A recent one, by researchers at Princeton and Columbia, has opened up perspectives into these colorful, exotic Caribbean doorsteps. This study was spearheaded by Oscar Puebla, a former Smithsonian postdoctoral fellow who is now a Research Associate at STRI and a ZMT professor in Germany. That research, which appeared in Science Advances, raises profound implications for how we define species and the intricacies of their evolution.
The study examined dozens of genetic data from 335 hamlet fish and found just one genetic divide among the 19 currently recognized species. This result is surprising and shows that the limits dividing these species may be less clear-cut than once thought. To model fish passing through the cannula, the research team used a new, custom-built underwater camera designed by Floriane Coulmance. This enabled them to carefully map the colors of living fish and pixel by pixel, documenting the incredible visual diversity between and within these species.
Innovative Techniques and Genetic Analysis
It was Coulmance’s underwater camera that made this research possible, providing an unprecedented view of living hamlets and the ability to describe their colors with great accuracy. Such a technological advance opened the door for us to explore the connection between the fish’s color pattern and their molecular patterns. The bright coloration of these village-like habitats made it easier to recognize and identify distinct species. New genetic results are breaking down this perspective and calling into question the rigidity with which we often view species boundaries.
The research team sequenced complete genomes from all 335 fish, which resulted in some surprising finds that go against long-accepted taxonomy. To their surprise, they found that only a single gene seemed to be responsible for the species-defining differences. Martin Helmkampf, senior researcher at ZMT, commented on this surprising result.
“To our surprise, when we looked at the [genetic data], we realized that no [single gene] allows us to reconstruct a family tree for the group.” – Martin Helmkampf
This new revelation makes us rethink the way we classify and think about species in evolutionary biology.
Fluid Boundaries Between Species
The findings from this study suggest that hybridization among species may play a significant role in the evolution of new traits and adaptations. According to Owen McMillan, staff scientist at STRI and co-author on the study, the implications of this fluidity are profound.
“If there is one thing that we’ve learned from our ability to sequence the genomes of many individuals, it’s just how fluid the boundaries are between what we call species.” – Owen McMillan
Hybridization is crucial to fast-tracking evolution. This process is actually not only widespread, but crucial to many organisms, including humans, migratory butterflies, birds and coral reef fishes. He pointed out that this same phenomenon is probably happening among hamlets.
“It is also a way to rapidly evolve new [species], something we see in butterflies, and is probably occurring in hamlets. Of course, this makes sorting things into defined groups challenging, but it is a remarkable testament to how evolution works to create Earth’s biodiversity.” – Owen McMillan
This perspective emphasizes that species definitions may require a more nuanced understanding as hybridization becomes increasingly recognized as a significant factor in evolutionary processes.
Implications for Evolutionary Biology
Those study findings are profound with consequences across the discipline of evolutionary biology. There is just one genetic divide across all 19 species examined. This discovery means that the classic stereotypes for building trees don’t apply to everyone. Helmkampf acknowledged this challenge.
“So, in the end, we have to live with the fact that in some cases it is impossible to reconstruct a [family tree] that differentiates the species.” – Martin Helmkampf
This study calls on researchers to rethink how they approach classification in the midst of biodiversity crises. The classical species concept species are easily observable, separate and distinct entities. This understanding can be an oversimplification, dredging the chasms of their evolutionary pasts.