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The impact of severe drought on survival, fecundity and population persistence in an endangered amphibian

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Climate is globally changing. In Europe, studies have highlighted an increasing trend in both the frequency and magnitude of droughts. Abrupt changes in the frequency, location, or intensity of extreme heatwaves and droughts can have direct and severe effects on wild populations. Amphibians are the planet's most threatened group of vertebrates, with over 40% of known species considered in decline. To date, researchers have mainly focused on the influence of repeated droughts on species occurrence and community composition; however, evidence of the direct impact of climatic factors on the demographic parameters of amphibians is currently not well documented. Further investigation of this issue is therefore of critical importance in order to optimize local and global wildlife conservation policies in the context of a changing climate. This study used capture–recapture data to investigate the impact of severe drought on the survival and fecundity of a threatened amphibian, the yellow-bellied toad (Bombina variegata, L.), as well as to predict how potential changes in the frequency of droughts might influence the population growth rate. By developing multievent capture-recapture models, we showed that severe drought has a negative impact on fecundity and postmetamorphic survival at different ontogenetic stages. Then, using stochastic matrix population models, we predicted that changes in drought frequency negatively influence the population growth rate, which is a warning sign for population persistence. Direct conservation actions are then proposed to mitigate the detrimental effects of drought on population dynamics.
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v v Article e012461v
IntroductIon
     -
       -

     
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       
        
     -
      
      -
       
       -
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     
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
23412
1UMR 5023 LEHNA, Laboratoire d’Ecologie des Hydrosystèmes Naturels et Anthropisés,
CNRS, Université Lyon 1, 69100 Villeurbanne, France
2CEFE UMR 5175, CNRS – Université de Montpellier – Université Paul-Valéry Montpellier – EPHE, Laboratoire
Biogéographie et Ecologie des Vertébrés, 1919 Route de Mende, 34293 Montpellier Cedex 5, France
3Oce National des Forêts, Agence de Verdun, 55100, Verdun, France
4Alcedo Faune Flore, Quartier Le Fez, 07110, Sanilhac, France
Citation:


Abstract.
-


    
      -



Bombina varie-
gata-


  
-

Key words:Bombina variegata
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
v v Article e012462v www.esajournals.org
CAYUELA ET AL.
-

     
       

      -
       



     


      

 
-

-

 -
  
   
Bufo bufo
    Triturus cristatus   
  
 T. cristatus
Ambysto-
ma tigrinum

Rana sevosaAmbystoma
opacum
Gyrinophilus porphy-
riticus

     
     
  
     
      
     
       

 

      


    Bombina varie-
gata 
      
      

       
        
    

-

       

    -
     B variegata  

        -
 

     -
 

     
      -
       

      -
-

    
      -
      
      -
     
-


Methods
Study area and field sampling
      
of B variegata     -
    -
       
       
      

   
      
       
    
      
       
v v Article e012463v www.esajournals.org
CAYUELA ET AL.
      -
     
     
      -
      
         

       
       

      
      
      
  
 
-
  

       
    

-
       

 
-
        
    
-
     

    
       
       
      

       
       
    
     


    -
-

Multievent capture–recapture model
       
       
       
     
         
     
      
     
     -
     
        
     -
    
      
       
       
      
        
          
      
       
       -
       
      

 -
      -
     
    
       -
      
       
       
       
  

 
     
       Bombina
variegata


v v Article e012464v www.esajournals.org
CAYUELA ET AL.
-


     
   αα 

α
ββββ

 -
    

 
     
     
      -


 φ φ
  φφ  φφ 
       
      

