The geometry of sex: How body size could lead to new species

Aug 26, 2011
The P. skiltonianus species group includes two size-differentiated species that are widespread in western North America. Top: An adult female P. skiltonianus from San Luis Obispo County, California Bottom: Adult male P. gilberti from Yuba County, California. The bright red head coloration indicates a male in breeding condition. (Top: © Brad Alexander Bottom: © Ackson Shedd)

Different species of scincid lizards, commonly known as skinks, rarely interbreed, but it's not for lack of trying.

According to Jonathan Richmond, a researcher with the U.S. Geological Survey, different species of skinks in western North America will often try to mate with each other when given the opportunity, but mechanical difficulties caused by differing body sizes can cause these encounters to fail.

After observing hundreds of cross-species mating attempts in the lab, Richmond and his colleagues developed a showing how size differences create reproductive barriers between skink species.

In order to align their for successful , the male must corkscrew his body around the female.

Once the sizes of the male and female diverge outside the threshold of the researchers' model, successful mating was very rare.

The model elucidates the role body size plays in splitting skinks into separate species.

For skinks, it apparently isn't behavioral preference that prevents between species. It's the mechanics of body size.

"As size diverges, the corkscrew fails," Richmond said. "In this case, it just happens that this is about the only thing necessary to get the ball rolling for speciation."


Explore further: Honey bees sting Texas man about 1,000 times

More information: Jonathan Q. Richmond, Elizabeth L. Jockusch, and Andrew M. Latimer, "Mechanical Reproductive Isolation Facilitates Parallel Speciation in Western North American Scincid Lizards." American Naturalist, September 2011.

add to favorites email to friend print save as pdf

Related Stories

Limb loss in lizards -- evidence for rapid evolution

Nov 11, 2008

Small skink lizards, Lerista, demonstrate extensive changes in body shape over geologically brief periods. Research published in the open access journal BMC Evolutionary Biology shows that several species of th ...

Lizard sex linked to climate

Oct 28, 2010

(PhysOrg.com) -- A Tasmanian lizard has evolved to give birth to more male or more female offspring depending on climatic conditions, Oxford University scientists have discovered.

Armed beetles find a mate, whatever their size

Mar 27, 2008

One species of armed beetle is proving that size doesn’t necessarily matter when it comes to finding a mate. The creature’s ‘pulling techniques’ will be revealed in the April edition of the Royal En ...

Male seahorses like big mates

Jul 07, 2009

Male seahorses have a clear agenda when it comes to selecting a mating partner: to increase their reproductive success. By being choosy and preferring large females, they are likely to have more and bigger eggs, as well as ...

Official! Size Really Does Matter...

Feb 09, 2006

Buy your female Valentine a priceless diamond ring and she will be faithful forever… but any cheap gift will lose her attention. Such comic-book logic has yet to be proven among humans, but it’s certainly the case in ...

Recommended for you

A tiny new species of frog from Brazil with a heroic name

11 hours ago

The Atlantic Forest is a hotspot of biodiversity and one of the most species richness biome of anurans (frogs, tree-frogs, and toads) in the world. However, current levels of diversity might be still underestimated. ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

epsi00
5 / 5 (1) Aug 26, 2011
so size does matter!
Deadbolt
1 / 5 (2) Aug 26, 2011
I wonder if some dog breeds could diverge due to this effect enough that they become considered different species.