Historical and biological determinants of genetic diversity in the highly endemic triploid sea lavender Limonium dufourii (Plumbaginaceae)

Abstract

Microsatellite markers were used to evaluate the genetic diversity and population genetic structure in the critically endangered Limonium dufourii (Plumbaginaceae), a highly endemic triploid species from the coasts of eastern Spain. Sixty-five alleles from 13 microsatellite regions were amplified in a sample of 122 individuals collected from the six extant populations. Microsatellite patterns were consistent with the triploid nature of L. dufourii. Alleles were unambiguously assigned to two different parental subgenomes in this hybrid species and the greater contribution of the diploid parental subgenome was confirmed. Eleven, 25 and 26 multilocus genotypes were recorded from the haploid, diploid and from the combined information of both subgenomes, respectively. Genetic diversity was mostly distributed among populations (72.06% of the total genetic variation). Genotypes from Marjal del Moro populations grouped into two highly structured clusters (88.41% of the total variance). The observed patterns of distribution of genetic diversity are interpreted to result from multiple hybridization events and isolation between populations. Threats to this species are mainly anthropogenic (urbanization and tourism pressure), although stochastic risks cannot be ignored. Therefore, in order to preserve extant genetic variation of L. dufourii, in situ strategies such as the preservation of its habitat are a high priority. Several recommendations in order to assist ex situ measures to guarantee the success of conservation strategies and maintain the relationships between individuals and populations are proposed.

Polyploid origin, genetic diversity and population structure in the tetraploid sea lavender Limonium narbonense Miller (Plumbaginaceae) from eastern Spain

“…Poor microsatellite transferability results also support the large phylogenetic distance from these two to other Limonium species (Palop et al 2000). Therefore, if other unrelated Limonium species would have been involved in the origin of L. narbonense, microsatellite amplification patterns should have revealed a high proportion of null alleles, due to the amplification of only one subgenome (Palop-Esteban et al 2007); fixed banding profiles, due to the absence of recombination between heterologous chromosome pairs; or absence of allele variability in one or both subgenomes (Palop-Esteban et al 2007). None of these patterns was observed in the electropherograms of L. narbonense (Fig.…”

“…Therefore, genetic diversity in Limonium may be conditioned not only by extrinsic factors, such as distribution ranges, but also by intrinsic factors such as ploidy levels and reproductive system types. Accordingly, L. dufourii (Girard) Kuntze, the only species studied to date using microsatellite markers, showed lower genotypic diversity and a stronger population differentiation than L. narbonense (72.06 vs. 18.82% of the variance distributed among populations; see Palop-Esteban et al 2007 and Table 2), as consequence of triploidy, which involves male sterility, absence of recombination at meiosis, and exclusively apomictic reproduction. Fixation indices (F IS ) do not provide support for nonrandom mating and asexual reproduction in L. narbonense.…”

“…Although in some of these taxa the absence of sexuality may pose a problem for gaining new genetic diversity González-Candelas 1997a, b 1999;Palop et al 2000;Palop-Esteban et al 2007), they may still benefit from higher seed-set through apomixis and higher molecular variability than their separate diploid counterparts due to their hybrid origin.…”

“…These taxa of hybrid origin usually form monomorphic populations with regards to the SI systems (A/cob or B/papillate) and have strong pollen sterility because of abnormal meiosis. In such species reproduction is via apomixis (Baker 1953a;Erben 1979) which reduces the possibility of generation of novel genetic variation after hybridization (Palop-Esteban et al 2007).…”

Genetic analysis of salt-marsh sedge Carex scabrifolia Steud. populations using newly developed microsatellite markers

“…Conservation and restoration strategies for endangered clonal plants must pay careful attention to genetic diversity of the population (e.g., Palop-Esteban et al 2007;Rasmussen and Kollmann 2008). Our data revealed that the genetic diversity and integrity of populations of the clonal salt-marsh sedge C. scabrifolia differ greatly, irrespective of population size.…”