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.
Se presentan los resultados de dos cruceros de pesca de investigación de la jibia, Dosidicus gigas (Orbigny 1835) realizados entre julio de 1993 y enero de 1994 en la Zona Económica Exclusiva de Chile comprendida entre los 29º S y 40º S. En cada lance se registró el día, hora, duración del lance, así como el volumen de la captura por lance y máquina potera, para efectuar estimaciones de abundancia relativa. A los ejemplares capturados se les determinó la longitud dorsal del manto (LDM), peso total, peso eviscerado, peso manto, sexo y se les extrajo el tracto digestivo, para un análisis del contenido estomacal. Las jibias sólo fueron capturadas entre los 29º S y los 30º S. En el primer crucero (invierno) se registraron ejemplares grandes (71 a 98 cm LDM) y chicos (< 44 cm LDM) de ambos sexos, mientras que en el segundo crucero (primavera) se capturaron sólo jibias de tamaño intermedio (26 a 60 cm LDM). Las distribuciones de frecuencias de tamaños determinadas en los cruceros muestran dos cohortes de D. gigas en la zona de pesca. La dieta no varió entre las estaciones y estuvo compuesta principalmente por peces pelágicos y demersales, secundariamente cefalópodos y ocasionalmente crustáceos pelágicos, incluyendo también canibalismo. Las relaciones longitud-peso fueron similares en ambos sexos y se corrobora que las jibias registradas en aguas de Chile, alcanzan pesos mayores a la misma longitud que las poblaciones de jibia de México y Perú.
Erroneous identifi cation of the mussel, Mytilus galloprovincialis
RESUMENEsta comunicación informa que la presencia de Mytilus chilensis (Hupe 1854) citada en la literatura científi ca para la costa de la Bahía de Concepción (Chile) no es correcta, siendo Mytilus galloprovincialis (Lamarck 1819) la identifi cación taxonómica válida.
Populations of the flounder, Platichthysjesus, were screened for electrophoretically detectable protein variation at up to 37 loci. Atlantic and North Sea populations (subspeciesjesus) were genetically very similar to one another (120.99) but different from Adriatic (subspecies italicus) and Black Sea (subspecies luscur) populations. The values for genetic identity between subspecies were around 0.9. Diagnostic loci enabled specimens ofyesus, italicus and luscus to be differentiated from one another. Samples ofyesus showed two to three times the heterozygosity levels of italicus or luscus, consistent with the greater population size ofyesus. Morphological comparisons enabled populations to be categorized to subspecies, Plalichthys~Yesus italicus and luscus are valid subspecies: the terms are not synonyms. The genetic distance data provide an estimate ofdivergence time of the three subspecies at about 2 My ago, an estimate that seems reasonable in the light of present knowledge concerning the recent geological histories of the Mediterranean and Black Sea basins.
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