Relative colony size of parabiotic species demonstrates inversion with growth

Abstract

Ant-gardens are a mutualistic association involving epiphyte plants and one or several ant species. Ant-gardens inhabited by Camponotus femoratus (Fabricius, 1804) and Crematogaster levior (Longino, 2003), are the most commonly found in the Neotropical Region. These two ant species share the nest and their foraging trails but keep their brood separated (i.e., parabiosis). The larger Ca. femoratus defends the nest, while benefits from the foraging ability of C. levior. However, it is still not experimentally proven which of the two parabiotic species initiates nest building. Moreover, the growth dynamic of population for these two ant species is unknown. To address these topics, we analyzed the change in proportion of individuals from the two species depending on the nest volume. Our results show that (1) the proportion of Ca. femoratus workers increased with nest volume leading to a numerically domination of Ca. femoratus in the largest nests and (2) C. levior workers are likely to initiate the nest construction given that it represents the overwhelming majority of the small nests. These results reinforce the knowledge of the complex and understudied interaction between these two ant species. Ant-gardens arise as a mutualistic association between ants and epiphyte plants. Plants benefit from the dispersal of their seeds and defense by the patrolling ants, while provide nest structure to the ants. The ants Crematogaster levior and Camponotus femoratus live within common Ant-gardens. We studied the growth dynamic of the two species population with the volume of the Ant-garden nest. The proportion of Ca. femoratus increases with the nest volume resulting in a domination of the latter species on C. levior in the largest nets. Furthermore, our results, combined with field observations, suggest that C. levior can initiate the nest construction. These findings precise the complex relationship between the two ant species.