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 sento tothe
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