High genetic differentiation in marginal populations of European white elm (Ulmus laevis)

Abstract

Studies on the amount of genetic variation in marginal populations and differentiation between them are essential for assessment of best gene conservation strategies and sampling schemes. Thirteen marginal populations of Ulmus laevis in southern Finland and one in Estonia were investigated for genetic variation in 20 allozyme loci. Population differentiation among Finnish stands was high, F st = 0.290, and mean genetic diversity low, H e = 0.088. The differentiation follows the isolation-by-distance structure within the core of the distribution area (lake Vanajavesi). Fairly high frequency of recurrent genotypes was observed, but this did not have an influence on the genetic parameters. The observed genetic structure is consistent with the central-marginal hypothesis. In the light of the results, the Finnish gene conservation strategy for U. laevis seems to be on a sound basis.

Ulmus laevis in the Iberian Peninsula: a review of its ecology and conservation

“…The loss of suitable habitats due to human-induced changes in riparian forests, combined with the effect of Dutch elm disease (DED), has compromised the survival of many U. laevis populations (Collin 2003). It is estimated that only 1 % of the elms still remain alive in Germany (Mackenthun 2004), whereas the white elm is considered an endangered species in northern Belgium (Vander Mijnsbrugge et al 2005), southern France (Timbal & Collin 1999), and Finland , Vakkari et al 2009). Moreover, many small isolated populations throughout its distribution range are at risk of genetic drift (Collin 2003).…”

Dissection of leaf morphological traits from isolated and declined relict populations of Ulmus laevis reveals putative random ecotype evolution

“…For instance, although variation in pubescence can be related to water deficiency (Johnson 1975), negligible differences in precipitation regimes among the origins of the sampled populations cannot explain the deviation of the Halle population for this character. This all suggests that the morphological deviation of the two relict populations is caused ''randomly'', putatively triggered by the phenomenon of genetic drift that has been observed for U. laevis (Vakkari et al 2009), rather than by local adaptation, natural selection or epigenetic polymorphism (that would result from environmental heterogeneity). Hybridisation with taxa of the U. minor-U.…”

“…Relict populations do not only suffer from declined population sizes. Several molecular studies have detected low genetic diversities within natural populations together with high population differentiations (Vakkari et al 2009;Venturas et al 2013) and Central European populations show a demographic signature of recent bottlenecks (Nielsen and Kjaer 2010).…”

Genomics of the Dutch elm disease pathosystem: are we there yet?

“…There is, however, surprisingly little genomic information on elms compared to other broadleaved tree species found in the same parts of the world, such as poplars, beech or oaks (Kremer et al 2012, Staszak & Paw-lowski 2012, even though elm breeding programs have been existing for over 80 years (Mittempergher & Santini 2004). Molecular and genomic studies of elms were mostly concerned with species identification (Coleman et al 2000, Whiteley et al 2003, population genetics and structure (Gil et al 2004, Zalapa et al 2008, Vakkari et al 2009, Venturas et al 2013), elm conservation (Goodall-Copestake et al 2005 and introgression between invasive and native elm species (Zalapa et al 2010, Brunet et al 2013.…”