Evolutionary Significant Units (ESUs) Management … · Evolutionary Significant Units (ESUs)...

Evolutionary Significant Units (ESUs)Evolutionary Significant Units (ESUs)&&

Management Units (MUs)Management Units (MUs)

•• Defining Management Units Within SpeciesDefining Management Units Within Species

•• Diversity is Diverse and ComplexDiversity is Diverse and Complex

•• GGenetic enetic Distinctiveness & ESU’s definitionDistinctiveness & ESU’s definition

•• Measuring & ManagingMeasuring & Managing Genetic DiversityGenetic Diversity

•• Genetic Variability within PopulationsGenetic Variability within Populations

•• Defining evolutionary conservation value ofDefining evolutionary conservation value of populations or areaspopulations or areas

•• SummarySummary

Evolutionary Significant (ESUs)Evolutionary Significant (ESUs)MManagement Unitsanagement Units ((MUs)MUs)

Lecture OutlineLecture OutlineLecture Outline

•• Evolutionary Significant Units (ESUs)Evolutionary Significant Units (ESUs)

•• Molecular EcologyMolecular Ecology

•• IIdentification of dentification of eevolutionaryvolutionary distinct populationsdistinct populations

•• Genetical & Ecological ExchangeabilityGenetical & Ecological Exchangeability

Difficulties of defining a species can be very informative becauDifficulties of defining a species can be very informative because se it forces us to address organismal behaviour in an evolutionary it forces us to address organismal behaviour in an evolutionary and ecological contextand ecological context

Diversity is Diverse and Complex!Diversity is Diverse and Complex!

[[Evolutionary Significant Evolutionary Significant & M& Management Units]anagement Units]

Conservation genetics is about more than endangered speciesConservation genetics is about more than endangered species

•• it includes understanding theit includes understanding the relationships and diversityrelationships and diversity which which represent biodiversityrepresent biodiversity

•• need not (directly) be an applied science, but need not (directly) be an applied science, but can address issues can address issues relating to understanding diversityrelating to understanding diversity

•• maymay assist planning viable conservation strategiesassist planning viable conservation strategies more than more than conserving directlyconserving directly



Should we be conservingShould we be conserving speciesspecies??

Species onlySpecies only is a veryis a very simplisticsimplistic approach in the real worldapproach in the real world

•• is diversity only the number of species present?is diversity only the number of species present?

•• are all species equally relevant for biodiversity?are all species equally relevant for biodiversity?

•• must biodiversity be determined entirely by our species definitimust biodiversity be determined entirely by our species definition?on?



If not, then what else do we need to know?If not, then what else do we need to know?

What questions are really of interest?What questions are really of interest?

•• what (genetic) diversity is present within our taxon of interestwhat (genetic) diversity is present within our taxon of interest??

•• what diversity is present within a region?what diversity is present within a region?

•• what does this tell us about the important processes for creatinwhat does this tell us about the important processes for creating and g and maintaining diversity?maintaining diversity?

•• can we predict the consequences of a particular diversity level?can we predict the consequences of a particular diversity level?

•• if so, what is the appropriate response?if so, what is the appropriate response?

•• what/where should we be saving? what/where should we be saving?

•• can we have objective criteria for prioritization?can we have objective criteria for prioritization?

•• is is human activityhuman activity reducing diversity or is it a natural process?reducing diversity or is it a natural process?

•• is is genetic pollutiongenetic pollution a risk of human movements and introductions?a risk of human movements and introductions?



More difficult and controversial than defining speciesMore difficult and controversial than defining species

Species clearly require management as separate units, butSpecies clearly require management as separate units, but

•• somesome populationspopulations within species maywithin species may

•• be onbe on the path to speciationthe path to speciation andand

•• showshow significant adaptive differentiationsignificant adaptive differentiation to particular to particular ecological niches orecological niches or

•• significant genetic differentiationsignificant genetic differentiation

justifying theirjustifying their management as separate evolutionary management as separate evolutionary lineageslineages for conservation purposesfor conservation purposes

