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Today we will be talking about venomous species
and in particular about venomous snakes.
Vasco's Video blog #6: Evolution and distribution of venomous species.
This is actually a video response to a video
made by Derek from Veritasium a few days ago.
And he was asking like some other people
why it looks like that venomous species
are more common on hot countries.
I really think you should check out the original video over here.
Its really cool.
Derek starts of the video by showing a map
which shows the hot areas on this earth and the cold ones.
And then he also made a map indicating the number of venomous species per country.
However, the problem with this approach
the data is not normalised for the total number of species found in each country.
Because the general trend, from the poles to the equator, you will find more and more species
so the biodiversity is increasing.
This of cause is not the case for all regions
so in a desert you wound find so much animals.
But its a gerneral trend.
As Derek later points out in his video
there is no real trend with temperature and the number of venomous species found in a country.
However I still would like to criticise some problems with this approach.
One big issue is the counting by country borders,
If you just count the number of venomous inside one particular country.
because the distribution of a species goes across the border of contries.
If you want to find a trend in the distribution of venomous species
you should rather look at climate zones.
So as you see here on the map you have the tropics and deserts and tundra and so on.
And most of the time
species have a specific habitat that lies somewhere in those regions,
or you might even want to break it down further in more detail.
By looking at those climate regions you might be able to find a trend at all.
I'm not sure if someone has really done this,
but I think it might be worth a try to do some research on this.
I think the biggest challenge if you want to do some research on this
would be to get reliable data, and also you need to have quite a lot of data.
Another problem is, if you count the number of different species
I would say you should rather take a look at the number of independent evolutions of venomous species.
For example if we have one snake and it evolves a very strong venom
it might have an advantage compared to other non venomous snakes.
Our one venomous "hero" snake will flurish and expand its range across a big landscape
and then it might happen that this species might split into several species
if you differentiate into different niches and you have some evolutionary factors going on.
So this could have happened a few million years ago or even longer.
And today we take a look and we find 5 snake species,
who have all evolved this venom.
But in fact it was just one ancestor species.
So we really should take a look at the relatedness of the venomous species
and see if they all have one common (venomous) ancestor
because then I would rather count them as "one" rather than 5 different venomous species.
Because once you have evolved a venom
its quite easy to radiate and split into different species.
I would take a look at the species histories
and look for points where the venom has actually evolved.
This way we might be able to find some ecosystem where venomous species are more likely to evolve
and we can find the mechanisms that lead to those evolutions more frequently, if there are any at all.
In the last part of the video Derek is talking with experts about snakes in Australia.
They were wondering why some snakes are really venomous
so if you get bitten you very certain will die, and some
are just not so venomous, so if they bite you it hurts but you will survive for sure.
So how can it be that some snakes are very venomous
and some others are not, and they live in the same area.
I think that the snake and predator interaction could be the answer to this question.
We have here our venomous snake ant its predator.
Lets just assume its a fox for example.
And now they will engage in a dramatic fight
and there are basically two options:
The venomous snake will manage to bite the fox
and the fox will die because the snake is very venomous
or the fox will eat the snake.
But if we now take a look at the same situation
with the snake that is not very venomous.
If this one bites you, it just hurts a lot.
It can go two ways again:
First the fox can still eat you, because you as a snake are not skilled enough to defend your self.
But if you are a very good snake, you might be able to bite the fox.
Now the fox will be in a lot of pain, but hey, it will survive.
But I think foxes are quit clever, so this one fox that you have bitten
he will be for sure remembering that you are a very nasty snake
to attack you can result in a lot of pain, so
I think maybe next time he will avoid you.
So by not killing of you predator
you introduce some kind of learning effect into our fox.
I think after a few engagements the fox will quickly learn that its not worth attacking you as a snake.
The big problem is however if you are very venomous
that the fox has no chance to learn
he will eat you or he will die.
Of cause a lot of factors play into those interactions
and this is dramatically oversimplified.
If this system works for you as a not so much venomous snake
depends of cause on your predators.
And it even could benefit you as a non venomous snake.
Because some predators might avoid all snakes
and not differenciate between different kind of snakes.
The next strange thing was,
Why would a snake that is venomous actually lose its venom
and became a non venomous snake?
Because you would think its kind of advantageous and you don't have a lot of cost producing the venom.
So why would a snake evolve this way?
Because they talked in the video about
how a lot of snakes in Australia are now non venomous but had venomous ancestors.
I think the answer to this problem is relatively simple.
You can afford to louse your venom if you don't have the problem with predators.
Or maybe you change your behaviour or your home range
or you change some factor that allows you to survive even if you are not venomous.
This could be the case for example, if the predators around you avoid all snakes completely because of your venomous friends.
However its not like snakes choose to not be venomous any more, this of cause has to evolve.
And the thing with venom, even if its not very costly you still need to produce you venom.
And for that you need a blue print, like a cookbook that tells you how to make this delicious venom.
And every snake is very lucky to have blue prints to produce the venom, and this is the DNA.
I would assume that quite a lot of different pathways and enzymes are needed to create these venoms.
And the big problem is, that if something in the pathway mutates
that you can't maintain the pathways any more
so its kind of an error in your enzyme and it stops working.
So if you have a mutation on the wrong point in your DNA you will lose your venom.
This is kind of a problem if you need your venom.
If you have predators that are attacking you, and you really need to be a venomous snake to defend against them.
However if you don't have this pressure
if you don't have the pressure by predators or some other factors
to really keep your poisonousness
mutations in genes responsible for your venom pathways
will really quickly laed
to a non venomous snake.
So those were just some ideas, some hypothesis that might explain the patterns we find.
Or maybe I'm completely wrong, I'm not a snake expert.
But make sure to let me know in the comments below
what you think about it or maybe post you own theories
As always, thanks for watching. I see you next time. Bye bye.
Next week I will be talking about dinosaurs and why they went extinct
however I can only do this if I can get behind the paywall of the magazine Science,
because there was a nice paper published a few days ago
and I need to se if I can get a hold of it some how.
So until next week, bye bye!