Importance of Natural Resources

A home away from home: The beneficial role of artificial structures…


Alright, hi everyone! Welcome to the
Knauss brown bag series. I’m excited to introduce Zac Cannizzo who is a marine
protected area climate specialist and interagency coordinator at the National
marine protected areas Center in the Office of National marine sanctuaries.
Zak recently earned his PhD in marine science at the University of South
Carolina. He is interested in climate change ecology and his graduate work
focused on the climate mediated range expansion of the mangrove tree crab into
salt marsh ecosystems. As a Knauss fellow in the marine protected area Center he
has continued his work on climate change by reviewing and reporting on the
impacts of climate change on marine protected areas and our national marine
sanctuaries and prior to his graduate work Zac received his Bachelors of
Science in biology and biological biological aspects of conservation at
the University of Wisconsin-Madison. Today he will be presenting a home away
from home the beneficial role of artificial structures for climate
displaced species. Thanks everyone for coming and everyone who’s attending on
the webinar I appreciate interest in this subject so when you take a look at
my title the first question that you should be answering yourself this what’s
a climate display species you probably haven’t heard that term before because I
made it up you’re not gonna find it anywhere in the literature it’s brand
new yay but it’s a really good term to describe the systems that we’re going to
talk about today and what those systems are is
essentially rain shifts climate change is forcing or encouraging many species
to shift or change their ranges away from or expand out or contract in all
kinds of different ways from their geographic range that they’ve
historically been found in mmm-hmm now this is something that we expect to
happen more and more we’re seeing it happen with a lot of species and there’s
been a lot of study on this in invasive species but there hasn’t been a whole
lot of study on how native species deal with this shift when they move into a
new ecosystem and that’s really the subject that we’re going to talk about
today most of the time when a CC shifts its
range it shifts it along with the ecosystem that it’s associated with
because most species can’t really survive out of the ecosystem that they
evolved in but sometimes you get these climate shift mismatches where a species
is able to shift at a different rate from the ecosystem that it’s
historically associated with so for example you may have a species that’s
always been found in mangroves but now it’s shifting faster than mangroves in
tons of colonizing salt marshes so these new habitats are novel to the species
they’ve never experienced them before they’re not adapted to live in them
thus the interactions that they have in these ecosystems are very likely to be
suboptimal it’s not a place that these species are used to living in they’re
not adapted to dealing with these conditions now remember this is
different from an invasive species this is a native species that’s moving into a
new area invasive species are often transported to the area by humans then
introduced to an area that’s similar enough to the ecosystem that they’re
used to that they can thrive these native species often do not thrive when
they enter these new ecosystems so the case study we’re going to cover mostly
today is this little guy here the mangrove tree crab aratus bostonia so if
you put your thumb and forefinger together that’s about how big their
bodies are not counting their legs they are in our boreal crab so if you know
how that means they climb on trees this is a clam that lives in the trees and it
hates water so it’s also the crowd that hates water so it’s really weird in
pretty much everything that it does the reason why it hates the water is because
there’s lots of predators in the water it’s little it’s crunchy its food for
everything so the fact that it doesn’t like the water is going to be really
important throughout this talk so just keep that in mind so what it does is it
climb structure it climbs up into the trees itself or whatever other structure
it can find when the tide rises so there’s historically a neotropical
mangrove associated species meaning that it’s found throughout the tropics of the
new world in mangroves but recently it’s climate rated kind of mediated northward
expansion has outpaced that of mango so you’ve probably heard how mangroves
are moving north so is this species but it’s moving
faster because of that it’s colonized salt marshes in northern Florida and
southern Georgia so this is exactly the topic that we were talking about we have
a native species moving under its own power into a habitat that it’s never
been found in before and just as predicted the salt marshes have
suboptimal habitats for this crab we see that in a lot of ways the most obvious
is these crabs are much smaller in the salt marsh than they are in the
mangroves they also have decreased reproduction potential they simply don’t
produce as many offspring there’s increased predation risk in the marsh so
even though predation risk in the water is bad everywhere it’s really bad in the
marsh these crabs I really really likely to get eaten if they enter the water in
the marsh and they lose some important behaviors such as site fidelity which is
a behavior that allows them to return to the same place every day and save time
and trying to find food so we have this system where we have a species moving
into a region where it’s never been in before
it’s a suboptimal region so this is what we would call what I am calling a
climate displaced species it’s moved there its larval dispersed these guys
don’t have any choice in the fact that they’re there they get pushed into the
water as larvae and they end up there so it has to deal with the conditions that
it’s in what about that other part of my title the artificial structures how does
that play into this well there’s this idea of artificial structures acting as
analogous habitats and an analogous habitat is a habitat that provides a
refuge for a species that would not otherwise thrive in the surrounding
ecosystem this idea grew out of the urban ecology literature because if you
think about a city city is not a natural habitat there
I mean if animals are only supposed to exist in the habitats that they evolved
in there shouldn’t be any animals and cities but we know that there are so a
good example of an artificial analogous habitat might be this pool in a backyard
