**2.1.2 Reproductive biology and phenology**

The increase of temperature and thermal variation are the basic signal for emergence and reproduction in anurans, particularly in species from temperate zone (Duellman & Trueb, 1986; Jorgensen, 1992). Climate change linked with other factors such as photoperiod (Pancharatna & Patil, 1997) may affect the breeding patterns of amphibians. Amphibians in Canada are affected by the precipitation decrease and increased temperatures during summer (Herman & Scott, 1992; Ovaska, 1997). In The United Kingdom there has been evidence of early oviposition in *Bufo calamita*, *Rana sculenta* and *Rana temporaria* between 1978 and 1994, which is correlated with the increase of spring temperatures during the last 20 years (Beebee, 1995; Forchhammer et al., 1998). Also, an earlier beginning in the oviposition period (2 to 13 days between 1846 and 1986) in *Rana temporaria* in Finland has been recorded and correlated to changes in air and water temperature (Terhivou, 1988). Historical and recent climate data from Ithaca, New York suggest that the temperature rising during the 20th century has changed the matting patterns of *Pseudacris crucifer*, *Lithobates sylvaticus*, *Lithobates catesbeianus*, and *Hyla versicolor*, by promoting the vocalization behavior for 10 to 13 days earlier than the expected from historical data (Gibs & Breisch, 2000).

In addition, it has been proposed that the change in precipitation patterns (Duellman & Trueb, 1985) can affect the reproductive phenology of amphibian species that breed in ponds. If ponds are filled latter in the season, then the short water permanence should lead to an increase in competition and a higher predation rate. Meanwhile organisms are concentrated in the remaining ponds and they are more vulnerable diseases outbreaks. Changes on amphibian's phenology could present complex effects over populations, changing the population structure, and then a rapid decline of sensitive populations (Donelly & Crump, 1998).

#### **2.1.3 Distribution**

It has been suggested that climate change is the cause of species migration to higher altitudes and latitudes, and then the subsequent shrinkage or loss of amphibian populations and distribution (Pounds et al., 1997). Exploring the relationship between current amphibian distribution and the possible effects of global warming on species distribution in order to build distribution models based on different algorithms such as GARP or MAXENT (Stockwell & Peters, 1999), neural networks, and generalized lineal models (Thuiller, 2003), It would possible to model for the basic conditions for the species to survive. General models of amphibians in Europe suggest that a large portion of species could expand its distribution along Europe if they are able to disperse unlimited, but if species are not capable to disperse, the distribution range of most of the species could be drastically reduced. This scenario could be the most likely because the current levels of habitat fragmentation and degradation, especially in the aquatic habitats. According to the projections of Araujo et al. (2006) the majority of the amphibian species from Europe could lost most of their distribution areas for 2050. This supports the hypothesis that climate

Effects of Climate Change in Amphibians and Reptiles 167

reduction of the ozone layer and higher doses of UV-B radiation (Stebbins, 1995). A deeper water column can reduce UV-B radiation, but in sites/localities with decreased rainfall per year, and the subsequent shallowness of ponds or streams an increase in the embryos exposure to UV-B radiation is expected. In the Pacific Northwest an outbreak of *Saprolegnia ferax* was described as the cause of extensive mortality of *Bufo boreas* embryos in shallow waters, also the exposition to higher levels of UV-B radiation causes that amphibian embryo more sensitive to infection by pathogens (Blaustein et al., 1994b; Kiesecker et al., 1995;

In spite of this, it has be found significant variation among species in the activity levels of photolyaze, an enzyme that repairs DNA for damage caused by UV-B radiation (Hays et al., 1996). The hypothesis of UV-B radiation sensitivity predicts: 1) Significant differences between species of amphibians in relation to the photolyaze repair activity in eggs, and differential success between clutches exposed to solar radiation, 2) a correlation of these differences to the extent of exposure of eggs to sunlight, and 3) high-repair activity in species that are not in decline compared with those declining. Blaustein et al. (1994b) reviewed 10 species of amphibians in Oregon. The enzyme activity was higher in species that are not declining and low in declining species. Field experiments showed that in *Hylla regilla* embryos, a species that is not in decline had high activity of photolyaze with higher clutch success, differing from two species in decline (*Rana cascadae* and *Bufo boreas*) with low

Kiesecker et al., 2001; Laurance et al., 1996; Pounds et al., 1994; Pounds, 2001).

