Distinct male reproductive strategies in two closely related oak species

Abstract

Reproductive strategies of closely related species distributed along successional gradients should differ as a consequence of the trade-off between competition and colonization abilities. We compared male reproductive strategies of Quercus robur and Q. petraea, two partly interfertile European oak species with different successional status. In the studied even-aged stand, trees of the late-successional species (Q. petraea) grew faster and suffered less from intertree competition than trees of the early-successional species (Q. robur). A large-scale paternity study and a spatially explicit individual-based mating model were used to estimate parameters of pollen production and dispersal as well as sexual barriers between species. Male fecundity was found to be dependent both on a tree's circumference and on its environment, particularly so for Q. petraea. Pollen dispersal was greater and more isotropic in Q. robur than in Q. petraea. Premating barriers to hybridization were strong in both species, but more so in Q. petraea than in Q. robur. Hence, predictions based on the competition-colonization trade-off are well supported, whereas the sexual barriers themselves seem to be shaped by colonization dynamics.

Genetic Insights into Ecological Succession from Oak- (Quercus robur L.) to Beech- (Fagus sylvatica L.) Dominated Forest Stands

“…In the case of oaks, the recently proposed validated multiplexes of microsatellites were used mostly to study mating patterns (Lagache et al, 2014), interspecific hybridization processes (Lander et al, 2013) or species identification (Neophytou, 2013;Rellstab et al, 2016) rather than genetic diversity (Curtu et al, 2015;Moracho et al, 2016). Nevertheless, the levels of population genetic parameters found in our study were similar to those observed by other authors (Streiff et al, 1998;Cottrell et al, 2003;Curtu et al, 2015).…”

Tracing the origin and species identity of Quercus robur and Quercus petraea in Europe: a review

“…Both species are monoecious, anemophilous and mostly outcrossing (CHYBICKI and BURCZYK, 2013;GERBER et al, 2014;LAGACHE et al, 2013). Pollen dispersal kernels indicate both localized dispersal (mean 70-120 m) as well as fat tails representing long distance dispersal events, which translate in high rates of immigrant pollen within the studied stands (BUSCHBOM et al, 2011;CHYBICKI and BURCZYK, 2013;GERBER et al, 2014;LAGACHE et al, 2014;STREIFF et al, 1999). Seed dispersal is more restricted but long-distance dispersal events have also been inferred (GERBER et al, 2014;PETIT et al, 1997;STREIFF et al, 1998).…”

“…nSSRs have been substantially used for pollen flow studies, as their strong polymorphism allows reliable paternity estimation (BUSCHBOM et al, 2011;LEPAIS and GERBER, 2011;. Also many nSSRs have been until now the markers of choice to study the mating system, pollen dispersal and hybridization (BUSCHBOM et al, 2011;CHYBICKI and BURCZYK, 2013;CURTU et al, 2007a;GERBER et al, 2014;LAGACHE et al, 2013LAGACHE et al, , 2014LEPAIS and GERBER, 2010;PETIT et al, 1997;STREIFF et al, 1998STREIFF et al, , 1999. Available nSSRs loci for Q. petraea and Q. robur are reviewed in Table 2.…”

“…Phenotype variation such as leaf morphology and pubescence, and genetic analysis of adults and progenies among species occurring in sympatry showed that low inter-specific pollen-flow (CURTU et al, 2007a), backcross events (LEPAIS and GERBER, 2011), genetically controlled pollen discrimination (LEPAIS and GERBER, 2011), selection against hybrids at the juvenile stage (GUGERLI et al, 2007) and postmating prezygotic reproductive barriers (ABADIE et al, 2012;LAGACHE et al, 2013) have been identified as potential mechanisms maintaining species integrity. The two species have contrasting environmental optima (CHYBICKI et al, 2010;GUICHOUX et al, 2013;NEOPHYTOU and MICHIELS, 2013), different reproductive strategies (LAGACHE et al, 2014) and within-stand environmental heterogeneity sometimes affects the spatial arrangement of the two species (CHYBICKI and BURCZYK, 2013;GUGERLI et al, 2007;LAGACHE et al, 2013LAGACHE et al, , 2014. Further, signatures of divergent selection have been identified (GOICOECHEA et al, 2012).…”

“…+49 4102 696 157, Fax +49 4102 696 200. E-Mail: celine.blanc-jolivet@thuenen.de many studies, but with some asymmetry due to stronger interspecific sexual barriers in Q. petraea (CHYBICKI and BURCZYK, 2013;CURTU et al, 2007a;GERBER et al, 2014;LAGACHE et al, , 2014LEPAIS and GERBER, 2011), although signals of past asymmetric introgression toward Q. petraea could be observed at loci with high interspecific differentiation (GUI-CHOUX et al, 2013). Furthermore, both species seem to actively diverge from each other (GOICOECHEA et al, 2012), which probably results in successful morphological and genetic identification of pure and hybrid individuals (CHYBICKI et al, 2010;CURTU et al, 2007a, b;FORTINI et al, 2015;GUGERLI et al, 2007;GUI-CHOUX et al, 2011NEOPHYTOU, 2014;NEOPHYTOU et al, 2015;YÜCEDAG and GAILING, 2013).…”