     
  -
-
      
     
  -
    
       
    -


-

1𝛼
JM
0𝛼
JM 0 0 0 0 0 000
01𝛼JF 0𝛼JF
0 0 0 0 000
00𝛽JM 01𝛽JM
0 0 0 000
0 00𝛽JF 01𝛽JF
0 0 000
0 0 00 𝛽SM 01𝛽SM
0 000
0 0 00 0 𝛽SF 01𝛽SF
000
0 0 0 0 0 0 1 0 000
0 0 0 0 0 0 0 1 000
0 0 0 0 0 0 0 0 100
0 0 0 0 0 0 0 0 010
0 0 0 0 0 0 0 0 001
10 0 0 0 0 0 0 0 0 0
01 0 0 0 0 0 0 0 0 0
00𝜙JM 000 0 0 0 0 1𝜙JM
00 0 𝜙JF 0000 0 0 1𝜙JF
00 0 0 𝜙SM 000 0 01𝜙SM
00 0 0 0 𝜙SF 00 0 01𝜙SF
00 0 0 0 0 𝜙BM 0 0 01𝜙BM
00 0 0 0 0 0 𝜙BF 0 01𝜙BF
00 0 0 0 0 0 0 𝜙NBM 01𝜙NBM
00 0 0 0 0 0 0 0 𝜙NBF 1𝜙NBF
00 0 0 0 0 0 0 0 0 1
(2)
(1)
v v Article e012465v www.esajournals.org
CAYUELA ET AL.

   γγ 
γγ 

sensu
    -
-


(4)
      
-

Biological scenarios using the E- SURGE program
    
      
     
     -
   
    
 -
      
 α ϕ   γ p(-
        

      
    -
  

 
     -
       
      -
       
-
       

      
     

-


     -
     -

     
t
   t       

     
  
  -


Simulation matrix model
      

  
100000 0 0 0 0 0
010000 0 0 0 0 0
001000 0 0 0 0 0
000100 0 0 0 0 0
000010 0 0 0 0 0
000001 0 0 0 0 0
000000 𝛾BM 01𝛾BM
00
000000 0 𝛾BF 01𝛾BF 0
0000001𝛾NBM 0𝛾NBM
00
000000 0 1𝛾NBF 0𝛾NBF 0
000000 0 0 0 0 1
1 00 00
1 00 00
1pJM pJM
000
1pJF pJF
000
1pSM 0pSM
00
1pSF 0pSF
00
1pBM 00pBM 0
1pBF 000pBF
1 00 00
1 00 00
1 00 00
(3)
v v Article e012466v www.esajournals.org
CAYUELA ET AL.
    
   

(5)
     1 
2
      
-

     t  
female at t   
      -
  

    
       
-
      -
        -
    

         
     k 
      
     
tkt0k
       


result
        
      
      
(00F
BP
S1
00
0
S2S3)

 
α 
α 
β 
β 
β 
β 
φ 
φ 
φ 
φ 
φ 
φ 
φ 
φ 

γ tt
γ tt
γ 

γ 

p 

p 

p 

p 

p 

p 

v v Article e012467v www.esajournals.org
CAYUELA ET AL.
      -
       

       
       
        
        
        
      
  
     α
φγ p  


    
        -
     
      
       
       

       -
      
  
 
       -
     
  
Bombina variegata
rk-

      

r    kDev 
1  YEAR  24  
2  YEAR  22  
3  YEAR  21  
4  YEAR    
5 DRY  YEAR  18  
6 DRY  YEAR  20  
7  YEAR  17  
8  YEAR    
   YEAR YEAR 21  
10   YEAR YEAR   
11   YEAR YEAR 18  
12   YEAR YEAR 16  
13 DRY  YEAR YEAR 15  
14 DRY  YEAR YEAR 17  
15   YEAR YEAR 14  
16   YEAR YEAR 16  
17   YEAR  21  
18   YEAR    
   YEAR  16  
20   YEAR  18  
21 DRY  YEAR  15  
22 DRY  YEAR  17  
23   YEAR  14  
24   YEAR  16  
25   YEAR  17  
26   YEAR  15  
27   YEAR  14  
28   YEAR  12  
 DRY  YEAR  11  
30 DRY  YEAR  13  
31   YEAR  10  
32   YEAR  12  
v v Article e012468v www.esajournals.org
CAYUELA ET AL.
 
      

     
       

       

dIscussIon

       
     B. variegata
     

      
    
Fecundity is impacted by drought events
      
     
      
     

       
   B variegata  
      
Bombina variegata
         
             
   





v v Article e01246v www.esajournals.org
CAYUELA ET AL.