Defining Managment Units Within SpeciesDefining Managment Units Within Species


Evolutionary Significant Units (ESUsEvolutionary Significant Units (ESUs))

genetically differentiated populations that have a high genetically differentiated populations that have a high priority for separate management and conservationpriority for separate management and conservation

closely related (sometime synonymous) toclosely related (sometime synonymous) to

•• subspeciessubspecies

•• distinct population segments (DPS distinct population segments (DPS -- Endangered Species Act)Endangered Species Act)

many authors suggest that ESUs, subspecies and DPS all merit sepmany authors suggest that ESUs, subspecies and DPS all merit separate arate management and have amanagement and have a high priority for conservationhigh priority for conservation

the fundamental idea is thatthe fundamental idea is that conservation should aim to preserveconservation should aim to preserve

•• evolutionary processesevolutionary processes

•• adaptive potentialadaptive potential

•• not just current speciesnot just current species

without regard to losing significant variation within specieswithout regard to losing significant variation within species



What defines an ESU?What defines an ESU?

Original ESU's definitionsOriginal ESU's definitions (Ryder, 1986; Waples, 1991)(Ryder, 1986; Waples, 1991) had two componentshad two components

•• reproductive isolationreproductive isolation (and consequently, genetic distinctness)(and consequently, genetic distinctness)

•• ecological distinctnessecological distinctness (unique adaptations)(unique adaptations)

Recent definitions emphasize more genetic distinctivenessRecent definitions emphasize more genetic distinctiveness



RationaleRationale

Although genetics has assumed an important roleAlthough genetics has assumed an important role in conservation in conservation biologybiology

•• genetic surveys ofgenetic surveys of managed species are far from routine managed species are far from routine

•• therethere is a perception that genetic analyses are of moreis a perception that genetic analyses are of more significance significance to longto long--term than shortterm than short--term needsterm needs

•• genetic genetic analysis has analysis has lower priority than demographiclower priority than demographic analysisanalysis

MoritzMoritz

•• ttheory and practice heory and practice are are so far apartso far apart because the relevancebecause the relevance of of genetic analyses to practical issues ingenetic analyses to practical issues in wildlife management have not wildlife management have not been adequatelybeen adequately explained and demonstratedexplained and demonstrated

•• genetic markers (mtDNA and microsatellites) should be used to genetic markers (mtDNA and microsatellites) should be used to define management units within speciesdefine management units within species

GGenetic enetic DistinctivenessDistinctiveness & ESU’s definition& ESU’s definition


Moritz's definitionMoritz's definition

ESU’s should showESU’s should show

•• significant divergencesignificant divergence and and reciprocal monophylyreciprocal monophyly for mtDNAfor mtDNA

•• significant divergence of allele frequencies at nuclear locisignificant divergence of allele frequencies at nuclear loci

Moritz's Moritz's ESU’s ESU’s definition definition impliesimplies

•• bothboth historicalhistorical andand recent restriction ofrecent restriction of gene flowgene flow

it makes criteria for genetic it makes criteria for genetic distinctiveness more concretedistinctiveness more concrete

•• evidence forevidence for long term divergencelong term divergence, , continuingcontinuing in the presentin the present

divergencedivergence in mtDNA reflectsin mtDNA reflects long term restriction of gene flowlong term restriction of gene flow

congruence of slow and fast markerscongruence of slow and fast markers (microsatellites) (microsatellites) is is evidence for historical isolation thatevidence for historical isolation that persists todaypersists today



Reciprocal MonophylyReciprocal Monophyly

each ESU is a monphyletic groupeach ESU is a monphyletic group (ancestral population and all (ancestral population and all descendant populations) that does not include any portion of thedescendant populations) that does not include any portion of the otherother



ESU 1ESU 1 ESU 2ESU 2

mtDNA is a powerful tool in evolutionary biologmtDNA is a powerful tool in evolutionary biologyy

•• rapid rate of base substitutionsrapid rate of base substitutions

•• effectivelyeffectively haploidhaploid

•• maternal inheritancematernal inheritance

reduces reduces NNee

increases sensitivity toincreases sensitivity to genetic driftgenetic drift

•• ease of isolation and manipulationease of isolation and manipulation

mtDNA can producemtDNA can produce results of considerableresults of considerablepracticpracticaal importancel importance, but , but

•• the conservation goalsthe conservation goals must be clearly must be clearly defined first and the analysesdefined first and the analysesdesigned to fit the goalsdesigned to fit the goals



Critics to the ESU conceptCritics to the ESU concept

•• evolutionary significant units areevolutionary significant units are essentially equivalent to, and essentially equivalent to, and should be abandoned in favour of, should be abandoned in favour of, phylogenetic speciesphylogenetic species

