All right, everyone, it gives me great pleasure to hand the
microphone over to Professor Jim Cullen.
I was going to start by saying who I am, but I guess I don't have to.
The Department of Geological Sciences is very pleased to have be able to welcome
Doctor Dana Reuter to our department as a visiting professor.
As a native New Englander, she received her undergraduate degree at
Mount Koyo College, which many of you are probably familiar
with, and then she headed West where she
received her PhD at the University of Oregon.
And then subsequent to her finishing her doctorate,
she got awarded A prestigious NSF postdoctoral fellowship that she
completed at Texas A& M and the Florida Museum of Natural
History.
Dana is a paleoecologist whose research focuses on ecological links among extinct
mammalium taxa and the influence of past climate change has on ecological
relationships.
Her special focus is on diet.
She looks to the fossil record to understand the processes that Dr.
ecological diversity and community changes.
Her talk today is entitled.
Is it up there?
Good.
I don't have to say it.
And please welcome her with a round of applause.
Thank you, Jim.
So we'll see if I want a wander.
I also have a laser pointer, so that'll help today.
So thank you for having me.
I'm very excited to be here, and I'm very excited to talk in honor of
Darwin's birthday.
This is quite exciting for me and we're going to talk a little bit about
something that I think Darwin would be highly interested in,
basically diet and how it interacts with other traits in mammals and how that
influences how they go extinct and the communities that they live in.
So if you don't know me, this is something you should know about
me.
I really love food.
I love thinking about food.
I love cooking food.
I actually gave my family a homemade cookbook this year for Christmas,
and this is a picture of me eating one of my favorite foods,
which is a cardamom bun.
I still have not perfected baking them, but maybe someday.
But I'm also very interested in animals and why they eat certain foods and how
they eat those foods and why we have so many different kinds of animals that
consume such different varieties of things from their environment.
And mammals are a great group to study this in because they have evolved such
different shapes and sizes, and they have a lot of traits that
actually align with their foods that they're eating.
So if you think about the teeth in your head,
I think about them a lot because as a paleontologist,
we use those as clues to see what they have been consuming.
And the Today, what we're going to talk about is how I
think about this as a paleoecologist.
So how I can think about diet in the past, how I can kind of reconstruct it.
And then I'm going to talk about how lovely the Oregon fossil record is and
the projects that I I did there when I was living out in Oregon and I'm still
working on to this day.
So we're going to talk about first the this project I have on herbivore
community structure.
So we're going to really focus in on the herbivores in the community.
And I'm going to show you some isotopic evidence for the foods that they were
eating.
And then I'm going to talk about a project that I'm still picking at,
and it's still ongoing, where I'm reconstructing the entire
community.
I'm making food webs for these ancient communities.
So we need a little primer first before we can really dig into what I do as a
paleoecologist.
We need to think about traits and how they're linked to feeding strategies and
mammals.
And as a paleo ecologist, I do something and you use what is called
diet proxies.
And this is a stand in for actual observations of of the diets of organisms.
So I can't go out in the field and watch my extinct Organism eat something.
So I need to take a measurement or have something stand in for that data.
And the ones that I use the most are tooth shape and size.
So the two examples I have here are of a browser and a grazer.
And so if a browser is picking up nice soft leaves,
its teeth will usually be lower.
It also allows them to maybe crack things open in a little if they're eating nuts
and stuff.
So a lower tooth is better for that job.
But if you're a grazer, you're eating a lot of grit.
So both grass itself has abrasive objects in it and it's also dirty if you're
thinking about it's really close to the ground.
So you need a taller tooth to deal with all that grit that you're eating.
So we can use tooth shape as a stand in for the diets of these organisms.
Snout shape and jaw shape are also useful.
I've done some work looking at the jaw shape of animals and how thick and how
long the jaws are, and that can indicate the diet of the
organisms as well.
Another really good trait that I use a lot as a paleoecologist is actually body
mass, and this is a really nice figure that I
like to show.
So we have body size at the bottom here, and it's actually getting bigger this way,
and it's also getting larger in the other direction as well.
And this is showing how changes occur in diet related to body mass in mammals.
And so if you're an herbivore, you might be eating pollen and nectar
when you're smaller.
But as you get larger and larger, you actually need to start eating plants
that are more abundant on the landscape.
So you might be relying more on leaves and grasses that you can find in many
places.
The same thing kind of happens in carnivores where you're eating small
things like insects, eggs, and then as you get larger and larger,
you need to take down larger prey in order to meet your energetic needs.
You can't run around and catch a ton of spiders or ants.
You need to actually eat larger organisms once you get to a certain size.
And one of the first projects I kind of really got into was trying to figure out
what's going on with the omnivores.
Because if you imagine, if you mix foods, you can kind of break some rules.
And if we're trying to reconstruct what's going on in the past,
we need to know a little bit more about what omnivores are doing as well.
So I spent a lot of time actually working on that project,
collected data from modern animals and actually plotted their body mass versus
the different dietary types that they have.
And one of the first findings that we found was that most omnivores don't eat
all types of food.
There's kind of subsets within omnivore that seem pretty consistent.
It's actually really rare to eat every single type of food.
