# Why sexual maturity at different times for sexes?



## cloud jaguar (Oct 22, 2008)

It seems like many types of mantids have females and males that reach sexual maturity at very different times, even reducing breeding success. I am wondering, why on earth would they evolve like this? It seems odd that nature would select this as a survival mechanism, yet mantids have been around for millions of years. I guess what I am saying is, say for example orchids, in nature i assume it is just more likely that one super male will outlive all his competitors and mate like crazy or what? Can anyone shed some light on this for me?

.


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## sidewinder (Oct 22, 2008)

Arkanis,

The first thing you need to do is remember that what you see with captive mantids is not necessarily representative of what happens in nature.

Keep in mind that the vast majority of mantid species are tropical and do not have to complete their life cycle in single growing season. Oothecae for tropical species likely hatch every day which means that overlapping generations are normal. Because of this, having the sexes mature at different rates is not a problem. In fact, there may some potential benefit to this.

Since most temperate species have to complete their life cycle in single growing season, it would be fatal for the species to have the sexes become sexually mature at significantly different times. The oothecae of temperate species in the same area hatch at about the same time. I think you will find that, in nature, the adults of temperate species become sexually mature in the appropriate time frame leaving themselves plenty of time to mate and lay oothecae.

Scott


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## kamakiri (Oct 22, 2008)

I was thinking that in the wild, the males would eat proportionately less than the females due to their smaller size at later instars. Average molt intervals could remain the same that way. Even non-tropical species in captivity seem to have males develop faster.


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## matt020593 (Oct 26, 2008)

I think it's a way to avoid interbreeding. If the males and females mature at different times then you dont get the same family mating with eachother.

Maybe somebody can confirm or correct that?


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## sidewinder (Oct 26, 2008)

Matthew Whittle said:


> I think it's a way to avoid interbreeding. If the males and females mature at different times then you dont get the same family mating with eachother.Maybe somebody can confirm or correct that?


Matthew Whittle,

For tropical species, that is one of the "potential benefits" I alluded to in my post above. But with _Tenodera sinensis_ (Chinese mantis) at least, I don't see how that would work out. According to page 45 of _The Praying Mantids_, oothecae of the species all hatch within two weeks of each other. I would expect similar synchronicity among other temperate species.

Scott


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## Orin (Oct 29, 2008)

Arkanis said:


> It seems like many types of mantids have females and males that reach sexual maturity at very different times, even reducing breeding success.


Males mature faster because the second male to find the female finds a less receptive, fertilized female.


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## sidewinder (Oct 29, 2008)

Orin said:


> Males mature faster because the second male to find the female finds a less receptive, fertilized female.


What happens captivity is not necessarily representative of what happens in nature. In nature, because of wide dispersion of individuals, males just don't stumble upon female mantids.

The primary reason male mantids find female mantids is due to pheromone emission. From the research I have read, it would appear that, in most species, the female starts emitting pheromones when she is sexually mature and stops emitting pheromones when she has successfully mated. She will resume emitting pheromones after laying one or more oothecae (_The Praying Mantids_, page 72).

In other words, the female will "call" males when she is receptive to mating. If she is not receptive, she will not call. Males that come across females that are not calling do find less receptive females and suffer a higher risk of becoming a meal.

Again, within a species, males reaching adulthood sooner than females is not an issue with tropical species. In temperate species, as long as the males are available to mate throughout the time females are sexually mature and capable of laying oothecae, it matters not that they mature sooner or even significantly sooner.

Scott


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## kakistos (Oct 29, 2008)

I see you know your biology Scott!

I also think that the behavoir and development we observe in our own captive mantids can not be reliable to predict behavoir/development in the wild.

There is a point in maturing early for males as made by Orin, because males that are too late have less chances mating, because the females might already have mated. But I cannot believe the differences in maturing are ever as large as in captive Hymenopus.

Inbreeding is avoided in all species. why have sex if you do it with your sisters? Then it's easier to become parthenogenic.


