Knowledge about the genetic underpinnings of invasions—a theme addressed by invasion genetics as a discipline—is still scarce amid well documented ecological impacts of non-native species on ecosystems of Patagonia in South America. One of the most invasive species in Patagonia’s freshwater systems and elsewhere is rainbow trout (Oncorhynchus mykiss). This species was introduced to Chile during the early twentieth century for stocking and promoting recreational fishing; during the late twentieth century was reintroduced for farming purposes and is now naturalized. We used population- and individual-based inference from single nucleotide polymorphisms (SNPs) to illuminate three objectives related to the establishment and naturalization of Rainbow Trout in Lake Llanquihue. This lake has been intensively used for trout farming during the last three decades. Our results emanate from samples collected from five inlet streams over two seasons, winter and spring. First, we found that significant intra- population (temporal) genetic variance was greater than inter-population (spatial) genetic variance, downplaying the importance of spatial divergence during the process of naturalization. Allele frequency differences between cohorts, consistent with variation in fish length between spring and winter collections, might explain temporal genetic differences. Second, individual-based Bayesian clustering suggested that genetic structure within Lake Llanquihue was largely driven by putative farm propagules found at one single stream during spring, but not in winter. This suggests that farm broodstock might migrate upstream to breed during spring at that particular stream. It is unclear whether interbreeding has occurred between “pure” naturalized and farm trout in this and other streams. Third, estimates of the annual number of breeders (N b) were below 73 in half of the collections, suggestive of genetically small and recently founded populations that might experience substantial genetic drift. Our results reinforce the notion that naturalized trout originated recently from a small yet genetically diverse source and that farm propagules might have played a significant role in the invasion of Rainbow Trout within a single lake with intensive trout farming. Our results also argue for proficient mitigation measures that include management of escapes and strategies to minimize unintentional releases from farm facilities.

Genetics data have provided unprecedented insights into evolutionary aspects of colonization by non‐native populations. Yet, our understanding of how artificial (human‐mediated) and natural dispersal pathways of non‐native individuals influence genetic metrics, evolution of genetic structure, and admixture remains elusive. We capitalize on the widespread colonization of Chinook salmon Oncorhynchus tshawytscha in South America, mediated by both dispersal pathways, to address these issues using data from a panel of polymorphic SNPs. First, genetic diversity and the number of effective breeders (N b) were higher among artificial than natural populations. Contemporary gene flow was common between adjacent artificial and natural and adjacent natural populations, but uncommon between geographically distant populations. Second, genetic structure revealed four distinct clusters throughout the Chinook salmon distributional range with varying levels of genetic connectivity. Isolation by distance resulted from weak differentiation between adjacent artificial and natural and between natural populations, with strong differentiation between distant Pacific Ocean and Atlantic Ocean populations, which experienced strong genetic drift. Third, genetic mixture analyses revealed the presence of at least six donor geographic regions from North America, some of which likely hybridized as a result of multiple introductions. Relative propagule pressure or the proportion of Chinook salmon propagules introduced from various geographic regions according to government records significantly influenced genetic mixtures for two of three artificial populations. Our findings support a model of colonization in which high‐diversity artificial populations established first; some of these populations exhibited significant admixture resulting from propagule pressure. Low‐diversity natural populations were likely subsequently founded from a reduced number of individuals.

Different pathways of propagation and dispersal of non‐native species into new environments may have contrasting demographic and genetic impacts on established populations. Repeated introductions of rainbow trout (Oncorhynchus mykiss) to Chile in South America, initially through stocking and later through aquaculture escapes, provide a unique setting to contrast these two pathways. Using a panel of single nucleotide polymorphisms, we found contrasting genetic metrics and patterns among naturalized trout in Lake Llanquihue, Chile's largest producer of salmonid smolts for nearly 50 years, and Lake Todos Los Santos (TLS), a reference lake where aquaculture has been prohibited by law. Trout from Lake Llanquihue showed higher genetic diversity, weaker genetic structure, and larger estimates for the effective number of breeders (N b) than trout from Lake TLS. Trout from Lake TLS were divergent from Lake Llanquihue and showed marked genetic structure and a significant isolation‐by‐distance pattern consistent with secondary contact between documented and undocumented stocking events in opposite shores of the lake. Multiple factors, including differences in propagule pressure, origin of donor populations, lake geomorphology, habitat quality or quantity, and life history, may help explain contrasting genetic metrics and patterns for trout between lakes. We contend that high propagule pressure from aquaculture may not only increase genetic diversity and N b via demographic effects and admixture, but also may impact the evolution of genetic structure and increase gene flow, consistent with findings from artificially propagated salmonid populations in their native and naturalized ranges.

