Biomathematics & Statistics Scotland
Understanding the limitations on species’ ranges is becoming increasingly important with the onset of global warming, and is the subject of both empirical and theoretical research. Previous work has shown that, when the genetic variance in the trait under selection is too small relative to the (linear) rate of change of the environment in space, the ability of the species to adapt to ever more extreme conditions collapses; instead of adaptation leading to uniform population densities, a species will then have a strictly limited range. As part of an EPSRC-funded collaboration on complexity science we have developed models to explore the impact of environmental changes in time as well as space. Our results show that uniform adaptation can still occur in large spatial domains, but with suppression of population densities in faster-changing environments because the species trait lags behind the environmental optimum. However, where species range is limited even in a static environment, trait adaptation is much slower than environmental change and the population will need to track the environment via migration of individuals to more favourable conditions.
Population density
(ψ) in physical
space (X) and trait
space (Z). When
the environmental
gradient is
shallow (left), local
adaptation causes
the gradient
in average
population trait
to coincide with
the environment,
leading to uniform population densities. When the environmental gradient is steeper
(right), local adaptation can not compensate, leading to variable densities and a restricted
species range.
Further details from: Glenn Marion