It's hard to combine them all down here just to kind of clue you in.
A lot of the scale that I'm going to be talking about today is actually in log
scale, because if you look at body mass between
a really small thing and a really big thing on the same scale,
it's really hard to read.
So just to clue you in on the numbers here.
So the first thing I really want to point out is that what we found is that prey
type is more important than plant type for omnivore and how it relates to body
mass.
So here we have Invertebrore omnivores, so they're eating invertebrate prey and
they are on the average smaller than omnivores that are combining foods with
say, vertebrate prey.
We don't see a similar pattern in plants.
So eating fibrous foods versus non fibrous foods doesn't really affect the
body mass as much.
So fibrous foods we typically think of as leaves and grasses versus things like
fruit nectar, pollen on the non fibrous side.
So we found this really interesting and intriguing and it helps us think about
what's going on in the fossil record as well,
because now we can look at the body mass of omnivores and make a little bit of a
prediction about what they were eating in the fossil record.
And so just to kind of put together this whole picture of using proxies and
thinking about the the diet of an Organism,
we're going to use the panda as a lovely example because I love talking about the
panda's diet because it's really interesting and weird.
So it eats bamboo even though it's a bear.
And so in order to understand the panda, we need to think about its evolutionary
history, so where it came from.
So for instance, it's a bear, so it has different tools and its body is
already in a particular shape.
And the lineage it came from wasn't eating bamboo before,
but it had to change and evolve in a way that would allow it to eat bamboo.
Its environment is causing a lot of this influence because it's living in an
environment that has a lot of bamboo around it.
So it's there's natural selection there, pressure to maybe evolve to eat this
particular food item.
But in order for that to happen, we need to think about morphology.
So what changes need to happen and what tools does it have that can indicate that
it's eating that particular diet and then also it's body mass?
Is there energetic constraints from that food that is causing it to have a
particular size?
And so I kind of think about all of these things together when I'm thinking about
diet in the past.
And I'm combining a lot of different data sets.
So I'm combining field data if I'm going out and collecting fossils,
museum data if I'm going to a museum and taking samples,
and also previously published data and databases.
And I'm combining that to form this picture of what the Organism was eating
in the past.
And then I'm using that information to kind of make predictive rules about what
might happen in the future and how ecosystems function over time.
So today we're going to spend a little bit of time mostly in the environmental
part of my research.
Kind of clued you in a little bit to what I've done before with morphology and body
mass, but today we're going to talk a lot more
about the environment.
And I think this would have been a topic that Darwin would have been really close
to Darwin's heart because he really knew that the environment plays a large role
in the selection on organisms, and the environment determines what is
available to an Organism to eat.
So the environment is where we're finding all these foods that the organisms can
eat.
And so for a lot of different studies have been done in the past,
We've been learning more about how ecosystem type can affect diversity,
community composition, food web structure, and also animal abundance,
even how many animals we can have on the landscape.
And so as a paleontologist, I'm kind of looking at the same thing in
the past, but I'm asking slightly different
questions.
I'm asking questions like, did extinct communities behave the same
way as modern ones do today?
Do we see a pattern through time?
How has past climate change influence communities?
So if we do see differences, is this because of climate change?
Is it because there's a different climate system that was going on at that time
versus today?
And does past community change say something about our future again?
Can we make predictions to how we as humans are maybe changing the planet?
What might happen to those ecosystems in the future?
And the really good example I'm going to walk us through is about grasslands.
So if you didn't know, grasses are actually geologically young
and grasslands are geologically young compared to Earth's history.
And we kind of take them for granted because as humans,
we actually evolved in this landscape and we've lived in them and we spend a lot of
time in them.
And as we drive across North America, we see these lovely fields,
but this is actually quite a unique environment that wasn't around all the
time.
So maybe around 28,000,000 years ago, that's when grasslands start appearing.
And then really 3,000, 000 years ago is when we start seeing
really expansive grasslands across North America and in the globe,
and we can think about how unique this environment is compared to, say,
forests that would have been there before.
So this is a really open landscape that requires different traits and new
adaptations and new ways of being than when you're in a forest,
there's fewer places to hide.
You have to maybe change your body mass to avoid predators.
You have to maybe Burrow underground.
I gave the example of your teeth have to change to deal with all the grit that
might be on your food.
And so we can see these changes through time and past research has really shown
how if we take all of the different groups in North America.
So these are this is evidence in North America for both rodents.
So this is smaller organisms and ungulates which are hoofed mammals.
So think horses, cows, etcetera, deer and we can see a change in their
morphology through time as we're progressing to today.
So this is today and grasses would have started appearing around maybe 30 million
years ago, maybe a little earlier, but they really start getting going like
I said kind of towards the end here.
And in rodents what we're looking at is again that tooth height.
So this is smaller teeth, shorter teeth.
Brachyidone teeth are low crowned.
We have mid height teeth, taller teeth and these are those ever
growing teeth.
So if you think about rodents having those ever growing teeth and we can see
that there's an increase in taller teeth through time,
especially in rodents and they react quite quickly to this new environment.
So rodents have a shorter lifespan, they can reproduce faster so they can
adapt and evolve quicker to new changes.
