Climate change disease and amphibian declines
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Climate Change, Disease, and Amphibian Declines. by Jason R. Rohr. University of South Florida Department of Biology, SCA 110 4202 E. Fowler Ave. Tampa, FL 33620 [email protected] Climate Change, Amphibian Declines, and Bd.

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Climate change disease and amphibian declines

Climate Change, Disease, and Amphibian Declines

by Jason R. Rohr

University of South Florida

Department of Biology, SCA 110

4202 E. Fowler Ave.

Tampa, FL 33620

[email protected]


Climate change amphibian declines and bd

Climate Change, Amphibian Declines, and Bd

Also evidence that Bd-related declines are linked to climate change (Pounds et al. 2006, Bosch et al. 2006)


Outline for talk

Outline for Talk

Does global climate change affect worldwide amphibian declines associated with chytrid fungal infections?


Enigmatic amphibian declines

Enigmatic Amphibian Declines


Genus atelopus

Genus Atelopus


Climate change disease and amphibian declines

71 of 113 spp. presumed extinct,

many of which were ostensibly

caused by chytridiomycosis

from La Marca et al. 2005. Biotropica


Climate bd and conservation planning

Climate, Bd, and Conservation Planning

  • If we understand the climatic factors that accelerate Bd spread, increase host susceptibility, or elevate pathogen virulence, we can identify present and future geographic locations that might have amphibians at risk of Bd-related declines

  • Hence, we can better target areas that warrant monitoring and remediation


Tenuous links between climate and amphibian declines

Tenuous Links Between Climate and Amphibian Declines

  • Most of the evidence supporting climate change as a factor in Bd-related amphibian extinctions comes from a positive, but temporally confounded, multi-decade correlation between air temperature and extinctions in the toad genus Atelopus

Rohr et al. 2008 PNAS


Need to conduct detrended analyses

Need to Conduct Detrended Analyses?

  • If there is a true relationship between climate and Bd-related extinctions, fluctuations around temporal trends in temperature and extinctions should also positively correlate

  • There would many fewer non-causal explanations for this correlation than the multidecadal relationship between declines and temperature


Climate change disease and amphibian declines

Objectives

Use the Atelopus database to simult-aneously test various climate-related hypotheses for amphibian declines, controlling for multidecadal correlations and the intrinsic spatiotemporal spread of Bd


Ultimate hypothesis enso drives amphibian declines

Ultimate Hypothesis: ENSO Drives Amphibian Declines


Enso el ni o southern oscillation

ENSO: El Niño-Southern Oscillation

  • Commonly referred to as simply El Niño is a global coupled ocean-atmosphere phenomenon

    • The Pacific ocean signatures, El Niño (warm and wet) and La Niña (cool and dry) are important temperature fluctuations in surface waters of the tropical Eastern Pacific Ocean

    • The atmospheric signature, the Southern Oscillation (SO) reflects the monthly or seasonal fluctuations in the air pressure

  • Effects of El Niño in South America are direct and stronger than in North America


Proximal hypotheses for enigmatic bd related declines

Proximal Hypotheses for Enigmatic/Bd-related Declines

  • Spatiotemporal spread hypothesis:declines are caused by the introduction and spread of Bd, independent of climate (Bell et al. 2004, Lips et al. 2006)

  • Climate-based hypotheses:

    • Chytrid-thermal-optimum hypothesis:Increased cloud cover, due to warmer oceanic temperatures, leads to temperature convergence on the optimum temperature for growth of Bd (Pounds et al. 2006, Bosch et al. 2006)

    • Mean-climate hypothesis: changes in mean temp. and/or moisture conditions affect the distributions of amphibians (Whitfield et al. 2007, Buckley & Jetz 2007)

    • Climate-variability hypothesis: temporal variability in temp. cause suboptimal host immunity facilitating declines (Raffel, Rohr, et al. 2006)


Climate change disease and amphibian declines

Climate-Variability Hypothesis

Ectotherms:

*seasonal changes in body temperature*


Climate variability hypothesis

Climate Variability Hypothesis

  • Hypothesis: unpredictable temperature shifts, which are increasing with GCC, benefit pathogens more than hosts.