(Cracraft, 1997)(Cracraft, 1997)

•• genetically defined ESUs ignore adaptive differencesgenetically defined ESUs ignore adaptive differences(Crandall et al., 2000)(Crandall et al., 2000)

•• unlikely detectedunlikely detected within species within species with high gene flowwith high gene flow

even though populations may have adaptive differences even though populations may have adaptive differences and warrant separate managementand warrant separate management

•• populations populations with low gene flowwith low gene flow that have been differentiated that have been differentiated by genetic drift may be designated as seprate ESUs by genetic drift may be designated as seprate ESUs

even even though they may not be adaptively distinctthough they may not be adaptively distinct

Genetical & Ecological ExchangeabilityGenetical & Ecological Exchangeability


Critics to the ESU concept Critics to the ESU concept (Crandall et al., 2000)(Crandall et al., 2000)

TThehe reciprocal monophyly criterion reciprocal monophyly criterion may bemay be overly strictoverly strict

•• guaranteesguarantees that that historical restriction of gene flowhistorical restriction of gene flow occurredoccurred

•• ecologically important genetic differences ecologically important genetic differences may havemay haveaccumulated without thisaccumulated without this pattern pattern

•• cconversely, onversely, long accumulation of neutral genetic long accumulation of neutral genetic differences differences may result inmay result in littlelittle ecological divergenceecological divergence

If the goal is If the goal is to maintain adaptive potentialto maintain adaptive potential, need to , need to

•• consider these possibilitiesconsider these possibilities

•• restorerestore focus on adaptations, not just neutral genetic variationfocus on adaptations, not just neutral genetic variation



CrossCross--hair Analysis hair Analysis (Crandall et al., 2000)(Crandall et al., 2000)

Populations can be classified according to whether they show Populations can be classified according to whether they show recent or historical ecological or genetic exchangeabilityrecent or historical ecological or genetic exchangeability

CrossCross--hair analysis hair analysis attempts to delineate whether there isattempts to delineate whether there is

•• there isthere is adaptive differentiation adaptive differentiation

•• there isthere is gene flowgene flow

•• historicalhistorical

•• due to recent admixturedue to recent admixture

CrossCross--hair analysis hair analysis leads toleads to

•• more adequate management recommendationsmore adequate management recommendations




Populations are given Populations are given ++ or or -- classificationsclassifications



EcologicalEcologicalGeneticGenetic

++//--++//--HistoricalHistorical

Time FrameTime Frame

RecentRecent

HH00 ExchangeabilityExchangeability

++//--++//--

++ reject reject HH00 of exchangeabilityof exchangeability, evidence exists for divergence, evidence exists for divergence

-- accept accept HH00 of exchangeabilityof exchangeability, failure to detect divergence, failure to detect divergence


Genetic ExchangeabilityGenetic Exchangeability

•• concerned with theconcerned with the limits of spread of new genetic variation limits of spread of new genetic variation through gene flowthrough gene flow

rejected (rejected (++)) when there is when there is evidence evidence ofof restricted gene flowrestricted gene flow

accepted (accepted (--)) when there is when there is evidence evidence ofof ample gene flow ample gene flow

•• evidence for gene flow is ideally evidence for gene flow is ideally based on multiple nuclear loci based on multiple nuclear loci but also on mtDNA or cpDNAbut also on mtDNA or cpDNA






RecentRecent


++//--++//--


Ecological ExchangeabilityEcological Exchangeability

•• based on the factors that define thebased on the factors that define the

•• fundamental fundamental nicheniche

•• the the spread ofspread of new genetic variantsnew genetic variants through genetic drift through genetic drift or natural selectionor natural selection






RecentRecent


++//--++//--


Ecological ExchangeabilityEcological Exchangeability

rejected (rejected (++)) when there is when there is evidence evidence for population differentiation for population differentiation due to due to genetic drift or natural selectiongenetic drift or natural selection

features interpreted as reflectingfeatures interpreted as reflecting adaptive differentiationadaptive differentiation

•• life history traitslife history traits•• morphologymorphology•• habitathabitat•• QTL traits under selectionQTL traits under selection




++++//--HistoricalHistorical


RecentRecent


++++//--


Recent and historical time frames Recent and historical time frames distinguishdistinguish

