Tip:
Highlight text to annotate it
X
Christy Coghlan: Good afternoon from the U.S. Fish and Wildlife Service's National Conservation
Training Center in Shepherdstown, West Virginia. My name is Christy Coghlan, and I'd like to
welcome you to today's broadcast of the NCCWSC Climate Change Science and Management Webinar
Series. This series is held in partnership with the U.S. Geological Survey's National
Climate Change and Wildlife Science Center. Today's webinar will focus on "Can camouflage
keep up with climate change? White hares on brown snowless backgrounds as a model to study
adaptation to climate stress". Our speaker today is Dr. L. Scott Mills.
Everybody, please join me in welcoming Shawn Carter, Senior Scientist at the USGS National
Climate Change and Wildlife Science Center in Reston, Virginia.
Shawn, would you please introduce our speaker? Shawn Carter: Sure, happy to Christy, thank
you. Thank you everyone for joining us today. Today, Scott Mills is going to be joining
us and giving a presentation. He recently is, I think he's still in the process, actually,
of transitioning to a new faculty position in Fisheries Wildlife and Conservation Biology
at NC State. Prior to that, Scott was a professor or Wildlife Biology at the University of Montana,
where his interests were in the area of Applied Population Ecology.
At this new job, he's going to be addressing questions on global environmental change,
working with the NC State faculty and also our USGS Southeast Climate Science Center
and the North Carolina Museum of Sciences. He's also going to continue studying hares
and color coat change and also expanding work to consider snowshoe hares across North America
and look at other color coat changing species around the world.
He's also hoping to embark on new projects relevant to global environmental change in
the Southeast. But, he's not quite sure what the focal species might be, ranging from salamanders,
alligators, flying squirrels, or maybe something completely different.
A broad portfolio, some interesting work. Today, we're going to hear about his work
where he was at Montana. With that, I'll turn it over to today's presenter, Scott Mills.
Scott Mills: Great, thank you Shawn. Thanks to everybody out there. I will say I'm a newbie.
This is my first time doing a webinar. I'm used to faces out there so that I can glare
at them if anybody falls asleep but I have been told I have a little attention meter
here. It's an exclamation point. I'm told that I can keep track of whether anybody is
dozing off out there in the ether. Anyway, it's great to be here. The movers are carrying
my stuff out of my lab and office and house as we speak so it's good to get a little break
from the moving to give this presentation. I would like to begin by stepping back a bit
and just talking a little bit about the genesis that brought me to this place. I have [pause].
There we go. I've been studying snowshoe hares pretty much continuously since 1998. The studies
all along have been focused on addressing population dynamics of the snowshoe hare and
particularly addressing the role that predation has on individual and population level dynamics.
This particular slide shows the radio collar and the remains of a snowshoe hare. It doesn't
take long to realize that when you are in this business of studying hare population
dynamics, you're really in the business of studying how many different ways hares can
die, and also, getting an appreciation for the role that predation has in shaping population
dynamics and individual behavior. I won't go into a lot of detail. Just to point
to a couple of the big, broad brush places where we and others have thought about the
role of predation in shaping hare population dynamics and behavior.
Of course, we're all familiar with the classic 10 year cycles of hares and lynx. But some
work that we did about 10 years or so ago, we explored the role that heterogeneity across
the forested landscape creates differences in predation rates in closed and open forests
and in so doing, actually is strong enough to dampen the population dynamics.
In this case, there's a population level effect where predation across a heterogeneous landscape
is sufficient to take away the cycles that are so classic in the north.
Just jumping to an example of an individual way that individual behavior is shaped by
predation, we looked at hares at times of full moons which are shown by the white dots
here and at times of non-full moons when there was snow on the ground and when there was
no snow on the ground. The big thing that jumps out here is that
when there's snow on the ground and the moon is full, so the hares are illuminated on the
bright, white background, they seem to behave as if they're perceiving predation risk. They
move a lot less. They hunker down a lot more at those times.
Alas, it doesn't do them any good. They still die more, even when doing that. Here, you
can see that when there's snow on the ground and the moon is full is the time when hares
die the most. All of these things have been bouncing around
in my mind as I thought about population and individual level manifestations, or implications,
of predation. With that in mind, I became struck, over time, thinking about this, which
is that at the heart of a snowshoe hare's life history strategies, its camouflage is
really its best defense from predation. They are remarkably well camouflaged, and
they are a species that actually changes its camouflage in order to track changing weather
conditions. Hares, in the fall, they change from brown, they start gaining white. By late
fall, early winter, they're completely white. Then, when the days begin to get longer again,
in the spring, they have another color moult back to being brown again.
Thinking about predation as a shaping force for hares, and thinking about how the hare's
coat color is critical to its camouflage, and thinking about how the coat color changes
seasonally, all began to really strike me as I started seeing this more and more out
in the forest, as we were doing our field work.
