Summary: The Evolution Of Non-Native Species

Well-documented records of introduction for non-native species provide a remarkable opportunity to understand how populations evolve in a new environment. Commonly, species introduced into a new environment came from a few individuals, which is translated mostly in a low genetic diversity due to that they have just part of the genetic diversity of the original population (Frankham 2005; Roman and Darling 2007). Additionally, the process of random genetic drift as it is predicted by the genetic theory is stronger in small populations (Frankham 1996; Roman and Darling 2007). Like further consequence related to genetic drift during the process of introduction, frequently is followed by a strong selection by the new environment what can drive an

Salmo trutta, S. salar, Oncorhynchus tshawytscha, O. kisutch, and O. mykiss; Basulto 2003; León-Muñoz et al. 2007; Soto et al. 2006), therefore Salmonids are useful models to address how species evolve in a new environment. In this context, Rainbow trout Oncorhynchus mykiss Walbaum, 1972 is one of the most introduced and successful freshwater species due to its economic value, its ease of culture, and importance to sport fishing (Casal 2006; Crawford and Muir 2008). In addition this species is listed in the 100 of the world’s worst invasive alien species (Lowe et al. 2000).The native distribution of rainbow trout is the northern hemisphere along the eastern and western Pacific Ocean from California through the Kamchatka Peninsula. This species has several life history forms, including fluvial, ad fluvial, and anadromous (steelhead), and is iteroparous, maturing at several ages including paar (Quinn 2005). This plasticity and economic value have resulted in the worldwide introductions and subsequent colonization of rainbow trout including rivers and lakes in Chilean

Subsequent records were not well documented until the 1980s with the onset of the salmon aquaculture industry (Basulto 2003). Rainbow trout introduced in northern Patagonian had occurred in diverse Araucanian lakes where highlighted two contrasting lakes that can tell us different histories about how rainbow trout populations have evolve after their establishment, Lake Llanquihue and Lake Todos Los Santos (TLS). Differences among them are related mainly to farming pressure and nutrient production (Arismendi et al. 2009; Soto et al. 2006). Lake Llanquihue with an area of 870.5 Km2 is the most important producer of salmonid smolts for aquaculture in the country and the history of introductions occurred between 1910 and 1916 from a temporary rainbow trout hatchery at the outlet of Llanquihue (i.e. Maullin River) (Basulto 2003; León-Muñoz et al. 2007). This temporary hatchery was focused in stoked the lake Llanquihue and tributaries with individuals of rainbow trout brought from Germany (Basulto 2003). After the 1980s the lake Llanquihue became the second producer of rainbow trout smolts with an average of 5.1 million of fish produced between 1998 and 2005 (León-Muñoz et al. 2007). It had been suggested that the current free living population is a combination of earlies stocked and posteriorly individuals escaped