**2.1.6 Other climatic variables and their influence on amphibian's declines** 

It has been suggested that the cause of exposures of amphibian embryos to UV-B is not the thinning of the ozone layer, but the unusual weather patterns such as high temperatures, which is linked with the assumption that the increasing frequency and intensity of El Niño Southwester Oscillation (ENSO) phenomenon as a result of climate change, inducing a high embryo mortality in the Pacific Northwest amphibians (Kiesecker & Blaustein 1997, 1999). In extremely dry and warm years a large proportion of the oviposition sites of *B. boreas* recorded very low levels of water depth, causing that aquatic habitats provide few protection against UV-B. In shallow water (20 cm.) filaments of *S. ferax* attack up to 80% of the embryos on average compared to 12% at 50 cm of water depth. Otherwise, the exposure of organisms to extreme temperatures may be an alternative explanation for the increased mortality of amphibian embryos in shallow waters (Pounds, 2001). The alteration of precipitation patterns may be related to the occurrence of ENSO, in this way, the increased frequency and magnitude of this phenomenon can increase the incidence and severity of *S.* 

In addition to the evidence mentioned above there are some other hypothesis that predicts the highlands clime alteration by the rise of temperature in the sea surface due the evaporation increase sea surface in the tropics, this trend accelerates the atmospheric warming of the nearby highlands (Graham, 1995). One of these scenarios is "weather-related outbreaks" (Pounds & Crump, 1994), which predicts that the host parasite relationships are affected by climate, so amphibian mass extinctions in forests areas that apparently have no significant disruption could be evidence of how deep and unpredictable climate change result of warming sea surface alter the ecological interactions and generates potentially devastating effects. The case of the Harlequin Frog (*Atelopus varius*) could be considered under this situation. As climate increased since 1983 in the localities when this frog was

levels of photolyaze activity (Blaustein et al., 1994b).

*ferax* outbreaks (Kiesecker & Blaustein, 2001).

change will cause the future decline of amphibian's populations. As an example, the pletodontid salamanders of the central highlands of Mexico *Pseudoricea leprosa* and *P. cefalica* could face important levels of habitat loss for the increased rise of temperature. Models predict that *P. leprosa* could possible loss the 75% of its distribution range for the year 2050 (Parra-Olea et al., 2005). These salamanders have limited dispersal behavior; so on they must face the loss in its distributional range in situ (Easterling et al., 2000; Mc Carty, 2001).

#### **2.1.4 Synergy with biotic and abiotic factors (diseases, infections and physiological performance)**

It is clear that the amphibians survival is linked to abiotic factors such water availability, the increase in temperature (Pouns et al., 1999; Pounds, 2001), and the increase in cloud cover (Pounds, 2006) could alter weather patterns and hydrology of the places when amphibians inhabit. The association of this factors with the exposure to higher doses of UV-B radiation due the thinning of the ozone layer (Kiesecker et al., 1995), and the interaction with biotic (diseases and infections), and physiological performance (immune system and tolerances thresholds) could be the main precursors of the events that cause widespread mortality in amphibians and the decline of their populations.

The emergence of disease and infections outbreaks due climate change is related with the decline of several amphibian species (Pounds, 2006). The link between climate change and the coming out of epidemics in amphibians and their subsequence decline has been attributed to the changes in environmental conditions that enhance outbreaks (Pounds & Crump, 1994; Pouns & Puschendorf, 2004). As temperature increases amphibians can exceed their physiological tolerance limits, therefore pathogens could reach their suitable thresholds, and outbreaks should be suited with faster dispersion at high temperatures (Epstein, 2001; Harvel et al., 2002; Rodo et al., 2002). A significant association between rises of local temperature (until thermal optimum levels) with occurrence of chytridiomycosis outbreaks in temperate zones has been described (Bosch et al., 2007). In the Peruvian Andes, the ponds originated by the water of the melting glacial retreat are colonized by three species of frogs *Pleurodema marmorata*, *Bufo spinulosus*, and *Telmatobius marmoratus*, and subsecuenty by the pathogen *Batrachochytridium dendrobatidis* (*Bd*), which possibly causes dead in the adults and declines in metamorphic juveniles and tadpoles. The *Bd* outbreak could be related with the rise of temperature in the ponds, with a subsequent achieve of the tolerable levels by *Bd* (Seimon et al., 2007). Therefore, the amphibian decline are consequence of a complex multifactorial processes that are related with host and parasites, since there is a synergic effects in life histories of hosts and parasites, because both are influenced by the same factors: humidity and temperature (Lips et al., 2008).

