Genetic structure of the seagrass Posidonia oceanica in the Western Mediterranean:ecological implications

Abstract

The seagrass Posidonia oceanica (L.) Delile plays a dominant role in coastal ecosystem dynamics in the Mediterranean Sea. This species reproduces both sexually through germination and asexually through vegetative propagation of subterranean rhizomes. Though flowering and fruiting are common, seedlings rarely succeed. An extensive population of P oceanica on the coast of the Island of Ischia (Gulf of Naples, Italy) was found to be nearly clonal when analysed with 2 DNA fingerprinting techniques, minisatellites and random amplified polymorphic DNA ( R A P D ) ; the results show similarity values of 1 and >0.91, respectively. Furthermore, a comparably hlgh genetic similarity was observed between this populat~on and individuals from another lschia population and from the coast of Spain. These findlngs support clonal propagation as the dominant reproductive mode for this specles. The presence of limited numbers of genotypes in the Western Mediterranean basin coupled with a very slow rhlzome elongation rate and the sign~ficant anthropogenic stress on these populations is cause for concern over the long-term ecological stability of this keystone species.

Meadow-scale genetic structure in Posidonia oceanica

“…For each sampled shoot, 1 fresh leaf (approximately 100 mg wet weight) was removed and placed into a 1.5 ml tube. Samples were ground under liquid nitrogen, and genomic DNA was extracted using a modified hexadecyltrimethyl ammonium bromide (CTAB) method (Procaccini et al 1996). Thirteen polymorphic microsatellite regions, 12 nuclear and 1 chloroplast (Procaccini & Waycott 1998, Alberto et al 2003, were used to obtain individual multilocus genotypes.…”

Comparison of ISSR and SSR markers for analysis of genetic diversity in the seagrass Posidonia oceanica

“…P. oceanica meadows exhibit different levels of genetic variability when investigated with different molecular markers. Initial studies using allozymes (Capiomont et al 1996) and multilocus DNA markers such as randomly amplified polymorphic DNA (RAPD) and M13-DNA fingerprinting (Procaccini et al 1996) indicated that meadows were almost completely clonal and highly distinct genetically. More recent studies using more RAPD primers (Jover et al 2003, Micheli et al 2005) and tri-and heptanucleotide microsatellites (SSRs; Procaccini et al 2001Procaccini et al , 2002, contradicted these findings detecting higher levels of variation.…”

Genetic structure of natural and restored shoalgrass Halodule wrightii populations in the NW Gulf of Mexico

“…Given the proper set of conditions, however, significant differentiation can occur over distances as small as 5 km (Olsen et al 2004). Those species that exhibit significant levels of differentiation often do so in a seemingly random fashion, most often attributed to stochastic factors affecting dispersal, such as prevailing current patterns (Procaccini et al 1996) or geologic history (Olsen et al 2004).…”

“…Ruckelshaus 1998, Williams & Orth 1998, Reusch et al 1999, Williams 2001, Reusch 2002, Hämmerli & Reusch 2003, Olsen et al 2004, Muñiz-Salazar et al 2005 and Posidonia oceanica (e.g. Procaccini et al 1996, Procaccini & Piazzi 2001, Jover et al 2003. In contrast, little is known of the local or regional genetic structure of Halodule wrightii, a common inhabitant of shallow waters throughout the Caribbean region.…”