GALAXIAS MACULATUS’ DIADROMOUS AND RESIDENT POPULATIONS: EVOLUTIONARY AND ECOLOGICAL GENOMICS OF A PLASTIC LIFE HISTORY TRAIT

Delgado, M.L.¹, Manosalva, A.², Habit, E.², Urbina, M.³, Górski, K.⁴, Link, O.⁵, Ruzzante, D.E.¹

¹Department of Biology, Dalhousie University, Canada

²Centro de Ciencias Ambientales, EULA, Universidad de Concepción, Chile

³Departamento de Zoología, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Chile

⁴Departamento de Ecología, Facultad de Ciencias, Universidad Católica de la Santísima Concepción, Chile

⁵Departamento de Ingeniería Civil, Facultad de Ingeniería, Universidad de Concepción, Chile

m.lisette.delgado@dal.ca

Diadromy, the ability to migrate between fresh- and seawater, is a life history trait suitable for the study of local adaptation and adaptation to salinity changes. Here, we focus on Galaxias maculatus, one the most widespread fishes in the Southern Hemisphere. We first compare 10 diadromous and resident population pairs across the species distribution in Chile using genome-wide SNP markers. Diadromous populations exhibit high gene flow, while most resident populations were strongly genetically distinguishable forming their own genetic group. We then examine how diadromous and resident populations respond to salinity changes. We reared from two pairs of diadromous and resident populations under a common garden setting. Diadromous adults were highly plastic consistently enduring abrupt changes in salinity. Resident adults instead varied in their response as a function of river of origin. Resident G. maculatus from the first river showed no plastic response and an inability to survive abrupt increases in salinity, while resident individuals from the second river exhibited a plastic response similar to diadromous individuals. These findings suggest that resident populations differ in their ability to survive in estuarine and marine environments pointing to differences in local adaptation and suggesting independence in origin.

Palabras clave: GALAXIAS MACULATUS, DIADROMOUS, RESIDENTS, GENOMIC DIFFERENTIATION, SALINITY TOLERANCE