Browsing by Author "Santelices, B"

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    A dichotomous species of Codium (Bryopsidales, Chlorophyta) is colonizing northern Chile
    (2004) González, A; Santelices, B
    In late 2001 and early 2002, a dichotomous species of Codium appeared colonizing the low intertidal and shallow subtidal bottoms of Caldera Bay, northern Chile (27degrees03' S, 70degrees51' W). Due to the ecological and economic impact the species is having in Caldera Bay and its potential spread along the Chilean coastline, we studied the taxonomic identity of the species and examined its relationships with other dichotomous species of Codium reported for temperate Pacific South America. Morphological analyses suggest that the seaweeds from Caldera Bay belong to Codium fragile (Suringar) Hariot. Not only is there strong agreement in internal and external morphological characters, but among all the species reported for Peru and Chile, this is the only one exhibiting utricles with rounded, apiculate tip terminating in a mucron. This species has a broad geographic distribution in temperate waters. In Chile it was known only from the coasts of Valdivia to the Straits of Magellan (39degrees48' S, 73degrees26' W to 53degrees10' S, 73degrees49' W). This is the first record of C. fragile in northern Chile, and this study discusses several alternative hypotheses for the presence of the species into this area. The morphological characteristics of the material collected in Caldera partially agree with diagnostic characters known for C. fragile subspecies tasmanicum and C. fragile subspecies tomentosoides. However, the rapid population spread of the species in northern Chile, and recent molecular analysis support the identification of this form as the invasive C. fragile subspecies tomentosoides.
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    Growth-related intraclonal genetic changes in Gracilaria chilensis (Gracilariales: Rhodophyta)
    (1999) Meneses, I; Santelices, B; Sánchez, P
    Gracilaria ia chilensis exhibits noticeable intraclonal variation, some of which is presumed to result from mitotic recombinations or other types of DNA turnover associated with replication activities during cellular division. To test this, genetic variability (determined by multilocus fingerprinting markers using the randomly amplified polymorphic DNA technique, RAPD) and total growth were simultaneously measured over time in clonal replicates of G. chilensis incubated under controlled laboratory conditions. The results suggest that genetic variability increases as growth occurs and biomass accumulates, supporting the hypothesis of growth-related increases in genetic heterogeneity. For species massively propagated by thallus fragmentation in either naturally or farmed populations, growth-dependent genetic changes may constitute a powerful means of generating intra-population variation without thalli becoming reproductively mature, and, as a, consequence, bypassing meiosis and/or sexual recombination.
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    Nomenclature and typification of Gelidiella tenuissima (Gelidiales, Rhodophyta)
    (2002) Santelices, B; Rico, JM
    The nomenclature and the type material of the entity presently known as Gelidiella pannosa (Feldmann) Feldmann & Hamel are considered. It is concluded that G. tenuissima Feldmann & Hamel is the correct name for the species lectotypified by the specimen located in the lower left corner of the herbarium sheet 7913802 of Herb, Thuret (PC, Paris), collected in Biarritz. France, on 25 June 1868. The following names are considered synonyms of G. tenuissima: Gelidium tenuissimum Thuret, G. pannosum Bornet non Grunow, G. pannostem Weber van Bosse, Echinocaulon pannosum Feldmann, Gelidiella pannosa (Bornet) Feldmann & Hamel, G pannosa (Feldmann) Feldmann & Hamel, and G. tenuissima (Thuret) Feldmann & Hamel. Syntypes of this species are found in the Thuret Herbarium (PC, Paris) and in Holmes' Herbarium at the British Museum London.
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    Selective mortality on haploid and diploid microscopic stages of Lessonia nigrescens Bory (Phaeophyta, Laminariales)
    (1998) Martinez, EA; Santelices, B
    In seaweeds, potential selective events on juveniles are particularly important because the highest mortality rates usually affect these microscopic stages rather than the macroscopic ones. This study evaluates the degree to which the mortality induced by herbivory and wave impact are selective on the size (mean and whole distribution) of haploid, gametophytic, and of diploid, early sporophytic stages of the intertidal kelp Lessonia nigrescens. In theory, in species with a complex life history, the potential effect of selective mortality on haploid and diploid individuals may range between two extremes. One of inhibition, where the same feature, conferring higher survival in one phase, may cause the opposite effect in the following phase. The other extreme is synergism, where selection operates similarly among the two alternating Life history phases. Controlled experiments showed that herbivorous snails had a more significant negative impact on haploid gametophytes than on the slightly larger, diploid, sporophytes. Conversely, separate experiments showed that wave impact eliminated more efficiently the larger diploid plantules than the smaller haploid ones. Size selectivity by both mortality agents occurred only on the microscopic diploid stages, when plantule sizes were longer than 20 mu m. Directionality of selection indicated that larger individuals, with more developed adhesive rhizoids, had higher survival rates. The directional selection on diploid plants is neither reinforced, or cancelled out, in the alternate haploid stages. Thus, no inhibitory or synergetic effects were observed for the directional selection of size between these two Life history phases. These results suggest that, compared to organisms with direct life cycles, those having complex life histories, with independent phases, have at least one more restriction for the occurrence of evolutionary change. Namely, that of equivalent expression and response of involved traits on both alternate haploid and diploid phases to the same putative selective agents. (C) 1998 Elsevier Science B.V. All rights reserved.
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    Strain selection and genetic variation in Gracilaria chilensis (Gracilariales, Rhodophyta)
    (1999) Meneses, I; Santelices, B
    Strain selection processes in seaweed often have assumed that sterile clones could be maintained for long periods in a diversity of environments without major genetic changes. However, clonal species such as Gracilaria chilensis exhibit intra-clonal variation in performance and ongoing studies suggest such changes may be due to rapid changes in DNA composition associated with growth, via mitotic recombinations. Therefore performance of a given ramet in this type of seaweed should be understood as the dynamic outcome of rapid reactions between the environment and the changing genotype of the selected strain. To evaluate this idea, we measured changes in genetic variability, as detected by DNA-fragment polymorphism using RAPDs-PCR, exhibited by clones of G. chilensis after two transfers to different environmental conditions (from field to controlled laboratory conditions and from the laboratory to large-scale tank culture). The transfer to laboratory conditions reduced the frequency of low similarity values and increased the frequency of intermediate similarity values in DNA banding patterns, suggesting the branchlets produced under controlled laboratory conditions have less genetic variability (evaluated as total DNA polymorphism) than plants recently collected in the field. Tank incubation reduced the total range of similarity and significantly increased the frequency of high similarity values. Results thus suggest the dynamic of genetic changes in vegetative clones of Gracilaria chilensis that is fast and strongly affected by the external environment.