Macrocystis es el alga parda dentro del orden Laminariales que posee las mas amplia distribucion, encontrandose en las costas temperadas de America del Norte y Sur, tambien en Argentina, Sudafrica, Australia, Nueva Zelandia y gran parte de las islas Subantarcticas. A pesar de gran importancia ecologica y economica, su filogenia, taxonomia y patrones de dispersion se encuentran muy poco estudiados. Utilizando diversos marcadores moleculares, estudiare la conectividad, filogeografia y patrones de dispersion en Macrocystis. Para ello realizare una aproximacion global, pero con un mayor enfoque en las costas de Chile y Nueva Zelandia. (ver más)

The brown alga Macrocystis C. Agardh is widely distributed throughout the cold temperate waters of the Northern and Southern hemispheres, forming ecologically diverse and productive kelp forests. The taxonomy of this alga has been under constant discussion. Since the first description, species have been mostly described by holdfast and blade morphology; however, the importance of these taxonomic characters has been questioned. Based on a morphological study, the genus has recently been synonymized into a single species, M. pyrifera (L.) C. Agardh, but additional genetic evidence is still lacking. Using the “DNA-barcoding” gene (COI), we examined the taxonomy of Macrocystis collected from 19 sites worldwide, covering the distribution of the four ecomorphs (M. “pyrifera,” M. “angustifolia”, M “integrifolia”, and M. “laevis”). Our molecular data strongly support the recognition of a single species; therefore, the genus should contain only one species, M. pyrifera, the oldest name. Results also reveal shared haplotypes in several distant sites around the Southern Hemisphere and very low variability among samples. Additionally, samples of the ecomorphs M. “integrifolia” and M. “pyrifera” from a sympatric population in California had the same haplotype. The revised taxonomy changes questions of Macrocystis distribution from interspecific dispersal and evolutionary questions to intraspecific ecological questions on the maintenance of Macrocystis in certain environments that produce particular morphologies.

We assessed the genetic structure of the giant kelp Macrocystis pyrifera across a broad latitudinal range along the southeastern Pacific coast (SEP). Specifically we analyzed the concordance of putative biogeographic breaks with genetic discontinuities and the effect of historical and contemporary events on the genetic pattern of this important seaweed. Mitochondrial DNA and single-strand DNA conformation polymorphism (SSCP) analysis for a total of 730 samples were carried out. Only 5 haplotypes were found among individuals collected along 4800 km of coastline, with very low haplotype diversity and a shallow genealogy compared with other macroalgal species. Some phylogeographic disjunctions in M. pyrifera were found to correspond roughly to established biogeographic breaks. On the southern coast we found a genetic break at 42°S (Chiloé Island) coincident with a well-known biogeographic boundary, while the genetic break found between samples in central/northern Chile (33°S) does not correspond to any known biogeographic breaks in other brown algae, but does reflect a break associated with other marine taxa. The low genetic diversity in northern Chile may be related to contemporary events (e.g. El Niño Southern Oscillation) while in southern Chile the haplotype distribution may reflect the effect of historical events (Last Glacial Maximum; LGM). Additionally, we compared the SEP data with samples from some of the subantarctic islands and New Zealand. The results showed shared haplotypes among some of the subantarctic islands and southern-central Chile, suggesting a recent colonization of the subantarctic region. The high dispersal potential of kelp rafts may also help to explain the low genetic diversity observed. We conclude that both present and historic events are responsible for the genetic structure of M. pyrifera along the SEP.

Numerous experimental studies have reported inducible defenses in macroalgae, but most of them have been conducted in laboratory environments where algae were maintained detached from the substratum and in artificial flow regimes. The results of those experiments might not reflect the natural situation, which can only be studied in situ. We examined whether the brown macroalgae Dictyota kunthii (C. Agardh) Greville and Macrocystis integrifolia (Bory) show inducible defenses following exposure to different grazing levels (direct, water-borne cues from nearby grazed conspecifics, presence of a non-grazing herbivore and natural grazing) in field experiments, striving to maintain natural conditions as much as possible. We measured palatability of algae after exposure to different grazing levels by using live algae and agar-based food containing non-polar extracts. Macrocystis integrifolia showed no induction of defenses (at least not of non-polar compounds), suggesting constitutive defenses, absence of defenses (tolerance) or use of another strategy to avoid herbivory. These results are similar to those from previous laboratory experiments. In Dictyota kunthii, defense was induced after two weeks of direct grazing by amphipods under field conditions. Water-borne cues from nearby grazed conspecifics, presence of a non-grazing herbivore and natural grazing did not induce defenses. Induction of defense in response to direct grazing agrees with results from a previous laboratory study, but while indirect cues induced defenses in the laboratory, there was no measurable induced defense in the field. Probably chemical cues from grazers are diluted quickly in the field, not reaching concentrations that cause induction of defenses. This might be the reason why in some algae induction by direct grazing is a more important defensive strategy than induction by water-borne cues. The results from our study also suggest that laboratory experiments showing induced defenses in response to grazed neighbours or mere grazer presence need to be interpreted with caution.