This is what I call a light bulb, hopping around in a brown forest. It's one of our
radio collar hares. I should say that all the pictures in the
slide show today are from our research photos. None of them are re touched, or none of them
involve moving hares around. There was somebody that asked me, one time, "I don't believe
that is actually a hare in its natural habitat. I think you got that hare and took it somewhere
and placed it there." None of these hares have been moved, or touched,
or anything. Anyway, seeing these white hares more and
more over time was striking. It was especially striking as I reflected on the fact that the
single biggest signal of climate change in temperate regions around the world is a reduction
in number of days with snow on the ground. Here, we're looking at this for the Northwest.
The red means that the snow water equivalent has increased over the half century. The blue
means it's decreased. Obviously, very few blue dots out there and lots of red dots,
some of which are quite large, showing a reduction in snow water equivalent.
Here we're looking at it in a slightly different way, for a slightly different geographic region.
This pattern is shown, really, around the world, Europe, Asia, northeastern North America,
that the snowpack is staying for a shorter period of time in temperate regions. This
is largely driven by increased rain on snow events in the fall, and especially in the
spring. Seeing these light bulbs hopping around the
forest increasingly, these hares and realizing that the snowpack was getting shorter, it
obviously got me wondering what would be the implication of that. The implications of a
light bulb hopping around in the forest. What comes to mind is probably this. This
is actually a picture that was sent to me by a colleague in Colorado, Jake Ivans, who
is studying hares down there. This is sort of the intuition that comes to mind when you
see that white hare. You figure, "This must be what's happening to hares." Of course,
there are other options. Really, the question has become, over the
last few years with our research group, to what extent are hares becoming increasingly
mismatched, and what are the implications of that mismatch in terms of changing vital
rates, birth and death rates, survival rates, in particular, and then what might the implications
of that be for the future, for hares. We actually know quite a lot about how wild
animals will respond to global stressors: climate change, or, really, any other human
caused stressor. That can be captured in this graphic for climate change. In the case of
climate change, the stressor that's an anthropogenically driven stressor, is changes in the physical
environment. That affects plants and the physical environment. That in turn leads to animals
having, really, three options. It all boils down to these three options.
These are: animals successfully move to stay within a physical environment envelope that's
appropriate to them, or, they locally adapt without moving. These can be happening together.
If they're not able to do these two things, then the species will be expected to decline.
Of course, how these things play out is going to ultimately change the ecosystem structure.
I'm sure in this audience I don't need to focus very much on moving as a strategy. There's
ample evidence for animals changing geographic range and changing movement patterns. This
has been widely described across a wide range of species. I believe that we spend a lot
less time considering the scope and potential of the second option, that is the possibility
to successfully adapt, in place, to climate change stressors without necessarily moving
and without necessarily declining or dying. One of the ways that plants and animals have
been shown to adapt in place to climate change is through changes in the timing of their
life history events, phenologic changes. Often times, phenologic changes that are described,
such as hibernation emergence or changes in migration, are pretty complicated, multi trophic
level phenologic changes. An animal's migration time becomes disconnected from the optimal
phenologic time of their food source and that creates mismatch.
The challenge with those kinds of examples is that number one, they go across multiple
trophic levels. Number two, it's hard to attribute them necessarily to climate change, because
other things are going on, in many cases land use changes, that can change migration times
or food emergence. Here, in this case, with this case we're talking
about today, it's a very straight forward example, in a sense that either it's a climate
change driven effect that manifests itself either as a presence or absence of snow. We
feel like it's a very nice model system to ask this question of: what is the potential
for animals that have a very strong, fitness related, trait that's affected by this climate
related driver, what's the potential for these animals to locally adapt to a decrease in
snowpack? As I talk more through the talk, what I mean
by, when I talk about "adapt", I'm using it in a bit of a broad sense to say, either dealing
with it locally through plasticity and the coat color change, changing the timing or
the rate of the coat color change, or plasticity in behavior, or actually evolving changes
that lead to adaptation through natural selection. I'll touch on each of these.
Of course, snowshoe hares are not the only players. This is not necessarily a snowshoe
hare story strictly. Many of us are familiar that Arctic fox undergoes seasonal coat color
changes. Several species of weasels undergo seasonal coat color changes. Lemmings go from
brown to white. One or two species of hamsters go from brown to white.
We can map them out and see that a large part of the world is covered by these seasonal
coat coloring species. The genus that has the most coverage of seasonal coat color change
is Lepus. Snowshoe hare here. This is mountain hare, Lepus timidus in Europe and Asia, and
the arctic hare, and also, white tailed jack rabbit.
