Abstract
Average age and maximum life span of breeding adult three-spined sticklebacks (Gasterosteus aculeatus) were determined in eight Fennoscandian localities with the aid of skeletochronology. The average age varied from 1.8 to 3.6 years, and maximum life span from three to six years depending on the locality. On average, fish from marine populations were significantly older than those from freshwater populations, but variation within habitat types was large. We also found significant differences in mean body size among different habitat types and populations, but only the population differences remained significant after accounting for variation due to age effects. These results show that generation length and longevity in three-spined sticklebacks can vary significantly from one locality to another, and that population differences in mean body size cannot be explained as a simple consequence of differences in population age structure. We also describe a nanistic population from northern Finland exhibiting long life span and small body size.
Highlights
Age at first reproduction as well as life span are life history variables that are important for individual fitness through their effects on lifetime reproductive output (e.g. [1]), and for population dynamics and demographic structure – and thereby evolution – of wild populations [2]
Some knowledge of generation length is needed. The importance of this was nicely illustrated by Cuveliers et al [6] showing that the Ne estimates for sole (Solea solea) changed over time as a response to reduced generation length caused by fisheries-induced shifts towards earlier maturation with time
A generalized linear model fitted to the data revealed that there were significant differences in mean age among habitat types (LR ChiSquare = 11.98, df = 2, P = 0.0025), due to the contrast between marine and pond populations (Fig. 2a)
Summary
Age at first reproduction as well as life span are life history variables that are important for individual fitness through their effects on lifetime reproductive output (e.g. [1]), and for population dynamics and demographic structure – and thereby evolution – of wild populations [2]. Age at first reproduction as well as life span are life history variables that are important for individual fitness through their effects on lifetime reproductive output Apart from being parameters of central importance in studies of evolution of individual life histories and population dynamics, life span and its intrinsic, as well as extrinsic, determinants continue to attract interest in the context of research focused on aging and senescence Knowledge of the population age structure is critically important for empirical studies of effective population size (Ne). The population genetic approaches developed to estimate Ne from temporal changes in allele frequencies in neutral loci can be sensitive to biases caused by overlapping generations Since the generation time can be approximated from the average age of breeding adults in the population [7], knowledge about spatial and temporal variation in population age distribution can aid studies of Ne
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