backyard is not a great habitat for these toads and frogs but you put a pool
in there that’s an artificial habitat that acts similar to a pond so it might
not be ideal but now these guys can survive
an example that’s a little more relevant to DC is pigeons
so pigeons are cliff dwelling organisms in case you were unaware of them there
are no cliffs in DC in case you were also unaware of that but pigeons do
pretty well here that’s because we’ve built buildings that look a lot like
cliffs so again it’s a habitat that is similar to what the species is used to
provides things for that species that allow it to survive in a region where it
would otherwise not be able to survive all right now let’s push those two ideas
together how do analogous habitats fit in with
range edge populations so we had a lot of literature on how artificial habitats
help invasive species move forward but the problem is when we think about
invasive species we’re all we often focus on how those species impact the
habitats that they are now in we don’t often think about how that habitat is
impacting the species as native species start moving into new habitats that’s
gonna be really important we care about these theses we want to manage these
species so this idea of habitats at the range edge started to hit the literature
in the mid 2000s there was one paper in 2006 who briefly talked about it one
sentence and then this paper in 2017 this was the first really good one that
I’ve been able to find if you know of any others please let me know I would
love to hear about it this little hummingbird here the Annis
hummingbird is native to Alaska and what’s interesting is these researchers
found that these artificial feeders allowed it to expand its winter range
luces areas where it’s found in the summer so it’s not moving into a wholly
new area but because this artificial habitat provides food for this species
now in the winter it can survive that a slightly better example came out earlier
this year in – in Maine artificial reefs facilitate tropical fish at their range
this is more along the ideas that we were talking about these researchers
found that artificial reefs that were built along the east coast of the United
States we’re allowing tropical species to expand further
north than they were otherwise likely to be able to so we have a habitat that’s
purely human-made that’s similar to the habitat these species that are used to
and it’s allowing them to survive in areas that they otherwise wouldn’t be
able to survive in problem is besides saying hey it’s a habitat that looks
kind of like this other habitat what’s the mechanism if we really want to use
artificial habitats to manage these rain shifting species if we really want to
understand how rain shift our weight shifting species are affected by these
artificial habitats we need to know why they allow these species to survive in
these areas so we need to dig into the mechanisms and that’s really what I did
with our case study so the role of docks I’m introducing a third habitat so we
already have mangroves in salt marsh and only have docks in the salt marsh so you
come up into this area of the salt marsh there’s no mangroves around if say you
know low-complexity habitat about this high maybe this high with marsh grasses
no canopy and all of a sudden you see this that looks a heck of a lot more
like a mangrove than the marsh does so now we’ve fallen into this idea hey it’s
a habitat that looks more like the habitat it’s used to maybe knacks as an
analogue and there are crabs there there’s one there’s a mangrove tree crab
are they an analogue well we have our first pin here
it’s crabs are big on the docks so you can catch a crab on the dock and it will
be bigger than if you go ten meters away into the salt marsh you’re not going to
find crabs that large so that’s a good hit maybe these docks are acting as a
mangrove analog but we really need to dig into those mechanisms so we answer
it we asked a number of questions related to this big question of do docks
act as a mangrove analogue so is this artificial habitat allowing this climate
display species to be able to better persist and expand into this novel
ecosystem does behavior differ between habitats it could that’s important
behavior affects a lot of aspects of an organism’s ecology and it can often be
affected by the habitats the habitats differ in the provision of disturbance
refuge so essentially if a hurricane comes by is it better to be in a dock or
in the salt marsh is there something about those habitats that provide more
protection the differences between how to test
affect the ability of crabs to expand this is that same question with the
artificial reefs in the fish if just because there’s a dock there is the crab
likely to be further north how does the thermal environment differ between
habitats crabs are cold blood so the temperatures they experience are going
to affect a lot of different things to do with their life history their fitness
it’s too cold they might die this is a tropical species remember it’s expanding
north if it’s too warm they’re likely not going to have as enough energy left
over to do things like grow and reproduce as much as crabs and other
habitats might be able to the other side of that coin is does habitats affect
diet so these crabs feed on mangrove leaves in the mangrove that’s 85 percent
of their diet there is no mangrove leaves in the salt marsh so what are
they eating and does that differ between the dock and salt marsh habitat and
finally the ultimate question how do these factors and habitats affect
reproductive fitness so if we’re going to say that these artificial habitats
are helping these species in this new environment we probably need to test
whether or not they’re actually increasing the fitness of those species
not going to talk about the first two questions today we just don’t have time
they’re not as interesting as the other four if you want to know feel free to
look up the papers or ask me afterwards I am obviously always happy to talk
about my research all right let’s orient everyone to the study area we have
Florida in case you’ve never seen it before
Georgia in case you’ve never seen it before and here is where our mangrove
sites were on Fort Pierce Florida we had our dock and salt marsh sites up around
st. Augustine this little diamond here is really important this is the 2013
extent of this species this was the first paper to show that this species
have moved into salt marshes we also have the northernmost black and red
mangroves so yes there are mangroves in this salt marsh area but this line here
