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rather.than.to.higher.latitudes,.and.such.changes.to.distributions.would.again.not.be.
detected.by.coarse-scale.data.(Hill.et.al..2002)..Furthermore,.attributing.observed.
declines.to.climate.change.is.dificult.in.the.many.landscapes.where.intensive.human.
land.use.represents.an.additional.threat.to.species,.particularly.at.lower.elevations.
(Thomas.et.al..2006).
In.the.last.ive.years,.however,.an.increasing.number.of.uphill.range.shifts.have.
been.identiied,.often.driven.by.local.extinctions.at.the.downslope.limits.of.species.
distributions,.and.at.faster.rates.than.suggested.by.earlier.meta-analyses..Here,.we.
describe.the.approaches.that.have.been.used.to.detect.such.range.shifts,.focusing.on.
evidence.from.the.apparent.breeding.ranges.of.species,.rather.than.temporary.migra-
tory.movements..Thus,.we.interpret.the.range.shifts.as.changes.to.the.distribution.of.
populations.of.species,.relecting.local.extinctions.in.zones.of.range.contraction.and.
colonizations.in.zones.of.range.expansion.
REPORTED ELEVATIONAL SHIFTS IN SPECIES DISTRIBUTIONS
Evidence. now. exists. that. plants,. invertebrates,. and. ectothermic. and. endothermic.
vertebrates.have.shifted.to.higher.elevations.associated.with.recent.climate.warming.
in.tropical,.temperate,.and.polar.latitudes.(TablesĀ 6.1.and.6.2)..Four.types.of.evidence.
have.been.presented.for.uphill.range.shifts.
.
1.. Average elevation of species distributions. .The.average.elevation.of.a.spe-
cies'.range.could.shift.upward.because.of.extinctions.at.low.elevations.or.
colonizations.at.high.elevations,.either.at.the.margins.of.or.within.the.spe-
cies'.range..Different.types.of.data.lend.themselves.to.different.methods.for.
estimating. average. elevation.. Studies. using. atlas. data. have. calculated. the.
mean. elevation. of. grid. squares. with. distribution. records. in. repeated. sur-
veys.(Hill.et.al..2002;.Konvicka.et.al..2003;.Hickling.et.al..2006)..Repeat.
sampling. along. the. same. elevation. gradients. can. be. used. to. calculate. the.
midpoint. of. a. species'. range. (Raxworthy. et. al.. 2008),. although. such. an.
approach. is. not. sensitive. to. changes. in. abundance. or. occupancy. between.
upper.and.lower.limits.(Shoo.et.al..2005a,.2005b)..Alternatively,.the.mean.
elevation.weighted.by.the.abundance.or.cover.of.species.may.be.an.appro-
priate.technique.for.discrete.sampling.elevations,.even.when.relatively.few.
(5-20).locations.have.been.sampled.(Kelly.and.Goulden.2008;.Chen.et.al..
2009)..When.many.sites.are.sampled,.optimum.elevations.with.the.highest.
probability. of. occurrence. for. species. can. be. modelled. based. on. presence.
and.absence.records;.such.models.can.be.applied.to.repeat.surveys.in.the.
same.region.(Wilson.et.al..2005).or.to.national-scale.site-based.data.sliced.
into.discrete.time.periods.(Lenoir.et.al..2008).
.
. Reported.uphill.shifts.in.the.average.or.optimum.elevations.of.species.
distributions.are.rather.consistent.among.taxa.and.regions..European.stud-
ies. based. on. atlas. data. report. absolute. uphill. shifts. (averaged. across. spe-
cies).of.20-60.m.over.the.25-30.years.at.the.end.of.the.twentieth.century,.
using.data.for.butterlies.(Hill.et.al..2002;.Konvicka.et.al..2003).and.a.wide.
range. of. ectothermic. groups. (arthropods. and. ish;. Hickling. et. al.. 2006)..
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