Across populations or species, life histories can be interpreted as the result of the
optimisation of individual phenotypes, or the development of evolutionarily stable
strategies, with respect to the environment (Stearns 1992). This process should lead
to similar elevation trends within and among species. The greatest variability
among species in organismal design, evolutionary history and ecological niche
enhances the opportunity for differentiation as compared to variation within species,
but these factors also constrain environmental fit proportionally more among species, as detailed below.
11.3.2 Constraints
Body size is one of the most crucial intrinsic constraints to differentiation in life
histories and should always be accounted for when analysing the fit of life histories
to the environment. It engenders a continuum with, at one extreme, large species that
grow slowly, mature late, and live long, and at the other extreme, small species
adopting the opposite strategy (Sibly and Brown 2007). Biological rates, such as
growth rates or reproductive biomass production, tend to obey simple allometric
scaling laws regardless of the living conditions or taxonomic group (Enquist et al.
1999; Laiolo et al. 2015b). Trade-offs in resource allocation among competing
functions foster a second dimension of correlated traits, also known as the ‘slow-fast
life-history continuum’, rooted in the concept of r/K-selection. The cost of reproduction, i.e. the reduction in future reproduction resulting from current investments
in reproduction, is the most prominent trade-off, describing the constraining relationships between growth, survival and reproduction (Reznick 1985; Obeso 2002).
Great allocation in reproduction is associated with fast and short lives even when the
effect of body mass or environment is controlled for, a correlation also defined as the
‘pace-of-life’ syndrome in comparative animal studies (Ricklefs and Wikelski
2002). In plants, vegetative growth is strongly hampered by investment in sexual
reproduction, and is a crucial component of this continuum. Within species, this
trade-off lies beneath the population process of ‘demographic compensation’, or
negative correlations of fitness components across environmental gradients and
towards species’ range margins (Villellas et al. 2015). At margins, vital rates tend to
decline because of poorer conditions of the environment (‘centre-periphery’
hypothesis: Lawton 1993; Vucetich and Waite 2003; Angert and Schemske 2005).
Evolutionary history, relatively unimportant at the intraspecific level, dictates the
options available to selection, with traits of more closely related species responding
more similarly to environmental factors (Harvey and Clutton-Brock 1985).
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P. Laiolo and J.R. Obeso
optimisation of individual phenotypes, or the development of evolutionarily stable
strategies, with respect to the environment (Stearns 1992). This process should lead
to similar elevation trends within and among species. The greatest variability
among species in organismal design, evolutionary history and ecological niche
enhances the opportunity for differentiation as compared to variation within species,
but these factors also constrain environmental fit proportionally more among species, as detailed below.
11.3.2 Constraints
Body size is one of the most crucial intrinsic constraints to differentiation in life
histories and should always be accounted for when analysing the fit of life histories
to the environment. It engenders a continuum with, at one extreme, large species that
grow slowly, mature late, and live long, and at the other extreme, small species
adopting the opposite strategy (Sibly and Brown 2007). Biological rates, such as
growth rates or reproductive biomass production, tend to obey simple allometric
scaling laws regardless of the living conditions or taxonomic group (Enquist et al.
1999; Laiolo et al. 2015b). Trade-offs in resource allocation among competing
functions foster a second dimension of correlated traits, also known as the ‘slow-fast
life-history continuum’, rooted in the concept of r/K-selection. The cost of reproduction, i.e. the reduction in future reproduction resulting from current investments
in reproduction, is the most prominent trade-off, describing the constraining relationships between growth, survival and reproduction (Reznick 1985; Obeso 2002).
Great allocation in reproduction is associated with fast and short lives even when the
effect of body mass or environment is controlled for, a correlation also defined as the
‘pace-of-life’ syndrome in comparative animal studies (Ricklefs and Wikelski
2002). In plants, vegetative growth is strongly hampered by investment in sexual
reproduction, and is a crucial component of this continuum. Within species, this
trade-off lies beneath the population process of ‘demographic compensation’, or
negative correlations of fitness components across environmental gradients and
towards species’ range margins (Villellas et al. 2015). At margins, vital rates tend to
decline because of poorer conditions of the environment (‘centre-periphery’
hypothesis: Lawton 1993; Vucetich and Waite 2003; Angert and Schemske 2005).
Evolutionary history, relatively unimportant at the intraspecific level, dictates the
options available to selection, with traits of more closely related species responding
more similarly to environmental factors (Harvey and Clutton-Brock 1985).
258
P. Laiolo and J.R. Obeso