People: Carla Riva Rossi, Miguel Pascual, Enrique Lessa, John Carlos Garza, Devon Pearse, Néstor Basso.

The recent diversification of anadromous salmonids in Patagonia constitute an ideal setting to study the patterns, processes and the pace of ongoing adaptation, evolutionary change, and ecological speciation in organisms recently introduced to novel environments.

Salmonids provide excellent opportunities for the study of microevolution (evolution at the population or species level) as they exhibit a great diversity in life histories, local adaptations and neutral and adaptive variation, which vary among species and populations, and within conspecific populations. The great range of variation in the expression of key life history traits, such as anadromy (migration between fresh and saltwater), homing (strong site fidelity with the natal stream), and the degree of parity (number of spawning events) that is present in salmonids has shaped their evolutionary process, promoting the development of phenotypic and genetic divergence, population segregation, and the origin of new species in relatively short evolutionary times. Flexibility in these traits has also enabled salmonid fishes to colonize a wide range of novel environments.

The recent diversification of anadromous salmonids in Patagonia (5-25 generations) provides the opportunity to study the process of on-going evolution in species / populations that have recently originated and vary with respect of their tendency to express anadromy and their degree of parity. The main goal of this research is to use introduced salmonids in Patagonia as a model system to investigate the genetic architecture underlying the processes of colonization and microevolution of salmonids in Patagonia. This study may contribute background information for the conservation / restoration of anadromous salmonid in the native range and for addressing the problem of invasive species in recipient communities.

The replicated colonization of Patagonian basins by different species and populations of anadromous salmonids constitutes also an ideal setting to investigate the genetic architecture of salmon evolution across different study systems: (i) ongoing colonization of Atlantic and Pacific Basins of Patagonia by chinook salmon; (ii) evolution and maintenance of anadromous vs. non-anadromous life histories in rainbow trout from the Santa Cruz River (iii) life history variation and population structuring in the complex resident vs. sea-run brown trout from the Grande and Gallegos Rivers, Patagonia, Argentina.

Specific goals

		Investigate the relative effect of neutral (drift, migration and population size) and adaptive (selection) processes during the ecological colonization of novel habitats. Investigate the contribution of genotype vs. environment on the development of the phenotypic and genetic variation associated to the evolution and coexistence of anadromy and non-anadromy and iteroparity vs. semelparity.
Investigate the genetic foundations of reproductive isolation and population divergence at different geographical scales (between and within rivers, geographic localities, and life history forms). Identify genomic regions and pathways associated to the expression of anadromy and other phenotypic traits of potential adaptive value (e.g., growth, fertility, lifespan).

Some specific activities

Establish the source populations of introduced stocks (multiple vs. single origin) and assess the incidence of anadromous behavior in the source populations (anadromous, resident / non-anadromous, mixed) using historical records, population data, and  molecular markers.

Investigate the genetic architecture of contemporary and source populations using molecular markers.

Investigate the effect of environmental variation across Patagonia over the expression of anadromy and asses the suitability of Patagonian basins to promote and sustain anadromous lifestyles. Investigate the genetic population structure among basins and populations and between anadromous and non-anadromous variants within and among populations using mitochondrial and microsatellites nuclear  DNA. Assess the relatedness and association between anadromous and non-anadromous individuals using microsatellites, bioenergetic analysis and otolith microchemical data (Sr:Ca).

Investigate the correlations between early growth and energetic status with the expression of anadromy (e.g., anadromy vs. non-anadromy in rainbow and brown trout) and the age of first ocean migration (stream- vs. ocean-type in chinook salmon) using growth and bioenergetic analysis.

Investigate the adaptive bases of anadromy and non-anadromy and the inheritance of life history traits using quantitative genetics.

Establish the relative adaptive costs and benefits of anadromy vs. non-anadromy and semelparity vs. iteroparity in anadromous salmonids of Patagonia integrating biological and demographic data.