#### **2.1.5 Thinning of the ozone layer and UV-B radiation**

It has been suggested that climate change can work in synergy with the ozone layer reduction to increase the exposure of organisms to UV-B radiation (Blustein et al., 1994a, 1998; Schindler et al., 1996; Yan et al., 1996). Worrest & Kimeldorf (1976) found that high levels of UV-B radiation (290-315nm) cause developmental abnormalities and mortality in *Bufo boreas* tadpoles before metamorphosis. Therefore amphibians that breed in mountain aquatic habitats such as temporary ponds or lakes can be quite susceptible to increased levels of UV-B radiation. Because amphibian embryos develop in shallow lakes and mountain ponds are often exposed to direct sunlight, and therefore, considering the

change will cause the future decline of amphibian's populations. As an example, the pletodontid salamanders of the central highlands of Mexico *Pseudoricea leprosa* and *P. cefalica* could face important levels of habitat loss for the increased rise of temperature. Models predict that *P. leprosa* could possible loss the 75% of its distribution range for the year 2050 (Parra-Olea et al., 2005). These salamanders have limited dispersal behavior; so on they must face the loss in its distributional range in situ (Easterling et al., 2000; Mc Carty, 2001).

**2.1.4 Synergy with biotic and abiotic factors (diseases, infections and physiological** 

It is clear that the amphibians survival is linked to abiotic factors such water availability, the increase in temperature (Pouns et al., 1999; Pounds, 2001), and the increase in cloud cover (Pounds, 2006) could alter weather patterns and hydrology of the places when amphibians inhabit. The association of this factors with the exposure to higher doses of UV-B radiation due the thinning of the ozone layer (Kiesecker et al., 1995), and the interaction with biotic (diseases and infections), and physiological performance (immune system and tolerances thresholds) could be the main precursors of the events that cause widespread mortality in

The emergence of disease and infections outbreaks due climate change is related with the decline of several amphibian species (Pounds, 2006). The link between climate change and the coming out of epidemics in amphibians and their subsequence decline has been attributed to the changes in environmental conditions that enhance outbreaks (Pounds & Crump, 1994; Pouns & Puschendorf, 2004). As temperature increases amphibians can exceed their physiological tolerance limits, therefore pathogens could reach their suitable thresholds, and outbreaks should be suited with faster dispersion at high temperatures (Epstein, 2001; Harvel et al., 2002; Rodo et al., 2002). A significant association between rises of local temperature (until thermal optimum levels) with occurrence of chytridiomycosis outbreaks in temperate zones has been described (Bosch et al., 2007). In the Peruvian Andes, the ponds originated by the water of the melting glacial retreat are colonized by three species of frogs *Pleurodema marmorata*, *Bufo spinulosus*, and *Telmatobius marmoratus*, and subsecuenty by the pathogen *Batrachochytridium dendrobatidis* (*Bd*), which possibly causes dead in the adults and declines in metamorphic juveniles and tadpoles. The *Bd* outbreak could be related with the rise of temperature in the ponds, with a subsequent achieve of the tolerable levels by *Bd* (Seimon et al., 2007). Therefore, the amphibian decline are consequence of a complex multifactorial processes that are related with host and parasites, since there is a synergic effects in life histories of hosts and parasites, because both are

influenced by the same factors: humidity and temperature (Lips et al., 2008).

