Reproductive timing phenotypes in female salmon: true alternatives or extreme variants?

Publication year: 2011
Source: Animal Behaviour, Available online 13 October 2011</br>
Margaret A.*Warren, Yolanda E.*Morbey</br>
Kokanee salmon,Oncorhynchus nerka, can vary in their maturation status at arrival to spawning areas and in their subsequent behaviour. In Meadow Creek, British Columbia, typical ‘red-arriving’ females arrive with red nuptial coloration, spawn within a few days, and then defend their nests against digup by conspecifics. In contrast, atypical ‘silver-arriving’ females arrive with scales still present and delay maturation and spawning by 3–4*weeks. Our objective was to further describe the silver- and red-arriving phenotypes and to test the hypothesis that they are proxies for a dimorphism of life cycle variation. Colour was a good indicator of a female’s stage of maturity and senescence because silver-arriving females had larger guts, larger and fattier livers, and smaller eggs containing less lean mass than red-arriving females. Colour, and therefore maturity status, covaried with life history traits: silver-arriving females were younger (in 2008 and 2009) and smaller (in 2008) than red-arriving females. The percentage of silver-arriving females was higher in 2009 (11.4%) than in 2008 (2.2%), possibly because of poor conditions for growth in 2009. We also observed some silver-arriving males, but they were much rarer (0.4% in 2008 and 1.5% in 2009). Scores on the first discriminant function based on colour information from digital photographs distinguished silver-arriving and red-arriving females. At the population level, these scores were bimodally distributed, but the dip between modes did not clearly separate silver- and red-arriving females. Although silver- and red-arriving phenotypes represent female reproductive tactics for delivering parental care, they are not distinct alternatives and instead represent the extremes of life cycle variation in this population.</br>
Highlights

? Female kokanee vary in colour and sexual maturity at arrival to spawning areas. ? Red arrivals spawn within a few days whereas silver arrivals spawn within 3–4*weeks. ? These phenotypes represent different reproductive tactics relating to parental care. ? Colour data show these phenotypes do not reflect alternative reproductive tactics. ? Instead, female reproductive tactics show continuous variation at the population level.</br></br>

13th October 2011 22:33

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