Global cooling caused diversity of species in orchids, confirms study


Date:
July 10, 2023
Source:
University of Bath
Summary:
Research shows global cooling of the climate 10 million years ago
led to an explosion of diversity in terrestrial orchids.


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FULL STORY ========================================================================== Research led by the Milner Centre for Evolution at the University of Bath looking at the evolution of terrestrial orchid species has found that
global cooling of the climate appears to be the major driving factor
in their diversity. The results help scientists understand the role of
global climate on diversity of species, and how our current changing
global climate might affect biodiversity in the future.

One of the largest families of plants, there are around 28,000 species
of orchids growing across the world. These plants are known for their
huge variety of different sized and shaped flowers, so why are there so
many species Climate change driving speciation Charles Darwin studied
orchids as a model for evolution through natural selection, proposing
that they evolved an array of different flowers gradually over time to
attract specific pollinators.

However, scientists at the Universities of Bath and York studying almost
1500 species of terrestrial orchids, have found that rather than evolving gradually over thousands of years, these plants diversified relatively
quickly due to changes in global temperature.

Analysing thousands of DNA sequences, they compiled a family tree showing relationships between the species, and used statistical models to test
how changes in climate during the Earth's history might have driven the formation of new species. They then tested the different possible models
using more than 2.5 million records of geographical distributions.

They found evidence that most of the species appeared during the last
10 million years, coinciding with global cooling, as calculated from
geological records.

Modelling the probability of different drivers of speciation suggested
that global cooling is 700 times more likely to influence speciation of
orchids than time alone.

Everything, everywhere, all at once Dr Jamie Thompson, first author of the paper and researcher at the Milner Centre for Evolution at the University
of Bath, said: "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.

"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 also found that the speciation
rate -- how quickly new species arise -- wasn't dependent on how many
species there were to begin with.

Dr Nick Priest, Lecturer at the Milner Centre for Evolution and senior
author of the study, said: "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.

"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." Dr Katie Davis, Lecturer in Palaeobiology at the University of York, said:
"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."
* RELATED_TOPICS
o Plants_&_Animals
# Nature # Evolutionary_Biology # Endangered_Plants
o Earth_&_Climate
# Climate # Global_Warming # Environmental_Awareness
o Fossils_&_Ruins
# Evolution # Early_Climate # Charles_Darwin
* RELATED_TERMS
o Attribution_of_recent_climate_change o
Temperature_record_of_the_past_1000_years o Dinosaur o
Orchidaceae o Tunguska_event o Climate o Homo_ergaster o
Homo_(genus)

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Story Source: Materials provided by University_of_Bath. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Jamie B. Thompson, Katie E. Davis, Harry O. Dodd, Matthew A. Wills,
Nicholas K. Priest. Speciation across the Earth driven by global
cooling in terrestrial orchids. Proceedings of the National Academy
of Sciences, 2023; 120 (29) DOI: 10.1073/pnas.2102408120 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230710180446.htm

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