Ergon, R. | Search bioRxiv

bioRxiv2022

Microevolutionary system identificationand climate response predictions

Microevolutionary system identification was introduced in Ergon (2022), with the specific purpose to show that predictions of genetic adaptations to climate change require that environmental reference values are properly defined. The theoretical development was then limited to single-input single-output (SISO) systems, and the simulations used a toy example with spring temperature as input and mean breeding date as output. Generations were assumed to be non-overlapping. Here, the theory is extended to cover multiple-input multiple-output (MIMO) systems, while the simulation example uses two environmental inputs (spring temperature and rainfall) and two adaptive phenotypic outputs (breeding date and breeding habitat). These extended simulations reveal difficulties involved in predictions of genetic adaptations for complex systems based on short data, where the reference environment values are not included.

evolutionary biology↗

bioRxiv2022

On the environmental zero-point problem in microevolutionary climate response predictions

It is well documented that individuals of wild populations can adjust to climate change by means of phenotypic plasticity, but few reports on adaptation by means of genetically based microevolution caused by selection. Disentanglement of these separate effects requires that the reference environment (the environmental zero-point) is defined, and this should not be done arbitrarily. The problem is that an error in the reference environment may lead to large errors in predicted microevolution. Together with parameter values and initial mean trait values, the reference environment can be estimated from environmental, phenotypic and fitness data. A prediction error method for this purpose is described, with the feasibility shown by simulations. As shown in a toy example, an estimated reference environment may have large errors, especially for small populations. This may still be a better choice than use of an initial environmental value in a recorded time series, or the mean value, which is often used. Another alternative may be to use the mean value of a past and stationary stochastic environment, which the population is judged to have been fully adapted to, in the sense that the expected geometric mean fitness was at a global maximum. Exceptions are cases with constant phenotypic plasticity, where the microevolutionary changes per generation follow directly from phenotypic and environmental data, independent of the chosen reference environment.

evolutionary biology↗