlynn, 2006;Smith et al, 2007). Taken together, these results suggest that, under natural conditions, colony growth is less constrained than usually assumed.…”

“…This result also contrasts with the suggestion of a colony size threshold for reproduction in termites, albeit this is based on very few species (Lepage & Darlington, 2000). In the better studied Hymenoptera, the uncoupling between reproduction and colony size seems to be at least as common as size-dependent reproduction within species (Kaspari & Byrne, 1995;Beekman et al, 1998;Cole, 2009). Importantly, we found that alate number was independent of worker number even when considering breeding colonies only, so that variation in breeding status among colonies cannot account for this result.…”

“…Empirical tests of the above predictions have provided mixed results: productivity does not always level off as colonies grow (Poitrineau et al, 2009;Dornhaus et al, 2012;Kramer et al, 2014), colony reproductive effort is often independent of colony size (Cole, 2009;Dornhaus et al, 2012), and soldier allocation strategy only partially matches theoretical expectations (Walker & Stamps, 1986;Kaspari & Byrne, 1995;Dornhaus et al, 2012). However, such conclusions are heavily biased towards hymenopterans, particularly ants.…”

Ecological strategies of (pl)ants: Towards a world‐wide worker economic spectrum for ants

“…have multiple queens). Polygyny is in turn correlated with dependent colony founding and ecological dominance (Boulay et al, 2014 ) and hypothesised to be associated with morphological differentiation in the worker caste (worker polymorphism; Bourke, 1999 ; Anderson & McShea, 2001 ), with fast‐growing colonies investing more in soldier castes (Kaspari & Byrne, 1995 ). Furthermore, polygyny may facilitate social parasitism because colonies accept returning young queens (Buschinger, 1990 ).…”

Extraordinary starvation resistance in Temnothorax rugatulus (Hymenoptera, Formicidae) colonies: Demography and adaptive behavior

“…According to the superorganism concept, the functionally sterile workers can be compared to somatic tissue and the reproductive queens to the germ line (Oster and Wilson, 1978;Moritz and Fuchs, 1998). Like multicellular organisms, social insect colonies display trade-offs in resource allocation between growth, defense, and reproduction (Sudd and Franks, 1987;Bourke and Franks, 1995;Kaspari and Byrne, 1995). Colony mortality and resource allocation trade-offs are fundamentally different between colonies with one queen (monogynous), in which colony survival is determined by queen survival (Franks et al, 1990a;Pamilo, 1991), and polygynous colonies (with several queens) in which colonies are potentially immortal through serial polygyny (Seppa, 1994).…”