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Genetic variance in fitness indicates rapid contemporary adaptive evolution in wild animals

Published in: Science

Authors: Bonnet et al (there are 40!)


The rate of adaptive evolution, the contribution of selection to genetic changes that increase mean fitness, is determined by the additive genetic variance in individual relative fitness. To date, there are few robust estimates of this parameter for natural populations, and it is therefore unclear whether adaptive evolution can play a meaningful role in short-term population dynamics. We developed and applied quantitative genetic methods to long-term datasets from 19 wild bird and mammal populations and found that, while estimates vary between populations, additive genetic variance in relative fitness is often substantial and, on average, twice that of previous estimates. We show that these rates of contemporary adaptive evolution can affect population dynamics and hence that natural selection has the potential to partly mitigate effects of current environmental change.

You can access the paper here

Press Release – University of Auckland

“Fuel of evolution” more abundant than previously thought in wild animals

The raw material for evolution is much more abundant in wild animals than we previously believed, according to new international research led from The Australian National University (ANU).

Populations respond to new selection pressures, such as climate change, via genetic changes in characteristics that favour the survival and reproduction of individuals.  The rate at which evolution occurs depends crucially on genetic differences between individuals in their ability to survive and reproduce.

Led by Dr Timothée Bonnet from ANU, an international research team wanted to know how much of this “fuel” of evolution exists in wild animal populations. The answer: two to four times more than previously thought.

We often think of the process of evolution as something that proceeds extremely slowly, visible only over geological ages.  According to Dr Bonnet, “Researchers have however identified many examples of evolution occurring in just a few years, and discovery of these examples has accelerated recently thanks to technological progress in genetics and statistics”.

Local examples of fast evolution can be found in the species that have been introduced to Aotearoa New Zealand– in many cases, species have rapidly adapted to very different contexts than their native range, for example New Zealand weasels are generally larger than the European populations that they derived from. We can also see considerable and rapid change in many of our domesticated and farmed species through ‘artificial’ (human-directed) selection.

In this new study, the team evaluated the extent of genetic differences for animal survival and reproduction systematically on a large scale, using a new statistical method standardised across the species. The team of 40 researchers from 27 scientific institutions used studies of 19 populations of wild animal around the world. These included hihi in Aotearoa New Zealand, superb fairy-wrens in Australia, spotted hyenas in Tanzania, song sparrows in Canada and red deer in Scotland. The different studies have been running for an average of nearly thirty years each, generating a remarkable resource of detailed records on wild animal populations. For hihi, the two datasets, from populations on Tiritiri Matangi island and at Zealandia Sanctuary, represent a combined 31 years and 90,000 hours of fieldwork from dedicated conservation staff, volunteers and students.

“For each study, we needed to know when each individual was born, who they mated with, how many offspring they each had, and when they died. Bringing all the 19 studies together gave us an incredible 2.6 million hours of field data collection over several decades. We combined this with genetic information on each animal studied to estimate the extent of genetic differences in their ability to reproduce, in each population,” Dr Bonnet said.

After three years of trawling through reams of data and developing new statistical methods, Dr Bonnet and the team were able to quantify this genetic variation, which is what controls how much natural selection can cause genetic changes in each population. The answer was, in general, much higher than previous estimates.

“The method gives us a way to measure the potential of populations to evolve in response to natural selection. Being able to see so much potential change came as a surprise to the team,” Dr Bonnet said.

Professor Loeske Kruuk also from ANU (and now at the University of Edinburgh, UK) commented, “This has been a remarkable team effort that was feasible because researchers from around the world were happy to share their data in a large collaboration. It also shows the value of long-term studies with detailed monitoring of animals throughout their life for helping us understand the process of evolution in the wild.”

According to the researchers, their findings also have implications for predictions of species’ adaptability to environmental change.

“This research has shown us that evolution is a much more significant driver than we previously thought in the adaptability of populations to current environmental changes,” Dr Bonnet said.

Dr Bonnet said that with the habitats of many species changing at an increasing rate, there is no guarantee that these populations will be able to keep up. In fact, it might be the current fast rates of evolution that are buffering some of the accelerating changes in species environments – and there may be a point at which that change becomes too fast to keep up with, and we start to see population sizes decrease.

Co-author Dr Anna Santure from Waipapa Taumata Rau – the University of Auckland – said the results give hope for the many threatened species in Aoteaora New Zealand – their capacity to continue to adapt is still likely to be significant, as long as we can act to remove or mitigate the major threats to them, including habitat loss, predation and climate change.

Commentary from Dr Anna Santure:

How fast can populations adapt? It seems faster than we previously thought, based on a large global study examining rates of evolution in 15 different species, including the threatened Aotearoa New Zealand hihi (stitchbird). The study used long term data – spanning over 2.6 million hours of fieldwork study across species – to determine the contribution of genes versus environment to differences in the ability of individual animals to survive and reproduce. A higher genetic contribution to survival and reproduction means that populations are more able to rapidly adapt to new selection pressures. Where previous studies across species had suggested that the ability to adapt was very limited for many species, in this study, applying new statistical methods, most species showed capacity to rapidly respond to selection, which in turn puts them at a lower risk of extinction.

Dr Anna Santure, a contributing author from the University of Auckland, said that the hihi team that she works with had been delighted to add their very precious hihi datasets to this global analysis. Two of our reintroduced hihi populations – on Tiritiri Matangi Island in the Hauraki Gulf, and Zealandia wildlife sanctuary in Wellington – have been intensively studied since they were established, which means breeding and survival data is available for every bird. The new analysis agreed with previous analysis Anna and her team had done for hihi that suggested they have low capacity to adapt but are buffered from extinction by conservation management actions such as provisioning food and parasite and predator control. However, the general finding from this new global research was optimistic for the ability of many other threatened species to adapt, particularly if habitat loss and climate change can be slowed from their current increasingly fast rates of change.

Written by Dr John Ewen

I have been interested and working with hihi since I was involved with establishing the Tiritiri Matangi island population through translocation in 1995. I am now employed as a Research Fellow at the Zoological Society of London and have been here since 2004. My research is multi-disciplinary and focusses on small population biology and management. I use decision science to assist in planning hihi management and drive our applied research with this species and have experience in molecular and behavioural ecology, wildlife health and nutrition and reintroduction biology.


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