Agriculture & Climate Change, UK (Commonwealth Union) – The combination of favorable climate, geographic diversity, long periods of stable conditions, and high levels of competition along with predation are all contributions to the high levels of species diversity near the equator were considered possibilities by many scientists in the past.
In recent findings scientist have utilized almost half a million fossils to find a solution to a 200-year-old scientific mystery. The mystery revolves around why the number of various species is the highest in close proximity to the equator and lessens steadily towards the polar regions. The findings published recently in the journal Nature, provided valuable details onto how biodiversity is produced over long timescales, and the ways climate change impacts the richness species across the world.
A widely held view according to researchers was that marine and terrestrial systems species. Demonstrate a ‘latitudinal diversity gradient’, with biodiversity reaching its peak at the equator. However, till now, insufficient fossil was a stumbling block for researchers to thoroughly evaluate the ways this diversity gradient 1st arose.
This recent study, led by scientists from the Department of Earth Sciences at the University of Oxford, utilized a group of unicellular marine plankton known as planktonic foraminifera. Researchers analyzed 434,113 entries in a global fossil database, that included the past 40 million years. They then evaluated the association between the number of species over time and space, with possible drivers of the latitudinal diversity gradient, like sea surface temperatures along with ocean salinity levels.
The modern-day latitudinal diversity gradient 1st began to emerge roughly 34 million years back, as the Earth went from a warmer to cooler climate, according to the researchers who also noted that this gradient stayed shallow at the start, until roughly 15–10 million years back, when it steepened to a large extent. This concurred with a significant increase in global cooling.
Peak richness for planktonic foraminifera took place at increased latitudes from 40–20 million years back. By roughly 18 million years ago, the peak richness moved to between 10° to 20° latitude, consistent with the diversity pattern noticed presently, was further noticed by researchers along with a powerful positive association between species richness and sea surface temperatures, where as they were modelled over time at specific places, or at different place in a specific time.
The researchers then found that there was also a positive association between species richness and the power of the thermocline, where the temperature gradient existing between the warmer mixed water at the surface of the ocean as well as the cooler deep under the water.
The findings showed that the modern-day distribution for species richness of planktonic foraminifera could be defined by the steepening of the latitudinal temperature from the equator to the poles in the past 15 million years. This possibly paved the way for further ecological niches in tropical regions within the water column, contrasted with higher latitudes, furthering increased rates of speciation, as indicated by researchers.
Planktonic foraminifera have its originations in Early to Middle Jurassic period which is roughly 170 million years back. They can be observed in oceans across the globe. Due to their formation of hard outer shells, preservations can occur in huge numbers. The huge worldwide availability of planktonic foraminifera and their exceptional fossil record in the past 66 million years made them a perfect group for researchers.
“Planktonic foraminifera arguably have one of the most complete species-level fossil records of any group of organisms. Our study builds on decades of important research to uncover how planktonic foraminiferal distributions have changed across space and through time. It’s a privilege to synthesize these data to propose something fundamental about the drivers of ecological and evolutionary change,” explained Dr Erin Saupe from the Department of Earth Sciences, at the University of Oxford, who was the lead author of the study.