Presentation Title

Hybrid Worker Size Variation Between Interbreeding Desert Seed Harvester Ant Lineages

Abstract

Hybridogenetic species depend on interbreeding with a second species to reproduce successfully. Two hybridogenetic lineages of Pogonomyrmex harvester ants, J1 and J2, directly compete for resources, but at the same time inter-dependently breed to produce the sterile worker offspring that perform tasks vital to colony survival, growth, and reproduction. Because colonies can produce fewer workers as they become more common, the lineages should stabilize at a 50:50 ratio, but instead lineages in the field maintain a 60:40 J2:J1 ratio. This suggests an ecological advantage contributing to skewing of the ratio. One possibility is that J2 colonies produce larger workers, giving them a competitive advantage. In this study, I tested if J2 workers are larger by sampling workers from field colonies and measuring head width as a proxy for body size. To investigate whether hybridization frequency influences worker production, colonies were reared under common-garden laboratory conditions for 18 months, genotyped at 12 microsatellite loci to determine the number of inter-lineage matings, and measured for colony size and mean head width. Head widths of field-collected workers from the two lineages did not differ, although J2 colonies were more variable in worker size than J1 colonies. In lab analysis is ongoing

Primary Faculty Mentor Name

Sara Cahan

Status

Undergraduate

Student College

College of Arts and Sciences

Program/Major

Biological Science

Primary Research Category

Biological Sciences

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Hybrid Worker Size Variation Between Interbreeding Desert Seed Harvester Ant Lineages

Hybridogenetic species depend on interbreeding with a second species to reproduce successfully. Two hybridogenetic lineages of Pogonomyrmex harvester ants, J1 and J2, directly compete for resources, but at the same time inter-dependently breed to produce the sterile worker offspring that perform tasks vital to colony survival, growth, and reproduction. Because colonies can produce fewer workers as they become more common, the lineages should stabilize at a 50:50 ratio, but instead lineages in the field maintain a 60:40 J2:J1 ratio. This suggests an ecological advantage contributing to skewing of the ratio. One possibility is that J2 colonies produce larger workers, giving them a competitive advantage. In this study, I tested if J2 workers are larger by sampling workers from field colonies and measuring head width as a proxy for body size. To investigate whether hybridization frequency influences worker production, colonies were reared under common-garden laboratory conditions for 18 months, genotyped at 12 microsatellite loci to determine the number of inter-lineage matings, and measured for colony size and mean head width. Head widths of field-collected workers from the two lineages did not differ, although J2 colonies were more variable in worker size than J1 colonies. In lab analysis is ongoing