delineate the extent of the mangrove dominated ecosystem so north of that
line you are in salt marsh there are patches of mangroves here and there but
there’s not very many of them so what did I do who wants to dig into
Memphis we’re not gonna do that that’s boring I looked at crabs I caught crabs
there’s some crabs if you really want to learn more about methods and statistics
ask me later we’re not going to cover it now we’re gonna stick to the fun results
all right do docks increase expansion rate here’s that map again I want you to
pay attention to that red diamond and those two trees they are not going to
move we’re just gonna zoom into the northern extent so how do you know
whether or not a habitat is allowing a species to expand further north you do
this really crazy intense scientific method of going out and looking for them
so we’re not looked in the autumn of 2016 and look at that they are further
north on docks and they are in the salt marsh great but remember there’s a
tropical species its northern extent is really probably going to be restricted
by the winter temperatures so I went back out in the spring after the winter
had a chance to kill off some of these guys and they died back in the salt
marsh so as an active range edge there’s going to be advances in retrieves but
interestingly they didn’t die back at all on the docks so something on the
docks is allowing these species to persist in the salt marsh when they’re
otherwise not able to its that 36 kilometers further north than they’re
able to in the salt marsh itself all right one year’s interesting let’s try
again just to make sure went out again the autumn of 2017 again
they moved further north now we’re seeing them at the same northern extent
in docs and marsh that’s fine maybe these crabs from the docks
released some larvae that got a little bit further north we can’t really
identify where these crabs are coming from but at the end of a nice hot summer
they’re all the way up there anyone who was in the southeast they’re in the
winter of 2017 and 2018 we’ll remember that it was unusually cold in fact in
this area it was one of the coldest winters in 30 years so what happens to a
tropical species when it gets really cold they die they die back a lot so we
had a die back of over 80 kilometers at the range in both the doc and the salt
marsh but interestingly once again these crabs are 22 kilometers further
north on the dock than they are in the salt marsh so even in extreme years this
artificial habitat is allowing this species to persist further north than
would otherwise be able to great stop here right this this habitats doing a
great job but again we want to dig into the mechanisms so why is it doing this I
mean it’s probably keeping it 1 right I mean it’s keeping it warmer cold is
what’s killing it back and that’s that is what’s happening we stuck some
thermal loggers underneath the dock and in the nearby salt marsh and it is
consistently warmer underneath docks than it is in the salt marsh you can see
that in the real data too I mean might be a little bit difficult to see for you
guys out in the audience but even on these coldest days it’s about 6 degrees
at points warmer underneath the dock and in the nearby salt marsh right this was
an unusually cold winter it consistently got below 0 degrees Celsius the lethal
temperature for this crab is 4 so it’s getting cold even underneath the docks
and yet these crowds persisted in these docks so what’s going on you’ll notice
the squiggly little black line here never reaches 4 degrees Celsius this is
the water temperature so these crabs hate water but if it’s starting to get
cold probably better to be in the water where it’s likely to be warmer because
Robert water cools down a heck of a lot faster than air does then they just die
if it gets cold so we notice that when it starts to get cold these crabs do
stay closer to the water they move further I further shoreward and what’s
likely happening here the difference between these two habitats is that at
low tide the marsh is no longer submerged they like to hang out around
these marsh grasses so that they could climb out of the water at high tide but
at low tide they don’t have access to the water in the marsh so if you don’t
have access to the water you’re out of luck you’re dead these docks however
because they’re built for people to be able to gain access to the water
whenever they want part of the dock does remain submerged so we believe that
what’s happening here is that the docks are allowing these crabs
to maintain a warmer environment overall and then on the extreme cold days
maintaining access to the warmer water which might just be able to allow them
to survive it appears that’s the case because these crowds did survive this in
the dock but not the salt marsh all right
docks provide a warmer thermal refuge increases the speed and extent of
expansion of the salt marsh great this artificial habitat is providing
something that allows these this climate displaced species to survive in an area
it wouldn’t otherwise be able to survive what about during the summer crabs is
the salt marsh experience an environment that’s too warm it’s a tropical species
that’s a stupid question right but it’s not these crabs evolved in a forest if
you’ve been in a forest you know it’s shady it’s probably a little bit cooler
this is about all the shade these crabs get in the salt marsh when they’re up on
the grass it’s not much that that’s not helping you very much
so we asked the question during this time when crabs are forced out on the
water so at high tide it’s about six hours a day at best are they
experiencing a Worman a warmer environment in the salt marsh the reason
why that could be bad is because for a cold-blooded animal like a crab
if you experience temperatures that are too warm it’s going to increase your
metabolism more Energy’s gonna go towards that and not gonna have as much
energy for things like growth and reproduction these important things that
help keep you alive but help your species persist so how do we do this
well we paint some crafts with nail polish we release them and we watch them
to see how much time are they spending in the Sun in the shade
hey look at that if there’s no shade you spend a heck of a lot more time in the
Sun crazy right docks are shaded though they have that nice little thing that we
like to walk on so it acts like a mangrove it provides a shaded habitat
for these crabs awesome docks are acting as an analogue to the mangrove the
provide a shading habitat and this is probably the craziest graph I will show
