A generalized heterozygote deficiency assessed with microsatellites in French common ash populations

Abstract

Common ash is a temperate forest tree with a colonizing behaviour, a discontinuous spatial distribution and a peculiar and poorly known mating system. Microsatellite markers were used to study the genetic structure in natural populations of common ash. Twelve populations located in northeastern France were analysed at five loci. Levels of genetic variability within and among stands were estimated for the seedling and adult stages. As expected for a forest tree, our results reveal high levels of intrapopulation diversity and a low genetic differentiation between stands. However, a general and significant heterozygote deficiency was found, with a mean F(IS) of 0.163 for the seedlings and of 0.292 for the adult trees. The different explanations for such an excess homozygosity are discussed: a nonMendelian inheritance of alleles, the presence of null alleles, a Wahlund effect and assortative mating.

Paternity analysis of pollen-mediated gene flow for Fraxinus excelsior L. in a chronically fragmented landscape

“…Furthermore, genotypes observed at loci 3.1 and FEMSATL5 suggest departure from Mendelian segregation and occurrence of null alleles that has also been discussed in other F. excelsior studies (Heuertz et al, 2001;Morand et al, 2002).…”

“…The phylogeography of the species is now well described (Morand et al, 2002;Heuertz et al, 2004;Ferrazzini et al, 2007). F. excelsior displays a complex, polygamous sexual system (FRAXIGEN, 2005) in which individuals may be classified phenotypically across a continuum from purely male to purely female with a whole range of hermaphroditic intermediates.…”

Estimating dispersal from short distance spatial autocorrelation

“…While as noted earlier, a larger number of alleles generally increases statistical power per locus (or per genotyping-effort), numbers of alleles are sometimes so large that it seems likely that mutation is occurring at rates near 10 À2 . For example, albeit at a larger spatial scale, Morand et al (2002) employed loci having as many as 56 alleles. The demonstrated effects of high mutation rates suggest that some caution is in order.…”

Thank you for not flowering: conservation genetics and gene flow analysis of native and non-native populations of Fraxinus (Oleaceae) in Ireland

“…Six nuclear microsatellite markers (FEMSATL 4, FEMSATL 11, FEMSATL 12, FEMSATL 16, FEMSATL 19 (Lefort et al, 1999) and M2-30 ) were used to genotype all the samples; these markers had been used previously for successful characterization of common and hybrid ash populations (Fernández-Manjarres et al, 2006;Thomasset et al, 2011a). The PCR methodology followed Morand et al (2002). PCR products were analysed using an Applied Biosystems 3130xl Genetic Analyser (Applied Biosystems, Foster City, CA, USA) and allele sizes were determined from the raw data using GeneMapper v. 4.0 (Applied Biosystems).…”

“…Pollination can occur over short distances in dense stands in which highly fertile trees might dominate the pollen clouds (Morand, 2003) to several kilometres in small and isolated populations (Bâcles et al, 2005). A deficiency of heterozygotes, very low rates of selfing and high levels of pollen dispersal with relatively moderate degrees of isolation-by-distance are common traits that are found in different populations of F. excelsior (Morand et al, 2002;Heuertz et al, 2003;Morand, 2003). Levels of heterozygosity and gene flow as well as the mating system of F. angustifolia are much less well characterized outside hybridization studies (Fernández-Manjarres et al, 2006;Gérard et al, 2006c).…”