Philippine Journal of Systematic Biology Vol. VI (June 2012) Page | 28 BIOTYPE OF THE INVASIVE PLANT SPECIES Chromolaena odorata (ASTERACEAE: EUPATORIAE) IN THE ZAMBOANGA PENINSULA, THE PHILIPPINES LINA T. CODILLA 1 , EPHRIME B. METILLO 2 1 JH Cerilles State College, Mati, San Miguel, Zamboanga del Sur, Philippines 7016 E-mail: ltcodilla@yahoo.com 2 Department of Biological Sciences, Mindanao State University-Iligan Institute of Technology, Iligan City, Philippines 9200 E-mail: ephrime.metillo@g.msuiit.edu.ph ABSTRACT The gross morphology of one of the world’s worst invasive plant species, Chromolaena odorata, now widespread in three provinces of the Zamboanga Peninsula, was examined and compared to the characteristics of Asian/West African (AWA), Southern African (SA), and Central and South American biotypes. C. odorata from the three provinces of Zamboanga Peninsula is very similar with the AWA and the Central and South American biotypes. Implications of this finding are discussed in the light of the species’ invasion and biocontrol in South Asia, Southeast Asia and the Philippines. KEYWORDS: Chromolaena odorata, biotype, Asian-West African biotype, Southern African biotype, Central and South American biotype, gross morphology, invasive plants INTRODUCTION Although originally used in entomology, the term biotype has been generally applied to individuals of a population with similar genotypes and indistinguishable morphology but differ in expressed biological attributes (Shufran and Payton 2009). For example, insect biotypes are individuals that cause damage to a crop plant that is resistant to other individuals of the same insect species (Maxwell and Jennings 1980). However, the usefulness of the biotype concept in systematics and evolution of species is recently debated (e.g. Downie 2010). The plant species Chromolaena odorata (L.) R. M. King and H. Robinson has two recognized biotypes as it became highly invasive and allelopathic after its introduction to Asia and West and South Africa due to the absence of its natural enemies, e.g. the lepidopteran Pareuchaetes pseudoinsulata (Muniappan and Bamba, 2000; Robertson et al. 2008; Zacchariades et al. 2009). These Asia and West Africa (AWA) and Southern