Ancient Horse Mother Found

1 02 2012

A team of geneticists, paleontologists, and archaeologists have identified the ancient mother of all the horses alive today, according to a paper (link here) published in the Proceedings of the National Academy of Sciences, January 30.

The study, led by Alessandro Achilli, of the Dipartimento di Biologia Cellulare e Ambientale, at the Università di Perugia, in Perugia, Italy, determined that the common ancestral mare to all living horses trotted the earth between 130,000 and 160,000 years ago, with a date of approximately 140,000 years being most likely.  More importantly, the study also identified 18 major clusters of genes called haplogroups, that were involved in the domestication of horses.

Torroni and his colleagues examined 83 modern horse genomes from the Americas, Asia, Europe, and the Middle East.  While the generalities of horse domestication are broadly understood, the specifics of time and location are not.  This study sheds significant light on these aspects of the horse’s natural history.

The study indicates that horses were domesticated over a broad area of Eurasia with multiple incidents of domestication occurring at different times.  This differs from many other domestic animals, such as cattle and sheep, which were domesticated from a handful of animals at very specific locations and then spread through trade and capture.  At least one of these domestication events took place in Europe, with Iberia being a possible location for it.

Horses have an extended and close relationship with humans.  They have played a major role in human history.  Horses were widely used in warfare until the end of World War I, and were still used to some extent even in World War II.  In civilian use, millions of horses were engaged for transportation and to haul goods until the 1920s, when they were largely replaced by trucks and automobiles.  They were still a common sight on many American roads until the 1940s.

In addition to its general scientific interest, the paper points out that the results of the study can also be used to classify fossil horse remains, identifying where they belong on the horse family tree; better define and understand modern horse breeds and their ancestry; and evaluate the role of maternal ancestry in racehorse performance.

Bhimbetka_Rock_Paintng_Man_Riding_Horse

A 30,000 year old rock painting from Bhimbetka in north central India, showing a man riding a horse. This image comes from Wiki Commons and is used under the GNU Free Documentation License





Scientists Discover Link Between Malaria and Red Tides

1 06 2010

A team of scientists has discovered the common ancestor of two creatures that cause the world a considerable amount of trouble and suffering, the malaria parasite and the organism that causes red tides.  The missing link, the thing that connected the two, turned out to be little brown balls called Chromera.

The team, consisting of scientists from the University of British Columbia in Canada and the University of South Bohemia, in the Czech Republic, published their findings in the online early edition of the Proceedings of the National Academy of Sciences (PNAS), an American publication.

Chromera is a symbiont found inside corals. While it has a compartment (called a plastid) used to perform photosynthesis like the dinoflalgellate algae that causes red tide (as well as photosynthesis in plants), Chromera is closely related to apicomplexan parasites, which include malaria.  This discovery, first published in the journal Nature in 2008, gave researchers the idea that the algae and the parasites might be related and that the Chromera was the connection.

The scientists sequenced the genome of Chromera and were able to show for the first time, how the two are connected evolutionarily.

In recent interviews, the scientists said that they hope the knowledge gained by their research will not only advance basic scientific knowledge, but will also open the way for treatments for diseases such as malaria.

The original PNAS article is available here.





Floral Symmetry Genes and the Origin and Maintenance of Zygomorphy in a Plant-Pollinator Mutualism

5 04 2010

This article, published online March 30, in the Proceedings of the National Academy of Science (PNAS) examines floral zygomorphy in light of pollinator selection.  Following is the abstract for the article.  To read the entire article (if you have a subscription), please click on the following URL:  http://www.pnas.org/content/early/2010/04/01/0910155107.abstract?abspop=1&related-urls=yes&legid=pnas;0910155107v1.

