Cryptic divergent lineages of Pultenaea pauciflora M.B. Scott (Fabaceae: Mirbelieae) exhibit different evolutionary history MELISSA ANN MILLAR* and MARGARET BYRNE Science Division, Department of Environment and Conservation, Bentley Delivery Centre, Locked Bag 104, Bentley, WA 6983, Australia Received 10 September 2012; revised 22 October 2012; accepted for publication 22 October 2012 Genetic structure among disjunct population groups of Pultenaea pauciflora was assessed to determine the evolutionary history of this species as a basis for conservation management strategies. Analysis of individuals from all extant populations using 1737 amplified length polymorphism markers revealed two highly divergent genetic entities with strong geographical structuring. Populations located at Narrogin and Brookton clustered together in Bayesian assignment analysis with every individual optimally placed in a single cluster with complete membership. Genetic differentiation between populations in these two areas was very low. Populations at Boddington were highly divergent from those located at Narrogin and Brookton. All individuals from Bod- dington populations were optimally placed into a second cluster with complete membership. Populations located at Boddington maintain lower levels of allelic diversity, yet greater levels of mean heterozygosity than popu- lations located at Narrogin and Brookton. The degree of genetic differentiation and different patterns of genetic diversity strongly suggest historical divergence and separate evolutionary influences on the two lineages that occur in different ecological habitat. These Evolutionary Significant Units are likely to represent two cryptic sister taxa in the extant populations currently recognized as P. pauciflora, and the reassessment of taxonomic and conservation status of both lineages is required. © 2013 State of Western Australia. Biological Journal of the Linnean Society © 2013 The Linnean Society of London, 2013, 108, 871–881. ADDITIONAL KEYWORDS: conservation genetics – cryptic species – conservation units – evolutionary significant units – fragmentation – genetic diversity. INTRODUCTION For many plant species in fragmented landscapes, a combination of historical processes and more recent anthropogenic impacts have interacted to shape the distribution, degree of population disjunction, and size of extant populations. The degree of genetic differen- tiation among isolated populations and associated reduction in genetic diversity is directly related to the time scale over which evolutionary processes occur, including active selection, mutation, genetic drift, and inbreeding. In general, species with historically iso- lated population distributions are expected to exhibit high levels of genetic differentiation (Templeton et al., 1990; Young, Boyle & Brown, 1996; Thomassen et al., 2011). Although such populations may have experi- enced bottlenecks, persistence through historical cli- matic fluctuations is likely to have preserved genetic diversity. By contrast, species with isolated population distributions arising from more recent, typically anthropogenic, fragmentation events are expected to exhibit lower levels of genetic differentiation among populations and reduced levels of genetic diversity within small populations. The influence of recent anthropogenic impacts confounds inference of past demographic and evolutionary processes, although investigating patterns of genetic differentiation and genetic diversity among and within plant populations can provide some insight into these factors. *Corresponding author. E-mail: melissa.millar@dec.wa.gov.au Biological Journal of the Linnean Society, 2013, 108, 871–881. With 3 figures © 2013 State of Western Australia Biological Journal of the Linnean Society © 2013 The Linnean Society of London, 2013, 108, 871–881 871 Downloaded from https://academic.oup.com/biolinnean/article-abstract/108/4/871/2415586 by guest on 10 June 2020