This first slide really is just an update on the content of my

lecture last time, and it actually has two

messages; there's the direct message and

then there's the meta-message.

Andrea interpreted my lecture last time as me making the claim

that parents usually don't intervene in fights between

their offspring.

And so she had this nice paper that she'd read on hyenas that

showed that actually mother hyenas do intervene in the

squabbles between the baby hyenas,

and that they do so probably because in some seasons they're

actually able to get enough food--

if there are twins born, say that are sisters,

that are fighting with each other in the first week of

life-- to actually rear both of them.

And that's an important qualification.

So I want you all to know about it.

But the meta-message is this.

I really appreciate being informed about things like this.

I have to cover an incredibly broad range of biology in this

course, and I can't read all of the latest literature in all of

it.

And so if any of you feel moved, by the work that you have

done on your papers, to increase my knowledge by

sending in a little qualifier on one of my lectures,

I would be delighted to receive it;

then my lectures next time around will be a little bit more

current.

So.

Student: Can you check your microphone?

Is it on or off?

Prof: Open to all kinds of criticism.

>

Okay, today we're going to talk about alternative breeding

strategies.

And I asked Alex actually to come up with one of his

incredibly neat videos today, and he had trouble on YouTube,

and other places, finding a really neat video of

alternative breeding strategies, in males.

You'll see some slides.

They are dramatic, and they really are all focused

around one basic idea, and I just want to show-

indicate that at the beginning.

And it's actually in the simplest example,

in the bullfrog example.

Okay?

And the whole issue of having an alternative breeding strategy

revolves around frequency dependence.

So the usual scenario is that at some point in the

evolutionary past a male has achieved a dominant mating

status, and that sexual selection has

then driven the evolution of his behavior and his morphology--

the mating system, polygeny, polyandry,

whatever; in which case it would be a

female who would achieve the dominant mating status--

so that there was a focal pair, and that that biology got

pushed to a certain degree.

But once it evolved, it created the opportunity for

alternatives.

And so that's the theme of the whole lecture;

okay, it's alternative ways of getting a mating.

And as you'll see there are quite a few issues that are

interesting, and it covers a pretty broad range of different

kinds of organisms.

So this is the paradigmatic example.

And this often happens in various kinds of frogs,

not just bullfrogs, that the male calls,

the female hears the male calling, moves toward the pond,

and the male will then grasp the female with incredibly

strong forearms.

And if any of you are interested in frogs,

or had one in your pocket, you may have noticed that males

have different forearms than females.

They really have Popeye the Sailorman, bulked up,

steroid forearms, and once they get onto a female

it's actually extremely hard to pry them off.

You might be two hundred times their weight,

but boy they are hard to get off, and that's because that's

where all of their reproductive success is.

If they can stay locked onto her when she releases her eggs,

they will get the babies.

Of course what then happens is that a small male will jump on,

on top of the large male.

If a small male gets onto the female first,

the large male will grab both of them and practically squeeze

the small male to death.

Now the point of this is that the behavior of the dominant

male, and the female who's attracted

to him, created the opportunity for the

alternative behavior of the small male.

If that hadn't already been there, the alterative wouldn't

exist.

In the spring in the meadow that was behind our house in

Switzerland, when the male frogs started

calling in the pond in our neighbor's garden,

and the females started coming down through the meadow,

the male frogs that were waiting for the females to move

by would jump onto them, and then the females would have

to carry those guys on their backs,

around 100 meters, to get to the pond;

during which time, you know, other frogs would be

trying to jump on.

So it's a very--part of the intensity of this is driven by

the ephemerality of the pond.

If it weren't the case that the pond was only going to be there

for a little while, and only really suitable for

raising baby frogs for a little while,

it wouldn't be so intense.

But that's the case, and it is incredibly intense.

It all happens in a period of about twenty-four to forty-eight

hours.

Now a similar kind of alternative--well similar in the

abstract sense; a similar alternative mating

strategy has evolved in figs and fig wasps.

And figs and fig wasps are one of the wonders of ecology and

evolution.

There are--I don't want to be precise because in fact I don't

think we really know.

But let's say there are more than 500 species of figs in the

world--many of them in tropical rainforests;

many of them critical ecological resources providing

food throughout seasons when other trees are not providing

food-- and each one of these species

of figs, in general, has its own fig

wasp, and if it didn't have that fig wasp,

it couldn't get pollinated.

So what's going on here is that the figs are sacrificing some of

their own seeds to raise the wasps that pollinate them.