Chondracanthus chamissoi is a red alga which is acquiring an increasing economic importance in Chile and becoming a target species for cultivation. Considering that epiphytism is a major problem in the mariculture of seaweeds, the recruitment of Ulva sp. and Enteromorpha sp. on gametophytic (cystocarpic) and tetrasporophytic thalli of C. chamissoi was tested in vitro on four populations from different locations in Chile. For Ulva sp. the density, cover and length of the recruits varied between the reproductive phases of the host and among the studied populations of C. chamissoi . In most experiments a larger number of epiphytic thalli was observed on gametophytic plants of C. chamissoi ; populations from Calderilla and Lechagua had a higher resistance to epiphytism. For Enteromorpha sp. its ability to grow epiphytically on both phases of the host showed a greater variability, but was inferior than that of Ulva sp. The differential resistance to epiphytism in both reproductive phases and in plant origin indicates the possibility of obtaining selected strains of C. chamissoi with lower susceptibility to epiphytism to be utilized in planning maricultural programs.

Hinojosa I., Boltaña S., Macaya E., Ugalde P., Valdivia N., Vásquez N., Newman W. & Thiel M. 2006. Zoogeography of four pelagic barnacles within the SE-Pacific coast of Chile. Revista Chilena de Historia Natural. 78: 603-614. (WWW)

Macroalgae can defend themselves against generalist and specialist herbivores via morphological and/or chemical traits. Herein we examined the defensive responses (via relative palatability) of two brown (Lessonia nigrescens , Glossophora kunthii) and two red algae (Grateloupia doryphora , Chondracanthus chamissoi) from the northern-central coast of Chile against selected generalist meso-herbivores. Two laboratory experiments were conducted to investigate whether (i) algae can respond generally to grazing pressure of meso-herbivores (amphipods, isopods and juvenile sea urchins) and whether (ii) these algal responses were inducible. In order to examine palatability and thus effectiveness of responses, feeding assays were run after each experiment using fresh algal pieces and artificial agar-based food. Lessonia nigrescens responded to amphipods but not to sea urchins, and G. kunthii showed inducible response against one species of amphipods. Grateloupia doryphora did not respond against any of the tested grazers, whereas C. chamissoi responded against one species of amphipods and the tested isopod. Our results indicate variable responses of macroalgae against selected generalist meso-herbivores and evidence of an inducible defense in the brown alga G. kunthii.

Macaya E., Boltaña S., Buschmann A., Hinojosa I., Macchiavello J., Valdivia N., Vásquez N., Vásquez J., Vega J. & Thiel M. 2005. Presence of sporophylls in floating kelp rafts of Macrocystis spp. (Phaeophyceae) along the Chilean Pacific Coast. Journal of Phycology. 41: 913-922. (PDF)

Some species of macroalgae continue to live for extended periods of time after detachment and may even maintain reproductive structures, yet very little is known about this process. Here, we describe the presence of sporophylls (with sporogenous tissues) on floating kelp rafts of Macrocystis spp. along the coast of Chile. Surveys were conducted at nine sites (18–50° S) during austral summer 2002, and floating kelp rafts were seen and collected at seven of these nine sites (between 22 and 50° S). Fifteen (26.8%) of the 56 samples had sporophylls, indicating maintenance of sporophylls after detachment. Some of the kelp sporophytes with reproductive blades showed signs of having been afloat for long periods (indicated by the large size of attached stalked barnacles). Additionally, experiments showed that floating kelps released viable zoospores. To understand the reproductive dynamics of floating kelps, we compared these results with information from attached populations of Macrocystis spp. at nearby coastal sites. In general, attached kelp had higher proportions of sporophylls than floating rafts, suggesting that detachment may negatively affect reproductive status. Nevertheless, floating kelps remained functionally reproductive, suggesting that zoospores may be dispersed via floating rafts. Published reports on other macroalgae indicate that some species (Lessoniaceae, Fucaceae, and Sargassaceae) are fertile and probably release zoospores or zygotes while floating or drifting in ocean currents. Because dispersal distances achieved by spores of most macroalgae are relatively short, release of spores from floating algae may be an alternative mechanism of long-distance dispersal.