Microsatellite analysis of genetic population structure of the endangered cyprinid Anaecypris hispanica in Portugal: implications for conservation P. Salgueiro a , G. Carvalho b , M.J. Collares-Pereira a , M.M. Coelho a, * a Centro de Biologia Ambiental/Departamento de Zoologia e Antropologia, Faculdade de Cie ˆncias da Universidade de Lisboa, Campo Grande C2—Piso 3, 1749-016 Lisboa, Portugal b Molecular Ecology and Fisheries Genetics Laboratory, Department of Biological Sciences, University of Hull, UK Received 4 June 2001; received in revised form 2 March 2002; accepted 14 March 2002 Abstract Theendangeredfishspecies Anaecypris hispanica isrestrictedtoeightdisjunctpopulationsinthePortugueseGuadianadrainage. The genetic structure of these populations was studied in order to determine levels of genetic variation within and among popula- tions and suggest implications for conservation of the species. Based on five microsatellite loci, the null hypothesis of population homogeneitywastested.Testsforgeneticdifferentiationrevealedhighlysignificantdifferencesforpairwisecomparisonsbetweenall populations, and substantial overall population subdivision (F ST =0.112). All sampled populations contained unique alleles. Our findings indicate marked genetic structuring and emphasise limited dispersal ability. The high levels of genetic diversity detected within and among A. hispanica populations suggest, however, that the observed fragmentation and reduction in population size of somepopulationsduringthelasttwodecades,hasimpactedlittleonlevelsofgeneticvariability.Dataimplythatmost A. hispanica populationsshouldbemanagedasdistinctunitsandthateachhasahighconservationvaluecontaininguniquegeneticvariation.It is argued that geographic patterns of genetic structuring indicate the existence of eight management units. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Anaecypris hispanica; Conservation genetics; Population structure; Iberian cyprinid; Microsatellites 1. Introduction Anaecypris hispanica (Steindachner, 1866) is a fresh- waterfishspeciesendemictoIberianwaters.Itisasmall cyprinid now confined to the Guadiana River Basin but which, 30 years ago, inhabited rivers across the entire middle and lower Guadiana catchment in Portugal and Spain (Collares-Pereira et al., 1999). It is adapted to severe conditions, especially those arising from flow reduction in dry periods, typical of intermittent river systems in the Mediterranean region. Within rivers, A. hispanica is patchily distributed, preferring small, shal- low, well-oxygenated streams, with aquatic and riparian vegetation, coarse substrate and medium to low flow (Ribeiro et al., 2000). The abundance and geographic range of A. hispanica have contracted progressively since the species was first described by Collares-Pereira and Almac¸a (1979), and its distribution became highly fragmented and restricted to a few isolated areas. As a result, A. hispanica was designated the most endangered primary fish species in Iberian fresh waters (SNPRCN, 1991; Blanco and Gonza´lez, 1992), as indicated by its inclusion in the IUCN Red List (Baillie and Groombridge, 1996), the Bern Convention and EC Habitats directive (see Collares-Pereira et al., 1999, 2000). When a population decline is coupled with fragmen- tation, conservation actions are particularly complex due to the localised reduction in genetic diversity (Car- valho and Cross, 1998). Since it is well established that genetic variation promotes adaptation to changing environmental conditions (Carvalho, 1993), conserva- tion of genetic resources is an essential component of manyspeciesmanagementprogrammes(e.g.Templeton, 0006-3207/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0006-3207(02)00132-5 Biological Conservation 109 (2003) 47–56 www.elsevier.com/locate/biocon * Corresponding author. Tel.: +351-2175-00000; fax: +351-2175- 00028. E-mail address: mmcoelho@fc.ul.pt (M.M. Coelho).