  
        

 
    
    
      
  
       -

      
      -
       
       -
       
       
        
      -
      
         

Survival probability is impacted by age and drought
       -
      
      
      
        
       
         
     
  

       -
        -
 
       
 B variegata     

     
     
      
    -
    
     

     
      
     

       
      
 B variegata     -
     
      
      
     
      
     
      

Population growth rate is impacted by
drought frequency
     
     
      

       
      
       
     
      -
 
        
         
          
      
        B variegata
     
      
        
     
     -
  
      
     
     -
     
Conservation recommendations
      

for B. variegata    -
      
     
       -
     

    -
      
v v Article e0124610v www.esajournals.org
CAYUELA ET AL.
      -
      
Bombina variegata

-


      
    
 -
     -
     


-

       
     
      
    
  
       
       
 
      -
       


-
-
 

      -

 
     
      -

       
        
     
      -

 

 
     -
   

-
      -
  
      
     
      
     
      -
     

-
      
      
-
       

     
B. variegata
AcknowledgMents
       
   
       
       
      
  
      
 
lIterAture cIted

   

-
  
(Rana sylvatica
       
Bombina
variegata
       
     
       
     

-
     -

         
        
      Bombina
variegata



v v Article e0124611v www.esajournals.org
CAYUELA ET AL.
-

        
  
-
      

         



   
      -
   in   
   
    

-

    Ambystoma tigri-
num
-
-



-

-
  
  -

 -
       
    in     
-
       -
  
-
      -

      
    


-
 -
  

          
      -
     


      -
      


  -
 

        
   
   

          
    
  -




   
-

     Bombina Pelo-
phylaxRana
-
   


        
  Bombina variegata   
       


         
      



      
    

  -
        -
    Bombina variegata -
    


      
    

     


     
    
  

v v Article e0124612v www.esajournals.org
CAYUELA ET AL.
       
     
Bombina variegata et Bufo calamita

         
-
    
 -
-

     -

-

        -
Bombina variegata
      

    -

 
      Bombi-
na variegata    


-

        -

    

           
     
Rana sevosa
-

          
      -
      



     
-





           
     -
    

         
       
-

          -



        


-

  -


 
   
-
    




     -

  -
-

 
       -
      

        


   
     
