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The Lilliput effect and mass extinction events |
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 Downsizing in adversity: the Lilliput effect and mass extinction events
Dr. Richard Twitchett spricht über Massenaussterben und die Erholung von Massenaussterben in der Erdgeschichte (Vortrag in englischer Sprache)
Donnerstag, 23. April 2009, 18:15, Hörsaal 7, Pharmaziezentrum, Althanstraße 14, 1090 Wien
The history of life on Earth has been punctuated by 5 or 6 major mass
extinction episodes, and a host of regional and smaller-scale events.
These extinction episodes have shaped the evolution of the biosphere
and understanding their causes and consequences is a topic that engages
many evolutionary biologists, geologists and palaeontologists. The
Lilliput effect - a term which was first coined by Adam Urbanek in 1993
following his studies of Silurian graptolites - is however one aspect
that has hitherto been largely overlooked. The term “Lilliput effect”
describes the pattern of size change through extinction events: in the
immediate aftermath of such events organisms are typically much smaller
than during pre-extinction times. Body size is a key morphological
variable, with implications for many aspects of an animal’s biology,
behaviour and ecology and can be measured from fossil remains.
Understanding the Lilliput effect may therefore be crucial in
understanding the nature of ecological, environmental and biological
change during past biotic crises, especially during the immediate
post-event aftermath. The phenomenon is clearly widespread: a decrease
in the body size of post-extinction survivors is recorded in the
aftermath of all the major Phanerozoic extinction episodes, and has
been documented in a variety of animal groups, such as Early Silurian
corals, Late Devonian conodonts, Early Triassic gastropods and Early
Danian echinoids and foraminifera, as well as terrestrial vertebrates.
Despite the common occurrence of the Lilliput effect, there are still a
number of outstanding questions that need to be addressed, such as the
cause(s) of size reduction and its biological mechanism. Size changes
in the marine realm seem to relate to changes in temperature,
productivity and expansion of the oxygen minimum zone, all of which are
likely to occur in the near-future. Are we heading for a new Lilliput
world?
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