Abstract

The evolution of floral zygomorphy is an important innovation in flowering plants and is thought to arise principally from specialization on various insect pollinators. Floral morphology of neotropical Malpighiaceae is distinctive and highly conserved, especially with regard to symmetry, and is thought to be caused by selection by its oil-bee pollinators. We sought to characterize the genetic basis of floral zygomorphy in Malpighiaceae by investigating CYCLOIDEA2-like (CYC2-like) genes, which are required for establishing symmetry in diverse core eudicots. We identified two copies of CYC2-like genes in Malpighiaceae, which resulted from a gene duplication in the common ancestor of the family. A likely role for these loci in the development of floral zygomorphy in Malpighiaceae is demonstrated by the conserved pattern of dorsal gene expression in two distantly related neotropical species, Byrsonima crassifolia and Janusia guaranitica. Further evidence for this function is observed in a Malpighiaceae species that has moved to the paleotropics and experienced coincident shifts in pollinators, floral symmetry, and CYC2-like gene expression. The dorsal expression pattern observed in Malpighiaceae contrasts dramatically with their actinomorphic-flowered relatives, Centroplacaceae (Bhesa paniculata) and Elatinaceae (Bergia texana). In particular, B. texana exhibits a previously undescribed pattern of uniform CYC2 expression, suggesting that CYC2 expression among the actinomorphic ancestors of zygomorphic lineages may be much more complex than previously thought. We consider three evolutionary models that may have given rise to this patterning, including the hypothesis that floral zygomorphy in Malpighiaceae arose earlier than standard morphology-based character reconstructions suggest.





PNAS Paper Suggests Predation was Responsible for Crinoid Diversification during Mesozoic

16 03 2010
Agaricocrinus splandens

Agaricocrinus splandens, a crinoid from the Mississippian Period

A paper published Monday, Mar. 15, in the online early edition of the Proceedings of the National Academies of Sciences (PNAS), draws a connection between evidence of early predation and the adaptive radiation experienced by crinoids during the early Mesozoic.  The multi-author paper points to changes in the group following their near-extinction during the end-Permian mass extinction.  This contrasts with the “major evolutionary radiation [the group underwent] during the Middle–Late Triassic that produced distinct morphological and behavioral novelties, particularly motile taxa that contrasted strongly with the predominantly sessile Paleozoic crinoid faunas.”  The authors suggest “that the appearance and subsequent evolutionary success of motile crinoids were related to benthic predation by post-Paleozoic echinoids with their stronger and more active feeding apparatus and that, in the case of crinoids, the predation-driven Mesozoic marine revolution started earlier than in other groups, perhaps soon after the end-Permian extinction.”

For the abstract and complete article, please see the following link:
http://www.pnas.org/content/early/recent.





Study Suggests Flowering Plants had Earlier Origin than Believed

16 03 2010

A study, published today (Mar. 16) in the online early edition of the Proceedings of the National Academy of Sciences (PNAS), analyzed molecular dating material collected from land plants, including 33 fossil calibrations, to reach its conclusion.  That conclusions is that the origin of crown-clade angiosperms took place during the late Triassic period, which is “considerably older than the unequivocal fossil record of flowering plants or than the molecular dates presented in recent studies”.

According to the abstract, the study permitted “rates of molecular evolution to be uncorrelated across the tree, and take into account uncertainties in phylogenetic relationships and the fossil record”.  The authors go on to state that they “attached a prior probability to each fossil-based minimum age, and explored the effects of relying on the first appearance of tricolpate pollen grains as a lower bound for the age of eudicots”.

The authors also state that “many of our divergence-time estimates for major clades coincide well with both the known fossil record and with previous estimates”.

Finally, the authors state that “although the methods used here do help to correct for lineage-specific heterogeneity in rates of molecular evolution (associated, for example, with evolutionary shifts in life history), we remain concerned that some such effects (e.g., the early radiation of herbaceous clades within angiosperms) may still be biasing our inferences”.

The study was conducted by Stephen A. Smith of the National Evolutionary Synthesis Center in Durham, NC, U.S.A., and Jeremy M. Beaulieu and Michael J. Donoghue of the Department of Ecology and Evolutionary Biology at Yale University, New Haven, CT, U.S.A.  Donoghue is also associated with the National Evolutionary Synthesis Center.

For the complete journal article see the following URL:
http://www.pnas.org/content/early/recent.