  -
    

... Recruitment in previous breeding seasons has been identified in several other studies as a key determinant of contemporary population sizes (Scheele et al. 2012, Cayuela et al. 2016a. This provides justification that impacts to recruitment should be targeted for understanding declines brought about by climatic anomalies. ...
... Our result that amphibian survival was correlated with rain and temperature agrees with other studies (Cayuela et al. 2016a, Cayuela et al. 2016b) and demonstrates an impact of the drought. The lack of rain and high temperatures likely contributed to mortality in L. aurea during the drought. ...
... Extreme weather anomalies in future climate change scenarios are likely to surpass the critical survival thresholds for many species (Maxwell et al. 2019). Climate change is likely to impact many animal populations globally (Walls et al. 2013, Cayuela et al. 2016a, Potvin et al. 2017, Zylstra et al. 2019. Synchronised global action on climate change is needed to fortify conservation efforts. ...
Article
Full-text available
Biodiversity is in global decline during the Anthropocene. Declines have been caused by multiple factors, such as habitat removal, invasive species, and disease, which are often targets for conservation management. However, conservation interventions are under threat from climate change induced weather extremes. Weather extremes are becoming more frequent and devastating and an example of this was the 2019/2020 Australian drought and mega-fires. We provide a case study the impacts of these extreme weather events had on a population of the threatened frog Litoria aurea that occurs in a constructed habitat which was designed to reduce the impact of introduced fish and chytrid-induced disease. We aimed to determine what factors influenced persistence so that the design of wetlands can be further optimised to future-proof threatened amphibians. We achieved this with 4 years (2016-2020) of intensive capture-recapture surveys during austral spring and summer across nine wetlands (n = 94 repeat surveys). As hypothesized, drought caused a sharp reduction in population size, but persistence was achieved. The most parsimonious predictor of survival was an interaction between maximum air temperature and rainfall, indicating that weather extremes likely caused the decline. Survival was positively correlated with wetland vegetation coverage, positing this is an important feature to target to enhance resilience in wetland restoration programs. Additionally, the benefits obtained from measures to reduce chytrid prevalence were not compromised during drought, as there was a positive correlation between salinity and survival. We emphasize that many species may not be able to persist under worse extreme weather scenarios. Despite the potential for habitat augmentation to buffer effects of extreme weather, global action on climate change is needed to reduce extinction risk. Supplementary information: The online version contains supplementary material available at 10.1007/s10531-022-02387-9.
... The predicted rise of 3°C temperature and the drop of the annual precipitation by up to 200 mm by the year 2020 along the urban-fringe region in Melbourne, Australia, would eventually cause water deficiency in ponds by the year 2030 which may cause a reduction of 41% occupancy of the Spotted Marsh Frog (Limnodynastes tasmaniensis) (Wilson et al 2012). Cayuela et al. (2016) reported a 31% reduction in the population of Yellow-bellied Toads (Bombina variegata) during a severe drought in southeastern France. This decline is possibly the direct effect of drought on tadpole mortality due to the dehydration of breeding sites. ...
... We believe implementing the measures suggested in the policy, such as empirical research on biodiversity, setting national biodiversity indicators, integration of biodiversity conservation with other sectors such as forestry, adopting efficient water conservation methods for local communities, construction of water storage sites, integrated watershed management, reforestation of catchments areas, improvement in weather forecast systems, and better coordination among various stakeholders and departments such as forestry, wildlife and city districts could lead to conserve the endemic species and their habitats. Some other measures which have widely been used to mitigate the impacts of drought, high temperature and precipitation patterns include ditch draining (Delft & Creemers, 2008) and the renovation of hydraulic networks, construction of small dams to store water to be into the habitat during dry periods and by restoring riparian forests to enhance vegetation cover to mitigate the effect of droughts (Cayuela et al. 2016). We, therefore, suggest carrying out detailed scientific studies on the ecology of amphibians, quantification of climate change threats and their responses to these threats in order to devise possible measures for their conservation and management. ...
Article
Full-text available
Climate change could affect lentic breeding amphibians directly by reducing their survival and fecundity, or indirectly by altering their habitats. Increase of temperature and thermal variation may affect breeding phenology, shift distribution patterns, and the possible spread of epidemics. We have provided a critical review on climate change and extreme weather events in Pakistan to discuss possible future scenarios for assisting with the survival of Pakistan's amphibians. Amphibian species of Pakistan, such as Duttaphrynus himalayanus, Bufotes latastii, B. pseudoraddei, B. baturae, Scutiger occidentalis, Allopaa barmoachensis, A. hazarensis, and Nanorana vicina inhabiting the northern region of the country might experience the effects of warmer atmospheric temperatures, altered precipitation patterns, glacier melting, and flash floods while species found in the southwestern arid terrain, such as Bufotes surdus, B. zugmayeri, Duttaphrynus olivaceus, and Chrysopaa sternosignata are expected to suffer from drought and excessive heat. We suggest studying the impact of these changes in the climate to understand the response of amphibian species of Pakistan so that appropriate mitigation strategies, such as ditch draining in areas experiencing drought, could be devised.
