Seagrass Evolution, Ecology and Conservation: A Genetic Perspective

Waycott, Michelle; Procaccini, Gabriele; Les, Donald H.; Reusch, Thorsten B. H.

doi:10.1007/978-1-4020-2983-7_2

Cited by 36 publications

(21 citation statements)

References 122 publications

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“…Wider and darker edges represent the most connected sites of this study with the highest relative connectivity (1.0) between 23.US Craig Key and 24.US Arsenicker. The numbers within the nodes represent the populations as in Table 1 Trinidad Bermuda and other T. testudinum populations is a strong indicator of the dispersal potential of this species, a characteristic that is likely widespread across all the seagrass groups (Kendrick et al, 2012;McMahon et al, 2014;Waycott, Procaccini, Les, & Reusch, 2006).…”

Section: Genetic Diversity Throughout the Rangementioning

confidence: 99%

Range‐wide population genetic structure of the Caribbean marine angiosperm Thalassia testudinum

Dijk

Bricker

Tussenbroek

et al. 2018

Ecology and Evolution

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Many marine species have widespread geographic ranges derived from their evolutionary and ecological history particularly their modes of dispersal. Seagrass (marine angiosperm) species have ranges that are unusually widespread, which is not unexpected following recent reviews of reproductive strategies demonstrating the potential for long‐distance dispersal combined with longevity through clonality. An exemplar of these dual biological features is turtle grass (Thalassia testudinum) which is an ecologically important species throughout the tropical Atlantic region. Turtle grass has been documented to have long‐distance dispersal via floating fruits and also extreme clonality and longevity. We hypothesize that across its range, Thalassia testudinum will have very limited regional population structure due to these characteristics and under typical models of population structure would expect to detect high levels of genetic connectivity. There are very few studies of range‐wide genetic connectivity documented for seagrasses or other sessile marine species. This study presents a population genetic dataset that represents a geographic area exceeding 14,000 km2. Population genetic diversity was evaluated from 32 Thalassia testudinum populations sampled across the Caribbean and Gulf of Mexico. Genotypes were based on nine microsatellites, and haplotypes were based on chloroplast DNA sequences. Very limited phylogeographic signal from cpDNA reduced the potential comparative analyses possible. Multiple analytical clustering approaches on population genetic data revealed two significant genetic partitions: (a) the Caribbean and (b) the Gulf of Mexico. Genetic diversity was high (H E = 0.641), and isolation by distance was significant; gene flow and migration estimates across the entire range were however modest, we suggest that the frequency of successful recruitment across the range is uncommon. Thalassia testudinum maintains genetic diversity across its entire distribution range. The genetic split may be explained by genetic drift during recolonization from refugia following relatively recent reduction in available habitat such as the last glacial maxima.

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Section: Genetic Diversity Throughout the Rangementioning

confidence: 99%

Range‐wide population genetic structure of the Caribbean marine angiosperm Thalassia testudinum

Dijk

Bricker

Tussenbroek

et al. 2018

Ecology and Evolution

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“…Our study species, eelgrass (Zostera marina), belongs to the seagrasses, a polyphyletic group of monocotyledoneous flowering plants (angiosperms) that returned to the marine habitat three times independently within the group Alismatidae (Waycott et al 2006). In shallow waters, their extensive meadows play an important role as foundation species for productive ecosystems and for sediment stabilization (Hemminga & Duarte 2000).…”

Section: Study Species and Sampling Sitesmentioning

confidence: 99%

Genome scans detect consistent divergent selection among subtidal vs. intertidal populations of the marine angiosperm Zostera marina

Oetjen

Reusch

2007

Molecular Ecology

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Genome scans are a powerful tool to detect natural selection in natural populations among a larger sample of marker loci. We used replicated habitat comparisons to search for consistent signals of selection among contrasting populations of the seagrass Zostera marina, a marine flowering plant with important ecological functions. We compared two different habitat types in the North Frisian Wadden Sea, either permanently submerged (subtidal) or subjected to aerial exposure (intertidal). In three independent population pairs, each consisting of one tidal creek and one tidal flat population each, we carried out a genome scan with 14 expressed sequence tag (EST)-derived microsatellites situated in 5'- or 3'-untranslated regions of putative genes, in addition to 11 anonymous genomic microsatellites. By using two approaches for outlier identification, one anonymous and two EST-derived microsatellites showed population differentiation patterns not consistent with neutrality. These microsatellites were detected in several parallel population comparisons, suggesting that they are under diverging selection. One of these loci is linked to a putative nodulin gene, which is responsible for water channelling across cellular membranes, suggesting a functional link of the observed genetic divergence with habitat characteristics.

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“…Seagrasses, a polyphyletic group of 60 or so marine flowering plants, are not only ecologically very important (Williams & Heck Jr 2001;Duarte 2002). They have also become a major focus of plant population genetics because of their interesting life history involving sexual reproduction through subaqueous pollination in combination with rhizomateous clonal spreading (Reusch 2001;Waycott et al . 2005).…”

Section: Introductionmentioning

confidence: 99%

Does disturbance enhance genotypic diversity in clonal organisms? A field test in the marine angiosperm Zostera marina

Reusch¹

2005

Molecular Ecology

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Physical disturbance has often been invoked to control genotypic diversity in sessile clonal organisms, yet experimental evidence is lacking. I studied the effects of physical disturbance on genet dynamics and genotypic diversity in a clonal marine angiosperm, Zostera marina (eelgrass). In replicated plots of 1 m2, the vegetation canopy was removed in gaps of zero (control), 25%, 50% and 75% of the area (n = 6 replicates). Before removal and during two consecutive years, the genotypic composition was determined using genetic markers (DNA microsatellites) in a 5 x 5 pixel grid per plot. An aggregate index of genet dynamics summarizing recruitment, increase, loss and decrease of clones was maximal at intermediate disturbance levels (quadratic polynomial P = 0.02). Physical disturbance also increased the occurrence of new genotypes, possibly reflecting recruitment (linear model, P < 0.05). Contrary to expectations, there was no competitive advantage of more heterozygous genotypes over less heterozygous ones. In the absence of disturbance, in particular, clones with lower individual heterozygosity were more likely to increase in area over a 1-year time period than more heterozygous ones, while there was no such correlation in plots with disturbance (logistic model, P(disturbance x heterozygosity) = 0.036). Undisturbed plots revealed background recruitment independent of canopy gaps, suggesting that Z. marina exhibits a strategy of continual recruitment. Effects of experimental disturbance (linear or quadratic) on clonal diversity were not detectable. Instead, initial (pretreatment) clonal diversity accounted for between 68% and 91% of the variance in diversity, indicating remarkable resilience of genotypic diversity in the face of physical disturbance.

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Seagrass Evolution, Ecology and Conservation: A Genetic Perspective

Cited by 36 publications

References 122 publications

Range‐wide population genetic structure of the Caribbean marine angiosperm Thalassia testudinum

Range‐wide population genetic structure of the Caribbean marine angiosperm Thalassia testudinum

Genome scans detect consistent divergent selection among subtidal vs. intertidal populations of the marine angiosperm Zostera marina

Does disturbance enhance genotypic diversity in clonal organisms? A field test in the marine angiosperm Zostera marina

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