It has been suggested that climate change can work in synergy with the ozone layer reduction to increase the exposure of organisms to UV-B radiation (Blustein et al., 1994a, 1998; Schindler et al., 1996; Yan et al., 1996). Worrest & Kimeldorf (1976) found that high levels of UV-B radiation (290-315nm) cause developmental abnormalities and mortality in *Bufo boreas* tadpoles before metamorphosis. Therefore amphibians that breed in mountain aquatic habitats such as temporary ponds or lakes can be quite susceptible to increased levels of UV-B radiation. Because amphibian embryos develop in shallow lakes and mountain ponds are often exposed to direct sunlight, and therefore, considering the

**2.1.5 Thinning of the ozone layer and UV-B radiation** 

**performance)** 

amphibians and the decline of their populations.

reduction of the ozone layer and higher doses of UV-B radiation (Stebbins, 1995). A deeper water column can reduce UV-B radiation, but in sites/localities with decreased rainfall per year, and the subsequent shallowness of ponds or streams an increase in the embryos exposure to UV-B radiation is expected. In the Pacific Northwest an outbreak of *Saprolegnia ferax* was described as the cause of extensive mortality of *Bufo boreas* embryos in shallow waters, also the exposition to higher levels of UV-B radiation causes that amphibian embryo more sensitive to infection by pathogens (Blaustein et al., 1994b; Kiesecker et al., 1995; Kiesecker et al., 2001; Laurance et al., 1996; Pounds et al., 1994; Pounds, 2001).

In spite of this, it has be found significant variation among species in the activity levels of photolyaze, an enzyme that repairs DNA for damage caused by UV-B radiation (Hays et al., 1996). The hypothesis of UV-B radiation sensitivity predicts: 1) Significant differences between species of amphibians in relation to the photolyaze repair activity in eggs, and differential success between clutches exposed to solar radiation, 2) a correlation of these differences to the extent of exposure of eggs to sunlight, and 3) high-repair activity in species that are not in decline compared with those declining. Blaustein et al. (1994b) reviewed 10 species of amphibians in Oregon. The enzyme activity was higher in species that are not declining and low in declining species. Field experiments showed that in *Hylla regilla* embryos, a species that is not in decline had high activity of photolyaze with higher clutch success, differing from two species in decline (*Rana cascadae* and *Bufo boreas*) with low levels of photolyaze activity (Blaustein et al., 1994b).

#### **2.1.6 Other climatic variables and their influence on amphibian's declines**

It has been suggested that the cause of exposures of amphibian embryos to UV-B is not the thinning of the ozone layer, but the unusual weather patterns such as high temperatures, which is linked with the assumption that the increasing frequency and intensity of El Niño Southwester Oscillation (ENSO) phenomenon as a result of climate change, inducing a high embryo mortality in the Pacific Northwest amphibians (Kiesecker & Blaustein 1997, 1999). In extremely dry and warm years a large proportion of the oviposition sites of *B. boreas* recorded very low levels of water depth, causing that aquatic habitats provide few protection against UV-B. In shallow water (20 cm.) filaments of *S. ferax* attack up to 80% of the embryos on average compared to 12% at 50 cm of water depth. Otherwise, the exposure of organisms to extreme temperatures may be an alternative explanation for the increased mortality of amphibian embryos in shallow waters (Pounds, 2001). The alteration of precipitation patterns may be related to the occurrence of ENSO, in this way, the increased frequency and magnitude of this phenomenon can increase the incidence and severity of *S. ferax* outbreaks (Kiesecker & Blaustein, 2001).

In addition to the evidence mentioned above there are some other hypothesis that predicts the highlands clime alteration by the rise of temperature in the sea surface due the evaporation increase sea surface in the tropics, this trend accelerates the atmospheric warming of the nearby highlands (Graham, 1995). One of these scenarios is "weather-related outbreaks" (Pounds & Crump, 1994), which predicts that the host parasite relationships are affected by climate, so amphibian mass extinctions in forests areas that apparently have no significant disruption could be evidence of how deep and unpredictable climate change result of warming sea surface alter the ecological interactions and generates potentially devastating effects. The case of the Harlequin Frog (*Atelopus varius*) could be considered under this situation. As climate increased since 1983 in the localities when this frog was

