The Origin of Clonal Diversity and Structure of Populus alba in Sardinia: Evidence from Nuclear and Plastid Microsatellite Markers

Abstract

The uniqueness of the cpDNA haplotypes, the prevalence of clonality and the restricted number of genets recorded suggest that Sardinian white poplar could be a floristic relict of the native flora of the island, which has spread through available habitats on the island mainly by means of vegetative propagation and human activities.

Genetic Biodiversity and Phylogenetic Studies in Poplar by Means of the Metallothionein Multigene Family

“…The natural and semi-natural banks of the river are surrounded by grazing lands for buffalo and fields of maize and vegetables, and are also the ideal sites for the spontaneous reproduction of white poplar natural populations. The Cp-SSR analysis performed on the 63 individuals of the Sele river population highlighted a number of alleles (per single locus and in total) and haplotypes comparable with that observed for the white poplar population of the Ticino river previously investigated by this research group (8 Vs 9 haplotypes, Brundu et al, 2008), and slightly higher than that of two populations of the Danube river (8 Vs 5, Lexer et al, 2005), but a little lower than that calculated for a limited number of white poplar specimens collected in different regions of the Mediterranean basin (8 Vs 10, Brundu et al, 2008). However, the higher number of haplotypes observed in the population of the Ticino river could be ascribed to the presence of several hybrids (P. x canescens) derived from the natural cross between P. alba and P. tremula (Fossati et al, 2004;Castiglione et al, 2010), being the last observation further confirmed by Lexer and co-workers in the case of two populations of the Danube and of one of the Ticino (2005Ticino ( , 2010.…”

“…Population biodiversity was evaluated by number of alleles, frequency, observed and expected heterozygosity; within-population inbreeding coefficient F IS for microsatellite loci was also estimated using the available free software package GenAlex6 (Peakall & Smouse, 2006) freely available at the following web site: http://www.anu.edu.au/BoZo/GenAlEx/new_version.php. Furthermore, some of the nuclear SSR markers were used to determine the genetic relationship of the Sele population compared to some selected specimens belonging to already surveyed P. alba populations (Brundu et al, 2008;Castiglione et al, 2009;, as described above. The molecular similarity of the defined four groups of poplars was assessed performing a PCA (Principal Component Analysis) by means of the NTSYS-pc program version 2.1 (Rohlf & Marcus, 1993), using as distance the Jaccard dissimilarity index (Jaccard, 1908).…”

Population clustering and clonal structure evidence the relict state of Ulmus minor Mill. in the Balearic Islands

“…Established clones are much more likely to survive these violent discharges carrying tons of debris than newly established seedlings. At the same time, root fragments can be uprooted and transported in the flow, contributing to long distance recruitment of elm clones in the Balearic populations, similarly to what has been observed in other riparian species (Barsoum et al, 2004;Brundu et al, 2008;Macaya-Sanz et al, 2012). Given enough time, long distance dispersal of root fragments and vegetative propagation under benign climates could explain the presence of some clones in distant watersheds, albeit we cannot exclude human contribution to this feature Macaya-Sanz et al, 2012), or (despite our analyses suggesting otherwise), that these shared multi-locus genotypes between watersheds are independently sexually derived.…”

Genetic analysis of post-mating reproductive barriers in hybridizing European Populus species

“…This hypothesis is supported by high mortality (34%) during early life stages of the BC 1 progeny and by the low level of heterozygosity of the P. alba backcross parent (only 38%), compared with 67% of heterozygous loci in the F 1 hybrid parent of the backcross. This suggests that increased heterozygosity due to introgression can ameliorate the negative effects of biparental inbreeding (that is of recessive deleterious alleles in homozygous state) in P. alba; biparental inbreeding in P. alba becomes apparent from the great magnitude of short-range kinship coefficients among individuals (F ij ) in recent studies of spatial genetic structure in this species (van Loo et al, 2008), and from the extra-ordinary clone sizes of genets of P. alba in Southern Europe (Brundu et al, 2008;González-Martí-nez and coworkers, unpublished data). Hypothesis 3, increased introgression due to cytonuclear interactions (Galloway and Fenster, 1999;Tiffin et al, 2001;Futuyma, 2009), is equally supported by our data: our plastid DNA data indicate a P. tremula cytoplasm for the female F 1 hybrid parent of our interspecific BC 1 .…”