Message - 7th IAL Symposium

2A-2-O
Lichen: from genome to ecosystem in a changing world
(2A-2-O4) Submission ID: IAL0052-00001
GEOGRAPHICAL STRUCTURE OF CETRARIA ACULEATA POPULATIONS ALONG
A WIDE LATITUDINAL TRANSECT
Fernandez Mendoza F. 1 , Printzen C. 2
1 Biodiversitat und Klima Forschungszentrum, Frankfurt Am Main, Germany
2 Abteilung Botanik und Molekulare Evolutionsforschung, Senckenberg Forschungsinstitut und Naturmuseum, Frankfurt Am
Main, Germany
Many lichen species that occur at high latitudes are common to both hemispheres, showing a bipolar
disjunct distributional pattern. The fruticose lichen Cetraria aculeata, as many other bipolar species, also
spreads into lower latitudes, into temperate and tropical high mountains and dry temperate lowlands. With this
study we aim to explore the historical and geographical processes that determined its current distribution. The
geographical distribution of species has frequently been interpreted in terms of vicariance and dispersal events.
The relative importance of these two processes in the evolution of a species is very difficult to partial out. In the
case of bipolar lichens, and other widely distributed taxa, their distribution has been interpreted in two opposed
ways: a) they had extremely large ancestral ranges, or b) they are/were able to disperse across long ranges. In
this work the lichen C. aculeata was studied from the perspective of population and evolutionary genetics on a
transect joining south and north polar regions along the Andes and the Rocky mountains. Our results suggest
that this species originated in the Northern Hemisphere and advanced progressively towards the Antarctic using
available patches of suitable habitats on high mountain ranges. The genetic structure of populations suggests
the absence of long range connectivity between extant populations. Population size reconstructions suggest that
the species underwent at least one population expansion in the past followed by a more recent contraction. It
seems likely that mid and long range dispersal lead to a transient increase in population size and a subsequent
increase of geographical range during the Pleistocene, Our data suggest that extant regional populations result
from the concurrence of two separate processes: a) population and range expansion, and a posterior b) population
fragmentation leading to the appearance of vicariant demes. The geographical extent and temporal patterns
of range and population size expansions and contractions during the Pleistocene glaciations should be further
explored.
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