•• natural evolutionary processes of limited gene flownatural evolutionary processes of limited gene flowHH00 rejected (rejected (++) ) in thein the historicalhistorical--genetic categorygenetic category




++//--++HistoricalHistorical


RecentRecent


++//--++//--


Recent and historical time frames Recent and historical time frames distinguishdistinguish

•• natural evolutionary processes of limited gene flownatural evolutionary processes of limited gene flowHH00 rejected (rejected (++) ) in thein the historicalhistorical--genetic categorygenetic category

formform•• recent population isolationrecent population isolation

++ in thein the recentrecent--genetic categorygenetic category






RecentRecent


++//--++


Recent and historical time frames Recent and historical time frames distinguish alsodistinguish also

•• secondary contactsecondary contactHH00 accepted (accepted (--)) in thein the recentrecent--genetic categorygenetic category






RecentRecent


++//----


Recent and historical time frames Recent and historical time frames distinguish alsodistinguish also

•• secondary contact secondary contact HH00 accepted (accepted (--) ) in thein the recentrecent--genetic categorygenetic category

formform•• long termlong term--gene flowgene flow

HH00 accepted (accepted (--)) in thein the historicalhistorical--genetic categorygenetic category




++//----HistoricalHistorical


RecentRecent


++//--++//--


•• 16 categories of divergence 16 categories of divergence between two populationsbetween two populations

•• recommended management actionsrecommended management actions are given for are given for 8 categories8 categories•• strong emphasis on top right quadrantstrong emphasis on top right quadrant






RecentRecent


++//--++//--




separate speciesseparate species


++++HistoricalHistorical

RecentRecent ++++

++--

++++

--++

++++treat as separate speciestreat as separate species






RecentRecent ++-- treat as distinct populationstreat as distinct populations•• recent admixturerecent admixture•• loss of genetic disctinctivenessloss of genetic disctinctiveness



RecentRecent --++

treat as single populationtreat as single population•• if natural convergence on if natural convergence on

ecological exchangeabilityecological exchangeabilitytreat as distinct populationtreat as distinct population

•• if if anthropogenic convergence anthropogenic convergence

Diceros bicornisDiceros bicornis

Assignment examples Assignment examples –– Black RhinocerosBlack Rhinoceros

O’Ryan et al. (1994) used mtDNA to argue for two subspecies withO’Ryan et al. (1994) used mtDNA to argue for two subspecies withseparate managementseparate management

CrossCross--hair Analysis hair Analysis

•• insufficient grounds to reject either genetic or insufficient grounds to reject either genetic or ecological exchangeabilityecological exchangeability

•• populations showpopulations show gene flowgene flow

•• habitats are similarhabitats are similar




----HistoricalHistorical

RecentRecent ----

The species should beThe species should be managed as a single populationmanaged as a single population

Assignment examples Assignment examples –– African ElephantAfrican Elephant

Georgiadis et al. (1994) found a Georgiadis et al. (1994) found a reciprocal monophyetic reciprocal monophyetic relationship among mtDNA relationship among mtDNA

•• authors argued that the genetic diversity was simply authors argued that the genetic diversity was simply isolation isolation by distance due to driftby distance due to drift across their geographic rangeacross their geographic range

•• habitat of different populations is suffifiently similar to habitat of different populations is suffifiently similar to acceptacceptecological exchangeabilityecological exchangeability





RecentRecent --++

The species should beThe species should be managed as a single populationmanaged as a single population

Loxodonta africanaLoxodonta africana

Assignment examples Assignment examples –– Cryan’s BuckmothCryan’s Buckmoth

Legge et al. (1996)Legge et al. (1996)

•• adequate gene flow adequate gene flow •• no evidence to reject no evidence to reject geneticgenetic exchangeabilityexchangeability based based

on either mtDNA or allozymes on either mtDNA or allozymes

•• evidence to reject recentevidence to reject recent but not historical but not historical ecological ecological exchangeabilityexchangeability between populationsbetween populations

•• adaptive significance of the ecological differentiationadaptive significance of the ecological differentiation





RecentRecent ++--

The species should beThe species should be managed as distinct populations managed as distinct populations although although gene flow consistent with current population structure is allowagene flow consistent with current population structure is allowableble

Hemileuca sp.Hemileuca sp.

