Spatial patterns of genetic diversity in Posidonia oceanica, an endemic Mediterranean seagrass

Abstract

Posidonia oceanica is an endemic seagrass species in the Mediterranean Sea. In order to assess levels of genetic structure in this species, the microsatellite polymorphism was analysed from meadows collected in several localities, along the coasts of the Tyrrhenian Sea (Mediterranean Sea). The existence of single population units and the recruitment of seedlings collected in some localities were investigated. Moreover, genetic structure at different spatial scales and biogeographic relationships among populations were also assessed. Our analysis showed the existence of clear patterns of genetic structure in P. oceanica in the area considered in the analysis. P. oceanica, in fact, is present in separate meadows that represent discrete populations, characterized by low genetic diversity. Comparable levels of genetic variability between mature meadows and seedlings were found. Patterns of genetic relatedness among populations seem to be in accord with direction of dominant current flux in the whole area, separating South Tyrrhenian from North Tyrrhenian populations. Moderate levels of gene flow between populations and genetic substructure within populations, together with the finding of the limited role of sexual reproduction in increasing genetic variability, should be a cause for concern for the persistence of this essential resource in the Mediterranean basin.

Long‐term acclimation to reciprocal light conditions suggests depth‐related selection in the marine foundation speciesPosidonia oceanica

“…This shift in the reproductive phenology reduces gene flow along the depth, enhancing the partial isolation and neutral drift of the different meadow's stands (D'Esposito et al., 2012; Migliaccio et al., 2005; Procaccini & Mazzella, 1998; Procaccini et al., 2001). In addition, despite the potential free dispersion of clonal fragments within the meadow, the strong separation between shallow and deep stands indicates that recruitment of adult individuals coming from other depths is rare.…”

“…This condition can represent an intrinsic barrier to gene flow and can promote the emergence of divergent selection between the two stands. Indeed, a consistent level of genetic differentiation between depths has been recorded in various populations (D'Esposito, Dattolo, Badalamenti, Orsini, & Procaccini, 2012; Migliaccio et al., 2005; Procaccini et al., 2001). Moreover, plants growing at different depths show differences in their response to temperature (Marín‐Guirao, Ruiz, Dattolo, Garcia‐munoz, & Procaccini, 2016) and in many phenotypic characters also affecting meadow structure (Zupo et al., 2006), such as: leaf morphology (Dalla Via et al., 1998), photo‐physiology (Dattolo et al., 2013, 2014; Mazzuca et al., 2013; Pirc, 1986), growth, and respiration (Olesen, Enriquez, Duarte, & Sand‐Jensen, 2002).…”

Morphological and Genetic Variation in the Endemic Sea Grass Halophila hawaiiana (Hydrocharitaceae) in the Hawaiian Archipelago

“…Some marine animal species with high dispersal potential (e.g., with planktonic larvae or long-distance migrating adults) have a practical dispersal limit, and gene flow can be affected by island position, ocean currents, random long-distance dispersal events, larval behavior, natal homing, and selection (Palumbi et al 1997). Gene flow has been estimated in only a few seagrass populations (Williams and Davis 1996, Procaccini and Mazella 1998, Ruckelshaus 1998, Schlueter and Guttman 1998, Procaccini et al 2001, Reusch 2001. The practical dispersal limit of H. hawaiiana remains undetermined.…”

Effect of habitat fragmentation on the genetic diversity of Stipa krylovii Reshov. in an agro-pastoral ecotone in northern China

“…Some empirical studies arrived at the same conclusion (Young et al 1993;Fore´and Guttman 1999;Procaccini et al 2001;Jump and Pen˜uelas 2006). Results from our study suggest there is a low level of genetic differentiation and diversity (Tables 3 and 4) between fragmented and non-fragmented S. krylovii populations in an agro-pastoral ecotone of a typical steppe in northern China.…”