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"Density-dependent male mating harassment, female resistance and male mimicry"
Thomas P. Gosden and Erik I. Svensson


male blue-tailed damselfly matting with his doppelganger

A male mating with his female doppelganger (photo: Erik Svensson) 

Females in the blue-tailed damselfly (Ischnura elegans) occur in three different inherited color forms: green, red, and blue, with the blue form looking confusingly similar to males, perhaps to avoid repeated excessive sexual harassment. By dusting the males with a fluorescent powder, the authors monitored both the intensity of male mating harassment and the number of matings of the three female forms. The avoidance through male mimicry only seems to benefit the females when their “more attractive” sisters are at higher densities.

Press Release

Snapshot of Speciation
Study catches two bird populations as they split into seperate species

A new study finds that a change in a single gene has sent two closely related bird populations on their way to becoming two distinct species. The study, published in the August issue of The American Naturalist, is one of only a few to investigate the specific genetic changes that drive two populations toward speciation.

Parasites May Help Keep Sex On Top

What’s so great about sex? From an evolutionary perspective, the answer is not as obvious as one might think. An article published in the July issue of The American Naturalist suggests that sex may have evolved in part as a defense against parasites.

Michael J. Wade to Receive 2009 Sewall Wright Award

Harvard Biologist Jonathan Losos to Receive 2009 E. O. Wilson Naturalist Award

In the News

Featured in Scientific American
"Are Parasites To Thank for Sex?" July 8, 2009
The Maintenance of Sex, Clonal Dynamics, and Host-Parasite Coevolution in a Mixed Population of Sexual and Asexual Snails
Jukka Jokela, Mark F. Dybdahl, and Curtis M. Lively
A study in the journal The American Naturalist implies that parasites helped drive the development of sex, because the shuffling of genes gives sex-produced progeny an advantage over asexual genetic clones. Cynthia Graber reports.

Featured in ScienceNOW
"On the Road to a New Species" June 15, 2009
Difference in Plumage Color Used in Species Recognition between Incipient Species Is Linked to a Single Amino Acid Substitution in the Melanocortin‐1 Receptor
J. Albert C. Uy, Robert G. Moyle, Christopher E. Filardi, and Zachary A. Cheviron, Associate Editor: Ben C. Sheldon, Editor: Monica A. Geber
Next, the researchers evaluated whether this color change might make any difference to the birds. They put stuffed birds of either color into the territories of live flycatchers. Flycatchers are not bothered by most foreign birds, but they will attack potential rivals of the same species. Black bird decoys drew angry responses from black birds but little reaction from brown-belly birds and vice versa, Uy and his colleagues report in the August issue of The American Naturalist.

July 1979

Volume 114, Number 1
Am Nat 1979. Vol. 114, pp. 156
DOI: 10.1086/283462

Janzen's Reply

D. H. Janzen

Cited by

MICHAEL MOGIE, HENRY FORD. (1988) Sexual and asexual Taraxacum species. Biological Journal of the Linnean Society 35:2, 155-168
Online publication date: 1-Nov-1988.
CrossRef
HENRY FORD. (1981) The demography of three populations of dandelion. Biological Journal of the Linnean Society 15:1, 1-11
Online publication date: 1-Mar-1981.
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