Assignment examples Assignment examples –– Puritan Tiger BeetlePuritan Tiger Beetle

•• mtDNAmtDNA show show low genelow gene flow and flow and significant differentiationsignificant differentiation

•• evidence to reject evidence to reject geneticgenetic exchangeabilityexchangeability

•• not not ecological exchangeableecological exchangeable based on habitat parametersbased on habitat parameters




--++HistoricalHistorical

RecentRecent ++++

•• strong adaptive differentiationstrong adaptive differentiation

•• recommendation torecommendation to manage manage the two populationsthe two populations as separate as separate units for conservation purposesunits for conservation purposes

Cicindela puritanaCicindela puritana

It is important to distinguish betweenIt is important to distinguish between

1.1. Gene ConservationGene Conservation

•• the use of genetic information to measure and manage the use of genetic information to measure and manage geneticgenetic diversity for its own sakediversity for its own sake

2.2. Molecular EcologyMolecular Ecology

•• genetic analyses as agenetic analyses as a complement to ecological studies of complement to ecological studies of demographydemography

•• moremore straight forwardstraight forward

•• of more use to wildlifof more use to wildlife e managers faced with shortmanagers faced with short--term managementterm management prioritiespriorities

Conservation GoalsConservation Goals


MManaging genetic diversity isanaging genetic diversity is more relevant tomore relevant to

longlong--term planningterm planning

policypolicy

than to than to

shortshort--term management of threatenedterm management of threatened populations populations

few noticeable exceptionsfew noticeable exceptions (e.g.(e.g. translocationstranslocations ) )

Measuring & ManagingMeasuring & Managing Genetic DiversityGenetic Diversity


mtDNA has been used in this contextmtDNA has been used in this context toto

•• measure genetic variation within populationsmeasure genetic variation within populations,, especially especially ones thought to have declinedones thought to have declined recentlyrecently

•• iidentify evolutionary divergent sets ofdentify evolutionary divergent sets of populations, including populations, including thethe resolution ofresolution of ESUsESUs

•• assess conservation value of populations orassess conservation value of populations or areas from areas from an evolutionary or phylogenetican evolutionary or phylogenetic perspectivperspectivee



mtDNA has been used in this contextmtDNA has been used in this context toto

•• measure genetic variation within populationsmeasure genetic variation within populations,, especially especially ones thought to have declinedones thought to have declined recentlyrecently

oo iidentify evolutionary divergent sets ofdentify evolutionary divergent sets of populations, including populations, including the the resolution ofresolution of ESUsESUs

oo assess conservation value of populations orassess conservation value of populations or areas from areas from an evolutionary or phylogenetican evolutionary or phylogenetic perspectivperspectivee



Genetic Variability within PopulationsGenetic Variability within Populations

AAim of quantifying mtDNA variation withinim of quantifying mtDNA variation within populations populations

•• test for thetest for the loss of genomicloss of genomic variabilityvariability, , generallygenerally as a as a consequence of reductionconsequence of reduction in population sizein population size

conservation significance if the loss ofconservation significance if the loss of variation translates variation translates to reduced individual fitnessto reduced individual fitness

This is aThis is a weak application of mtDNAweak application of mtDNA

lacklack of any theoretical or empirical evidence for aof any theoretical or empirical evidence for a strongstrongcorrelation between mtDNA diversity andcorrelation between mtDNA diversity and diversity in the diversity in the nuclear genomenuclear genome

llow mtDNA diversity is correlated with lowow mtDNA diversity is correlated with low nuclear gene nuclear gene diversity is some case but not othersdiversity is some case but not others



Genetic Variability within PopulationsGenetic Variability within Populations

•• low mtDNA diversity has beenlow mtDNA diversity has been reported in rapidly expanding species reported in rapidly expanding species •• northern elephant seals northern elephant seals •• parthenogenetic gekosparthenogenetic gekos

•• moderate to high mtDNA diversity hasmoderate to high mtDNA diversity has been observed in declining been observed in declining species subjected to intense harvesting or in species otherwise species subjected to intense harvesting or in species otherwise suggestedsuggested to be inbredto be inbred

•• coconut crabscoconut crabs•• humpback whaleshumpback whales



Megaptera novaeangliaeMegaptera novaeangliae

Mirounga angustirostris Mirounga angustirostris

Birgus latroBirgus latro

mtDNA has been used mtDNA has been used toto

measure genetic variation within populationsmeasure genetic variation within populations,, especially especially ones thought to have declinedones thought to have declined recentlyrecently

