̽��ֱ�� of Cambridge - Javier Igea

Going up: birds and mammals evolve faster if their home is rising

jg533 — Thu, 02 Sep 2021 15:11:37 +0000

Researchers at the ̽��ֱ�� of Cambridge have combined reconstructions of the Earth’s changing surface elevations over the past three million years with data on climate change over this timeframe, and with bird and mammal species’ locations. Their results reveal how species evolved into new ones as land elevation changed - and disentangle the effects of elevation from the effects of climate.

̽��ֱ��study found that the effect of elevation increase is greater than that of historical climate change, and of present-day elevation and temperature, in driving the formation of new species – ‘or speciation’.

In contrast to areas where land elevation is increasing, elevation loss was not found to be an important predictor of where speciation happens. Instead, present-day temperature is a better indicator of speciation in these areas.

̽��ֱ��results are published today in the journal Nature Ecology and Evolution.

“Often at the tops of mountains there are many more unique species that aren’t found elsewhere. Whereas previously the formation of new species was thought to be driven by climate, we’ve found that elevation change has a greater effect at a global scale,” said Dr Andrew Tanentzap in the ̽��ֱ�� of Cambridge’s Department of Plant Sciences, senior author of the paper.

As land elevation increases, temperature generally decreases and habitat complexity increases. In some cases, for example where mountains form, increasing elevation creates a barrier that prevents species moving and mixing, so populations become reproductively isolated. This is the first step towards the formation of new species.

̽��ֱ��effect of increasing elevation on that rate of new species formation over time was more pronounced for mammals than for birds; the researchers think this is because birds can fly across barriers to find mates in other areas. Birds were affected more by present-day temperatures; in birds, variation in temperature creates differences in the timing and extent of mating, risking reproductive isolation from populations of the same species elsewhere.

Until now, most large-scale studies into the importance of topography in generating new species have only considered present-day land elevation, or elevation changes in specific mountain ranges.

“It’s surprising just how much effect historical elevation change had on generating the world’s biodiversity – it has been much more important than traditionally studied variables like temperature. ̽��ֱ��rate at which species evolved in different places on Earth is tightly linked to topography changes over millions of years,” said Dr Javier Igea in the ̽��ֱ�� of Cambridge’s Department of Plant Sciences, first author of the paper.

He added: “This work highlights important arenas for evolution to play out. From a conservation perspective these are the places we might want to protect, especially given climate change. Although climate change is happening over decades, not millions of years, our study points to areas that can harbour species with greater potential to evolve.”

̽��ֱ��researchers say that as the Earth’s surface continues to rise and fall, topography will remain an important driver of evolutionary change.

This research was funded by Wellcome, the Gatsby Charitable Foundation and the Isaac Newton Trust.

Reference

Igea, J. & Tanentzap, A.J.: ‘Global topographic uplift has elevated speciation in mammals and birds over the last 3 million years.’ Nature Ecology & Evolution, September 2021. DOI: 10.1038/s41559-021-01545-6

̽��ֱ��rise and fall of Earth’s land surface over the last three million years shaped the evolution of birds and mammals, a new study has found, with new species evolving at higher rates where the land has risen most.

Whereas previously the formation of new species was thought to be driven by climate, we’ve found that elevation change has a greater effect at a global scale

Andrew Tanentzap

Pablo Heimplatz on Unsplash

Wild Kea, New Zealand

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Species ‘hotspots’ created by immigrant influx or evolutionary speed depending on climate

fpjl2 — Wed, 06 Feb 2019 19:01:52 +0000

Some corners of the world teem with an extraordinary variety of life. Charles Darwin noted that: “ ̽��ֱ��same spot will support more life if occupied by very diverse forms.”

̽��ֱ��question of how these ‘hotspots’ of biodiversity – from California to the Galapagos – acquired such a wealth of species has long puzzled naturalists.

Now, scientists at the ̽��ֱ�� of Cambridge have conducted a ‘big data’ study of almost all the world’s mammal and bird species to reveal the answer – and it’s very different depending on climate.

According to the study, tropical hotspots close to the equator have generated new species at a much faster rate than their surrounding areas during the last 25 million years of evolution.

However, biodiversity hotspots in more temperate northerly regions, such as the Mediterranean basin and Caucasus Mountains, are mainly populated with immigrant species that originated elsewhere.

Scientists say these migrants may have been escaping the effects of long-term “geological processes” such as vast encroaching glaciers. Warmer climes, as well as peninsulas and mountain ranges, could have offered shelter.

̽��ֱ��researchers say that their new study, published today in the journal Science Advances, shows how these “contrasting macroevolutionary routes” have shaped the uneven distribution of species across the planet.

