Hypothesis testing framework
Pacific lamprey genetic traits and their associated phenotypes appear to be inherited independently and may occur in combinations that manifest as different life history strategies to fit unique ecological niches throughout the species’ range. For example, in the Willamette River basin there is relatively high diversity of traits and nearly equal portions of genetic variants associated with alternate forms of small and large-bodied adults and ocean- versus river-maturing ecotypes. The following multiple strategies appear to be represented: 1) stream-maturing small- and large-bodied fish that have overwintered below the Falls, 2) ocean-maturing small- and large-bodied fish that arrive shortly before spawning above the Falls, and 3) stream-maturing small- and large-bodied fish that arrive after June and ascend the Falls. The fact that there are four separate chromosomes with important adaptive genes (some with undetermined trait associations) provides for the possibility that various combinations of adaptive variants at these four chromosomes could underpin a multitude of life history strategies. Patterns in the occurrence of the two phenotypic traits we emphasized in this study suggest that Pacific lamprey life history traits may exhibit differential fitness across the range. For example, extrapolation predicts a predominance of large-bodied, stream-maturing forms in northern B.C. and the interior Columbia River, small-bodied ocean- and stream-maturing forms in Puget Sound, intermediate-bodied ocean- and stream-maturing forms in the lower Columbia, and large-bodied ocean- and stream-maturing forms in the southern coastal range. This provides a hypothesis testing framework to examine the incidence likelihoods of life history traits across the range, and understand factors driving optimization of these traits.