DOI: 10.5061/dryad.qp512
title: Data from: The temporal window of ecological adaptation in postglacial lakes: a comparison of head morphology, trophic position and habitat use in Norwegian threespine stickleback populations

description: Background: Studying how trophic traits and niche use are related in
 natural populations is important in order to understand adaptation and
 specialization. Here, we describe trophic trait diversity in twenty-five
 Norwegian freshwater threespine stickleback populations and their putative
 marine ancestor, and relate trait differences to postglacial lake age. By
 studying lakes of different ages, depths and distance to the sea we
 examine key environmental variables that may predict adaptation in trophic
 position and habitat use. We measured trophic traits including geometric
 landmarks that integrated variation in head shape as well as gillraker
 length and number. Trophic position (Tpos) and niche use (α) were
 estimated from stable isotopes (δ13C, δ15N). A comparison of head shape
 was also made with two North American benthic-limnetic species pairs.
 Results: We found that head shape differed between marine and freshwater
 sticklebacks, with marine sticklebacks having more upturned mouths,
 smaller eyes, larger opercula and deeper heads. Size-adjusted gillraker
 lengths were larger in marine than in freshwater stickleback. Norwegian
 sticklebacks were compared on the same head shape axis as the one
 differentiating the benthic-limnetic North American threespine stickleback
 species pairs. Here, Norwegian freshwater sticklebacks with a more
 "limnetic head shape" had more and longer gillrakers than
 sticklebacks with "benthic head shape". The "limnetic
 morph" was positively associated with deeper lakes. Populations
 differed in α (mean ± sd: 0.76 ± 0.29) and Tpos (3.47 ± 0.27), where α
 increased with gillraker length. Larger fish had a higher Tpos than
 smaller fish. Compared to the ecologically divergent stickleback species
 pairs and solitary lake populations in North America, Norwegian freshwater
 sticklebacks had similar range in Tpos and α values, but much less trait
 divergences. Conclusions: Our results showed trait divergences between
 threespine stickleback in marine and freshwater environments. Freshwater
 populations diverged in trophic ecology and trophic traits, but trophic
 ecology was not related to the elapsed time in freshwater. Norwegian
 sticklebacks used the same niches as the ecologically divergent North
 American stickleback species pairs. However, as trophic trait divergences
 were smaller, and not strongly associated with the ecological niche,
 ecological adaptations along the benthic-limnetic axis were less developed
 in Norwegian sticklebacks.
description: Read me file with
 location codes0 Sample codes to locality
 names.xls1
 Dataset-FreshwaterData comparing the
 freshwater stickleback only; with principal component scores (see details
 in the manuscript).2 Dataset-Freshwater and
 marineData comparing the
 marine and freshwater stickleback; with principal component scores (see
 details in the manuscript).3 Dataset- Freshwater,
 marine and North AmericanData comparing the
 marine and freshwater stickleback from Norway and the two North American
 species pairs; with principal component scores (see details in the
 manuscript).