tailieunhanh - Freeland - Molecular Ecology (Wiley, 2005) - Chapter 3

3 Genetic Analysis of Single Populations Why Study Single Populations? Now that we know how molecular markers can provide us with an almost endless supply of genetic data, we need to know how these data can be used to address specific ecological questions. | 3 Genetic Analysis of Single Populations Why Study Single Populations Now that we know how molecular markers can provide us with an almost endless supply of genetic data we need to know how these data can be used to address specific ecological questions. A logical starting point for this is an exploration of the genetic analyses of single populations which will be the subject of this chapter. We will then build on this in Chapter 4 when we start to look at ways to analyse the genetic relationships among multiple populations. This division between single and multiple populations is somewhat artificial as there are very few populations that exist in isolation. Nevertheless in this chapter we shall be treating populations as if they are indeed isolated entities an approach that can be justified in two ways. First research programmes are often concerned with single populations for example conservation biologists may be interested in the long-term viability of a particular population or forestry workers may be concerned with the genetic diversity of an introduced pest population. Second we have to be able to characterize single populations before we can start to compare multiple populations. But before we start investigating the genetics of populations we need to review what exactly we mean by a population. What is a population A population is generally defined as a potentially interbreeding group of individuals that belong to the same species and live within a restricted geographical area. In theory this definition may seem fairly straightforward at least for sexually reproducing species but in practice there are a number of reasons why Molecular Ecology Joanna Freeland 2005 John Wiley Sons Ltd. 64 GENETIC ANALYSIS OF SINGLE POPULATIONS Figure A pair of copulating common green darner dragonflies Anax junius . Juvenile development in this species is phenotypically plastic depending on the temperature and photoperiod during the egg and larval stages. Photograph .