Morphological and Genetic Variations of Ingerophrynus parvus (Boulenger, 1887) in Southern Thailand

Abstract

Stream toad Ingerophrynus parvus is distributed in Southeast Asia. This species has small body size, and habitat specificity. The topography of southern Thailand might affect its distribution and connection among Ingerophrynus parvus populations. This study aimed to compare the morphological and genetic variations of Ingerophrynus parvus populations in southern Thailand. Newly collected 166 specimens from 10 study localities were examined for 15 morphological characters, and the data was analyzed using chi-squared test. Sexual size dimorphism were examined base on 18 morphometric characters, and the analysis was performed using independent sample t-test and sexual size dimorphism index. One-way ANOVA analysis and hierarchical cluster analysis were used to compare the differences of morphometric characters among populations. The results show that seven from 15 characters of external morphology were significantly different among localities. The morphometric study exhibited that females of Ingerophrynus parvus were significantly larger than that of males, Moreover, morphometric characters of males and females showed positive correlation with snout to vent length (SVL). Besides, 17 from 18 ratios of morphometric characters with SVL showed significantly different characters among localities (p<0.05), and hierarchical cluster analysis group specimens from Tarutao Island separated from the mainland populations. It was found that population from Tarutao shared some morphometric characters with population from mainland. This could be results of the connection between Tarutao Island and the mainland in the past, leading to sharing of external morphology between the island and mainland populations. However, morphological characters of the mainland populations did not clearly show the group of Ingerophrynus parvus populations. Molecular study of 16S rRNA gene from 518 nucleotides were analyzed with maximum likelihood and network analysis. The molecular study showed genetic variation followed the isolated mountain ranges in southern Thailand, i.e., Tenasserim Mountain Range, Nakhon Si Thammarat Mountain Range and Sankalakhiri Mountain Range. The specimens from Tenasserim Mountain Range were closely related with populations from Nakhon Si Thammarat Mountain Range, but grouped separated from populations from Sankalakhiri Mountain Range. Explaining by geographical distance that the big lowland area between Nakhon Si Thammarat Mountain Range and Sankalakhiri Mountain Range can influence distribution of Ingerophrynus parvus populations. The smaller lowland areas between Tenasserim Mountain Range and Nakhon Si Thammarat Mountain Range, and between Sankalakhiri Mountain Range and Thale Ban National Park had less effect on the distribution of Ingerophrynus parvus. This study exhibit variation in external morphology among Ingerophrynus parvus populations in southern Thailand, but it's not clearly distinct into subgroup. However, molecular study group Ingerophrynus parvus populations follow isolated mountain ranges in southern Thailand.