Lots of species undergo seasonal coat coloring change. What do we know about the drivers
of it? The best we know, from studies of other circannual processes, in some studies of coat
color change is that it's triggered by day length. This is important because it means
that it's not like a chameleon, animals aren't changing from brown to white whether or not
there's snow on the ground. They're changing based on a shortening of day length or lengthening
day length. Essentially, it's a process of hormones being
triggered by photo periods. Here's a schematic developed for weasels. We see that as brown
animals in the summer confront decreased day length, shorter days, then that initiates
the hormonal cascade that ultimately leads to the production of white fur. In the spring,
as the days get longer, again, a hormonal cascade that leads to, again, production of
a brown coat. We have this species confronting reduced snowpacks
with a presumed mechanism of triggering of the coat color change daily.
The way we've attacked this question over the last few years is to radio a bunch of
snowshoe hares, intensively follow them every week, go out, as best we can and get pictures
of every single hare so we can quantify the phenology, get pictures and observations of
the ground around the hare so we could quantify the presence throughout the snow and quantify
a contrast or mismatch. We've done this at two different study areas,
one near Seeley Lake, Montana, western Montana, and one near Yellowstone, just outside of
Yellowstone Park, at quite a bit higher elevation. I should note now that much of what I'll be
talking about today has been done with my master's student, Marketa Zimova. We also
had an amazing bunch of undergraduates. If anybody's interested in the more gossipy side
of this research project, you can go to our blog, our "snowshoe hare chronicle blog",
which the students run. It's entertaining. Also, there's publications and stuff on there
too. The first publication on this work came out
a couple of months ago. What I'll talk about in the next few slides came from this paper.
This picture tells a lot of the story. Let me walk you through this. What this basically
describes is the phenology of the coat color change here and the snowpack here. I'll start
with here. This just shows that we go across the year, from fall to late fall. The right
side panels are the spring, and the late spring. Looking first at the middle panels, you can
see, we've got three different years going on here,. Each year is a different color.
For example, here in 2009, big drop of snow. The snow melted. The snow came again. Melted,
and then eventually, by late November, early December, it was constant.
Different years, different amounts of snowpack, and that was shown across years, or even more
so in the spring. We can see that the spring of 2011 was a very big snowpack. Snow stayed
around a lot longer. The bottom panels are temperature measures,
which show also that the temperatures differed across with year. We kept track of temperature
because we were trying to explore that as a covariant for the coat color phenology.
Here's the bunny story. Here's the hare story. Up here for the three different years, the
vertical lines show the initiation dates or the completion dates of the color molt. The
brown hares began to change to white, they initiated the molt right around the second
week of October. You can see the confidence intervals overlap, which tells us that there's
no plasticity in the initiation of the coat color change. Across all three years, the
initiation was on about the same date. Also, in the fall, the rate of coat color
change across the different years didn't change. We can see that by, again, overlapping confidence
intervals. That tells us that the rate of change from brown to white was constant across
all three years. In the spring, we again see overlapping confidence
intervals for the initiation date. It's early April. But there is some plasticity in the
rate of change. There's no plasticity in initiation but some plasticity in the rate of change.
You can see, especially here, that in that 2011 big snow year, the hares were able to
put on the brakes somewhat and slow down the rate of change once it's initiated.
To get more support for that, just coming at it from another angle, the ideal way to
look at plasticity would be to look at the same animals that survive multiple years and
see how much they change from year to year according to environmental conditions in this
case, according to snowpack. The problem is that hares are lunchmeat for everything in
the forest, so they don't usually survive more than a year. It's hard for us to get
animals that survive in the same location for multiple seasons.
Here, we're looking in the fall at nine hares that survived at least one fall in this case,
survived two falls, shown by the solid and dotted line. You can see that the fall phenology
shows very little plasticity, just like we talked about. All of them are shown over here
piled on top of each other, In the spring, we actually only had one hare
that survived two years, but that one hare again does support what we found with the
analysis I just talked about. That one hare did show plasticity in the two years that
we were able to monitor, 2011 and 2010, so there is plasticity in the rate of the spring
molt. The other question that we addressed in the
PNAS paper was...We've shown that there's not plasticity, but now what we should do
is to turn to some climate downscaling, look at snow models developed specifically for
our study site, downscale to the level of our study site, and ask how much would we
expect the snowpack to change in the future, and then how much would that lead to increased
mismatch without adaptive changes. What we ended up using was local weather stations,
a whole bunch of them interpolated across the northwest for the present conditions,
and then we turned to multiple global circulation models with two different CO2 forcings to
look into the future. What we found is the pattern that's been talked
a lot about in the climate literature, which is that compared to the recent past, we expect
in the future, depending on which CO2 forcing we use, we expect to see a reduction in number
of days of snow on the ground, and even more so as we go further into the future to late
century. [pauses] Sorry. I just was distracted because
my phone beeped, but I think it's all OK. Also, the moving van arrived outside. Ah,
what a day. We see this reduction in number of days with
snow on the ground. What we next did was, we said, "Let's take the snow duration, the
number of days we expect to see snow on the ground, and superimpose that on the average
phenology measured from our hares in the field." The black line here is the average phenology
across years and across hares. Hares are going from brown to white and then back to brown.
