TY - JOUR

T1 - Queen-worker caste ratio depends on colony size in the pharaoh ant (Monomorium pharaonis)

AU - Schmidt, Anna Mosegaard

AU - Linksvayer, Timothy Arnold

AU - Boomsma, Jacobus Jan

AU - Pedersen, Jes Søe

PY - 2011

Y1 - 2011

N2 - The success of an ant colony depends on thesimultaneous presence of reproducing queens and nonreproducingworkers in a ratio that will maximize colonygrowth and reproduction. Despite its presumably crucialrole, queen–worker caste ratios (the ratio of adult queensto workers) and the factors affecting this variable remainscarcely studied. Maintaining polygynous pharaoh ant(Monomorium pharaonis) colonies in the laboratory hasprovided us with the opportunity to experimentally manipulatecolony size, one of the key factors that can be expectedto affect colony level queen–worker caste ratios and bodysize of eclosing workers, gynes and males. We found thatsmaller colonies produced more new queens relative toworkers, and that these queens and workers both tended tobe larger. However, colony size had no effect on the sizeof males or on the sex ratio of the individuals reared.Furthermore, for the first time in a social insect, we confirmedthe general life history prediction by Smith andFretwell (Am Nat 108:499–506, 1974) that offspring numbervaries more than offspring size. Our findings document ahigh level of plasticity in energy allocation toward femalecastes and suggest that polygynous species with buddingcolonies may adaptively adjust caste ratios to ensure rapidgrowth.

AB - The success of an ant colony depends on thesimultaneous presence of reproducing queens and nonreproducingworkers in a ratio that will maximize colonygrowth and reproduction. Despite its presumably crucialrole, queen–worker caste ratios (the ratio of adult queensto workers) and the factors affecting this variable remainscarcely studied. Maintaining polygynous pharaoh ant(Monomorium pharaonis) colonies in the laboratory hasprovided us with the opportunity to experimentally manipulatecolony size, one of the key factors that can be expectedto affect colony level queen–worker caste ratios and bodysize of eclosing workers, gynes and males. We found thatsmaller colonies produced more new queens relative toworkers, and that these queens and workers both tended tobe larger. However, colony size had no effect on the sizeof males or on the sex ratio of the individuals reared.Furthermore, for the first time in a social insect, we confirmedthe general life history prediction by Smith andFretwell (Am Nat 108:499–506, 1974) that offspring numbervaries more than offspring size. Our findings document ahigh level of plasticity in energy allocation toward femalecastes and suggest that polygynous species with buddingcolonies may adaptively adjust caste ratios to ensure rapidgrowth.

KW - Faculty of Science

KW - Caste

KW - COLONY SIZE

KW - Ergonomics

KW - Resource allocation

KW - Polygyny

U2 - 10.1007/s00040-010-0126-x

DO - 10.1007/s00040-010-0126-x

M3 - Journal article

VL - 58

SP - 139

EP - 144

JO - Insectes Sociaux

JF - Insectes Sociaux

SN - 0020-1812

IS - 2

ER -