IMG_2979Understanding how animals respond to environmental change is a major challenge in biology. Over the course of deep history (millions of years) the extinction of species, the emergence of news species, as well as their migration across the globe has been influenced by environmental change. Take for example the evolution of kangaroo species over the past 25 million years in response to the increasingly hot and dry Australian climate. Australia and Antarctica were once connected and shared a cooler and wetter climate to that of Australia today. As Australia drifted north from Antarctica, the climate became more arid, which meant that the native vegetation changed too. In contrast to the open forests and grassy woodlands that are characteristic of Australia today, millions of years ago the area was dominated by rainforests. As kangaroo species evolved on the Australian continent they became adapted to the changing climate and vegetation communities. Their skulls and teeth became better suited to eating tougher, lower-energy foods and their foot structure better for moving across open grasslands compared to through dense rainforest. It is often hard to conceive of the time scale at which continental drift and evolution take place. Suffice to say it is a very long time!

Zooming into the present and we see that environments also change within the lifetime of one individual. For animals that do not generate their own body heat (about 90% of all animals), even seasonal temperature change imposes a considerable challenge. The body temperature of ectothermic animals (ecto- for ‘outside’, -therm for ‘temperature’) is dependent on ambient temperature. So when the cold temperatures of winter descend, the vital processes of growth, muscle movement and reproduction slow down because of lower body temperatures. Conversely, the heat of summer drives up energy use and oxygen consumption in these animals, pushing the energy budgets of individuals to their limits.

To some extent, ectothermic animals can regulate their body temperature behaviourally. However, most also adjust their behaviour and internal functions (physiology) in response to seasonal temperature change to help maintain growth, movement, reproduction and energy budgets. The process of acclimation (or acclimatisation) is familiar even to us, which we recognise when we go on holidays to places much colder or hotter than what we are used to. After several weeks we start to feel more comfortable at the new temperature, partly due to a process of acclimatization.

The way animals respond to environmental fluctuations within their lifetime is an important part of understanding how more persistent environmental changes, like climate change, impact on species in the long term. Importantly, different animals have different capacities to respond within their lifetime to the changes they experience. Predicting which species will persist in the face of contemporary environmental change therefore requires an understanding of why animals respond differently to short term environmental fluctuations.

An important set of tools for scientists are mathematical models that serve as simplifications of the world in all its complex reality. Modern models of animals in changing environments were pioneered by Richard Levins in his seminal work Evolution in Changing Environments published in 1968. Based on the work of Levins, biologists today generally speak of two distinct types of individual responses to the environment. On one hand, animals can match their physiology to the environment experienced during early development. For example, maternal nutrition can induce metabolic changes in developing embryos. The effects of environmental factors like nutrition on embryonic development often last into adulthood and tend to be considered an ‘irreversible’ type of response. On the other hand, the way individuals respond to the environments they experience later in life, such as seasonal temperature change, are typically reversible and repeatable. Until now, a firm distinction between developmental and reversible responses has been implicit in the way scientists study animals in changing environments.

Recently, my supervisors and I wrote a review article of the current scientific literature in the field. We argue that, contrary to the situation described above, the developmental environment influences the way animals respond to the conditions they face later in life. The interplay between developmental and reversible responses within individuals is important for two reasons. First, animals would benefit from being able to regulate during development those processes that enable them to respond to the conditions they will face later in life. Depending on when an individual is born, they might face considerable environmental fluctuations within their lifetime and will need to change their behaviour and physiology accordingly. Others might go through life with relatively small and transient fluctuations in their environment, and might benefit most from having relatively fixed behaviour and physiology. Second, animals that fix their behaviour and physiology to match the environment experienced during development risk becoming poorly suited when conditions change again later in life. In that situation, animals that can also respond repeatedly throughout life will be more likely to remain well matched to their conditions. The consequence is that, over evolutionary time, the dynamics between developmental and reversible responses to environmental change become mutually reinforcing.

The scientific study of how animals cope with environmental change is only relatively young and there is still much to discover. A more detailed understanding of how life has evolved on Earth over billions of years can be gained from the study of animals in changing environments. Environmental change is also firmly on the agenda more generally in the 21st century. Managing the impact of a growing global society on our environment will require a broad range of research foci. Here I have described one area where we can improve our understanding about which species are likely to persist in the face of contemporary environmental change.

For anyone interested in a copy of our review paper, it can be downloaded here for free until 7 April 2016.

Cheers,

Julian

 

 

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There was a distinct lack of summer rain in southern Queensland this year. By late March, Pippa Kern was starting to think that there would not be another big rain event until next summer and that she would have to give up on her plans to collect the eggs of the ornate burrowing frog (Platyplectrum ornatum) for her research.

And then it rained. A lot!

The short video below follows Pippa out to the Western Downs in Queensland, a fertile flood plain west of the Great Dividing Range. After heavy rain, the landscape is spectacularly transformed. The deep cracking clay soil absorb vast volumes of water which pools in some areas for weeks. These ephemeral pools provide short-term breeding habitat for various different frog species. Many of the frog species that live here only emerge after massive rain events. During the short period of suitable conditions thousands of frogs race to find a mate and breed, as well as gorge themselves on the abundance of insects, before bunkering down again until the next big rain. In the long dry periods between rain, some species shown in the video enter a state of metabolic depression (called aestevation) and can survive in an underground cocoon for years on end!

Stay tuned for the next video when we will follow Pippa into the lab at the University of Queensland to find out how the ornate burrowing frog copes with the challenges of living in such a boom-bust environment.

Last time we followed Pippa Kern on her research expedition to the rainforest of the Scenic Rim, Queensland in search of eggs of the black-soled frog (Lechriodus fletcheri). In this short video, we go with Pippa to the flood plains of the Western Downs, Queensland to search for eggs of the ornate burrowing frog (Platyplectrum ornatum). Check out what she found on her journey:

Hope you enjoy the wildlife!

Cheers,
Julian

L. fletcheri in a breeding pool at O'Reilley's Rainforest Retreat, Canungra, Queensland. Beaman 17-11-13.

Lechriodus fletcheri, the black-soled frog, in a breeding pool at O’Reilley’s Rainforest Retreat, Canungra, Queensland. Photo: Beaman 17-11-13.

This post comes to you in video format. Please follow the link below to find a short video report on Pippa Kern’s latest expedition to collect the eggs of Australian frogs for her PhD research:

http://www.youtube.com/watch?v=L490q8gBVck

Pippa is completing her PhD in physiological ecology in Prof Craig Franklin’s ECO-lab at the University of Queensland, Brisbane (link to the ECO-lab: http://www.uq.edu.au/eco-lab/). Pippa’s research aims to understand how frogs cope with temperature fluctuations experienced as tadpoles, and the consequences of these conditions on the performance of adult frogs. This time round, she’s on her way to O’Reilley’s Rainforest Retreat high in the rainforest of the Scenic Rim in south east Queensland.

Turn your volume right up, we decided on the fly to just have a crack and shoot this one late Sunday night in the rain, so it’s a bit quiet (and dark) at times. Watch out for the next one, coming soon, cause we’ll be a little more prepared!

Cheers,
Julian