Tali Reiner Brodetzki

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Insect societies headed by multiple queens (polygyny) raise evolutionary questions, such as how does genetic heterogeneity among colony members affect in‐nest interactions; or, are all queens equally reproductive or equally treated by workers? Answering such questions requires intensive and continuous observations of in‐nest behavior. Here, we addressed these questions in the polygyne supercolonial ant,Cataglyphis niger,using a barcoding system that enables the tracking of individual interactions, together with polymorphic DNA microsatellite markers that indicate the matriline and patriline of all individuals. Our findings that both queens and workers have low interrelatedness corroborate earlier reports regarding the supercolony structure ofC. niger. Ovary inspection and worker genotyping revealed that all the queens contribute similarly to nest demography. Tracking positions of individual workers through time revealed that only a small proportion of them are constantly engaged in tending the queens and can be considered as retinue workers. However, genotyping these workers and the attended queens revealed no relationship to genetic relatedness, again typical of a true polygyne and supercolonial species. Unlike invasive supercolonial species,C. nigeris native to Israel, enabling us to address questions regarding the driving forces, other than kin selection, that stabilize this society.

In social insects, due to considerable polyphenism as well as high level of hybridization, the delimitation of species can be challenging. The genus Cataglyphis presents a high level of diversification, making it an excellent model with which to study evolutionary paths. Israel appears to be a “hot spot” for recent speciation in this genus. Although previous studies have described multiple species of Cataglyphis in Israel, a recent genetic study has questioned the existence of some of these historically described species. The present study focuses on an apparent species complex, the C. niger species complex which includes C. niger, C. savigyi, and C. drusus that are distinguishable by their mitochondrial DNA (and therefore named mitotypes) but not by their nuclear DNA. Using a multi-method approach (genetics, chemistry and behavior), we show that these mitotypes also differ in their social structures and are readily distinguishable by their cuticular hydrocarbons profiles. While most populations of the different mitotypes are allopatric, at our study site they are sympatric, but nonetheless maintain the observed differences between them. This raises the evolutionary question: Are these incipient species that have diverged with gene flow, or is this a case of social and chemical polymorphism that is maintained within a single species? Unveiling the interplay between social polyphenism and species segregation is at the core of evolutionary biology.

Species are the fundamental units upon which evolutionary research is based. In insects, due to the high level of hybridization, the delimitation of such species can be challenging. The genus Cataglyphis presents a high level of diversification, making it an excellent model with which to study evolutionary paths. Israel appears to be a 'hot spot' for recent speciation in this genus. Although previous studies have described multiple species of Cataglyphis in Israel, a recent genetic study has questioned the existence of some of these historically described species. The present study focuses on an apparent species complex that is distinguishable by its mitochondrial DNA (and therefore named mitotypes) but not by its nuclear DNA. Using a multi-method approach (genetics, chemistry and behavior), we show that these mitotypes also differ in their social structures and are readily distinguishable by their cuticular hydrocarbons profiles. While the different mitotypes are in general allopatric, at our study site they all coexist but nonetheless maintain the observed differences between them. This raises many evolutionary questions: Are these incipient species that have diverged with gene flow, or is this a case of social and chemical polymorphism that is maintained within a single species.

The remarkable diversity of ant social organization is reflected in both their life history and population kin structure. Different species demonstrate a high variation with respect to both social structure and mating strategies: from the ancestral colony type that is composed of a single queen (monogyny), singly inseminated (monoandry), to the more derived states of colonies headed by a multiply inseminated queen (polyandry), to colonies composed of multiple queens (polygyny) that are either singly or multiply inseminated. Moreover, the population structure of an ant species can range from multicoloniality to polydomy to supercoloniality, andCataglyphisis considered to be a model genus in regard to such diversity. The present study sought to determine the social and population structure of the recently describedC. israelensisspecies in Israel. For this purpose we employed a multidisciplinary approach, rather than the commonly used single approach that is mostly based on genetics. Our study encompassed behavior (nest insularity/openness), chemistry (composition of nestmate recognition signals and cuticular hydrocarbons), and genetics (microsatellite polymorphism). Each approach has been shown to possess both advantages and disadvantages, depending on the studied species. Our findings reveal thatC. israelensiscolonies are headed by a single, multiply inseminated queen and that the population structure is polydomous, with each colony comprising one main nest and several additional satellite nests. Moreover, our findings demonstrate that none of the above‐noted approaches, when employed individually, is suitable or sufficient in itself for delineating population structure, thus emphasizing the importance of using multiple approaches when assessing such complex systems.

The basic ant colony is presumed to have evolved through kin selection. However, ants show a remarkable diversity in their social organization, from a monogynous-monandrous queen to the more derived states of polygyny with polyandrous queens. The existence of polygyny is an evolutionary enigma, since kin selection theory predicts that while queens should strive for reproductive monopoly, workers are predicted to favor their own matriline in rearing gynes. Using a barcoding system that enables tracking of individual interactions, along with polymorphic DNA microsatellite markers that indicate the matriline and patriline of all individuals, we demonstrate the complex social interactions in polygyne nests of Cataglyphis niger . C. niger is not only polygyne but also constitutes a supercolony at the study site. Our pioneering findings that both queens and workers are not necessarily related to each other support the supercolony structure of the population. Also in line with supercoloniality, we demonstrate that the workers contribute equally to the nest production and rearing of the queens. Unlike invasive supercolonial species, C. niger is native to Israel, raising questions about the driving forces, apart from kin selection, that stabilize this society.