Wing size differences between two Nasonia wasp species are the result of newly discovered genetic differences between the species. The diversity of size and shape differences between other animal species may have similar origins. Credit: David Loehlin, University of Wisconsin, Madison |
From
spaghetti-like sea anemones to blobby jellyfish to filigreed oak trees,
each species in nature is characterized by a unique size and shape. But
the evolutionary changes that produce the seemingly limitless diversity
of shapes and sizes of organisms on Earth largely remains a mystery.
Nevertheless, a better understanding of how cells grow and enable
organisms to assume their characteristic sizes and shapes could shed
light on diseases that involve cell growth, including cancer and
diabetes.
Providing
new information about the evolution of the diversity of sizes and
shapes in nature is a study identifying genetic differences between two
closely related species of Nasonia wasps. These differences give males of one of the Nasonia species small flightless wings and the males of the other Nasonia species flight-worthy wings that are twice as large.
Jack
Werren and David Loehlin at the University of Rochester led the
research. (Loehlin is now a post-doc at the University of
Wisconsin-Madison). Funded by the National Science Foundation (NSF),
this week’s issue of Science covers the research.
The
research team identified the chromosomal location of the gene
responsible for wing size in each of the two Nasonia species, the
differences between the DNA sequences of these genes, as well as
regulatory controls that determine when, where and how long each
species’ growth gene is turned on.
These genetic differences alter both the locations of growth centers in the wings and the timing of growth during Nasonia
development—factors that give each species its distinct wing size. As
evidence that the identified genes control wing size, the researchers
nearly doubled the wing size of the small-winged species by
cross-breeding into it the gene from the big-winged species.
Interestingly, Loehlin says the team’s results indicate multiple genetic changes caused the differences in Nasonia wing size-changes, and these changes may have occurred incrementally.
“It
is possible that the diversity of size and shape differences between
other animal species have similar origins in regulator DNA. And the gene
we identified is thought to control growth in many other animals,
including people.”
The researchers suspect that the small winged Nasonia species evolved from the big-winged species, but it is also possible that the two species evolved in the opposite order.
“Understanding
the types of changes in DNA that are responsible for evolution is
critical to unraveling the causes of life’s diversity,” says Samuel
Scheiner, a program director at NSF. “The recent explosion of new tools
for DNA sequencing is now allowing this understanding. This study
demonstrates that changes in gene regulation can be important for such
evolution.”
The two studied species of Nasonia
wasps were chosen for this research because their close genetic
relationship coupled with the large difference in their wing sizes makes
genetic comparisons between them particularly easy. Nasonia
wasps have become a model system for studying evolution because their
genetics and breeding system simplify the identification of genetic
changes behind complex traits.