•• iidentify evolutionary divergent sets ofdentify evolutionary divergent sets of populations, including populations, including thethe resolution ofresolution of ESUsESUs

oo assess conservation value of populations orassess conservation value of populations or areas from areas from an evolutionary or phylogenetican evolutionary or phylogenetic perspectivperspectivee



IIdentification of dentification of eevolutionaryvolutionary distinct populationsdistinct populations

IIdentification of dentification of taxataxa with independentwith independent evolutionary historiesevolutionary histories

•• pprerequisite for managing biodiversity rerequisite for managing biodiversity

•• groupings variously referred to as groupings variously referred to as

•• sspeciespecies

•• ssubspeciesubspecies

•• evolutionary significant units (ESUs)evolutionary significant units (ESUs)

mtDNA phylogeniesmtDNA phylogenies can can

•• provide unique insights intoprovide unique insights into population history population history

•• suggest hypotheses aboutsuggest hypotheses about the boundaries of genetically the boundaries of genetically divergent groups (i.e., cryptic species)divergent groups (i.e., cryptic species)



IIdentification of dentification of eevolutionaryvolutionary distinct populationsdistinct populations

•• mtDNA phylogeniesmtDNA phylogenies must be used in conjunction withmust be used in conjunction withnuclear markersnuclear markers because given thebecause given the

•• lower effective number of geneslower effective number of genes

•• greatergreater dispersal by malesdispersal by males than femalesthan females

mtDNA canmtDNA can diverge while nuclear genes do notdiverge while nuclear genes do not



Recognition of ESUsRecognition of ESUs

CCriteria for defining an ESU remainsriteria for defining an ESU remains to be establishedto be established

SSuggested thresholds rangeuggested thresholds range from from

•• any population that contributes substantiallyany population that contributes substantially to the overall genetic to the overall genetic diversity of the species anddiversity of the species and is reproductively isolatedis reproductively isolated

to to

•• populations showingpopulations showing phylogenetic distinctiveness of alleles acrossphylogenetic distinctiveness of alleles acrossmultiple locimultiple loci

The question that plagues the approach is The question that plagues the approach is

HowHow much difference is enough?much difference is enough?




HowHow much difference is enough?much difference is enough?

•• no theoretical or empirical justificationno theoretical or empirical justification for setting an for setting an amount of sequence divergenceamount of sequence divergence beyond which a set of beyond which a set of populations is recognized as an ESUpopulations is recognized as an ESU

AlthoughAlthough

•• comparisons to divergences withincomparisons to divergences within an among related species an among related species may provide an empiricalmay provide an empirical yardstickyardstick




QQualitative criterionualitative criterion

avoiding the quantitative question of avoiding the quantitative question of hhow much is enoughow much is enough??

•• to to considerconsider thethe geographic distribution of allelesgeographic distribution of alleles in relationshipin relationshipto theirto their phylogenyphylogeny

gene flow must be restricted for a long periodgene flow must be restricted for a long period to create to create phylogeographicphylogeographic structuring of allelesstructuring of alleles

ESUs shouldESUs should show complete monophyly of mtDNA allelesshow complete monophyly of mtDNA alleles

HoweverHowever

this criterion may bethis criterion may be totooo stringentstringent

well characterized species with paraphyleticwell characterized species with paraphyletic mtDNA mtDNA lineageslineages have been documentedhave been documented




Again…Again…

it is important to seekit is important to seek corroborating evidence from nuclear locicorroborating evidence from nuclear loci



HoweverHowever,, alleles of nuclear genesalleles of nuclear genes are expectedare expected

•• toto take substantially longer to show phylogenetictake substantially longer to show phylogenetic sortingsortingbetween populations or speciesbetween populations or species

larger effective population size larger effective population size

slowerslower neutral mutation rateneutral mutation rate


measure genetic variation within populationsmeasure genetic variation within populations,, especially especially ones thought to have declinedones thought to have declined recentlyrecently

iidentify evolutionary divergent sets ofdentify evolutionary divergent sets of populations, including populations, including the the resolution ofresolution of ESUsESUs

•• assess conservation value of populations orassess conservation value of populations or areas from areas from an evolutionary or phylogenetican evolutionary or phylogenetic perspectivperspectivee