The vertical lines are the snow on and snow off dates from the recent past and then from
the future with the two different CO2 forcings. The gray area is what we call mismatch. For
this exercise, we call it a hare mismatch if it was at least 60 percent white hare on
a brown, snowless background. Given that definition...You can adjust that. We've done that, and the
story still stays the same. The gray shows the mismatch, the duration
of mismatched hares. You can see that going into the future, that increases such that
as we see a decrease in number of days of snow on the ground going into the future,
we would expect to see a three to eight fold increase of mismatched white hares on brown,
snowless backgrounds. That is striking, but it still doesn't tell
the whole story because we still have to answer the critical question. What happens to these
mismatched hares in terms of, do they die more, and how might they be able to adapt,
either through plasticity or through adaptive changes through natural selection, which could
happen in a myriad number of ways. The question of increased mortality during
times of mismatch, or increased mortality for mismatched hares, goes way back to that
study I talked about in the beginning when I was talking about the source sink dynamics
that we described. One thing we found there that was quite interesting and actually served
as a genesis, really, as a catalyst for all this work that's happened since, was we were
a bit surprised. We were looking at hares in closed and open
forest patches because we were interested in source sink dynamics. We found that in
the winter and summer, hares had higher survival. The higher survival during the summer, when
there would be presumably less predators, and during the winter, when it's bitter cold.
Survival was actually higher than it is in the fall and the spring. Survival is lowest
up on these open stands in the fall and spring. This is an interesting coincidence, but it's
certainly not compelling with respect to coat color change, because lots of other things
are happening in the fall and the spring besides coat color change. Animals are switching their
diet. Deciduous leaves are coming on. Predator communities are shifting. So this itself was
tantalizing, but it wasn't compelling. But we have over the last few years been working
on the really compelling analysis. I cannot yet tell you details, but the details will
be coming out soon. It's quite a complex analysis. We've used our radio collared hares. It's
a complex analysis because of the changing phenology of the hares and accounting for
the changing seasons and other forms of mortality, missing observations.
But there are some complications. Marketa, my student, will talk some about the results
more in detail at the Conservation Biology meeting later this month. We're working on
a paper. I will say that we do find a signal indicating non trivial costs to being mismatched.
We do find a cost to hares in terms of survival of being mismatched.
If we have mismatched hares, and they are more vulnerable to being killed when they
are mismatched, then the next critical question...I think this has not been well considered for
many cases in terms of climate change. The really critical question is, what do we expect
to happen? As I said, a lot of times, we tend to think,
"Oh my gosh. Let's figure out how to move them or let them move." Or we say, "They can't
move. That means they're doomed." But there is, of course, this third option, this potential
ability for hares to adapt. They can adapt through either plasticity or through natural
selection. We have begun to consider plasticity. I've
already told you that they have very little plasticity in terms of the coat color change
itself. The initiation date in the fall and the spring are fixed, there's a little bit
of plasticity to slow down or speed up the rate of change in the spring, but if there's
no snow before they initiate, they're going to be mismatched.
Can they adapt through behavioral plasticity? Well, so far, we don't see a signal of this.
We've looked at the obvious things that hares might do to be able to adapt to mismatch.
We find that they do not conceal themselves in vegetation more when they're mismatched.
Of course, this assumes that a hare looks down at itself like an emperor with no clothes
and then decides that it better do something about it and gets behind some bushes or behind
a tree. We don't find a signal of that. We don't find that hares flee at further distances
with increasing mismatch. Instead, their flight distance seems a lot more tightly linked to
their concealment, not to mismatch per se. We find that hares don't look around, at least
not at the local site level, and plop themselves down in a place that matches their coat color
the best. As Marketa has said, they didn't get the memo for the dress code, and so did
they look around for the site that best fits the dress code. Instead, if there's areas
with snowy and non snowy places, they tend to prefer the bare ground places.
This is not to say that there is no potential for plasticity of hare behavioral plasticity.
There's lots of other ways to look at it and consider it. Just we haven't found it so far.
So, limited plasticity in the coat color change, limited plasticity in the behaviors. What
about the ability to adapt through natural selection? This is the next big direction
where we'll be taking this project, so I don't have a lot to tell you on this yet, but I
will say...Actually, I guess I'll back up here and stay for a second.
At first, I think, this can strike people as crazy to even be thinking about natural
selection, but it's only crazy if you think about natural selection as being all about
fossils and speciation and thousands of years. Then it seems impossible to imagine that it's
relevant. But, actually, I would say that some of the
most exciting developments in biology with respect to climate change in the last two
decades has been the understanding that evolution actually can happen quite fast on ecological
time, and it can lead to quite strong morphological, behavioral, biochemical changes.
