Origin of the species



Dr Fred Gurgel and Gareth Belton examining macroalgae in the research lab at Ningaloo Station.
Image: Gary Cranitch.

 

21 May 2010 
 
Examining the genetic differences in algae can help scientists understand the evolution of marine plant species and assist ocean conservation, according to the University of Adelaide's Dr Carlos Frederico "Fred" Gurgel and PhD student Gareth Belton.
 
Their field of research is called Phycology, or marine botany – the study of algae and seagrasses. They have been scuba diving, snorkelling and searching the ocean for specimens of macroalgae for the University of Adelaide and the South Australian State Herbarium and the South Australian Research and Development Institute – Aquatic Sciences branch.
 
Fred and Gareth use taxonomy, morphology (the study of shapes, structure and anatomy), molecular biology (DNA analyses) and biogeography to understand the evolution, distribution and biodiversity of marine algae.
 
"Part of our work is to look at any genetic differences between populations of macroalgae found in different places and environments," Gareth explains.
 
"If we find genetic differences between populations we try and understand the reason for the lack of gene flow between these populations, which could be due to ocean currents or prevailing winds. If you find quite significant genetic differences between the populations, we could have a new species rather than different populations," he says.
 
"But if we find only minor differences between populations, we might be seeing the start of speciation. For example, if one population of macroalgae lives in cold, rough conditions in Victoria, and a genetically identical population lives in calm, warm waters here at Ningaloo, with minimal gene-flow between the populations, they may eventually become adapted to their local different environments, differentiate, and become distinct species. The problem is that just by looking at them we can't tell at which stage in the evolutionary process they are. We need to do DNA analysis to understand the whole story," Gareth says.
 
One particular green alga, for example, had always been found growing together with a sponge, in a symbiotic relationship between the two: a plant (the alga) and an animal (the sponge). This structure had been found throughout the Indian Ocean and the western Pacific.
 
"It was assumed to be one species of alga and one species of sponge. Every time we found it, we knew exactly what they were," Fred explains.
 
 
"But recent molecular analysis conducted in our lab is now showing that, even though they all look the same, in different areas they are composed of different species of green algae and different species of sponge. You can't tell that from looking at it, you can only tell through DNA analysis. The levels of genetic diversity observed can even put these newly discovered entities in different genera.
 
"Just by looking at the morphology you cannot quantify the true biodiversity," he says.


Dr Fred Gurgel returns from a dive.
Image: Gary Cranitch.

 

This has important implications for conservation of coral reefs.
 
"We now know that there is greater macroalgal diversity than formerly appreciated," Gareth says.
 
"If we lose a population in the Ningaloo Reef, for example, we can't assume that's okay because it's still found in other tropical environments, like the Great Barrier Reef. It's not. It could be a separate species or sub-species, and it will be gone forever. Modern conservation efforts aim not only to ensure the survival of species but also to protect the genetic diversity within species. Once the genetic diversity is lost, the likelihood a species will disappear, increases," he says.
 
Fred's team, in collaboration with Murdoch University's Dr John Huisman and Melbourne University's Gerry Kraft, is working on a book of the red algal flora of the Great Barrier Reef that will be published by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Australian Biological Resources Study as part of the Algae of Australia series.
 
"But recent molecular analysis conducted in our lab is now showing that, even though they all look the same, in different areas they are composed of different species of green algae and different species of sponge. You can't tell that from looking at it, you can only tell through DNA analysis. The levels of genetic diversity observed can even put these newly discovered entities in different genera.
 
"Just by looking at the morphology you cannot quantify the true biodiversity," he says.
 
This has important implications for conservation of coral reefs.
 
"We now know that there is greater macroalgal diversity than formerly appreciated," Gareth says.
 
"If we lose a population in the Ningaloo Reef, for example, we can't assume that's okay because it's still found in other tropical environments, like the Great Barrier Reef. It's not. It could be a separate species or sub-species, and it will be gone forever. Modern conservation efforts aim not only to ensure the survival of species but also to protect the genetic diversity within species. Once the genetic diversity is lost, the likelihood a species will disappear, increases," he says.
 
Fred's team, in collaboration with Murdoch University's Dr John Huisman and Melbourne University's Gerry Kraft, is working on a book of the red algal flora of the Great Barrier Reef that will be published by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Australian Biological Resources Study as part of the Algae of Australia series.