Archive

Posts Tagged ‘behavioural ecology’

Resurrection Biology Part 2: On Mammoth Steak and Coral Reefs.

January 26, 2014 Leave a comment

It seems there is a larger conversation to be had about the notion of resurrection biology. A friend of mine and I had that conversation after I posted up my last blog post. I thought it was that fun that I would do a follow up post on my thoughts regarding two issues he raised in that conversation: resurrection biology for food production and ecological services.

Food Production

The whole reason for this section is this comment:

Another potential use of resurrection biology which I think most people would object to is farming; imagine mammoth farms, admittedly their natural behaviour wouldn’t be as great, their habitats altered, but considering how many farm animals have been altered and placed into habitats we have designed it does seem a viable option for extinct edible megafauna. – Washington Irving

I don’t think I need to tell you that the human population is growing, I hope it’s also self-evident that the population increase has sped up over time. To demonstrate, the time it took to go from 1 billion to 2 billion was 123 years (according to United States Census Bureau (USCB) data) while the time from 6 to 7 billion was 12 years (again, USCB data) and it’s estimated we’ll pass 8 billion by another 16 years (you guessed it, USCB data). This last one actually surprised me but it seems that we’re living in an age in which, due to an ageing population and an increased life expectancy for children and infants, the rate of growth is finally sloping off. All these extra people need a place to live and food to eat so, maybe if we resurrected extinct species they’ll provide the food we’ll need?

I would be inclined to think not and here’s why: First off, you have to actually make a population of organisms from scratch, which is no small task, take a look at conservation and reintroduction efforts across the globe and how much effort has been put into these programmes to see why this is difficult. Secondly, we would be producing food from an organism that, potentially, no human has eaten before so there would necessarily be testing required to see if this food is a healthy alternative to currently farmed species. This is closely related to another point, the fact that these foods would fall under the domain of Genetically Modified Food and here we open a hornet’s nest of political debate on the nature and safety of GM food which I’m not going to wade into here, except to say that it would make some people hesitant to buy into the new food source.

The example species Wash gave for the possibility of farming extinct species was farming Mammoth for steaks. Unfortunately, this is a terrible example for the potential of resurrected farm animals. Mammoth are close relatives of Elephants and as such we can say with a level of certainty that they would be long lived, slow to grow and, what is called k selected which essentially just means that they have relatively small numbers of children, perhaps one at a time which are then cared for by parents or members of a group; the opposite is r selection which is where many offspring are born all at once and are typically abandoned to fend for themselves.

Source: http://sprudge.com/saturday-sept-th-san-francisco-huge-block-party-with-coffee-bar-sf-and-scout-mob-plus-ribs.html

Unfortunately, this might not be feasible.

What this means is that it might take a decade to grow the initial population of mammoth to adulthood and then you’d need to leave many of them alive to produce the next population. Mammoths would also require huge tracks of land to maintain their population with tonnes and tonnes of grass every day. So there are quite a few problems I can see, my final problem is that the economic costs are really quite high given the genetic meddling needed, the set up of the population et c. but are there any cases which would be suitable for resurrection farming.

Now to raise a point I didn’t realise until I started typing up this post which is the fact that we don’t even need to resurrect extinct megafauna to farm, we could equally easily resurrect extinct plants, or fungi, or yeast or any living thing which we have records of their genetic material (Mesozoic organisms are apparently too old for this, sorry Jurassic Park). It’s possible we could develop an extinct species with higher yields than current farmed species, or with different nutritional benefits. It seems to me that the possibilities here are basically the same as with the genetically modified crops which we are already developing and that extinct species won’t really add anything to their potential.

There is one example that I’d mention for it’s possibilities, which is the Gros Michel, this is a banana variety which was used until the 1950’s when it was devastated by a fungal infection which spread extremely rapidly due to the low genetic diversity of the variety. Everyone switched to the Cavendish cultivar and now the only legacy left is the banana flavouring which is still the same as when it was developed to taste like the Gros Michel. The possibility of bringing back species or cultivars devastated by diseases gives hope to the extremely homogenous cultivars used today, because were they wiped out, it might be possible to resurrect them based on this technology.

Source: http://tangerinetravels.blogspot.co.uk/2011/02/am-reading-banana-fate-of-fruit-that.html

Spot the difference.

