Realities of rarity: climatically and ecologically restricted, critically endangered Kandian Torrent Toads (Adenomus kandianus) breed en masse
- Published
- Accepted
- Subject Areas
- Animal Behavior, Biodiversity, Ecology, Taxonomy, Zoology
- Keywords
- mating congregation, rare toad, resource partitioning, niche modelling, montane forests, Sri Lanka, DNA barcoding, tadpole ecology, restricted distribution, conservation and management
- Copyright
- © 2015 Meegaskumbura et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ PrePrints) and either DOI or URL of the article must be cited.
- Cite this article
- 2015. Realities of rarity: climatically and ecologically restricted, critically endangered Kandian Torrent Toads (Adenomus kandianus) breed en masse. PeerJ PrePrints 3:e1575v1 https://doi.org/10.7287/peerj.preprints.1575v1
Abstract
Endemic to Sri Lanka, genus Adenomus contains two torrent-associated toad species whose ecology and natural history in the wild is virtually unknown. Adenomus kelaartii is relatively common, with a wide geographic distribution. Its sister species, A. kandianus, however, is restricted to two isolated populations in fast-disappearing montane and sub-montane forests. Formally declared extinct after not being recorded for over a century, a few A. kandianus were rediscovered in 2012 and redescribed as "the world's rarest toad". Here we report the results of a two-year study of the occurrence, habits and habitat associations of adult and larval A. kandianus using both general surveys and quadrat sampling. We show this to be a secretive species with a patchy distribution. Non-breeding female toads dwell in primary-forest habitats, but after heavy and sudden downpours they form large mating congregations in large streams. Amplexed pairs swim synchronously, enabling them to traverse fast currents. Egg-laying sites remain unknown, but the ability to dive and vocalize underwater, and characteristics of the eggs, suggest that they lay eggs in dark recesses of the stream. Tadpoles show microhabitat partitioning within the stream, with the greatest diversity of stages in slow-flowing rocky areas. The more robust stages possessing sucker discs exploit rocky-rapids, while metamorphic stages inhabit stream margins. We use DNA-barcoding to show the existence of two disparate toad populations. Distribution modeling with forest-cover layers added, predict a very small remaining area of suitable habitats. Conservation of this climatically and ecologically restricted species hinge largely on the preservation of high-elevation primary and riparian forests and unpolluted torrents.
Author Comment
This article has been submitted to PeerJ journal as an original scientific article.
Supplemental Information
Sampling trails and sites for Adenomus kandianus adults and tadpoles
The 4.5 km trail (A to B) representing the habitat and altitudinal gradient that was sampled four times from May 2012–August 2014. Blue markers indicate the tadpole (and mating aggregation) sampling stations along the major stream. Females were found in forest habitats and tadpole stages showed resource partitioning within the stream.
Presence locations of Adenomus kandianus used in this study
Known geographic coordinates of A. kandianus.
Uncorrected pairwise distances within and between Adenomus kanidanus and A. kelaartii populations
The genetic distances within A. kandianus populations suggest recent gene flow between the two main populations.
Video documentary of a mating aggregation of A. kandianus.
Video depcting their habits (synchronous swimming, underwater vocalization, amplexus, male-male competition) and habitat.