Sammendrag
Aim Previous research on how climatic niches vary across species ranges
has focused on a limited number of species, mostly inv asive, and has not, to
date, been very conclusive. Here we assess the degree of niche conservatism
between distant populations of native alpine plant species that have been
separated for thousands of years.
Location European Alps and Fennoscandia.
Methods Of the studied pool of 888 terrestr ial vascular plant species
occurring in both the Alps and Fennoscandia, we used two complementary
approaches to test and quantify climatic-niche shifts for 31 species having
strictly disjunct populations and 358 species having either a contiguous or
a patchy distribution with distant populations. First, we used species distr i-
bution modelling to test for a region effect on each species’ climatic niche.
Second, we quantified niche overlap and shifts in niche width (i.e. ecological
amplitude) and position (i.e. ecological optimum) within a bi-dimensional
climatic space.
Results Only one species (3%) of the 31 species with str ictly disjunct
populations and 58 species (16%) of the 358 species with distant popula-
tions showed a region effect on their climatic niche. Niche overlap was
higher for species with strictly disjunct populations than for species with
distant populations and highest for arctic–alpine species. Climatic niches
were, on average, wider and located towards warmer and wetter conditions
in the Alps.
Main conclusion Climatic niches seem to be generally conserved
between populations that are separated between the Alps and Fennoscandia
and have probably been so for 10,000–15,000 years. Therefore, the basic
assumption of species distribution models that a species’ climatic niche is
constant in space and time – at least on time scales 10
4
years or less – seems
to be largely valid for arctic–alpine plants.
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