So this is this is expected is that we'd see the signal of grassland environments
in them first compared to hooved mammals.
And same thing here that we're seeing.
We have low crown teeth, brachyidont, mesodont, hipscelodont.
And what we're seeing is we have an increase in tall toothed ungulates and
then we actually have a a decrease in overall diversity.
And this is driven by the brachyidont browsing organisms going extinct.
We are learning, though, that this change in North America of
grasslands expanding is kind of variable and is patchy throughout the rock record.
This is an image of what are known as phytoliths.
So these are inside all plants.
They're little silica bodies that help the plants stay upright.
They help at all along with the lignin and cell walls that a lot of plants have.
And they have unique shapes depending on which plant they're actually coming from.
So we can identify them based on morphology.
And as we study these and also the pollen record,
we're we're learning how the spread of grasslands in North America was also
different at local areas.
It wasn't just all at the same time.
Maybe a mountain was in the way causing a rain shadow,
and that prevented the grasses from quite getting there for a little bit.
And so this is the motivation for looking at this in Oregon,
because Oregon actually has a wonderful rock record.
There's a lot of volcanoes in Oregon, if you didn't know,
and they make a lot of volcanic ash and that kills and also preserves a lot of
fossils.
And so there's almost a continuous rock record in Oregon from around 40 million
years ago to around 7,000,000 years ago.
And there's many fossiliferous deposits throughout that record.
And so here's just a example of some of the fossil localities that I've studied.
And these are murals at the John Day Fossil Beds Park,
the National Monument representing this change that we think occurred also in
Oregon, going from more forested ecosystems to
maybe something that looked sort of like a Saviana,
where you have patchy forested areas and more open areas,
and then finally to this open grassland environment.
Here's some examples of the really lovely fossil bearing rocks that I got to work
in out in Oregon just to show you the scale of the rock record that we're
talking about.
And I also want to point this out because all of these little ledges here are
actually ash deposits and we can date them.
And this is important because it allows us to really precisely know the ages of
some of these fossils, which is why I can tell you the story
that I'm going to tell you today.
So another important reason why I wanted to study this phenomenon in Oregon is
that it's very geologically dynamic.
And there's been a lot of events that have occurred in Oregon throughout this
time that has been recorded.
So we have a lot of volcanoes in Oregon.
There's a lot of mountain building events, there's faulting,
there's the the Columbia Flood basalts that kind of coded the in almost the
entire state.
And so these, these geologic events make it very
different and unique compared to say the Great Plains,
the interior of North America where we have a lot of the evidence of grassland
expansion happening.
So a lot of the studies that have been done before have mostly focused on the
Great Plains.
And instead, we want to see if the same pattern is
occurring here in this geologically complex area.
So basically the question is, is the same thing happening in Oregon
that we are seeing elsewhere?
So the specific questions that I ended up asking are,
how has the Oregon mammalian community changed over the last 32,000,000 years?
Did dietary diversity change in this time?
So the Lego Miocene is this time period that I'm talking about around 32,000,
000 years ago.
And do these changes in functional diversity and trophic structure align
with our current knowledge of what was happening in Oregon?
A lot of the evidence that we have for this change from this forested ecosystem
to a grassland ecosystem is based on very little of our plant fossils that we have.
And also paleosols.
There was some paleosol which are ancient soil data.
So the proxies that I'm going to use instead are tooth morphology that I
talked about.
So we're going to look at tooth height, body size again,
so because that tracks with a lot of different dietary differences.
And then we're also going to use isotopic evidence because you are what you eat.
So if you eat a particular kind of plant that is going to be preserved in your
body.
And so this is another line of evidence that we can use to kind of balance
against those other two measurements.
So again, the tooth height that I mentioned, Oh,
and this is the example of the isotopic measurements.
So if you're a grazer, you're going to have a different value of
both carbon and oxygen in your body then compared if you eat ate plants that are
in a closed environment.
I'm going to break that down for you even more.
So in order for us to talk about isotopes, we actually need to talk about plants.
So you thought maybe it was just about mammals today.
JK.
We got to go back to plants.
So if you haven't thought about them in a while,
there are two pathways for photosynthesis.
There's the C3 pathway.
So we have C3 plants and then we have C4 plants.
And the main difference that's important for isotopic work is that C3 plants do
all of their photosynthesis in the same cell that they actually take CO2 in from
the atmosphere, but C4 plants actually pass that CO2 down
into another cell.
And this allows them to do better in drier environments,
but it also influences their isotopic signature.
And Oregon is actually mostly C3 plants.
There's very little C4 plants in Oregon, and this is because of the amount of rain
and the climate in that area.
So C4 plants do better in drier, sort of like the interior of North
America and Oregon gets too much rain for them basically.
And this is actually.
Great for us and for my project because C3 plants are very sensitive to the
environmental conditions and with which they're growing and they'll actually
record that in their bodies.
And so this is a plot here done from a whole bunch of measurements from around
the globe of C3 plants and their isotopic values specifically related to carbon.
And down here is the precipitation, so the mean precipitation that they're
experiencing.
