Ecological and genetic basis of 'gigantism' in an island bird: an empirical test of new marker-based approaches

EVOLUTIONARY GENETICS of island birds: a Case Study Using Silvereyes (ZOSTEROPIDAE, AVES)

Observations of island bird life have been the source of many ideas in evolutionary biology. A pattern observed in many passerine birds is a trend towards gigantism subsequent to colonization of island environments. This classic pattern of increased body size is seen very clearly in the white-eye (Zosteropidae) family. One group of species and subspecies in this family, the Zosterops lateralis complex, provides an ideal test case for theories attempting to explain this increase in size. Previous research suggests that the reason for this size change is due to adaptation to selective pressure rather than genetic drift. We are currently investigating the genetic basis of this morphological change in silvereyes. We are using both traditional and newer, molecular marker-based methods of investigating quantitative inheritance in a particular silvereye population, the Capricorn silvereye (Zosterops lateralis chlorocephalus). To this extent we have identified over 20 polymorphic markers for this species. Nineteen were selected to create a fluorescent marker set which consists of 4 published silvereye loci (Degnan et al 1999), 7 new silvereye loci (Frentui et al in prep), 7 Seychelles warbler loci (Richadson et al 2000) and a swallow locus (Primmer et al 1995). We are currently genotyping the whole population of silvereyes with this set of loci.

MOLECULAR-MARKER ASSISTED QUANTITATIVE GENETICS

As part of the larger silvereye project, we are currently genotyping 900 individuals with the fluorescent microsatellite marker set to investigate quantitative inheritance. Newer methods rely on using molecular markers to estimate relatedness, which will then be used in comparisons of phenotypic similarity among relatives (Ritland, 1996). We are using traditional cross-fostering methods to test the usefulness of these molecular methods in this population. It is hoped this will enable future research into the genetic basis of evolution in other Zosterops species.

The lab work involves:

  • Development of a Capricorn silvereye (Zosterops lateralis chlorocephala) microsatellite marker library to obtain between more polymorphic loci.
  • Testing other published bird microsatellite loci for cross-utility in Capricorn silvereye (Zosterops lateralis chlorocephala).
  • Optimisation of the loci developed and combination into a fluorescent marker set.
  • Genotyping of all sampled birds at 19 loci (approimately 900 birds) using an upgraded Applied Biosystems 377 automated sequencer.

Personnel

Francesca Frentiu (2002)
John Chittock (2002-2003)

Associated Publications

Frentiu FD, Lange CL, Burke T, Owens IP (2003) Isolation of microsatellite loci in the Caprocorn silvereye, Zosterops laterils chlorocephalus (Aves: Zosteropidae). Molecular Ecology Notes, 3 (3). pp. 462-464. ISSN 1471-8278

Frentiu FD PhD Thesis (2004) Adaptive morphological evolution in an island bird (Zosterops lateralis chlorocephalus) : a quantitative genetic approach. The University of Queensland

Degnan SM, Robertson BC, Clegg SM, Moritz CC (1999) Microsatellite primers for studies of gene flow and mating systems in white-eyes (Zosterops) Molecular Ecology, 8 (1), 159-160.

Collaborators

Dr Ian Owens (i.owens@ic.ac.uk), Imperial College at Silwood Park, London.
Dr Sonya Clegg, Imperial College, London.
Francesca Frentiu, Department of Zoology and Entomology, University of Queensland, St Lucia, Brisbane, Australia.

This project is a collaboration between Professor Terry Burke and Dr Ian Owens of the Imperial College, London.

Also see 

Morphological shifts in island-dwelling birds: the roles of generalist foraging and niche expansion
             
This project was funded by the Natural Environment Research Council (http://www.nerc.ac.uk/.