Genetic neighbourhood of clone structures in eelgrass meadows quantified by spatial autocorrelation of microsatellite markers

Abstract

Limited dispersal distances in plant populations frequently cause local genetic structure, which can be quantified by spatial autocorrelation. In clonal plants, three levels of spatial organization can contribute to positive autocorrelation; namely, the neighbourhood of (a) ramets, (b) clone fragments and (c) entire clones. Here we use data from an exhaustive sampling scheme on a clonal plant to measure the contribution of the neighbourhoods of each distinct clonal structure to total spatial autocorrelation. Four plots (256 grid points each) within dense meadows of the marine clonal plant Zostera marina (eelgrass) were sampled for clone structure with nine microsatellite markers (E80 alleles). We found significant coancestry (f ij ), at all three levels of spatial organization, even when not allowing for joins between samples of identical genets. In addition, absolute values of f ij and the maximum distance with significant positive f ij decreased with the progressive exclusion of joins between alike genotypes. The neighbourhood of this clonal plant thus consists of three levels of organization, which are reflected in different kinship structures. Each of these kinship structures may affect the level of biparental inbreeding and the physical distance between flowering shoots and their outcrossing neighbourhood. These results also emphasize the notion that spatial autocorrelation crucially depends on the scale and intensity of sampling.

Small-scale spatial genetic structure in Scopalina lophyropoda, an encrusting sponge with philopatric larval dispersal and frequent fission and fusion events

“…Spatial autocorrelation analysis is indicated for quantifying the component of genetic structure due to limited dispersal (Hämmerli & Reusch 2003). Our predictions on restricted dispersal in the species, based on its presumed philopatric larval behaviour , Mariani et al 2006, have been confirmed by autocorrelation statistics (Fig.…”

“…Since populations were relatively small and spatial autocorrelation has been reported to strongly depend on the scale and intensity of sampling (Hämmerli & Reusch 2003), we collected sponge fragments from all the individuals along each rocky wall (n = 27, n = 13 and n = 30 for Walls 1, 2 and 3, respectively). There were no individuals in the rocky areas between walls.…”

Meadow-scale genetic structure in Posidonia oceanica

“…To date, meadow genetic structure and genetic similarity among pairs of ramets have been analysed as a function of their pairwise distance in only a few seagrass species. A positive spatial autocorrelation of kinship coefficients was found at a distance of 2 to 5 m and 2 m in the monoecious Zostera marina and Z. noltii, respectively (Hämmerli & Reusch 2003b, Coyer et al 2004, and at a distance of 10 to 16 m in the dioecious Cymodocea nodosa (Ruggiero et al 2005b).…”

Eelgrass Zostera marina populations in northern Norwegian fjords are genetically isolated and diverse

“…Both are affected by shoot density of the meadow, which itself can become a recruitment barrier (Duarte et al 2006, Neiva et al 2012. Mosaic patterns of Zostera marina genotypes, attributed to sporadic recruitment and limited dispersal, have been documented in Brittany (Becheler et al 2010) and Schleswig-Holstein (Hämmerli & Reusch 2003). Both Medby and Sørkjosen are dense meadows, suggesting that recruitment may be limited.…”

“…Meadows may be heterogeneous as a consequence of temporal admixture events of repeated recruitment through time (originally proposed by Petit et al 2003for oaks, Becheler et al 2010; limited dispersal of pollen and seeds, leading to patchiness (Hämmerli & Reusch 2003); and local habitat selection (Oetjen & Reusch 2007, Oetjen et al 2010, Winters et al 2011. Alternatively, they can be homogeneous as a consequence of dominance by a few large genets/clones (Reusch et al 1999, Coyer et al 2008) and limited recruitment (Duarte et al 2006).…”