you today it’s it’s cooler in the shade than it is in the Sun that’s all that
shows but just proving it it’s significantly cooling we’re talking ten
degrees okay so they’re spending more time in the Sun are they really any
cooler or any warmer in the salt marsh so what about that body temperature well
we took some thermal photos and found out
and yes the body temperature Krabs is cooler in the docks than it is in the
saltmarsh all right we figured out that the docks
provide a thermal refuge both in the winter and in the summer so because
these docks are providing a cooler habitat that’s thus more similar to the
mangrove than the salt marsh it may be allowing these crabs to save energy
that otherwise have be put towards metabolism they were elsewhere in the
salt marsh oh sorry what about energy intake the other side
of that energetics going maybe if you’re you know if a crab is pushing away more
energy to metabolism it can make up for that by eating more yeah that’s possible
so we took a look at that remember these crabs like to eat leaves in the mangrove
but they will eat animal material when they have the opportunity to just a heck
of a lot harder to catch a fiddler crowd that’s scurrying around than it is to go
up to a tree and eat a leaf but that animal material is actually a higher
quality diet it’s easy to just tie in calories it’s got all kinds of good fats
and proteins in it so they don’t have access to these leaves in the salt marsh
habitat or in the dock habitat so maybe they’re gonna eat more maybe they can
eat animals but you still have the problem of trying to catch them what’s
going on first question is how much do they remember we said if you’re
expending more energy maybe you can make up for that by eating more so there’s a
one time I’m going to dig into methods a little bit because the way we looked at
this was a little funky so remember these crabs don’t like the water
so as the tide rises they climb up onto the structure they also have a gut
passage time about three hours it’s convenient because the tidal cycle from
the time where the sediment becomes inundated to the time where it’s no
longer inundated is about six hours means a time that the tide is rising
it’s about three hours see three out perfect so what we did is we collected
groups of crabs and we dissected them first group we collected as the tide was
rising right before they lost access to the Sun so when you take the stomach’s
out of those crabs and look at how full they are this tells us how much that
crab is eating when it is access to as much habitat for food as it can possibly
have access to can eat things on sediment and climb into trees and eat
leaves and go wherever it wants with collected crabs right at high tide so
we’re getting here is the idea of how much these crabs are eating as a tide of
slowly rising they’re climbing up on structures so they only have access to
whatever food is provided by the structure there’s nothing on the
sediment there’s no wet areas in the mangrove I mean they just probably just
climbing up a new trees and eating right that’s fine what are they doing in salt
dock and then finally collected a group to
crowds three hours later just before they lost access to the tide so this is
as the tide is falling crabs have access to the same dry food that they did the
previous three hours but they also have access to anything that the water is
depositing on that structure and what we see here is kind of an interesting
pattern first thing I want you to take notice of is crabs in the dock in
mangrove they have consistent thoughtfulness throughout the time I
should probably orient you to this and I apologize I didn’t do this earlier the
letters correspond to significantly similar groups so if you have an Ana B
that means they’re significantly different in a na means they’re the same
so the gut fullness is the same in both of these habitats throughout the tidal
cycle awesome that means crabs in the dock and mangrove are able to probably
eat as much as they want throughout the tidal cycle they have constant access to
food that’s not the case in salt marsh during this three hours where the tide
is rising and crabs only have access to dry habitat they’re not eating as much
so they likely don’t have equal access to food now they seem to possibly be
making up for that by eating more overall that’s great so we have some
differences between these habitats more consistent access to the food on docks
which is more similar to the mangroves which is a benefit what about diet
quality so it’s all fine and good if you’re eating more but if you’re eating
things that don’t give you very much energy it’s not helpful so we took
advantage of these stomachs that we already had and we examined this
morphological ratio called carapace we’ve got width ratio yeah nice and
scientific all that means is the size of the crab divided by the size of the
stomach so I’ve progressively smaller stomach would give you a higher ratio
Mayo just thing about this ratio is it allows you
to get an idea of the long term diet quality of Kratz a low ratio means a
poor diet quality their likely high in plant material the high ratio generally
means a high quality diet high in animal material so there’s a difference between
eating celery I mean yeah we call it good for us but it’s low calorie
difficult to digest you’re not getting a lot out of that or a hamburger which is
high calorie easy to digest but crabs don’t eat celery and hamburgers they eat
marsh grass or delicious juicy I suppose or you might know them as roly-poly
bucks and we take a look at this rate relationship in crabs that’s interesting
okay so crabs in the salt marsh of the lowest quality diet fine but crabs on
the dock have a higher quality diet than crabs in the mangrove what’s going on
these things evolved in the mangrove why don’t they have a higher quality diet
there well there’s no mangrove leaves on docks but there is on docks is following
communities there are a lot of sponges barnacles bryozoans isopods crawling all
over these docks it’s easy access to animal material if these crowds can
easily catch so we think’s going on here what this tells us is that crabs on
docks are probably switching from feeding primarily on plants to feeding
primarily on animals you study this crab that’s weird
we never would have thought that was gonna happen everything in the
literature tells you these are primarily herbivores crabs
they’ll eat animal tear when they can get it but they’re not going to target
it so are we sure about this kind everything kinda spent a lot of time
