Popcorn-like fossils give evidence of environmental influence on species richness

The research by analysing the fossil record of microscopic aquatic creatures called planktonic foraminifera, whose fossil remains resemble miniaturised popcorn and date back millions of years, provided the first statistical evidence that environmental variations can alter species richness.

According to new research led by the University of Southampton, the number of species that can exist on Earth depends on the changes in the Environment.

Dr Thomas Ezard, an evolutionary ecologist at the University of Southampton was the lead author of the study.

The study was published in the June edition of the journal Ecology Letters.

Highlights of the study

• The idea of infinite species on a finite Earth is clearly fanciful; the relevance of upper limits to diversity is a fractious debate amongst evolutionary biologists, ecologists and palaeontologists.

• The study showed statistically for the first time that the upper limit is environmentally dependent.

• It is easy to use and understand that the variations in the environment can alter the spatial gradient of more species in the tropics than at the poles. It is pervasive evidence for its large-scale influence.

• However, on the analysis of species numbers that have changed over time that have assumed that any limit was always been the same, even through periods of massive climate upheaval.

• The data rejected the idea of fixed rules for competition among species and instead show that the limit to the number of species that can co-exist on Earth is much more dynamic.

• Climate and geology are always changing, and the limit changes with them.

• While previous research typically focused individually on either biological, climate change or geological explanations, this new research examined the co-dependence of these factors on how species interact.

• The study found that the number of species was almost certainly controlled by competition among themselves and probably kept within a finite upper limit.

• It was found by observing the fossil history of 210 evolutionary species of macroperforate planktonic foraminifera in the Cenozoic Era from 65 million years ago to the present.

• Mathematical models were used to reveal the environmental changes that influence both the rate of diversification among species and the number of species that can co-exist at once.

• The result of the models suggested that the world is full of species, but that the precise fullness varies through time as environmental changes alter the outcome of competition among species.

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