Defining evolutionary conservation value ofDefining evolutionary conservation value of populations or areaspopulations or areas

EExtension of the use of mtDNA variation toxtension of the use of mtDNA variation to recognize ESUsrecognize ESUs

•• phylogenetic uniquenessphylogenetic uniqueness should be considered inshould be considered in prioritizing prioritizing species for management species for management

•• define conservationdefine conservation valuevalue taktakinging account of evolutionary account of evolutionary distance distance

particularly well suited to molecular dataparticularly well suited to molecular data




Then, mThen, movingoving from speciesfrom species toto communitycommunity geneticsgenetics

•• definedefine geographic regionsgeographic regions within whichwithin which multiple species have multiple species have genetically unique populationsgenetically unique populations oror ESUsESUs

•• testing fortesting for congruence ofcongruence of phylogeographic patterns among phylogeographic patterns among speciesspecies to defineto define geographic regions within which ageographic regions within which a substantial substantial proportion of species have had evolutionary historiesproportion of species have had evolutionary historiesseparateseparate from their respective conspecificsfrom their respective conspecifics

•• regions with a high proportion of ESUsregions with a high proportion of ESUs should be accordedshould be accordedhigh conservation priorityhigh conservation priority

•• even if they do not have an array of endemiceven if they do not have an array of endemic species as species as recognized by conventional methodsrecognized by conventional methods




‘‘ValueValue’’ skirtsskirts some basicsome basic philosophical and ethical issuesphilosophical and ethical issues……

•• ……wwhat do we mean by thehat do we mean by the SS in Ein ESSU?U?

•• …c…can we justifyan we justify ranking speciesranking species according to a measure of according to a measure of molecular divergence? molecular divergence?

•• wwe can only measure evolutionary significance ore can only measure evolutionary significance or value in terms of value in terms of past historypast history

•• wwe cannote cannot predict which, if any, of thesepredict which, if any, of these units will diversify to units will diversify to produce future biodiversityproduce future biodiversity

•• we must be very clear about the nature of the advice we are we must be very clear about the nature of the advice we are providing when weproviding when we discuss conservation priorities from a moleculardiscuss conservation priorities from a molecularevolutionary perspectiveevolutionary perspective……



GGeneral area of application eneral area of application that usesthat uses genetics as a tool for ecologistsgenetics as a tool for ecologists

•• to define the appropriate geographic scaleto define the appropriate geographic scale for monitoring for monitoring and managingand managing

•• to provide a means forto provide a means for identifying the originidentifying the origin of individuals in of individuals in migratory speciesmigratory species

•• to test forto test for dramatic changes in populationdramatic changes in population size and size and connectednessconnectedness

In general these applications areIn general these applications are

•• conceptuallyconceptually simpler simpler

•• much moremuch more relevant to shortrelevant to short--termterm management issuesmanagement issues

than are those related to genethan are those related to gene conservationconservation

Molecular EcologyMolecular Ecology


Defining Management UnitsDefining Management Units or stocksor stocks

SSimple but powerful and practical application ofimple but powerful and practical application of geneticsgenetics

•• aa great deal of effort is spent ongreat deal of effort is spent on monitoringmonitoring populations as part populations as part of the species recoveryof the species recovery processprocess

•• too often, little consideration istoo often, little consideration is given to thegiven to the appropriate appropriate geographic scale forgeographic scale for monitoring or managementmonitoring or management

•• aan exception is withn exception is with fisheriesfisheries, , where it has longwhere it has long been recognized been recognized thatthat species typically consist ofspecies typically consist of

•• multiple stocksmultiple stocks that respond independently tothat respond independently to harvesting and harvesting and managementmanagement

•• populations thatpopulations that exchange so few migrants as to be exchange so few migrants as to be geneticallygenetically distinct will also be demographically distinct will also be demographically independentindependent



Defining Management UnitsDefining Management Units or stocksor stocks

In contrast to ESUsIn contrast to ESUs

•• MUsMUs are defined byare defined by significantsignificant divergence in allele frequenciesdivergence in allele frequenciesregardless of theregardless of the phylogeny of the alleles phylogeny of the alleles

allele frequenciesallele frequencies will respond to population isolation more will respond to population isolation more rapidlyrapidly than phylogenetic patternsthan phylogenetic patterns

mtDNAmtDNA is especially useful for detectingis especially useful for detecting boundariesboundaries between Mbetween MUUss

