Madagascar, a true treasure trove of biodiversity, has always captured the attention of botanists. However, there are still regions within the country that remain relatively unknown and lack adequate protection. Given the rapid disappearance of tropical forests, it is crucial to gather valuable information to bolster conservation efforts.
The Sorata forest massif in the northern part of the island is one such region. Until 2015, this area had no formal protection status and was significantly underexplored and endangered. A comprehensive survey conducted by the Missouri Botanical Garden in 2007 resulted in the discovery of over 415 taxa through 645 collections. But these collections were limited to a small area surrounding three campsites. Additionally, due to its location at the northern end of Madagascar's primary mountain range, within the Central biogeographical Domain, Sorata likely acts as a vital bridge for species migration between the north and south. The preservation of this relay zone is crucial for the conservation and genetic diversity of these species. The present study was conducted in partnership between the Conservatoire et Jardin botaniques de Genève, the Universities of Geneva and Antananarivo, and the Famelona organisation, with the aim of compiling a comprehensive list of plant species and conducting a biogeographical study.
The fieldwork led to the collection of 1,052 herbarium specimens, resulting in the identification of 547 plant species within the Sorata region. Among these species, 40 have been identified as new to science. Furthermore, the phytogeographical analyses based on the distributions of the collected species in Sorata conducted across Madagascar and the world have yielded significant discoveries. Specifically, 11 new occurrences were observed within the Central Domain, two of which were located over 1,000 km south of Sorata. Additionally, species previously considered endemic to Marojejy and Montagne d'Ambre within the Central Domain were found in Sorata. Similar findings were made for two endemic species from Loky-Manambato and Ankarana within the Western Domain, as well as Kalabenono within the Sambirano Domain.
Other than highlighting these new occurrences, Sorata was found to potentially serve as a bridge for species distribution. Collections made in Sorata have extended the distribution range of 39 species endemic to the Central Domain, including species that were previously known to occur more than 600 km away from Sorata before this study. This potential role as a relay zone is further supported by the presence of Pandanus latistigmaticus and three species endemic to Montagne d'Ambre in the southern direction.
These results demonstrate that Sorata possesses its own significant local endemism while exhibiting numerous phytogeographical connections with other domains. This suggests that Sorata plays a crucial role as a migration pathway for species across the island. The findings will be shared with local authorities and reserve managers to advocate for enhanced protection measures for the Sorata region and improve the daily management of the protected area.