And so if we have a very closed forested environment that's very humid and damp
and dark, those will have a different value and
will be they'll have a different value than those that live in dry environments.
So as the plants become more and more water stressed,
they'll actually become heavier and heavier in their isotopic values.
It is important to note a few things.
So these differences, we can we can track them in animals too.
So if an animal is eating these plants that are experiencing water stress,
we can actually see that in their their bodies.
And this is a measurement of tooth enamel, which is what I'm going to talk about
because it's preserved in the rock record.
And this is a bison versus some of the other deer that live in Yellowstone,
showing that if you're a grazing bison grazing a lot of grass and driers parts
of the environment, then you'll have a different isotopic
signature than if you're more of a browser eating things in the forests.
One thing to keep in mind though, that'll come up later when I talk about
the actual values, is that a lot of the time we make this
distinction between grass and trees, and this is pretty well documented and
it's kind of true, but more evidence is showing that there
are many different kinds of plants that can have the same isotopic signature.
And it's really going back to that amount of evaporation that's happening.
So if they're all hanging out in a dry environment,
even if there is a tree and a grass, a lot of the times they'll look the same.
And even parts of the plant can be different from one another.
So if you have the top of a plant that's experiencing more evaporation,
then the top of the plant will be not as it'll,
it'll be a little bit more heavy than the other parts.
OK, so data collection, we'll come back to the isotopes and I'll
explain it again and it'll, it'll make sense once we have actual
values from these organisms.
So data collection, I spent a long time in the field and also
visiting a number of museums to find the right specimens to do this project.
And because I was looking at many fossil sites,
we actually needed quite a few specimens, partially because we're going to compare
many different organisms and we wanted a sample size greater than one,
which is actually harder to do in the fossil record than you'd think.
And then we're also comparing different formations.
So we wanted to make sure that we had enough of a sample size in each one.
And I'm highly grateful to a lot of the people that allowed me to go to museums
and look through their collections.
And isotopic work can be kind of challenging because it is destructive.
So you actually need to take a tiny sample of the tooth.
You need to take a drill and drill it off.
And so I spent a long time trying to sift through what was in the collections and
finding the worst teeth but that were still identifiable,
which is also very difficult.
You want the tooth that you know what the animal is,
but no one's going to mind if you just take a little bit of it.
And we do only take a really tiny bit.
And I wish I had a vial to show you how small of the amount of powder.
We're getting better and better at this technique as as time progresses,
we need fewer and fewer bits of enamel.
But still, it can be somewhat difficult to convince
someone to let you drill such a nice, beautiful tooth.
So once we got all these samples, we had to clean them,
we had to drill them.
We took them back to the Oregon Stable Isotope lab.
And as you can see, I spent a lot of my COVID time alone in
the lab, measuring out tiny little bits of enamel
powder, washing them to get out any contaminants,
drying them, and then running them on the mass spec.
So many days were spent looking and lording over my samples.
So the first thing we're going to talk about,
the results that I would like to talk about is actually not the isotopic work.
So we're combining different types of data again, because again,
we can't see these animals eating.
So we have to use many lines of evidence to figure it out.
So the first thing we're going to look at is actually the morphology again.
So we're going to look at tooth height, oops, tooth height.
And for this plot, again, we've got body mass heavier on this side.
This is log scale again and we're actually got three different types of
tooth height.
We've got that low crown, brachydont, mesodont, hipsodont.
And so hipsodont's the taller tooth, Brachyodont's the lower tooth.
And the first thing to notice is that in the Turtle Cove Member,
which is our oldest fossil site, and this is during the Oligocene,
during that time that we think there wasn't any grasses there,
we have no high crown tooth organisms.
So these are all herbivores, ungulates, but none of them have tall teeth.
They're all very short.
And they also don't have really large body sizes.
There's some that do get kind of large, but a lot of the organisms are kind of in
this lower range.
Once we get into the Maskel formation, which is during this time which is called
the Mid Myosin climatic optimum, which is when we have a warming event and
it becomes a little bit more wet.
And this is when we think there was maybe a mixture of a mixture of environments.
And so we maybe have some grasses, some patchiness,
some heterogeneity on the landscape.
We have a lot of different organisms.
We have some that are smaller and have low crown teeth and then we have some mid
crown teeth and then we have those high crown tooth organisms living there too.
And then once we get into the rattlesnake formation,
which is when we think grasslands had really established themselves in Oregon,
we can see a big shift in the community and we have larger organisms.
Again, it's kind of hard to be small in a
grassland environment.
And then we also have a lot more organisms that have taller teeth and we
only have one individual species that has a low crown tooth and this is the peccary.
So this is more of a a pig like animal.
So that's the morphology.
That's what the morphology is telling us.
But let's let's think about the isotopes.
And I'm going to like explain the isotope chart real quick because it can be kind
of confusing.
Basically, we have lower values which are indicating
more closed environment and we're going to plot the tooth values on this plot.
And these lines are indicating the different sort of levels for those global
plant values that I mentioned earlier.
So beyond this line, we're in the water stressed C3 plant
environment.
So if an animal has a tooth value in this area,
we're thinking that it lived and ate food in a water stressed environment.
