Katrin Kellner Research
Evolution of mating systems in social insects: Consequences on conflict and cooperation in group life
My research employs social insects as model systems to understand the evolution of mating systems and their impact on societies. Ants are nearly ubiquitous in warm temperate and tropical ecosystems and their success can be attributed to employing a broad variety of mating strategies: single or multiple queens, single or multiply mated, male and/or female parthenogenesis (arrhenotoky and thelytoky) – and often some species employ combinations of all of the above!
My research generally involves aspects of population genetics, evolutionary genetics, and microbial ecology to understand the evolutionary ecology of social insects.
Major Research Areas:
Population genetics: From unrelated individuals to perfect clones
Relatedness has a central to our understanding of the evolution and maintenance of animal societies--animal societies are often extended families of some sort. Much of my research focuses on ants in the subfamily Ponerinae and relies extensively on genetic fingerprinting methods (microsatellites, mtDNA, etc.). Ponerine ants are considered to be phylogenetically old and have a number of traits that the first ants possessed.
Part of my research investigates ants in the genus Pachycondyla. These ants are widely distributed in the tropics, and exhibit a variety of mating strategies. For example, Pachycondyla inversa and P. villosa are facultative polygynous, meaning that queens can found new nest either alone or together with other queens. Interestingly, queens can either be singly or multiply mated. Thus a single colony may be genetically heterogeneous due to multiple queens or multiply mated queens, which was a finding that contradicted theoretical predictions that polygyne and polyandry exclude each other. In fact, colonies of P. inversa and villosa have an average within-colony relatedness of 0, which means that these colonies consist of completely unrelated individuals. Ongoing areas of research include comparisons with Pachycondyla species in Texas.
In contrast, our understanding of another Ponerine, Platythyrea punctata is strikingly different. These colonies consist of genetically identical clones because workers in this species can reproduce unisexually, i.e, females are unmated but can lay diploid eggs without the use of sperm. This results in colonies having an average relatedness of 1, which is the complete opposite case as Pachycondyla. This clonal species seems to easily colonize new habitats. For example, this species has spread throughout the West Indies from Central America within the last 100,000 years. Current research is addressing whether colonies exhibit inbreeding depression or other consequences of low mating frequency or unsexuality.Behavioral Ecology: Conflict and conflict resolution
Animal cooperative systems such as those exhibited by social insects can be destabilized by exploitation and cheating. Outside of extreme cases illustrated above, social insect colonies consist neither of genetically identical clones nor of unrelated individuals. Due to the haplodiploid sex determinations of Hymenoptera (females are diploid, males are haploid), not all individuals in a colony are equally related. Therefore conflicts are expected, e.g. about who produces females and males and about queen: worker ratio. Though mechanisms are not completely understood, social insects have evolved strategies to resolve conflicts and ensure the maintenance of group homeostasis. One of these mechanisms under investigation is so-called “policing” where workers prevent each other from laying eggs in the presence of a fertile queen. This area of research involves behavioral observations, experimentation, DNA fingerprinting and social network analysis. Model systems include the unisexual ants Platythyrea punctata and Mycocepurus smithii (see below) but also other ants I find interesting.
Evolutionary Genetics and Microbial Ecology: Holobionts
This topic addresses microbial influences on ant behavior and their evolutionary ecology. This area uses the fungus-gardening ant Mycocepurus smithii as the main experimental system. M. smithii is unique among fungus-gardening ants because it is also unisexual like P. punctata discussed above. However, this species is a fungus-gardening ant, which cultivates fungus as its sole food source. Due to the lack of sexual recombination, ant genotypes are genetically distinct lineages, as well as the fungal strains of the asexually proliferated fungus. Using microsatellite markers and phylogenetic techniques I study the coevolution and short term and long term fitness consequences of manipulating ant-fungus combinations. In addition, using bacterial-16s 454-pyrosequencing I am studying microbial communities associated with this ant species.
The Attine ant Mycocepurus smithii is unique among the Attines because males are missing and females are produced by thelytokous parthenogenesis. Other areas of investigation include the use of Mycocepurus smithii as a system to address topics listed above.
Kellner, K. H. Fernández-Marín, HD Ishak, R Sen, TA Linksvayer & UG Mueller (in minor revision) Frequent cultivar substitution limits co-evolutionary potential of ant-fungus associations in the asexual fungus-farming ant Mycocepurus smithii. Journal of Evolutionary Biology
Seal JN, Kellner K, Fiesel P, Heinze J (in revision) Dispersal barriers and reduced gene flow in a parthenogenic ant in the Mesoamerican Biological Corridor.
Kellner K, JN. Seal & J Heinze (2012) Sex at the margins: parthenogenesis vs. facultative and obligate sex in a Neotropical ant, Journal of Evolutionary Biology, 26:108-117
Jon N Seal, K Kellner, A Trindl & J Heinze (2011) Phylogeography of the parthenogenic ant Platythyrea punctata: highly successful colonization of the West Indies by a poor disperser, Journal of Biogeography, 38, 868-882.
Kellner K, Heinze J (2011) Absence of Nepotism in Genetically Heterogeneous Colonies of a Clonal Ant, Ethology, 117, 556–564
Ishak, HD, R Plowes, R Sen, K Kellner, E Meyer, D A Estrada, S E Dowd & U G Mueller (2011)Bacterial Diversity inSolenopsis invicta and Solenopsis geminata Ant Colonies Characterized by 16S amplicon 454 Pyrosequencing. Microbial Ecology, 61, 821-831.
Kellner K, Heinze J (2011) Mechanism of facultative parthenogenesis in the ant Platythyrea punctata. Evolutionary Ecology, 25, 77-89.
Barth, B, K. Kellner and J. Heinze (2010) The police are not the army: context-dependent aggressiveness in a clonal ant. Biology Letters, 6, 329-332.
Brunner, E., K. Kellner and J. Heinze (2009) “Policing and dominance behavior in the parthenogenetic ant Platythyrea punctata“ Animal Behavior, 78, 1427-1431
K. Kellner, B. Barth and J. Heinze (2009) “Colony fusion causes within-colony variation in a clonal ant”, Behavioral Ecology and Sociobiology, 64, 737-746
K. Kellner, A. Trindl, J. Heinze and P. D'Ettorre (2007) “Polygyny and polyandry in small insect societies” Molecular Ecology, 16, 2363-2369.
P. D'Ettorre, K. Kellner, J. H. C. Delabie and J. Heinze (2005) “Number of queens in founding associations of the ponerine ant Pachycondyla villosa.” Insectes Sociaux, 52, 327-332.