We have come far in identifying the genetic makeup of traits that underlie adaptation and speciation in various range of organisms. However, many of these studies primarily focus on cases with a relatively simple genetic basis on easily observable traits, which may not fully reflect the complexity found in nature. As an evolutionary biologist, I am enthusiastic about integrating genomics with ecological and experimental work to dissect the genetic and genomic basis of polygenic traits, such as behaviour and crucially its functional follow-up to obtain a more mechanistic understanding of possible biophysical or developmental constraints that lead to the use of particular mutations or genes in adaptation and speciation. To achieve this, I investigate cases involving recent range expansion and colonisation of species that rapidly adapting to novel habitats, capturing snapshots of evolution-in-action.

The rapid environmental changes accelerated by human activities have facilitated the introduction of invasive species worldwide. In this process, many of these species have become extinct, while others have managed to survive but are not considered invasive. However, there are a few that have thrived, gained reproductive success, and spread extensively, thereby altering the local eco-evolutionary dynamics.

For instance, a case in Switzerland demonstrates the rapid and sudden expansion of the range of a native species of wall lizards, Podarcis muralis, within just two decades. Interestingly, the spreading population of lizards does not exhibit the phenotypic characteristics of the native lizards. These phenotypic differences suggest the possibility that the expanding lizards may not representing the native lizards, but rather introduced subspecies or possibly the result of genetic hybridisation between the native lizards and other subspecies whose ranges overlap, such as the Italian lineage and the southern Alps lineages.

While hybridisation often carries a negative connotation due to its homogenising effect on gene pools, recent shifts in understanding have revealed that in certain cases, hybridisation can enrich genetic variation, potentially facilitating rapid routes to adaptation and speciation. As a visiting MSc student of the MEME program at the Sanger Institute, I am utilising these organisms to study the genetic mechanisms that explain why and how a species spreads rapidly.

Moreover, invasive introduced species also have the potential to create new ecological niches for native organisms. During the era of European exploration to the East, Europeans brought numerous seeds and introduced high-value economically and aesthetically significant species beyond their native ranges. Many tropical American plants now thrive in Southeast Asia, primarily due to similar microclimatic conditions. These species present new and challenging obstacles to overcome, but they also have the potential to open up new ecological opportunities for local herbivores.

One example is a phytophagous ladybird beetle species in Southeast Asia that has repeatedly colonised an introduced invasive plant within a relatively short period. Similar colonisation patterns have been observed in other ladybird beetle species within the same tribe. Interestingly, in one case, adaptation to the new habitat has the potential to act as a critical driving force in population divergence or speciation due to host plants specialisation, while in some cases, it leads to generalisation.

Soon, in my PhD at the Sanger Institute in October, I am interested in characterising the evolutionary agents that drive genetic changes in cases of specialisation and generalisation to host plants. I aim to study the genomic features that facilitate these changes during the host plant colonisation process, and trace the origin of genetic variants responsible for the behavioural preferences and adaptations of these beetles to new host plants. More information will be provided soon!

Arif Maulana, Wellcome Sanger Institute

In recent years, I have also been involved in several projects related to the genetic basis of speciation in popular model systems. With Matteo Rossi and Richard Merrill, we have functionally validated the genetic basis of visual mate preference in Heliconius butterflies. Using genome editing, we have knocked out one of the five candidate genes recently found to be strongly associated with preference behaviours across the broader Heliconius clade. In another opportunity, with Marjolaine Rousselle and Carole Smadja, we are investigating the presence, link, and causes of fast-X and large-X effects, exploring the role of sex chromosome evolution in the development of reproductive isolation across the continuum of divergence using various pea aphid, Acyrthosiphon pisum, host-specialised biotypes.

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