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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

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
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Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
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Brian Reply
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Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
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LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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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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