Scott A. Elias, Barnaby Crocker, 2008.
The
Bering
Land
Bridge: a
moisture
barrier
to
the
dispersal
of
steppe-tundra
biota?
Quaternary
Science
Reviews, (2008):1-11
Journal homepage:
www.elsevier.com/locate/quascirev
Authors address:
Geography
Department,
Royal
Holloway,
University
of
London,
Egham,
Surrey
TW20 0EX, UK
ABSTRACT.
The
Bering
Land
Bridge
(BLB)
connected
the
two
principal
arctic
biological
refugia,
Western
and
Eastern
Beringia,
during
intervals
of
lowered
sea
level
in
the
Pleistocene.
Fossil
evidence
from
lowland
BLB
organic
deposits
dating
to
the
Last
Glaciation
indicates
that
this
broad
region
was
dominated
by
shrub
tundra
vegetation,
and
had a
mesic
climate.
The
dominant
ecosystem
in
Western
Beringia
and
the
interior
regions
of
Eastern
Beringia
was
steppe-tundra,
with
herbaceous
plant
communities
and
arid
climate.
Although
Western
and
Eastern
Beringia
shared
many
species
in
common
during
the
Late
Pleistocene,
there
were a
number
of
species
that
were
restricted
to
only
one
side
of
the
BLB.
Among
the
vertebrate
fauna,
the
woolly
rhinoceros
was
found
only
to
the
west
of
the
BLB,
North
American
camels,
bonnet-horned
musk-oxen
and
some
horse
species
were
found
only
to
the
east
of
the
land
bridge.
These
were
all
steppe-tundra
inhabitants,
adapted
to
grazing.
The
same
phenomenon
can
be
seen
in
the
insect
faunas
of
the
Western
and
Eastern
Beringia.
The
steppe-tundra
beetle
fauna
of
Western
Beringia
was
dominated
by
weevils
of
the
genus
Stephanocleonus, a
group
that
was
virtually
absent
from
Eastern
Beringia.
The
dry-adapted
weevils,
Lepidophorus
lineaticollis
and
Vitavitus
thulius
were
important
members
of
steppe-tundra
communities
in
Eastern
Beringia,
but
were
either
absent
or
rare
in
Western
Beringia.
The
leaf
beetles
Chrysolina
arctica,
C.
brunnicornis
bermani,
and
Galeruca
interrupta
circumdata
were
typical
members
of
the
Pleistocene
steppe-tundra
communities
of
Western
Beringia,
but
absent
from
Eastern
Beringia.
On
the
other
hand,
some
steppe
tundra-adapted
leaf
beetles
managed
to
occupy
both
sides
of
the
BLB,
such
as
Phaedon
armoraciae.
Much
of
the
BLB
remains
unstudied,
but
on
biogeographic
grounds,
it
appears
that
there
was
some
kind
of
biological
filter
that
blocked
the
movements
of
some
steppe-tundra
plants
and
animals
across
the
BLB.