Abstract
Variation in age and size of mature nine-spined sticklebacks (Pungitius pungitius) within and among 16 Fennoscandian populations were assessed using skeletochronology. The average age of individuals in a given population varied from 1.7 to 4.7 years. Fish from pond populations were on average older than those from lake and marine populations, and females tended to be older than males. Reproduction in marine and lake populations commenced typically at an age of two years, whereas that in ponds at an age of three years. The maximum life span of the fish varied from 3 to 7 years. Mean body size within and among populations increased with increasing age, but the habitat and population differences in body size persisted even after accounting for variation in population age (and sex) structure. Hence, the population differences in mean body size are not explainable by age differences alone. As such, much of the pronounced intraspecific variation in population age structure can be attributed to delayed maturation and extended longevity of the pond fish. The results are contrasted and discussed in the context of similar data from the three-spined stickleback (Gasterosteus aculeatus) occupying the same geographic area.
Highlights
Maturation at small size is usually accompanied by short life span, whereas late maturation at larger size is typically associated with long life span [1], [2]
The mean age of the fish differed significantly among habitat types (GLMM, Habitat: F2,13.16 = 14.56, P,0.005): fish from the marine and lake populations were younger than the fish from the pond populations (Tukey HSD, P,0.05), but there was no significant difference between lake and marine fish (Tukey HSD, P.0.05; Fig. 2)
We will discuss these observations and relate them to what is known about life history variation in nine- and three-spined sticklebacks, as well as address some implications of these findings on future studies
Summary
Maturation at small size is usually accompanied by short life span, whereas late maturation at larger size is typically associated with long life span [1], [2] This general life history pattern is thought to be driven mainly by variation in extrinsic mortality rates [2]. Populations subject to low extrinsic mortality rates may be selected for delaying their maturation at larger size, and exhibit prolonged lifespans [2,3,4,5,6] While these general life history patterns have been demonstrated in numerous studies, there is a great deal of variation around them The patterns of longevity associated with size and age at maturation are highly variable among organisms [15]
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