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Gould’s spandrel: a non-adaptionist hypothesis

Though experimental results appear to support a sexual selection hypothesis, some researchers present an alternate interpretation. Female spiders may consume smaller males because, quite simply, it is easier to do so (Wilder and Rypstra 2008). Though tiny males may not be nutritionally substantive, it is possible that female predatory behavior is ingrained and non-discriminatory (a female is willing to catch any prey around). In size dimorphic species, sexual cannibalism may have arisen incidentally from the condition of sexes’ size divergence.

The non-adaptionist hypothesis is composed of a simple argument:

  1. High levels of size dimorphism is an attribute of typical predator-prey interactions. Sexually cannibalistic spider species often display high sexual size dimorphism (Wilder and Rypstra 2008)
  2. There is no feasible explanation for how sexual cannibalism could have selected for high sexual size dimorphism. If females consistently selected against smaller males, there would be lower dimorphism than spider species exhibit. Instead, sexual size dimorphism must have evolved first, driven by external factors. Fecundity selection favored greater female size because massive females could produce bigger ootheca, and more surviving offspring. Conversely, scramble competition promoted smaller size among males.
  3. Since size dimorphism is conducive to predator-prey interaction (see premise 1), sexual cannibalism emerged subsequently (Wilder and Rypstra 2008).

Thus, the non-adaptionist hypothesis argues that the phylogenic distribution of sexual cannibalism in some spiders is a by-product of selection for sexual size dimorphism in other contexts. Stephen J. Gould terms such incidental cross-trait associations “spandrels,” after an architectural term for the space between two arches (Gould 1997). In a spandrel , a behavior may not be beneficial at all, but inevitably arises out of external survival pressures.

A corollary to the “spandrel” explanation is another, “spillover” hypothesis. According to some researchers, sexual cannibalism is a consequence of generalized female aggressive behavior. The trait of female rapacity is favorable for juveniles, promoting their survival in a stage that demands high food consumption. Rapacity is less important after females attain maximum size and sexual maturity, but the aggressive trait cannot be extricated by that point (even if it drives away a fecund female’s potential mates). Thus, sexual cannibalism is non-adaptive, but sustained because rapacity helps juveniles survive (Arnqvist and Henriksson 1997).

Discussion question:

Given the analysis regarding how sexual cannibalism could be adaptive, how are these non-adaptive theories and to what extent are they contradictory? Which do you think is more likely?

Conclusions and future directions

Several well-developed hypotheses arise to explain the peculiar and dramatic behavior of sexual cannibalism. Models based on fitness economics, sexual selection, and non-adaptive “spandrels” or “spillovers” provide viable descriptions of cannibals’ evolution. These various hypotheses are not mutually exclusive, and may apply differently to species based on organisms’ unique morphology and environmental pressures. A common vein in several hypotheses is that sexual cannibalism is a manifestation of conflict of interest between the sexes. Intersexual conflict is succinctly expressed by cost/benefit models for males and females, in which parameters for the benefit of cannibalism contrast. This conveys the divergent nature of reproductive behaviors. Sexual cannibalism demonstrates that, even when organisms have the common goal of producing quality offspring, they interact through selfish and often antagonistic tactics.

Questions & Answers

What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Mockingbird tales: readings in animal behavior. OpenStax CNX. Jan 12, 2011 Download for free at http://cnx.org/content/col11211/1.5
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