The Milner Centre for Evolution at the University of Bath revealed that global temperature cooling appears to be the primary driver of terrestrial orchid species diversity.
The findings will help scientists better understand the effect of global temperature on species diversity and how climate change may affect biodiversity in the future.
Orchids are one of the world’s most diverse plant groups, with over 28,000 species found worldwide.
Climate Change Driving Speciation
Charles Darwin studied orchids as a paradigm for natural selection, claiming that through time, they gradually evolved an array of diverse blooms to attract certain pollinators.
However, researchers from the Universities of Bath and York revealed that, rather of developing gradually over thousands of years, these plants diversified rapidly in response to fluctuations in global temperature.
Thousands of DNA sequences were analysed to create a family tree depicting species connections. Statistical models were employed to examine how temperature variations over Earth’s history may have affected the emergence of new species. The researchers then tested the various models using over 2.5 million geographical distribution records.
The majority of the species arose within the last 10 million years, corresponding with global cooling, according to geological data.
Modelling the likelihood of several causes of speciation indicated that global cooling is 700 times more likely to affect orchid speciation than time alone.
Everything, Everywhere, All at Once
Darwin proposed that orchids adapted gradually through natural selection to attract different pollinators, but our data show that it’s more complicated than that. There was an explosion of diversity in terrestrial orchids across the globe within the last 10 million years, with all the major lineages of these plants emerging at roughly the same time.
Dr. Jamie Thompson, Study First Author and Researcher, Milner Centre for Evolution, University of Bath
Dr. Jamie Thompson adds, “We found this correlated with global climate change, so that more species emerged as the climate cooled, giving the first evidence of global cooling driving speciation in these plants.”
Speciation Rate Independent of Diversity
The researchers additionally discovered that the number of species existing in the initial place had no effect on the speciation rate (how quickly new species form).
Our biogeographic analysis revealed consistent effects of climate change on speciation across the Earth. But we were surprised to find that the regions that have high diversity don’t necessarily have high speciation rates. This has implications for conservation strategies—that we can’t just count on preserving a few small pockets of land to protect evolutionary diversity—it’s important to try and conserve everything we possibly can.
Dr. Nick Priest, Study Senior Author and Lecturer, Milner Centre for Evolution, University of Bath
Dr. Nick Priest adds, “What we want to investigate next in all flowering plants is whether there is a simple effect of temperature or if there is a threshold that needs to be passed before there is a surge in speciation. We also want to predict how rising temperatures due to global climate change will impact the processes generating plant biodiversity.”
Our findings also show the importance of considering evolution over geological time scales. Understanding how organisms evolve in response to global environmental change has important implications for conservation and we can only know this by looking at the deep evolutionary history.
Dr. Katie Davis, Lecturer, Palaeobiology, University of York
Source: bath.ac.uk