    • faster metabolisms of parasites should allow them to acclimate more quickly to unpredictable temperature shifts, especially for ectothermic hosts

    • parasites have fewer cells and processes to adjust and generally withstand greater temperature extremes than hosts (Portner 2002)

    • owing to their shorter generation times, parasites should evolve more quickly than hosts to changes in climate


Climate variability hypothesis1

Climate Variability Hypothesis

  • The categorically faster metabolisms, smaller size, and greater reproductive capabilities of parasites than hosts provides a general hypothesis for how global climate change will affect disease risk– unpredictable climate variability should increase disease.


Climate change disease and amphibian declines

Is there Spatiotemporal Spread of Atelopus Extinctions?

Rohr et al. 2008 PNAS


Atelopus extinctions through time

Atelopus Extinctions Through Time

Best fit curve

Rohr et al. 2008 PNAS


Climate change disease and amphibian declines

How we controlled for the likely epidemic spread of the pathogen


Ultimate hypothesis enso drives amphibian declines1

Ultimate Hypothesis: ENSO Drives Amphibian Declines


Climate change disease and amphibian declines

El Niño Years?

La Niña Years?


Ultimate hypothesis enso

Ultimate Hypothesis: ENSO

Rohr and Raffel 2010 PNAS


Must control for intrinsic dynamics to detect extrinsic factors

Must Control for Intrinsic Dynamics to Detect Extrinsic Factors!

  • No significant ENSO signature if we don’t control for probable epidemic spread

  • Hence, the availability of susceptible hosts appears the primary factor influencing epidemic spread followed secondarily by climate


Climate change disease and amphibian declines

But What is the Proximate Explanation?

What is it about El Nino years that is associated with amphibian extinctions?


Proximal hypotheses for enigmatic bd related declines1

Proximal Hypotheses for Enigmatic/Bd-related Declines

  • Spatiotemporal spread hypothesis: declines are caused by the introduction and spread of Bd, independent of climate (Bell et al. 2004, Lips et al. 2006)

  • Climate-based hypotheses:

    • Chytrid-thermal-optimum hypothesis:Increased cloud cover, due to warmer oceanic temperatures, leads to temperature convergence on the optimum temperature for growth of Bd (Pounds et al. 2006, Bosch et al. 2006)

    • Mean-climate hypothesis: changes in mean temp. and/or moisture conditions affect the distributions of amphibians (Whitfield et al. 2007, Buckley & Jetz 2007)

    • Climate-variability hypothesis: temporal variability in temp. cause suboptimal host immunity facilitating declines (Raffel, Rohr, et al. 2006)


Regional predictors tested w and w o a one year lag

Regional Predictorstested w/ and w/o a one year lag

Mean absolute value of monthly

differences (AVMD) in temp.

Cloud cover x temp. (Pounds et al. 2006)

Cloud cover (Pounds et al. 2006)

Temperature-dependent Bd growth (Pounds et al. 2006)

Precip. x temp. (Whitfield et al. 2007)

Diurnal temp. range (DTR)

Frost freq.

Precip.

Temp.

Temp. max.

Temp. min.

Vapor press.

Wet day freq.


Results of best subset model selection

Results of Best Subset Model Selection

results are similar using AIC


Can monthly temperature variability explain atelopus extinctions

Can Monthly Temperature Variability Explain Atelopus Extinctions?

Rohr and Raffel 2010 PNAS


Climate change disease and amphibian declines

Amphibian extinctions have often occurred in warmer years, at higher elevations, and during cooler seasons.Are monthly and daily variability in temperature also greater at these times and locations?


Do warmer years have greater variability in temperature

Do Warmer Years Have Greater Variability in Temperature?

Rohr and Raffel 2010 PNAS


Do high elevations have greater variability in temp

Do High Elevations Have Greater Variability in Temp.?


Do cooler months have greater variability in temp

Do Cooler Months Have Greater Variability in Temp.?

Rohr and Raffel 2010 PNAS


Results of path analysis

DTR

2

R

=

0.633

P

<0.001

P

<0.001

0.675

0.694

Lag amphibian extinctions

P

=

0.044

El Niño 3.4

-

0.4

66

2

R

=

0.674

P

=0.002

P

<0.001

0.67

3

0.868

AVMD

anomalies

2

R

=

0.567

Results of Path Analysis

Rohr and Raffel 2010 PNAS


We weren t convinced

We Weren’t Convinced


Experimental test

Experimental Test

  • Acclimated Cuban tree frogs to 15 or 25⁰ C for four weeks

  • Challenged with Bd at start of week five

  • Quantified survival and pathogen loads

15⁰C

15⁰C

25⁰C

25⁰C


Does temperature variability increase bd loads on frogs

Does Temperature Variability Increase Bd Loads on Frogs?

