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- Recruit survival of Cymodocea nodosa along a depth gradientPublication . Paulo, Diogo; Manent, Pablo; Barrio, Juan M.; Serrão, Ester; Alberto, FilipeClonal plants can reproduce sexually and clonally, expressing different proportions of these different life histories in distinctive environments. In seagrass meadows, light attenuation hinders marine plant colonization in deeper areas of its vertical distribution. Therefore it is expected that the fluorescence maximum quantum yield of seedlings will be higher at deep limits of the meadow relative to shallower depths. We hypothesized that seagrass seedlings experience higher mortality in deeper areas of the meadows than at shallower levels. Our objective was to test survival of seagrass seedlings along a depth gradient in meadows of Cymodocea nodosa in the Canary Islands. Seedlings germinated in laboratory conditions, were transplanted to a natural meadow at three water depths: shallow (5 m), medium (8 m) and deep (12 m). Transplanted seedlings were monitored by measuring maximum quantum yield, leaf length, number of leaves per shoot and survival. Our data suggest that light does not hinder survival of seedlings along the depth gradient of the meadow. Before establishing clonal growth, seedlings in deeper areas had higher survival rates than those in shallow areas. Even though seeds are present at shallow depths and sexual allocation is high, sexual contribution can be lower than expected due to seedling loss.
- Sexual reproduction vs. clonal propagation in the recovery of a seagrass meadow after an extreme weather eventPublication . Paulo, Diogo; Diekmann, Onno; Ramos, Ana; Alberto, Filipe; Serrao, EsterMarine flowering plants can reproduce sexually and clonally, and the relative contribution of these two modes can be dependent on the environmental conditions. Zostera marina, a seagrass widely distributed in the northern hemisphere, can form annual and perennial meadows with different proportions of sexual versus clonal propagation depending on the environmental disturbance regime. We study the hypothesis that the contribution of sexual propagation varies during the recovery of a seagrass meadow. In this case study, we compare the proportion of sexual versus clonal propagation of a perennial Z. marina meadow before its disappearance due to winter storms and after recovery. Before disturbance, genotypic diversity was high, indicating frequent sexual reproduction events likely to create an abundant seed bank. Seedling germination allowed the population to recover after the extreme disturbance. As months passed, seedlings became rare and finally absent, giving place to adult shoots. In an advanced stage of colonization, the shoots colonized the area by vegetative growth, which lowered the genotypic diversity. Despite this reduction over time, the genotypic diversity of the new meadow is still high, demonstrating the importance of sexual reproduction in meadow recovery and persistence.