A dichotomous species of Codium (Bryopsidales, Chlorophyta) is colonizing northern Chile Una especie dicotómica de Codium (Bryopsidales, Chlorophyta) está colonizando el norte de Chile

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 (27° 03’ S, 70° 51’ 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 (39° 48’ S, 73° 26’ W to 53° 10’ S, 73° 49’ 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 tomentosoidesA fines de 2001 y principio de 2002, apareció en el norte de Chile una especie del género Codium, de morfología dicotómica, colonizando los niveles intermareales y submareales de la Bahía de Caldera (27° 03’ S, 70° 51’ O). Debido al impacto ecológico y económico que ha provocado esta especie en la Bahía de Caldera y a su dispersión potencial a lo largo de la costa de Chile, estudiamos la identidad taxonómica de la especie, examinando su relación con las especies de Codium de hábito erecto descritas para la costa temperada del Pacífico Sudamericano. El análisis morfológico sugiere que el alga encontrada en la Bahía de Caldera corresponde a la especie Codium fragile (Suringar) Hariot. Tanto los caracteres morfológicos internos como externos del alga, son concordantes con la descripción de la especie, incluyendo utrículos de ápices redondeados apiculados terminados en un mucron puntiagudo. Esta especie posee una amplia distribución geográfica en aguas temperadas. En Chile, es conocida sólo para las costas entre Valdivia y Magallanes (39° 48’ S, 73° 26’ O a 53° 10’ S, 73° 49’ O). Este es el primer registro de C. fragile en el norte de Chile y además, este estudio discute diversas hipótesis alternativas de introducción de la especie en el área. Las características morfológicas de los materiales colectados en Caldera concuerdan parcialmente con los caracteres diagnósticos conocidos para C. fragile subespecies tasmanicum y C. fragile subespecies tomentosoides. Sin embargo, la expansión poblacional rápida que la especie está mostrando en Chile norte junto con análisis moleculares recientes apoyan la identificación de estas poblaciones como pertenecientes a la subespecie tomentosoide

Banks of microscopic forms and survival to darkness of propagules and microscopic stages of macroalgae Bancos de formas microscópicas y supervivencia a la oscuridad de propágulos y formas microscópicas de macroalgas

Previous studies have found that the number of species conforming a bank of microscopic forms in tide pools in central Chile accounted only for half the number of species present in the macroscopic vegetation around the pools. An elemental condition for survival in these banks is the ability of microscopic forms to tolerate darkness or very low irradiances for extended periods. To test this ability, spores of 17 green, brown and red algal species, present and absent from the bank, were incubated at different combinations of irradiances and day lengths. Propagules of 47 % of the species tested (eight species) germinated in total darkness while the propagules of the other nine species germinated under conditions of very low irradiance (2-10 µmol m-2 s-1). In most species, microforms showed a higher tolerance to darkness than the propagules. Some survived for over a year and one species (Gelidium lingulatum) could live under complete darkness for 500 days. The ability to survive in total darkness did not relate to presence or absence of a species in the banks of microscopic forms previously studied, to phylogenetic relatedness, life history style, propagule size, morphology of microscopic forms or to successional status (fugitive versus late successional). Thus, tolerance to darkness appears to be common to propagules and microscopic stages of most benthic algae. The growth patterns exhibited by the microforms of Lessonia nigrescens, Chaetomorpha firma and Glossophora kunthii suggest high irradiances on these recruits might determine the shallower limits of distribution of these speciesEstudios previos han encontrado que el número de especies formando un banco de formas microscópicas en pozas de mareas de Chile central incluyó sólo la mitad del número de especies presentes en la vegetación macroscópica en las cercanías de las pozas intermareales. Una primera condición para sobrevivir en estos bancos radica en la capacidad de las formas microscópicas para tolerar oscuridad total o baja iluminación por períodos prolongados. Para evaluar dicha capacidad, los propágulos de 17 especies de algas verdes, pardas y rojas, presentes y ausentes del banco de formas microscópicas fueron incubadas a distintas combinaciones de intensidad luminosa y fotoperíodo. Propágulos del 47 % de las especies evaluadas (ocho especies) germinaron en oscuridad mientras que los propágulos de las otras nueve especies requirieron valores muy bajos de intensidad luminosa (2-10 µmol m-2 s-1) para germinar. En una mayoría de las especies, las formas microscópicas mostraron una mayor tolerancia a la oscuridad que los propágulos. Algunos sobrevivieron en la oscuridad por sobre un año y una especie (Gelidium lingulatum) pudo sobrevivir en oscuridad absoluta por 500 días. La habilidad para sobrevivir en oscuridad total no se relaciona con presencia de la especie en los bancos de formas microscópicas, con grupos filogenéticos o con historias de vida específicas, con tamaño de propágulo, morfología de la forma microscópica o estatus sucesional (especies fugitivas versus sucesionales tardías). Por lo tanto, tolerancia a la oscuridad aparece como un patrón común a propágulos y formas microscópicas de una mayoría de algas bentónicas. Los patrones de crecimiento exhibidos por las formas microscópicas de Lessonia nigrescens, Chaetomorpha firma y Glossophora kunthii sugiere que el efecto de altas intensidades luminosas sobre estos reclutas podría determinar los límites superiores de distribución vertical de estas especie

