Geoscience Reference
In-Depth Information
depends.on.whether.current.conditions.lie.below,.at,.or.above.the.thermal.optimum.
for.a.species..Warmer.temperatures.in.August.have.led.to.increased.mass.and.greater.
reproductive.output.by.adult.female.Common.Lizard.
Lacerta vivipara
at.its.south-
ern.range.margin.in.France.(Chamaillé-Jammes.et.al..2006)..An.understanding.of.
the. genetic. and. physiological. mechanisms. underpinning. the. effects. of. climate. on.
fecundity. can. provide. valuable. information. on. the. capacity. of. species. to. adapt. to.
change.. For. example,. the. willow. beetle.
Chrysomela aeneicollis
. experienced. low-
elevation.extinctions.and.high-elevation.colonizations.at.its.southern.range.margin.
in.California.between.1998.and.2007..Genetic.polymorphism.at.the.phosphoglucose.
isomerase.(PGI).locus.is.associated.with.traits.that.confer.temperature.adaptation.in.
fecundity.in.this.species,.opening.up.the.possibility.to.research.the.population-level.
consequences.of.genetic.variation.in.a.changing.climate.(Dahlhoff.et.al..2008).
The.rates.at.which.species.extend.their.distributions.upward.depend.on.growth,.
fecundity,.and.survival.at.and.beyond.the.high-elevation.range.limit,.and.rates.of.dis-
persal.to.higher.elevations..In.plants,.seed-regenerating.species.may.face.relatively.
little. dispersal. limitation. over. elevation. gradients. (Molau. and. Larsson. 2000),. and.
may.therefore.track.suitable.conditions.faster.than.vegetatively.propagating.species.
(Kullman. 2002).. In. the. Alps,. species. with. lighter. diaspores. have. expanded. their.
distributions.more.quickly.uphill.(Parolo.and.Rossi.2008),.but.dispersal.and.recruit-
ment.limitation.may.signiicantly.slow.tree-line.expansions.(Dullinger.et.al..2004)..
Observed.uphill.shifts.in.tree.lines.may.represent.growth.in.height.by.individuals.
that.were.already.present.at.high.elevations.(Kullman.2001),.although.warmer.win-
ters.since.1987.in.Sweden.have.also.led.to.increased.high-elevation.germination.and.
seedling.establishment.(Kullman.2002)..Nevertheless,.recruitment.at.tree.lines.may.
depend.more.on.natural.disturbance.and.the.invasibility.of.existing.vegetation.than.
thermal. conditions. (Cullen. et. al.. 2001;. Daniels. and. Veblen. 2003;. Dullinger. et. al..
2004)..In.some.cases,.the.tree.line.may.relect.human.patterns.of.disturbance.and.
may.expand.upward.because.of.land.use.abandonment.rather.than.climate.warming.
(Dullinger.et.al..2004;.Batllori.and.Gutiérrez.2008)..Microclimate.and.soil.condi-
tions.also.inluence.local.or.regional.rates.of.uphill.expansion.(Holtmeier.and.Broll.
2005),.and.tree.lines.have.been.shown.to.shift.upward.faster.on.sheltered.or.south-
facing.slopes.than.on.exposed.or.north-facing.sites,.because.of.more.favorable.condi-
tions.for.growth.(Luckman.and.Kavanagh.2000;.Kullman.2001).
The.mechanisms.behind.upward.range.extension.by.the.pine.processionary.moth.
Thaumetopoea pityocampa
. in. Italy. have. been. studied. using. experiments. on. the.
effects.of.temperature.on.survival.and.dispersal..The.amount.of.time.in.winter.above.
threshold. temperatures. for. larval. feeding. has. increased,. leading. to. increased. sur-
vival.and.uphill.extensions.by.110.m.on.a.north-facing.aspect.and.230.m.on.a.south-
facing.aspect,.related.to.differences.in.insolation.(Battisti.et.al..2005)..In.addition,.
the.extreme.hot.summer.of.2003.had.ive.times.as.many.nights.above.the.threshold.
temperature.for.female.light.at.the.upper-elevation.range.limit,.resulting.in.dispersal.
and. colonization. of. extreme. high-elevation. sites. (Battisti. et. al.. 2006).. Warm. win-
ter.conditions.enabled.these.new.high-elevation.colonies.to.survive.into.2004..For.
T. pityocampa
,.a.widely.available.larval.host.plant.(
Pinus sylvestris
).permitted.the.
uphill.range.extension;.for.many.specialist.insect.species,.the.upper.limits.of.ranges.
