Population and colony structure of an ant with territorial males, Cardiocondyla venustula

Abstract

Background: Many species of social insects have large-scale mating and dispersal flights and their populations are therefore often relatively homogenous. In contrast, dispersal on the wing appears to be uncommon in most species of the ant genus Cardiocondyla, because its males are wingless and the winged queens mate in their natal nests before dispersing on foot. Here we examine the population structure of C. venustula from South Africa. This species is of particular interest for the analysis of life history evolution in Cardiocondyla, as it occupies a phylogenetic position between tropical species with multi-queen (polygynous) colonies and fighting males and a Palearctic clade with single-queen colonies and mutually peaceful males. Males of C. venustula exhibit an intermediate strategy between lethal fighting and complete tolerancethey mostly engage in non-lethal fights and defend small territories inside their natal nests. We investigated how this reproductive behavior influences colony and population structure by analyzing samples on two geographic scales in South Africa: a small 40 × 40m 2 plot and a larger area with distances up to 5 km between sampling sites in Rietvlei Nature Reserve near Pretoria. Results: Colonies were found to be facultatively polygynous and queens appear to mate only with a single male. The extraordinarily high inbreeding coefficient suggests regular sib-mating. Budding by workers and young queens is the predominant mode of colony-founding and leads to high population viscosity. In addition, some queens appear to found colonies independently or through adoption into foreign nests. Conclusion: While C. venustula resembles tropical Cardiocondyla in queen number and mating frequency, it differs by the absence of winged disperser males. Dispersal by solitary, mated queens on foot or by short flights and their adoption by alien colonies might promote gene flow between colonies and counteract prolonged inbreeding. The abundance of suitable habitat and the high density of nests facilitate the spread of this species by budding and together with the apparent resistance against inbreeding make it a highly successful pioneer species and invader of degraded and man-made habitats.

Male‐biased dispersal in a fungus‐gardening ant symbiosis

“…For example, in some species, female birds tend to disperse farther than males, while male mammals tend to disperse farther than females (sex‐biased dispersal) (Greenwood, 1980; Trochet et al., 2016). While females form the core of societies in ants (and all social Hymenoptera), considerable variation exists among the dispersal abilities of males and reproductive females (Bourke & Franks, 1995; Cronin et al., 2013; Hakala et al., 2019; Helms, 2018; Jacobs & Heinze, 2019; Keller et al., 2014). For example, some ant species have wingless individuals (females or males) that can move across scales of just a few meters, or winged individuals that vary in their ability or tendency to disperse long distances (over hundreds of meters).…”

“…For example, in species where queens do not fly, males may fly and be responsible for most long‐distance dispersal (Berghoff et al., 2008; Hakala et al., 2019). In other species, wingless males and winged females may experience inbreeding due to a lack of dispersal (Jacobs & Heinze, 2019). In species with winged males and females, both sexes may contribute to long‐distance dispersal, gene flow, and near panmictic population structure (Johansson et al., 2018).…”

Development of a Set of Microsatellite Markers to Investigate Sexually Antagonistic Selection in the Invasive Ant Nylanderia fulva

“…Microsatellite loci are the primary marker of choice to study mating systems, such as the diversity of modes of reproduction and kinship structures observed in ants [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. These co-dominant markers are usually highly polymorphic, randomly spread throughout the genome and considered as neutral markers [ 19 ].…”

Male-Biased Dispersal in a Female-Dispersed Symbiosis

“…For example, in some species, female birds tend to disperse farther than males, while male mammals tend to disperse farther than females (sex-biased dispersal) (Greenwood, 1980;Trochet et al, 2016). While females form the core of societies in ants (and all social Hymenoptera), considerable variation exists among the dispersal abilities of males and reproductive females (Bourke & Franks, 1995;Cronin, Molet, Doums, Monnin, & Peeters, 2013;Hakala, Seppä, & Helanterä, 2019;Helms, 2018;Jacobs & Heinze, 2019;Keller, Peeters, & Beldade, 2014). For example, some ant species have wingless individuals (females or males) that can move across scales of just a few meters, or winged individuals that vary in their ability or tendency to disperse long distances (over hundreds of meters).…”

“…For example, in species where queens do not fly, males may fly and be responsible for most long-distance dispersal (Berghoff, Kronauer, Edwards, & Franks, 2008;Hakala et al, 2019). In other species, wingless males and winged females may experience inbreeding due to a lack of dispersal (Jacobs & Heinze, 2019). In species with winged males and females, both sexes may contribute to long-distance dispersal, gene flow, and near panmictic population structure (Johansson, Seppä, Helanterä, Trontti, & Sundström, 2018).…”