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Queen execution increases relatedness among workers of the invasive Argentine ant, Linepithema humile.

Inoue MN, Ito F, Goka K - Ecol Evol (2015)

Bottom Line: Polygyny in social insects can greatly reduce within-nest genetic relatedness.The significant deviation from Hardy-Weinberg equilibrium increased, and the relatedness among workers significantly increased from May to September in all supercolonies.This result suggested that the supercolonies replaced old queens with new ones during the reproductive season, thus supporting the plausibility of queen execution.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Biological Science Tokyo University of Agriculture and Technology 3-5-8 Saiwaicho Fuchu Tokyo 183-8509 Japan.

ABSTRACT
Polygyny in social insects can greatly reduce within-nest genetic relatedness. In polygynous ant species, potential rival queens in colonies with multiple queens are often executed by other queens, workers, or both. The Argentine ant, Linepithema humile, native to South America, forms a "supercolony" that is composed of a large number of nests and is considered to contribute to the ant's invasion success. Currently, four mutually antagonistic supercolonies are contiguously distributed within a small area of Japan. Here, we analyzed the genetic structure and relatedness within and among the four supercolonies using microsatellite markers to clarify how L. humile maintains its supercoloniality. The results of AMOVA and BASP, the F ST values, and the existence of several private alleles indicated that the L. humile population in the Kobe area had a characteristic genetic structure. Within a given supercolony, there was significant genetic differentiation (F ST) among workers collected in May and those collected in September. The significant deviation from Hardy-Weinberg equilibrium increased, and the relatedness among workers significantly increased from May to September in all supercolonies. This result suggested that the supercolonies replaced old queens with new ones during the reproductive season, thus supporting the plausibility of queen execution. From the perspective of kin selection, workers collectively eliminate queens, thereby increasing their own inclusive fitness. Restricted gene flow among supercolonies, together with mating with sib and queen execution, could help to maintain the unique social structure of L. humile, the distribution of which is expanding worldwide.

No MeSH data available.


Plot of log‐likelihood values [lnP(D)] as a function of K indicating the number of distinct groups for Linepithema humile sampled from 19 nests in the Kobe area in both May and September 2009, for a total of 38 nest–month combinations. All data were obtained from analysis of the microsatellite DNA loci using 20 runs with STRUCTURE. K values tested ranged from 1 to 20, with a burn‐in of 100,000 and with 100,000 Markov chain Monte Carlo iterations per value of K.
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ece31681-fig-0003: Plot of log‐likelihood values [lnP(D)] as a function of K indicating the number of distinct groups for Linepithema humile sampled from 19 nests in the Kobe area in both May and September 2009, for a total of 38 nest–month combinations. All data were obtained from analysis of the microsatellite DNA loci using 20 runs with STRUCTURE. K values tested ranged from 1 to 20, with a burn‐in of 100,000 and with 100,000 Markov chain Monte Carlo iterations per value of K.

Mentions: Figure 3 shows the relationship between lnP(D) and K. The lnP(D) values increased with increasing K until they reached a plateau at about K = 9. If the supercolonies had formed a significant genetic barrier to the flow of nuclear genes, we would have expected four population clusters to be revealed in this analysis; therefore, the lnP(D) values would have approached a maximum at K = 4. However, the curve failed to produce a clear peak at any value of K and the STRUCTURE analysis did not detect any signs of population structure in L. humile. The characteristics of the curve were not altered by extending the burn‐in period or by increasing the number of MCMC iterations. The log‐likelihood curve was further tested using the ΔK statistic, but this statistic also did not produce a distinct peak that would have been correlated with the most likely value of K. All individuals were assigned to one of the respective clusters with a probability of >82% at K = 4 according to the number of supercolonies using STRUCTURE (Fig. 4A). In contrast, BAPS identified eight homogenous units within the study area, indicating that each supercolony represented genetic differentiation between the seasons (Fig. 4B).


