Effects of density on the vital rates of a modular seaweed

Viejo, Rosa M.; Åberg, Per

doi:10.3354/meps221105

Cited by 24 publications

(31 citation statements)

References 61 publications

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“…High lateral densities suppressed lateral initiation in Sargassum ilicifolium, as has been reported for other fucoid algae (Lazo & Chapman 1998, Viejo & Åberg 2001, Ateweberhan 2004. Module initiation may be density regulated, as a mechanism to avoid overcrowding and competition among modules.…”

Section: Effects Of Lateral Densitysupporting

confidence: 70%

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Seasonal dynamics of Sargassum ilicifolium (Phaeophyta) on a shallow reef flat in the southern Red Sea (Eritrea)

Ateweberhan¹,

Bruggemann²,

Breeman³

2005

Mar. Ecol. Prog. Ser.

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The seasonality of Sargassum ilicifolium was studied in the southern Red Sea by monitoring thallus density, thallus size and the initiation, growth, reproduction and survivorship of primary laterals. Thallus density showed slight but significant seasonal variation; it was highest at the end of the hot season and lowest at the end of the cold season. Mean thallus and lateral lengths peaked in the second half of the cold season. Initiation of new laterals was highest in the first half of the cold season. High lateral densities suppressed new lateral initiation. In the first month after initiation, laterals grew out to the same length as those formed earlier in the year. Thus, elongation rates of young laterals were highest during the period of maximum canopy height. In older laterals, growth rates decreased with length, due to increased tissue loss. Growth rates were independent of reproductive status. Reproduction occurred in the second half of the cold season and was independent of lateral size, but laterals had to be at least 1 to 2 mo old before reproducing. Highest loss rates of laterals occurred at the end of the growth season. Survivorship was independent of lateral size or reproductive status. Loss rates were lowest in the hot season. We conclude that there is no direct trade-off between reproduction and growth/survival of the laterals, and that the dynamics of S. ilicifolium are directly related to the seasonal extremes in environmental conditions. Morphogenetic responses at the level of individual laterals also contribute to the overall phenological pattern.

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Section: Effects Of Lateral Densitysupporting

confidence: 70%

“…Growth rates of shoots of large canopy algae have been reported either as absolute growth rates (= elongation rates) (e.g. De Ruyter van Steveninck & Breeman 1987, Viejo & Åberg 2001 or as relative growth rates (RGR) (e.g. Schaffelke & Klumpp 1997).…”

Section: Methodsmentioning

confidence: 99%

Seasonal dynamics of Sargassum ilicifolium (Phaeophyta) on a shallow reef flat in the southern Red Sea (Eritrea)

Ateweberhan¹,

Bruggemann²,

Breeman³

2005

Mar. Ecol. Prog. Ser.

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“…Both L. scutulata and L. obtusata have radulae with shovel-like cusps (Reid 1996) that make them capable of excavating tissue from the surface of large leathery seaweeds such as fucoids (Steneck and Wating 1982;Voltolina and Sacchi 1990), which weakens the seaweed shoots and makes them more prone to breakage (cf. Viejo and Åberg 2001). Mesoherbivores are a large and heterogeneous group of animals, and their eVects on seaweed Wtness are probably highly dependent on the mode of herbivore feeding.…”

Section: Discussionmentioning

confidence: 99%

Mesoherbivores reduce net growth and induce chemical resistance in natural seaweed populations

Toth¹,

Karlsson²,

Pavia³

2007

Oecologia

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Herbivory on marine macroalgae (seaweeds) in temperate areas is often dominated by relatively small gastropods and crustaceans (mesoherbivores). The effects of these herbivores on the performance of adult seaweeds have so far been almost exclusively investigated under artificial laboratory conditions. Furthermore, several recent laboratory studies with mesoherbivores indicate that inducible chemical resistance may be as common in seaweeds as in vascular plants. However, in order to further explore and test the possible ecological significance of induced chemical resistance in temperate seaweeds, data are needed that address this issue in natural populations. We investigated the effect of grazing by littorinid herbivorous snails (Littorina spp.) on the individual net growth of the brown seaweed Ascophyllum nodosum in natural field populations. Furthermore, the capacity for induced resistance in the seaweeds was assessed by removing herbivores and assaying for relaxation of defences. We found that ambient densities of gastropod herbivores significantly reduced net growth by 45% in natural field populations of A. nodosum. Seaweeds previously exposed to grazing in the field were less consumed by gastropod herbivores in feeding bioassays. Furthermore, the concentration of phlorotannins (polyphenolics), which have been shown to deter gastropod herbivores, was higher in the seaweeds that were exposed to gastropod herbivores in the field. This field study corroborates earlier laboratory experiments and demonstrates that it is important to make sure that the lack of experimental field data on marine mesoherbivory does not lead to rash conclusions about the lack of significant effects of these herbivores on seaweed performance. The results strongly suggest that gastropods exert a significant selection pressure on the evolution of defensive traits in the seaweeds, and that brown seaweeds can respond to attacks by natural densities of these herbivores through increased chemical resistance to further grazing.

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“…1;Collado-Vides 2002a;Santelices 2004). By aggregating photosynthetic tissue in favorable habitats or limiting growth in unfavorable ones, seaweeds may forage for resources analogously to clonal plants (Viejo and Å berg 2001;Arenas et al 2002;Collado-Vides 2002b). Despite such ecological parallels, however, the evolution of morphological plasticity in clonal seaweeds has rarely been evaluated from a clonal plant perspective (Collado-Vides 2002a; Santelices 2004).…”

Section: Introductionmentioning

confidence: 97%

Multivariate selection shapes environment-dependent variation in the clonal morphology of a red seaweed

2007

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Within-individual strategies of variation (e.g., phenotypic plasticity) are particularly relevant to modular organisms, in which ramets of the same genetic individual may encounter diverse environments imposing diverse patterns of selection. Hence, measuring selection in heterogeneous environments is essential to understanding whether environment-dependent phenotypic change enhances the fitness of modular individuals. In sublittoral marine habitats, competition for light and space among modular taxa generates extreme patchiness in resource availability. Little is known, however, of the potential for plasticity within individuals to arise from spatially-variable selection in such systems. We tested whether plasticity enhances genet-level fitness in Asparagopsis armata, a clonal seaweed in which correlated traits mediate morphological responses to variation in light. Using the capacity for rapid, clonal growth to measure fitness, we identified aspects of ramet morphology targeted by selection in two contrasting light environments and compared patterns of selection across environments. We found that directional selection on single traits, coupled with linear and nonlinear selection on multi-trait interactions, shape ramet morphology within environments and favor different phenotypes in each. Evidence of environment-dependent, multivariate selection on correlated traits is novel for any marine modular organism and demonstrates that seaweeds, such as A. armata, may potentially adapt to environmental heterogeneity via plasticity in clonal morphology.

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Effects of density on the vital rates of a modular seaweed

Cited by 24 publications

References 61 publications

Seasonal dynamics of Sargassum ilicifolium (Phaeophyta) on a shallow reef flat in the southern Red Sea (Eritrea)

Seasonal dynamics of Sargassum ilicifolium (Phaeophyta) on a shallow reef flat in the southern Red Sea (Eritrea)

Mesoherbivores reduce net growth and induce chemical resistance in natural seaweed populations

Multivariate selection shapes environment-dependent variation in the clonal morphology of a red seaweed

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