Phylogenetic Approaches to the Study of Extinction

Phylogenetic Approaches to the Study of Extinction - Annual Review of Ecology, Evolution, and Systematics, 39(1):301 -
Abstract

Annual Review of Ecology, Evolution, and Systematics
Vol. 39: 301-319 (Volume publication date December 2008)
(doi:10.1146/annurev-ecolsys-063008-102010)
First published online as a Review in Advance on August 29, 2008

Phylogenetic Approaches to the Study of Extinction

Andy Purvis­

Division of Biology, Imperial College London, Silwood Park Campus, Ascot SL5 7PY, United Kingdom;

Species extinction is both a key process throughout the history of life and a pressing concern in the conservation of present-day biodiversity. These two facets have largely been studied by separate communities using different approaches. This article illustrates with examples some of the ways that considering the evolutionary relationships among species—phylogenies—has helped the study of both past and present species extinction. The focus is on three topics: extinction rates and severities, phylogenetic nonrandomness of extinction, and the testing of hypotheses relating extinction-proneness to attributes of organisms or species. Phylogenetic and taxic approaches to extinction have not fully fused, largely because of the difficulties of relating discrete taxa to the underlying continuity of phylogeny. Phylogeny must be considered in comparative tests of hypotheses about extinction, but care must be taken to avoid overcorrecting for phylogenetic nonindependence among taxa

Morphological Integration and Developmental Modularity

Morphological Integration and Developmental Modularity - Annual Review of Ecology, Evolution, and Systematics, 39(1):115 - Abstract

Annual Review of Ecology, Evolution, and Systematics
Vol. 39: 115-132 (Volume publication date December 2008)
(doi:10.1146/annurev.ecolsys.37.091305.110054)
First published online as a Review in Advance on August 26, 2008

Morphological Integration and Developmental Modularity

Christian Peter Klingenberg­

Faculty of Life Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom;

Biological systems, from molecular complexes to whole organisms and ecological interactions, tend to have a modular organization. Modules are sets of traits that are internally integrated by interactions among traits, but are relatively independent from other modules. The interactions within modules rely on different mechanisms, depending on the context of a study. For morphological traits, modularity occurs in developmental, genetic, functional, and evolutionary contexts. A range of methods for quantifying integration and modularity in morphological data is available, and a number of comparative and experimental designs can be used to compare the different contexts. How development produces covariation between traits can have substantial implications for understanding genetic variation and the potential for evolutionary change, but research in this area has only begun and many questions remain unanswered.

Complete mitochondrial genome of 5,000-year-old mummy yields surprise

Complete mitochondrial genome of 5,000-year-old mummy yields surprise

Researchers have revealed the complete mitochondrial genome of one of the world's most celebrated mummies, known as the Tyrolean Iceman or Ötzi. The sequence represents the oldest complete DNA sequence of modern humans' mitochondria, according to the report published online on October 30th in Current Biology, a Cell Press publication.

Mitochondria are subcellular organelles that generate all of the body's energy and house their own DNA, which is passed down from mother to child each generation. Mitochondrial DNA thus offers a window into our evolutionary past.

"Through the analysis of a complete mitochondrial genome in a particularly well-preserved human, we have obtained evidence of a significant genetic difference between present-day Europeans and a representative prehistoric human—despite the fact that the Iceman is not so old—just about 5,000 years," said Franco Rollo of the University of Camerino in Italy.

The Tyrolean Iceman witnessed the Neolithic-Copper Age transition in Central Europe more than 5,000 years ago. His mummified corpse was recovered from an Alpine glacier on the Austro-Italian border in 1991. In 2000, scientists defrosted the Iceman's body for the first time and sampled DNA from his intestines.

Earlier study of the DNA showed that he belonged to the lineage, or "subhaplogroup," known as K1. About 8% of modern Europeans belong to the K haplogroup, meaning that they share a common ancestor, and that group is divided into two "subhaplogroups," K1 and K2. The K1 haplogroup, in turn, can be divided into three clusters.

In the new study, the researchers took advantage of advanced genome-sequencing technologies to shed more light on the Iceman's genetics. They sequenced his entire mitochondrial genome and compared that sequence to other published human mitochondrial DNA sequences to construct his evolutionary (or phylogenetic) family tree.

"The surprise came when we found that the lineage of the Iceman did not fit any of the three known K1 clusters," Rollo said. His team has informally named the newly discovered branch on the human family tree "Ötzi's branch."

"This doesn't simply mean that Ötzi had some 'personal' mutations making him different from the others but that, in the past, there was a group—a branch of the phylogenetic tree—of men and women sharing the same mitochondrial DNA," Rollo said. "Apparently, this genetic group is no longer present. We don't know whether it is extinct or it has become extremely rare."

At least for the moment, he said, that means no one can claim to be "the issue of Ötzi."

Source : Cell Press