Variability in the Last Abdominal Sternum of Brontispa longissima Populations Using Outline-Based Geometric Morphometric Analysis

Abstract

Abstract-The coconut plant plays a major role in the economy of many Asian countries including the Philippines and their economies are recently threatened due to a serious outbreak of the coconut leaf beetle, Brontispa longissima (Gestro). This study was conducted to observe if there is an intraspecific morphological variation among the coconut hispine beetle populations in terms of the last abdominal sternum shape to better understand why these pests differed in the level of their infestation in different populations. From outline-based geometric morphometrics analysis, results showed that a considerable sternum shape variation among the populations is studied. Morphological sternum shape variations were verified statistically in Principal Component Analysis, Canonical Variate Analysis, and Multivariate Analysis of Variance (MANOVA) using PAST 2.13 software. Furthermore, shape differences could be observed in the shape representation of Elliptic Fourier Shape analysis as well as in the PCA diagrams and CVA scatter plots.Index Terms-Abdominal sternum, B. longissima, geometric morphometircs, morphology, shape variability. I. INTRODUCTIONThe coconut palm plays a major role in the economy of many Asian countries by providing food and income from its products. It is an important source of income in many households especially in the Philippines which is known to be the biggest exporter of coconut productions in the world. Currently, there are losses of coconut production that lead to a threatened economy of the country due to a serious outbreak of the coconut hispine beetle, Brontispa longissima (Gestro), (Coleoptera: Chrysomelodae) [1]. The larvae and adult of the coconut hispine beetles (CHB) feed on tissues of unopened leaf buds of the palm where they turn the leaves brown causing a decreased fruit production and successive severe defoliations that leads to death of the tree [2]. Only limited information about B. longissima has been presently published. Yet there have been available reports associating the management of this pest. Yet, the reported control strategies which seem to have failed to the infestation are now distributed in the Southern places of the Philippines, in Manuscript received February 23, 2014; revised April 28, 2014 Mindanao.Moreover, it is argued that a successful control of the pest based on correct identification for the inability to recognize distinct populations can have severe and costly consequences for pest management [3]. Therefore, it's necessary to consider the coconut hispine beetle (CHB) in details to stop its infestation in the country, especially that different levels of infestation have been observed among the invaded localities.Morphological variability is a good start to better understand why the CHB have differed in the level of infestation, for distinct populations of agronomic pest differ only on little phenotypic characters and sometimes these may represent stable characters with genetic bases which are good bases for the study [4]. An advanced tools of the geometric mo...