Shifting lakes, coastlines and mountains: how millions of years of environmental changes shaped the evolution of a little fish

The roles of aridification and sea level changes in the diversification and persistence of freshwater fish lineages

The process of publishing science is a lengthy one – there are many rounds of revisions, assessments, and review required before a paper can be published. With that, I’m very proud to announce that the first paper from my PhD has recently been published in the journal Molecular Ecology. This paper is a collection of a lot of complex analyses, and addressing some relatively complicated biogeographical questions, so I’ve decided to provide a simplified summary here.

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Incomplete lineage sorting through Pachinko – a visual analogy

Reconstructing evolutionary history

Unravelling the evolutionary history of organisms – one of the main goals of phylogenetic research – remains a challenging prospect due to a number of theoretical and analytical aspects. Particularly, trying to reconstruct evolutionary patterns based on current genetic data (the most common way phylogenetic trees are estimated) is prone to the erroneous influence of some secondary factors. One of these is referred to as ‘incomplete lineage sorting’, which can have a major effect on how phylogenetic relationships are estimated and the statistical confidence we may have around these patterns. Today, we’re going to take a look at incomplete lineage sorting (shortened to ILS for brevity herein) using a game-based analogy – a Pachinko machine. Or, if you’d rather, the same general analogy also works for those creepy clown carnival games, but I prefer the less frightening alternative.

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Rebuilding the genomic architecture of evolution

Beyond mutations in the genome

Although genetic variation is, in itself, often considered to be one of the fundamental underpinnings of adaptation by natural selection, it can appear through a number of different forms. Typically, we think of genetic variation in terms of individual mutations at a single site (referred to as ‘single nucleotide polymorphisms’, or SNPs), which may vary in frequency across a population or species in response to selective pressures. However, we’ve also discussed some other types of genetic-related variation within The G-CAT before, such as differential gene expression or epigenetic markers.

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Evolutionary clocks out of sync

Evolutionary time

It shouldn’t come as a surprise to anyone with a basic understanding of evolution that it is a temporal (and also spatial concept). Time is a fundamental aspect of the process of evolution by natural selection, and without it evolution wouldn’t exist. But time is also a fickle thing, and although it remains constant (let’s not delve into that issue here) not all things experience it in the same way.

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Genes in parallel

Adaptation from genetic variation

One of the central themes of this blog, and indeed of evolutionary biology as a whole, is the notion that adaptation is often underpinned by genes. Genetic variation acts as the basis for natural selection to favour or disfavour traits: while this is directly through phenotypic traits (e.g. fur colour, morphology, behaviour), these traits are typically determined by a genetic component. In the early stages of adaptation, evolution can often be observed by changes in the frequency of genetic variants (alleles) within a species or population over time as natural selection acts, gradually leading to the observable (and sometimes dramatic) change in species over time.

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