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Quaternary range dynamics of ecologically divergent species (Edraianthus serpyllifolius and E. tenuifolius, Campanulaceae) within the Balkan refugium

Authors

  • Boštjan Surina,

    1. Department of Biogeography and Botanical Garden, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
    2. Natural History Museum Rijeka, Lorenzov prolaz 1, HR-51000 Rijeka, Croatia
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  • Peter Schönswetter,

    1. Department of Biogeography and Botanical Garden, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
    2. Institute of Botany, University of Innsbruck, Sternwartestrasse 15, A-6020 Innsbruck, Austria
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  • Gerald M. Schneeweiss

    Corresponding author
    1. Department of Biogeography and Botanical Garden, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
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Gerald Schneeweiss, Department of Biogeography and Botanical Garden, University of Vienna, Rennweg 14, A-1030 Vienna, Austria.
E-mail: gerald.schneeweiss@univie.ac.at

Abstract

Aim  We investigated Quaternary range dynamics of two closely related but ecologically divergent species (cold-tolerant Edraianthus serpyllifolius and thermophilic Edraianthus tenuifolius) with overlapping distribution ranges endemic to the western Balkan Peninsula, an important yet understudied Pleistocene refugium. Our aims were: to test predictions of the ‘refugia-within-refugia’ model of strong genetic subdivisions due to population isolation in separate refugia; to explore whether two ecologically divergent species reacted differently to Pleistocene climatic fluctuations; and to test predictions of the displacement refugia model of stronger differentiation among populations in the thermophilic E. tenuifolius compared with the cold-tolerant E. serpyllifolius.

Location  The western Balkan Peninsula.

Methods  We gathered amplified fragment-length polymorphism (AFLP) data and plastid DNA sequences from two to five individuals from 10 populations of E. serpyllifolius and 22 populations of E. tenuifolius, spanning their entire respective distribution areas. AFLP data were analysed using a Bayesian clustering approach and a distance-based network approach. Plastid sequences were used to depict relationships among haplotypes in a statistical parsimony network, and to obtain age estimates in a Bayesian framework.

Results  In E. serpyllifolius, both AFLP and plastid sequence data showed clear geographic structure. Western populations showed high AFLP diversity and a high number of rare fragments. In E. tenuifolius, both markers congruently identified a major phylogeographic split along the lower Neretva valley in central Dalmatia. The most distinct and earliest diverging chloroplast DNA (cpDNA) haplotypes were found further south in the south-easternmost populations. North-western populations, identified as a separate cluster by Bayesian clustering, were characterized by low genetic diversity and a low number of rare AFLP markers.

Main conclusions  Clear evidence for multiple Pleistocene refugia is found not only in the high-elevation E. serpyllifolius, but also in the lowland E. tenuifolius, despite the lack of obvious dispersal barriers, in line with the refugia-within-refugia model. Genealogical relationships and genetic diversity patterns support the hypothesis that cold-adapted E. serpyllifolius responded to climatic oscillations mostly by elevational range shifts, whereas thermophilic E. tenuifolius did so mainly by latitudinal range shifts, with different phases (and probably extents) of range expansion. In contrast to the displacement refugia hypothesis, the two elevationally differentiated species do not differ in their genetic diversity.

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