Browsing by Author "Santelices, Bernabe"

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    Hierarchical analysis of reproductive potential in Mazzaella laminarioides (Gigartinaceae, Rhodophyta)
    (1997) Santelices, Bernabe; Martinez, Enrique A.
    Estimations of reproductive effort in seaweeds are important for evaluation of the effects of ecological parameters on fitness as well as for prediction of colonization capacity and competitive potential. Such estimations must consider several levels of resolution. At the coarsest scale of analysis, fertile blade abundance must be Measured. At a finer level of analysis, cystocarps and tetrasporangial sori must be quantified within blade Populations. At the finest level of analysis, the condition of the spores, including their size, stage of maturation, and germination potential Should be considered. This study tests whether the integration of these various scales of analysis into a single algorithm might improve the estimations Of reproductive potential. Application of this analysis to populations of Mazzaella laminarioides (Bory) Fredericq revealed new patterns of distribution at the three hierarchical levels analyzed and new trends across hierarchical levels. The pattern of distribution of fertile blades in the field is characterized by high spatial and seasonal heterogeneity. The size structure of fertile blades revealed a minimum size necessary to achieve reproductive maturity, and the density per unit area of cystocarpic and tetrasporangial sori was higher in larger blades than in smaller ones. No clear pattern of maturation of reproductive was found within blades when sampled along axes from apex to base and from side to side. At the finest level of analysis. it was found that variation in color of reproductive bodies correlated with different spore morphologies and germination rates, thus suggesting a maturation trend. The resulting algorithm used to estimate reproductive potential integrated information from all three levels of analysis. Reduction of variability by making assumptions of homogeneous germination potential, homogeneous blade sizes, or homogeneous spatio-temporal distribution significantly influenced estimates of the number of spores produced per unit area of habitat.
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    IDENTIFICATION OF CRYPTIC SPECIES IN THE LESSONIA NIGRESCENS COMPLEX (PHAEOPHYCEAE, LAMINARIALES)
    (WILEY, 2012) Gonzalez, Alejandra; Beltran, Jessica; Hiriart Bertrand, Luciano; Flores, Veronica; de Reviers, Bruno; Correa, Juan A.; Santelices, Bernabe
    The kelp Lessonia nigrescens Bory is the most ecologically and economically important seaweed in rocky intertidal and shallow subtidal habitats along the temperate Pacific South American coasts. Recent molecular studies suggest the existence of two lineages, one (northern lineage) from 17 degrees S to 30 degrees S and a second (central lineage) from 29 degrees S to 41 degrees S. To identify and name these lineages we performed morphological, nomenclatural and field studies. Four external and three internal anatomical traits permitted a morphological separation of the two lineages. The internal structure of both lineages was different from the isolectotype of Lessonia nigrescens. It is therefore concluded that the name Lessonia nigrescens should not be used for the Chilean material. Chordaria spicata Suhr appears as the oldest available name for the central lineage, while Lessonia berteroana Montagne is the oldest name for the northern lineage. In both cases, the type material consisted of small-sized, apical branches of larger plants. The new combination Lessonia spicata (Suhr) Santelices is proposed for the central lineage and we reinstate Lessonia berteroana for the northern lineage. Laminaria scissa Suhr is reduced to synonym of L. spicata. Representative specimens of Lessonia nigrescens were not found during new visits to its type locality in Cape Horn and along Chile. Future studies should verify the status of this species.
