Examining the Effectiveness of Discriminant Function Analysis and Cluster Analysis in Species Identification of Male Field Crickets Based on Their Calling Songs

Ranjana Jaiswara,Diptarup Nandi,Rohini Balakrishnan

doi:10.1371/journal.pone.0075930

Ranjana Jaiswara, Diptarup Nandi + Show 1 more

Open Access

https://doi.org/10.1371/journal.pone.0075930

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Journal: PLoS ONE	Publication Date: Sep 25, 2013
Citations: 55	License type: CC BY 4.0

Affiliation: Indian Institute of Science Bangalore

Abstract

Traditional taxonomy based on morphology has often failed in accurate species identification owing to the occurrence of cryptic species, which are reproductively isolated but morphologically identical. Molecular data have thus been used to complement morphology in species identification. The sexual advertisement calls in several groups of acoustically communicating animals are species-specific and can thus complement molecular data as non-invasive tools for identification. Several statistical tools and automated identifier algorithms have been used to investigate the efficiency of acoustic signals in species identification. Despite a plethora of such methods, there is a general lack of knowledge regarding the appropriate usage of these methods in specific taxa. In this study, we investigated the performance of two commonly used statistical methods, discriminant function analysis (DFA) and cluster analysis, in identification and classification based on acoustic signals of field cricket species belonging to the subfamily Gryllinae. Using a comparative approach we evaluated the optimal number of species and calling song characteristics for both the methods that lead to most accurate classification and identification. The accuracy of classification using DFA was high and was not affected by the number of taxa used. However, a constraint in using discriminant function analysis is the need for a priori classification of songs. Accuracy of classification using cluster analysis, which does not require a priori knowledge, was maximum for 6–7 taxa and decreased significantly when more than ten taxa were analysed together. We also investigated the efficacy of two novel derived acoustic features in improving the accuracy of identification. Our results show that DFA is a reliable statistical tool for species identification using acoustic signals. Our results also show that cluster analysis of acoustic signals in crickets works effectively for species classification and identification.

Highlights

Traditional taxonomy, which involves discovering and identifying new species using key morphological characters and matching them with the characters of voucher specimens, has contributed to biodiversity exploration since the time of Linnaeus
Several attempts have been made to use technological advances in the fields of molecular biology and engineering to overcome this problem. In this modern era of taxonomy, many new methods for systematic study of organisms are in use such as DNA barcoding [2,3] and Web-based taxonomy [4,5,6]
Traditional taxonomy based on morphology fails to identify taxa that appear morphologically very similar to each other and in such cases, molecular taxonomy using DNA sequences becomes one of the important approaches in identification of cryptic species [7]

Summary

Introduction

Traditional taxonomy, which involves discovering and identifying new species using key morphological characters and matching them with the characters of voucher specimens, has contributed to biodiversity exploration since the time of Linnaeus. The process of biodiversity exploration and estimation slows down in the tropics due to high species diversity, lack of sufficient numbers of active trained taxonomists [1] and often due to the inaccessibility of the holotype specimens that are necessary for confirming species identity This problem can be even more confounding in the case of arthropods which have enormous diversity, especially in the tropics [1]. Several attempts have been made to use technological advances in the fields of molecular biology and engineering to overcome this problem In this modern era of taxonomy, many new methods for systematic study of organisms are in use such as DNA barcoding [2,3] and Web-based taxonomy [4,5,6]. Traditional taxonomy based on morphology fails to identify taxa that appear morphologically very similar to each other and in such cases, molecular taxonomy using DNA sequences becomes one of the important approaches in identification of cryptic species [7]

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