Profile of Alexandra Tyers
General Research Theme & Interests:
Broadly my research encompasses topics in evolutionary biology and behavioural ecology, with a main focus on the roles of ecological and sexual selection in adaptive radiation and speciation. I am also interested in convergent evolution, phenotypic plasticity and individual variation in behaviour.
The majority of the cichlid fish species found in the East African Rift Valley belong to the haplochromini tribe. These fish are found in many of the river systems throughout East Africa, but it is due to their rapid adaptive radiation and explosive speciation within the Great Lakes, particularly Malawi and Victoria, that has led to their frequent use as a model system in evolutionary biology. Among the hundreds of endemic species found within each lake there are eco-morphological and behavioural adaptations to suit all habitats and available food sources. Many closely related cichlid species are reproductively isolated by mate choice and territorial males tend to be more aggressive to similar-coloured males, facilitating coexistence of divergent colour morphs or species. The beautiful diversity of colour within and among sympatric species and geographic populations makes these not only a very useful, but also very charismatic, group of organisms with which to test theories of vertebrate evolution and speciation
Current Research*: Genomic basis of adaptive divergence and speciation
Current research projects combine full-genome sequencing with ecological field work, morphological investigations and aquarium based behavioural experiment to investigate mechanisms of sympatric and allopatric divergence, and morphological and behavioural variation and phenotypic plasticity in species which are prone to rapid speciation.
We are carrying out detailed investigations of basal species in the early stages of sympatric speciation in small isolated crater lakes in Southern Tanzania, and also making large scale collections of the diversity of the Lake Malawi cichlid radiation (500-100 species), with the aim of building a scientific resource consisting of genome sequence and phenotype data of one of the largest adaptive radiations of vertebrates ever known. Specimens representing the diversity of form are also available for use in public displays at the Cambridge University Zoological Museum.
* in collaboration with researchers at Bristol University (Dr Martin Genner), the University of Cambridge (Dr Eric Miska, Dr Richard Durbin), and the Tanzanian Fisheries Research Institute.
Individual differences in female mate preference
Mate preferences are a major force in the process of speciation. Not only does the development of assortative mating reduce gene flow between diverging taxa and provide pre-zygotic reproductive isolation between closely related species without the need for geographical or ecological separation, consistent individual variation in preference within a population has the potential to influence evolution by sexual selection. Because of its potential to drive evolutionary change, I have developed and interest in the nature of individual variation in behaviour, which is often overlooked in population level studies of mate preference.
The maintenance of rare morph colour polymorphism in Lake Malawi haplochromine cichlids
Blotch polychromatism is widespread among East African cichlids and recent laboratory based behavioural experiments suggest that intrasexual aggression may be a major contributing factor to it's maintenance: lack of recognition of rare morphs by conspecifics may result in an advantage through reduced aggression. We investigate these issues in the polychromatic Lake Malawi cichlid fish, Pseudotropheus callainos, using laboratory behavioural choice trials and field observations.
PhD thesis: Divergence and speciation of Lake Malawi haplochromine cichlid fish from non-rocky habitats.
Much of the exceptional diversity of lacustrine cichlids can be explained by geographic variation among isolated populations of the rocky-shore habitat specialists. However, there are also many other types of habitat specialists, which have received much less attention. The main focus of my thesis research was to compare patterns of assortative mating among taxa from different habitats with different degrees of population structuring, by investigating divergence and reproductive isolation among allopatric populations of non-rock restricted taxa in the Lake Malawi catchment.
- Tinghitella MH, Lackey AR, Martin M, Djikstra P, Drury JP, Heathcote R, Keagy J, Scordato ESC & Tyers AM. Accepted. The role of male competition in speciation: A review and research agenda. In press. Behavioral Ecology.
- Verheyen E (on behalf of the Cichlid Science 2015 meeting & concerned scientists). 2016. Oil extraction imperils Africa’s Great Lakes. Science. 354: 561-562.
- Malinsky M, Challis R, Tyers AM, Schiffels S, Terai Y, Ngatunga BP, Miska E, Durbin R, Genner M & Turner GF. 2015. Genomic Islands of speciation separate cichlid ecomorphs in an East African crater lake. Science. 350: 1493-1498.
- Tonkins B, Tyers AM & Cooke GM. 2015. Cuttlefish in captivity: an investigation in housing and husbandry for improving welfare. Applied Animal Behaviour Science. 168: 77-83.
- Tyers AM, Bavin D, Cooke GM, Griggs C & Turner GF. 2014. Peripheral isolate speciation of a Lake Malawi cichlid fish from shallow-muddy habitats. Evolutionary Biology. 41: 439-451.
- Tyers AM & Turner GF. 2013. Signal and preference divergence among populations of the non-endemic basal Lake Malawi cichlid fish Astatotilapia calliptera (Perciformes: Cichlidae). Biological Journal of the Linnean Society. 110: 180-188.
- Shechonge A, Ngatunga B, Bradbeer S, Day J, Ford A, Kihedu J, Mzighani S, Smith A, Sweke E, Tamatamah R, Tyers A, Turner G & Genner M. Submitted. Widespread colonisation of Tanzanian catchments by introduced Oreochromis tilapia fishes: the legacy from decades of deliberate introduction.
- Tyers AM, Cooke GM & Turner GF. Submitted. Rare morph Lake Malawi mbuna cichlids may benefit from reduced aggression from conspecifics and closely related heterospecifics.
- Malinsky M, Svardal H, Tyers AM, Miska EA, Genner MJ, Turner GF & Durbin R. In prep. Whole genome sequences of Malawi cichlids reveal multiple radiations interconnected by gene flow. Available on bioRvix.
- Tyers AM, Wilson I, Ngatunga BP, Genner MJ & Turner GF. In prep. Phenotypic differentiation, morphological plasticity and allopatric speciation in Tanzanian crater lake cichlids.
- Tyers AM, Wilson I & Turner GF. In Prep. Genome-wide analysis of the evolution of new species of cichlid fish.
- Tyers AM, Jones KA & Cooke GM. Reactors and thinkers: Individual differences in plasticity limits behavioral responses across contexts in cuttlefish (Sepia officianalis).
Click here to view Alexandra's CV.