The Ortiz-Barrientos lab is interested in the genetics and ecology of speciation and adaptation. We have developed a new system of study, the Australian daisy (or the variable groundsel) Senecio lautus to tackle fundamental questions in these fascinating areas of evolutionary biology. Below you can read a brief description of our research interests and the opportunities available for training in the Ortiz-Barrientos lab.

Speciation and adaptation

The ecological and genetic basis of speciation. As populations adapt to new environmental challenges they may become reproductively isolated from such other populations. The genetic changes associated with the evolution of reproductive isolation remain largely unknown, and therefore we have a limited understanding as to how ecology and genetics interact during the origin of new species. In the Ortiz-Barrientos lab we are tackling this problem by studying the early stages of speciation in the S. lautus species complex (sensu lato). Specifically, we are interested in identifying those genes responsibles for hybrid failure under field conditions, and in discovering their function within species. We use a combination of genomic, quantitative and classical genetics, together with reciprocal transplant experiments in our research. 

The genetic basis of parallel evolution. Populations experiencing similar selective pressures may evolve similar traits. As they adapt to similar environments, populations may fix similar alleles, or they might reach a phenotypic solution via different biochemical and genetic routes. In the Ortiz-Barrientos lab we are investigating how maritime populations of S. lautus have repeatedly and independently adapted to constrasting habitats along the Australian coast. We are using population genomic approaches (e.g., using RAD tags) and mapping by selection experiments to identify those genomic regions responsible for the replicated evolution of tall and prostrate forms in S. lautus. We combine these results with the use of Nearly Isogenic Lines to test the adaptive significance of candidate genes under field conditions. 

Experimental evolution.  Direct demonstration for the role of natural selection in the creation of new speciation is rare. Although microbial and unicellular eukaryotic organisms have provided insights as to how speciation occurs, there are very few examples in plants and animals as to how natural selection creates reproductive isolation. in the Ortiz-Barrientos lab we are exploring various strategies to deconstruct species and then to use natural selection to reconstuct them. Using specific quantitative genetic breeding designs together with QTL mapping we are tracking genetic changes that take place as adaptation proceeds and reproductive isolation revolves (e.g., the evolution of immigrant inviability and ecologically dependent postzygotic isolation). Results from these experiments will shed light on the connection between adaptation and speciation, and will help us understand how genetic architectures evolve. 

The genetics of adaptation.  In his famous treatise on natural selection, Ronald A. Fisher argued that "The rate of increase in fitness of any organism at any time is equal to its genetic variance in fitness at that time". The genetic basis of traits contributing to fitness remains largely unresolved, particularly because some times many alleles of small effect control phenotypic variability, and because sometimes traits may evolve in step with other traits. These putative features of genetic architectures and trait evolution make the genetic study of adaptation difficult and impossible in most organisms. In our lab we are using mapping by selection of extreme tails to identify those genes responsible for ecotypic differences, and those traits reponsible for fitness differences in the wild. Further, we are investigating the adpative significance of genetic correlations during ecotypic divergence, and the relative contributions of additive vs. non-additive effects to fitness variation. 

Genomic tools for S. lautus.   The advent of new nucleic acid sequencing and functional genomic technologies is rapidly transforming the experimental landscape in evolutionary biology. In our lab we are rapidly deploying new experimental tools for population and ecological genomic analyses of S. lautus. Specifically, we have recently produced a de novo assembly of both the S. lautus transcriptome and of a large fraction of its gene space. These genomic resources are creating sinergies with other genetic resources developed in the lab. For instance, a large fraction of RAD tags (~80%) produced by other members of the lab can be mapped to this genome space, thus facilitating the execution of population genomic projects. Finally, we are creating a linkage map with more than 2500 markers distributed across the genome of S. lautus which will enable us to study the genetic architecture of species differences, adaptation, and reproductive isolation. 

Developmental genetics of ecologically important traits.  Correlations between traits and habitat suggest that natural selection has been responsible fo their evolution. Here, we are studying the developmental genetics of leaf morphology variation in S. lautus. We are reconstructing genetic pathways invovled in leaf morphology, as well as carrying functional genomic approaches at various developmental stages of leaf development in four different and leaf contrasting ecotypes. We are further performing molecular population genetic analyses in candidate genes for natural variation in leaf morphology in S. lautus.

© Daniel Ortiz Barrientos 2020