•• differences betweendifferences between populations will be more readily populations will be more readily detected withdetected with mtDNAmtDNA than with nuclear genesthan with nuclear genes

importantimportant when sample sizes are limited aswhen sample sizes are limited as is often is often the case with threatened speciesthe case with threatened species

•• mtDNA mtDNA it is usuallyit is usually more prone tomore prone to genetic driftgenetic drift than nuclear than nuclear loci loci

aa greater proportion of the variation is distributedgreater proportion of the variation is distributedbetween populationsbetween populations



Identification & Use of Genetic TagsIdentification & Use of Genetic Tags

Useful applicationUseful application of genetics for shortof genetics for short--term managementterm management is tois to provide provide a source ofa source of naturally occurring naturally occurring

•• genetic tagsgenetic tags

genetic variantsgenetic variants that individually or in combination that individually or in combination diagnosediagnose different Mdifferent MUUss

•• iindeliblendelible

•• present in all memberspresent in all members of a population at all agesof a population at all ages

•• can becan be used to determine the source(s) of animalsused to determine the source(s) of animals in in

•• hharvestarvest

•• international commerceinternational commerce

•• areas subjected toareas subjected to impacts or managementimpacts or management



Identification & Use of Genetic TagsIdentification & Use of Genetic Tags

•• particularly useful forparticularly useful for migratorymigratory speciesspecies where where

impacts in one area (e.g., feedingimpacts in one area (e.g., feeding ground) can affect one or ground) can affect one or more distant MUsmore distant MUs

•• most effective where themost effective where the variation within areas is low relative to thatvariation within areas is low relative to thatbetween areasbetween areas

•• maximummaximum likelihood methodslikelihood methods can be used to estimate thecan be used to estimate thecontribution of various MUs to a samplecontribution of various MUs to a sample ofof individuals taken individuals taken from a particular from a particular •• feeding groundfeeding ground•• migratory routemigratory route•• commercial harvestcommercial harvest



MMigration and changigration and changeses in in population population sizesize

WWildlife managers ildlife managers often face the problem of often face the problem of assessing the degree to assessing the degree to which populations are which populations are

•• connected by migration connected by migration •• changing in sizechanging in size

PPatterns of genetic variationatterns of genetic variation provideprovide•• indirect estimates of indirect estimates of these parametersthese parameters

•• rapid developmentrapid development ofof methodsmethods for using information on for using information on alleleallele distributions and relationshipsdistributions and relationships to inferto infer

longlong--termterm migration ratesmigration ratestrends in trends in NNee

•• significant significant insightinsightss into theinto the longlong--termterm behavior of populationsbehavior of populations•• unclear relevance in unclear relevance in conservation studiesconservation studies ((shortshort--term term

managementmanagement) ) where populations are often fluctuating in where populations are often fluctuating in size and/orsize and/or connectednesconnectednesss



According to the According to the Evolutionary Significant Units (ESUs)Evolutionary Significant Units (ESUs) conceptconcept

•• genetically differentiated populations have a high priority for genetically differentiated populations have a high priority for separate management and conservationseparate management and conservation

•• ESU’s should showESU’s should show

•• significant divergence and significant divergence and reciprocal monophyly for mtDNA reciprocal monophyly for mtDNA allelesalleles

•• significant divergence of allele frequencies at nuclear locisignificant divergence of allele frequencies at nuclear loci


SummarySummarySummary

For the ecological and genetic exchangeability conceptFor the ecological and genetic exchangeability concept

•• populations within a species may justify management as populations within a species may justify management as separate units if they show adaptive genetic differentiationseparate units if they show adaptive genetic differentiation

•• delineation of such population requires information on their delineation of such population requires information on their recent or historical ecological or genetic exchangeabilityrecent or historical ecological or genetic exchangeability


•• measure genetic variation within populationsmeasure genetic variation within populations

•• iidentify evolutionary divergent sets ofdentify evolutionary divergent sets of populationspopulations

•• assess conservation value of populations orassess conservation value of populations or areas from an areas from an evolutionary or phylogeneticevolutionary or phylogenetic perspectivperspectivee


SummarySummarySummary

Evolutionary Significant Units (ESUs) Management … · Evolutionary Significant Units (ESUs)...

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