Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New species thanks to different ways of seeing

02.10.2008
Eye colour and hair colour play a role in human partner choice, but visual stimuli can also determine mating preferences in the animal kingdom.

In many species, the male’s fortunes in the mating stakes are decided by a conspicuous breeding dress. A study of brightly coloured fish has now demonstrated that this has less to do with aesthetics than with the sensitivity of female eyes, which varies as a result of adaptation to the environment.

Females more attuned to blue will choose a metallic blue mate, while those better able to see red will prefer a bright red male. These mating preferences can be strong enough to drive the formation of new species – provided that habitat diversity is not reduced by human activities.

The role of selection in the formation of new species has yet to be fully explained in evolutionary biology. The development of brightly coloured cichlid species in African lakes within only a few thousand years – a brief period on the evolutionary timescale – supports the hypothesis that mating preferences may contribute to speciation, without populations being geographically isolated from each other. In the case of cichlids, it has been suggested that selection is attributable to differences in colour perception. Compelling evidence for this theory has now been provided for the first time in a study just published in the journal Nature.

Seeing and being seen

In the study, evolutionary biologist Ole Seehausen (Eawag and Bern University) and his co-authors demonstrate that female cichlids from Lake Victoria whose eyes are more sensitive to blue tend to prefer blue-coloured males, while females with photoreceptors better able to detect red light choose males with red nuptial coloration. The different visual receptor pigments were distinguished by the team on the basis of DNA and protein sequences. The DNA sequence of the genes underlying the visual pigments also shows that specialization did not occur by chance but was in turn due to natural selection. Colour sensitivity differs according to the water depth at which the fish are found. Females living in deeper water are more sensitive to red, and those in shallower water are more sensitive to blue. The adaptation of visual receptors to the prevailing ambient light colour confers an advantage on fish in a certain depth range. They are better able to navigate and, for example, will find more food than non-adapted fish. At the same time, the males have evidently also adapted to this situation: males with a red breeding dress predominate in deeper water, while blue-coloured males are dominant in shallower water.

Two species are formed when ambient light changes only gradually with increasing water depth, a condition given in relatively clear waters. This means that there is sufficient room for the different genetic variants to exploit the competitive advantage conferred by their visual specialization and colour in their particular niche.

Reasons for dramatic decline of species

Besides demonstrating one way in which new species can be formed, the latest findings provide a mechanistic explanation for the dramatic loss of species diversity that has occurred in Lake Victoria over the past 25 years. Eutrophication of the lake due to agricultural runoff, deforestation and urbanization has substantially increased the turbidity of the water. As a result, ambient light changes dramatically within only a few metres of the water column. Accordingly, the different ecological niches are now so small and so close together that the mechanism of genetic adaptation can no longer operate. Thus, the authors found that at sites with turbid water, rather than separate red and blue species, an intermediate form predominated, not specifically adapted to either of the light niches. It is very likely that merging of species, driven by environmental changes, has contributed significantly to the decline of cichlid species diversity in Lake Victoria from more than 500 to the present total of around 250 species within merely 25 cichlid generations.

Box: What is a species?

Various concepts of a species are found in evolutionary biology. What all have in common is that populations of organisms are assigned to different species if they coexist in nature over many generations in the same site without genetically merging. Numerous species hybridize occasionally but remain differentiated if mechanisms exist to restrict gene flow. The definition of a species as a group of individuals not capable of interbreeding with members of other species is a popular misconception.

Andri Bryner | alfa
Further information:
http://www.eawag.ch

More articles from Life Sciences:

nachricht Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden

nachricht The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>