ESEB2019_MattBrachmann_13.08.2019.pdf (1.47 MB)
Ecological opportunity promotes diversifying selection and facilitates rapid phenotypic divergence in Icelandic Arctic charr
Version 2 2019-08-25, 06:43
Version 1 2019-08-16, 18:03
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posted on 2019-08-25, 06:43 authored by Matthew BrachmannMatthew Brachmann, Kevin Parsons, Skúli Skúlason, Moira M. FergusonEcological
opportunity can promote rapid adaptive diversification across multiple
populations if niche availability is high, phenotypic trade-offs facilitate diversifying
selection, and spatial dynamics as well as phenotypic divergence reduce gene
flow. We investigated populations of Icelandic Arctic charr (Salvelinus alpinus) to evaluate whether phenotypic
diversification is the result of common niche availability, diversifying
selection, and/or a reduction in gene flow across populations. Arctic charr invaded freshwater Icelandic lakes
within the last 10,000 years and different populations have either diversified
into coexisting benthic and pelagic morphs or evolved as monomorphic populations.
Using single nucleotide polymorphisms we evaluated genetic population structure
to determine if it was consistent with the repeated evolution of morphs in sympatry.
We inferred resource use with stable isotopic signatures and characterized
morphological variation with geometric morphometrics. Adult charr were sampled
from five Icelandic lakes and a river containing anadromous charr. Sympatric
morphs were genetically more similar to each other than to phenotypically
similar morphs in other lake populations. Populations appear to be evolving in
response to similar ecological gradients and aspects of benthic-pelagic niche
availability based on similar resource use patterns. We detected varied degrees
of morphological divergence between sympatric morphs and phenotype-environment
correlations suggest that habitat specific phenotypic trade-offs are facilitating
diversifying selection within populations. Lastly, habitat divergence leads to
reductions in gene flow between morphs, which may further advance phenotypic
diversification. These lines of evidence suggest that high ecological
opportunity and diversifying selection facilitate rapid morphological divergence
and adaptive diversification.