BBC Wildlife - UK (2020-05)

appliedearlier,maybetheseinvaderscould

havebeencontrolledbeforetheytookover.

Howthepastinformsthefuture

DNAtracescanalsohelpuslookback

intime.Ina 2016studythatanalysed

ancientDNA,scientistsfoundthatwoolly

mammothsonthesmallAlaskanisland

ofStPaulwerestillaliveuntil5,600years

ago– almost2,000yearsafterthedatethat

hadbeenestimatedusingbones.It was

previouslynotknownforsurewhythese

giantsdiedout– theyweren’thuntedonthe

island,andtheclimatewasrelativelystable

duringtheperiodtheywerethoughtto

havegoneextinct.Thenewdatetiedinwith

whendrinkingwaterbecamesalty,sothe

mammothsprobablydiedfromthirst.

1

eDNAcanbecollected

fromanyenvironmental

sample,suchassoil,

sedimentorwater(left).

Whenworkingwithwater,

samplesmaybecollected

inbags,bottlesorbuckets.

2

A syringemaybeused

topusha sampleofthe

collectedwaterthrougha

filter.Thefiltercollectsthe

DNA,andis sentotothe

labforanalysis(left/below).

3

Inthelab,theDNAis

isolatedusinga series

ofsteps,startingwith

breakingopenthecellsto

releasetheDNA.Attheend

oftheprocess,theDNAis

ina tubeonitsown.

4

A singlewatersample

cancontainmillionsof

DNAsequences.WitheDNA

sampling,youareusually

lookingforsomething

specific.So,a relevant

‘primer’isusedtoamplify

theDNAinquestion– for

instance,anamphibian

primer,if lookingfor

frogs.Eventually,you

havelotsofcopiesof

theparticularDNA

you’reafter.

5

Theamplified

eDNAisthen

sequencedandis

matchedwithknown

DNAprofilesfrom

animalsthatare

alreadyonfile.

Scientistsfound

thatmammothson

theislandofStPaul

werestillaliveuntil

5,600yearsago.

eDNA

samp

ng

x4:

Mo

yCzachur

for

NatureMetr

cs

JHENIOSMAN

isa science

journalistand

author.Shepresents

onBBCRadio4’s

environmental

seriesCosting

theEarth.

“Themassive

potentialof

sedimentaryancient

DNA– fromlakes,caves

andotherenvironments

• is thereconstruction
  ofentirebiological
  communitiesover
  thepasttensor
  evenhundredsof
  millennia,”saysPeter
  Heintzman,from
  TheArcticUniversity
  ofNorway.“Thiscould
  tellus,withhighprecision,
  whenspeciesmovedintoor
  disappearedfromregionsand
  howthisrelatestopastchangesin

climate,whichtogethercouldbeused

topredicttheresponsesofbiological

communitiestotheclimatechangethat

is currentlyunderway.”

What’sthecatch?

eDNAanalysisdoeshavesome

limitations.Extractionandprofiling

is onlypossibleinthelab.Andthe

techniquecanonlyidentifyif a species

is present– it can’ttellexactnumbers

orwhethertheanimalis anadultora

juvenile.Butthebenefitsoutweighthe

limitations.Samplesofspeciesatany

lifestageandeveninverylownumbers

canbecollectedanytime,anywhere

andbyanyone,andcanprovidehuge

amountsofdatathathaven’tpreviously

existedforbiodiversity.

“Inthecaseofclimatechange,youcan

measureemissionsandcarbondioxide

levels,whichallowsyoutosettargets,

measureprogressandreportit.We’ve

neverhadthatwithbiodiversity,”saysKat

Bruce.“Thestoryis reallybleak,we’re

inthemiddleofa massextinctionevent.

Justbeingabletoaccuratelygenerate

large-scale,high-resolutiondatawill

helptoaddressthis.”

Katis notalone.Expertsaround

theworldareincrediblyenthusiastic

aboutthehugepotentialof

eDNAanalysis.Whileit won’t

completelyreplacetraditional

samplingmethods,if usedin

conjunctionwiththem,eDNA

lookssettoempoweruswith

a wealthofdatatoprotect

thisplanetfromthecurrent

environmentalonslaught.

May 2020 BBC Wildlife 35

NEWS FEATURE

eDNA: HOW IT WORKS