Ecology. Michael Begon

Ecology - Michael  Begon


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Graphs depict the exponential effects of temperature on metabolic reactions. (a) The rate of oxygen consumption of the Colorado beetle, which doubles for every 10°C rise in temperature up to 20°C, but increases less fast at higher temperatures. (b) Relationship between resting oxygen consumption of teleost fish, plotted for a variety of species as oxygen consumption at their typical environmental temperature for a standardized 50 g fish. (c) Q10 values for oxygen consumption of various invertebrate and vertebrate animal taxa, averaged across multiple published studies.

      Source: (a) After Marzusch (1952). (b, c) Data compiled from various sources by Clarke (2017).

      effectively linear effects on rates of growth and development

Graphs depict effectively linear relationships between rates of growth and development and temperature. (a) Growth of the protist Strombidinopsis multiauris. (b) Egg development in the beetle Oulema duftschmidi. (c) Egg to adult development in the mite Amblyseius californicus. The vertical scales in (b) and (c) represent the proportion of total development achieved in one day at the temperature concerned.

      Source: (a) After Montagnes et al. (2003). (b) After Severini et al. (2003). (c) After Hart et al. (2002).

      day‐degree concept

      When the relationship between growth or development is effectively linear, the temperatures experienced by an organism can be summarised in a single very useful value, the number of ‘day‐degrees’. For instance, Figure 2.9c shows that at 15°C (5.1°C above a development threshold of 9.9°C) the predatory mite, Amblyseius californicus, took 24.22 days to develop (i.e. the proportion of its total development achieved each day was 0.041 (= 1/24.22)), but it took only 8.18 days to develop at 25°C (15.1°C above the same threshold). At both temperatures, therefore, development required 123.5 day‐degrees (or, more properly, ‘day‐degrees above threshold’), i.e. 24.22 × 5.1 = 123.5, and 8.18 × 15.1 = 123.5. This is also the requirement for development in the mite at other temperatures within the non‐lethal range. Such organisms cannot be said to require a certain length of time for development. What they require is a combination of time and temperature, often referred to as ‘physiological time’.

      temperature–size rule

Graphs depict the temperature–size rule. (a) Reduction in protist cell volume with increasing rearing temperature. The vertical scale measures the proportional change from cell volume at 15°C. (b) Maximal size of 74 fish species generally declines across a steep temperature gradient in the Mediterranean Sea. The figure presents the best model based on the whole dataset, plotting percent of maximum size observed with an increase in maximum sea surface temperature of up to 5°C.

      Source: (a) After Atkinson et al. (2003). (b) After van Rijn et al. (2017).

      These links can equally be seen from the viewpoint of how metabolism co‐varies with temperature and size. We pick this up again in Section 3.9 when we look at the so‐called metabolic theory of ecology.


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