The origin of species
A study which will unravel the evolutionary history of a species by combining high-tech digital mapping with DNA sequencing is being undertaken at the University of St Andrews.
Focusing on bushcrickets but with potential relevance to everything from human population to pest species studies, the project will try and explain why the crickets differ depending on their geographical location and, ultimately, explain what factors contribute to the creation of a species.
The three-year study, led by Dr Mike Ritchie of the School of Biology and funded by a £313,000 Natural Environmental Research Council (NERC) grant, will provide a framework applicable to future studies on other species and is based on two areas, never combined in this way before.
On-site in the South of France, biologists will locate crickets in the field using a global positioning system (GPS) where they will measure a number of morphological characters (size, shape) and take tissue samples for subsequent DNA analysis in the St Andrews laboratory. This information will help establish how individuals, populations and subspecies are related to each other.
Meanwhile, geography experts will feed a wealth of data gathered from various sources into a state- of-the-art geography information system (GIS). For example, to build detailed temperature models of mountain valleys, data loggers will be set out in the field to record the temperature every half hour all year round. Other data (some originating from satellite imaging) will be downloaded from the internet. The information, which includes Dr Ritchie’s own data collected from nearly 15 years’ work on bushcrickets, will then be combined to provide a rich dataset of factors ranging from the climate from the end of the last ice age to the present, to the number of bushcrickets per square mile and their different mating strategies.
Dr Ritchie said, “The make-up of a species is usually a series of different populations which may have split due to geographic or historical issues such as climate change, eventually leading to the current patchwork structure. Examining bushcrickets is ideal because populations of the species are extremely different from each other and, therefore, if we can work out their past history and what climatological or geographic factors influence them, we can figure out what has caused the current structure. For example, in some areas, the climate now may lead to differences in shape but other differences may result from historical changes in distribution, for example during the last ice age. Likewise, their communication system varies hugely, depending on where they are. You can actually hear their song change as you drive through France, and song changes may influence gene flow between populations, again, just like human languages.
He continued, “There is great potential in this approach for exploring other species – in principal, the approach we are developing could be used for any species including humans – our languages typically change in the same regions as the bushcrickets! Factors such as climate are likely to have played a key role so, by using high-tech software packed with rich datasets on climate change and terrain type, we will be able to explain why species are usually very variable in only particular places, such as major mountain ranges. In the past, determining evolutionary processes in contemporary species has only been carried out by biologists but, by throwing detailed geographical data into the equation, the picture should become much clearer”.
Bushcrickets are found in the South of France, the Alps and the Pyrenees – areas less affected by human development, although current development might eventually effect the patterns of variation observed. With long antennae and spindly jumping legs, they are roughly the size of a small mouse.
Dr Ritchie said, “They are an extremely variable, and therefore fascinating species, with variation in many different traits such as their behaviour, morphology, life cycles and DNA. They also have an interesting mating technique where males sing to attract the females and, when the female finds the male, he gives her a nuptial gift – a protein food package containing sperm which the female then eats.”
In addition to Dr Ritchie, the team comprises of David Kidd, a postgraduate research assistant (and St Andrews graduate); Dr Nicholas Pepin, a climatologist from Portsmouth University; Ruth Hammill, a postdoctoral researcher and Laura Spooner, a PhD student.
NOTE TO EDITORS – Photographs of bushcrickets (in jpeg form) available from Claire Grainger – contact details below.
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