Ecological services

The other half of our conversation was on the potential to help with problems caused by extinctions, such as the destruction of species which provide what are called ecological services. Ecological services are basically things which species naturally do, which benefit human society, the canonical example being bees pollinating flowers of crops but there are other, more subtle ecological benefits such as the protection forests provide against flooding.

So what if there are species which used to exist which was better at providing some ecological services than current ones, perhaps there is an extinct species of tree with roots particularly adept at drawing up the water during floods but does not dry out the soil too much when water isn’t quite so abundant. Conditions on this planet has varied so much that it’s entirely possible such species have existed.

The difficulty I see with this plan is that you first need to resurrect the species and then see how it would interact with an ecosystem before introducing it. This would mirror the process already used to determine if biological control agents introduced into new environments would potentially become invasive and harm the ecosystem more than it would help. So given the added cost of trying to create a viable population, nearly, from scratch you then have to make sure you’ve not resurrected a species which is going to oust other members of the ecosystem you intended to fix.

Source: http://www.bioimages.org.uk/html/p7/p71469.php

Imagine the Harlequin Ladybird was extinct and we thought we’d reintroduce it to control aphid populations.

The final point I think which would probably be raised first by others, again it is quite Jurassic Park: The species went extinct for a reason, maybe it should have stayed that way. While I don’t personally believe in a grand plan for evolution, I could modify this argument to the notion that the environmental changes which caused the species’ extinction in the first place could still be in effect and so the species would be doomed to extinction all over again. This would be my response to my friends comment:

I think it depends also how you would re-introduce extinct species, as some are able to readjust to natural settings after human interaction. I’m thinking more along the lines of coral reef communities where some species will go extinct and if these can be resurrected it’d be extremely useful, even if it is in potential new habitats due to warmer oceans… – Washington Irving

It’s possible we could reintroduce species such as those coral reefs which Washington mentions but the result could be another extinction all over again. Even if we got everything right, we cannot be sure that the species would provide the ecological services we want and that they would not be destroyed by some process, whether artificial or natural.

In the end, the only use I can see for resurrection biology is for the purpose of maintaining species which already exist as Washington says:

I’ve wondered at times how species could be integrated into existing areas, and the only result I see is that the competition negatively effects the previous community. […] I still think that resurrection biology would have a potential use primarily for helping current species with low populations and natural behaviours which are known be able to recover or even to try and mitigate losses from global warming and ocean acidification events. – Washington Irving

If we can maintain the species which are at risk today, that is the best outcome for resurrection biology. We aren’t here to fix the world, the world isn’t broken, the problem is that it may become just a little less interesting if we allow processes currently shaping our world to continue along their path.

Advertisements

Resurrection Biology and Behavioural Ecology

January 26, 2014 8 comments

To begin with, I think it would be best to ensure that you know what the hell resurrection biology and behavioural ecology mean before we move onto why this is interesting and important. So, resurrection biology is the notion that we can create a real-life Jurassic Park of extinct animals, or reintroduce extinct animals to an ecosystem by reconstructing their genetic code and then incubating the resulting egg in a related organism. Behavioural ecology is the study of what animals do and why they do it, instead of asking ‘does an animal have horns?’ it asks ‘what do the horns do?’ and this question may have different answers for different organisms, for some it might be defence against predators while for others it might purely be to display the health and vitality of the animal.

Now, why are these two fields important to each other? Well, it has been suggested that we might be able to reintroduce, for example, dodos, woolly mammoths or thylacines (Tasmanian Wolves) to their old ranges. It comes up in the news every now and then and every time it is, they rarely discuss the ecological implications of such a reintroduction could cause, at least that is my faint impression from the back of my hermit’s cave.

Source: http://forum.phish.net/thread.php?thread=1375181970

Imagine these guys roaming across Russia, Northern Europe and Canada.

First off, let’s talk reintroductions of endangered species. Endangered species are notorious for causing problems for people trying to help them survive. The image of giant pandas stubbornly refusing to mate comes to mind. A study by Jule, Leaver and Lea entitled “The Effects of Captive Experience on Reintroduction Survival in Carnivores: A Review and Analysis” found

the results of the ANOVA show that wild-caught carnivores survived significantly more (53%) than captive-born carnivores (32%), F(1,4.66) = 17.697, p = 0.01.