Colonisation and growth strategies in two Codium species (Bryopsidales, Chlorophyta) with different thallus forms

In clonal macroalgae, evidence of guerrilla and phalanx growth strategies has been related to a differential response due to a heterogeneous habitat. However, some species of the green algal genus Codium may exhibit different growth strategies at different times of their development. Since the crustose species C. bernabei and the erect C. fragile had different thallus forms as well as ecological and geographic distributions, we used them to test the idea that despite morphological and growth differences, both species exhibited a similar propagation strategy. We cultured, under controlled conditions, individuals of both species to determine, first, if isolated utricles can function as propagation units; second, the type of growth at different stages of development; and, third, if species show differences in specific growth rate. Our results indicated that isolated utricles could be used for propagation because they had the ability to regenerate young mat-forming thalli in both species

Frequency of chimerism in populations of the kelp <i>Lessonia spicata</i> in central Chile

<div><p>Chimerism occurs when two genetically distinct conspecific individuals fuse together generating a single entity. Coalescence and chimerism in red seaweeds has been positively related to an increase in body size, and the consequent reduction in susceptibility to mortality factors, thus increasing survival, reproductive potential and tolerance to stress in contrast to genetically homogeneous organisms. In addition, they showed that a particular pattern of post-fusion growth maintains higher genetic diversity and chimerism in the holdfast but homogenous axes. In Chilean kelps (brown seaweeds), intraorganismal genetic heterogeneity (IGH) and holdfast coalescence has been described in previous research, but the extent of chimerism in wild populations and the patterns of distribution of the genetically heterogeneous thallus zone have scarcely been studied. Since kelps are under continuous harvesting, with enormous social, ecological and economic importance, natural chimerism can be considered a priceless in-situ reservoir of natural genetic resources and variability. In this study, we therefore examined the frequency of IGH and chimerism in three harvested populations of <i>Lessonia spicata</i>. We then evaluated whether chimeric wild-type holdfasts show higher genetic diversity than erect axes (stipe and lamina) and explored the impact of this on the traditional estimation of genetic diversity at the population level. We found a high frequency of IGH (60–100%) and chimerism (33.3–86.7%), varying according to the studied population. We evidenced that chimerism occurs mostly in holdfasts, exhibiting heterogeneous tissues, whereas stipes and lamina were more homogeneous, generating a vertical gradient of allele and genotype abundance as well as divergence, constituting the first time “within- plant” genetic patterns have been reported in kelps. This is very different from the chimeric patterns described in land plants and animals. Finally, we evidenced that IGH affected genetic differentiation among populations, showed lower levels of F_ST index when we compared holdfast than lamina samples. In the light of this, future studies should evaluate the significance of chimeric holdfasts in their ability to increase kelps resilience, improve restoration and ecosystem service.</p></div

Hierarchical AMOVA analyses of spatial scales of differentiation in <i>L</i>. <i>spicata</i>.

<p>All data showed significant differences at <i>P</i> <0.001 after 10000 permutations.</p