Abstract: Zooplankton diversity in shallow salt lakes of the Andean countries in South America is low and distribution is highly dependent on salinity, which varies from moderate to high. At salinities lower than 90 g/l, the halophilic copepod Boeckella poopoensis (Marsh, 1906) predominates, whereas above that level the anostracan Artemia franciscana (Kellogg, 1912) is the exclusive component of the habitat. This constitutes, however, fragmentary information only. A review of the available literature for Andean saline lakes in Bolivia, Chile, and Peru, confirms that presence and distribution of both species is significantly driven by salinity levels. The results of a species co-occurrence null model analysis, indicates that species associations are not random, and these results are supported by the correlation analysis, which indicates a significant, inverse correlation between species number and salinity, and a significant direct relation of species number with surface of the habitat. The low species diversity characteristically seen in these habitats and their dependence on salinity change.

Abstract: Rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta are the world’s two most widespread exotic fishes, dominate the fish communities of most coldtemperate waters in the southern hemisphere and are implicated in the decline and extirpation of native fish species. Here, we provide the first direct comparison of the impacts of rainbow and brown trout on populations of a native fish by quantifying three components of exotic species impact: range, abundance and effect. We surveyed 54 small streams on the island of Chiloe´ in Chilean Patagonia and found that the rainbow trout has colonized significantly more streams and has a wider geographic range than brown trout. The two species had similar postyearling abundances in allopatry and sympatry, and their abundances depended similarly on reach-level variation in the physical habitat. The species appeared to have dramatically different effects on native drift-feeding Aplochiton spp., which were virtually absent from streams invaded by brown trout but shared a broad sympatric range with rainbow trout. Within this range, the species’ post-yearling abundances varied independently before and after controlling for variation in the physical habitat. In the north of the island, Aplochiton spp. inhabited streams uninvaded by exotic trouts. Our results provide a context for investigating the mechanisms responsible for apparent differences in rainbow and brown trout invasion biology and can help inform conservation strategies for native fishes in Chiloe´ and elsewhere

Abstract: The brine shrimp Artemia is a well known animal extremophile adapted to survive in very harsh hypersaline environments.We compared the small stress proteins artemin and p26, and the chaperone hsc70 in encysted embryos (cysts) of the New World species, A. franciscana and A. persimilis. Cysts of the former, from San Francisco Bay, USA (SFB), were used essentially as a reference for these proteins, while both species were from locations in Chile where they occur in habitats at latitudinal extremes, the Atacama desert and Patagonia. These two species are phylogenetically distant, A. persimilis being closer to the Old World species, whilst A. franciscana is considered younger and undergoing evolutionary expansion. Using western blotting we found all three stress proteins in cysts from these five populations in substantial although variable amounts. The protein profiles revealed by Coomassie staining after electrophoresis (SDS-PAGE) were similar qualitatively, in spite of marked differences in the habitats from which these populations originated, and the long time since they diverged. We interpret these findings as further evidence for the adaptive importance of these three conserved proteins in coping with the variable, but severe stresses these encysted embryos endure.

Abstract: Chromosomal rearrangements have played a key role in the speciation of the New World sexual Artemia species (Crustacea, Anostraca) A. franciscana and A. persimilis. The species differ by a chromosome duplication (2n244 in A. persimilis vs 2n42 in A. franciscana), and a greater amount of heterochromatin (HCH) in A. franciscana. To investigate this difference in HCH, four parameters were compared for the first time in Artemia: 1) the absolute sizes of one A. persimilis and four A. franciscana karyotypes; 2) the relative lengths of all chromosome; 3) the number of heterochromatic bands and 4) the relative amounts of HCH per chromosome and its position. The two A. franciscana karyotypes with the largest HCH amount (26%), have twice (139.26 mm and 134.05 mm) the absolute size of the A. persimilis karyotype (64.91 mm; HCH: 1.97%). Interspecific and intraspecific (A. franciscana) differences in chromosome size and HCH were observed, although the two sets of information are not positively correlated. While A. persimilis shares plesiomorphic karyological traits with Old World species, A. franciscana has apomorphic features such as longer chromosomes and greater HCH content, mainly dispersed towards telomeres. The impacts of such chromosome rearrangements are discussed in relation to the wider geographic distribution, greater colonizing ability, and life history plasticity of A. franciscana. An additional, though preliminary, point of this paper is the observation that the female would be the heterogametic sex.

Abstract: The brine shrimp Artemia (Crustacea, Branchiopoda), a paradigmatic inhabitant of hypersaline lakes, has molecular features to survive under stressful conditions, such as the p26 heat shock protein. We report the RFLP fingerprinting pattern (four restriction enzymes) of a 217 bp fragment of exon2 of the Hsp26 gene in six Artemia franciscana and four Artemia persimilis populations, the most genetically divergent Artemia species co-occurring in latitudinal extremes of Chile. The species-specific RFLP pattern observed is a simple and cost-effective single-locus tool for species delimitation and experimental testing the habitatinduced isolation barrier between them.

Resumen: La celebración este año del bicentenario del natalicio de Darwin y de los 150 años de la publicación de su libro El origen de las especies es el preámbulo conceptual para dos eventos que ocurrirán con ocasión del bicentenario de la independencia nacional: el año de la biodiversidad y el congreso de la Asociación Latinoamericana de Genética, ALAG 2010, Viña del Mar. Los pilares conceptuales del darwinismo, Descendencia con Modificación y Evolución por Selección Natural, representan una idea revolucionaria y sin contrapeso para explicar el origen y diversidad del mundo viviente, que traspasa las fronteras biológicas e incluso tiene aplicación práctica. El lema del congreso ALAG, Biodiversidad latinoamericana: el hombre y sus recursos genéticos, evoca estos conceptos pero a la vez expresa los problemas que preocupan a la genética que Darwin no conoció. Por una parte, explicar las causas de la individualidad y de la diversidad humana y, por otra, los recursos genéticos como base para la estabilidad de los ecosistemas y para el bienestar humano. Celebrar el año de la biodiversidad requiere armonizar la explotación con la conservación de los recursos, dos fuerzas aparentemente antagónicas pero que sin embargo convergen bajo el concepto de sustentabilidad. Para que el desarrollo sea sustentable es necesario caracterizar y monitorear espacio-temporalmente el potencial de cambio evolutivo de poblaciones y especies, propiedad que reside en sus atributos genéticos. Finalmente, el artículo esboza la complejidad inherente a la relación organismo-fenotipo y medio ambiente, de donde surge la necesidad de unificar el conocimiento, un aspecto que deberá ser abordado en el congreso ALAG. Los fundadores y forjadores de la genética y evolución chilena, y otros actores relevantes en un período de gran efervescencia ideológica en torno al valor de la diversidad genética, son recordados hacia el final del texto.

Abstract: We used an invaded stream fish community in southern Chile to experimentally test whether the diversity of exotic species affects their competitive impact on a native species. In artificial enclosures an established invasive, rainbow trout, Oncorhynchus mykiss, and a potential invader, Atlantic salmon, Salmo salar, reduced the growth rate of native peladilla, Aplochiton zebra, by the same amount. In enclosures with both exotic salmonids, the growth rates of all three species were the same as in single exotic treatments. While neither species identity nor diversity appeared to affect competitive interactions in this experiment, the impact of salmonid diversity may vary with the type of interspecific interaction and/or the species identity of the exotics. Our experiment links two prominent concepts in invasion biology by testing whether the result of invasional meltdown, an increase in the diversity of exotic species, affects their impact through interspecific competition, the mechanism invoked by the biotic resistance hypothesis.