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evidenced
across
Europe,
possibly
related
to
large-‐scale
trends
in
food
resources
(Renaud
and
Michaux
2007).
Finally,
the
wood
mouse
is
an
opportunistic
species
that
accompanied
human
travels
during
prehistorical
and
historical
times
(Genovesi
et
al.
2009).
It
thus
colonized
many
islands,
where
it
displays
cases
of
pronounced
phenotypic
evolution
(Renaud
2005;
Renaud
and
Michaux
2007).
The
shape
of
the
first
upper
molar
(UM1)
was
quantified
using
an
outline
analysis
method,
allowing
for
the
estimation
of
within-‐
and
between-‐populations
patterns
of
variation.
The
following
questions
were
then
addressed.
(1)
Was
Pmax
conserved
among
populations?
This
was
tested
in
a
series
of
comparisons
between
populations:
within
lineage,
among
lineages,
and
in
an
insular
population
where
adaptation
and
drift
could
have
promoted
local
divergence.
(2)
Did
Pmax
channel
evolution
into
favorite
directions,
validating
its
proposed
role
of
‘line
of
least
resistance
to
evolution’?
This
was
tested
in
several
situations:
(2.1)
among
lineages,
involving
a
probable
role
of
drift
between
isolated
groups;
(2.2)
along
the
latitudinal
trend
on
the
continent;
(2.3)
on
islands,
where
adaptation
and
random
factors
may
both
promote
divergence.
Material
and
Methods
Material
The
study
is
based
on
a
data
set
of
586
wood
mouse
first
upper
molars
(Table
1).
Most
specimens
were
genetically
diagnosed
as
Apodemus
sylvaticus,
discarding
possible
mixing
with
the
related
species
Apodemus
flavicollis.
The
only
exception
were
specimens
from
the
collection
of
the
Museum
National
d’Histoire
Naturelle
(MNHN,
Paris,
France)
and
from
the
collection
of
the
Centre
de
Biologie
et
Gestion
des
Populations
(CBGP,
Montpellier,
France),
but
all
originated
from
areas
in
Western
France
were
A.
flavicollis
is
not
documented
(Quéré
and
Le
Louarn
2011).
Most
of
the
wood
mice
considered
belong
to
the
Western
European
genetic
lineage,
including
populations
from
mainland
and
various
islands
(French
Atlantic
Islands:
Oléron,
Noirmoutier,
Ré;
Mediterranean
Hyères
Islands,
off
South-‐Eastern
France:
Port-‐Cros
and
Porquerolles;
Ibiza
off
Eastern
Spain).
The
italo-‐balkanic
genetic
lineage
was
represented
by
localities
from
mainland
Italy
and
various
islands
(Corsica,
Sardinia,
Elba).
Sicily
and
the
satellite
island
Marettimo
correspond
to
a
separate
lineage
related
to
the
Italian
one
(Michaux
et
al.
1998b).
North-‐African
populations
correspond
to
a
separate
lineage
related
to
the
Western
European
one
(Michaux
et
al.
2003)
but
it
is
documented
here
by
a
single
locality.
