Patterns in nature are often attributed to heterogeneity in the environment, but at our study site, a shade coffee farm in southern Mexico, it has been demonstrated that despite an apparently homogenous environment from the perspective of the ant Azteca instabilis there is a distinct patchiness in the distribution of colonies, indicating a self-organized pattern. The aim of this project was to investigate patterns of colony establishment of A. instabilis in a shade coffee agroecosystem in the Soconusco region of Chiapas, Mexico. Specifically we wanted to determine if colonies within a cluster are satellite colonies that have budded off from a central colony or if there is a high degree of colony formation via new queens emanating from other clusters, and identify the presence and geographic extent of A. instabilis mega-colonies. Aggression tests were combined with genetic data to elucidate colony relationships, assuming that closely related colonies would be less aggressive to each other than distantly related colonies. Individuals from colonies within the same cluster and between different clusters were taken from the field and observed and scored for aggressive behaviors in individual trials. Additionally, mitochondrial sequences and microsatellites were used to assess relatedness within and between clusters.
Results/Conclusions
From aggression tests it appears that two ‘mega-colonies’ dominate the study site. Significant aggression was consistently observed between workers from ‘mega-colony’ A and ‘mega-colony’ B. However, very little aggression was observed within clusters of A. instabilis colonies as well as between clusters within the same ‘mega-colony.’ There appears to be a significant relationship between aggression and distance between nests in ‘mega-colony’ B (P =0.026) but this relationship seems to break down in ‘mega-colony’ A as aggression by distance was not significant (P =0.077). This may be indicative of different patterns of colony formation between the ‘mega-colonies.’ Sequences from a 250bp region of COI indicates significant divergence between the two ‘mega-colonies.‘ Within each ‘mega-colony‘ a 0.1-0.4% difference in sequences was observed while between ‘mega-colonies‘ there was an average of 17.1% difference. Microsatellite data will be used to examine relationships between clusters of nests within each ‘mega-colony.’ Aggression data, genetic analysis and morphological differences strongly indicate that 'mega-colony' A and B are distinct evolutionary units.