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Individual-based genetic analyses support asexual hydrochory dispersal in Zostera noltei

Publication . Berković, Buga; Coelho, Nelson; Gouveia, Licínia; Serrao, Ester; Alberto, Filipe

Dispersal beyond the local patch in clonal plants was typically thought to result from sexual reproduction via seed dispersal. However, evidence for the separation, transport by water, and re-establishment of asexual propagules (asexual hydrochory) is mounting suggesting other important means of dispersal in aquatic plants. Using an unprecedented sampling size and microsatellite genetic identification, we describe the distribution of seagrass clones along tens of km within a coastal lagoon in Southern Portugal. Our spatially explicit individual-based sampling design covered 84 km(2) and collected 3 185 Zostera noltei ramets from 803 sites. We estimated clone age, assuming rhizome elongation as the only mechanism of clone spread, and contrasted it with paleo-oceanographic sea level change. We also studied the association between a source of disturbance and the location of large clones. A total of 16 clones were sampled more than 10 times and the most abundant one was sampled 59 times. The largest distance between two samples from the same clone was 26.4 km and a total of 58 and 10 clones were sampled across more than 2 and 10 km, respectively. The number of extremely large clone sizes, and their old ages when assuming the rhizome elongation as the single causal mechanism, suggests other processes are behind the span of these clones. We discuss how the dispersal of vegetative fragments in a stepping-stone manner might have produced this pattern. We found higher probabilities to sample large clones away from the lagoon inlet, considered a source of disturbance. This study corroborates previous experiments on the success of transport and re-establishment of asexual fragments and supports the hypothesis that asexual hydrochory is responsible for the extent of these clones.

2018-08Journal article

Open Access

Landscape genetics of a seagrass species in a tidal mudflat lagoon

Publication . Berković, B.; Serrão, Ester; Alberto, Filipe

In this thesis I looked at different components of dispersal in the seagrass Zostera noltii, from the dispersal potential of both sexual and asexual propagules to indirect genetic estimation and landscape genetics analysis. My studies show that the dispersal biology of Z. noltii is very dependent on commonly underestimated asexual dispersal. This asexual LDD is the most parsimonious explanation for the wide distribution of clones in the lagoon and dramatically changes our view of the species’ life history. Furthermore, I propose that the observed lack of association between landscape features and spatial genetic structure is a consequence of this LDD of asexual propagules. The high dispersal capacity of Z. noltii combined with a tidal regime which homogenizes the otherwise complex lagoon habitat, are prevalent over any effects of landscape on gene flow caused by the lagoon complexity as shown by the landscape genetics analyses. Nevertheless, sexual reproduction also affects spatial genetic structure, as the positive kinship between clones within a 3 km range is a signature of restricted seed dispersal.

2015-10-06Doctoral thesis

Open Access