The ‘genetics of sand’ may shed new light on evolutionary process over millions of years

This image shows a close-up of planktonic
 foraminifera. (Credit: The University of Southampton)

An evolutionary ecologist at the University of Southampton, is using ‘grains of sand’ to understand more about the process of evolution. 

Dr Thomas Ezard is using the fossils of microscopic aquatic creatures called planktonic foraminifera, often less than a millimetre in size, which can be found in all of the world’s oceans. The remains of their shells now resemble grains of sand to the naked eye and date back hundreds of millions of years.

A new paper by Dr Ezard, published today (9 August 2013) in the journal Methods in Ecology & Evolution, opens the debate on the best way to understand how new species come into existence (speciation). The debate concerns whether fossil records such as those of the planktonic foraminifera, contain useful evidence of speciation over and above the molecular study of evolution. Molecular evolution traditionally uses evidence from species that are alive today to determine what their ancestors may have looked like, whereas this new research promotes the importance of using fossil records in conjunction with the molecular models.

Dr Ezard, from Biological Sciences and the Institute for Life Sciences at Southampton, says: “Because planktonic foraminifera have been around for many millions of years and rocks containing groups of their species can be dated precisely, we can use their fossils to see evidence of how species evolve over time. We can also see how differences between individual members of species develop and, in theory, how a new species comes into existence.

“The controversial hypothesis we test is that the processes leading to a new species coming into existence provoke a short, sharp burst of rapid genetic change. This is controversial because it is very difficult to detect these new species coming into existence accurately without the fossil data; it is more commonly determined from assumptions made from the study of species alive today using molecular evidence.”

In the paper, Dr Ezard and colleagues, Dr Gavin Thomas from the University of Sheffield and Professor Andy Purvis from Imperial College London, highlight the importance of using fossil and molecular evidence to study evolution. Their intention is that the use of both types of data will become widespread in the future study of evolution.

To support his research, Dr Ezard has received an Advanced Fellowship from the Natural Environment Research Council (NERC) to study how variation among individuals generates variation among species. He will conduct this interdisciplinary research in the Centre for Biological Sciences at the University, in close collaboration with researchers from Ocean and Earth Science at the National Oceanography Centre, Southampton.

Watch Dr Thomas Ezard, NERC Advanced Senior Research Fellow, Centre for Biological Sciences

Article Source : University of Southampton.

By Science and Universe

Microbes can influence evolution of their hosts

Microbes can influence evolution of their hosts

The tree of life made out of Nasonia microbes. (Robert Brucker/Vanderbilt)

You are not just yourself. You are also the thousands of microbes that you carry. In fact, they represent an invisible majority that may be more you than you realize.

These microscopic fellow travelers are collectively called the microbiome. Realization that every species of plant and animal is accompanied by a distinctive microbiome is old news. But evidence of the impact that these microbes have on their hosts continues to grow rapidly in areas ranging from brain development to digestion to defense against infection to producing bodily odors.

Now, contrary to current scientific understanding, it also appears that our microbial companions play an important role in evolution. A new study, published online on July 18 by the journal Science, has provided direct evidence that these microbes can contribute to the origin of new species by reducing the viability of hybrids produced between males and females of different species.

“It was a high-risk proposition. The expectation in the field was that the origin of species is principally driven by genetic changes in the nucleus. Our study demonstrates that both the nuclear genome and the microbiome must be considered in a unified framework of speciation,” said Associate Professor of Biological Sciences Seth Bordenstein who performed the study with graduate student Robert Brucker.This study provides the strongest evidence to date for the controversial hologenomic theory of evolution, which proposes that the object of Darwin’s natural selection is not just the individual organism as he proposed, but the organism plus its associated microbial community. (The hologenome encompasses the genome of the host and the genomes of its microscopic symbiotes.)

They conducted their research using three species of the jewel wasp Nasonia. These tiny, match-head sized wasps parasitize blowflies and other pest flies, which make them useful for biological control.

Colored scanning electron microscope image of an adult Nasonia female.
(Robert Brucker/Vanderbilt)

“The wasps have a microbiome of 96 different groups of microorganisms,” said Brucker. Two of the species they used (N. giraulti and N. longicornis) only diverged about 400,000 years ago so they are closely related genetically. This closeness is also reflected in their microbiomes, which are quite similar. The third species (N. vitripennis), on the other hand, diverged about a million years ago so there are greater differences in both its genome and microbiome, he explained.

The mortality of hybrid offspring from the two closely related species was relatively low, about 8 percent, while the mortality rate of hybrid offspring between either of them and N. vitripennis was quite high, better than 90 percent, the researchers established.

“The microbiomes of viable hybrids looked extremely similar to those of their parents, but the microbiomes of those that did not survive looked chaotic and totally different,” Brucker reported.

The researchers showed that the incompatibilities that were killing the hybrids had a microbial basis by raising the wasps in a microbe-free environment. They were surprised to find that the germ-free hybrids survived just as well as purebred larvae. But when they gave the germ-free hybrids gut microbes from regular hybrids, their survival rate plummeted.

“Our results move the controversy of hologenomic evolution from an idea to an observed phenomenon,” said Bordenstein. “The question is no longer whether the hologenome exists, but how common it is?”

Article Source : Vanderbilt University.
By Science and universe