CLOWN FISH like one named Nemo may have put their marine environment on Hollywood’s map, but their coral reef neighbours, the hamlet fish, have now made a significant contribution to research on evolution.
Scientists in Britain and Canada who undertook a study of the colourful Caribbean species have found that different forms of evolution can occur in one place regardless of any physical separation.
The finding, published yesterday in the journal Global Ecology and Biogeography, significantly improves understanding of "speciation" as in the evolutionary method by which new species arise.
Up to now it had been presumed that 10 species of the hamlet fish had developed their own distinct colour patterns due to their development in separate ocean locations. For example, the blue hamlet is found only in the Florida region.
However, in some areas up to seven varieties of hamlet can be found on a single reef.
The prevailing theory for this has been that falling sea levels divided the original species in the past. When sea levels rose, the different colour types were thrown back together again.
However, ecologists at the University of East Anglia and Simon Fraser University in Canada have found little evidence of this theory, and they believe that the hamlet fish colour schemes evolved differently regardless of rather than because of geographical difference.
The scientists studied thousands of underwater surveys made by scuba divers as part of a volunteer coral reef survey project.
They found that even widespread hamlet species are not found everywhere, and they identified high-density hotspots for each species.
The research also suggests that ecological factors, such as competition for food or habitat, may influence how different hamlet species co-exist.
“Our findings suggest that ecology may better explain the evolution of hamlets than geographical separation,” Dr Ben Holt of the University of East Anglia’s school of biological sciences said yesterday.
In a separate study published this week, a European project involving Irish scientists from NUI Galway and Queen’s University in Belfast has found that recently introduced seaweed types from Japan and California are spreading more rapidly in Europe than ever before. This may be due to shipping and aquaculture imports.
However, coastal environments appear to be losing their resistance to seaweed “invaders”, according to a paper published on the team’s behalf in a Royal Society journal this week by Prof Mark Johnson of NUIG.
There are over 500 seaweed types in Ireland, and some 126 non-native species from Asia and the US have been recorded in Europe over the past century.