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Dr. Richard TwitchettDownsizing 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?