For the uninitiated, this means that animals caught from the wild and introduced to an area where they had been wiped out were nearly twice as likely to survive as those born in the zoo. Now, this is a very good example study to illustrate my point, which is raised probably more eloquently in the paper, that the behavioural ecological differences such as confidence near humans, feeding behaviours et c. (Though it is very important to point out that the paper did not look into these differences, doubtless due to the lack of data available on this matter) can potentially have a major impact on the survivability of an animal being reintroduced into habitat. And these are animals which are still alive and so have parental guides to how they should act!

Imagine a dodo, now imagine all the things it does in a lifetime, are you sure your imagination is entirely accurate? This is the behavioural ecological problem for resurrection biology: we don’t know how to create the environment which a dodo would develop in so would we actually make a dodo? This point is pretty Jurassic Park, I cannot find the quote online but I believe Dr Alan Grant, in Jurassic Park 3, says something to the effect of “the genetic creations of InGen are not dinosaurs, the last dinosaurs died out 65 million years ago” and while this is not entirely accurate, many dinosaurs continue to thrive today, it’s just that they are covered in feathers and restricted to the dinosaurian group Aves, the birds.

Source: http://aliceinwonderland.wikia.com/wiki/The_Dodo

Ok, so maybe they didn’t smoke pipes and wear waistcoats and wigs, but we cannot be sure of other, less stupid, behaviours that the dodo may have performed.

Getting back on the point, behavioural plasticity within a species is quite high, especially in birds and mammals. I would provide definitive evidence for this point but I don’t know that a study exists which has looked at the plasticity of development in large groups of animals and found this. It’s more of a theoretical argument which, while not as good as a study, is a starting point. Feel free to complain to me that my hypothesis is inaccurate because X, Y, Z. So my reasoning for increased behavioural plasticity in mammals and birds is the fact that there are many and varied studies on many different species of bird and mammal which showed their ability to learn and adapt their behaviours according to the requirements of their environment. The reasoning for the behavioural plasticity of all animals is that it seems far more likely that every species will have at least one epigenetic process involved in their development and thus plasticity in final form. I hope this reasoning is strong enough to stand on its own until some concrete evidence is found to swing the facts one way or the other*.

To move on, the ecosystem which an extinct animal used to be a part of may not exist any more, many species that have been pushed to extinction by humans, went extinct because of habitat loss. Here I would say that the link is difficult to establish so once again, this is me armchair ecologising (Totally a word). But it is reasonable given what Brooks et al. point out about biodiviersity hotspots in their abstract:

Nearly half the world’s vascular plants and one-third of terrestrial vertebrates are endemic to 25 “hotspots” of biodiversity, each of which has at least 1500 endemic plant species. None of these hotspots have more than one-third of their pristine habitat remaining. Historically, they covered 12% of the land’s surface, but today their intact habitat covers only 1.4% of the land.

To understand this, endemic means ‘only found there’ so, for example, kangaroos are endemic to Australia. Biodiversity is a measure of how many different types of organism are in a particular place, so a rainforest is more diverse than an ice floe. Look at it this way, hotspots of biodiversity are like cities full of different people and if we destroy a city, we kill many more unique individuals than if we destroyed a farming community. Even before we made the mass migration into cities during the Industrial Revolution, even though most people would live in a farming community, because they are so diffuse, less people would die if the same area of farmland were destroyed compared to a city.

So the lack of good habitat would make reviving a species a mute point, not to mention that the lack of habitat might mean that symbioses, predator-prey relations, parasite-host interactions and so on that were present in the animals’ original ecosystem that the animal would not survive in an equivalent ecosystem, such as moving an Orangutan into the Amazon.

To conclude, I would point out that my career in behavioural ecology is probably not even in its infancy, it’s gestating still, and these are the problems I could rattle off. Perhaps given a more skilled or experienced mind, a brighter mind, there are even more issues which could arise for the field of resurrection biology from behavioural ecology.

I hope this hasn’t been too boring for my first post of 2014 and that it gives someone, somewhere a few fun and interesting things to think about, if it has, let me know, if it hasn’t, let me know, feedback is how I can make this blog something worth reading.

*Just a note to say that my suggestion in this paragraph is exactly that, it is a suggestion, it is not a theory, theories require evidence and testing and a whole bunch people doing their utmost to tear it down, and then failing. Theoretical does not mean theory, it means that based on my understanding of how the system works, this may be true; theoretical work is based on theories and experimental work is based on theoretical work.

On spirals, stripes and zigzagging.

