Hybridisation in Antarctic Skuas

Project 1: Hybrid zones offer unique opportunities to obtain insights into processes of speciation. The project is designed to investigate the hybridisation between two long-lived antarctic seabird species, the South Polar Skua (Catharacta maccormicki) and the Brown Skua (Catharacta antarctica lonnbergi).

The molecular genetic AFLP method will be used to allow the objective assignment of each individual to a species or its identification as hybrid. This genetical reference makes the analysis of historic data with respect to hybridisation-related questions possible. We will test whether Haldane's rule (unisexual sterility) is valid in skuas. Reproductive output of pure and mixed-species skua pairs will be measured and together with historic data enables us to decide which of the existing hypotheses best explains the hybrid zone between both skua species.

Knowledge about mate choice is essential for our understanding of hybridisation. The relevance of the bird’s morphology and the voice for mate choice decisions will be studied. This will additionally reveal whether the voice can function as an honest signal representing the individual’s condition among other factors.



Project 2: The project aims to investigate the phylogeography of the southern skua complex by sequencing a hypervariable region of mitochondrial DNA. This marker contains enough informative variation to resolve population differences and is established in Skuas.

DNA samples of 25-30 individuals per breeding location will be provided from co-operating scientists and will cover the breeding range of all taxa. The analysis will reveal the phylogeny and age of the five taxa as well as population history and potential range changes. The prediction that climatic oscillations do stronger reduce the phylogeographical structure of high latitude taxa will be tested by comparing populations of (antarctic) South Polar Skua and Sub-antarctic Skua.

The project offers the opportunity to compare speciation in arctic gulls and antarctic Skuas and will reveal the importance of glaciation on population genetic structure and past speciation events.

Scientists

Dr. Hans-Ulrich Peter
Polar & Bird Ecology Group
Institute of Ecology
Friedrich-Schiller-University

Dr. Markus Ritz
Polar & Bird Ecology Group
Institute of Ecology
Friedrich-Schiller-University

Research areas

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Publications

Ritz, M.S. (2007). Sex-specific mass loss in chick-rearing South Polar Skuas (Stercorarius maccormicki) - Stress induced or adaptive? Ibis 149: 156-165.

Votier S.C., Kennedy, M., Bearhop, S., Newell, R.G., Griffiths, K., Whitaker, H., Ritz, M.S., Furness, R.W. (2007) DNA from birds occurring in Europe fails to discriminate between southern hemisphere skua species. Ibis 149 (3): 619-621.

Hahn, S., K. Reinhardt, M. S. Ritz, T. Janicke, D. Montalti and H.-U. Peter. (2007). Oceanographic and climatic factors differentially affect reproduction performance of Antarctic skuas. Marine Ecology Progress Series 334: 287-297.

Ritz, M.S., Hahn, S., Janicke, T. & Peter, H.-U. (2006): Hybridisation between South polar skua (Catharacta maccormicki) and Brown skua (C. antarctica lonnbergi) in the Antarctic Peninsula region. Polar Biology 29 (3): 153-159.

Ritz, M.S., Hahn, S. & Peter, H.-U. (2005): Factors affecting chick growth in the South Polar Skua (Catharacta maccormicki): food supply, weather and hatching date. Polar Biology 29 (1): 53-60.

Hahn, S., Peter, H.-U. & Bauer, S. (2005): Skuas at penguin carcass: patch use and state-dependent leaving decisions in a top-predator. Proc. Roy. Soc. Lond.B 272 (1571): 1449-1454.

Votier, S. C., Furness, R. W., Bearhop, S., Crane, J. E., Caldow, R. W. G., Catry, P., Ensor, K., Hamer, K. C., Hudson, A. V., Kalmbach, E., Klomp, N. I., Pfeiffer, S., Phillips, R. A., Prieto, I. and Thompson, D. R. (2004): Changes in fisheries discard rates and seabird communities. Nature 427: 727-730.

Hahn, S., Peter, H.-U. (2003): Sex and age dependency of wing patch size in Brown Skuas. Emu 103 (1): 37-41.

Hahn, S., Peter, H.-U. (2003): Feeding territoriality and the reproductive consequences in brown skuas Catharacta antarctica lonnbergi. Polar Biology 26: 552-559.

Hahn, S., Ritz, M.S. & H.-U. Peter (2003): Living in mixed pairs- better for fitness ? A study in skuas. In: Antarctic Biology in a Global Context, pp.229-233.

Homepage

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Research funding organisation

German Research Foundation

Project number: PE 454/13
Funding period: 2003 - 2005