Geoscience Reference
In-Depth Information
varied.as.a.function.of.ambient.temperature..In.this.case,.the.range.of.slope.expo-
sures.and.other.conditions.suitable.for.oviposition.increased.as.regional.temperature.
increased. (Davies. et. al.. 2006).. The. frequency. and. magnitude. of. extreme. climatic.
events.is.likely.to.increase.as.climate.changes,.and.extreme.events.can.precipitate.
sudden.shifts.in.vegetation.structure..Singer.and.Thomas.(1996).demonstrated.evo-
lutionary.responses.by.a.metapopulation.of.
Euphydryas editha
.to.changes.in.relative.
abundance.of.different.larval.hosts.that.were.driven.by.human.activity.and.intense.
climatic.events.(Singer.and.Thomas.1996).
In.some.cases,.geographic.ranges.of.butterlies.have.shifted.rather.than.expanded..
Parmesan.et.al..(1999).found.that.the.ranges.of.63%.of.35.nonmigratory.European.
butterlies.shifted.to.the.north.by.35-240.km.during.the.1900s..Not.only.latitudinal.
but. elevational. range. shifts. have. been. observed.. As. mean. annual. temperature. in.
central. Spain. rose. by. 1.3°C. over. 30. years,. the. mean. lower. elevational. limit. of. 16.
species.of.butterlies.increased.by.212.m.(Wilson.et.al..2005)..Hill.et.al..(2002).did.
not.detect.a.systematic.northward.shift.in.the.ranges.of.51.species.of.butterlies.in.
Britain.during.the.1900s..However,.the.distribution.of.species.that.occupied.northern.
or.montane.areas.tended.to.shift.to.higher.elevations.(Franco.et.al..2006).
A. small. number. of. studies. have. emphasized. relationships. between. population.
dynamics.of.butterlies.and.patterns.of.precipitation..Fluctuations.in.abundance.of.two.
populations.of.
E. editha
,.the.mechanism.that.ultimately.led.to.extirpations,.appear.
to.have.been.exacerbated.by.increasing.variability.in.precipitation.(McLauglin.et.al..
2002)..Since.1978,.abundances.of.28.of.31.species.of.British.butterlies.have.been.
correlated.positively.with.low.precipitation.in.the.current.year.and.high.precipitation.
in.the.previous.year,.as.well.as.with.warm.temperatures.during.summer.of.the.cur-
rent.year.(Roy.et.al..2001)..In.general,.since.the.mid-1800s,.abundance.of.British.but-
terlies.tended.to.increase.when.summers.were.warm.and.dry.and.to.decrease.when.
summers.and.winters.were.wet.and.winters.were.warm.(Dennis.and.Sparks.2007)..
These.observations.are.not.necessarily.linked.to.climate.change,.although.changes.
in.the.amount,.timing,.and.variability.of.precipitation.are.consistent.with.projections.
of.climate.change.
DRAWING RELIABLE INFERENCE FROM BUTTERFLIES
It. is. reasonable. to. assume. that. occurrence. and. population. dynamics. of. butterlies.
relect.changes.in.climate,.but.tracking.that.response.is.confounded.by.noise.intro-
duced.by.responsiveness.to.weather..In.many.instances,.the.population.dynamics.of.
butterlies.actually.may.be.so.responsive.to.minor.variations.in.ecological.conditions.
that.they.may.not.serve.as.signals.of.meaningful.environmental.trends..Interpretation.
of.responses.of.population.dynamics.of.butterlies.also.is.confounded.by.a.general.
misconception. that. butterlies. can. provide. more-general. information. on. myriad.
environmental.variables.and.trends.(Fleishman.and.Murphy.2009).
Many. apparent. associations. between. butterlies. and. weather. or. climate. are.
mediated. through. the. structure. or. composition. of. vegetation,. rather. than. directly.
by.climate..There.is.concern.that.differences.in.the.phenological.responses.of.but-
terlies. and. their. larval. host. plants. to. changes. in. climate. may. lead. to. declines. in.
abundance.or.distribution..However,.evidence.suggests.that.these.relationships.may.