October 28, 2012 Leave a comment

So this week I thought I’d take the time to go into a bit of depth about what I was looking at for the dissertation I completed for my degree. If you’re not interested, I’m sorry to hear that, go be boring somewhere else. It’s all about moving, particularly, moving in ways listed in the title, spirals, stripes and zigzags. In order to understand this however, you need to understand the details of my dissertation.

Nah, just kidding, but it would be good for you to understand the background of my project because my work is based on the hypotheses of a few good men. It is based on the fact that in the fossil record there are remains of what was originally thought to be seaweed but which were later reinterpreted as the tracks, trails and burrows of ancient sea creatures. Think about the last time you were on a beach, you know that worm cast? Well that’s because of a ‘U’ shaped burrow of a worm which it uses to collect nutrients by passing water over it’s gills through the burrow.

Worm Cast: This stuff is the sand pushed out of the back (On the right) of the burrow (The front is the hole on the left) to make room for the worm. Source.

Okay, now imagine that worm lived millions of years ago and the sand it burrowed through was turned to rock and the burrow remains as an imprint in the rock. This is one type of fossil which has been studied, the types that I studied where probably made by a species which crawled across the ocean floor, grazing. These patterns changed of the course of history, the first recorded paths are quite ancient, I believe the earliest ones I found in the literature were from the Silurian period (in the region of 450mya, for contrast, humans diverged from chimps around 4mya).

The Silurian Period: This is the geologic time scale, Earth was fully formed by At the very bottom on the left. Animals evolved around the start of the Paleozoic (In blue) and all the time since then has been expanded on the right. The Silurian is the 3rd period from the bottom on the left, the dinosaurs fit into the pink section on the right; all of human existence fits into the Quaternary at the very top of the right. Source.

So these things have been around a while, but they’ve not been idle, oh no, there are several different groups of fossils, some with spirals, some with zigzags, but they didn’t start out that way: The first records are simple stripes which overlapped a lot. Then millions of years later, we find record of some with loose zigzags and some with loose spirals. Millions of years after that there is record of tighter zigzags and very tight, double spirals. Millions of years after that and we’re around the time when mammals are about to take centre stage as the largest animals on the planet, and we find tight corkscrews drilling into the ocean floor.

Trace Fossils: So called because they are the traces and tracks of animals rather than their bodies. This is from Raup and Seilacher’s original paper, the left side shows the fossils they based their model on and the right shows what the computer model did. Source.

My work was based off of this and the Prescott and Ibbottson paper I got the picture above from. Along with a paper with the wonderful title ‘In Search of the Optimum Scumsucking Bottomfeeder’. The question is: Why bother to make yourself able to develop such complex patterns as that double spiral? What is pressuring these creatures to develop the complex neural pathways required to make such patterns? Well Hayes in the paper named above suggested that the ocean floor is a uniform resource and the best tactic is to just munch on the resources as you move along it and the more efficiently you use up the space, the better off you’ll be.

Well I think that’s a good idea except I was convinced of the patchiness of the resources, the ocean floor isn’t uniform, far from it. In the end, I decided that a strong contender as one of the reasons for the behaviours would be competition from others. In other words, the population density within an area would mean that the organisms would be all crowded together to a certain extent. This crowding would mean they should watch out for where they move because if they move over an already grazed patch, that’s a waste of the energy used to move over that patch.

I tested the idea by looking at the various behaviours and how Raup and Seilacher suggested the decision tree would work. I built a whole bunch of different behaviour sets based on how they would move in a free environment without depleted areas getting in the way; I also behaviour sets based on how they would react to the path they were moving along being obstructed by depleted patch. The pictures below should illustrate what I mean:

Movement behaviours: The three different ways that the organisms would move, there was (a) the straight path (with a little wobbling because nothing in nature is perfect); (b) the curve, the organism would gently turn as it walked; (c) the zigzag, similar to the straight path but after a set number of steps, the creature would reverse it’s path. Source: Self.

Reaction behaviours: These three are how the organisms would react when they came across a depleted patch (Which if all the world is filled with food, would only occur if another organism has already grazed the area and represented by the horizontal arrow. (a) the simplest option is to do nothing about it and keep going with your movement behaviour; (b) a more complex choice is to look out for it and when you see a patch ahead, turn a fixed amount and then carry on with your movement behaviour; (c) this is the most complex choice, in it, the organism attempts to follow along the edge of the already depleted patch and graze alongside it. Source: Self.

