Geoscience Reference
In-Depth Information
Examining.the.climate-linked.epidemic.hypothesis.and.the.spatiotemporal.spread.
hypothesis,.Rohr.et.al..(2008).showed.that.there.was.spatial.structure.to.the.timing.
of.
Atelopus
.extinctions,.but.the.cause.for.this.structure.was.unknown..Furthermore,.
Rohr.et.al..(2008).stated.that.the.temporal.pattern.of.
Atelopus
.extinctions.reported.
by.Lips.et.al..(2006).in.Panama.could.also.be.explained.by.spatiotemporal.heteroge-
neities.in.the.emergence.of.a.novel.pathogen.or.an.abiotic.stressor.that.caused.local.
population.declines.(McCallum.2005)..They.also.stated.that.in.Costa.Rica,.BD.might.
have.been.widespread.long.before.declines.were.detected.(Puschendorf.et.al..2006).
Rohr. et. al.. (2008). showed. a. positive. multidecade. correlation. between.
Atelopus
.
extinctions. and. mean. air. temperature. in. the. previous. year.. However,. the. evidence.
that.this.causes.population.declines.is.weak.because.other.variables.were.also.good.
predictors.of.extinction.events..Although.Rohr.et.al..(2008).found.no.support.for.the.
“chytrid-thermal-optimum.hypothesis”.(Pounds.et.al..2006;.Blaustein.and.Dobson.
2006),.they.suggest.that.climate.change.is.likely.to.play.an.important.role.in.amphib-
ian.population.declines.worldwide.
Climate. change. and. outbreaks. of. chytridiomycosis. have. been. reported. in.
recent.studies..Bosch.et.al..(2006).showed.a.signiicant.association.between.ris-
ing. temperatures. and. outbreaks. of. chytridiomycosis. in. Spain.. Increases. in. chy-
driomycosis. were. correlated. with. low. average. summer. maximum. temperatures.
in.Australia.(Drew.et.al..2006)..During.the.decline.of.amphibians.in.New.South.
Wales,.Australia,.very.few.moribund.specimens.examined.were.positive.for.BD.
(Alford.et.al..2007)..Alford.et.al..(2007).suggested.that.stress.during.growth.and.
development.may.contribute.to.limb.asymmetries.in.amphibians..They.suggested.
that. unusual. climate. conditions. might. be. a. signiicant. stressor. on. amphibian.
growth.and.development..In.Australia,.Alford.et.al..(2007).attributed.the.greater.
frequency. of. limb. asymmetries. in. “pre-declining. populations”. compared. with.
nondeclining.“control”.populations.to.stress.from.“dramatic.regional.warming.”.
They.suggested.that.BD.might.not.be.the.only.factor.involved.in.amphibian.popu-
lation.declines.in.this.region.and.that.climate.conditions.alone.may.be.an.impor-
tant.factor.in.declines.
Di.Rosa.et.al..(2007).showed.that.BD.may.be.present.without.causing.chytridiomy-
cosis.in.frogs.in.Italy.and.that.other.pathogens.may.also.contribute.to.frog.declines.
in.this.region..In.agreement.with.Pounds.et.al..(2007),.they.suggested.that.climate.
conditions.might.make.amphibians.more.susceptible.to.a.number.of.pathogens.
Evidence. from. studies. at. the. Savannah. River. long-term-research. site. in. South.
Carolina. illustrates. that. populations. of. several. amphibian. species. have. been. in.
decline.(Daszak.et.al..2005)..At.this.site,.the.presence.of.BD.was.rare.and.there.was.
no. evidence. of. chytridiomycosis.. The. investigators. concluded. that. the. population.
declines.in.this.region.were.more.likely.due.to.low.rainfall.and.shortened.hydrope-
riod.for.breeding.rather.than.an.epidemic.caused.by.BD.
Depending.upon.the.model,.a.speciic.region.may.receive.more.or.less.precipita-
tion.in.the.future.than.at.present.and.may.be.colder.or.warmer.than.at.present.(Lawler.
et.al..2006,.2009)..Such.changes.could.signiicantly.affect.hydroperiods.critical.to.
amphibian.life.cycles..Thus,.Gervasi.and.Foufopoulos.(2008).showed.that.wood.frog.
(
Lithobates sylvaticus
). tadpoles. exposed. to. desiccation. had. shorter. development.
times,.weaker.cellular.immune.system.responses,.and.lower.total.leukocyte.numbers.