Effects of Climate Change in Amphibians and Reptiles 169

common and broad distributed species with numerous sub-populations which are less threatened (Davies et al., 2000). Endemic species use to have unique environmental specializations, and the possibility of losing them could be higher (Grimm, 1993). It is predicted that populations of amphibians at the edges of their distributional ranges may be particularly vulnerable to changes in local and global climate (Pounds and Crump, 1994; Wyman, 1990). Therefore anurans assemblages may be dominated by species with wide ranges of ecological and physiological tolerance. Also, if weather patterns changes, some regions may be affected by the decreasing in the abundance of terrestrial invertebrates (basic diet of amphibians; Blaustein & Kiesecker, 2002; Bradford, 2002; Kiesecker & Blaustein 1997a). Populations also could be affected by changes in births, mortality, emigration, and immigration rates. This can alter the operational sex ratio, age-population structure, and genetic variability. If the population size declines, the young frogs can grow more slowly

I has been speculated that terrestrial frogs of the dry zones of the world could be forced to use the fewer wet areas available, consequently this large aggregations would propitiate higher contact between individuals and thus more vulnerability to parasites and predators, as has been demonstrated for *Atelopous varius* in Costa Rica (Pounds & Crump, 1987). Species with continuous reproductive cycle may experience a reduction of the breeding season, restricting the oviposition to wet periods only. In environments with unpredictable rainfall patterns, the frogs may experience hard times locating the adequate ponds for their larvae, and therefore populations of these species could decline more rapidly (Alford &

To understand the relationships between the biotic and abiotic factors causing the amphibians decline must be considered five evolutionary principles: 1) the development is limited by historical constraints, 2) not all evolution is adaptive, 3) the adaptations are often linked through trade-offs, 4) the development could only alter existing variations, and 5) the evolution takes a lot of time! Therefore, in an evolutionary context although amphibians have been exposed to sunlight and UV-B radiation through its evolutionary history, by now they are facing an unprecedented situation that put them at risk (Cockell, 2001). For example behavior, morphology, and lifestyles that have enabled them to persist for millions of years, today could be highly risky because exposure to sunlight involves receive high doses of UV-B radiation that cause mutations and cell death, decrease growth rates, disable the immune system (Trevini, 1993). Thus in the context described above, the exposure to UV-B radiation can be especially harmful to those species in which natural selection shaped behavioral strategies necessarily exposed to relatively high doses of solar radiation (e.i. species they have to put their eggs in water). In addition, many other selection pressures (biotic and abiotic) are intense and relatively new (i.e. chemical pollution, disease, etc.). Although these might cause a relatively rapid change in some populations, while other threats such as the emergence of infectious diseases combined with environmental changes can be so intense that amphibians cannot adapt to them (Kiesecker & Blaustein, 1997b). Since not all evolution is adaptive, as showed the evidence that in several species of amphibians still lay their eggs in shallow water and communal masses, exposing them to potentially harmful agents such as UV-B, exposure to temperatures that exceed their tolerance limits and conditions (Romer, 1968). Such behavior probably has persisted over millions of years, but under current

than adults and reduce the energy allocated to reproduction (Stearns, 1992).

Richards, 1999; Berven & Grudzien 1990; Gulve, 1994; Sjogren, 1991).

**2.1.9 Climate change and possible evolutionary adaptations of amphibians** 

distributed, the increased of vulnerability to this frogs to lethal parasites also increased, with the subsequent loss of several populations of this frog (Crump & Pouns, 1985, 1989). Finally it has been suggested that as the habitat dries up and frogs gather near the available waterfalls, the probability of being attacked and infected by parasites increase, resulting in high mortality (Pounds et al., 1999).