... The predicted rise of 3°C temperature and the drop of the annual precipitation by up to 200 mm by the year 2020 along the urban-fringe region in Melbourne, Australia, would eventually cause water deficiency in ponds by the year 2030 which may cause a reduction of 41% occupancy of the Spotted Marsh Frog (Limnodynastes tasmaniensis) (Wilson et al 2012). Cayuela et al. (2016) reported a 31% reduction in the population of Yellow-bellied Toads (Bombina variegata) during a severe drought in southeastern France. This decline is possibly the direct effect of drought on tadpole mortality due to the dehydration of breeding sites. ...
... We believe implementing the measures suggested in the policy, such as empirical research on biodiversity, setting national biodiversity indicators, integration of biodiversity conservation with other sectors such as forestry, adopting efficient water conservation methods for local communities, construction of water storage sites, integrated watershed management, reforestation of catchments areas, improvement in weather forecast systems, and better coordination among various stakeholders and departments such as forestry, wildlife and city districts could lead to conserve the endemic species and their habitats. Some other measures which have widely been used to mitigate the impacts of drought, high temperature and precipitation patterns include ditch draining (Delft & Creemers, 2008) and the renovation of hydraulic networks, construction of small dams to store water to be into the habitat during dry periods and by restoring riparian forests to enhance vegetation cover to mitigate the effect of droughts (Cayuela et al. 2016). We, therefore, suggest carrying out detailed scientific studies on the ecology of amphibians, quantification of climate change threats and their responses to these threats in order to devise possible measures for their conservation and management. ...
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Climate change could affect lentic breeding amphibians directly by reducing their survival and fecundity, or indirectly by altering their habitats. Increase of temperature and thermal variation may affect breeding phenology, shift distribution patterns, and the possible spread of epidemics. We have provided a critical review on climate change and extreme weather events in Pakistan to discuss possible future scenarios for assisting with the survival of Pakistan’s amphibians. Amphibian species of Pakistan, such as Duttaphrynus himalayanus, Bufotes latastii, B. pseudoraddei, B. baturae, Scutiger occidentalis, Allopaa barmoachensis, A. hazarensis, and Nanorana vicina inhabiting the northern region of the country might experience the effects of warmer atmospheric temperatures, altered precipitation patterns, glacier melting, and flash floods while species found in the southwestern arid terrain, such as Bufotes surdus, B. zugmayeri, Duttaphrynus olivaceus, and Chrysopaa sternosignata are expected to suffer from drought and excessive heat. We suggest studying the impact of these changes in the climate to understand the response of amphibian species of Pakistan so that appropriate mitigation strategies, such as ditch draining in areas experiencing drought, could be devised.
... Articles in R&A are made available under a Creative Commons Attribution-NonCommercial 4.0 International license. D rought is an important consequence of natural climatic processes that can have direct and severe effects on amphibian populations (Cayuela et al. 2016). Extreme weather and climate events, which include extreme floods and droughts, have increased during the last century (Walls et al. 2013). ...
... Studies have revealed direct effects of drought on tadpole mortality due to the desiccation of breeding sites (Cayuela et al. 2016). Most anuran larvae must complete metamorphosis and move onto land before their larval aquatic habitats dry out. ...
... Climate is a major driver of biological processes for amphibians, and adaptations influenced by climate change could contribute to extinctions (Bucciarelli et al., 2020). For example, global warming and severe drought decrease body size and body condition in many amphibian species, which consequently decreases survivorship and fecundity (Reading, 2007;Caruso et al., 2014;Cayuela et al., 2016). Climate-induced habitat changes, such as decreased availability of surface water for breeding, can also cause amphibian populations to decline (Miller et al., 2018). ...
