Associations of stream geomorphic conditions and prevalence of alternative reproductive tactics among sockeye salmon populations

Journal of Evolutionary Biology
By: , and 

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Abstract

In many species, males may exhibit alternative life histories to circumvent the costs of intrasexual competition and female courtship. While the evolution and underlying genetic and physiological mechanisms behind alternative reproductive tactics are well studied, there has been less consideration of the ecological factors that regulate their prevalence. Here, we examine six decades of age composition records from thirty‐six populations of sockeye salmon (Oncorhynchus nerka) to quantify associations between spawning habitat characteristics and the prevalence of precocious sneakers known as ‘jacks’. Jack prevalence was independent of neutral genetic structure among stream populations, but varied among habitat types and as a function of continuous geomorphic characteristics. Jacks were more common in streams relative to beaches and rivers, and their prevalence was negatively associated with stream width, depth, elevation, slope and area, but positively related to bank cover. Behavioural observations showed that jacks made greater use of banks, wood and shallows than guard males, indicating that their reproductive success depends on the availability of such refuges. Our results emphasize the role of the physical habitat in shaping reproductive tactic frequencies among populations, likely through local adaptation in response to variable fitness expectations under different geomorphic conditions.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Associations of stream geomorphic conditions and prevalence of alternative reproductive tactics among sockeye salmon populations
Series title Journal of Evolutionary Biology
DOI 10.1111/jeb.13217
Volume 31
Issue 2
Year Published 2018
Language English
Publisher Wiley
Contributing office(s) Coop Res Unit Leetown
Description 15 p.
First page 239
Last page 253