watching these crabs and they eat the animal material on the docks here’s a
picture in case you don’t believe me there is one of these crabs eating an
isopod they do it but I keep drilling on getting into the mechanism so are you
gonna believe me when I’ve shown you just this morphological relationship I
mean we all know that morphological relationships can be iffy so we looked
at this again by examining the fatty acids that these crabs deposit into
their eggs okay so this has been shown over and over again in crustaceans to
correspond really well to what they’re eating they
tend to get a lot of these fatty acids from the things that they eat and you
can use particular fatty acids to get an idea of the diet of those organisms so
don’t worry about what these trophic markers are exactly just know that this
one if you have a higher value of it you’ll be lower trophic level so crabs
on docks have a very low trophic level they’re feeding more on animals than
crabs in the salt marsh on the mangrove one is unusually low we can talk about
that later if you want to but we’re focused on docks in salt marsh here but
what then our crabs in the salt marsh eating if they have a low-quality diet
they’re not eating animal material well they’re probably eating detritus that’s
what this measure tells us so to try this as dead stuff they’re eating
rotting Spartina grass they’re eating mud and more specifically the bacteria
and the fungus that grows on these things this is a low quality diet for
these prends they are not evolved to primarily feed on this so we have good
evidence here that docks provide a superior diet to the salt marsh through
increased Carnevale and crabs in the salt marsh have a low quality diet high
in Detroit’s detritus I want to pause here with our case study really quick
and just point out this is why we need to study the mechanisms behind these
artificial structures this is an unexpected benefit of the docks we never
would have expected that they would shift to a diet high in carnivore
that’s not what these crabs are known for and we never would have known that
and that that might be a benefit that they’re providing if we hadn’t dug into
the mechanisms of how this artificial habitat benefits this species so we
really need to dig into the mechanisms of these systems if we’re truly going to
understand and why am i harping on this for diet because diet affects a lot of
things for a species a high quality diet is likely to improve the reproductive
potential of an organism to improve its growth to improve its energetics you are
when we need a good diet things are likely gonna go better for you mmm so
docks provide a more favorable thermal environment more constant access to
higher quality diet so we’re getting at these mekin
we’re starting to show how this artificial habitat helps this climate
displaced species but how does this impact Fitness that’s the ultimate
question if we can sure this artificial habitat is increasing the fitness of
these animals we’ve really shown something so how do we look at Fitness
reproduction why are we production it’s a measure of relative fitness if you
have two individuals of the same species and one has a better reproduction it’s
more fit at a basic level it’s also impacted by environmental factors like
spoiler diets and thermal conditions so we know that these differ between
habitats and we know they differ strongly between habitats so maybe this
is one of the things that can affect it and importantly for this species and for
many shifting species it expands via larval dispersal so increase
reproductive potential if you create more and higher-quality larvae that’s
likely to directly affect the expansion of this species which is ultimately what
we’re looking at so if you’re familiar with looking at reproductive potential
especially for invertebrates the first thing we often look at is how much
energy is invested specifically what’s the proportional energetic investment so
how much energy are you investing per body size into reproduction often if we
see a higher what’s called ganado somatic index it’s only telling me to
say that what I promise all that means is the proportional energetic investment
in their reproduction if we see a higher value of that we often say hey that
individual has a higher reproductive potential and a lot of times we stop
there so of course what you’re gonna expect is Dax they’re gonna have a
higher investment right we’ve seen that for everything but they don’t mm-hmm
that’s weird crabs in the salt marsh where everything appears to be
suboptimal or investing a greater proportion of their energy into
reproduction so we could stop here and say all right everything we’ve looked at
it’s wrong we don’t know what’s going on what about investing energy and the
reproduction is important ultimately you want to know you return on that
investment is so we dug into that a little bit what’s the first thing you’re
gonna look at how many offspring are you producing well that’s different
crabs the document you were producing a lot
more eggs per crab than those in the salt marsh individual produces more eggs
probably more fit well you should be asking me now is how is that return on
investment if you remember our investment is proportional to body size
that’s not proportional body size these crabs in the docks are much larger than
they are in the salt marsh a larger crab is going to produce more eggs that’s
just how it works so to get at this to really get a return on investment we had
to look at the size corrected aid production we did this by taking the
residuals of the relationship between body size and clutch size if you want to
know more about what that means ask me later it’s a pretty simple statistical
technique I don’t want to waste time explaining it and boom two things here
first the mangroves produce crabs in the mangrove produce less eggs per body size
and those in the dock in salt marsh we’ll get back to that in a little
minute don’t focus on that right now I promise we can explain it but crabs on
the dock in salt marsh are producing the same number of eggs per body size what’s
interesting about that is crabs in the salt marsh are investing more energy
into a production so the dock is allowing these crabs to produce more
eggs per energetic investment than those in the salt marsh that’s pretty good
okay but why is that happening we got a look at the quality of that investment
to do that we chemically analyzed the eggs for energy content glycogen content
total fat content lipids and the fatty acid profile
that’s the mm-hmm fatty acids that make up those lipids there’s a whole lot of