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## sidewinder (Oct 29, 2008)

kakistos,

I suppose the best reason for male mantids in a temperate species maturing first is that it would never be good to have sexually mature females present in the population with few to no sexually mature males. Those females need to mate as soon as possible to get those oothecae laid before something happens to them.

Scott


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## kakistos (Oct 30, 2008)

salomonis said:


> kakistos,I suppose the best reason for male mantids in a temperate species maturing first is that it would never be good to have sexually mature females present in the population with few to no sexually mature males. Those females need to mate as soon as possible to get those oothecae laid before something happens to them.
> 
> Scott


Yeah that could also be true, but you should not think of it in a way of "good for the species" but more to "good for the males". Because if an individual could do something that is benefical to the individual but harmful to the population/species, he/she would still do it in evolution. There is not way to regulate population benefit, only benefit to the individual: more benefit means more offspring, means more genes passed on.

If the females want to mate asap, then the males would still not do that just because the females want it. But if the males that do mature sooner find more unmated females, then their genes spread more... so next year more males (the offspring of the first males) will mature sooner.


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## sidewinder (Oct 30, 2008)

kakistos said:


> Yeah that could also be true, but you should not think of it in a way of "good for the species" but more to "good for the males". Because if an individual could do something that is benefical to the individual but harmful to the population/species, he/she would still do it in evolution. There is not way to regulate population benefit, only benefit to the individual: more benefit means more offspring, means more genes passed on.If the females want to mate asap, then the males would still not do that just because the females want it. But if the males that do mature sooner find more unmated females, then their genes spread more... so next year more males (the offspring of the first males) will mature sooner.


kakistos,

Of course you are right. Males evolve to do what is best for them, not the population. Selfish, aren't they?  

Scott


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## Katnapper (Oct 30, 2008)

salomonis said:


> kakistos,Of course you are right. Males evolve to do what is best for them, not the population. Selfish, aren't they?
> 
> Scott


And you wonder why females are sometimes inclined to cannibalize them while mating...  (Couldn't resist)


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## PhilinYuma (Oct 30, 2008)

salomonis said:


> kakistos,Of course you are right. Males evolve to do what is best for them, not the population. Selfish, aren't they?
> 
> Scott


Salamonis, Kakistos:

You're both putting us on, right? I sometimes coach my 14 yr old, sophomore granddaughter, Sunny, in her honors (!) biology, and showed her this. She is sure that you are both joking and slyly referring to Dawkins' _The Selfish Gene_. Those theoretical, self centered mantids that won't mate "just because the female want them to," will not pass on their genes (is willful independence a dominant or recessive gene? recessive, I should think) so every year fewer and fewer male offspring will be willfully independent, and those with a good sexual work ethic will eventually win out.

Still, these spats are great fun to read, especially when not constrained by facts. Sunny is a bright but intellectually lazy child, and perhaps I can use your discussion to ease her into actually reading Dawkins' book

I am about to put some boring, factual stuff about male/female emergence into the thread about S. limbata. It may be familiar to you old hands, but it was new to me.


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## kamakiri (Oct 30, 2008)

Matthew Whittle said:


> I think it's a way to avoid interbreeding. If the males and females mature at different times then you dont get the same family mating with eachother.Maybe somebody can confirm or correct that?


Okay let me try this again a different way  

I doubt this is a way to avoid inbreeding. I believe that highly specialized insects like mantids rely on inbreeding to evolve and adapt.

I doubt that in nature development times vary by much. In small, relatively isolated mantid populations in temperate areas, this would spell extinction a species.


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## kakistos (Oct 30, 2008)

PhilinYuma said:


> Salamonis, Kakistos:You're both putting us on, right? I sometimes coach my 14 yr old, sophomore granddaughter, Sunny, in her honors (!) biology, and showed her this. She is sure that you are both joking and slyly referring to Dawkins' _The Selfish Gene_. Those theoretical, self centered mantids that won't mate "just because the female want them to," will not pass on their genes (is willful independence a dominant or recessive gene? recessive, I should think) so every year fewer and fewer male offspring will be willfully independent, and those with a good sexual work ethic will eventually win out.
> 
> Still, these spats are great fun to read, especially when not constrained by facts. Sunny is a bright but intellectually lazy child, and perhaps I can use your discussion to ease her into actually reading Dawkins' book
> 
> I am about to put some boring, factual stuff about male/female emergence into the thread about S. limbata. It may be familiar to you old hands, but it was new to me.


