Variation in the ilium of central European water frogs Pelophylax (Amphibia, Ranidae) and its implications for species-level identification of fragmentary anuran fossils
Abstract
Background: A total of 454 ilia of modern green frogs from the former German Democratic Republic have been studied: 168 for P. lessonae (86 of males and 82 of females), 118 for P. ridibundus (44 of males and 74 of females) and 168 for P. kl. P. esculentus (86 of males and 82 of females). The origin, sex, population structure and phenotype are known for each of the studied specimens. Eight variables have been taken (one angle and seven measurements), mainly on the distal part of the element in order to be able to apply them to fragmentary fossil ilia. Interspecific variations, sexual dimorphism and population structure have been investigated. Results suggest that the secure determination of a single fossil ilium at species level is quite impossible, but that at population level, it may be possible to distinguish between a ‘pure’ species or a ‘pure’ species plus its cohabiting hybrid form, as some minor differences have been evidenced in particular in the angle of the tuber superior in relation to iliac's main axis (character 2) and the width of the pars ascendens (character 8); two parameters significantly non size-dependent. No sexual dimorphism has been detected, except for P. lessonae.
Results: The genetic analyses of the mitochondrial 16S rRNA, cytochrome oxidase subunit I (COI), and control region (CR) of specimens from various localities showed that there was no genetic differentiation between the populations inside and outside of the Persian Gulf.
Conclusions: We propose here a new biometrical method in order to differentiate between the fossil ilia of central European water frogs (genus Pelophylax) at population level.
Background: A total of 454 ilia of modern green frogs from the former German Democratic Republic have been studied: 168 for P. lessonae (86 of males and 82 of females), 118 for P. ridibundus (44 of males and 74 of females) and 168 for P. kl. P. esculentus (86 of males and 82 of females). The origin, sex, population structure and phenotype are known for each of the studied specimens. Eight variables have been taken (one angle and seven measurements), mainly on the distal part of the element in order to be able to apply them to fragmentary fossil ilia. Interspecific variations, sexual dimorphism and population structure have been investigated. Results suggest that the secure determination of a single fossil ilium at species level is quite impossible, but that at population level, it may be possible to distinguish between a ‘pure’ species or a ‘pure’ species plus its cohabiting hybrid form, as some minor differences have been evidenced in particular in the angle of the tuber superior in relation to iliac's main axis (character 2) and the width of the pars ascendens (character 8); two parameters significantly non size-dependent. No sexual dimorphism has been detected, except for P. lessonae.
Results: The genetic analyses of the mitochondrial 16S rRNA, cytochrome oxidase subunit I (COI), and control region (CR) of specimens from various localities showed that there was no genetic differentiation between the populations inside and outside of the Persian Gulf.
Conclusions: We propose here a new biometrical method in order to differentiate between the fossil ilia of central European water frogs (genus Pelophylax) at population level.
Keywords
Ilium; Pelophylax; Osteology; Biometry; Klepton; Central Europe.