Beyond the line into the white would actually indicate C4 plants.
So that would indicate that we have C4 plants and it was eating something even
higher in value.
Again, I'm going to remind you that these cut
offs for thinking about the environment, they also can indicate different plant
parts.
So think tops of trees and bushes that are experiencing a lot of evaporation.
OK.
So this is all of our data put together, which is again,
we've got the Turtle Cove member here, Masco formation and the rattlesnake.
So this is that closed environment that we think is happening in the Oligocene.
We've got this warm environment where we think we have a mixture of environments
and then we have the rattlesnake formation,
which we think is more of a grassland environment.
So the first thing to note is that we don't actually have any evidence of
closed canopy feeding.
So the forests that were there, we're not dense enough to have the same
signal that we get from a very densely closed canopy environment.
The other thing to know is that a lot of the organisms in the rattlesnake
formation have similar values.
So the there's kind of a shrinking of the values and expansion of space that they
were occupying at the time.
So maybe the landscape was more homogeneous at that late stage.
So if we're thinking it's a continuous grassland,
this would be consistent with that.
So again, narrow values for the rattlesnake
formation.
I kind of want to get into the specific animals because something that we can do
now that we have this information is we can talk about specific organisms and
what they were eating related to one another.
And I'd like to tell you a little bit about oriadons because I find them
intriguing.
This is an extinct group of ungulates that we don't have any analogues for
today, so they're not around today.
We don't really know how they functioned.
We have fairly good idea from their morphology.
They're kind of like sheep, pig, camel things.
They're very, they're very cute.
And so they start off actually eating plants more in the closed environment.
So this isn't completely closed canopy, but they're kind of more hanging out in
the forests, browsing a lot of the foods in that area.
And then actually as time goes on in the Maskel, we only have one or a dot left,
that one species of oreont and it's kind of expanded the foods that it's eating.
So Ticoleptus has a little bit taller teeth.
It's getting into that mesodont, that mid level high.
So only middle, it's kind of hard to describe.
Not high crowned, it's middle crowned teeth.
So mesodont is what we say it is, and so it we think it expanded its diet.
And this is maybe in response to this changing landscape,
it's trying to kind of adapt to this new food source.
And then actually when we get to the rattlesnake, there's no more oridans.
They've actually gone extinct at this point.
So we don't see them on the landscape and we have no evidence of them around.
So we actually might have this story of them trying to adapt to this new
environment that's coming on the scene.
Another example that was very intriguing and very interesting to my colleagues and
I from this data is there's a small horse called Archaeo Hippus.
And that's what these dots are here.
And it's actually quite small.
It's it's very, very small for the time.
And it's very interesting because its values were quite high,
suggesting it was eating water stressed plants.
So we were trying to think about what this would look like and we actually read
up a lot about the poodoo.
And the poodoo lives a life where it goes out into these open these open areas.
It eats a lot of the the plants in these open patches.
And then when it's threatened by a predator, it runs back into the woods.
So it actually eats eats a lot of the things that we would think would be
consistent with this value of having a more high or enriched value here.
And but it's body size and other parts of it,
it's morphology suggests that it probably was relying on these forested areas for
protection.
OK, let's see how I'm doing on time.
I'm doing all right.
So conclusions from the isotopic study so far that we have and actually this work
is published.
So there's a lot more conclusions that I didn't quite pick apart for you today,
but there's a, there's a bunch in there.
We have a more homogeneous ungulate community both morphologically and
isotopically.
So both lines of evidence kind of support this as these global temperatures change
and grasslands expand.
So this story of going from a more forested ecosystem to a grassland
ecosystem is fairly consistent both isotopically and morphologically.
And the things that are really changing is we have those small browsers with the
low crown teeth being lost from the landscape.
So the poor Oridan's no longer there.
OK, so that was the kind of the first project
and that's great.
But what about the rest of the community?
So we're seeing this change.
So if we think about these communities and these ecosystems,
starting with the change in vegetation, maybe grasses are coming in.
We see this change in the ungulates, the herbivores on the landscape that are
eating those plants.
Maybe we can layer in another layer here and put a lot of the other organisms into
the community.
And that's, that's the next project that my
colleagues and I worked on.
So we actually, the previous isotopic work was just on
the John Day formation, the Maskel formation and the,
the rattlesnake.
But now we're actually going to put in the rest of these fossil localities that
kind of track this global temperature change that we're interested in.
And we're going to look at 2 aspects from these fossil sites.
We're going to look at functional diversity.
And this is sort of the the amount of each Organism and each kind of bin.
If we're going to classify them as extra large herbivores, small carnivores,
small omnivores, etcetera, we can actually look at the the shape and
changes in those bins and see how they've changed through time.
And this has been done for the Great Plains.
So this paper looked at changes in ecosystems in the Great Plains from
around the same time periods that we were interested in,
and we do see changes there.
So do we see the same in Oregon?
And then we're also going to reconstruct food webs because I am very obsessed with
trying to figure out how to do this correctly for the fossil record.
And there are some really great people that have worked on this for marine
ecosystems.
And so trying to translate them to terrestrial ecosystems in the past is
something I'm very passionate about and interested in.