Natural selection can be a relevant factor on ecological scales, especially if the Biology
101 attributes of natural selection are fulfilled. That is, if we have a trait that's variable,
if it's under strong directional selection, that is, it affects fitness so it's under
strong directional selection and it's heritable. We are interested in asking the extent to
which this could be true for snowshoe hares. What I'll tell you a little bit of what we
thought about, and what we've done so far and then where we're going next.
Variable traits. This is a classic variable trait. This is a kind of trait that if you
were natural selection, you would love to act on. This is a variable trait both within
populations and among populations. Let's talk about each of those.
Within populations, different hares definitely change their coat color and there is plasticity
in the rate of coat colors within populations. This is one of our study sites, one year,
one day, and you could see that the full range of possibilities are available. Here's a white
hare on white ground. Here's a brown hare on brown ground. Remember, this is the same
site, same day, and in fact, there because you can see the snow patches and the hares
are different colors. Then you could have white hares on brown ground, brown hares on
white ground. There's definitely variability to act, for selection to act on.
This is looking at the same thing. For one population, one year. Each green dot is an
observation of a hare on a given day. Again, this is going across the calendar and from
hares that are all brown to all white. Yeah. We're looking, here, in the spring, they're
all white. Then they start to change to brown. See, there's lots of variation so that, for
example, on April 25th, you have hares that are everything from nearly completely white,
they've begun to change, but they're still at 95 percent white, all the way down to close
to about 5 percent white. You see the full range. This is what natural
selection could operate on. Also, we know there's variability in the traits
by looking at the species across this range. From most of the snowshoe hare range, they
change from brown to white seasonally. But along the coastal region, for example, Olympic
Peninsula, southwest British Columbia, there are hares that do not undergo the white molt
in the wintertime. They stay brown all winter. There are, even, some very interesting populations
that we're very excited about studying in the Cascade Mountains of Washington and Oregon,
where in the same populations there are white hares and brown hares in the winter in the
same population. Similar sorts of cross population variability
plays out for the Lepus timidus, the mountain hare, which is in Europe and Asia. In particular,
so far, we know of at least one population in Ireland of Lepus timidus that stays brown
during the winter, doesn't undergo coat color molt.
This is definitely a variable trait. That's what natural selection likes to have in order
to operate on, be able to change phenotypes quickly. It's a variable trait within populations
and among populations. Does the trait affect fitness? We're pretty
confident, and becoming more confident almost on a daily basis, at this point, that it does
indeed affect fitness. We see limited plasticity either through the coat color change timing
or through behaviors. As I say, our analysis, it's still preliminarily at this point, pointing
towards a fitness cost of mismatch. The next question is, is it heritable? What
would be the mechanism by which natural selection could operate? What would be the genetic basis
by which natural selection could operate to change this trait, and how fast could it change
with potentially the timing or rate of the coat color change?
To go down this path, we will be linking our field data. We'll keep doing our field data,
and we'll link that with the marvelous world of genomics, transcriptomics and genomic approaches
that will, hopefully, ultimately take us down the path towards understanding candidate genes
for the coat color change. This is something we've just begun working
with colleagues here at University of Montana, Jeff Good, and our colleagues Paulo Alves
and Zef Ferreira at the University of Porto. We've just begin this, but I'll show you some
more, really, hot off the press results. This is just from the last month or so. I guess,
this header didn't show up very well, but it says, "The initial transcriptome sequence
analysis." This is our very, way initial beginning of our genomic analysis. What we focused on,
the sort of low hanging fruits of this, is the focus on that polymorphic population that
I mentioned in the Cascade Mountains. We've sampled it several times. We haven't
yet collected field data there. We've sampled quite a few individuals from there so this
analysis is based on 10 snowshoe hares, all of which were collected in January. Six were
brown, four were white. In the world of genomics, it's just amazing
that 46,000 genetic markers that we've been able to analyze so far in this very preliminary
run. In general, the differentiation between the six brown and the four white individuals,
FST as a measure of genetic differentiation, in this case, between these two color groups
is quite small. It's quite small FST and that's not surprising.
You wouldn't expect to see a huge differentiation between brown and white hares found in exactly
the same spot. But interestingly, we do so far have almost 2,000 outliers as genetic
markers. These could include markers that with more work may become candidate genes
that help us understand the genetic basis of the seasonal coat color change.
No silver bullet yet. I can't announce to you that we've found the white gene, or the
brown gene, or the coat color gene or anything like that. This will be, most likely, a long
process. It will include some captive breeding. In fact my new job, amazingly, at North Carolina,
they're building me what they laughingly call the "Hare Chiller" on the campus at North
Carolina State. So I'm out there, I'll actually have a subzero temperature controlled chamber.
