Genetic principles for freshwater restoration in New Zealand

Abstract

Habitat fragmentation and destruction can lead to loss of genetic diversity within and among populations. One goal of restoration proj ects is to minimise loss of genetic diversity and to preserve genetic structure. Restoration may involve the release of wild‐caught or hatchery‐produced individuals to re‐establish or augment populations, and targets species with weak dispersal potential. Key criteria to consider in restoration projects are genetic divergence among the source populations and the number of individuals to transfer. Molecular tools provide quick and simple tools for assessing genetic diversity, but most markers are selectively neutral and should be supplemented with data on life‐history traits. The effective size of the population, N_e , can be considerably smaller than the census N. Low numbers of founders will lead to a loss of genetic diversity, whereas subsequent breeding between closely related individuals will lead to inbreeding depression. Outbreeding depression can occur when offspring are produced from crosses between individuals from divergent populations, leading to the breakdown of co‐adapted gene complexes. Both inbreeding and outbreeding depression can lead to declines in fitness, and these effects may take several generations to become evident.

Keywords:

• effective population size
• outbreeding and inbreeding depression
• genetic restoration