This species has a very small distribution in northeastern Queensland, Australia. It is known from short sections of 13 streams draining into the Barron River in the Kuranda area (between the localities of Kuranda, Fairyland, Myola, Mantaka, Kowrowa, and Oak Forest). The distribution is bound to the north, east and south by the northern lineage of Litoria genimaculata (which also occurs at most Litoria myola sites), and to the west by the limit of rainforest distribution (Hoskin 2007). All sites are between 320 and 360 m asl. The extent of occurrence of L. myola is 13.5 km
Habitat and Ecology
All records of L. myola are from rainforest along permanent and ephemeral streams (Hoskin 2007). Rainforest along the streams ranges from mesophyll vine forest to rainforest regrowth dominated by Acacia and Calamus. Litoria myola is a stream breeder (Hoskin 2007). Stream substrate at the sites ranges from rock and gravel through to coarse sand, and stream gradient at all sites is low. Males were only encountered along the streams, at high density at some sites (Hoskin 2007). Females were rarely encountered, with most found on the streams, primarily as gravid individuals, and always where L. myola males were calling (Hoskin 2007). Occasionally, females were sighted perched high in trees, and several females were encountered a considerable distance from the streams (Hoskin 2007). Metamorphs were rarely encountered (on streamside vegetation) and juveniles were not observed (Hoskin 2007). Therefore, as is in L. genimaculata (Richards and Alford 2005, C.J. Hoskin, unpubl. data), L. myola utilizes streams as breeding habitat, primarily in spring and summer, and nonbreeding adults and subadults utilize the surrounding rainforest. Given the apparent rarity of non-breeding individuals on the streams, and how infrequently the species is encountered in the surrounding rainforest, it would appear that L. myola utilizes the mid and upper forest levels when not breeding (Hoskin 2007).
Litoria myola is abundant along only one stream, where it occurs at a density of up to 50 males per 100 m of stream (Hoskin 2007), a density similar to or higher than recorded at sites across the range of L. genimaculata (Laurance et al. 1996, Richards and Alford 2005; C.J. Hoskin pers. observ.). Although L. myola was consistently recorded at a high density along this stream, the four smaller monitored populations were inconsistently detected and declined in abundance from common to rare over the monitoring period (Hoskin 2007). The decline appeared to be due an extended drought between 2002 and 2005, during which most streams in the area stopped flowing and several were completely dry for consecutive years. This was particularly the case for streams on the drier western end of the species' range and populations at these sites may be particularly susceptible to dry periods as they breed in ephemeral streams on sandy soils in marginal rainforest habitat (Hoskin 2007). Intensive surveys in the region in early 2007, following a year of reasonably high rainfall, detected L. myola at all known sites (13 streams), although it remained rare at four of the five monitoring sites (Hoskin 2007). Based on stream surveys of mature males, and assuming an equal sex ratio, the total breeding population was estimated to be less than 1,000 individuals in the summer of greatest abundance and considerably less in other summers (Hoskin 2007). This consisted of a population on one stream estimated at 500 mature individuals and smaller populations of between ten and 100 individuals across the other streams (Hoskin 2007).
Litoria myola is threatened by: (1) clearing of rainforest (including regenerating rainforest); (2) impacts to the streams in terms of water flow, water quality, and sedimentation; and (3) fragmentation of habitat and breeding populations (Hoskin 2007). The species is potentially threatened by: (1) altered levels of hybridization and/or competition with L. genimaculata due to captive breeding and release or movement of individuals of either species into or out of the Kuranda region; (2) frog chytrid fungus; and (3) stochastic events (Hoskin 2007). The sites where L. myola has been recorded are generally unprotected strips of riparian rainforest along streams whose catchments are being heavily altered by rural residential development and more intensive urbanisation (Hoskin 2007). Disturbance to upstream sections of the stream catchments has the potential to detrimentally impact the breeding habitat of L. myola by affecting stream flow, water quality, or sedimentation (Hoskin 2007). L. myola sites are subject to considerable disturbance from clearing, road construction, dam construction, and run-off of sediment, chemicals and rubbish from the catchments (Hoskin 2007). The degree of connectivity between the populations in each of the catchments is not known. Given the genetic similarity between L. myola and L. genimaculata, the effect of disease and parasites on L. myola would be predicted to be similar to that seen in L. genimaculata (Hoskin 2007). Litoria genimaculata is currently common throughout the Australian Wet Tropics but underwent population declines in the early 1990s (Laurance et al. 1996, McDonald and Alford1999). Concurrent declines in several other Wet Tropics stream-breeding frog species resulted in complete disappearance of some species and the decline of others from upland areas (Laurance et al., 1996; McDonald and Alford, 1999). A chytridiomycete fungus (Batrachochytrium dendrobatidis) has been identified as the most likely proximate cause of these declines (Berger et al. 1998), and chytrid is known to be a source of mortality in L. genimaculata (Speare and Berger 2005). Populations of L. genimaculata appear to have recovered to pre-decline levels across the Wet Tropics (McDonald and Alford 1999. Richards and Alford 2005). The effect of chytrid on L. myola is not known but is assumed to be similar to its effect on L. genimaculata (Hoskin 2007). Litoria myola is parasitized by a Dipteran fly (Batrachomyia sp.), but it is not known whether or not this has a negative impact on populations (Hoskin 2007). Hybridization between L. myola and the surrounding populations of L. genimaculata is very limited (Hoskin et al. 2005). Interaction between these two species as it currently stands is not a threat; indeed, it appears to be the driving force for speciation of L. myola from L. genimaculata (Hoskin et al. 2005). However, the reproductive isolation (and competitive interaction) between these two species may be in part density or habitat dependent, and if this were so, the integrity of L. myola could be compromised by reductions in population size or translocations of L. myola frogs or tadpoles out of, or L. genimaculata into, the Kuranda area (Hoskin 2007).
This species occurs in one small conservation park (C. Hoskin pers. comm.). Management of L. myola should focus on protection and revegetation of the stream habitat and surrounding rainforest throughout its range, and include strict control of impacts from the catchments that may affect water quality, water flow and sedimentation (Hoskin 2007). There should be a prohibition on moving and releasing adults or larvae of both L. myola and L. genimaculata throughout the Kuranda area, as this could lead to a breakdown in the isolating mechanisms between the two species (Hoskin 2007).
Conrad Hoskin 2008. Litoria myola. In: IUCN 2014