Population and colony structure and morphometrics in the queen dimorphic little black ant, Monomorium sp. AZ-02, with a review of queen phenotypes in the genus Monomorium.

Robert A Johnson,Rick P Overson

doi:10.1371/journal.pone.0180595

Abstract

The North American little black ant, Monomorium sp. AZ-02 (subfamily Myrmicinae), displays a dimorphism that consists of alate (winged) and ergatoid (wingless) queens. Surveys at our field site in southcentral Arizona, USA, demonstrated that only one queen phenotype (alate or ergatoid) occurred in each colony during the season in which reproductive sexuals were produced. A morphometric analysis demonstrated that ergatoid queens retained all specialized anatomical features of alate queens (except for wings), and that they were significantly smaller and had a lower mass than alate queens. Using eight morphological characters, a discriminant analysis correctly categorized all queens (40 of 40) of both phenotypes. A molecular phylogeny using 420 base pairs of the mitochondrial gene cytochrome oxidase I demonstrated that alate and ergatoid queens are two alternative phenotypes within the species; both phenotypes were intermixed on our phylogeny, and both phenotypes often displayed the same haplotype. A survey of the genus Monomorium (358 species) found that wingless queens (ergatoid queens, brachypterous queens) occur in 42 of 137 species (30.6%) in which the queen has been described. These wingless queen species are geographically and taxonomically widespread as they occur on several continents and in eight species groups, suggesting that winglessness probably arose independently on many occasions in the genus.

Highlights

Dispersal polymorphisms have played a significant role in our understanding of population dynamics, dispersal dynamics, life history, and the physiological and biochemical basis of adaptation [1, 2]
This study extends our understanding of queen dimorphism for ants in general and this species in particular by: (1) conducting a morphometric analysis of alate and ergatoid queens, (2) determining if alate and ergatoid queens belong to the same gene pool, (3) assessing for type of reproductive queens produced in colonies, and (4) providing observations of mating flights in this species
Dispersal polymorphisms occur in a wide variety of insects, and they are well known in crickets and aphids [1, 71]

Summary

Introduction

Dispersal polymorphisms have played a significant role in our understanding of population dynamics, dispersal dynamics, life history, and the physiological and biochemical basis of adaptation [1, 2]. Such polymorphisms are common among insects, and typically consist of one form that is fully capable of flight and a second form that is flightless. AZ-02 level, these dimorphisms result from variation in genotype, environment, or from a combination of both; at the ultimate level, flight ability is associated with habitat persistence. Flight allows organisms to disperse from heterogeneous or temporary habitats, while flightlessness promotes survival in homogeneous or persistent habitats [2,3,4,5]

Methods

Results

Conclusion