Genetic divergence and reproductive isolation in the genus Fejervarya (Amphibia: Anura) from Bangladesh inferred from morphological observations, crossing experiments, and molecular analyses

In the present study, morphological examinations, crossing experiments and molecular analyses were performed to elucidate the degree of genetic divergence and phylogenetic relationships within the genus Fejervarya from Bangladesh and other Asian countries. Morphological characteristics revealed that Fejervarya species from Bangladesh were divided into four distinct groups: large, medium, small, and mangrove types. Crossing experiments indicated the involvement of three reproductive isolating mechanisms: gametic isolation between the large type and mangrove type, hybrid inviability between the large type and two other types, and hybrid sterility between the medium and small types. Experimental results also indicated that these four types of frogs merit the status of individual species of Fejervarya. Molecular analyses based on mtDNA gene sequences showed that the Bangladesh Fejervarya species were largely divided into three groups: the mangrove type, large type, and others, with the last further subdivided into the medium and small types. Comparison with other Asian Fejervarya species revealed that the Bangladesh mangrove type (which resembled F. cancrivora in morphology) was closely related to F. cancrivora from India, Thailand, and the Philippines; the large type belonged to the F. iskandari group and closely resembled F. orissaensis; the small type was included in the South Asian or Indian group, and was closest to F. syhadrensis from India and Sri Lanka, whereas the medium type was most closely related to F. limnocharis from Myanmar among all described species of this genus.