This species is only known from its type locality in Manombo Special Reserve from ca. 50 m asl, Fianarantsoa Province in southeastern Madagascar (Vences et al. 2015). Its extent of occurrence (EOO) is 89 km2 and estimated elevational range is 0-100 m asl. Because lowland species tend not to be extreme microendemics, it is expected to occur in other nearby lowland sites; however, littoral forest in the area where the species occurs is extremely reduced, so any other sites are likely to be small and under high pressure (M. Vences pers. comm. March 2016).
Habitat and Ecology
Specimens were found in low vegetation along a small moving, shallow stream within a disturbed area of low altitude, littoral forest (Vences et al. 2015).
This species is only known from two male individuals. Due to ongoing declines in the extent and quality of habitat, the population is suspected to be decreasing.
There is very little remaining littorial forest in southeast Madagascar, all of which is subject to ongoing deforestation for timber and charcoal production, subsistence agriculture, livestock grazing, regular burning to maintain cattle pasture, expanding human settlements, and mining activities.
This species is found in Manombo Special Reserve, which is already quite degraded but reasonably well-protected; it is along a major road and heavily impacted by cyclones which some years ago destroyed a large part of the remaining forest in the reserve (M. Vences pers. comm. March 2016).
Improved habitat protection of lowland forest is required, including inside the Special Reserve, because so little forest is left (M. Vences pers. comm. March 2016).
Further study is required to better understand the size and distribution of the species' population.
Red List Status
Critically Endangered (CR)
Listed as Critically Endangered because its extent of occurrence (EOO) of 89 km2 is unlikely to be much larger due to the little remaining lowland forest in the region where this species occurs. Furthermore, it is known from a single threat-defined location where pressures on the forest are high, and are causing ongoing declines in the quality and extent of its habitat. The species is listed in this category despite being known from so few records as a precautionary measure due to the severe and ongoing pressure on the remaining habitat in the region and because it not expected to occur much further beyond the area from which it is currently known.
IUCN SSC Amphibian Specialist Group 2016. Guibemantis diphonus. The IUCN Red List of Threatened Species 2016: e.T88219153A88312479. http://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T88219153A88312479.en