1. 1.
Sampling
from
the
UW
herbarium
•
We
collected
leaves
from
14
species,
focusing
on
tropical
open-­‐habitat
grasses
in
the
PACMAD
clade
(ArisAdoideae,
Arundinoideae,
Chloridoideae).
2.
Extrac:on
and
slide
prepara:on
•
For
each
species,
we
extracted
phytoliths
from
the
dried
leaves
using
the
protocol
from
Piperno
(1988).
•
We
mounted
extracted
phytoliths
on
microscope
slides.
3.
Coun:ng
and
choosing
species
for
GM
•
For
each
species,
we
counted
and
categorized
the
various
shapes
(morphotypes)
(Fig.
3).
•
For
the
GM
analysis,
we
focused
first
on
bilobates,
which
are
disAncAve
in
shape
and
produced
in
many
grasses
across
Poaceae.
•
We
selected
4
species
with
>5%
bilobates.
4.
Photography
and
descrip:on
•
Phytoliths
were
placed
on
slides
in
Permount,
a
fluid
mounAng
medium.
•
We
rotated
them
under
a
light
microscope
and
took
photographs
of
each
angle
(top/base,
side,
end)
for
morphometric
analysis.
•
We
described
phytolith
features
that
are
not
easily
photographed
(e.g.,
ridges
on
the
top
surface).
5.
Geometric
Morphometrics
•
Bilobate
shapes
were
digiAzed
and
analyzed
using
GM
computer
soUware.
Grass
Phytoliths:
A
Key
to
Past
Environments
Elie
Aboulafia1,
William
Brightly2,3,
Camilla
Crifo2,3,
BriXany
McManus1,
Casey
O’Keefe2,
Ashly
Senske2,
Anna
Schorr2,
Caroline
A.E.
Strömberg2,3
1
Department
of
Earth
and
Space
Sciences,
University
of
Washington,
SeaXle,
2
Department
of
Biology,
University
of
Washington,
SeaXle,
3
Burke
Museum
of
Natural
History
and
Culture,
University
of
Washington,
SeaXle
Introduc:on
•
Phytoliths
are
microscopic
silica
bodies
that
form
in/around
plant
cells.
•
Grass
phytoliths
are
both
very
disAncAve
and
variable
(Fig.
1-­‐2).
They
are
the
most
common
grass
fossil,
making
them
ideal
for
tracking
the
evoluAon
of
grasses.
•
However,
to
do
so
it
is
vital
to
study
whether
and
how
phytolith
shape(s)
can
disAnguish
different
grass
taxa.
Research
Ques:on
•
Can
grass
clades
be
disAnguished
by
the
phytolith
shapes
they
produce
and
their
relaAve
abundances
?
•
Specific
Objec:ve:
Use
phytolith
counts
and
geometric
morphometrics
(GM)
of
bilobate
phytoliths
to
disAnguish
different
grass
taxa.
DISCUSSION
●
Our
preliminary
results
suggest
that
phytolith
relaAve
abundance
and
shape
can
be
used
to
disAnguish
grass
taxa.
●
This
combined
approach
is
promising
for
idenAfying
ancient
grasses
based
on
fossil
phytoliths
preserved
in
fossil
soils.
●
Because
the
spaAal
distribuAon
of
grass
species
vary
depending
on
environmental
factors
such
as
temperature
and
humidity,
this
work
can
also
help
provide
past
climaAc
and
environmental
informaAon.
References
Strömberg,
C.A.E.,
2003.
The
origin
and
spread
of
grass-­‐dominated
ecosystems
during
the
TerAary
of
North
America
and
how
it
relates
to
the
evoluAon
of
hypsodonty
in
equids,
IntegraAve
Biology.
Univ.
of
California,
Berkeley,
779
pp.
Piperno,
D.R.,
1988.
Phytolith
Analysis,
an
Archaeological
and
Geological
PerspecAve.
Academic
Press,
San
Diego.
Acknowledgements
Maria
Yousoufian
and
David
Giblin
in
the
University
of
Washington
Herbarium,
the
Burke
Museum
paleo
collecAons
staff,
Nik
Pershing,
Ryan
Thummel,
and
Alice
Novello.
This
work
was
funded
by
NSF
EAR-­‐1253713.
Figure
3.
Morphotype
counts,
*bilobates.
Figure
2.
Diagram
of
different
bilobates
viewed
from
each
angle
(Strömberg,
2003).
Results
• Our
counts
showed
that
bilobates
are
more
common
in
the
Arundinoideae
than
in
the
Chloridoideae.
• GM
of
bilobate
shape
separates
the
species
and
clades
in
morphospace.
Figure
4.
Geometric
morphometric
analysis
of
bilobate
shapes.
Figure
1.
Common
grass
phytolith
morphotypes
photographed
in
this
study.
Common grass morphotypes
*82.4%
*32.8%
*50.3%
!
Bilobate)
Rondel)
Polylobate)
)Saddle)
)
Cross))