Queen execution increases relatedness among workers of the invasive Argentine ant, Linepithema humile.

Inoue MN, Ito F, Goka K - Ecol Evol (2015)

Plot of log‐likelihood values [lnP(D)] as a function of K indicating the number of distinct groups for Linepithema humile sampled from 19 nests in the Kobe area in both May and September 2009, for a total of 38 nest–month combinations. All data were obtained from analysis of the microsatellite DNA loci using 20 runs with STRUCTURE. K values tested ranged from 1 to 20, with a burn‐in of 100,000 and with 100,000 Markov chain Monte Carlo iterations per value of K.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4588641&req=5

ece31681-fig-0003: Plot of log‐likelihood values [lnP(D)] as a function of K indicating the number of distinct groups for Linepithema humile sampled from 19 nests in the Kobe area in both May and September 2009, for a total of 38 nest–month combinations. All data were obtained from analysis of the microsatellite DNA loci using 20 runs with STRUCTURE. K values tested ranged from 1 to 20, with a burn‐in of 100,000 and with 100,000 Markov chain Monte Carlo iterations per value of K.
Mentions: Figure 3 shows the relationship between lnP(D) and K. The lnP(D) values increased with increasing K until they reached a plateau at about K = 9. If the supercolonies had formed a significant genetic barrier to the flow of nuclear genes, we would have expected four population clusters to be revealed in this analysis; therefore, the lnP(D) values would have approached a maximum at K = 4. However, the curve failed to produce a clear peak at any value of K and the STRUCTURE analysis did not detect any signs of population structure in L. humile. The characteristics of the curve were not altered by extending the burn‐in period or by increasing the number of MCMC iterations. The log‐likelihood curve was further tested using the ΔK statistic, but this statistic also did not produce a distinct peak that would have been correlated with the most likely value of K. All individuals were assigned to one of the respective clusters with a probability of >82% at K = 4 according to the number of supercolonies using STRUCTURE (Fig. 4A). In contrast, BAPS identified eight homogenous units within the study area, indicating that each supercolony represented genetic differentiation between the seasons (Fig. 4B).

Bottom Line: Polygyny in social insects can greatly reduce within-nest genetic relatedness.The significant deviation from Hardy-Weinberg equilibrium increased, and the relatedness among workers significantly increased from May to September in all supercolonies.This result suggested that the supercolonies replaced old queens with new ones during the reproductive season, thus supporting the plausibility of queen execution.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Biological Science Tokyo University of Agriculture and Technology 3-5-8 Saiwaicho Fuchu Tokyo 183-8509 Japan.

ABSTRACT
Polygyny in social insects can greatly reduce within-nest genetic relatedness. In polygynous ant species, potential rival queens in colonies with multiple queens are often executed by other queens, workers, or both. The Argentine ant, Linepithema humile, native to South America, forms a "supercolony" that is composed of a large number of nests and is considered to contribute to the ant's invasion success. Currently, four mutually antagonistic supercolonies are contiguously distributed within a small area of Japan. Here, we analyzed the genetic structure and relatedness within and among the four supercolonies using microsatellite markers to clarify how L. humile maintains its supercoloniality. The results of AMOVA and BASP, the F ST values, and the existence of several private alleles indicated that the L. humile population in the Kobe area had a characteristic genetic structure. Within a given supercolony, there was significant genetic differentiation (F ST) among workers collected in May and those collected in September. The significant deviation from Hardy-Weinberg equilibrium increased, and the relatedness among workers significantly increased from May to September in all supercolonies. This result suggested that the supercolonies replaced old queens with new ones during the reproductive season, thus supporting the plausibility of queen execution. From the perspective of kin selection, workers collectively eliminate queens, thereby increasing their own inclusive fitness. Restricted gene flow among supercolonies, together with mating with sib and queen execution, could help to maintain the unique social structure of L. humile, the distribution of which is expanding worldwide.

No MeSH data available.