literature about how the different fatty acids different ratios of fatty acids
different combinations of fatty acids kind of fact the ultimate quality of the
larva not going to focus on those two today because they were the same between
habitats so let’s keep it with the interesting ones total up the content
there you go here’s an answer to mangroves they invest a whole lot more
lipids into their eggs so they’re producing fewer eggs but they’re
investing more into those eggs they produce that’s actually a common
strategy we see in these rain shifts populations at the range cor
have a strategy of quality over quantity which is probably we’re seeing here
well is this at the range edge ie the dock and salt marsh these at the edge of
this guy’s range tell now the strategy of quantity over quality just produce as
many as you can hope that some of them survive this is a trait that’s favorable
for expanding your hmm so that’s probably our answer to why the
mangroves are producing less aids per body size than just producing higher
quality X but we see that the dock in the salt marsh same quality investment
all right so they’re produced grams on the docks are producing more eggs per
investment but they have the same quality of investment stop there right
if you haven’t gotten the theme yet we’re gonna really try and get at the
mechanism so we looked at those fatty acid profiles what’s the quality of
those lipids the reason why we thought this might be different it’s because
these are really really closely related to the quality of the diet we already
know that crabs on docks have higher quality diet than those in the salt
marsh so even though they’re investing the same amount of lipids into their
eggs they might be investing higher quality limits don’t get sticker shock
on this next slide I don’t need you to care about what each individual figure
says just notice that for every single one of these the dock bar is higher or
the same size as that in the salt marsh these are all different fatty acids that
prayer that our precursors to mmm higher-quality larvae so over and over
again we’re seeing these crabs in the dock are investing higher quality lipids
into their eggs than those in the surrounding salt marsh brain what’s the
ultimate outcome of that what’s the offspring quality if you don’t know how
to read one of these graphs will do a really quick primer on it the longer you
last the longer you survived the higher quality the larvae so crabs on the
mangrove are producing the highest quality larvae they survive the longest
under starvation the salt marsh lowest quality larvae
okay there we go quality over quantity for the range core populations quantity
over quality for the range populations but crabs in the dock at producing
higher-quality larvae than those crabs in the main growth I’m sorry higher
quality leaven those crabs in the saltmarsh
lower quality than the mangrove higher quality than in the saltmarsh awesome
that tells me doc provide an improved reproductive habitat those crabs on
docks are more thick than those crabs in the salt marsh on an individual crab
level same relative egg production for less energy higher quality larvae for a
higher quality investment and interestingly they may represent a
theoretical mid-range reproductive habitat I want to spend too much time on
this but this is that theory that in arranged shift populations at the range
edge have this strategy of quantity of equality while those at the ranch core
have quality over quantity crowding the docker at the rate of judge they’re
exhibiting the quantity thing that we see in the salt marsh but they’re
showing higher quality so they seem to be almost like this mid-range strategy
but at the range that’s important is that could increase the persistence and
expansion in the salt marsh if you have this climate displace species these
individuals that have found this patch of habitat that allows it to be more
scent that increases the overall average fitness of the population in the region
as a whole alright and over the long term may help
increase the add up to increase the rate of adaptation to this new environment to
really get into that we’d have to look at genetics I didn’t do that ask Sam to
Qin if you want to go on that one alright so I’ve talked to you a lot
about this case study I want to wrap it up really quick before we get back into
a larger discussion of those artificial habitats in this study we have this
artificial habitat of docks that are providing an improved ecology in life
history for this climate displaced crab by providing an improved thermal habitat
improved diet and improved reproductive potential mmm so really quickly going
back to those questions do you doctor buy stocks act as a mangrove analog yes
but to an extent they’re not always perfect
we don’t expect analogous habitats to be perfect if it was perfect it would be
the natural habitat of the species it’s better in some way is the diet actually
appears to be somewhat better but it’s worse in a lot of us if you noticed on
that body chart yeah the third of the body temperature chart yeah they were
cooler than in the dock there were none in the mango so it’s better than the
novel habitat but not perfect differences between habitats affect the
ability of crabs to expand yeah we saw that this thermal environment
differ between habitats yes docks provide a warmer temperature in
the in the winter a cooler temperature in the summer in the winter they’re
probably just trapping heat under their canopy which is what we see in forests
as well and can’t have that in a salt marsh that’s probably what’s going on
there does have a Down affect diet yeah low quality night in the salt marsh high
in detritus high quality diet the dock high in animal material do these factors
affect reproductive fitness absolutely crabs on bats produced more higher
quality larvae for a lower per egg energetic investment likely due to a
higher quality of investment tied to the higher quality of the diet of the mother okay so what does my little case study
mean to the bigger picture the first thing is that we really need to start
more time studying the impacts of novel habitats on expanding and invading
species so there’s a lot of work on how invader species impact the habitats that
they colonize but there’s far less work on how those species are impacted by the
habitats and this idea of habitat effects in general it’s important so if
we just looked at the salt marsh ecosystem the docks are part of salt
marsh ecosystem so if we pull everything together really a very different picture
