Contemporary divergence in early life history in grayling (Thymallus thymallus)
1 Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, P. O. Box 1066 Blindern, NO-0316 Oslo, Norway
2 Oppland County Governor, P.O. Box 987, NO-2626 Lillehammer, Norway
3 Norwegian Institute for Water Research, Gaustadalléen 21, NO-0349 Oslo, Norway
4 Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, P. O. Box 5003, NO-1432 Ås, Norway
BMC Evolutionary Biology 2011, 11:360 doi:10.1186/1471-2148-11-360Published: 13 December 2011
Following colonization of new habitats and subsequent selection, adaptation to environmental conditions might be expected to be rapid. In a mountain lake in Norway, Lesjaskogsvatnet, more than 20 distinct spawning demes of grayling have been established since the lake was colonized, some 20-25 generations ago. The demes spawn in tributaries consistently exhibiting either colder or warmer temperature conditions during spawning in spring and subsequent early development during early summer. In order to explore the degree of temperature-related divergence in early development, a multi-temperature common-garden experiment was performed on embryos from four different demes experiencing different spring temperatures.
Early developmental characters were measured to test if individuals from the four demes respond differently to the treatment temperatures. There was clear evidence of among-deme differences (genotype - environment interactions) in larval growth and yolk-to-body-size conversion efficiency. Under the cold treatment regime, larval growth rates were highest for individuals belonging to cold streams. Individuals from warm streams had the highest yolk-consumption rate under cold conditions. As a consequence, yolk-to-body-mass conversion efficiency was highest for cold-deme individuals under cold conditions. As we observed response parallelism between individuals from demes belonging to similar thermal groups for these traits, some of the differentiation seems likely to result from local adaptation
The observed differences in length at age during early larval development most likely have a genetic component, even though both directional and random processes are likely to have influenced evolutionary change in the demes under study.