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Climate change and prolonged drought have negatively impacted amphibians in southern California, U.S.A. Due to the severe drought from 2012–2016, agencies and researchers had growing concern for the persistence of the arroyo toad ( Anaxyrus californicus ), an endangered endemic amphibian in this region. Range-wide surveys for this species had not been conducted for at least 20 years. In 2017–2020 we conducted collaborative surveys for arroyo toads at historical locations. We surveyed 87 of the 115 total sites having historical records and confirmed that the arroyo toad is currently extant in 60 of 87 sites and 19 of 25 historically occupied watersheds. Only detection/non-detection and not population size was recorded, therefore potential declines at the population level could not be assessed. In other amphibian species, body condition has been documented to decrease with a decrease in water availability. To further investigate the drought’s impact on this species, we calculated an average body condition index annually for arroyo toads using allometric measurements recorded from 1996–present. This index was plotted against precipitation records over time. Our data show that body condition did not significantly change during drought years, but hydro-regulation may be masking an effect. Our study suggests that this species shows some resiliency to climate change and drought, and that mitigating invasive species, hydro-modification, and other anthropogenic drivers may currently be the most beneficial strategy for toad conservation. Arroyo toad conservation actions may also provide simultaneous benefits to several other native species that share the same habitat.
... Data at the individual level can provide insight into spatial and temporal dynamics of populations, resulting in more robust assessments of population health than abundance estimates alone (Kurose et al. 2005;Koons et al. 2006;Reid et al. 2006). For example, it is common that environmental changes affect ages and sexes differently because of differences in physiology, size, behavior, and space use (Steen et al. 2006;Popescu and Hunter 2011;Cayuela et al. 2016). Improved understanding of these differential effects broadens the ecological understanding of species and the ability to manage them. ...
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Documenting the sex of individuals encountered during wildlife research and monitoring activities is important for understanding and tracking changes in populations. However, sexing salamanders can be particularly difficult because secondary sex characters are often subtle or only visible during the breeding season, and guidance on species-specific sex determination is lacking from most field guides. The purpose of this guide is to provide a reference to assist biologists in the Central Appalachian region with identifying sex of live adult salamanders. In the main text we provide summary tables and figures to serve as concise references in the field. In Text S1 (Supplemental Material) we provide individual species accounts that contain concise yet comprehensive information for each species based on the published literature, as well as many images depicting sexually dimorphic characters. Our focal region encompasses partial or entire distributions for 56 species of salamanders in five families (Ambystomidae, Cryptobranchidae, Plethodontidae, Proteidae, and Salamandridae). We identified seven morphological characters that are strongly sexually dimorphic and useful for sexing live, non-anesthetized, adult salamanders in the field, with males of individual species exhibiting one to five of the characters. We identified >20 additional characters that are weakly sexually dimorphic, difficult to distinguish in the field, or species-specific. Our guide serves as a synthesis of sexually dimorphic characters available for salamanders in Central Appalachia, and we anticipate it will have broad value for researchers, monitoring programs, and salamander enthusiasts in eastern and central North America.
... La calibración de los modelos sugiere que la deshidratación simulada para P. cinereum emula a los organismos vivos pero nuestros resultados podrían subestimar la vulnerabilidad de G. marsupiata. El incremento de temperatura y una época de lluvias inestable a nivel local parecen afectar en mayor medida a G. marsupiata (Anderson et al., 2011;Aparicio, 2014;Cayuela et al., 2016). Catenazzi et al. (2014) sugieren que los anfibios de alta montaña están mejor adaptados a las variaciones térmicas pero su conclusión se basa en la ecología térmica de los anfibios y no en la regulación hídrica. ...
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Prolonged drought due to climate change has negatively impacted amphibians in southern California, U.S.A. Due to the severity and length of the current drought, agencies and researchers had growing concern for the persistence of the arroyo toad (Anaxyrus californicus), an endangered endemic amphibian in this region. Range‐wide surveys for this species had not been conducted for at least 20 years. In 2017–2020, we conducted collaborative surveys for arroyo toads at historical locations. We surveyed 88 of the 115 total sites having historical records and confirmed that the arroyo toad is currently extant in at least 61 of 88 sites and 20 of 25 historically occupied watersheds. We did not detect toads at almost a third of the surveyed sites but did detect toads at 18 of 19 specific sites delineated in the 1999 Recovery Plan to meet one of four downlisting criteria. Arroyo toads are estimated to live 7–8 years, making populations susceptible to prolonged drought. Drought is estimated to increase in frequency and duration with climate change. Mitigation strategies for drought impacts, invasive aquatic species, altered flow regimes, and other anthropogenic effects could be the most beneficial strategies for toad conservation and may also provide simultaneous benefits to several other native species that share the same habitat. U.S. range‐wide surveys for arroyo toads were conducted at 100% of the historical watersheds and ~76% of the historical sites following prolonged drought. Arroyo toads were detected at most sites delineated in the 1999 Recovery Plan for a downlisting consideration, yet toads could not be detected at 31% of sites surveyed indicating further declines. These are the most current and comprehensive data on number of extant arroyo toad populations since 1999 and can be used as a baseline for reevaluation of the Recovery Plan.
