Use of molecular techniques and discriminant analyses to determine with biometric measurements two subspecies of reed bunting Emberiza schoeniclus
Published: Volume 56(1), June 2009. Pages 85-94.
Original Title: Uso de técnicas moleculares y análisis discriminantes para diferenciar mediante biometría dos subespecies de escribano palustre Emberiza schoeniclus
Aims: To compare the biometry of the endangered western iberian reed bunting Emberiza schoeniclus witherbyi with the wintering populations of the nominal subspecies E. schoeniclus schoeniclus, using a sample of individuals previously identified by molecular techniques, and to obtain a discriminant function to easily determine the subspecies of birds in hand.
Location: Birds were captured in different populations in Spain, Portugal and Finland.
Methods: Blood, feathers or tissues samples from 99 individuals were used for extracting DNA to taxonomically classified two subspecies of reed buntings. Biometric measures were compared between E. s. schoeniclus and E. s. witherbyi subspecies for the 43 individuals for which subspecies assignation was known by molecular analysis. Discriminant analyses were used to identify the best traits for discriminating between the two subspecies. Biometric measurements from another different 105 reed buntings were externally used to validate the discriminant function.
Results: The molecular analysis classified correctly most of the individuals to the subspecies where they were initially assigned. There were significant differences in bill length, bill width, bill height and tarsus between the two subspecies studied. The best discriminant function included only bill height as the predictor variable and correctly classified 95 % of individuals included in the molecular subspecies sample, and 99 % of individuals from the external sample. A bird will be classified as Emberiza schoeniclus witherbyi if bill height is > 5.9 mm and as Emberiza schoeniclus schoeniclus if bill height is < 5.9 mm.
Conclusions: The discriminate function obtained using measurements of individuals previously assigned to each subspecies by molecular analyses showed that it is possible to distinguish between the twosubspecies with high accuracy using only bill height as a simple biometric measurement. From an evolutionary point of view, this difference in bill shape and size may be explained by an adaptation to different feeding habits.