Impact of population bottlenecks on genetic variation and the importance of life-history; a case study of the northern elephant seal

This paper reviews some of the important factors related to the impact of p opulation bottlenecks, using the northern elephant seal (Mirounga angustiro strus) as a case study for illustration. The northern elephant seal was hun ted extensively in the 19th century and forced through a bottleneck of appr oximately 10-20 seals. All measures of molecular genetic variation show cur rent levels for the northern elephant seal to be low. Levels of generic var iation were compared with expectations based on a simulation model that rec apitulates demographic growth, based on age-specific data oil reproduction and mortality. Predictions from the simulation model are then presented to illustrate the importance of differences in life-history strategy and skewe d reproductive success. Either high reproductive skew (e.g. polygyny) or a low growth rate in a population can increase the impact of a bottleneck on molecular variation. Severe population bottlenecks can also disrupt aspects of developmental stability and thereby increase the fluctuating asymmetry and variability of quantitative traits. A comparison of skulls collected be fore and after the bottleneck showed this to have occurred for some elephan t seal quantitative characters. (C) 1999 The Linnean Society of London.