Eldridge S. Adams

Reproductive dynamics and colony structure of subterranean termites of the genus Reticulitermes (Isoptera Rhinotermitidae): a review of the evidence from behavioral, ecological, and genetic studies

(1) In subterranean termites of the genus Reticulitermes, colonies are difficult to delineate because physical nest structures are concealed or amorphous, and colony boundaries are difficult to define. The ambiguity of colony architecture and the cryptic nesting and feeding habits of these ecologically and economically important termites hinder our understanding of their population biology. We review and synthesize current information on Reticulitermes life history, reproduction, and genetics to develop an understanding of colony and population structure, and possible modes of reproductive organization. (2) To infer colony structure, we simulate several breeding systems that might be found in Reticulitermes and determine the F statistics and relatedness coefficients expected for groups of workers drawn from the simulated populations. Available field data on the distribution of worker genotypes within and among colonies are then used to distinguish between alternate hypotheses regarding population and bree...

Variation in colony structure in the subterranean termite Reticulitermes flavipes

Abstract The genetic organization of colonies of the subterranean termite Reticulitermes flavipes in two subpopulations in Massachusetts was explored using five polymorphic allozymes and double-strand conformation polymorphism (DSCP) analysis of the mitochondrial control region. Empirically obtained estimates of worker relatedness and F-statistics were compared with values generated by computer simulations of breeding schemes to make inferences about colony organization. In one study site (G), worker genotypes indicated the presence of a mixture of colonies headed by monogamous outbred primary reproductives and colonies headed by inbreeding neotenic reproductives, both colony types having limited spatial ranges. A second site (S) was dominated by several large colonies with low relatedness among nestmates. Mixed DSCP haplotypes in three colonies indicated that nestmates had descended from two or three unrelated female reproductives. Computer simulations of breeding schemes suggested that positive colony inbreeding coefficients at site S resulted from either commingling of workers from different nests or different colonies. Such an exchange of workers between nests corresponds to the multiple-site nesting lifetype of many subterranean termites and resembles colony structure in polycalic Formica ants. Our study demonstrates considerable variation in R. flavipes colony structure over a small spatial scale, including colonies headed by monogamous outbred primary reproductives, colonies containing multiple inbred neotenic reproductives and large polydomous colonies containing the progeny of two or more unrelated queens, and suggests that the number of reproductives and nestmate relatedness change with colony age and size.

Territory area and colony size in the fire ant Solenopsis invicta

1. The allometry of colony mass to territory area governs the total biomass of ants that a given habitat supports. This relationship serves as an important link between the performance of individual colonies and the behaviour of populations experiencing density-dependent competition for space. 2. Territory area, colony mass, and the numbers of ants of each caste and developmental stage, were measured for colonies of the fire ant Solenopsis invicta across a wide range of sizes. 3. Most of the variation in territory area was explained by colony size, measured either by worker number, worker biomass or colony biomass. 4. The nature of this relationship was linear in May, when colonies were near their annual minimum size, but non-linear in November, when they were near their annual maximum. Territories of a given size were occupied by larger colonies in November than May, probably because in this saturated population the simultaneous increase in worker number in all colonies occurred without room for territorial expansion. 5. Mound volume, which can be quickly measured without disturbing the colony, provided a reasonable estimate of colony or worker biomass and explained most of the variance in territory size.

Bayesian analysis of linear dominance hierarchies

Studies on social animals often seek to identify dominance hierarchies, in which individuals are ranked according to competitive abilities based on counts of wins and losses in pairwise encounters. I illustrate Bayesian approaches, based on the method of paired comparisons, for determining ranks and for estimating relationships between dominance ability and other attributes. Bayesian inference combines prior probability distributions for each unknown parameter with likelihood functions to produce the joint posterior probability distribution for the quantities of interest. In contrast to nonparametric techniques for inferring ranks, Bayesian models yield measures of certainty for each inference and allow rigorous estimates of correlations between ranks and covariates even when there is considerable uncertainty as to the ranks themselves. A possible objection to the Bayesian approach is that it appears to entail more restrictive assumptions than do simpler methods. However, simulations show that Bayesian inferences are more robust to deviations from these assumptions than are the results of nonparametric methods.

Animal Contests as Evolutionary Games

Animal Contests as Evolutionary Games: Paradoxical behavior can be understood in the context of evolutionary stable strategies. The trick is to discover which game the animal is playing Author(s): Michael Mesterton-Gibbons and Eldridge S. Adams Reviewed work(s): Source: American Scientist, Vol. 86, No. 4 (JULY-AUGUST 1998), pp. 334-341 Published by: Sigma Xi, The Scientific Research Society Stable URL: http://www.jstor.org/stable/27857057 . Accessed: 14/11/2011 21:23

Density-Dependent Competition in Fire Ants: Effects on Colony Survivorship and Size Variation