And so something that this can give us that's different than functional
diversity is we can actually think about how energy is flowing through the
community and how the relationships between the organisms are changing.
So the basically the question is here are the players on the landscape changing?
And here the question is, are the, is the game kind of changing?
So if we have this shift in the amount of organisms we have in each bin,
will we also see a shift in the basic structure of the ecosystem or does it not
matter?
That's the question.
So in order to do this reconstruction, we collected data from modern papers on
predator prey interactions that occur in today's ecosystems,
and we kind of made-up a set of rules that will help us outline what we think
the link should be for these past organisms.
Some details, though, that we had to leave out is we had to
leave out things like pack hunting, because that can be really hard to figure
out in the fossil record.
It's very hard to know if a community of ancient carnivores hung out together or
not.
Same thing.
Also, we had to make some rules about omnivores
and carnivores were treated as both prey and predators.
But we did build in a rule that if the prey is bigger than you and is also a
carnivore, you did not eat that thing.
So we had to kind of cut out the impossible links.
And so these are the rules that we ended up falling on.
And so we have our predator size classes bend and then we have our prey size
classes here as well.
And then after we kind of reconstructed these links just to kind of hone in on
like why we made the decisions we did.
These are supposed to be potential interactions.
These aren't necessarily maybe the actual interactions on the landscape.
So we're trying to narrow in on the most likely scenario for that fossil locality,
for that group of organisms.
And so in order to do that, one of the things that we did also to
control for uncertainties in the fossil record.
So if you imagine the fossil record is not always complete,
so we don't always have all the organisms that maybe would have been on the
landscape at that particular time.
We're going to actually lump the nodes into what is called a trophic species.
So if by reconstructing these food webs, they have the same exact interactions
that we're reconstructing in say a giant web for each species.
So this would be maybe the web with each individual species plotted.
And after we simplify it down it, it breaks down those nodes into the
unique nodes in the landscape.
And we, we did this process and we also wrapped
in body mass variability because again, we have these rules,
but that doesn't necessarily mean that, say, if you're a predator,
you're not always going to be 4. 5 kilograms, right?
You're not completely set in that box.
So we had to build in a sort of variability in body mass for that as well.
And so then we we made 1000 simulations for each fossil food,
fossil locality for each food web.
So we made 1000 food webs for each locality.
OK, so the first results, I'll talk about the functional diversity
results.
So this is not the food web results and we've got our,
so this is a contribution plot.
So it's showing how much of each category of Organism is kind of contributing to
that community.
So these are the fossil localities here.
So we have Rattlesnake, Genturra, McKay, these are all sort of the younger.
So Maskel is 15,000,000 years ago, McKay is about 5 million years ago.
Our oldest localities are actually plotting way down here.
So these are from the Oligocene.
Again, that's those communities that we thought
had those really low crowned teeth browsers in our herbivore study.
And then this is actually the modern John Day community.
So these are the modern animals that are living there today.
And one of the things that we found was that the communities differ with respect
to large herbivores and large omnivores.
So the more large omnivores you have in your community are kind of plotting down
here, the two oldest plot here.
And if you have a large herbivores, and especially if you have extra large
herbivores, and what I mean by an extra large
herbivore is a proboscidian specifically.
They're the only ones that really make it into that category.
There's a few others, but this is the main 1.
So if you have proboscidians in your community,
that changes kind of the way that you you look as an ecosystem.
So we learned a lot by doing this and looking at the functional diversity.
But the food webs are telling us a slightly more detailed story,
which is I'm still figuring out.
To be completely honest, this is fresh hot off the press.
I made this last week, so pardon that it's a little messy,
but basically these are all our simulated food webs.
So each one of these little dots here is one of the food webs with that body mass
change.
So again, we're shifting the body masses and
sampling from a distribution of body masses for each species and then
reconstructing a food web for that distribution of body masses.
And this is for each fossil locality.
So we have here we have the turtle, the.
Lower turtle coves.
This is our oldest one.
The interesting thing to me is that on the last plot, the last plot,
the upper and lower Turtle Cove members, these are our Ligacine sites plot
together pretty nicely, right?
They look great, but then once we start putting the links,
we're seeing slight differences.
So this is the lower Turtle Cove here, but the upper Turtle Cove is actually
plotting closer to the modern John Day and the younger Rattlesnake formation.
So the way that the links are actually linking up the organisms for these two
differ, these older sites actually is making a
difference in their community structure.
And one of the reasons why I think this is happening is because of the amount of
or amount of omnivores they're actually having in those communities.
So the Lower Turtle Cove actually has a wide variety of omnivorous canids and
this is influencing the number of links they are having in this food web.
And these are all the metrics we're using to describe the food webs.
So compartmentalisation is basically, do you have a subset within the food web
where all the animals are eating each other and they're one compartment and
there's another compartment over here that are mostly eating each other and
there's very few links between them.
And then a lot of these other ones are describing number of links and degree of
omnivore.
There's also one called Connectants and that's telling us how connected,
how densely connected those the food webs are.
And so again, this one seems to be really driven by
omnivore.
The Maskell here seems to have a lot more compartmentalisation going on.