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    Morphological convergence in the inter-holdfast coalescence process among kelp and kelp-like seaweeds (Lessonia, Macrocystis, Durvillaea)
    (2015) Gonzalez, Alejandra V.; Beltran, Jessica; Flores, Veronica; Santelices, Bernabe
    In brown macroalgae, intraspecific holdfast coalescence has only been studied in two species of Lessonia (Lessonia spicata and Lessonia berteroana). In both species coalescence followed the same general pattern: once the connection between holdfasts was established, the contact areas showed significant cellular morphological modifications. Typical epidermal cells became polygonal and similar to cortical cells. In addition, coalescence involved the de novo formation of secondary plasmodesmata, establishing a direct cytoplasm connection within neighbouring cells, where dense materials, vacuoles and organelles can be observed. In the present study, we demonstrate intraspecific holdfast coalescence in two additional kelp species, Lessonia trabeculata and Macrocystis pyrifera, as well as in the kelp-like seaweed, Durvillaea antarctica. The process of holdfast fusions in these species is similar to that described previously and suggests that this is a generalized phenomenon among kelp and kelp-like brown algae. In addition, the formation of cytoplasmic connections between genetically different brown algal individuals is shown for the first time.
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    SIZE INCREMENTS DUE TO INTERINDIVIDUAL FUSIONS: HOW MUCH AND FOR HOW LONG?1
    (2010) Santelices, Bernabe; Alvarado, Jorge L.; Flores, Veronica
    Size increments following interindividual fusions appear as a general benefit for organisms, such as coalescing seaweeds and modular invertebrates, with the capacity to fuse with conspecifics. Using sporelings of the red algae Gracilaria chilensis C. J. Bird, McLachlan et E. C. Oliveira and Mazzaella laminarioides (Bory) Fredericq, we measured the growth patterns of sporelings built with different numbers of spores, and the magnitude and persistence of the size increments gained by fusions. Then we studied three morphological processes that could help explain the observed growth patterns. Results indicate that in these algae, coalescence is followed by immediate increase in total size of the coalesced individual and that the increment is proportional to the number of individuals fusing. However, the size increments in sporelings of both species do not last > 60 d. Increasing reductions of marginal meristematic cells and increasing abundance of necrotic cells in sporelings built with increasing numbers of initial spores are partial explanations for the above growth patterns. Since sporelings formed by many spores differentiate erect axes earlier and in larger quantities than sporelings formed by one or only a few spores, differentiation, emergence, and growth of erect axes appear as a more likely explanation for the slow radial growth of the multisporic sporelings. Erect axis differentiation involves significant morphological and physiological changes and a shift from radial to axial growth. It is concluded that the growth pattern exhibited by these macroalgae after fusion differs from equivalent processes described for other organisms with the capacity to fuse, such as modular invertebrates.
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    Spatial and temporal variation of photosynthesis in intertidal Mazzaella laminarioides (Bory)Fredericq (Rhodophyta, Gigartinales)
    (2006) Varela, Daniel A.; Santelices, Bernabe; Correa, Juan A.; Arroyo, Mary K.
    The red alga Mazzaella laminarioides is an economically important species with an extended latitudinal distribution along the Chilean coast. Its populations form mid-intertidal stands, several meters wide, and therefore are differentially exposed to environmental variables that result in temporal and spatial variability in productivity. We evaluated the effect of latitude and intertidal height on productivity by in situ measurement of photosynthetic performance. Daily and seasonal variations of O-2-evolution rate and maximal quantum yield (F (v)/F (m)) were determined in plants from the upper and lower intertidal zone at two localities 1500,km apart. Results suggest that plant responses were mainly affected by irradiation, temperature and desiccation. At local level, upper intertidal plants showed a reduced photosynthetic rate and quantum efficiency as compared to those displayed by plants from the lower intertidal, indicating their higher level of excitation energy acclimation. Stronger acclimation differences between upper and lower intertidal plants were observed in spring and summer. Differences in photosynthetic parameters between reproductive phases were recorded in autumn and winter, regardless of the position of the individuals in the intertidal zone. The effects of tidal elevation on seasonal patterns of photosynthesis were also influenced by latitude. Seasonal variation in photosynthetic efficiency was observed in plants from the northern population at both intertidal elevations, but only at the upper intertidal level in the southern population. This study shows that production variability in M. laminarioides results from differences in the intensity of environmental factors observed seasonally at local (intertidal) and latitudinal scales.