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Does an ecological advantage produce the asymmetric lineage ratio in a harvester ant population?

Gordon DM, Pilko A, De Bortoli N, Ingram KK - Oecologia (2013)

Bottom Line: Mature colonies of the two lineages did not differ in nest mound size, foraging activity, or the propensity to relocate their nests.There were no strong differences in the relative recruitment or survivorship of the two lineages.Our results show no ecological advantage for either lineage, indicating that differences between the lineages in sex ratio allocation may be sufficient to maintain the current asymmetry of the lineage ratio in this population.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Stanford University, Stanford, CA, 94305-5020, USA, dmgordon@stanford.edu.

ABSTRACT
In dependent-lineage harvester ant populations, two lineages interbreed but are genetically distinct. The offspring of a male and queen of the same lineage are female reproductives; the offspring of a male and queen of different lineages are workers. Geographic surveys have shown asymmetries in the ratio of the two lineages in many harvester ant populations, which may be maintained by an ecological advantage to one of the lineages. Using census data from a long-term study of a dependent-lineage population of the red harvester ant, Pogonomyrmex barbatus, we identified the lineage of 130 colonies sampled in 1997-1999, ranging in age from 1 to 19 years when collected, and 268 colonies sampled in 2010, ranging in age from 1 to 28 years when collected. The ratio of lineages in the study population is similar across an 11-year interval, 0.59 J2 in 1999 and 0.66 J2 in 2010. The rare lineage, J1, had a slightly but significantly higher number of mates of the opposite lineage than the common lineage, J2, and, using data from previous work on reproductive output, higher male production. Mature colonies of the two lineages did not differ in nest mound size, foraging activity, or the propensity to relocate their nests. There were no strong differences in the relative recruitment or survivorship of the two lineages. Our results show no ecological advantage for either lineage, indicating that differences between the lineages in sex ratio allocation may be sufficient to maintain the current asymmetry of the lineage ratio in this population.

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One-year-old colonies of Pogonomyrmex barbatus by lineage. Open bars show the number of one-year-old J1 colonies in a given year, filled bars show the number of one-year-old colonies of J2
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Fig1: One-year-old colonies of Pogonomyrmex barbatus by lineage. Open bars show the number of one-year-old J1 colonies in a given year, filled bars show the number of one-year-old colonies of J2

Mentions: The lineage ratio of J2:J1 remained relatively stable across 11 years. Using only the 130 colonies sampled in 1997–1999, the proportion of colonies that were J2 was 0.59. Using only the 268 colonies sampled in 2010, many of which were alive in 1999 and earlier, the proportion of colonies that were J2 was 0.66. The numbers of new colonies of each lineage varied from year to year, with more J2 than J1 colonies in all but 3 of the years between 1986 and 2011 (Fig. 1). Table 2 shows the numbers of colonies in the two samples that were alive in each year, using the data on colony age from the long-term census.Fig. 1


Does an ecological advantage produce the asymmetric lineage ratio in a harvester ant population?

Gordon DM, Pilko A, De Bortoli N, Ingram KK - Oecologia (2013)

One-year-old colonies of Pogonomyrmex barbatus by lineage. Open bars show the number of one-year-old J1 colonies in a given year, filled bars show the number of one-year-old colonies of J2
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3824609&req=5

Fig1: One-year-old colonies of Pogonomyrmex barbatus by lineage. Open bars show the number of one-year-old J1 colonies in a given year, filled bars show the number of one-year-old colonies of J2
Mentions: The lineage ratio of J2:J1 remained relatively stable across 11 years. Using only the 130 colonies sampled in 1997–1999, the proportion of colonies that were J2 was 0.59. Using only the 268 colonies sampled in 2010, many of which were alive in 1999 and earlier, the proportion of colonies that were J2 was 0.66. The numbers of new colonies of each lineage varied from year to year, with more J2 than J1 colonies in all but 3 of the years between 1986 and 2011 (Fig. 1). Table 2 shows the numbers of colonies in the two samples that were alive in each year, using the data on colony age from the long-term census.Fig. 1

Bottom Line: Mature colonies of the two lineages did not differ in nest mound size, foraging activity, or the propensity to relocate their nests.There were no strong differences in the relative recruitment or survivorship of the two lineages.Our results show no ecological advantage for either lineage, indicating that differences between the lineages in sex ratio allocation may be sufficient to maintain the current asymmetry of the lineage ratio in this population.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Stanford University, Stanford, CA, 94305-5020, USA, dmgordon@stanford.edu.

ABSTRACT
In dependent-lineage harvester ant populations, two lineages interbreed but are genetically distinct. The offspring of a male and queen of the same lineage are female reproductives; the offspring of a male and queen of different lineages are workers. Geographic surveys have shown asymmetries in the ratio of the two lineages in many harvester ant populations, which may be maintained by an ecological advantage to one of the lineages. Using census data from a long-term study of a dependent-lineage population of the red harvester ant, Pogonomyrmex barbatus, we identified the lineage of 130 colonies sampled in 1997-1999, ranging in age from 1 to 19 years when collected, and 268 colonies sampled in 2010, ranging in age from 1 to 28 years when collected. The ratio of lineages in the study population is similar across an 11-year interval, 0.59 J2 in 1999 and 0.66 J2 in 2010. The rare lineage, J1, had a slightly but significantly higher number of mates of the opposite lineage than the common lineage, J2, and, using data from previous work on reproductive output, higher male production. Mature colonies of the two lineages did not differ in nest mound size, foraging activity, or the propensity to relocate their nests. There were no strong differences in the relative recruitment or survivorship of the two lineages. Our results show no ecological advantage for either lineage, indicating that differences between the lineages in sex ratio allocation may be sufficient to maintain the current asymmetry of the lineage ratio in this population.

Show MeSH