than if we’re looking at the docks and the salt marsh is separate habitats and
for this species they are these things settle and they do not move much more
than 50 meters in their life so a crab in the saltmarsh a half a
kilometer away from a dock it’s never gonna see a dock in its life so these
are very different habitats for this species and it has very different
effects on how this species persists this is likely to continue to be true
for other species that are expanding their ranges so we really need to
consider these habitats effects and we’re studying these range shifts and
these climate displaced native species further the role of artificial habitats
and rain shifts is poorly understood but I would say could be very important I
think I’ve shown that through the case study it’s probably pretty important to
this crap with the exception of my dissertation work I have found three
studies that have explicitly looked at how artificial habitats affect the range
shift of a native species three and two of them have come out in the last two
years so this is starting to gain attention but we need more focus on this
we know that artificial habitats do create good habitat this is an oil rig
there’s a whole lot of coral on these oil rigs helping this natural coral it’s
helping this native coral expand possibly there’s some suggestion that
there might be but there hasn’t really been a good dive into many of these
questions finally and a little bit more relevant
to some of the work you guys might be doing we need to start thinking of
artificial habitats as a potential management tool often we think of
artificial structures we think of them as being unnatural as being bad and it’s
thus just to get rid of them like this oil rig on the top just completely
remove it it’s no longer in use get rid of it more and more others this call to
see how these artificial habitats may actually be improving habitat in the
area and for range shifting species this could be particularly important I’ve
shown you that an artificial habitat has the ability to increase the fitness and
persistence of a range shifting species in a novel habitat now it’s much easier
to remove build move in artificial habitat
to plant a whole bunch of mangroves in the salt marsh say for some crazy reason
you really wanted this crab to expect so I’m not saying focus all of your
management time on whether or not you’re going to build their move and artificial
habitat I’m just saying when you’re thinking about managing these species
and the effects of climate change on them especially if they’re shifting
their ranges just keep in the back of your mind that there might be an
artificial habitat out there that is aiding or hindering that species and
maybe that’s something to consider in a management approach all right I hope
that I have been able to convince you that artificial habitats aren’t all bad
and I hope that I’ve shown you something at least a little bit interesting it
didn’t get too bogged down in the science and with that I will show you a
picture of a spider eating one of these crowds to get you an idea of how big
they actually are and ask if you have any questions yeah so the question is
when you sorry I gotta go back to a figure here the question is when we’re
looking at are we actually looking at the difference between did we look at
any differences between what we find on the growing on the docks when we find
growing on the mangroves and if things are similarly growing on mangroves why
aren’t the crabs eating those is that more or less looking at and the second
question was I followed us well you also said why would yes and the other cost part of that
question was we showed that the quality of the larvae on the docks was lower
than in the mangroves so why would that be is it just due to a difference in
genetics of how these crabs invest their energy so the first question of I the
difference between the following communities I kind of briefly said I
might come back to that here that trophic level for crabs in the mangrove
is a lot lower than we would expect it based off the literature I only had a
certain amount of time in my dissertation so I didn’t dive into it
and I would have liked to I suspect that they are actually eating far more animal
material in the mangrove than we give them credit for a lot of the studies
that have looked at how much how much they’re eating as far as plant
nanomaterial have done visual inspections of gut content that’s great
the problem with that is soft material digests much faster it’s much more
difficult to identify and thus it’s montt you’re much more likely to get a
false negative on animal material because these crabs do not eat the hard
parts of the animals that they kill you’ll notice in this picture it’s not
eating the carapace it has ripped the carapace open and it is only eating the
soft parts so I suspect if we started doing some more say stable isotope
analyses on these crabs we would find they’re eating far more animal material
we give them credit for there’s some evidence for that in the sister species
in the Pacific where we see that they have a much higher they have a higher
proportion of annual material in their diet than those on the Atlantic and
that’s because someone did a stable isotope analysis on their diet so that’s
the answer to that question I think we are actually seeing higher proportions
in the mangrove as far as the larval quality hmm I have two answers to that
the first is that these crabs in the dock are still on the range so we do
expect them to have a bit of that strategy of producing more offspring so
they’re going to invest overall less than to any individual egg which is
going to lower the overall quality additionally these crabs did evolve to
feed on mangroves and they’re not getting those mangrove
leaves in the dock so even though you have this high-quality animal material
there is like there are likely some fatty acids that they are evolved to
have and evolved to use and invest in their larvae that they’re not getting in
particular this one here a la Alpha linoleic acid it’s an important omega-3
fatty acid for larval development and it’s much higher in the mangroves the
reason for that is it’s in really high quantity in quality quantity in mangrove
leaves so this is something that we would have to dive deeper into to really
get a for-sure answer on the mechanism and that but I suspect that part of the
reason on top of the greater investment the quantity of offspring is that
they’re just not quite getting the exact type of diet that they would need to