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The Humboldt Sulfuretum (HS), in the productive Humboldt Eastern Boundary Current Upwelling Ecosystem, extends under the hypoxic waters of the Peru-Chile Undercurrent (ca. 6˚S and ca. 36˚S). Studies show that primeval sulfuretums held diverse prokaryotic life, and, while rare today, still sustain species-rich giant sulfur-oxidizing bacterial communities. We here present the genomic features of a new bacteria of the HS, "Candidatus Venteria ishoeyi" ("Ca. V. ishoeyi") in the family Thiotrichaceae.Three identical filaments were micro-manipulated from reduced sediments collected off central Chile; their DNA was extracted, amplified, and sequenced by a Roche 454 GS FLX platform. Using three sequenced libraries and through de novo genome assembly, a draft genome of 5.7 Mbp, 495 scaffolds, and a N50 of 70 kbp, was obtained. The 16S rRNA gene phylogenetic analysis showed that "Ca. V. ishoeyi" is related to non-vacuolate forms presently known as Beggiatoa or Beggiatoa-like forms. The complete set of genes involved in respiratory nitrate-reduction to dinitrogen was identified in "Ca. V. ishoeyi"; including genes likely leading to ammonification. As expected, the sulfur-oxidation pathway reported for other sulfur-oxidizing bacteria were deduced and also, key inorganic and organic carbon acquisition related genes were identified. Unexpectedly, the genome of "Ca. V. ishoeyi" contained numerous CRISPR repeats and an IF CRISPR-Cas type system gene coding array. Findings further show that, as a member of an eons-old marine ecosystem, "Ca. V. ishoeyi" contains the needed metabolic plasticity for life in an increasingly oxygenated and variable ocean.

RESUMENDurante el primer estudio nacional de la zona de mínimo oxígeno (ZMO) y del macrobentos animal costa afuera del norte de Chile (1962), se descubrió una comunidad bentónica compuesta de bacterias fi lamentosas multicelulares gigantes en los sedimentos fuertemente reducidos entre 50 y182 m. La masiva abundancia de fi lamentos bacterianos visibles a simple vista y el extremadamente escaso macrobentos animal, fueron rasgos inesperados. Más recientemente (2004) un nuevo ensamble de bacterias fi lamentosas multicelulares más pequeñas fue descubierto distribuido en los sedimentos más reducidos sub-superfi ciales del tapiz bacteriano. Hoy reconocemos que este ecosistema dominado por procariotas constituye un rasgo mayor y distinto al nivel mundial el que aquí denominamos "Sulfureto de Humboldt" (SH) por su distribución entre Perú central y Chile central. Durante un largo periodo de una intensa investigación que surge después de 1977, con fuerte contribución internacional, se ha acumulado un gran cuerpo de información sobre el primer ensamble y su ambiente, fundamental para la comprensión del funcionamiento del Gran Ecosistema Marino de Humboldt, en tanto que la investigación sobre el segundo ensamble recién comienza. El presente trabajo es un esfuerzo para reunir la mayor parte de la literatura pertinente con la intención de estimular a los científi cos locales a enfrentar el necesario y urgente gran esfuerzo de investigación en las diversas líneas que la biota y el ambiente del Sulfureto de Humboldt ofrecen. PALABRAS CLAVES:Sulfureto, tapetes microbianos, micropaleontología, astrobiología, metabolitos secundarios. ABSTRACTDuring the fi rst national study of the oxygen minimum zone (OMZ) and the animal macrobenthos off northern Chile (1962), a benthic community mainly composed of giant fi lamentous multicellular bacteria was discovered in the highly reduced shelf bottoms between 50-182 m depth. Totally unexpected were the great abundance of massive and visible fi lamentous bacteria and the pronounced scarcity of macrobenthic animals. More recently (2004) a new assemblage of smaller fi lamentous multicellular bacteria was again discovered interspersed within the more reduced subsurface sediment of the same bacterial mat. Today we recognize that this prokaryote-dominated ecosystem constitutes a major distinct benthic marine feature and thus it is here named "Humboldt Sulfuretum" (HS) for his distribution under the OMZ between central Peru and central Chile. During a period of intense scientifi c research which took off after 1977, strongly based on international collaboration, a large body of information fundamental to the understanding of the Humboldt Current Large Marine Ecosystem has accumulated on the fi rst assemblage and its environment while the research on the second assemblage is just beginning. The present work is an effort to put together most of the pertinent literature with the intention of stimulating local researchers to face the much urgent, major scientifi c effort along the many lines offered by ...

Abstract.-The red macroalga Mastocarpus sp. (Rhodophyta, Gigartinales) has been reported as a non-indigenous species in central Chile. In this area the geographic range described for the species encompasses approximately 200 km, from Cobquecura (36°08'S, 72°48'W) up to Punta Lavapié (37°08'S, 73°35'W). Observations carried out at 22 localities along the central-southern Chilean coast allow us to extend the known range of this species approximately 300 km to the north and 600 km to the south. Additional analysis indicated high percentage cover on areas described as the introduction point of the species.

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