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.