Understanding how organisms adapt to their environment and how they diversify into many different species is a major challenge, and in my opinion, one of the most fascinating topics in evolutionary biology.
The study of evolutionary developmental biology (evo-devo) has provided invaluable contributions to our understanding of the relationship between genotypic and phenotypic change. Similarly, evolutionary ecology has greatly advanced our understanding of the relationship between the phenotype and the environment. Combining both evo-devo and ecological approaches can bring a more comprehensive understanding of the endless diversity present in nature.
To allow integration, models should provide a clear ecological context together with tractability of developmental genetic tools. Both cichlids and semi-aquatic insects are model systems where this integration starts to be achieved, we can combine evolutionary biology and development with the state-of-the-art methods of genome/gene function and fitness assays.
My research has focuses on the evolution and diversification of morphological traits within these two groups of animals – how they are genetically determined, and what are the selective forces that shape it. I use an approach that combines bioinformatics, developmental genetics, ecology and behavioural techniques to address the questions presented.
Genetic basis of a novel and variable pigmentation trait in cichlid fishes
The spectacularly diverse adaptive radiations of cichlid fishes in the East Africa Great Lakes provide an ideal system to study the molecular basis of evolutionary novelties in the context of adaptation and explosive speciation. One characteristic innovation of the most species-rich lineage of cichlids, the haplochromines, is a set of brightly pigmented spots on male anal fins, known as “egg-spots”. Egg-spots are a diverse trait (number, colour and shape), and this trait plays a key role in the territorial and breeding behaviour of around 1,500 species of cichlids. In this project we are studying the genetic and developmental basis underlying the emergence and diversification of this trait.
Cichlids are a very popular system in speciation and adaptive radiation research, although not as popular in developmental biology. The availability of dozens of cichlid species genomes makes it easier to develop functional tools (eg. CRISPR) for cichlids.
With these genomes and with the genetic tools, we can correlate which genetic changes lead to phenotypic changes, and which phenotypic changes impact the ability of the organism to interact with the environment. By addressing this same questions across different timescales (across populations, species and genera) we can address a long-standing question: whether the mechanisms of developmental change are the same at the micro- and macro-evolutionary scale. The multiple radiations of cichlid fishes in the East African lakes provide the ideal model to address this thematic.
Adaptive and genetic basis of a key innovation in Rhagovelia sp.
Here we study the developmental genetics at the origin of a novel trait that was essential for the invasion of a novel environment.
The invasion of novel environments often requires the evolution of key novel traits that will facilitate the exploitation of the new environment. In Rhagovelia sp. (genus of water-walking insects; Heteroptera, Gerromorpha) the evolution of a highly elaborate swimming fan on the tarsus of the propelling mid-legs increases water resistance against leg movements, thereby increasing their propelling function. We showed that this novel trait acted as a key innovation, allowing this group to conquer and diversify on running water surfaces; a niche that is not accessible for most other water-walking insects.
Little is known about the underlying genetic mechanisms and their role in the diversification of the group. We are characterizing the genes and the specific genetic changes that underlie the emergence of the Rhagovelia propelling fan. The function of these genes is tested with functional experimental studies by changing the expression of such genes (RNAi). Finally we manipulate the phenotype (through manipulation of it’s underlying genes) and access how it affects organismal fitness (by competing the knock-down with the wild-type phenotype in a controlled environment). We this approach we will be able to pinpoint which genetic changes lead to phenotypic changes and ultimately which phenotypic changes have a fitness impact on the organism ability to walk on water. This approach is highly innovative, as it will directly connect molecular and developmental changes in a key trait to a measure of fitness.
This research is done in collaboration with Abderrahman Khila.