News: We're off then: The evolution of bat migration
Ye Old One
November 20, 2009
http://www.physorg.com/news177948336.html
(PhysOrg.com) -- Not just birds, but also a few species of bats face a
long journey every year. Researchers at Princeton University in the
U.S. and at the Max Planck Institute for Ornithology in Radolfzell,
Germany studied the migratory behaviour of the largest extant family
of bats, the so-called "Vespertilionidae" with the help of
mathematical models. They discovered that the migration over short as
well as long distances of various kinds of bats evolved independently
within the family.
Most people know the term of "migrating bird" but "migrating bat" is
not well established. However, some bat species migrate every year
long or short distances. Whereas birds migrate to exploit seasonal
food resources, the majority of bats migrate with the intention to
find better hibernating conditions.
In Europe about 30 percent and in North America around 45 percent of
bird species migrate; the migration of bats however is a rather rare
phenomenon. Only about three percent of the approximately 1,000 bat
species migrate, of those less than 0.016 percent migrate further than
1,000 kilometres. The vast majority of bats living in temperate zones
hibernate during the winter as a result of food shortage at this time.
Together, researchers of the University of Princeton in the U.S. and
the Max Planck Institute for Ornithology analyzed the genealogical
tree of bats on the basis of their migratory behaviour. They are
confining themselves to only the family of the "Vespertilionidae",
also called the vespertilionid bats, which includes 316 species or
about a third of all bat species. Of about 32 migrating bat species,
23 are part of this family. Eleven of those migrate over long
distances greater than 1,000 kilometres. The remaining twelve species
only fly short distances that vary between 100 to 1,000 kilometres.
The researchers discovered that the migratory behaviour over long and
short distances evolved repeatedly and for the most part independently
within the family of vespertilionid bats. Kamran Safi, one of the
authors of the study says: "according to the model, the probability
for the vespertilionid bats to loose or gain their residential habitat
is the same as becoming a short or long distance migrant". The
migratory behaviour of bats could be more complex than previously
assumed. The evolution as well as the loss of the migratory behaviour
is probably based on the fast evolutionary adaptation that is caused
by climate change or changes in the social life of the bat.
The scientist of the Max Planck Institute says: "We assume that the
evolution of migratory behaviour in the vespertilionid bats is an
answer to sinking temperatures in their habitats, which made a
temporary migration into warmer areas necessary". In contrast, for the
migratory behaviour of birds it is generally hypothesized that
tropical species expand to different areas. The evolution of migratory
behaviour in bats enabled access to new resources and as a result, the
density of the bats increased rapidly.
Most of the verspertilionidae were originally from the temperate zone
and not from the tropics. In addition, researchers discovered that
there is a correlation between migration and roost use as well as
between migration and geographic distribution. Furthermore tree
roosting bats are more likely to migrate than cave roosting species. A
possible reason for this behaviour is the difficulty for bats to find
suitable hibernating conditions in trees.
Original work:
More information: Isabelle-Anne Bisson, Kamran Safi, Richard A.
Holland, Evidence for Repeated Independent Evolution of Migration in
the Largest Family of Bats. PLoS ONE 4(10): e7504. October 21st, 2009.
doi:10.1371/journal.pone.0007504
--
Bob.