Dr. Xavier Harrison
Institute Research Fellow
- 2013-Present: Research Fellow, Zoological Society of London.
- 2011-2013: BBSRC Postdoctoral Research Associate, University of Exeter.
- 2007-2010: NERC PhD Student, University of Exeter.
- 2006-2007: Research Technician, UKPopNet, University of York.
- 2003-2006: BSc.(Hons) Biology, University of York.
I am interested in genetic traits and ecological processes that drive asymmetries in reproductive success among individuals in wild populations. My work at the Institute of Zoology focuses on the effect of variation in vertebrate immunity genes – Toll-like receptors (TLRs) and the Major Histocompatibility Complex (MHC) – on key fitness traits such as survival and reproduction in a co-operatively breeding bird, the white-browed sparrow weaver (Plocepasser mahali).
My other main areas of research are dispersal ecology and population genetics, using two species with greatly contrasting life histories as model systems: the light-bellied Brent goose (Branta bernicla hrota) – an Arctic nesting migratory bird with one of the longest migration routes of any goose, and the white-browed sparrow weaver, a species with restricted dispersal that defends year-round territories in the Kalahari Desert, South Africa. Details of these projects are below.
In collaboration with Dr Andy Young .
The Sparrow Weaver project has been running since 2007, monitoring the life histories of all members of 35-40 social groups of white-browed sparrow weaver at the Tswalu Kalahari Reserve , South Africa. Sparrow weavers are co-operative breeders, and live in groups of 2-14 birds that comprise a behaviourally dominant breeding pair, as well additional individuals that do not appear to breed but instead help to rear the offspring of the dominant pair. My research focuses on:
- The role of immunogenetic variation in determining performance in a social context, including effects on survival, helper effort and probability of attaining behavioural dominance.
- Patterns of within-group reproductive skew and their implications for the maintenance of sociality.
- The phenotypic and genetic traits that determine the distribution of extra-group paternity among males.
- The influence of individual dispersal decisions on local genetic structure, and the consequences of that structure for mate choice decisions and inbreeding risk.
In collaboration with Professor Stuart Bearhop .
The light-bellied Brent goose is a long-distance migrant, travelling every year from Irish wintering grounds, via staging sites in Iceland, to the Canadian High Arctic to breed. Brent geese are capital breeders, meaning they have to store a large proportion of the resources they need to fuel reproduction as fat prior to migration to the breeding grounds. This can make them susceptible to what are known as “carry-over effects”, where differences in resource access during winter mean some individuals store more fat than others and subsequently have more resources to devote to reproduction the following season. Over the last 10 years, the Irish Brent Goose Research Group (in collaboration with Dr Gudmundur Gudmundsson at the Icelandic Institute of Natural History and Dr Kendrew Colhoun at the Wildfowl & Wetlands Trust) have marked over 3500 geese, and tracked their migrations and patterns of site use at each stage of the flyway. The database of these observations now contains over 95,000 records, and I use these ecological data in conjunction with genetic data to address at the following subjects:
- The role of cultural transmission as a means of learning migratory routes, and its effects on local kin structure, site fidelity and migratory connectivity.
- The role of kin structure in generating inbreeding risk, and quantifying the degree of inbreeding depression resulting from matings between relatives.
- The influence of carry-over effects on individual fitness, and how the strength of carry-over effects can be altered by additional processes, such environmental conditions during breeding.
Harrison XA, Hodgson DJ, Inger R, Colhoun K, Gudmundsson GA, McElwaine G, Tregenza T, Bearhop S (2013) Environmental Conditions During Breeding Modify The Strength of Mass-Dependent Carry-Over Effects in a Migratory Bird. PLOS One 8(10): e77783. doi: 10.1371/journal.pone.0077783
Harrison XA, York JE, Cram DL, Young AJ (2013) Extra-Group Mating Increases Inbreeding Risk in a Cooperatively Breeding Bird. Molecular Ecology 22, 5700-5715.
Harrison XA, York JE, Cram DL, Hares MC, Young AJ (2013) Complete reproductive skew within white-browed sparrow weaver groups despite outbreeding opportunities for subordinates of both sexes. Behavioral Ecology & Sociobiology doi: 10.1007/s00265-013-1599-1
Tyler F, Harrison XA, Veen T, Bretman A, Rodriguez-Munoz R, Tregenza T. (2013) Multiple post-mating barriers to hybridisation in field crickets. Molecular Ecology 22, 1640-1649.
Drewe JA, Weber N, Carter SP, Bearhop S, Harrison XA, Dall SRX, McDonald RA & Delahay RJ (2012) Performance of Proximity Loggers in Recording Intra- and Inter-Species Interactions: A Laboratory and Field-Based Validation Study. PLoS ONE7(6): e39068.
Harrison XA, Bearhop S, Inger R, Colhoun K, Gudmundsson GA, Hodgson DA, McElwaine G & Tregenza T (2011) Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects. Molecular Ecology 20, 4786-4795 doi: 10.1111/j.1365-294X.2011.05283.x
Harrison XA, Blount JD, Inger R, Norris DR & Bearhop S. (2011) Carry-over effects as drivers of fitness differences in animals. Journal of Animal Ecology 80, 4-18.
Harrison XA, Tregenza T, Inger R, Colhoun K, Dawson DA, Gudmundsson GA, Hodgson DJ, Horsburgh GJ, McElwaine G & Bearhop S. (2010) Cultural Inheritance drives site fidelity and migratory connectivity in a long-distance migrant. Molecular Ecology 19, 5484-5496.
Harrison XA, Dawson DA, Horsburgh GJ, Tregenza T & Bearhop S. (2010) Isolation, characterisation and predicted genome locations of Light-bellied Brent goose (Branta bernicla hrota) microsatellite loci (Anatidae, AVES). Conservation Genetics Resources 2, 365-371.
Inger R, Harrison XA, Ruxton GD, Newton J, Colhoun K, Gudmundsson GA, McElwaine G, Pickford M, Hodgson D & Bearhop S (2010) Carry-over effects reveal reproductive costs in a long-distance migrant. Journal of Animal Ecology 79, 974-982.