Ocean Romance: Japanese Treefrogs Exploit Coastal Pools for Breeding Under Salinity and Habitat Constraints

Area of Science:

• Ecology
• Amphibian Biology
• Conservation Science

Background:

• Amphibian microhabitat selection is crucial for understanding local adaptation in coastal island populations.
• The coastal breeding ecology of the Japanese Treefrog (Dryophytes japonicus) is poorly understood, with a significant knowledge gap in studies of natural coastal pools.

Purpose of the Study:

• To determine if coastal pools can support Japanese Treefrog populations.
• To investigate the influence of environmental factors, particularly salinity, on breeding site selection by Dryophytes japonicus.

Main Methods:

• A meta-analysis of 95 published studies was conducted.
• Field surveys of 810 tadpoles from 84 coastal pools on Jeju Island were performed.
• Random forest and partial dependence analyses were used to assess environmental factors influencing tadpole occurrence.

Main Results:

• A significant knowledge gap exists, with most studies focusing on agricultural habitats rather than natural coastal pools.
• Distance to the coastline was the strongest predictor of tadpole occurrence, with higher occurrence in inland pools.
• Japanese Treefrogs bred in shallow, low-salinity pools away from forest edges and shorelines; dissolved oxygen was also important.

Conclusions:

• Dryophytes japonicus exhibits spatial filtering in coastal landscapes, preferring inland, low-salinity, well-oxygenated pools.
• Understanding these microhabitat preferences is vital for amphibian persistence in coastal environments facing multiple constraints.
• This study provides critical ecological insights into Japanese Treefrog breeding in poorly studied coastal habitats.