Multiple queens means fewer mates

SummaryObligate multiple mating by social insect queens has evolved in some derived clades where higher genetic diversity is likely to enhance colony fitness [1–3]. The rare and derived nature of this behaviour is probably related to copulations being costly for queens, but fitness trade-offs between immediate survival and future reproductive success are difficult to measure and not well understood [1]. A corollary of this logic, that multiple mating should be less common or lost when genetic diversity among workers is achieved through multiple queens per colony, was suggested more than ten years ago [4]. However, large scale comparative analyses did not support this prediction, quite possibly because they did not contain any informative contrasts [1,2]. Only comparisons between closely related species with similar ecology and high queen-mating frequencies as ancestral state would provide decisive information, but such species pairs are exceedingly rare so that no case studies have been conducted and a comparative statistical approach [5] is impossible. Here we document for the first time that there is a clear link between the number of queens and the average number of matings of these queens, using the army ant Neivamyrmex carolinensis as a model system

Non-nest mate discrimination and clonal colony structure in the parthenogenetic ant Cerapachys biroi

Understanding the interplay between cooperation and conflict in social groups is a major goal of biology. One important factor is genetic relatedness, and animal societies are usually composed of related but genetically different individuals, setting the stage for conflicts over reproductive allocation. Recently, however, it has been found that several ant species reproduce predominantly asexually. Although this can potentially give rise to clonal societies, in the few well-studied cases, colonies are often chimeric assemblies of different genotypes, due to worker drifting or colony fusion. In the ant Cerapachys biroi, queens are absent and all individuals reproduce via thelytokous parthenogenesis, making this species an ideal study system of asexual reproduction and its consequences for social dynamics. Here, we show that colonies in our study population on Okinawa, Japan, recognize and effectively discriminate against foreign workers, especially those from unrelated asexual lineages. In accord with this finding, colonies never contained more than a single asexual lineage and average pairwise genetic relatedness within colonies was extremely high (r = 0.99). This implies that the scope for social conflict in C. biroi is limited, with unusually high potential for cooperation and altruis

Myrmecophiles

The term myrmecophile means ‘ant lover’, from the Greek ‘myrmex’ (ant) and ‘philos’ (loving). In the most general sense, any organism that is dependent on ants at least during part of its lifecycle is a myrmecophile. This definition encompasses plants that attract ants with food bodies or extrafloral nectaries, homopterans such as aphids, membracids, and scale insects that provide ants with honeydew, as well as fungi and bacteria that are cultivated or housed by some ants.Organismic and Evolutionary Biolog

Aphid-farming ants

Ivens and Kronauer provide an overview of the farming mutualism between ants and aphids, in which ants protect aphids in exchange for food

Data from: Cryptic diversity, high host specificity and reproductive synchronization in army ant-associated Vatesus beetles

Army ants and their arthropod symbionts represent one of the most species-rich animal associations on Earth, and constitute a fascinating example of diverse host-symbiont interaction networks. However, despite decades of research, our knowledge of army ant symbionts remains fragmentary due to taxonomic ambiguity and the inability to study army ants in the lab. Here we present an integrative approach that allows us to reliably determine species boundaries, assess biodiversity, match different developmental stages and sexes, and to study the life cycles of army ant symbionts. This approach is based on a combination of community sampling, DNA barcoding, morphology and physiology. As a test case, we applied this approach to the staphylinid beetle genus Vatesus and its different Eciton army ant host species at La Selva Biological Station, Costa Rica. DNA barcoding led to the discovery of cryptic biodiversity and, in combination with extensive community sampling, revealed strict host partitioning with no overlap in host range. Using DNA barcoding, we were also able to match the larval stages of all focal Vatesus species. In combination with studies of female reproductive physiology, this allowed us to reconstruct almost the complete life cycles of the different beetle species. We show that Vatesus beetles are highly adapted to the symbiosis with army ants, in that their reproduction and larval development are synchronized with the stereotypical reproductive and behavioral cycles of their host colonies. Our approach can now be used to study army ant-symbiont communities more broadly, and to obtain novel insights into co-evolutionary and ecological dynamics in species-rich host-symbiont systems

Data from: Low levels of hybridization in two species of African driver ants

Hybridization in ants can have consequences different from those observed in most other species, with many of the potential deleterious effects being mitigated due to haplodiploidy and eusociality. In some species where colonies are either headed by multiple queens or single queens that mate with many males, hybridization is associated with genetic caste determination, where hybrids develop into workers and purebred individuals develop into queens. A previous study suggested that hybridization occurs between two Dorylus army ant species with multiply mate queens. However, the extent and exact pattern of hybridization has remained unclear, and its possible effect on caste determination has not been investigated. In this study we aimed to determine the extent and direction of hybridization by measuring how frequently hybrids occur in colonies of both species, and to investigate the possibility of genetic caste determination. We show that hybridization is bidirectional and occurs at equal rates in both species. Hybrid workers make up only 1-2% of the population, and interspecific matings represent approximately 2% of all matings in both species. This shows that, while interspecific matings that give rise to worker offspring occur regularly, they are much rarer than intraspecific mating. Finally, we find no evidence of an association between hybridization and genetic caste determination in this population. This means that genetic caste determination is not a necessary outcome of hybridization in ants, even in species where queens mate with multiple males

Alignment CAD_wingless

Alignment of concatenated wg and CAD sequences of Vatesus beetles

COI phylogenetic tree

Newick tree file of COI sequences of Vatesus beetles

Data from: Can social partnerships influence the microbiome? insights from ant farmers and their trophobiont mutualists.

Mutualistic interactions with microbes have played a crucial role in the evolution and ecology of animal hosts. However, it is unclear what factors are most important in influencing particular host-microbe associations. While closely related animal species may have more similar microbiota than distantly related ones due to phylogenetic contingencies, social partnerships with other organisms, such as those in which one animal farms another, may also influence an organism’s symbiotic microbiome. We studied a mutualistic network of Brachymyrmex and Lasius ants farming several honeydew-producing Prociphilus aphids and Rhizoecus mealybugs to test whether the mutualistic microbiomes of these interacting insects are primarily correlated with their phylogeny or with their shared social partnerships. Our results confirm a phylogenetic signal in the microbiomes of aphid and mealybug trophobionts, with each species harboring species-specific endosymbiont strains of Buchnera (aphids), Tremblaya and Sodalis (mealybugs), and Serratia (both mealybugs and aphids) despite being farmed by the same ants. This is likely explained by strict vertical transmission of trophobiont endosymbionts between generations. In contrast, the ants’ microbiome is potentially shaped by their social partnerships, with ants that farm the same trophobionts also sharing strains of sugar-processing Acetobacteraceae bacteria, known from other honeydew-feeding ants and which likely reside extracellularly in the ants’ guts. These ant-microbe associations are arguably more ‘open’ and subject to horizontal transmission or social transmission within ant colonies. These findings suggest that the role of social partnerships in shaping a host’s symbiotic microbiome can be variable, and is likely dependent on how the microbes are transmitted across generations