Early survival and growth in populations of grayling with recent common ancestors—field experiments

Abstract

Among eight populations of grayling Thymallus thymallus that shared common ancestors 8-28 generations earlier, mean egg mortality ranged between 1·2 and 59·8%; mortality during yolk sac absorption was low (0·0-8·0%) and mean survival to swim-up was high (90-97%), with two exceptions (20% and 50%). Survival probabilities differed significantly among populations, even after statistically adjusting for size at swim-up and water depth, water velocity, gravel size and temperature. Development time from fertilization to first observed swim-up was significantly different among populations, ranging between 27 to 40 days, or 264 to 280 degree-days. Mean specific growth rates during the first external feeding period varied between 1·2 and 2·0% day 1 among populations. Population-specific growth rates were independent of temperature. Rates of divergence were of the same order as in other salmonid studies showing rapid evolution. The phenotypic differences may be due partly to genetic differentiation among the populations. 2000 The Fisheries Society of the British Isles

Similar plastic responses to elevated temperature among different‐sized brook trout populations

“…We found almost no evidence for differences in phenotypic plasticity in relation to population size among Cape Race brook trout populations despite a nearly 50-fold difference in N (179-8416), and a 10-fold difference in N b (18-135). This result is particularly notable given the large number of families and populations used in comparison to analogous vertebrate studies (Haugen andVøllestad 2000, Jensen et al 2008) and that one of our incubation temperatures (98C) represented an extreme condition that would not be experienced by these populations in a natural setting (Power 1980, Appendix A). In regard to the directional hypothesis, there was no evidence that the magnitude of plasticity was related to population size.…”

“…Therefore, although some small populations may have low genetic variation due to drift, fragmentation might also favor high levels of plasticity at key traits to cope with environmental fluctuations (van Kleunan et al 2000, Paschke et al 2003. For example, some very small founder populations have been shown to exhibit rapid plastic responses to novel environments (Haugen 2000).…”

“…Our study represents a model for the investigation of phenotypic plasticity in vertebrate populations of varying size. Data linking plasticity and population size will be important for prioritizing populations for management and conservation, specifically for salmonids, a socioeconomically important group of fish species experiencing population declines in many regions (e.g., Parrish et al 1998) as some small populations might have the ability to respond plastically to environmental change in the short term (e.g., Haugen 2000). Finally, we tested our hypotheses using both the adult census population size (N ) as well as the effective number of breeders (N b ), an analogue of effective population size but for a single breeding event (Waples et al 2013).…”

Lake‐specific variation in growth, migration timing and survival of juvenile sockeye salmon Oncorhynchus nerka: separating environmental from genetic influences

“…This repeated reverse common garden is a potentially more powerful approach to separate environmental from genetic influences on phenotypes than the more convenient alternative, taking fish from a single source population and introducing them (once) into different sites. In this latter case, each population might be evolving differences as well as showing phenotypic plasticity to changing environmental conditions (Haugen, 2000), and the distinction might be difficult to determine.…”

Unintentional selection, unanticipated insights: introductions, stocking and the evolutionary ecology of fishes

“…Following a single human-mediated introduction in one lake in 1880, and subsequent introductions into other lakes (in addition to colonization events unassisted by humans), T. thymallus persisted in the lakes (that did not previously contain them) and now express considerable differences in life-history traits (such as embryonic survival and length at hatching) and, most interestingly, in trait plasticity (Haugen & Vøllestad, 2000). The hypothesis that the discrete T. thymallus populations were adapting to their different local environments was supported by experiments showing that the traits in question and their plasticity resulted in survival that was highest at the temperatures that each population was most likely to experience in the wild (Haugen, 2000).…”