### **2.1.7 Increased cloud cover**

The Chytridio fungus pathogen is distributed from the deserts, rain forests in the lowlands to the cold mountains enviroments (Ron, 2005). It is consider as a non-lethal saprophyte parasite (Daszak et al., 2003, Retallick et al., 2004), which grows in the amphibian skin (Berguer et al., 2004; Piotrwski et al., 2004). However this fungus has become more common recently, with an increase of lethal records in places with low climate temperatures (Daszak et al., 2005; La Marca et al., 2005). This pathogen has been associated with amphibian mortality in upland regions even during winter (Alexander & Eischeid, 2001; Berguer et al., 2004). The global warming has been considered as a key factor in the spread of the *Bd*, and then the decline of amphibian populations, because of the sequence of events that propitiate the parasite development (altering the local temperature though the effect of changing ambient humidity and light) causing favorable conditions for the fungus growth and propagation.

Linked with the increase of the fungal infection, it is important to understand how environmental changes affect the immune system of amphibians. Environmental temperatures have a large effect on amphibians' immune system, and this is an important factor that makes them more susceptible to the emergence of pathogens (Carey et. al., 1999; Maniero & Carey, 1997; Rojas et al., 2005). The effects of temperature on the amphibian susceptibility to the outbreaks caused by the *Bd* fungus, which causes high mortality at low temperatures is a basic research issue that should be addressed to understand interactions between amphibian decline and climate change (Berguer et al. 2004; Woodhams et al., 2003). Immunity in ectotherms organisms depends on temperature, which can be decisive for the dynamics of disease in amphibians, especially in temperate regions. Seasonal changes in temperature can cause short-term decrease in optimal levels of immunity, causing a drop in the production of immune system cells during these periods until the organisms achieve to adapt as predicted by the hypothesis of the delay and the hypothesis of seasonal acclimatization (Raffel et al., 2006).

As an example, the Red-Spotted Newt (*Notophthalmus viridescens viridescens*) shows considerable variation at their basal levels in different immune parameters (lymphocytes, neutrophils and eosinophils) when they are affected by significant thermal variation. These findings suggest that temperature variability causes an increase in the susceptibility of amphibians to infection, and this has important implications for the emergence of diseases. The effects of delay and acclimatization may also cause infections after the unusual climate change, or could turn the evolution of parasites life-history strategies to take advantage of periods where host are more susceptible. Finally the increased variability of weather conditions predicted by the climate change scenarios could lead to longer or more frequent periods of immune suppression in amphibians which may increase their decline (Hegerl et al., 2004; Schar et al., 2004).

#### **2.1.8 Consequences of climate change on the ecology of amphibians**

It has been suggested that the climate change and its interaction with several factors could easily cause the disappearance of rare, endemic, and isolated species compared with

distributed, the increased of vulnerability to this frogs to lethal parasites also increased, with the subsequent loss of several populations of this frog (Crump & Pouns, 1985, 1989). Finally it has been suggested that as the habitat dries up and frogs gather near the available waterfalls, the probability of being attacked and infected by parasites increase, resulting in

The Chytridio fungus pathogen is distributed from the deserts, rain forests in the lowlands to the cold mountains enviroments (Ron, 2005). It is consider as a non-lethal saprophyte parasite (Daszak et al., 2003, Retallick et al., 2004), which grows in the amphibian skin (Berguer et al., 2004; Piotrwski et al., 2004). However this fungus has become more common recently, with an increase of lethal records in places with low climate temperatures (Daszak et al., 2005; La Marca et al., 2005). This pathogen has been associated with amphibian mortality in upland regions even during winter (Alexander & Eischeid, 2001; Berguer et al., 2004). The global warming has been considered as a key factor in the spread of the *Bd*, and then the decline of amphibian populations, because of the sequence of events that propitiate the parasite development (altering the local temperature though the effect of changing ambient humidity

Linked with the increase of the fungal infection, it is important to understand how environmental changes affect the immune system of amphibians. Environmental temperatures have a large effect on amphibians' immune system, and this is an important factor that makes them more susceptible to the emergence of pathogens (Carey et. al., 1999; Maniero & Carey, 1997; Rojas et al., 2005). The effects of temperature on the amphibian susceptibility to the outbreaks caused by the *Bd* fungus, which causes high mortality at low temperatures is a basic research issue that should be addressed to understand interactions between amphibian decline and climate change (Berguer et al. 2004; Woodhams et al., 2003). Immunity in ectotherms organisms depends on temperature, which can be decisive for the dynamics of disease in amphibians, especially in temperate regions. Seasonal changes in temperature can cause short-term decrease in optimal levels of immunity, causing a drop in the production of immune system cells during these periods until the organisms achieve to adapt as predicted by the hypothesis of the delay and the hypothesis of seasonal