“We’ve known for decades that just a subset of places on Earth, no more than 20%, contain about half of all vertebrate species. However, we lacked the tools and data to understand why these patterns exist,” said senior author Dr Andrew Tanentzap, from Cambridge’s Department of Plant Sciences.

“Large-scale initiatives to map species across the planet and in the Tree of Life, as well as advances in computing, are expanding our understanding of evolution in exciting ways. This study can now provide an answer to the old question of why diversity varies so much across the world.”

Cambridge scientists used new computational techniques to combine several giant datasets. These included the global distribution of 11,093 bird species and 5,302 mammals, and detailed evolutionary trees that track the origin of thousands of organisms through deep time.

In this way, the researchers were able to analyse the development of particularly species-rich areas within each of the Earth’s great “biogeographical regions” – from Australasia to the Nearctic.

They found that biodiversity hotspots in the tropics, such as South American forests and Indonesian islands, had higher rates of “speciation” – the formation of new and distinct species – over the last 25 million years.

For example, speciation rates for birds in hotspots of the Indo-Malay region were, on average, 36% higher than that region’s non-hotspot areas. Hotspots in the Neotropics had almost 28% greater bird speciation compared to non-hotspots.

“Species generation is faster in the tropics, but we can now see it is extra-quick in these hotspots of biodiversity,” said study lead author Dr Javier Igea, also from Cambridge’s Department of Plant Sciences.

“More rainfall and hotter temperatures bolster the ecosystems of tropical hotspots, producing more plants, more animals that feed on those plants, and so on,” he said.

“ ̽��ֱ��greater available energy and range of habitats within these hotspots supported the acceleration of species diversification.”

̽��ֱ��tropical hotspot of Madagascar, for example, holds 12 species of true lemur that diversified in the last ten million years. All of the 17 species of earthworm mice endemic to the Philippines were generated in the last six million years.

̽��ֱ��famously diverse finches Darwin found in the Galapagos Islands, as featured in his revolutionary book On the Origin of Species, are an iconic example of rapid speciation in a tropical hotspot.

However, when it came to the more temperate regions of the Nearctic (North America) and Palearctic (Eurasia and North Africa), the researchers discovered a different story.

While the hotspots of these regions also had a wider range of resource and habitat than neighbouring areas, the data from the evolutionary – or phylogenetic – trees revealed that most of their animals “speciated” somewhere else.

“Biodiversity hotspots in temperate zones have been shaped mainly by migration that occurred during the last 25 million years,” said Igea.

“We suspect that this influx of immigrant species resulted from climate fluctuations across millions of years, particularly cooling. Biodiversity hotspots may have acted as a refuge where more species could survive in harsh climatic conditions,” he said.

Igea points to species such as the Iberian lynx, now a native of the Mediterranean Basin hotspot, but found in central Europe during the Pleistocene – prior to the last Ice Age.

Or the yellow-billed magpie, which became isolated in California after becoming separated from its ancestral species – most likely due to glaciations – over three million years ago.

“We found that hotspots across the world all have a greater complexity of habitats and more environmental energy, but the processes that drive the biodiversity are very different for tropical and temperate zones,” Igea said.

For Tanentzap, the importance of species migration in temperate regions suggests that maintaining connectivity between hotspots should be a priority for future conservation efforts.

“Many of these hotspot regions have species found nowhere else on Earth, yet face devastating levels of habitat loss. Protecting these areas is vital to conserving the natural world’s diversity,” he said.

Reference
Igea, J et al. Multiple macroevolutionary routes to becoming a biodiversity hotspot. Science Advances; 6 Feb 2019; DOI: 10.1126/sciadv.aau8067

A bold response to the world’s greatest challenge
̽��ֱ�� ̽��ֱ�� of Cambridge is building on its existing research and launching an ambitious new environment and climate change initiative. Cambridge Zero is not just about developing greener technologies. It will harness the full power of the ̽��ֱ��’s research and policy expertise, developing solutions that work for our lives, our society and our biosphere.

New research reveals that biodiversity ‘hotspots’ in the tropics produced new species at faster rates over the last 25 million years, but those in temperate regions are instead full of migrant species that likely sought refuge from shifting and cooling climates.

Many of these hotspot regions have species found nowhere else on Earth, yet face devastating levels of habitat loss

Andrew Tanentzap

Museum of Zoology / Chris Green

Galapagos finch specimens from Museum of Zoology, collected on the second voyage of HMS Beagle that carried Darwin to the Islands. Researchers say these famously diverse finches are an iconic example of rapid speciation in the tropics.

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