Introduction:

The genetic variation between island and mainland populations of leaf-cutter ants have been poorly studied, despite its importance to understand their local dispersion, regional structure, and the distribution of one of the most abundant species in the neotropics.

Objective:

To analyze the genetic variation of an insular population of Atta cephalotes in a larger regional context in Central and South America.

Methods:

The Cytochrome Oxidase I gene of A. cephalotes was sequenced for the Gorgona Island and mainland populations in order to conduct an analysis of molecular variance, gene flow, and to calculate divergence time of haplogroups occurring in the island. An individual assignment test was conducted to estimate the spatial genetic connectivity and the distribution for this ant in the Eastern Tropical Pacific.

Results:

A total of 33 samples from the island and the Colombian mainland were compared to 389 Genebank accessions ofA. cephalotes from Central and South America. This leaf-cutter ant in the Gorgona Island is closely related to the Colombian mainland, despite that the separation between the island and the mainland likely constitute a barrier to gene flow. It is likely that two of the most common haplogroups on the continent arrived on the island recently. Therefore, the anthropogenic influence in the process of colonization of the island by this leaf-cutting ant cannot be excluded. A map of connectivity shows that this population has geographic limits that largely overlap with a biogeographic region within the Eastern Tropical Pacific. This trans-andean population accumulates 23 % of the maternally inherited diversity of theA. cephalotes.

Conclusions:

This leaf-cutter ant in the Gorgona Island and the Colombian Pacific is closely related to the Central American population and the whole region harbor a significant segment of A. cephalotes genetic diversity in South America.