Population Genetics
Population structure and demographic history are key factors in understanding the ecology and evolutionary history of species. Estimating gene flow between populations has implications for assessing the status of species and can provide critical insight for management. Many species of seabirds exhibit high degrees of colony fidelity which may result in highly structured populations. Seabird species that have multiple population-specific non-breeding areas tend to exhibit phylogeographic structure while those that remain resident near breeding colonies exhibit population genetic structure
For the crested penguins of New Zealand, we currently know relatively little about their population structure and demography. Some, like the tawaki, breed across relatively large ranges of coastline with small colonies scattered throughout. Others, like the erect-crested penguin, are found only in one or two locations during the breeding season and form large colonies on remote island groups. However with both of these species, very little is known about gene flow between colonies and juvenile recruitment. My interests lie in understanding how the gene flow and population structure are impacted by breeding and non-breeding distribution. Ultimately, I hope that this information will indicate the connectivity of the populations as a whole and provide much needed information for management.
Gene flow and juvenile recruitment among fjords in Fiordland tawaki
Tawaki occupy an extensive range along the south-western coast of New Zealand's South Island. The core of this range is the deeply indented fjord complexes of the Fiordland region. Each of the 14 fjords is likely home to breeding colonies of tawaki hiding in the dense coastal rainforest in rockfalls, caves, and tree roots. Research by the Tawaki Project has shown that location of the colony within the fjord (i.e. near the head vs. near the mouth) has a significant impact on whether tawaki forage within the fjord or off shore in the Tasman Sea. But whether or not colony location impacts gene flow within or between fjords is not known.
This project aims to estimate the genetic connectivity of the Fiordland tawaki population through partial genome sequencing using ddRad-Seq methods. In addition to a population-wide assessment of gene flow, I will also investigate juvenile recruitment to determine if juveniles return to their natal colonies or fjords to breed.
Field work for this project is complete with samples taken from breeding tawaki across Fiordland. Sample analysis is slated for August 2023 at the University of Texas at El Paso.
Conservation genetics of two declining sub-Antarctic penguin species
New Zealand's sub-Antarctic penguin species are significantly less studied than their mainland counterparts. In fact, the erect-crested penguin is cited as the least studied species of penguin in the world (a title formerly held by the tawaki). While very little is known about the erect-crested penguin, we do know that they appear to be declining in at least one of their two known breeding locations (Antipodes Island). Unfortunately, the sympatric Eastern rockhopper penguin may be facing even steeper declines.
This project aims to understand gene flow and demography in these two species across their New Zealand range through partial genome sequencing using ddRad-Seq methods. For erect-crested penguins, I have sampled breeding adults from the entire breeding range - Antipodes Island (declining population) & Bounty Islands (stable population?). For Eastern rockhoppers, I have sampled at Antipodes Island and will add the Auckland Islands and Campbell Island to the data set this season.
The first season of field work is complete with the goal of a second season December 2023.
The results of the above two projects have been combined and are currently being reviewed for publication in PLOS One.
White, J., Lavretsky, P., Garcia-Borboroglu, P., Ellenberg, U., Houston, D., Long, R., Mattern, T., Mays, H.L., Pütz, K., Seddon, P., & McCracken, K.G. (in review). Genetic connectivity and conservation: The diverging fates of New Zealand’s crested penguins.