The diversity of life on Earth has always bewildered scientists!
My scientific interest is driven by fascination and urge to document and understand this diversity.
In my PhD I studied evolutionary processes leading to differentiation, adaptation and speciation with particular focus on hybridization.
It is mesmerizing that, as the genomic data accumulates, we learn that hybridization is commonplace in the natural world; however, it is still largely unknown what role it plays in evolution. Is the genetic material exchanged between species important for their overall genetic variation, adaptation and diversification? Or is it removed from the genomic regions under selection and kept only in neutral/evolutionarily unimportant regions (if we can define such regions at all, when omnigenic models suggest that every piece of genetic background contributes to the phenotype in some way)? Is hybridization actually detrimental to species and if so why sexual selection hasn’t eliminated it so far? These are general questions that are on my mind daily.
In my PhD research I had tremendous luck to work on one of the very few documented cases of speciation fueled by hybridization in the animal kingdom – the Cottus fish. In this system, a young lineage of hybrid origin has successfully invaded, persisted and formed its own reproductively isolated population in a new environment, previously uninhabited by neither of the parental species. Due to this amazing feat we call this lineage the “invasives”. While the parental species are limited to summer-cold streams, the invasives colonized downstream areas of rivers that are more exposed to sunlight and significantly warmer in the summer. This suggests that hybrid Cottus have adapted to a new ecological niche coarsely related to temperature.
My goal is to investigate what is the nature of this rapid local adaptation.
Annual cycle of local adaptation in an emerging hybrid species
Since ecology is thought to play crucial role in the emergence of homoploid hybrid species, sampling phenotypic variation in the appropriate ecological context is key to understand evolutionary processes shaping the system.
I perform an extensive comparative transcriptomic study on parental species and the hybrid lineage sampled straight from the natural environment. I use RNASeq to compare transcriptomic profiles of wild fish over the course of one complete year – sampling that provides me with a detailed picture of phenotypic differentiation taking place in nature. I found that different clusters of genes contribute to the differentiation of hybrids from parental species in different seasons. Many genes follow changes in temperature, however, the data suggest that much of the differentiation between invasive Cottus and their parent is not related to temperature.
Further I am complementing this work by sampling of transcriptomes from fish raised under controlled laboratory conditions. This allows me to uncover the adaptive, heritable component of invasives phenotype. I found clusters of genes with high heritability to be enriched for metabolism-related GO terms, which suggests that the hybrid lineage might have altered metabolism.
Ecologically relevant transgressive traits in a young hybrid species
Recombination of parental alleles in the hybrid lineage…
can result in phenotypes lying outside of the normal parental range – called “transgressive”. Those in turn might increase hybrid’s fitness in the new ecological niche and therefore transgressive trait expression in the hybrids is thought to play an important role in the homoploid hybrid speciation process.
In this project I examine transcriptomes of fish raised in common-garden conditions to identify invasive-specific transgressive transcriptomic traits in invasive Cottus. Further I verify if the expression profiles remain differentiated in the natural contact zone of one of the parental species and the invasives.
I found that invasives transgressive traits were enriched for up-regulated genes and their expression patterns were largely conserved in nature. Transgressive traits were representing mostly GO terms connected to primary metabolic processes, which suggest possible adaptation through altering the metabolic rate. Additionally I identified a transgressive gene possibly involved in widening vision in the red light, which might constitute an adaptation to murky waters. Those findings unravel new possible avenues for studies on adaptation in Cottus that will demand future functional studies.
Metabolism, ecology and evolution
is well established as an important phenotypic trait, which is tightly linked with ecology. “The Metabolic Theory of Ecology” conceptualized by Brown et al. (2004) links metabolic processes with the ecological processes happening in populations. However, its connection with speciation has not really been considered until now.
Vast number of studies looked at metabolic rate in hybrids and concluded that genetic incompatibilities in hybrids cause decreased metabolic efficiency and low fitness. For instance, incompatibilities in the oxidation-reduction pathway genes resulted in elevated metabolic rate, dysfunction and lowered fitness, ultimately leading to the reinforcement of reproductive barriers between species in the hybrid zone of flycatchers (McFarlane et al. 2016).
But could hybridization also have “positive” effects on metabolism?
I believe that this is very possible and that enhancement of metabolic processes could influence ecological potential of the hybrid lineage allowing invasion of new ecological niche.
In my study I observed that genes related to basic metabolic functions are up-regulated in the invasive lineage of hybrid origin. This might indicate that they have higher metabolic rate and maybe it improves their performance. Whether this is the case and whether it is a result of hybridization remain open questions at this point. Further functional studies are necessary in order to find answers. For that purpose, I propose to study resting metabolic rate – a proxy for metabolic performance – in both parental species and the invasive lineage. Furthermore, I will investigate nucleotide divergence between lineages in the genes coding proteins of the oxidation-reduction chain and testing whether certain parental allele combinations are fixed in the invasives.
I believe that alterations to metabolism can have huge impact on fitness and life history traits of the hybrid lineage. I advocate re-discovering metabolic rate as a trait to study and apply to speciation research cause it is relatively easy to measure and potentially gravely important for individuals fitness. Metabolic rate is a complex trait – defined by the effects of multiple genes acting at the same time – traditionally considered unattractive cause they don’t provide straight answers pointing to one or two specific genes/regions responsible for i.e. disease or adaptation, however, nowadays we have good idea about how complex traits evolve and understand that this is how, oftentimes, evolution progresses.
BSc and MSc research projects
My previous research projects include population genetics of cod fish in the North Sea and the Baltic Sea studied by DNA extracted from fresh tissue samples as well as ancient DNA recovered from otoliths.