As far as I know, there's nothing like that in use anywhere for looking at seasonal coat
color change. We'll be able to look at that mechanism to coat color change and things
like that to the genomics. The engineers love the challenge of coming
up with a subzero temperature chamber in Raleigh, North Carolina summertime.
This shows us the big picture. The grand vision or hope that I have for this project. Really,
in order to answer this question, can any trait, but in this case we think camouflage
is a nice trait, can camouflage keep up with climate change? To do that, we have been and
will continue to quantify the extent of mismatch, the adaptive cost of being mismatched. Continue
to work on the snow downscaling, that I talked about that we did in the PNAS paper, so that
we can get realistic models for snowpack that are relevant to the animals themselves, and
understand the drivers of the coat color change and of the mortality.
If we can do that, then we, actually, can understand the rate at which the animals might
be able to adapt by either plasticity or through evolutionary changes. Then from that, we hope
to again link that to what we've been doing since 1998 in terms of studying population
dynamics. We can understand the consequences of mismatch on survival rates then we can
put that into population projection models that we've been working on all these years
to understand hare population dynamics. And get to the sort of end point, the very exciting,
I think, important endpoint of to what extent will climate change be likely to actually
change the population dynamics of this particular species that is important by its own right,
and also very important as a strong ecosystem interactor?
That is where we're heading, and it's complex and exciting. More complex than this. This
was an interview, an article that came out. Notice the date. This was one month after
I got the funding from USGS Climate Science Center to begin this research so I hadn't
even ordered the first radio collar. Hadn't even ordered...We had done nothing, actually,
on this project, but it was announced in the title that this is a disappearing rabbit,
that they're vanishing. Of course, many of you will know there's two
errors in this title. One is that these are hares, they're not rabbits. And the other
is that we don't, really, know anything at this point about them disappearing, but we
do hope to get to that point. With that, I'd just like to end by thanking
a lot of people, a remarkable group of graduate students and undergraduate students. Both
field assistants, we have 10 of them out in the field right now, four of them working
on senior thesis projects. It's been a labor of love for lots of folks.
As I mentioned, the genetic work is being done in collaboration both here at Montana
and at University of Porto where the rabbit genome is sequenced so there's this historical
reason to do that. Paul Lucaks has helped us a lot with a lot of the, really, complicated
Bayesian modeling that we have to turn to with this kind of analysis here.
Obviously, the funding and administrative support. This, really, goes all the way back
to 1998, but has been just terrific across lots of different federal and state agencies.
So with that, let me see, I'm going to check my attention meter and see...Oh. [laughs]
We've got some sleepers, we've got some people texting, but nevertheless, I'm happy to answer
questions. Wake up everyone. Christy: OK. We'll now be open to questions.
OK. Our first question is from Kevin McCarty. Go ahead and unmute your phone, please?
Kevin McCarty: Yes, this is Kevin McCarty. Scott: Hi, Kevin.
Kevin: Hey, how's it going? Scott: Good.
Kevin: Yes. My first question...Actually, I have two if you don't mind. My first question
is with the phenomenon that you found in the Olympic Peninsula area, the ones that did
not change color. Was there a recording towards what the elevation was that these hares were
found at? Scott: Yeah. I haven't particularly done any
work on hares in the Olympic. This is based on what is really well known in terms of natural
history of the Olympic Peninsula. As you know, the Olympic Mountains go really quickly out
to sea level so the hares tend to be at what we, here in Montana, would consider to be
quite low elevation. They're not found in the boreal area. They're at relatively low
elevation, and of course, it's maritime climate at the Olympic. No, I can't speak to any specifics
of elevation, but just to say that, in general, the hares are found in relatively low elevation.
They end up with many times not having winter long snowpack.
Kevin: OK. Then to the second part. I want to ask you if there was any research or any
side research that looked towards the predators that are, actually, feeding upon the hares,
if they are having any kind of effect with the climate change, as well, if that could
be any kind of contributing factor? Scott: Yeah. This is a really good question.
It's obviously a lot harder to get a handle on predator's dynamic, tracking something
like this. But John Sidle, here at the Rocky Mountain Research Station and his research
group, have been studying Canada Lynx in exactly these study areas since, basically, the same
year I started studying hares. John and his group have been studying Lynx. We haven't
formally connected that, but there's lots and lots of years of Lynx telemetry data and
we are working together. I guess, the short answer that question is not so much, but definitely
interesting and important. Kevin: OK. Thank you very much.
Scott: Thank you. Christy: Our next question is from Erik Beever.
Can you, please, unmute your phone, star six, please?
Erik Beever: Hey, Scott. Congratulations on the new position, the PNAS paper and the "Hare
Chiller." I'm wondering if that might be a treatment for baldness, as well, that "Hair
Chiller?" Scott: [laughs] Thanks, Erik. I'll look into
that. Erik: [laughs] Good. In your slide about the
projected mismatch of hares, you had snow off as a one day phenomenon. I have a follow
up question, but can you discuss that real quickly?
