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Donus multifidus is a single island endemic species from Santa Maria (Azores, Portugal). It has a very small extent of occurrence (EOO = 4 km²) and area of occupancy (EOO = 4 km²). There is a continuing decline in the EOO, AOO, extent and quality of habitat as well as the number of mature individuals as a result of the invasions of non-native plants. The species occurs only at one location. Therefore, it is assessed as Critically Endangered (CR).
Donus multifidus is a single island endemic species from Santa Maria (Azores, Portugal) (Borges et al. 2010), where it is restricted to the highest elevations of the island (450 to 550 m asl) and to the unique native primary forests. The size of its remaining native habitat is 0.09 km², but the AOO is 4 km². Its extent of occurrence (EOO) is therefore also 4 km².
The species is very rare and only known from a single sustainable subpopulation. A continuing decline in the number of mature individuals is inferred from the ongoing habitat degradation due to invasions of alien plants.
The species occurs in native forests of high altitude in Sta. Maria island (Azores), with an altitudinal range between 450 and 550 m. Adults and larvae are herbivores and feed of plant tissues.
In the past, the species has probably strongly declined due to deforestation. The most important ongoing threat to this species is the spread of invasive plants (Hedychium gardnerianum and Pittosporum undulatum) that are changing the habitat structure in the main native forest, namely decreasing the cover of bryophytes and ferns in the soil and promoting the spread of other plants. Based on Ferreira et al. (2016) the habitat will decline as a consequence of climate change (increasing number of droughts), which may drive this species to extinction, because it is dependent on humid forests.
The species is protected by regional law (RAA 2012). Its habitat is in a regionally protected area (Natural Park of Santa Maria). Further spread of invasive plants needs to be stopped in order to avoid any future decline of the species. Degraded habitats should be restored and a strategy needs to be developed to address the future threat by climate change. A habitat management plan is needed and anticipated to be developed during the coming years. Further research is needed into its ecology and life history in order to find extant specimens in the Pico Alto region (including non-native habitats) and obtain information on population size, distribution and trends. It is also necessary an area-based management plan and a monitoring plan for the invertebrate community in the habitat in order to contribute to perform a species potential recovery plan. Monitoring every ten years using the BALA protocol will inform about habitat quality (see e.g. Gaspar et al. 2011).