have the highest quality linemen possible is that like the population so
the question is do we have an idea of how connected the environments are and
if there’s any differences in the population sizes diversity in the
genetic diversity in the populations um a little bit of yes yes to both of them
with a with a caveat so there was a study done by the person who preached
found these crabs in the salt marsh was in the same lab that I was in just
before me she did a genetic study it’s not published but it is in her
dissertation so you can find the publish publication of her dissertation it’s uh
Megan Riley and her dissertation would have been 2015 I believe someone’s gonna
tell me wrong on that but that’s okay so Megan Riley and she did a genetic
study along the Florida coast up into Georgia using COI one markers to look at the
diversity what we found was that the populations along the Florida coast all
the way up to Georgia were all more similar to each other than you even have
between southern Florida and the Florida Keys so it appears that this is a very
genetically connected population the kind of somewhat add to that is that
there have been some questions as to whether or not that is the correct
marker to use in a range expanding population so maybe there’s slightly
more genetic diversity and differentiation than we see we’re not
really sure they aren’t probably pretty well connected because in general in
general the flow of the current is the flow of the currents with tidal flushing
is generally northward so what we think is happening is that we get enlarged
flow of larvae northward into these environments so there’s probably
constant receding from the mangrove especially in these further south salt
marsh environments when you start getting into the very range edge there
might be a little bit more of a there might be a little bit more of input from
those populations that are in the salt marsh and dock as far as the genetic
diversity of the populations we simply don’t know besides that one study there
hasn’t been much study on it on this crab at all this is a crowd that’s noted
in the mayor of community for being important but on the general scale
people don’t care about this crime which is one of the reasons why I was able to
get permits to go out and you know collect a bunch of them they’re not
equalized they’re not economically important they’re ecologically important
in the mangrove but not the salt marsh so that’d be great to find out and
that’s actually something that I would like to do is do a micro satellite study
at the range edge and see if we see some differences great
snips even better awesome I’m not a geneticist at all so since I said I look
at so regarding the larger crabs and docks
personal assault march could further into larger crabs are on the docks
because they’re capable to defend the territory basically is it those
defending territory player role or is that behavior not so all those crafts
these crabs are not territorial they do one of the papers that was in the
behavior one is they do have ritualized aggression but that’s just kind of
establishing hierarchy these things are incredibly dense on the trees and in the
docks not always so much in the salt marsh which is interesting so you can
and sometimes even in the salt marsh when the tide goes high you’ll see five
or six of these within three or four inches on a piece of grass they they
don’t really defend territory so much and does that expansion displays others
yes and that is see that is the other side of this coin where I’m sitting here
just trying to advocate for the thing that people think of less which is the
potential benefits of artificial habitats there are a lot of things that
they do that aren’t good to our natural communities one of them is that they do
tend to favor non-native species especially invasive species and we do we
haven’t looked at it yet but we have some very circumstantial evidence that
Doc’s may be uh that this crab may be displacing squareback marsh crab our
Massey’s sinner era in the northern part of its range they do this these two
crabs do coexist in the mangrove they segregate spatially but once you get
north of where the mangrove tree crab has found the squareback marsh crab is
found throughout the entire tidal range of the marsh when you get into the area
we also see this mark this off mangrove crab
you start to not see the are Massey’s square back wash crafts so much in the
low intertidal so that may be happening we haven’t looked at it scientifically
yet but it’s definitely a possibility it does not so no it does not we did take a
look at that we also took a look at the timing of the reproduction and all of
that the the reproduction stuff that I hit on is a what I touched on was a very
small part of a much larger study that is currently in review but it doesn’t
appear to affect the incubation time at least as far as we can tell they don’t
have differences in the timing of when they reproduce when they release their
eggs any of that so this kind of hits back on that previous question as well
where it is definitely possible that aiding this species expansion into this
new area is going to displace a species that is already there they might end up
competing as we as we possibly see with this mangrove crab and the squareback
marsh crab that is definitely something to consider the thing that I just want
to try and get across is that in these management considerations and when we’re
studying these things sometimes we do have to make the hard choice between one
species or another no one’s gonna choose this crap no one
cares about this crab I know that it was a good study system to show what’s
happening but if you do have to make a choice between say a threatened species
that’s that’s shifting its range it might not be expanding it maybe it’s
contracting it no maybe it is expanding maybe it’s moving its range say up a
mountainside and if you install some artificial
habitats it’s going to allow it to persist better but it’s going to have a
negative effect on the species that are already there that might be one of those
tough management strategy management decisions you have to make and
unfortunately climate change is going to force us to
have to make these decisions so in my opinion it’s better to get out ahead of
it and start studying the mechanisms behind what might be happening so we can
make an informed decision when it does come to those decisions Thanks anyone if
anyone has any further questions feel free to shoot me an email always happy
to talk about this


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