So we think it's a heterogeneous landscape.
Maybe that's what we're seeing here where we have compartments within our food web
representing those different landscapes preserved together.
So this is still something I'm working out to compare the functional diversity
data with the food web data.
Another insight that we got from reconstructing these food webs,
which I found really interesting was that we can actually see the place to see
megafauna extinction of impacts.
This isn't something I really set out to study on this project.
I was more interested in the spread of grasslands.
But because I also reconstructed the modern John day food web as kind of a
comparison to see if my food web reconstructing process was,
was a a good one.
Whoops.
We we found that a lot of our food webs that had Taiya sewids and proboscidians,
they have really unique places in the food webs.
And once they go extinct, it really shifts around the structure.
And this is again, body mass.
And you can see where proboscidians sit is quite on the larger end of things.
And when they're gone, there's a whole section of the food web
that is not there anymore.
And same thing with Taiya sewids, they're quite a large omnivore and they
exist on the landscape for a long time in a unique position here in the centre of
the food web.
And again, they disappear and you're really just
left with small omnivores on the landscape.
That's where they are in the food webs there.
So if we want to kind of put together everything that isotopic work that I've
done and then also now this new food web material that I'm trying to reconstruct,
we can start to put together a more complicated story than just saying, OK,
grasslands came in and the ecosystem change.
We can start to really get into the weeds here.
So we can start to say things like, OK, so we start off with a well connected
omnivore and browser rich community in this forest.
So we have a lot of different kinds of omnivores and there's a lot of browsers
hanging out.
And then as warm and wet conditions arrive,
because the masculine formation is during this mid Miocene climatic optimum where
we have it being a little warmer, we're starting to get that more
heterogeneic genetic landscape and we end up with a less connected landscape,
food webs, sorry, a less connected food web.
And we have a lot more diversity of herbivores.
So there's a lot of herbivores on the landscape,
but they're not as well connected with, say,
the the predators and omnivores on the landscape.
And we also have the expansion of that large herbivore space in in both
morphology and in the food web.
So again, those proboscidians show up from Asia and
then things start cooling down again.
And this is when we think grasslands really started to pick up in Oregon.
We start seeing them and we have our kind of our last transition where we're we
have fewer browsers, not as many omnivores and the communities
are shifting to having more small and mid sized carnivores.
And so overall, our conclusions are saying that these
landscape changes do 'cause certain mammalian functional groups to be more at
risk of extinction.
Kind of knew this a little bit that browsers disappear from North America as
grasslands expand.
But we're seeing this in Oregon as well.
And we can specifically point to certain species that go extinct at certain times.
And this is also having community structure consequences.
So the food webs are changing through time because of these disappearing
organisms.
Other things that I know that's different than just looking at say we,
we knew that browsers were taking hit at this time,
but we also see the decrease in mid size omnivores.
So there's not as many of those on the landscape as well.
Also fruit and plant dependent omnivores disappear.
This is a lovely reconstruction of an ancient primate that lived in Oregon.
It's no longer with us.
And then also the shift in extra large herbivores I found was really interesting.
The kind of arrival of probositians and then subsequent disappearance also shifts
the communities.
OK, so I'm almost done.
We'll, we'll have questions here in a second,
but I do want to plug in.
I just want to give you a little bit of a taste of something else I'm working on
because I just talked a lot about fossil sites and fossil localities and ancient
communities and such.
And I actually have a hard time talking about this sometimes and having the
appropriate language to talk to other biologists and other geologists about
these concepts.
And one of the things that I got into when I was working on my post doc is
we're actually working on defining terms to make it a little easier for someone to
talk about what's going on with, say, a modern ecosystem and what's going on
with an extinct ecosystem.
And specifically, we want to, we want to define the dietary niche.
So a niche is a concept that is used often in biology.
And we want to define the terms that are related to the dietary niche specifically
so that when I say that I'm talking about something in the past,
I can say something like I'm talking about the potential dietary niche versus
if I'm looking at real dietary data from the landscape,
I can talk about the realised dietary niche.
So this is something that I have been thinking a lot about and it's been kind
of breaking my brain.
But it's been, it's been a lovely conversation with
other palaeontologists, other biologists, and we've put together quite a big group
of people and we're actually writing a theory and review paper at the moment.
So keep an eye out for that too.
With that, I have a lot of people to thank.
I did a lot of field work.
I went to a lot of museums.
I touched a lot of amazing fossils, and a lot of people helped me out with
with all of that, identifying things, having lab access,
just even living outside for weeks on end.
So I have lots of lab groups to think and a lot of students actually too.
A lot of students always go out with us in the field.
So I love their contributions to everything.
And with that, I'll take questions.
So it's actually really interesting.
There's a very good paper talking about how much time you have in a day to eat
and how much you can actually how many insects you can suck up in a given time.
And then calorie count of how many you need to eat in order to meet your like
amount of calories you need to eat for your certain body size.
And there's actually a nice cut off, it's around 21 kilograms that once you
get bigger than 21 kilograms, you run out of time basically to eat
enough insects to feed yourself to live.
So, and it's it's kind, it's not a completely hard cut off.
