Supervised machine learning to determine species boundaries reveals the
scale of mislabelling in Dicroglossid frogs across the Eastern
Indomalaya and Southeastern Palearctic
Abstract
Widespread amphibians are frequently impacted by incorrect species
assignments and inaccurate taxonomic labelling in open databases and
published studies, leading to confusion regarding species boundaries and
missing information for population trends at the ecozone level. We
examined three genera in the family Dicroglossidae (Fejervarya,
Hoplobatrachus and Quasipaa) across the Indomalaya and
Palearctic ecozones, where unresolved species boundaries and the
introduction of exotic populations are significant issues. Alternative
to conventional phylogeny, we employed the Bayes Factor Delimitation
method and nested sampling to assess 18 comparative delimitation models
for 15 verified species in GenBank, using 4,044 bp unlinked multilocus
data from 487 individual Asian Dicroglossids across both ecozones. Our
best-supported model delineated 17 clades across three genera,
highlighting Fejervarya as the genus with the shallowest clade
assemblages, with two clades within each of the F. kawamurai,
F. multistriata, and F. limnocharis species complexes, all
diverging below 3.70 Mya in the Northern Indomalaya and Southeastern
Palearctic. Through adjusted ecological niche modelling with species
delimitation data, we verify that precipitation of the driest month,
elevation, and mean diurnal temperature range, are key variables
influencing the distribution of F. kawamurai and F.
multistriata in mainland East Asia. Cross validation using call
analysis supported significant differences in call durations and
intervals between F. kawamurai [Clade II] and F.
multistriata [Clade II] in their overlapping range in the eastern
Yangtze River Basin indicated the existence of subspecies boundaries
even in the absence of physical barriers and validated the presence of
F. multistriata along the central coast of China, i.e. Shanghai.
Our findings also showed the clustering of the southern Palearctic
Fejervarya clade, including the population in the Jiangsu Plains,
within the Yangtze group of F. kawamurai, and delineated the
northern limit of F. multistriata in the vicinity of the Huai
River.