Although large evolutionary radiations producing many species have captured the attention of biologists, comparison of the sizes of evolutionary lineages show that unusually small groups with few species are more frequent than one would expect from a model of random speciation and extinction.
Among songbirds (Passeriformes), more than 30 of 106 tribe-level taxonomic groups have five or fewer species, compared to the average size of 54 species and a maximum of more than 10 times that number. The existence of so many small taxa suggests that these lineages must have unusually low rates of speciation and extinction compared to other songbirds. In an earlier analysis, Robert E. Ricklefs suggested that species in these small groups might avoid extinction by competitive exclusion because they are marginal both geographically and ecologically. In this new study, which will appear in the June 2005 issue of The American Naturalist, Ricklefs shows that species in small clades tend to have extreme morphology, in particular relatively long toes, sometimes in contrast with short legs, and small beaks. Such traits are associated with foraging on bark or rock surfaces or feeding from perched positions or in dense, shrubby vegetation. These are unusual habits for typically more active songbirds. How such marginal ecology slows the rates of species formation and extinction remains an open question.
Carrie Olivia Adams | EurekAlert!
Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University
Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017
25.04.2017 | Laser Zentrum Hannover e.V.
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
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25.04.2017 | Life Sciences