Abstracts (first author)
Adaptive dynamics modelling with evolving epigenetics
The term epigenetics is used to cover both the development of phenotypes from genotypes and the existence of alternative epigenetic birth states for a given genotype. If we define genotype-phenotype maps very broadly as the phenotypes and phenotype distributions a genotype can produce, then we can use these to model how an evolutionary dynamics depends on underlying traits and genotypic variation which control apparent phenotype distributions. Such models can then investigate different epigenetic mechanisms simultaneously evolving.
A long-term perspective on fitness and evolutionary dynamics is essential to understand whether an epigenetic architecture is adaptive. I propose to use invasion fitness of mutants and adaptive dynamics approximations to investigate this. For such approximations in models with apparent and underlying traits of individual phenotypes and alleles, expressions for fitness gradients and evolutionary stability criteria are derived. I complement these with tools to investigate models where the apparent traits are life history fitness components such as stage-specific survival probabilities, and probabilities that gametes switch from the epigenetic states of their parental alleles at a certain locus into another. It is shown that a per-generation perspective on the dynamics of populations of mutants is essential to get good insight in the evolutionary dynamics of alternative epigenetic birth states.
A specific example with evolving plastic epigenetic switching and evolving juvenile survival probabilities is worked out to discuss how trans-generational effects of parental birth state could evolve in a given ecological setting. I pay particular attention to the existence of alternative evolutionary outcomes for the same ecology, and to whether randomizing or plastic epigenetic switching strategies are most adaptive.
Giants from dwarfs: support for sympatric processes of size divergence in Austrolebias South-American annual killifishPDF
To determine the plausibility of sympatric speciation, we need to determine its relative rate of occurrence across different speciation events. Here we focus on a small taxonomic group and a particular speciation mechanism which requires sympatry: the emergence of a large and small species pair where the large cannibalizes the small. This scenario has been named “giant-dwarf” diversification. A comparative analysis of body size measures of Austrolebias South-American annual killifish suggests that species evolve towards one of three size optima. Species evolving towards the largest optimal size appeared at least three times from small in the Austrolebias genus. The first large ancestral species per event appeared in a trait change with relatively high speed in all three cases, consistent with expectations of cannibalism evolution. A comparative analysis of lower jaw length, a proxy for the level of specialization in piscivory suggests that in one clade of large species trait values indicate a very weak or no specialization towards piscivory, and that in the two other clades species are selected towards two optima with relatively large jaw lengths. By means of a reconstruction of ancestral species ranges we show that speciation events leading to a large and smaller species pair were sympatric with a large likelihood. For the clade of large species with little specialization, the probability that speciation was non-sympatric is largest among the three events. Conditional on the data we analysed, one can therefore conclude that giant-dwarf speciation by cannibalism most probably occurred twice in Austrolebias and that a third appearance of large species in the genus likely occurred by other selective or non-selective processes.