Final year PhD student interested in phylogenetics, hybridisation and macroevolution.
Email: kk443 [AT] cam.ac.uk
Plain English: I am interested in the origins of the amazing modern biodiversity, in particular tropical butterflies. I specialise in phylogenetics – the use of DNA data to reconstruct how different organisms are related (“The Tree of Life”), when they diversified and how fast they evolve. I also apply similar techniques to ask questions about specific genes involved in butterfly adaptation to the natural environment.
1. Phylogeny of Heliconiini
The Neotropical butterfly tribe Heliconiini is notorious for instances of hybrid speciation and widespread gene flow, which may obscure the phylogenetic signal of speciation. I combined Sanger sequencing, historical DNA techniques and de novo assembly of Illumina data to sample 20 nuclear loci and whole mitochondrial genomes from Heliconiini and allies. As expected from natural history, the loci show high incongruence. Philosophically different approaches to building the phylogeny (concatenation and multispecies coalescent) yield very similar topologies, but with differing emphasis on the underlying conflict on the data.
2. Diversification of Heliconiini
Heliconiini may have undergone rapid diversification in the periods of environmental change in the Amazon and Andes. Furthermore, complex interactions in the Muellerian mimicry rings could lead to a positive diversity dependence between the number of species and the rate of speciation. Bayesian analyses demonstrate that Heliconiini appear younger than previously thought and that the most speciose lineage Heliconius has indeed undergone a large increase in diversification rates.
3. Butterfly-plant coevolution
Heliconiini feed obligatorily on the toxic tropical Passiflora plants. I developed the most comprehensive phylogeny of Passifloraceae to date and used it to analyse the coevolution of the two clades. Host-parasite models detect a very strong signal of coevolution. Close to a half of modern dietary preferences of the butterflies are due to evolutionary conservatism.
4. Hybridisation in Heliconius hermathena
The wing patterns of the Brazilian Heliconius hermathena suggest it originated by hybridisation of H. erato and H. charithonia. To investigate this possibility, I developed a whole genome phylogeny of the H. erato clade and analysed the history of individual colour pattern loci. This project was a collaboration with Owen McMillan, supported by a Graduate Fellowship at the Smithsonian Tropical Research Institute in Panama.
5. Hybridisation across Heliconius
I have extended my work on H. hermathena to include nearly all species in the genus into a genome-wide phylogeny, and identify genomic signatures of introgression. Hybridisation is especially prevalent in the H. melpomene/cydno clade and somewhat important in the Silvaniforms. The bewildering amount of conflicting phylogenomic signals in other clades is a product of incomplete lineage sorting during rapid speciation.
I have also contributed to collaborative projects on receptor family evolution (with Adriana Briscoe, UCI), gene duplication (Laura Ferguson, Oxford) and Heliconius demography (Simon Martin, Cambridge).
Throughout my PhD I enjoyed a range of teaching activities from high school to graduate level. I am also interested in tropical conservation and natural history. Prior to research at Cambridge, I studied the biogeography of Peromyscus maniculatus mice with Hopi Hoekstra and took part in various field projects in Central America, the Caribbean and South Africa.
- 2011-present, PhD candidate, Department of Zoology, University of Cambridge
- 2010-2011, MPhil, Department of Zoology, University of Cambridge
- 2006-2010, BA (cum laude), Organismic and Evolutionary Biology, Harvard University
- 2004-2006, Czartoryski Scholar, Dulwich College, London
Data for Kozak et al. 2015 (Heliconiini phylogeny):
Template tree: Heliconiini_chronogram_Kozak_etal_2015
All trees and alignments: http://treebase.org/treebase-web/search/study/summary.html?id=15531