The next step for me was to simulate what different populations would do given these behaviours, so if there where 10 in an area, how much food could each gather under each behaviour set (Each model organism is given one movement behaviour and one reaction behaviour to use and I chose to make each population run just one of each of the nine combinations) then compare that with 20 in the same size area, and 30, and 40 all the way up to 900 (Just looked that up in the file I used to record all of this and it turns out that the file was created 29/10/2011 what a coincidence). So because the size of the area was the same for each one, I was looking at population density and what happened to the benefits of each behavioural set.

The short story is that after I collected something in the region of 3.5 million data points, I used some basic statistics and discovered that the reaction behaviours that tried to avoid the paths did VASTLY better than the one which didn’t avoid the paths at all at high population density. So if there’s lots of competition about, it pays to be smart about where you’re going. But at low population density, the reaction behaviour of ‘keep doing your movement behaviour’ did at least as well and often better (Depending on the movement behaviour) than the more complex reaction behaviours.

The reason for this, I think is that when there’s not many organisms around, it doesn’t matter if you go over a track every now and then, if you try to ‘take evasive maneuvers’ you’ll end up staying nearby to an area which has already been grazed on whereas not reacting to the grazed areas, you end up heading out to ‘greener pastures’ and not running into the paths again. It also seems that population density did have a significant effect on these ancient animals’ behavioural effectiveness. As for why all this matters, well, that I think I’ll save to waste your time with on another post.

On Deep Sea Grazers

This may not be a particularly interesting post for the vast majority of people but it’s one that I care about, it’s going to give the background to a dissertation I’m writing to hand in in the next two weeks (I handed it in on April the 27th). Everybody in the house interested in paleoethology, ichnology, evolution or deep sea worms that evolved around 542mya and have continued up to the present developing more and more complex grazing behaviour give me a hell yeah?! Ahem, yes well that’s what this post is all about so read on if you’re curious.

So how do we know that such behaviours actually exist? Well Ichnology, specifically paleoichnology is the study of trace fossils, fossils which record the tracks and trails of extinct animals, for instance Dinosaur footprints are on type of ichnofossil (Another name for trace fossils). Ichnology is the study of all tracks and trails and neoichnology is the branch of ichnology which focuses on extant (living today) animal tracks. There are fossils which record the movements of animals and they can be grouped by what sort of behaviours produced them. The particular group I am interested in are the group ostentatiously called Pascichnia (Pass-ik-nee-ah, I think). It literally means grazing tracks (Latin Pascos lit. Grazing Ichnos lit. Track) how inventive of them. If you want to know more about the inventive naming system, google the name Adolf Seilacher, he came up with the original categorisation system.

Pascichnia have been discovered from some of the earliest periods in history, the first fossils were simple and looked much like childrens’ scribbles, think what you did as a kid in MS paint scribbling randomly then colouring in the gaps between the lines. They look much like that but in rock and less colourful.

The next stage along was a couple of hundred million years later when the animals had learned to loop back and forth (This is but one example) but the loops were quite loose and there were often large gaps before the animal moved back to follow alongside it’s path. The final part of this example I will describe is those trace fossils which have been found from the Cretaceous, again, a few hundred million years after the previous ones. These showed a very tight strafing pattern back and forth minimising the area left unused by the animal.

So the patterns have gotten more complex, but why? There has to have been some sort of pressure to force the worms to develop more complex behaviours. It is possible that the behaviours developed by chance, that is, genetic drift in the development of their neurons would develop such behaviours, however there are a couple of reasons why this is unlikely.

First, neurons are expensive, unless the worms had another reason for the development of the neuronal capacity to develop these complex patterns then they wouldn’t have the neuronal capacity in the first place and no amount of genetic drift could generate these behaviours.

Second, the behaviours are temporally distinct, that is, each level of complexity is isolated from the others in time, only simple behaviours at the start, semi-complex behaviours in the middle and complex behaviours at the end (Or at least at the present, who knows what will happen in the future of such animals). This would suggest a directionality to the behaviour, if it were mere chance that developed these patterns then it would be a reasonable assumption that all behaviours would be represented at almost the entire length of their history. The fact that this is not the case would suggest that the complex behaviours are more selective.

So to conclude, these behaviours have gotten more complex over time, and it is highly likely that this is not the result of genetic drift, rather an evolutionary response to an environmental or ecological pressure which forced the development of such behaviours.

Comments and criticisms welcome.