Page 2 - Asylv_molars_Pmax_revised_2014_01
P. 2
2
Abtract
Evolutionary
studies
of
morphological
characters
often
depict
patterns
of
differentiation
and
interpret
them
as
response
to
selection
or
random
divergence
related
to
the
degree
of
isolation
between
populations.
The
pattern
of
differentiation,
however,
may
also
reflect
intrinsic
constraints
related
to
genetic
and
developmental
networks.
How
these
constraints
contribute
to
orientate
evolutionary
trajectories
is
nowadays
a
key
topic
bringing
together
evolution
and
development
in
an
evo-‐devo
perspective.
Morphological
variation
in
a
population,
being
the
product
of
genetic
and
developmental
processes,
can
constitute
a
precious
insight
into
such
constraints.
Widespread
phenotypes
being
easy
targets
of
both
selective
screening
and
random
sampling,
the
direction
of
main
variance
could
act
as
a
‘line
of
least
resistance
to
evolution’.
Extensive
biogeographic
variation
has
been
described
in
the
European
wood
mouse
(Apodemus
sylvaticus)
in
morphological
characters
such
as
the
molar
tooth.
A
latitudinal
gradient
has
been
evidenced
on
the
continent,
interpreted
as
an
adaptive
response
to
biogeographic
clines
in
food
resources.
Extensive
divergence
is
further
documented
on
various
islands,
that
could
be
attributed
both
to
adaptation
to
peculiar
insular
conditions,
and/or
to
drift
related
to
isolation.
Using
geometric
morphometrics,
and
based
on
this
well
documented
biogeographic
background,
we
explore
here
in
what
respect
these
different
patterns
of
differentiation
can
be
related
to
the
directions
of
main
intra-‐
population
morphological
variation.
Most
striking
cases
of
insular
divergence,
as
well
as
the
latitudinal
cline,
occurred
parallel
to
the
main
direction
of
morphological
variation.
This
validates
its
proposed
role
as
line
of
least
resistance
to
evolution
favoring
rapid
morphological
evolution,
either
as
response
to
selection
or
as
a
result
of
drift
or
both.
Whatever
the
process
involved,
this
line
of
least
resistance
is
likely
to
promote
parallel
evolution
in
various
contexts.
