Adil GÜNER, Vehbi ESER - optima

EVOLUTIONARY LINEAGES OF NI-HYPERACCUMULATION AND
SYSTEMATICS IN EUROPAEAN ALYSSEAE (BRASSICACEAE)
Lorenzo CECCHI , Roberto GABRIELLI, Cristina GONNELLI and Federico SELVI
Dipartimento di Biologia Vegetale dell'Università, Via G. La Pira 4, I-50121 Firenze, Italy,
tasmaceto@gmail.com;selviqunifi.it, gabbrielli@unifi.it, cristina.gonnelli@unifi.it
Ni-hyperaccumulation is a rare form of physiological specialization shared by a small number of
angiosperms growing on ultramafic soils. The remarkable proportion of hyperaccumulators in the
family Brassicaceae offer a broad range of opportunities to investigate the expression, regulation
and evolution of the genetic traits underlying such a specialization. However, the evolutionary
patterns of metal accumulation in Brassicaceae are still incompletely known. We used non coding
nrITS sequences and a phylogenetic approach to assess relationships among Nihyperaccumulators
in tribe Alysseae at the genus, species, and below-species level, in order to
test monophyly vs. polyphyly of this trait within such an important group.
Molecular data show that the ability for Ni-hyperaccumulation in Alysseae has a double origin,
appeared in the clades of Bornmuellera-Leptoplax and Alyssum sect. Odontarrhena. Lack of
affinity between Leptoplax emarginata and Peltaria, a member of Thlaspideae into which L.
emarginata is placed by some authors, implies that Ni-accumulation did not originate in
Thlaspideae, unlike commonly believed. In Bornmuellera-Leptoplax this ability represents an
early synapomorphy appeared from an ancestor shared with the calcicolous, sister clade of
Mediterranean Ptilotrichum. In A. sect. Odontarrhena it has multiple origins even within the
three Europaean clades retrieved by DNA sequences. Lack of geographic cohesion suggests that
accumulation ability has been lost or gained over the different serpentine areas of south Europe
through independent events of adaptation and selection associated with changes in the expression
of functional genes. Genetic continuity and phenotypic plasticity within and between populations
of the A. murale s.l. complex call for a reduction of the number of Ni-hyperaccumulator taxa to
be formally recognized.
Keywords: Alysseae, Alyssum sect. Odontarrhena, Bornmuellera, Brassicaceae, Leptoplax,
molecular phylogeny, Ni-hyperaccumulation
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