And this clearly has evolved from an ancestral situation in

which the wasps were actually parasitizing the figs,

and ripping them off, but now has evolved into a

mutualistic and very complicated mutualistic relationship.

The strategies of both the figs and the wasps vary.

You'll see in a minute that sometimes the figs are

monoecious, sometimes they're diecious;

in other words, sometimes they are producing

fruits that only have male flowers or only have female

flowers, and sometimes they're producing

fruits that have both kinds of flowers in the same fruit.

And the wasps have really highly differentiated strategies

that depend on whether they're copulating inside the fig,

outside the fig, and so forth,

and sometimes you get both kinds of strategies in the same

species of wasp.

So here's a fig, and here are some of the wasps

that would be living on it.

And this is about how big they are.

Okay?

So they're pretty small.

And in fact if you've gone to a nice organic store,

and you have eaten figs from a nice organic store,

there is a certain probability that you've increased your

protein intake, and you probably haven't even

noticed.

Now, the figs can make either long or short styled flowers.

And what that means is that they are making flowers which

are going to be targeted by fig wasps, or not targeted by fig

wasps, for their babies.

And if we--if you work through this diagram,

you'll see that the figs that have long styled flowers are

going to be getting pollinated, and there aren't going to be

any larvae developing on them.

These are the ones that are going to make new figs.

Okay?

And the figs that make short styled flowers are going to be

chosen--in this species of fig; this isn't for all,

but this is for one of the 600 species of figs--

they will be chosen by the wasp that will oviposit in them,

and the wasps will eclose.

They will mate; in many cases they will mate

inside the fig, and then when the females leave

the fig, the timing of the fig's flower

maturation is such that as the females force their way out of a

narrow aperture, there are flowers bearing

pollen right next to that aperture on the inside,

and the female takes them out, and then she flies off to

oviposit in another fig, which is how the pollination is

achieved.

So they had to set up two separate ways of making seeds;

the ones that the wasps would use and the ones that would make

future figs.

Other fig species have partitioned this in other ways.

Okay?

So there's an interesting complexity of evolution that's

gone on in this relationship.

Now the alternative mating strategies are that there will

be fighting males or dispersing males.

You don't need to pay too much attention to this;

this just shows that the more winged males there are,

the more females get mated by a winged male, that's all.

But there is a frequency dependent thing going on inside

one of those figs, as the males are hatching out.

If they fight with each other and kill each other,

then the survivor will be the only male who is in that fig,

or one of the few males in that fig,

who can mate with the females that are coming out.

So there is--you know, if you commit to that strategy,

you are committing to an extremely aggressive,

live by the sword die by the sword,

kind of existence, and it all gets carried out in

a dark little fig, and you're just waiting for the

first female to hatch out so that you can mate with her,

and you get as many as you can, and then you never fly,

because you don't have any wings.

You die in the fig.

So that's your protein intake; it's dead males.

On the other hand a certain number of the females are going

to manage to get out of the fig without being mated inside,

and if you can go out and find them,

outside, then you don't have to commit to fighting.

However, there are very strong morphological tradeoffs between

the two kinds of things.

You can't do both well; so you're committing to doing

one or the other well.

And how much each pays depends on the local biology.

How likely is it that the female will be able to get out

of a seed, an eclose, and get her wings

ready to go, and get out of there before one

of these fighting males comes over and gets her?

So that's what creates the frequency dependence.

And you can see these things are radically morphologically

different from one another.

This is a case in which the alternative reproductive tactics

are really resulting in changes that you could just pick up by

looking at the things.

You might need a hand glass to see it very clearly,

because these guys are down about one millimeter long.

But it has resulted in major morphological change.

And, by the way, these, from an evo-devo

perspective, this is neat because all of these forms are

elicited essentially from the same genotype.

These guys are haploid; these are the males.

This is the female; she's diploid.

Otherwise they have the same genotype,

and these alternatives here are probably being determined just

by one autosomal locus with two alleles,

that are determining whether or not you are a type that flies

out of the nest or stays in the nest and fights.

And you can see that the female is equipped with really a

beautiful, exquisitely long ovipositor to get her egg into

the fig seed.

Okay.

So we've seen that bullfrogs and fig wasps--the bullfrog

biology is relatively straightforward;

the fig wasp biology is almost arbitrarily complex.

But they both create situations in which alternative male mating

tactics are possible.

And the thing that drives that is that there is a very well

developed, evolved, prior biology,

that means an alternative has an opportunity to insinuate