Resistance, emigration, or adaptation? Phylogeography and ecology of European alpine plant species
Conti, Elena , Rutschmann, Frank .
Is the rare Saxifraga florulenta Moretti a Tertiary relictual species? Evidence from molecular dating analyses.
During the Pleistocene glacial maxima, unglaciated areas persisted at the center of the Alps or at the periphery of the Alpine chain, primarily in the southwestern and southeastern Alps, allowing the survival of Tertiary floristic elements. One of these refugial areas, the Maritime Alps in the southwestern part of the Alpine chain, has long been regarded as a region of high species diversity and endemism, with several presumed paleoendemic species. However, a rigorous distinction between paleoendemics of likely Tertiary origin, and neoendemics probably formed after glacial retreat would require an explicit time frame. In our study, we applied molecular dating analyses based on variable-rate methods to estimate the temporal origin of Saxifraga florulenta, a proposed paleoendemic species of the Maritime Alps. The results of both penalized likelihood and Bayesian dating analyses performed on matK sequences support the conclusion that Saxifraga florulenta evolved before the onset of the Pleistocene glacial cycles, most likely between the Tortonian and the Messinian stages. Moreover, the nearly complete lack of intra-specific and intra-individual variation of ITS sequences suggest a high degree of homogenization among ITS repeats in this old, diploid species. The observed lack of molecular and morphological variation, combined with the inferred ancient origin of Saxifraga florulenta, further suggest that this species might represent a "living fossil", as proposed by previous authors. Finally, the strict ecological adaptation of Saxifraga florulenta to siliceous substrates on north-facing slopes at the highest altitudes of the Maritime Alps might present an extinction risk, if current trends of global warming continue.
1 - University of Zürich, Institute of Systematic Botany, Zollikerstrasse 107, Zurich, Zurich, CH-8008, Switzerland
divergence times estimates
European Alpine System
Presentation Type: Symposium
Location: Ballroom 2 (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 1:45 PM