Geoscience Reference
In-Depth Information
gradient,. differentiating. between. specialized,. less. dispersive. species. and. distur-
bance-associated.species..One.might.analyze.data.for.several.species.whose.ranges.
are.expected.to.expand.northward.and.several.whose.ranges.are.expected.to.contract.
rather.than.concentrating.only.on.species.for.which.northward.expansion.is.antici-
pated.(Wilson.et.al..2007).
At.the.species.level,.it.is.most.straightforward.to.track.species.that.are.not.highly.
constrained.by.patch.dynamics..Metapopulation.dynamics.across.habitat.patches.that.
vary.in.resource.availability.and.quality.obfuscate.signals.of.climate.change..Patches.
supporting. populations. with. a. relatively. high. probability. of. extirpation. likely. will.
disappear. long. before. manifestation. of. incremental. climate. change.. For. example,.
wide-ranging.Papilionids.and.Pierids.might.be.more.appropriate.for.study.than.well-
known.Nymphalids,.such.as.
Euphydryas
.and.other.Melitaea.
The. demographic,. spatial,. and. temporal. resolution. of. each. set. of. data. must. be.
appropriate.for.the.given.question..Data.on.abundance.or.population.dynamics.usu-
ally. are. more. informative. than. data. on. presence. or. absence,. but. more. sensitive. to.
potential.confounding.factors.such.as.short-term.weather.and.differences.in.observ-
ers..If.one.is.evaluating.whether.appearance.dates.in.a.particular.location.over.many.
years.have.changed,.then.an.estimate.of.regional.means.and.variance.in.temperature.
and.precipitation.derived.from.just.one.or.two.weather.stations.may.be.suficient..If.
one.instead.is.examining.asynchronous.emergences.within.a.region.in.one.or.more.
years,.then.ine-resolution.data.on.climatic.variables.likely.are.necessary.
Known.mechanisms.by.which.the.abiotic.environment.affects.butterlies.can.allow.
the.generation.of.speciic,.testable.predictions.related.to.climate.change.(Hellmann.
2002;.Parmesan.2003)..The.ideal.species.would.have.fairly.well-resolved.and.highly.
speciic.requirements.for.survival,.so.relatively.few.stressors.would.confound.inter-
pretation. of. responses. to. climate.. Most. extant. species. in. developed. countries. are.
resilient.to.moderate.levels.of.human.activity,.which.reduces.the.number.of.likely.
drivers.of.a.population.response.(Parmesan.2003)..Especially.when.species.already.
are.rare,.short-term.weather.events.that.may.not.be.causally.related.to.determinis-
tic.changes.in.climate.may.lead.to.extirpation.or.extinction..One.must.separate.the.
effects.of.deterministic.changes.in.climate.on,.for.example,.the.availability.of.larval.
host. plants. from. stochastic,. but. not. necessarily. surprising,. anomalies. in. weather..
Furthermore,. many. alternative. hypotheses. for. changes. in. distributional. range. or.
demographic. parameters,. such. as. parasitoids. or. invasion. of. non-native. species. of.
plants,.may.themselves.be.affected.by.changes.in.climate.
Data.from.long-term.butterly.monitoring.programs.in.the.United.Kingdom.and,.
to. a. lesser. extent,. other. European. countries. sparked. a. belief. among. scientists. and.
the.public.that.changes.in.climate.will.be.relected.in.the.distribution.and.popula-
tion. dynamics. of. butterlies. sooner. than. in. many. other. popular. taxonomic. groups.
(Fleishman.and.Murphy.2009)..Butterlies.indeed.respond.to.atmospheric.conditions.
both.physiologically.and.indirectly,.mediated.by.changes.in.sources.of.food.for.lar-
vae.and.adults,.interactions.with.parasites.and.other.predators,.and.habitat.structure..
However,. robust. data. and. biological. understanding. are. critical. to. discriminating.
between.signal.and.noise.and.to.validating.mechanistic.hypotheses..Projected.range.
shifts.and.regional.extirpations.of.butterlies.that.are.based.on.simple.assumptions.
about.habitat.quality.and.relationships.among.land.cover,.latitude,.and.elevation.well.