Bd load:

Bd-induced mortality:

Temperature shifts increased Bd loads and Bd-induced mortality

Raffel et al. in press Nature Climate Change


Summary

Summary

  • Availability of susceptible hosts appears to be the primary factor influencing the spread of Bd

  • There is a strong ENSO signature to extinctions after controlling for epidemic spread

  • Both field patterns of extinctions and manipulative experiments support the climate-variability hypothesis for amphibian extinctions


Climate change disease and amphibian declines

ConclusionsTemperature, temperature variability, and Central Pacific El Niño events are increasing in tropical and subtropical regions because of climate change; thus, global climate change might be contributing to enigmatic amphibian declines, by increasing disease risk


Climate change disease and amphibian declines

ConclusionsElevated temperature variability might represent a common, but under-appreciated, link between climate change and both disease and biodiversity losses and might offer a general mechanism for why disease would increase with GCC.


Climate change disease and amphibian declines

Parte 4: MODELO CLIMÁTICO ECO FISIOLÓGICO para anfibios


Spea hammondi fisher and shaffer 1996

Spea hammondiFisher and Shaffer 1996


Bufo boreas fisher and shaffer 1996

Bufo boreasFisher and Shaffer 1996


Rana aurora bd induced fisher and shaffer 1996

Rana aurora (Bd induced?)Fisher and Shaffer 1996


Preparaci n de modelos

Preparación de modelos

  • Molde de Látex a partir de un espécimen de colección.

  • Obtención de modelos de agar.


Experimento de campo

Día

SECO - SOL

(2 modelos)

SECO - SOMBRA

(2 modelos)

Noche

HÚMEDO - SOMBRA

(2 modelos)

HÚMEDO -SOL

(2 modelos)

Experimento de campo

  • 4 condiciones experimentales (factorial).


Experimento de campo1

Experimento de campo

  • Modelos conectados a data loggers.

  • Reemplazo de modelos cada 3-4 hr.

SECO

SOL

SECO

SOMBRA

HÚMEDO

SOL

HÚMEDO

SOMBRA


T operativa y p rdida de agua

T operativa y Pérdida de agua

sombra húmedo

sol seco

Del Puerto Canyon; 12 march 2012; nublado; Annaxyrus boreas model


T ambiental y p rdida de agua

T ambiental y Pérdida de agua

sol seco

Tª sol

sombra seco

sol húmedo

sombra húmedo

Tª sombra

Los Baños Cistern; 5 march 2012; soleado; metamórficos


Climate change disease and amphibian declines

Pseudacris sierra

Un sitio persistente

Un sitio Extinct


Species calibrations for ca frogs

Species Calibrations for CA Frogs

Hydric Loss Rates and Extinction, significant assoc:*,**,***

Low sensitivity to Bd:

Immune to Bd:

  • Speahammondi

  • Anaxyrusboreas***

  • Anaxyruspunctatus

  • Pseudacrissierra***

  • P. cadaverina*

  • P. hypochondriaca

Very sensitive to Bd:

Rana sierrae***

Rana aurora


Climate change disease and amphibian declines

Bufo americanus

distancia recorrida en 10 minutos de la locomoción forzada

Preest and Pough, Funct Ecol 1989


Climate change disease and amphibian declines

  • Víctor H. Luja [email protected]

  • Octavio Jiménez [email protected]

  • Eric Curiel [email protected]


Desarrollando un modelo clim tico eco fisiol gico para anfibios

Desarrollando un MODELO CLIMÁTICO ECO FISIOLÓGICO para anfibios

  • 1. Buscamos un modelo que explique mejor el límite de distribución de las especies. Buscamos encontrar el conjunto de tasas de pérdida de agua (y de temperatura) durante el día vs la noche que explique los límites más secos (el umbral de desecación) debajo del cual la especie no se encuentra mas. Este umbral que mejor ajusta está basado en las ubicaciones de todas las poblaciones a partir de 1970.

  • 2. Este umbral hídrico de pérdida de agua es conceptualmente similar al h_r para las horas de restricción de actividad debido al calor.

  • 3. Entonces, nosotros probaremos como se comporta este modelo para predecir la distribución actual de las extinciones (por ejemplo cambios en la pérdida hídrica del delta entre 1975–2010, debido al incremento en la intensidad de la sequía).


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