1. Competition among ants can drive changes in both the density and the sizes of colonies. Models of competitive interactions produce conflicting predictions concerning size variation; these predictions have not previously been tested in social insect populations. 2. To measure the effects of early competition on population dynamics of the fire ant Solenopsis invicta, 2284 incipient colonies, each grown from a single queen, were planted in replicate arrays in an irrigated field. In a series of three experiments, colonies were planted in square grids with either 13-5, 15, 40, 60 or 120 cm between nearest neighbours. 3. Soon after planting, active colonies organized brood raids, which ended when victorious colonies acquired the brood and workers of one or more neighbours. 4. Initial colony density had strong effects upon the percentage of colonies engaged in raids, which ranged from 0% at the lowest density to 68-5% at the highest density. High colony density markedly increased raid complexity, colony mortality and queen migration. 5. The complex brood raids seen at high colony density rapidly reorganized clusters of incipient colonies. Excavation of surviving colonies showed that the number of workers per colony was more variable on plots with numerous raids; thus, competition by brood raiding tended to increase the degree of size inequality among colonies. This result is consistent with models and observations of «asymmetric competition» among sessile organisms. 6. During raids, queens sometimes moved to nearby nests where they joined or usurped the original queen. Queen usurpation was especially likely on high-density plots. 7. Brood raids were restricted to the first few weeks following worker emergence and were reduced by low surface moisture, apparently because worker activity declines in dry conditions. By 10 weeks following emergence, the ants developed intolerance of workers from neighbouring colonies, and the mechanism of competition changed from brood raids to group fighting at food resources or foraging trails

Relatedness, recognition errors, and colony fusion in the termite Nasutitermes corniger

Loss of aggression between social groups can have far-reaching effects on the structure of societies and populations. We tested whether variation in the genetic structure of colonies of the termite Nasutitermes corniger affects the probability of aggression toward non-nestmates and the ability of unrelated colonies to fuse. We determined the genotypes of workers and soldiers from 120 colonies at seven polymorphic microsatellite loci. Twenty-seven colonies contained offspring of multiple founding queens or kings, yielding an average within-colony relatedness of 0.33. Genotypes in the remaining 93 colonies were consistent with reproduction by a single queen and king or their progeny, with an average within-colony relatedness of 0.51. In standardized assays, the probability of aggression between workers and soldiers from different colonies was an increasing function of within-colony relatedness. The probability of aggression was not affected significantly by the degree of relatedness between colonies, which was near zero in all cases, or by whether the colonies were neighbors. To test whether these assays of aggression predict the potential for colony fusion in the field, we transplanted selected nests to new locations. Workers and soldiers from colonies that were mutually tolerant in laboratory assays joined their nests without fighting, but workers and soldiers that were mutually aggressive in the assays initiated massive battles. These results suggest that the presence of multiple unrelated queens or kings promotes recognition errors, which can lead to the formation of more complex colony structures.

An empirical test of Lanchester's square law: mortality during battles of the fire ant Solenopsis invicta

Lanchesters models of attrition describe casualty rates during battles between groups as functions of the numbers of individuals and their fighting abilities. Originally developed to describe human warfare, Lanchesters square law has been hypothesized to apply broadly to social animals as well, with important consequences for their aggressive behaviour and social structure. According to the square law, the fighting ability of a group is proportional to the square of the number of individuals, but rises only linearly with fighting ability of individuals within the group. By analyzing mortality rates of fire ants (Solenopsis invicta) fighting in different numerical ratios, we provide the first quantitative test of Lanchesters model for a non-human animal. Casualty rates of fire ants were not consistent with the square law; instead, group fighting ability was an approximately linear function of group size. This implies that the relative numbers of casualties incurred by two fighting groups are not strongly affected by relative group sizes and that battles do not disproportionately favour group size over individual prowess.

Landmarks in Territory Partitioning: A Strategically Stable Convention?

A convention is a rule based on arbitrary cues that allows quick resolution of potentially protracted disputes. A familiar example is the Bourgeois strategy, in which the second of two animals to discover a resource yields it to the first, even though it may be stronger than its opponent. Here we develop a game‐theoretic model to show that neighbors with imperfect information about one another’s fighting abilities can be favored to accept a landmark as the designator of a territory boundary, even when the resulting territory is smaller than the one that would have been won through fighting. Thus, the use of landmarks or other mutually obvious solutions can serve as a convention for territory partitioning. For a distribution of fighting ability with low variance and high skew, there is a remarkably high probability that an animal will accept a smaller territory than it would have won through fighting. The analysis provides a possible explanation for the observed use of landmarks as boundary markers by territorial animals in a variety of taxa, including birds, fish, insects, and mammals. The analysis also suggests why territory boundaries are stable, once established, despite changes in characteristics of the residents or the environment.

Lack of evidence for nepotism by workers tending queens of the polygynous termite Nasutitermes corniger

Kin selection theory predicts that workers in social insect colonies should preferentially aid close relatives over less related or unrelated individuals if such behaviors increase inclusive fitness. For example, a worker in a polygynous (multiple-queen) colony is predicted to tend its own mother rather than an unrelated queen if this nepotistic behavior increases its mother’s reproductive success in excess of costs. Despite predictions, experimental tests conducted in the social Hymenoptera have found no clear evidence of nepotism. No tests for nepotism have been carried out in the Isoptera (termites), another major insect taxon showing highly developed sociality. We tested for nepotistic behavior in the termite Nasutitermes corniger by determining if workers preferentially fed and groomed their mothers in a laboratory assay. We collected workers from nine naturally occurring multiple-queen colonies as they tended queens and determined their parentage using highly variable microsatellite markers. Our results provide no evidence that workers tend their mothers in preference to co-occurring queens. The absence of evidence for nepotism is consistent with previous results reported from numerous studies of eusocial hymenopterans.