How to

12 May 2017

Rising Temperatures Negatively Affect Microbiomes in Common Lizards, Study Confirms

It’s well-known and accepted by most rational-minded people that global warming is very real and will have some profound and highly damaging effects on the planet, its climates, and its ecosystems, if left to progress unchecked. Countless studies over the years have sought to highlight, understand, and combat these threats upon the world as we know it, examining factors ranging from sea ice levels, global average temperatures, and greenhouse gas emissions. Increasingly, these studies are beginning to look away from the mechanisms driving climate change, and more towards the consequences of current climate predictions on the various life forms which litter the planet. Polar Bears, Penguins and coral reefs have become the poster-boys of climatologists and campaign groups alike, as they seek a way to remedy the damage inflicted upon the Earth, but the effects of global warming extend to just about every living thing walking, swimming, crawling, or flying around our little blue planet.

Even bacterial life looks unlikely to avoid the far-reaching consequences of global warming, as confirmed by a recent study into the effects of rising temperatures on gut-microbial diversity in the Common Lizard. Granted, such bacteria isn’t quite as cute as the classic Polar Bear or Penguin and as such people don’t tend to care as much, but for the creatures hosting such microbiomes, the survival of this bacteria is crucial if they themselves are to last.

As lizards belong to the cold-blooded animal group known as ectotherms, which rely upon external heat sources to regulate their own temperature, the effects of climate change will likely have a much more substantial effect upon their bodies than it will upon ours or those of other warm-blooded species.

The study, conducted by a team from the University of Exeter and led by research fellow Elvire Bestion, consisted of a three-part experiment designed to ascertain the impact of climate on the lizard gut microbiome. Making use of the Metatron ecology station in Moulis, Southern France, the researchers were able to conduct their experiments in a semi-natural setting. The Metatron facility houses a system of 48 100-square-meter enclosures that include all the vegetation, insects, rocks, and other features you would expect in a real wild environment but, crucially, allows the scientists to control the temperature and other climatological aspects within the facility.

The first stage of the study, conducted in 2012, saw Bestion and her colleagues release three groups of Common Lizards into enclosures within the facility. The first group were enclosed under current local temperatures; the second group were kept at 2°C above this level (classified as ‘intermediate’); the third group were housed at 3°C above current local temperatures (classified as ‘warm’). During autumn and winter, all three were kept at current local temperatures.

The lizards’ cloacal microbiomes, often used as a proxy for the bacteria in the gut, were later sampled and examined in May 2013. These examinations revealed that the bacterial diversity of the lizards which summered at ‘warm’ temperatures was 34% lower than in those kept at current local temperatures.

In the second stage of the experiment, conducted in the summer of 2013, the research team sampled the lizards’ cloacal microbes both before and immediately after a two-month summer exposure to either current or ‘warm’ temperatures. Bacterial richness in both groups increased over the summer, but less so in those kept at higher temperatures. Bestion states that “this was mainly driven by extinction of individual bacterial taxa.”

In the third and final experiment, a subset of lizards from the first experiment was released into a common garden setting at current local temperatures for a full year in order to monitor their survival. It was found that the lizards which survived the year tended to be those which entered the environment with a richer microbiome, regardless of which enclosure within the Metatron they had come from. From this, the authors concluded that “loss of bacterial taxa might therefore have a negative impact on lizard survival.”

Two previous studies conducted in 2016, one focusing on tadpoles and the other on insects, further confirm the conclusion that temperature increases do in fact lead to microbiome changes within ectotherms. From here, the team hope to expand their research to examine the effects of a changing climate on other species, including endotherms. Study lead Elvire Bestion states, “There is clearly a pattern to be investigated, particularly in ectotherms… because of the direct link between air temperature in physiology in these animals, but I think even in endotherms, we should maybe think of investigating that to maybe better understand the consequences of climate change.”

Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.