No I'm not joking, but I think you misinterpreted what I said.

Someone was saying that males mature sooner because the females might die before mating if the males do not mature. I said it should not be viewed from the population point of view ("females mantids go to waste") but from the male view. Earlier maturing males will find more receptive females, so they will have the advantage. So they get more offspring and the next year more early males arise... untill it no longer has an advantage to be even sooner mature.

You completely misunderstood me if you thought that I said that the males have a 'will' and are 'stubborn' in self deciding when to mate. That is just stupid, like you said.


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## sidewinder (Oct 30, 2008)

PhilinYuma,

There is no willfulness involved. Let me provide an example of what kakistos was talking about:

Let's say we have a mantid species, _Gilliganus skipperus_, on an isolated island in a temperate zone of the Pacific ocean. Let's also say that _G. skipperus_ goes through an obligate diapause that is broken by the colder winter season and only lay one ootheca per season. Let's say that _G. skipperus_ oothecae exhibit strong synchronicity and all hatch within a week of each other. Finally, in _G. skipperus_, the males become sexually mature one to two weeks after the females.

The _G. skipperus_ males that become sexually mature soonest have the best chance to pass on their DNA. The next season more males will mature sooner. Then the same thing happens the next season. And so on and so on until maturing sooner than other males in the species is not an advantage. This what natural selection is all about.

This natural selection process had nothing to do with what was good for the population (species). It was just good for the males because their goal is to pass on their DNA.

Scott


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## PhilinYuma (Oct 30, 2008)

salomonis said:


> PhilinYuma,This natural selection process had nothing to do with what was good for the population (species). It was just good for the males because their goal is to pass on their DNA.
> 
> Scott


Kakistos, Salomonis:

O.K. gentlemen, I completely believe that you wre not joking, though Sunny will be very disappointed that "selfish" was not a punning reference to Dawkin's book. There are two issues here, though, that I would like to glance at.

According to your model of Gilliganus skiperus (now extinct I undersatand, due to global warming), the maturation delay would appear to be only of a temporary nature. Both your model and the Stagmomantis limbata data that I quote elsewhere, concur with Bobbyd's suggestion that, " in nature, the adults of temperate species become sexually mature in the appropriate time frame leaving themselves plenty of time to mate and lay oothecae."

I certainly agree with everything that you say in your last post, Salomonis, up until your last paragraph, indeed, I cannot think of anyone who would argue with it, but your last claim, that it is the males' _goal_ to pass on their DNA, undercuts, in my judgment, what has gone before. I know that such personification is frequently used unwittingly by scientists -- I think that someone has even put a collection of examples on a website -- but it undercuts one of the basic tenets of evolutionary theory. Of course the mantis isn't trying to advance his species, but equally, he isn't trying to pass on his DNA. He doesn't think, so he isn't "willful" but neither does he have goals. He follows his instincts, he obeys the pheromones to which he is exposed, and that is it.

I'm not sure whay, Kakistos, why you mentioned that, "Because if an individual could do something that is benefical to the individual but harmful to the population/species, he/she would still do it in evolution." Again, I can't think of anyone who would disagree. E.O. Wilson's theory of "altruistic behavior" (_Sociobiology_) with its suggestion that stotting Thompson's gazelles do so in order to warn their comrades while endangering themselves, is pretty much old hat., especially among those who have actually observed the behavior.

GSH! We all seem to be pretty much in agreement, and i shall conclude by uploading a pic of Sunny exopressing her opinion of "intelligent design". Shoot, how do you attach a pic? I got the file in the browser window, then...nothing.


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## sidewinder (Oct 30, 2008)

PhilinYuma,

You are anthropomorphizing my words. When I say "their goal", I am not saying it is their conscious thought to do this. It is their goal by instinct. What are the three primary instincts of most animals? Eat, survive, and reproduce....

Scott


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