non-egg guarding, highly fecund fish with small eggs and late maturity were more
frequent in environments with high mean annual temperature and temporary flow.
This pattern indicates that it may be advantageous to increase parental care or
produce fewer but larger eggs in low-temperature stream heads, as also observed in
crustaceans. Another consistent intraspecific pattern with temperature is that of
longevity, which declines at increasing temperatures (Pauly 1980; Beverton 1987).
Many fish species continue somatic growth after sexual maturation and growth is
typically highly plastic (Gotthard 2001). However, there is evidence that developmental decisions and growth patterns of populations are locally adapted (Nicieza
et al. 1994; Haugen and Vøllestad 2000) and respond to climate, for instance, along
latitudes, in a countergradient fashion as for other ectotherms (Conover and Present
1990).
11.4.3 Amphibians
Juvenile development to metamorphosis or sexual maturity strongly influences
amphibian adult fitness and has been the target of a large number of studies along
climate gradients (Berven and Gill 1983; Altwegg and Reyer 2003; Laugen et al.
2003; Muir et al. 2014). These have shown that ontogenetic traits tend to adjust to a
countergradient variation pattern across elevations. Berven et al. (1979) and Berven
(1982) showed, for instance, that the mountain larvae of the green frog (Rana
clamitans) and wood frog (R. sylvatica) complete metamorphosis faster and at a
larger size than their lowland counterparts in a common environment. Despite their
higher genetic growth capacity, however, in nature they metamorphose later
because of strong climatic constraints.
Again, similar to other taxonomic groups, anurans and urodeles from
high-altitudes invest in larger eggs but reduce offspring number (Liao et al. 2014)
and increase mean and maximum age, as well as maturation age (Zhang and Lu
2012). Apart from intrinsic trade-offs, hypoxia has been evoked as a possible cause
of increased longevity in high-altitude regions (Zhang and Lu 2012).
11.4.4 Reptiles
Viviparity in squamate reptiles has been explained in terms of climate selection for
longer periods of egg retention where juvenile mortality is high because of extended
cold exposure (Tinkle and Gibbons 1977). However, this does not apply to the
independent evolution of viviparity in freshwater fishes (Pollux et al. 2009) and
amphibians (Vitt and Caldwell 2013). In viviparous lizards and snakes, gravid
females actively thermoregulate and provide embryos of higher temperatures for
development, a behaviour that reduces juvenile mortality as compared to conditions
in nest regimes (Braña et al. 1991). Viviparity, however, requires modifications to
11 Life-History Responses to the Altitudinal Gradient
263
frequent in environments with high mean annual temperature and temporary flow.
This pattern indicates that it may be advantageous to increase parental care or
produce fewer but larger eggs in low-temperature stream heads, as also observed in
crustaceans. Another consistent intraspecific pattern with temperature is that of
longevity, which declines at increasing temperatures (Pauly 1980; Beverton 1987).
Many fish species continue somatic growth after sexual maturation and growth is
typically highly plastic (Gotthard 2001). However, there is evidence that developmental decisions and growth patterns of populations are locally adapted (Nicieza
et al. 1994; Haugen and Vøllestad 2000) and respond to climate, for instance, along
latitudes, in a countergradient fashion as for other ectotherms (Conover and Present
1990).
11.4.3 Amphibians
Juvenile development to metamorphosis or sexual maturity strongly influences
amphibian adult fitness and has been the target of a large number of studies along
climate gradients (Berven and Gill 1983; Altwegg and Reyer 2003; Laugen et al.
2003; Muir et al. 2014). These have shown that ontogenetic traits tend to adjust to a
countergradient variation pattern across elevations. Berven et al. (1979) and Berven
(1982) showed, for instance, that the mountain larvae of the green frog (Rana
clamitans) and wood frog (R. sylvatica) complete metamorphosis faster and at a
larger size than their lowland counterparts in a common environment. Despite their
higher genetic growth capacity, however, in nature they metamorphose later
because of strong climatic constraints.
Again, similar to other taxonomic groups, anurans and urodeles from
high-altitudes invest in larger eggs but reduce offspring number (Liao et al. 2014)
and increase mean and maximum age, as well as maturation age (Zhang and Lu
2012). Apart from intrinsic trade-offs, hypoxia has been evoked as a possible cause
of increased longevity in high-altitude regions (Zhang and Lu 2012).
11.4.4 Reptiles
Viviparity in squamate reptiles has been explained in terms of climate selection for
longer periods of egg retention where juvenile mortality is high because of extended
cold exposure (Tinkle and Gibbons 1977). However, this does not apply to the
independent evolution of viviparity in freshwater fishes (Pollux et al. 2009) and
amphibians (Vitt and Caldwell 2013). In viviparous lizards and snakes, gravid
females actively thermoregulate and provide embryos of higher temperatures for
development, a behaviour that reduces juvenile mortality as compared to conditions
in nest regimes (Braña et al. 1991). Viviparity, however, requires modifications to
11 Life-History Responses to the Altitudinal Gradient
263