Current Status of a Model System: The Gene Gp-9 and Its Association with Social Organization in Fire Ants

The Gp-9 gene in fire ants represents an important model system for studying the evolution of social organization in insects as well as a rich source of information relevant to other major evolutionary topics. An important feature of this system is that polymorphism in social organization is completely associated with allelic variation at Gp-9, such that single-queen colonies (monogyne form) include only inhabitants bearing B-like alleles while multiple-queen colonies (polygyne form) additionally include inhabitants bearing b-like alleles. A recent study of this system by Leal and Ishida (2008) made two major claims, the validity and significance of which we examine here. After reviewing existing literature, analyzing the methods and results of Leal and Ishida (2008), and generating new data from one of their study sites, we conclude that their claim that polygyny can occur in Solenopsis invicta in the U.S.A. in the absence of expression of the b-like allele Gp-9b is unfounded. Moreover, we argue that available information on insect OBPs (the family of proteins to which GP-9 belongs), on the evolutionary/population genetics of Gp-9, and on pheromonal/behavioral control of fire ant colony queen number fails to support their view that GP-9 plays no role in the chemosensory-mediated communication that underpins regulation of social organization. Our analyses lead us to conclude that there are no new reasons to question the existing consensus view of the Gp-9 system outlined in Gotzek and Ross (2007)

A 4D natural selection model illuminates the enigma of altruism in the Shedao pit viper

Cooperation, Evolution, Mutualism, Island biogeography, Complexity, A13, B49, B59, C72, C91, D63, D64, J16, Z13,

Ambidextrous Mandibles in the Fire Ant Solenopsis invicta.

The elongation and sharp teeth of ant mandibles are considered important adaptations that have contributed to ants successful colonization of terrestrial habitats worldwide. In extant ant species, mandibles function as hunting and defense weapons, as well as multipurpose tools for excavating soil, cutting leaves, capturing and butchering prey, harvesting seeds, and transporting brood. This article reports that the mandibles in the red imported fire ant, Solenopsis invicta Buren, are functionally ambidextrous. Individuals opened and closed each mandible in synchrony or independently depending on the requirement of the task at hand. Upon completion of a task, individuals were without a preference in the orientation of mandible overlap—right overlap or left overlap. Orientation of mandible overlap before and after performing a task was also examined in nine other ant species. No overlap orientation preference was observed in any of these ant species, suggesting that ambidextrous mandibles are a universal trait in ants. These findings add an increment of knowledge to the diverse functions of ant mandibles

The evolution of cooperative hierarchies through natural selection processes

Altruism, Skew selection, Bioeconomics, Parental exploitation, Tit-for-tat transactions, A13, B49, B59, C72, C91, D63, D64, J16, Z13,

Intraspecific and interspecific competition of Wyeomyia smithii (Diptera: Culicidae) in pitcher plant communities.

We investigated the inquiline communities found in the leaves of the purple pitcher plant Sarracenia purpurea L. No general patterns were found among the abundances of common species or in correlations between biotic and abiotic variables (pitcher volume, sediment volume, pH). Further, no support was found for successional patterns within the pitchers when leaf number was used as an estimate of pitcher age. Experiments were conducted to quantify the effects of two size classes of the mosquito Wyeomyia smithii (Coq.) (Culicidae) and cladocerans (family Daphnidae, subfamily Eurycerinae, species undetermined) on the growth and survival of the small-mosquito size class. In simulated pitchers maintained in growth chambers for 14 days, small mosquitoes and large mosquitoes sup- pressed small-mosquito growth, and large mosquitoes decreased small-mosquito survivor- ship. Cladocerans had no effect on small-mosquito growth or survival. In simultaneous experiments conducted in natural pitchers in the field, large mosquitoes suppressed small- mosquito abundance and growth; no other significant interactions were found

Fire ants self-assemble into waterproof rafts to survive floods

Why does a single fire ant Solenopsis invicta struggle in water, whereas a group can float effortlessly for days? We use time-lapse photography to investigate how fire ants S. invicta link their bodies together to build waterproof rafts. Although water repellency in nature has been previously viewed as a static material property of plant leaves and insect cuticles, we here demonstrate a self-assembled hydrophobic surface. We find that ants can considerably enhance their water repellency by linking their bodies together, a process analogous to the weaving of a waterproof fabric. We present a model for the rate of raft construction based on observations of ant trajectories atop the raft. Central to the construction process is the trapping of ants at the raft edge by their neighbors, suggesting that some “cooperative” behaviors may rely upon coercion