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Climate change effects are contributing to widespread declines of amphibians, and pond-breeding species may be particularly sensitive to future drought conditions that restrict wetland hydroperiods and decrease opportunities for successful breeding and recruitment. Pond-breeding amphibian populations can compensate for periodic droughts via episodic booms in recruitment, but studies predict that increased future drought conditions will negatively impact long-term persistence for several species. The southeastern United States is a global hotspot of amphibian biodiversity where future trends in drought conditions are uncertain. This study applied a population viability analysis (PVA) framework for an at-risk amphibian, the gopher frog (Lithobates [Rana] capito), to (i) explore population sensitivity to the frequency of droughts that restrict reproductive events, relative to changes in other demographic rates, and (ii) forecast future population viability over 30 years, given plausible scenarios varying in the frequency and duration of droughts adapted from recent historical patterns in the southeastern United States. Population persistence was highly sensitive to frequency of reproductive success. Persistence was fairly insensitive to all demographic parameters when reproductive success was ≥ 0.7 (i.e., ≤ 3 drought years per decade, on average), but sensitivity to survival of terrestrial stages (juvenile, adults) and initial abundance increased as reproductive success decreased. Persistence probabilities were relatively high (0.63–0.99) across a range of plausible future drought scenarios, with higher persistence probabilities (> 0.89) for all scenarios where drought years did not increase from recent historical conditions. Our results indicate gopher frog populations are likely resilient to periodic droughts that occur in 4 or fewer years per decade, but extirpation of some populations is possible if recent drought patterns repeat or increase during the next 30 years. Estimates of future risk to gopher frog populations can inform forthcoming status assessments and designation decisions of the U.S. Fish and Wildlife Service. More broadly, PVAs incorporating drought dynamics can identify climate thresholds that at-risk, pond-breeding amphibian populations can tolerate, which can inform management actions (e.g., maintaining a range of hydroperiods across proximate wetlands) that provide sufficient frequent breeding opportunities for long-term persistence even under drought conditions.
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The classification history of European Bombina is recalled. The past distribution of Bombina variegata in France is related: its range expanded until the Landes, Pyrénées-Orientales, Bouches-du-Rhône, Bretagne sides and Nord department. B. variegata was never reported in the following departments: Alpes-Maritimes, Var, Ariège, Hautes-Pyrénées, Lot-et-Garonne, Gers, Tarn, Tarn-et-Garonne, Aveyron, Morbihan, Finistère, Côtes d’Armor, Ille-et-Vilaine, Manche, Hautsde- Seine, Seine-Saint-Denis, Oise, Pas-de-Calais. It was erronneously reported from Lozère and Pyrénées-Atlantiques. It does not reach the Nord and Pas-de-Calais seaside. Its decline, started in the 19th century, increased during the last forty years.
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In Western Europe, habitat loss and landscape fragmentation has led to significant population decline in various animal groups, including amphibians. The extinction of the last natural populations of the yellow-bellied toad in Belgium, Luxembourg and several regions of southern and western France suggests a widespread decline. By using site-occupancy models and adding covariates corresponding to the human-influenced features of the landscape, we tried to identify the relative effects of different land-use types on the species’ distribution pattern in a man-made environment (the Alsatian Rhine floodplain in France). We recorded presence-absence data in 150 forest sample plots (300 × 300 m) and then modeled species distribution while taking into account detection errors in the field. Land-use was recorded on two spatial scales: within the forest sample plots and in a 1500 m radius buffer area around the forest plots. In the forest plots, toad occurrence was negatively correlated with loss of forest cover to agricultural land. In contrast, occurrence is positively correlated with the density of human-made rutted dirt paths and tracks, which provide semi-natural breeding sites. In the 1500 m radius buffer zones around forest plots, toad occurrence was negatively correlated with the density of urbanization and road networks. These results can be used to plan conservation strategies for amphibians in human-dominated landscapes.
