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Wiernasz DC, Cole BJ. The ontogeny of selection on genetic diversity in harvester ants. Proc Biol Sci 2022; 289:20220496. [PMID: 35673867 PMCID: PMC9174731 DOI: 10.1098/rspb.2022.0496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Selection may favour traits throughout an individual's lifetime or at a particular life stage. In many species of social insects, established colonies that are more genetically diverse outperform less diverse colonies with respect to a variety of traits that contribute to fitness, but whether selection favours high diversity in small colonies is unknown. We tested the hypothesis that selection favours genetically diverse colonies during the juvenile period using a multi-year field experiment with the harvester ant, Pogonomyrmex occidentalis. We used controlled matings to generate colonies that varied in genetic diversity and transplanted them into the field. We monitored their survival for seven (the 2015 cohort, n = 149) and six (the 2016 cohort, n = 157) years. Genetically more diverse colonies had greater survival, resulting in significant viability selection. However, in both cohorts survival was not influenced by genetic diversity until colonies were three years old. We suggest that changes in their internal organization enabled colonies to use the benefits of multiple genotypes, and discuss possible mechanisms that can generate this pattern.
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Affiliation(s)
- Diane C. Wiernasz
- Department of Biology and Biochemistry, University of Houston, Houston, TX, 77204-5001, USA
| | - Blaine J. Cole
- Department of Biology and Biochemistry, University of Houston, Houston, TX, 77204-5001, USA
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Cole BJ, Jordan D, LaCour-Roy M, O'Fallon S, Manaker L, Ternest JJ, Askew M, Garey D, Wiernasz DC. The benefits of being big and diverse: early colony survival in harvester ants. Ecology 2021; 103:e03556. [PMID: 34622941 DOI: 10.1002/ecy.3556] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 06/25/2021] [Accepted: 07/20/2021] [Indexed: 11/09/2022]
Abstract
In sessile organisms such as plants and benthic invertebrates, founding propagules typically suffer extremely high rates of mortality due to both extrinsic and intrinsic factors. Many social insect species share similarities with these groups, but factors influencing early colony survival are relatively unstudied. We used a field experiment to measure the importance of environmental quality relative to intrinsic colony properties in the harvester ant, Pogonomyrmex occidentalis, by monitoring the survival of 584 experimental colonies. We measured survival of transplanted colonies over four months in each of three years (2014-2016) at a site in western Colorado. Colony survival was primarily determined by colony features. Multiple mating by the queen and larger colony size at the time of transplant increased survival, but queen size, maternal lineage and the composition of plant species in the vicinity of the colony did not. Food supplementation increased survival significantly when natural food was scarce, but was not consistently beneficial, in contrast to predictions. Our results emphasize the general importance of rapid growth and early attainment of large size in the survival of sessile species. However, attributes specific to ants that are a consequence of their sociality also strongly affected survival. Colonies with multiply-mated queens were more likely to survive over a wide range of circumstances, highlighting the importance of this trait even at the early stages of colony life.
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Affiliation(s)
- Blaine J Cole
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, 77204-5001, USA
| | - Dayne Jordan
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, 77204-5001, USA
| | - Montrel LaCour-Roy
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, 77204-5001, USA
| | - Sean O'Fallon
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, 77204-5001, USA.,Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, 90095, USA
| | - Logan Manaker
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, 77204-5001, USA
| | - John J Ternest
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, 77204-5001, USA.,Department of Entomology and Nematology, University of Florida, Gainesville, Florida, 32608, USA
| | - Megan Askew
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, 77204-5001, USA
| | - Daniel Garey
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, 77204-5001, USA
| | - Diane C Wiernasz
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, 77204-5001, USA
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