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Asexual propagation in the coral reef macroalga Halimeda (Chlorophyta, Bryopsidales): production, dispersal and attachment of small fragments

Asexual propagation in the coral reef macroalga Halimeda (Chlorophyta, Bryopsidales): production, dispersal and attachment of small fragments,10.1016/

Asexual propagation in the coral reef macroalga Halimeda (Chlorophyta, Bryopsidales): production, dispersal and attachment of small fragments   (Citations: 18)
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Siphonous, green macroalgae of the genus Halimeda are ubiquitous and ecologically important in tropical and subtropical marine environments. It has been hypothesized that the abundance of Halimeda on coral reefs is in part due to the ability of this genus to propagate asexually via vegetative fragmentation. However, vegetative fragmentation has only been documented for H. discoidea in a laboratory setting. To test the hypothesis that vegetative fragmentation contributes to field populations of Halimeda, we examined three aspects of fragmentation by H. tuna (Ellis and Solander) Lamouroux, H. opuntia (Linneaus) Lamouroux and H. goreaui Taylor on Conch Reef in the Florida Keys: (1) short-term (8 days) and long-term (14 weeks) fragment survival and rhizoid production in the laboratory and field (7 and 21 m), (2) size of the fragment pool and (3) influences of herbivory and water motion on production and dispersal of fragments. Although morphologically similar to H. discoidea, only a small percentage of H. tuna fragments survived. Fragments of H. opuntia and H. goreaui were more robust, and survival and rhizoid production were positively correlated with size in short-term trials. In 14-week field trials, one-third or fewer fragments of any species survived at 7 m, potentially because fragments were covered by large amounts of sediment. Survivors included some buried, seemingly dead individuals that turned green when exposed to light, highlighting the remarkable ability of this genus to survive disturbances. There was much less sediment accumulation at 21 m, where more fragments survived. Most (93%) eight-segment fragments of H. opuntia produced attachment rhizoids by the end of the 14-week trial. Overall, a range of 4.7–9.4 fragments of Halimeda m−2 day−1 were found on Conch Reef; most fragments were generated by H. goreaui. Fish bite marks were evident on 75–85% of the individuals of H. tuna and the number of bites per thallus ranged from 1 to 23. Herbivorous reef fish commonly fed on all three species of Halimeda. Some fish consumed the biomass, while others rejected most bites. For example, 83% of bites were rejected by the blue-striped grunt. Dispersal distances for rejected bites ranged from 0 to 31 m. Water motion was also responsible for fragment dispersal; experimentally produced fragments moved up to 48 cm day−1. Results presented here suggest that asexual propagation of fragments of Halimeda is an important component of the life-history of this genus and vegetative fragmentation contributes to the abundance of this genus on coral reefs.
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    • ...Additionally, the ecomorphology of successful reef algae is also an important driver of algal success on reefs, but has received relatively little attention (but see Collado-Vides et al. 1998; Walters et al. 2002; Anderson et al. 2006)...

    Hannah L. Stewart. The role of spatial and ontogenetic morphological variation in the exp...

    • ...Halimeda is able to reproduce asexually via vegetative fragmentation (Walters et al. 2002)...

    Maggy M. Nugueset al. Coral settlement onto Halimeda opuntia : a fatal attraction to an ephe...

    • ...Walters et al. (2002), who documented similar fish biting rates on H. tuna...
    • ...Similarly, the mean biting rate for the redband parrotfish at 21 m was 3.1±0.4 and 2.7±0.3 for Dictyota and Halimeda, respectively (Walters et al. 2002)...

    L. W. Herrenet al. Fragment generation, survival, and attachment of Dictyota spp. at Conc...

    • ...In order to reduce genetic differences, this study focused on two populations close enough for the possible exchange of genetic information via asexual fragmentation (Walters & Smith, 1994; Walters et al., 2002), but environmentally distinct enough to display different physiological responses...
    • ...Photosynthesis (Beach et al., in press), asexual fragmentation (Walters et al., 2002), and nutrient physiology (Smith et al., in review) of H. tuna populations at each site were also examined...
    • ...Settlement of asexual fragments of Halimeda produced from fish bites and physical disturbance (Walters & Smith, 1994; Walters et al., 2002), or new plants produced at the end of rhizoidal runners (Meinesz, 1980b, but see Drew & Abel, 1988b), can quickly boost plant numbers without sexual reproduction...

    Peter S. Vroomet al. Field biology of Halimeda tuna (Bryopsidales, Chlorophyta) across a de...

    • ...In order to reduce genetic differences, this study focused on two populations close enough for the possible exchange of genetic information via asexual fragmentation (Walters & Smith, 1994; Walters et al., 2002), but environmentally distinct enough to display different physiological responses...
    • ...Photosynthesis (Beach et al., in press), asexual fragmentation (Walters et al., 2002), and nutrient physiology (Smith et al., in review) of H. tuna populations at each site were also examined...
    • ...Settlement of asexual fragments of Halimeda produced from fish bites and physical disturbance (Walters & Smith, 1994; Walters et al., 2002), or new plants produced at the end of rhizoidal runners (Meinesz, 1980b, but see Drew & Abel, 1988b), can quickly boost plant numbers without sexual reproduction...

    Peter S. Vroomet al. Field biology of Halimeda tuna (Bryopsidales, Chlorophyta) across a de...

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