Mega Clonality in an Aquatic Plant—A Potential Survival Strategy in a Changing Environment

Bricker, Eric; Calladine, Ainsley; Virnstein, Robert W.; Waycott, Michelle

doi:10.3389/fpls.2018.00435

Cited by 30 publications

(36 citation statements)

References 37 publications

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“…The same was shown for terrestrial grasses over 30 years ago [88]. Thus, our study indicates some interesting directions for future experimental work, tackling the relative importance of variable clone survival, as suggested by Bricker et al [9], and variable allocation to sexual and asexual reproduction in association with the disturbance regime.…”

Section: Discussionsupporting

confidence: 83%

“…AH seems to be possible for a range of seagrass species that cover a range of sizes, from some of the larger species from genus Posidonia [40,71] to one of the smaller species Halophila johnsonii [41]. Recently, an extremely large clone, spread over 47km, was found for the seagrass Thallassia testidinum in Florida using microsatellite analysis [9]. The authors concluded that AH dispersal was the likely process behind the propagation of this organism.…”

Section: Discussionmentioning

confidence: 99%

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Individual based genetic analyses support asexual hydrochory dispersal in Zostera noltei

Berković

Castilho

Gouveia³

et al. 2018

Preprint

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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 km2 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.

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Section: Discussionsupporting

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Individual based genetic analyses support asexual hydrochory dispersal in Zostera noltei

Berković

Castilho

Gouveia³

et al. 2018

Preprint

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“…Gene flow was the most important microevolutionary force leading to homogeneity in genetic and allelic diversity among populations (Hedrick, 1999). Thalassia testudinum has an elevated capacity for sexually derived long-distance dispersal (van Dijk et al, 2009;Kaldy & Dunton, 1999), and recent research indicates that vegetative dispersal in seagrasses could also be important (e.g., Bricker, Calladine, Virnstein, & Waycott, 2018;Smulders, Vonk, Engel, & Christianen, 2017). Thus, it is to be expected that neighboring populations are more related to each other than more distant ones (Isolation By Distance, Wright, 1943), even when these distant populations are hundreds of kilometers apart.…”

Section: Connectivitymentioning

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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“…To rapidly overcome these density-and patch sizedependent establishment thresholds, many landscape-forming plants rely on clonal expansion as their main mode of dispersal (Bouma et al 2005;Kendrick et al 2005;Hacker et al 2012, Reijers et al 2019a. Next to the ability to generate high local shoot numbers, increase patch size and steer shoot organization, clonality can also greatly enhance the longevity of an individual (de Witte and Stöcklin 2010;Thomas 2013;Bricker et al 2018). This significantly increases its persistence and potential of forming complex biogeomorphic landscapes (Bouma et al 2013;Strain et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Resilience of beach grasses along a biogeomorphic successive gradient: resource availability vs. clonal integration

et al. 2019

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Coastal ecosystems are often formed through two-way interactions between plants and their physical landscape. By expanding clonally, landscape-forming plants can colonize bare unmodified environments and stimulate vegetation-landform feedback interactions. Yet, to what degree these plants rely on clonal integration for overcoming physical stress during biogeomorphological succession remains unknown. Here, we investigated the importance of clonal integration and resource availability on the resilience of two European beach grasses (i.e. Elytrigia juncea and Ammophila arenaria) over a natural biogeomorphic dune gradient from beach (unmodified system) to foredune (biologically modified system). We found plant resilience, as measured by its ability to recover and expand following disturbance (i.e. plant clipping), to be independent on the presence of rhizomal connections between plant parts. Instead, resource availability over the gradient largely determined plant resilience. The pioneer species, Elytrigia, demonstrated a high resilience to physical stress, independent of its position on the biogeomorphic gradient (beach or embryonic dune). In contrast, the later successional species (Ammophila) proved to be highly resilient on the lower end of its distribution (embryonic dune), but it did not fully recover on the foredunes, most likely as a result of nutrient deprivation. We argue that in homogenously resource-poor environments as our beach system, overall resource availability, instead of translocation through a clonal network, determines the resilience of plant species. Hence, the formation of high coastal dunes may increase the resistance of beach grasses to the physical stresses of coastal flooding, but the reduced marine nutrient input may negatively affect the resilience of plants.

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Mega Clonality in an Aquatic Plant—A Potential Survival Strategy in a Changing Environment

Cited by 30 publications

References 37 publications

Individual based genetic analyses support asexual hydrochory dispersal in Zostera noltei

Individual based genetic analyses support asexual hydrochory dispersal in Zostera noltei

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

Resilience of beach grasses along a biogeomorphic successive gradient: resource availability vs. clonal integration

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