Scott: You mean the vertical line that was a snow on, snow off date?
Erik: Yeah. Snow on is plausible, but I didn't understand how that could be a one day phenomenon
for snow off? Scott: Yeah. Obviously, that's taken a semi
continuous phenomenon where I was showing our field data where I was showing the snow
comes, it goes, it comes, it goes in the fall. In the spring, it goes, it comes, it goes.
So it's taken a continuous event and making it dichotomous. Basically, we came up with
the criteria for continuous snowpack from the climate modeling, and we used that as
a threshold. One thing we did find, though, was those dates that came from the climate
modeling corresponded really well to our field data where we were out there every week taking
pictures of the snow around every hare. We had this nice field measure of when the snow
came and when it went weekly. That corresponded really well to the models on off dates that
came from the climate models. Erik: OK. Great. Secondly, this is stepping
back a touch. You talked towards the end about adaptability and the process either of through
behavioral plasticity or through natural selection. Can you talk about, let's say, first within
hares, which individuals might be most likely to be able to adapt? Would you come at that
from a purely genetic perspective? Also, if you want, which species might be most likely
able to adapt? Scott: Yeah. That's a great question. It's
obviously one that is a huge management relevance. It's a point that I expand on a lot more when
I give talks like this or I give climate change talks to, for example, land manager groups.
As far as I do think, it gives a ray of hope and it gives an action item that land managers
can do when they...Land managers can't necessarily do anything about carbon footprint, or carbon
credits or CO2 output. They can do something, I think, to facilitate adaptation. That is,
again, by the basic principles of natural selection, we expect the force of natural
selection to operate the best when the population is large, because if the population gets small,
genetic drifts can overwhelm selection. Maintain populations that are large enough to respond
to selective forces, that have a moderate level of gene flow among populations. That
is not so much gene flow that local adaptation might be swamped. Not so little gene flow
that adaptive variance can't arrive in a population. So those are two things, maintain relatively
large populations, relatively well connected populations and also, going along with those,
minimizing the other stressors that are operating on here. I always think about this for any
species, is being confronted by an anthropogenic stressor, the best possibility for it to adapt
is to give it more latitude for adaptation through minimizing other stressors.
Not to say that any of those three things are easy, of course, but those are action
items that people could do at a local level. As to which species, of course, for other
life history traits, obviously, things like rapid generation time, generalist life history
habit, those would also lead to more rapid adaptations as a general rule of course, as
a general theoretical rule. Hares are pretty well suited for that. Hares
aren't rabbits so they don't have the kind of intrinsic growth rate that rabbits do,
but they still are pretty well suited for rapid...They have relatively fast generation
times. They are, at least in some ways, relatively general.
Erik: Thanks. Excellent presentation. Scott: Thank you.
Christy: We have another question from Sean Sultaire.
Scott: I don't take any questions from that guy. I'm just kidding. He was one of our field
assistants. Christy: [laughs] Sean, if you could press
star six, unmute your phone? Scott: I was just kidding, Sean.
Christy: [laughs] OK. While we're waiting for him to get on, let's go to our next question.
It's Carol... Sean Sultaire: Hey, Scott?
Christy: Oh. Are you on? Sean: Did I make it on?
Christy: Yes, you did. Sean: OK. I think I pushed pound six on that
one. Great presentation, Scott. It seems like a lot has been going on since I left, definitely.
I had a question about the scale of inference for predicting future snow cover and population
dynamics, if that's going to be limited to the current study area or more broadly across
Southern portion, like Southern hare populations. Scott: Yeah, no, that's a good question. I
mean, I think to the extent that we can unravel mechanisms, then obviously, that's going to
increase the generality. I mean, if all we're doing is describing the phenomenon of increased
mismatch and mortality for hares in this one area, then that's not very generalizable.
Then we have to basically to, repeat that for everywhere in the world and every species.
But to the extent that we can unravel mechanisms of the role that plasticity might play, mechanisms
of the way in which natural selection might act to change the initiation date of the coat
color change, then it seems that it would be very generalizable.
The goal, the wonderful thing, would be to get, essentially, a measure of, "OK, with
this much mismatch, here's the force of selection, and here's the adaptive response that these
species are capable of." Even that, once you understand the mechanisms, you could start
asking that for other species with coat color change, or other species that have phenological
mismatch. Sean: Going along with that, just one more
question, if you don't mind. I know you've done some landscape genetics in the past,
across snowshoe hare range. You found for most southern populations there was not a
lot of genetic divergence from the core Boreal population, consistent with the core periphery
hypothesis for range boundary genetics. I wonder how you think that could play into
this species' adaptive response to changing snow conditions.
