DNA: How it’s helping scientists understand species adaptation to climate change
How species respond to climate change could well determine their chances of survival. A new paper describes how scientists are finding new ways to understand how plants and creatures adapt to climate change – by digging deep into their DNA.
The methods are allowing scientists to measure responses to climate change at a greater scale than ever before, the study’s lead author tells Carbon Brief.
DNA sequencing
DNA holds all the genetic information that controls how an organism will develop and function. In humans, it dictates physical traits such as height and eye colour.
DNA sequencing is the way scientists identify which genes control particular traits in a species. But as organisms may have millions or billions of pieces of DNA, sequencing can be a lengthy process.
The new paper, published in BioScience journal, describes how a technology called ‘next-generation DNA sequencing’ (NGS) allows scientists to analyse millions of pieces of DNA at the same time. This dramatically reduces how much time and money sequencing takes, the paper says.
Lead author, Prof Jonathon Stillman, uses an analogy of analysing a haystack to describe NGS. Using traditional methods you would need to pick out a few straws and use those to try understand the whole haystack, he says, but with NGS you can look at every straw of hay individually.
Move, adapt or die
So what are scientists doing with all this genetic information?
There are three ways a species can respond to changing conditions: move, adapt or die. While it is relatively easy to measure if a species is dying out, monitoring how it moves or adapts is more difficult. This is because scientists need to be able to study how its DNA or physical characteristics are changing.
Scientists use the data they gather from NGS to see where species migrate and which physical traits they’re developing to survive. One study, for example, uses NGS to track how the habitat of three species of giant clams expanded as sea levels rose after the last ice age. And a study also published this week shows how polar bears have gradually migrated north in search of more year-round sea ice.
There’s more than one way that a species can adapt, the study says, and NGS can help with both.
Types of adaptation
Species can adapt to changing conditions by ‘local adaptation’ or alternatively through what’s known as ‘plasticity’. Stillman explains to Carbon Brief:
“Local adaptation is fixed genetic differences among individuals from one site to the next. For example, fish living in one lake may be the same species as fish in another lake, but they may have their own characteristics that increase their fitness in each lake. Plasticity is the ability for organisms to respond to climate change without any genetic changes.”
So with local adaptation, scientists expect to see differences between the DNA of the same species that make it suitable, or fit, for the conditions that the creature or plant lives in. For example, a study of a flowering plant called thale cress shows that it has evolved to grow in both Sweden and Italy, despite very different climates.
With plasticity, a species might show different characteristics depending on their surroundings, but their DNA would be the same. For example, a study of porcelain crabs, reported by Carbon Brief last year, shows that in warmer, more acidic ocean conditions the crabs put a greater proportion of energy into the basic functions of living and breathing, leaving less for anything else.
Temperature the central focus
The paper finds a rapid increase in the number of research articles about NGS and climate change in recent years. As the graph below shows, the majority of studies look at how species respond to rising temperatures. This is because temperature is the most dominant climate driver that affects plants and creatures, Stillman says.
Image - Stillman & Armstrong (2015) Fig 1 DNA Sequencing (note)
Number of research articles on NGS and climate per year, by type of climate driver. Source: Stillman & Armstrong ( 2015).
But analysing how species adapt to other climate and environmental pressures can also involve NGS. Stillman concludes:
“Other drivers such as water availability, salinity, environmental chemistry, and others are also important, but temperature will probably always remain a central focus.”