Cytogenetic studies and taxonomic considerations in some taxa of Mallotus (Euphorbiaceae) in Thailand

Abstract

An investigation into the cytogenetics of Thai Mallotus (Euphorbiaceae) indicated that all plants have highly distinctive chromosomes at diakinesis and first anaphase. Bivalent length is 1.33–6 μm in pollen mother cells of 160–286.67 μm. The chromosome numbers of Mallotus can be divided into three groups, viz: 2n = 20 (10II), 22 (11II) and 24 (12II). Chromosome numbers of 11 species are recorded for the first time. The basic numbers of Mallotus are x = 10, 11 and 12. These dysploid numbers may have evolved through a
decrease from 2n = 22 to 2n = 20. M. oblongifolius is taxonomically conspecific with M. peltatus but their chromosome numbers are different with 2n = 20 and 2n = 22 respectively. Therefore, these two species should be maintained as distinct taxa.