As an example, the Red-Spotted Newt (*Notophthalmus viridescens viridescens*) shows considerable variation at their basal levels in different immune parameters (lymphocytes, neutrophils and eosinophils) when they are affected by significant thermal variation. These findings suggest that temperature variability causes an increase in the susceptibility of amphibians to infection, and this has important implications for the emergence of diseases. The effects of delay and acclimatization may also cause infections after the unusual climate change, or could turn the evolution of parasites life-history strategies to take advantage of periods where host are more susceptible. Finally the increased variability of weather conditions predicted by the climate change scenarios could lead to longer or more frequent periods of immune suppression in amphibians which may increase their decline (Hegerl et

It has been suggested that the climate change and its interaction with several factors could easily cause the disappearance of rare, endemic, and isolated species compared with

**2.1.8 Consequences of climate change on the ecology of amphibians** 

and light) causing favorable conditions for the fungus growth and propagation.

high mortality (Pounds et al., 1999).

acclimatization (Raffel et al., 2006).

al., 2004; Schar et al., 2004).

**2.1.7 Increased cloud cover** 

common and broad distributed species with numerous sub-populations which are less threatened (Davies et al., 2000). Endemic species use to have unique environmental specializations, and the possibility of losing them could be higher (Grimm, 1993). It is predicted that populations of amphibians at the edges of their distributional ranges may be particularly vulnerable to changes in local and global climate (Pounds and Crump, 1994; Wyman, 1990). Therefore anurans assemblages may be dominated by species with wide ranges of ecological and physiological tolerance. Also, if weather patterns changes, some regions may be affected by the decreasing in the abundance of terrestrial invertebrates (basic diet of amphibians; Blaustein & Kiesecker, 2002; Bradford, 2002; Kiesecker & Blaustein 1997a). Populations also could be affected by changes in births, mortality, emigration, and immigration rates. This can alter the operational sex ratio, age-population structure, and genetic variability. If the population size declines, the young frogs can grow more slowly than adults and reduce the energy allocated to reproduction (Stearns, 1992).

I has been speculated that terrestrial frogs of the dry zones of the world could be forced to use the fewer wet areas available, consequently this large aggregations would propitiate higher contact between individuals and thus more vulnerability to parasites and predators, as has been demonstrated for *Atelopous varius* in Costa Rica (Pounds & Crump, 1987). Species with continuous reproductive cycle may experience a reduction of the breeding season, restricting the oviposition to wet periods only. In environments with unpredictable rainfall patterns, the frogs may experience hard times locating the adequate ponds for their larvae, and therefore populations of these species could decline more rapidly (Alford & Richards, 1999; Berven & Grudzien 1990; Gulve, 1994; Sjogren, 1991).

#### **2.1.9 Climate change and possible evolutionary adaptations of amphibians**

To understand the relationships between the biotic and abiotic factors causing the amphibians decline must be considered five evolutionary principles: 1) the development is limited by historical constraints, 2) not all evolution is adaptive, 3) the adaptations are often linked through trade-offs, 4) the development could only alter existing variations, and 5) the evolution takes a lot of time! Therefore, in an evolutionary context although amphibians have been exposed to sunlight and UV-B radiation through its evolutionary history, by now they are facing an unprecedented situation that put them at risk (Cockell, 2001). For example behavior, morphology, and lifestyles that have enabled them to persist for millions of years, today could be highly risky because exposure to sunlight involves receive high doses of UV-B radiation that cause mutations and cell death, decrease growth rates, disable the immune system (Trevini, 1993). Thus in the context described above, the exposure to UV-B radiation can be especially harmful to those species in which natural selection shaped behavioral strategies necessarily exposed to relatively high doses of solar radiation (e.i. species they have to put their eggs in water). In addition, many other selection pressures (biotic and abiotic) are intense and relatively new (i.e. chemical pollution, disease, etc.). Although these might cause a relatively rapid change in some populations, while other threats such as the emergence of infectious diseases combined with environmental changes can be so intense that amphibians cannot adapt to them (Kiesecker & Blaustein, 1997b). Since not all evolution is adaptive, as showed the evidence that in several species of amphibians still lay their eggs in shallow water and communal masses, exposing them to potentially harmful agents such as UV-B, exposure to temperatures that exceed their tolerance limits and conditions (Romer, 1968). Such behavior probably has persisted over millions of years, but under current

