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Kadal Menjalani  Evolution yang cepat  Setelah dikenalkan pada  Sebuah tempat  Baru

Pada tahun 1971 , ahli biologi memindahkan  lima pasang  kadal dinding Italia dewasa  dari pulau asal mereka Pod Kopiste , di Selatan Laut Adriatik , ke pulau tetangga Pod Mrcaru . Sekarang peneliti telah memperlihatkan  bahwa sedikit perkenalan  , green backed lizards , Podarcis sicula , dengan lingkungan baru menyebabkan mereka mengalami perubahan evolusioner skala besar yang cepat ...more

Lizards Undergo Rapid Evolution After
Introduction To A New Home

Date:

April 18, 2008

Source:

University Of Massachusetts, Amherst

Summary:

In 1971, biologists moved five adult pairs of Italian wall lizards from
their home island of Pod Kopiste, in the South Adriatic Sea, to the neighboring
island of Pod Mrcaru. Now researchers have shown that introducing these small,
green-backed lizards, Podarcis sicula, to a new environment caused them to
undergo rapid and large-scale evolutionary changes.

......................

In 1971, biologists moved five adult pairs of Italian wall lizards from
their home island of Pod Kopiste, in the South Adriatic Sea, to the neighboring
island of Pod Mrcaru. Now, an international team of researchers has shown that
introducing these small, green-backed lizards, Podarcis sicula, to a new
environment caused them to undergo rapid and large-scale evolutionary changes.

“Striking differences in head size and shape, increased bite strength and
the development of new structures in the lizard’s digestive tracts were noted
after only 36 years, which is an extremely short time scale,” says Duncan
Irschick, a professor of biology at the University of Massachusetts Amherst.
“These physical changes have occurred side-by-side with dramatic changes in
population density and social structure.”

Researchers returned to the islands twice a year for three years, in the
spring and summer of 2004, 2005 and 2006. Captured lizards were transported to
a field laboratory and measured for snout-vent length, head dimensions and body
mass. Tail clips taken for DNA analysis confirmed that the Pod Mrcaru lizards
were genetically identical to the source population on Pod Kopiste.

Observed changes in head morphology were caused by adaptation to a
different food source. According to Irschick, lizards on the barren island of
Pod Kopiste were well-suited to catching mobile prey, feasting mainly on
insects. Life on Pod Mrcaru, where they had never lived before, offered them an
abundant supply of plant foods, including the leaves and stems from native
shrubs. Analysis of the stomach contents of lizards on Pod Mrcaru showed that
their diet included up to two-thirds plants, depending on the season, a large
increase over the population of Pod Kopiste.

“As a result, individuals on Pod Mrcaru have heads that are longer, wider
and taller than those on Pod Kopiste, which translates into a big increase in
bite force,” says Irschick. “Because plants are tough and fibrous, high bite
forces allow the lizards to crop smaller pieces from plants, which can help
them break down the indigestible cell walls.”

Examination of the lizard’s digestive tracts revealed something even more
surprising. Eating more plants caused the development of new structures called
cecal valves, designed to slow the passage of food by creating fermentation
chambers in the gut, where microbes can break down the difficult to digest
portion of plants. Cecal valves, which were found in hatchlings, juveniles and
adults on Pod Mrcaru, have never been reported for this species, including the
source population on Pod Kopiste.

“These structures actually occur in less than 1 percent of all known
species of scaled reptiles,” says Irschick. “Our data shows that evolution of
novel structures can occur on extremely short time scales. Cecal valve
evolution probably went hand-in-hand with a novel association between the
lizards on Pod Mrcaru and microorganisms called nematodes that break down
cellulose, which were found in their hindguts.”

Change in diet also affected the population density and social structure of
the Pod Mrcaru population. Because plants provide a larger and more predictable
food supply, there were more lizards in a given area on Pod Mrcaru. Food was
obtained through browsing rather than the active pursuit of prey, and the
lizards had given up defending territories.

“What is unique about this finding is that rapid evolution can affect not
only the structure and function of a species, but also influence behavioral
ecology and natural history,” says Irschick.

Results of the study were published March 25 in Proceedings of the National
Academy of Sciences. This research was supported by the National Science
Foundation and the Fund for Scientific Research in Flanders. Additional members
of the research team include Anthony Herrel of Harvard University and the
University of Antwerp, Kathleen Huyghe, Bieke Vanhooydonck, Thierry Backeljau
and Raoul Van Damme of the University of Antwerp, Karin Breugelmans of the
Royal Belgian Institute of Natural Sciences and Irena Grbac of the Croatian
Natural History Museum.







Story Source:

The above story is based on materials provided
by University Of Massachusetts, Amherst. Note:
Materials may be edited for content and length.

http://www.sciencedaily.com/releases/2008/04/080417112433.htm

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