Realized gene flow within mixed stands of Quercus robur L. and Q. petraea (Matt.) L. revealed at the stage of naturally established seedling

Abstract

The estimates of contemporary gene flow assessed based on naturally established seedlings provide information much needed for understanding the abilities of forest tree populations to persist under global changes through migration and/or adaptation facilitated by gene exchange among populations. Here, we investigated pollen- and seed-mediated gene flow in two mixed-oak forest stands (consisting of Quercus robur L. and Q. petraea [Matt.] Liebl.). The gene flow parameters were estimated based on microsatellite multilocus genotypes of seedlings and adults and their spatial locations within the sample plots using models that attempt to reconstruct the genealogy of the seedling cohorts. Pollen and seed dispersal were modelled using the standard seedling neighbourhood model and a modification--the 2-component seedling neighbourhood model, with the later allowing separation of the dispersal process into local and long-distance components. The 2-component model fitted the data substantially better than the standard model and provided estimates of mean seed and pollen dispersal distances accounting for long-distance propagule dispersal. The mean distance of effective pollen dispersal was found to be 298 and 463 m, depending on the stand, while the mean distance of effective seed dispersal was only 8.8 and 15.6 m, which is consistent with wind pollination and primarily seed dispersal by gravity in Quercus. Some differences observed between the two stands could be attributed to the differences in the stand structure of the adult populations and the existing understory vegetation. Such a mixture of relatively limited seed dispersal with occasional long distance gene flow seems to be an efficient strategy for colonizing new habitats with subsequent local adaptation, while maintaining genetic diversity within populations.

Comparison of pollen gene flow among four European beech (Fagus sylvatica L.) populations characterized by different management regimes

“…High gene flow through pollen seems a general characteristic of Fagaceae. Almost all estimates of pollen immigration in the literature lie between 0.5 and 0.7 (for example, Dow and Ashley, 1998;Streiff et al, 1999;Buiteveld et al, 2001;Valbuena-Carabaña et al, 2005;Chybicki and Burczyk, 2010b). When values lower than 0.5 were found, they were associated with particular ecological conditions.…”

A nuclear DNA barcode for eastern North American oaks and application to a study of hybridization in an Arboretum setting

“…Hybridization in the genus is common and known to be dependent on spatial distribution of parent trees, pollen dispersal and pollination time, and sexual barriers among other factors (Lagache, Klein, Guichoux, & Petit, 2013; Petit, Bodénès, Ducousso, Roussel, & Kremer, 2004). Oak species with similar reproductive strategies and overlapping geographic regions often hybridize in natural stands (Chybicki & Burczyk, 2010; Curtu, Gailing, & Finkeldey, 2007; Dodd & Afzal‐Rafii, 2004; Dumolin‐Lapègue, Démesure, Fineschi, Le Corre, & Petit, 1997; Dumolin‐Lapègue, Kremer, & Petit, 1999; Efrain Tovar‐Sanchez, 2004; Gerber et al., 2014; Hipp & Weber, 2008; Lexer, Kremer, & Petit, 2006; Moran, Willis, & Clark, 2012; Petit, 1993; Petit et al., 2004; Whittemore & Schaal, 1991). Morphological intermediacy, however, is an imperfect predictor of genetic admixture in oaks, making hybrids difficult to identify (Burgarella et al., 2009; Song, Deng, Hipp, & Li, 2015; Wei, Li, Zhang, & Liao, 2015).…”

Genetic evidence of reproductive isolation in a remote enclave of Quercus pubescens in the presence of cross-fertile species

“…In European white oaks effective pollen dispersal is usually bimodal, as a result of limited pollen dispersal within a population and a large pollen immigration from outside (e.g. Streiff et al 1999;Salvini et al 2009;Chybicki and Burczyk 2010;Buschbom et al 2011;Lepais and Gerber 2011). However, due to very low effective pollen immigration (as our results suggest), in the study population a distribution of mating distances can be unimodal with a peak at short distances.…”

“…In oaks, restricted dispersal of acorns was recognised as a primary mechanism shaping the spatial autocorrelation of genes (Streiff et al 1998;Grivet et al 2009;Nakanishi et al 2009;Chybicki and Burczyk 2010). Based on the results alone, we obviously cannot exclude that a similar phenomenon occurred in the study population.…”

“…A common observation is that a few tens percent of acorns result from pollination with immigrating pollen (e.g. Streiff et al 1999;Curtu et al 2009;Lepais and Gerber 2011;Buschbom et al 2011), and the immigration rate is relatively stable at the stage of established seedlings (Chybicki and Burczyk 2010;Lepais and Gerber 2011). This suggests that the population of Q. pubescens in Bielinek should experience a permanent oak pollen flow from the outside as well.…”