Effects of Climate Change in Amphibians and Reptiles 171

2006). According to the author's records individual body size increases dramatically in four populations studied for 18 years. Body size increase in all age classes appears to be associated with an increase in temperature experienced by the offspring in their first month of life (August). The maximum daily temperature in this region during August raised 2.2 °C and lizard snout-vent length increased over 28%. As a result, body size of adult females increased dramatically, with the following increase of the litter size and the reproductive effort. One of the populations surveyed by a capture-recapture study suggested that adult survivorship was correlated with May temperature. All the fitness components investigated responded positively to increase in temperature, so it can be concluded *Lacerta vivipara* has obtained benefits of climate change. Instead, it is possible that climate change drastically alters the marshes, the main habitat for the *Lacerta vivipara*, due to temperature increase could cause more evaporation and reduces its moisture (IPCC, 2001), and the species may not be able to cope with changes in their habitat. (Chamaillé-Jammes et al., 2006). Araujo et al. (2006) also suggest that a continuous increase in temperature could cause a long-term contraction in suitable habitat for lizards and therefore increase the risk of local extinction.

Global warming and the potential reduction in areas with suitable characteristics for the distribution of the lizard *Heteronotia binoei* was calculated the climate component of their fundamental niche through physiological measurements (thermal requirements for egg development, thermal preferences, and thermal tolerances). The environmental data analyzed was high-resolution climate data from Australia (air temperature, cloud cover, wind speed, humidity, radiation, etc.), and biophysical models projecting over the Australian subcontinent to predict the effects of global warming. Estimates predict relatively little effect on the maintenance of metabolic costs, mainly due to the buffering effect of thermoregulatory behavior of lizards. The lizards could be able to regulate their body temperature (and their metabolic rates) moving between thermally suitable places at the surface (shuttling), as has been shown for the nocturnal ectotherms, and other diurnal lizards like *Psammodroums algirus* in the Mediterranean region of Spain (Diaz & Cabezas-Díaz, 2004; Kearney & Predavec, 2000). On the other hand, lizards also should evade high thermal environments hiding in shelters in the hottest hours of day (Kearney, 2002), and changing their daily and stationary activity periods (Bawuens et al., 1996), and their habitat

Climate change is a threat to reptile populations due that in some lineages the temperature experienced by embryos during incubation determines the offspring sex ratio. Increases or decreases of temperature could turn to bias in the proportion of the clutch toward one sex. Nests exposed to an increase heat produced dramatic differences in sex ratios compared to those placed in shaded sites (Doody et al, 2004; Janzen & Morjan, 2001; St. Juliana et al., 2004). For this reason reptiles can useful as indicators of biological impact due global warming (Janzen & Paukstis, 1991; Mrosovky & Provancha, 1992). For example, related studies has been conducted in North America with the loggerhead turtle (*Caretta caretta*); results suggest that organisms could alter their nesting behavior as adaptive mechanism to the warming of historical nesting sites, that range from southeastern Florida to southeastern

**2.2.3 Thermoregulatory behavior and global warming** 

**2.2.4 Effects of climate change on reproductive biology of reptiles** 

selection (Stevenson, 1995).

conditions these behaviors may cause the damage by a large number of elements such as those mentioned above. Amphibians exhibit maladaptive characteristics because the evolution takes time. Obviously, amphibians, and other organisms have defenses against the harmful factors. Exposure to sunlight over evolutionary time has undoubtedly resulted in mechanisms that help animals to withstand UV-B radiation (Cockel, 2001; Hoffer, 2000).