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The fine structure of nuptial pad surface of the anuran amphibians Bom-bina variegata, Pelophylax epeiroticus, Pelophylax ridibundus and Rana dalmatina, was examined by scanning electron microscopy. Nuptial pads are cutaneous second-ary sexual characters of males that appear during the breeding season and disappear afterwards following an annual cycle. In males of P. epeiroticus, P. ridibundus and R. dalmatina, nuptial pads were observed on the ventrolateral aspect of the first digit (the thumb) as darkish and remarkably keratinized papillae. In males of B. variega-ta nuptial pads were almost black and very visible on the thumb, the second and the third digit of the front legs. They also extended on the ventral surface of the forearms. Under scanning electron microscope numerous small papillae were observed rising above pad's surface. In P. epeiroticus, P. ridibundus and R. dalmatina, these papillae were almost rounded at the base while at the dome shaped top they had many micro-processes organised in groups, thus assuming the shape of a "flower" which differed slightly among these three ranid species. In B. variegata the protuberances were coni-cal with heavily keratinized hooks without microprocesses. Our results show that sur-face morphology of nuptial pads is unique for each species and could be considered as a species-specific character.
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Climate change is a poorly understood, emerging threat to many amphibian species. One of the ways climate change is likely to affect amphibians is through increased recruitment failure associated with more frequent climatic extremes. To understand the risk posed by this threat, we combined 13 years of annual monitoring and multi-scaled habitat modelling at the site (n=60), pool (n=105) and nest (n=170) levels to investigate the decline of the endangered northern corroboree frog (Pseudophryne pengilleyi), during the most severe drought on record in southern Australia. We documented the local extinction of 42% of P. pengilleyi breeding sites during the climatic extreme. Using logistic regression we investigated habitat variables associated with extinction sites. We found that locally extinct sites now resemble historically absent sites, with fewer pools, less water, and drying-related tree invasion. Extended periods of limited water availability at extinction sites is likely to have restricted breeding, contributing to localised extinctions. Habitat variables recorded at the pool and nest level did not significantly influence P. pengilleyi presence/absence, indicating that site level wetness had an overriding effect. We anticipate that increasing climate variability is likely to disproportionately threaten seasonal pool-breeding amphibian species, exacerbating the global amphibian biodiversity crisis. However, our work with P. pengilleyi suggests there are a range of simple habitat manipulations that could help to ameliorate the impacts.
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Iteroparity is an adaptive response to uncertainty in reproductive success. However, spreading reproductive success over multiple reproduction events during a lifetime is constrained by adult mortality and the stochasticity associated with interactions between external factors and physiological states. The acquisition of information about environmental conditions during the growth of progeny and sufficient resources during the non-reproductive period are key factors for breeding success. Consequently, we hypothesized that long-lived animals may skip a breeding opportunity when information about unfavourable environmental conditions is available. In addition, nutritional constraints could prevent an animal from replenishing its reserves sufficiently to invest in the current breeding period. We investigated these questions using capture-recapture data from a 5-year study on a large population of yellow-bellied toads in a forest in north-eastern France. We took advantage of various advances in multi-state capture-recapture models (e.g. unobservable states and mixture models) to test our hypotheses. Our results show that the combined effects of rainfall deficit and the breeding/non-breeding state of individuals during the past breeding season affect breeding probability during the following breeding opportunity. We also found that females breed less frequently than males, suggesting that the overall energy cost of reproduction differs between genders. Finally, the results indicate that toad survival appears to be negatively influenced by rainfall deficits. We discuss the yellow-bellied toad's reproductive behaviour in term of bet-hedging strategy and life history trait evolution.
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Understanding the processes that lead to species extinctions is vital for lessening pressures on biodiversity. While species diversity, presence and abundance are most commonly used to measure the effects of human pressures, demographic responses give a more proximal indication of how pressures affect population viability and contribute to extinction risk. We reviewed how demographic rates are affected by the major anthropogenic pressures, changed landscape condition caused by human land use, and climate change. We synthesized the results of 147 empirical studies to compare the relative effect size of climate and landscape condition on birth, death, immigration and emigration rates in plant and animal populations. While changed landscape condition is recognized as the major driver of species declines and losses worldwide, we found that, on average, climate variables had equally strong effects on demographic rates in plant and animal populations. This is significant given that the pressures of climate change will continue to intensify in coming decades. The effects of climate change on some populations may be underestimated because changes in climate conditions during critical windows of species life cycles may have disproportionate effects on demographic rates. The combined pressures of land-use change and climate change may result in species declines and extinctions occurring faster than otherwise predicted, particularly if their effects are multiplicative.