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Clocktower.Tuesday 16 October 2018 2:37pm

Matthew Larcombe image
Dr Matthew Larcombe

Have you ever wondered why so many species live in tropical rainforests? Or why some groups of organisms have thousands of species, and other groups only a few?

Biologists have been thinking, and arguing, about this for hundreds of years. One school of thought says diversity is limited by competition for ecological space, while another says evolution allows the expansion of ecological space so there is no limit on global species diversity.

Getting to the bottom of this debate is vital for understanding how diversity evolves, and estimating the resilience of biodiversity to human disturbance.

University of Otago findings published today in Nature Communications show - using conifers - that competition and evolution work together to shape biodiversity. The study uses a cross disciplinary approach to show this is probably facilitated by the multi-dimensional nature of ecological niches.

Monkey puzzle tree image
Monkey puzzle tree conifers in southern Chile. Photo: Greg Jordan

“To answer these questions you need to study relationships between hundreds of species. The problem is that it's really difficult to get meaningful information about the niches of that many species, so in the past simplistic proxies like body size have been used,” Department of Botany researcher Dr Matthew Larcombe says.

Researchers from Otago's Department of Botany and Department of Mathematics and Statistics joined forces to apply a cutting-edge physiological model to address this long-standing question.

“Using the physiological model allowed us to quantify multiple ecologically relevant niche traits in all of the 455 conifer species in our dataset.”

Working with colleagues from the University of Tasmania, Australia, and the University of Bayreuth, Germany, the study shows that in a group of species, one niche dimension, such as the minimum temperature needed for photosynthesis, could be actively evolving, while another niche dimension, like soil nitrogen level required for growth, is constrained by competition.

“In practice we think that variation in niche dimensionality will result in periods when competitive processes prevail and others when evolutionary processes are shaping the accumulation of biodiversity,” Dr Larcombe says.

“We've known that habitat loss and fragmentation increases the risk of extinction, but this research also suggests that the evolution of new species could be limited by these factors if they increase competition, which they probably do.”

Professor David Bryant, of the Department of Maths and Statistics, said the study shows the great benefit of cross disciplinary collaboration, both within this university and internationally.

For more information, contact:

Dr Matthew Larcombe
Lecture, Department of Botany,
University of Otago
Tel 3 479 3943

Professor David Bryant
Department of Mathematics and Statistics
University of Otago
Tel 3 479 7889

Guy Frederick
Communications Adviser
University of Otago
Tel 3 479 7688

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