Scott: Yeah, I think I kept in here, I put this as an extra slide in here. Can you guys
see that? Can you see the new slide I have? Sean: It's up there on mine.
Christy: Yes. Scott: This is the landscape genetics project
that Shawn is referring to that was done by my student Ellen Cheng. It was quite interesting.
We found three distinct genetic groups the Boreal group across all of Canada and Alaska,
a Southern group which, as Sean mentioned, does have lower heterozygocity, then what
we call a Coastal group. This shows a few different things. One interesting thing that
I hesitate to say much about, but I will anyway because, hey, there's nobody here. I'm just
talking to the computer just kidding. The Coastal group includes the only hares that
we know of that retain brown coats during the winter.
This is only in review right now, but we find that there's actually introgression into these
snowshoe hares from black tailed jackrabbits, which are the only Lepus species in North
America that does not undergo seasonal coat color change.
Not to overplay it, or say that we found a silver bullet gene that black tailed jackrabbits
have given them the gene to stay brown, but it does imply that that might be a piece to
understand the evolutionary history of hares, even with respect to coat color change of
that grouping. Sean: Very interesting.
Scott: Thanks. Sean: Thanks, Scott.
Christy: OK, our next question is from Carol Mladinich.
Carol Mladinich: Pretty good. I am interested, when you talk about the changing snow conditions
and what they're doing. You say they're snow downscaling. Can you talk a little bit about
that? Is it because of the scale of the snowfall data that you're using?
Scott: What do I mean by snow downscaling? What I mean by that is, instead of trying
to connect these phenologic changes of the hares to some really big snow prediction,
like what you see in IPCC report. You know, where you see giant regions with changes in
snow cover, or you see whole continents or whole countries? Those are kind of hard because
there's so much variability within those regions. The snowpack over just several hundred kilometers
can be really different. In fact, as we found in our two different study sites, the snowpack
was really different, just because they were 1300 meters different in elevation. It's a
really broad brush trying to link biological changes to physical drivers or physical changers,
if you only have this really broad brush of regional or continental predictions of snow.
Carol: A higher resolution snow? Scott: Exactly. With the climatologists here,
we were able to come up with descriptions of the past and predictions of the future,
that were relevant to these particular animals of these particular study sites.
Christy: We have our next question. It's from chat. It's from Rachel Muir. She asks, "Do
snowshoes interbreed with any closely related species? Are hybrids viable? I have seen reference
to a Brier Island, Canada subspecies. Their phenology might be instructive".
Scott: First, was the second one, what island? Christy: Brier. That's B R I E R.
Scott: I've never heard of that. Yeah, I would love to hear about that. I've never heard
of Brier Island. Yeah, definitely, I would love to hear more about that. As for the first
question, it goes back to what I mentioned in answer to Sean's question, that we do see
a signal of hybridization from black tailed jackrabbits, ancient hybridization. I mean,
this would be tens of thousands of years ago, or more.
Some black tailed jackrabbits, we don't see that currently. That is an interesting question.
What were the conditions which led to that. Does that happen now? We don't see that hybridization
in other parts of the hare range that are sympatric with snowshoe hares.
I guess the short answer is that we don't have any reason to see, right now, that there's
hybridization from any of the congeneric species with the snowshoe hare. But, we do see a signal
that it has occurred at least once in the past with the black tailed jackrabbit.
Christy: Our next question is from Kerry Holcomb. Kerry, could you please unmute your phone?
Kerry Holcomb: My question is about your genetic analysis. I know you're just getting started
down this road, but do you anticipate that the difference in coloration is going to be
led mainly by a genomic difference, or just purely an expressional difference? Like an
embryological difference. Scott: You're exactly right. That is very
complicated. Yeah, definitely, that lies in the question that I'm sometimes asked, "Are
you going to find the coat color genes?" Because, yeah, as you say, not only is it likely a
suite of genes are involved, but also there's all these regulatory, there's lots of regulatory
changes that cascade in and make it much more complicated. I'm guessing, just based on what's
known from the genetic basis of coat color which, of course, for mammal coat colar has
been really well studied in mice and dogs and horses. The coat color, the genetic basis,
the complex genetic basis for coat color, or non seasonal, just background coat color
is pretty well understood. But, it's also known to be pretty complex.
I'm imagining that seasonal coat color will have all the complexities of the mammalian
coat color plus all the additional complexities of being a circannual process.
Kerry: Yeah. There could be some really deep methylation patterns or all kinds of different
fun stuff going on. Scott: Yeah, right. I bet it won't be easy.
Kerry: Well, good luck. Great job. Scott: Thank you.
Christy: OK. I'm just looking here at the participant list and I don't see any more
questions. Do we have more questions before we close out the presentation? OK. All right.
I'd like to thank Scott for a great presentation.