This species is found in the mountains of Mindanao and Dinagat Islands, in the Philippines, between 700–2,200 m asl. It is expected to occur more widely (A. Diesmos pers. comm. March 2018).
Habitat and Ecology
This species inhabits cool mountain streams and rivers in montane rainforest where it also breeds and the larvae develop. With its highly specific torrent-dwelling larval habitat requirements, it is limited to montane habitats (and lowlands near mountains) with high gradient stream flow (Sanguila et al. 2016). It is generally restricted to undisturbed or minimally disturbed habitats (Delima et al. 2006). Adults have generally been collected in splash zones near rapids or waterfalls, though they have also been found on the ground among leaf-litter away from water, especially after a period of rainfall (Sanguila et al. 2016).
It is fairly common where it occurs, but it has a patchy distribution throughout Mindanao (Inger 1954, 1992; Matsui et al. 2010). This distribution appears to be the result of its natural, larval habitat requirements (Sanguila et al. 2016). In suitable habitat this species was observed in large numbers and was often the most commonly observed amphibian in sampled areas in northeast Mindanao (Sanguila et al. 2016). In Mt. Kalatungan, it is observed to be very abundant (Warguez et al. 2013). Due to ongoing decline in the extent and quality of its habitat, the population is suspected to be decreasing.
The major threat is the destruction and conversion of both lowland and montane rainforest habitat on Mindanao due to small-scale agricultural activities, large-scale oil palm plantations, wood collection for charcoal production, and expanding human settlements (Philippines Red List Assessment Workshop May 2017). In addition, the quality of its stream habitat is subject to pollution due to agricultural effluents, soil erosion, and mine-tailings (Philippines Red List Assessment Workshop May 2017).
This species is known from several protected areas, including Mount Malindang National Park.
Conservation measures must include the regulation and proper disposal of pesticides and herbicides, and the protection of the remaining rainforest, especially high-elevation riverine habitats and gallery forests, on Mindanao. To preserve genetic diversity, protection of habitat in all five areas of genetic endemism across the species' range will be required (Sanguila et al. 2011).
The taxonomic status of this species requires further study to determine if this is a complex of more than one species (Diesmos et al. 2014), which will allow species boundaries of this widespread species complex to be defined (Sanguila et al. 2011). More information is also needed on this species' distribution, population status and ecology.
Red List Status
Listed as Least Concern in view of its wide distribution and presumed large population.
A recent phylogeographic study identified five genetically divergent and geographically structured haplotype groups in central and eastern Mindanao. Sanguila et al. (2011) argued that, at a minimum, these lineages should be recognized as evolutionarily significant units (ESUs) for conservation purposes, and that they may represent distinct species.
IUCN SSC Amphibian Specialist Group 2018. Ansonia muelleri. The IUCN Red List of Threatened Species 2018: e.T54477A58477220. http://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T54477A58477220.en .Downloaded on 23 January 2019