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Abstract Phenology, or seasonal variation in life cycle events, is poorly described for many macroalgal species. We describe the phenology of a non‐native population ofGracilaria vermiculophyllawhose thalli are free‐living or anchored by decorating polychaetes to tube caps. At a site in South Carolina, USA, we sampled 100 thalli approximately every month from January 2014 to January 2015. We assessed the reproductive state and measured thallus size based on wet weight, thallus length, and thallus surface area from herbarium mounts. Because life cycle stage cannot be assigned using morphology, we implemented a PCR assay to determine the life cycle stage—tetrasporophyte, female gametophyte, or male gametophyte—of each thallus. Tetrasporophytes dominated throughout the year, making up 81%–100% of thalli sampled per month. Reproductive tetrasporophytes varied between 0% and 65% of monthly samples and were most common in warm summer months (July through September) when thalli also tended to be larger. The vast majority of the reproductive thalli were worm‐anchored and not fixed to hard substratum via a holdfast. Thus, free‐living thalli can be reproductive and potentially seed new non‐native populations. GivenG. vermiculophyllareproduction seems tied closely to temperature, our work suggests phenology may change with climate‐related changes in seawater temperatures. We also highlight the importance of understanding the natural history of macroalgae to better understand the consequence of range expansions on population dynamics.
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Ontogenetic Variation in Blade Toughness May Contribute to the Spread of Turbinaria ornata Across the South Pacific
Coral reefs are shifting from coral to algal-dominated ecosystems worldwide. Recently, Turbinaria ornata, a marine alga native to coral reefs of the South Pacific, has spread in both range and habitat usage. Given dense stands of T. ornata can function as an alternative stable state on coral reefs, it is imperative to understand the factors that underlie its success. We tested the hypothesis that T. ornata demonstrates ontogenetic variation in allocation to anti-herbivore defense, specifically that blade toughness varied nonlinearly with thallus size. We quantified the relationship between T. ornata blade toughness and thallus size for individual thalli within algal stands (N=345) on 7 fringing reefs along the north shore of Moorea, French Polynesia. We found that blade toughness was greatest at intermediate sizes that typically form canopies, with overall reduced toughness in both smaller individuals that refuge within the understory and older reproductive individuals that ultimately detach and form floating rafts. We posit this variation in blade toughness reduces herbivory on the thalli that are most exposed to herbivores and may facilitate reproduction in dispersing stages, both of which may aid the proliferation of T. ornata.
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- Award ID(s):
- 1823461
- PAR ID:
- 10389927
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Journal of Phycology
- ISSN:
- 0022-3646
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1111/jpy.13292
