title: Costs of reproduction can explain the correlated evolution of semelparity and egg size: theory and a test with salmon.
abstract: Species' life history traits, including maturation age, number of reproductive bouts, offspring size and number, reflect adaptations to diverse biotic and abiotic selection pressures. A striking example of divergent life histories is the evolution of either iteroparity (breeding multiple times) or semelparity (breed once and die). We analysed published data on salmonid fishes and found that semelparous species produce larger eggs, that egg size and number increase with salmonid body size among populations and species and that migratory behaviour and parity interact. We developed three hypotheses that might explain the patterns in our data and evaluated them in a stage-structured modelling framework accounting for different growth and survival scenarios. Our models predict the observation of small eggs in iteroparous species when egg size is costly to maternal survival or egg number is constrained. By exploring trait co-variation in salmonids, we generate new hypotheses for the evolution of trade-offs among life history traits.
authors.affiliation: Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada.
authors.forename: Holly K
authors.initials: HK
authors.lastname: Kindsvater
authors.affiliation: School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada.|InStream Fisheries Research Inc., Vancouver, British Columbia, V5M 4V8, Canada.
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Braun
authors.affiliation: Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
authors.forename: Sarah P
authors.initials: SP
authors.lastname: Otto
authors.affiliation: Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada.
authors.forename: John D
authors.initials: JD
authors.lastname: Reynolds
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D052284:Clutch Size; D005260:Female; D008954:Models, Biological; D010063:Ovum / Q000502:physiology*; D012098:Reproduction / Q000502:physiology*; D012474:Salmon / Q000502:physiology*
keywords: Costs of reproduction; demography; iteroparity; life history theory; offspring size; salmon; semelparity