Une étude d'ADN révèle des pertes plus importantes dans l'arbre généalogique de la chenille hawaïenne

A groundbreaking DNA study has revealed that the Hawaiian honeycreeper family tree suffered far greater losses than previously understood, shedding light on the dramatic decline of these once-diverse birds. Researchers from the Smithsonian Institution have constructed the first comprehensive genetic map of the honeycreeper lineage, tracing both surviving and extinct species since European contact with Hawaii began in 1778. The study was published in the Proceedings of the National Academy of Sciences and provides critical insights into the evolutionary history of the group, which includes more than 60 species that once thrived across the archipelago. The research team combined genetic analysis with museum specimens and fossil records to reconstruct the evolutionary relationships among the honeycreepers. Only 17 of the original species remain today, with most under threat from habitat destruction, invasive species, disease, and climate change. The study underscores the urgency of conservation efforts, revealing that the loss of these unique birds extends beyond what had been previously documented. The honeycreeper family diversified rapidly from a common ancestor over a relatively brief geological timeframe, creating one of nature’s most striking examples of adaptive radiation. This process, where a single species evolves into numerous forms adapted to different ecological niches, occurred primarily around the formation of the island of O'ahu, approximately 2.5 to 3.5 million years ago. Scientists believe the emergence of new landmasses created isolated environments that allowed honeycreepers to evolve into specialized forms suited to varied diets and habitats. Michael Campana, a genomicist at the Smithsonian's National Zoo and Conservation Biology Institute and lead author of the study, described the results as both enlightening and sobering. “We now understand the relationships among the Hawaiian honeycreepers much better,” he said. “However, the findings reveal that we’ve lost more lineages than we thought.” One of the key discoveries was the role of hybridization in shaping the honeycreeper lineage. While interbreeding between species is rare and typically leads to genetic stagnation, the study found evidence of gene flow between two extinct species, the ‘ō’ū and the Lāna‘i hookbill, as well as ongoing genetic exchange among the amakihi, a group of closely related honeycreepers inhabiting different islands. These findings suggest that hybridization played a more significant role in the evolution of the group than previously assumed. To achieve these results, the research team employed advanced genetic sequencing techniques to extract DNA from museum specimens and fossils. Many of these samples came from birds collected centuries ago and stored in museums across the United States and Europe. Helen James, a bird curator at the National Museum of Natural History, expressed admiration for the technological advances enabling such research. “It’s astonishing how much genetic data can be retrieved from minute fragments of skin or bone from long-dead specimens,” she said. “These collections are becoming invaluable resources for modern genomics.” The study emphasizes the importance of preserving biological specimens for future scientific inquiry. As the number of surviving honeycreeper species dwindles, the genetic legacy of the entire group becomes increasingly fragmented. Understanding the full scope of this loss is essential for guiding conservation strategies aimed at protecting the remaining species and potentially reviving others through captive breeding programs or habitat restoration. The research team continues to analyze the genetic data to refine the family tree further and identify specific traits that may have contributed to the survival of certain species. Their work could inform targeted conservation measures, helping to prioritize species most at risk and those with the greatest potential for recovery. With the continued degradation of native ecosystems and the spread of non-native threats, the urgency for action grows ever more pressing.