They're always, there's always things that break the
rules in biology.
I feel like as a biologist, you just start realizing how many wacky
animals out there that you thought that didn't exist.
And they're just like, Nope, I can do that.
So with some, you know, adaptations for let's, you know,
become quicker at sucking up ants, you can get bigger,
but it's around 21 kilograms.
It's harder to sustain anything larger on just insects alone.
Yeah.
I want a question.
And you said that it was hard to not be big in the grasslands.
Is there like a reason why?
Yeah.
So you can be really.
So in grasslands you can be small and hide maybe underground or not be seen by
larger things.
But that like mid size is kind of hard because predators will try to eat you
basically because you don't have cover as much as in a forest or you can't run up a
tree to get away from a predator.
And so if you have a predator on the landscape,
you need to be faster than them.
And that's why, for instance, horses developed like a singular hoof to
run faster and faster or you need to be big enough to defend yourself, right?
You think of like a rhino is just like really big.
And lions don't really mess with rhinos as much because they're dangerous.
Other questions, yes.
So as grasslands expanded and tooth morphology changed,
did you also notice like a difference in the wear pattern on the teeth?
And if so, does that act as a function of the
expansion of the grassland?
So I didn't, I didn't myself look at wear patterns,
but there is a lot of studying of this and people that have looked in this
specifically.
There's two different kinds of wear patterns.
You can look at miso wear, which is kind of the overall wearing down
of your tooth, and you can look at the shape your tooth
takes with that, like overall profile of the tooth.
And in grasslands, you'd tend to get more of like a flat
wearing down of the tooth.
And then there's micro wear.
And micro wear is actually going back to those,
those phytoliths in the plants where if you imagine everything you eat kind of
leaves a little bit of an impression on your teeth.
It's very small and we have to use microscopes to see them.
But if you're eating a lot of grit and sand,
you'll actually get pitting in your teeth.
And we can see that in the fossil record too.
I didn't look at that because it took, I actually did want to look at microware
as well, including with the isotopic data because
these are really good dietary proxies.
If you imagine an isotopic signal is all the food that you've eaten that you've
used to develop your teeth kind of averaged out.
Microware is a little bit more of a finer signal, a shorter amount of time,
kind of like maybe your last meal before you're fossilized.
But it just takes a long time to collect that data.
So there are really good groups that are working on that.
And there is a group at Oregon State that they do microware there.
It's a great question.
Other questions?
Wait, yeah.
Did you set out to specifically study this in grasslands or did you end up on
grasslands because they had the most type of diversification and like changes
occurring in them?
So this kind of goes to like when you go to grad school and you have to design
your project, right.
So when you get into grad school, you maybe have interests.
You're like, I'm interested in these broad themes.
And then you and your advisor work really hard to narrow in on a specific question
that you can kind of spend a lot of time on.
And when I went to grad school, I actually,
I knew a couple of things because I had an internship at the Field Museum.
I liked looking at teeth, thought they were really cool.
I liked thinking about predator prey interactions,
and I liked thinking about the foods that animals ate,
and then from there narrowed in on specific questions related to that.
And my advisor, she was the one that worked on that
rodent plot where we had the rodents changing through time in response to
grassland expansion.
And so she had already thought about this for a long time.
So then I kind of got into it after that.
Yeah, it's a good question though.
Zachary, did you have how long to speak out?
Yeah, I did.
I was going to ask how can he apply?
Is there a way to be applied to like other ecosystems?
Like for example, I was watching a video about Diana Pyrus
and basically suggested that it leave in a more aquatic ecosystem in front of more
aquatic rotation compared to the Hydrosaurus,
which is which it lives alongside, can be applied to like them.
Even though Diapiris doesn't really have much teeth,
it's that had a peak for some rotation.
Yeah, it can be a little tricky if you so I'm,
I'm using enamel to kind of look at the diet of organisms.
It can be tricky to use other parts of the body because they they change a lot
in the fossil record.
So if you're trying to take a sample, say of bone,
bone will re crystallize a lot more and get a lot of other minerals inside of it
versus your teeth are almost already a rock.
So when they fossilize, they don't change as much,
but you can use tooth enamel to look at like aquatic habits in organisms.
And I know that for like the lineage of hippopotamus and like looking at them
being in the water, that's been done before.
But the the methods that I used in these projects can definitely be applied to
other ecosystems.
And I just specifically didn't look at aquatic animals as much,
although we do have a student that's looking at ancient Beavers in Oregon
because we found a really, really large 1.
And so it's very exciting to think about how we can maybe sample those teeth as
well, to think about if it was also living an
aquatic lifestyle.
Yeah, yes.
Would you expect to find similar changes occurring in Africa at the same time as
it went from forest to more grasslands?
Yeah, I think so.
And a lot of the papers that I actually relied on there,
they look at differences also in modern ecosystems in Africa,
because one of the things about Africa is it still has a lot of the megafauna and a
lot of the ecosystems that we think we're here.
And we're here in North America, we just don't have as analogues anymore,
right?
So, yeah, there are differences between the
ecosystems in Africa even today that we can see between grasslands and forested
ecosystems.
Yeah.
Any other questions?