Cryptic speciation in Fusarium subglutinalls # 8915

Fusm'iulIl isolates that form part of the Gibbndla fujikuroi species complex have been classified using either a morphological, biological, or phylogenetic species concept. Problems with the taxonomv of Fusarium species in this complex are mostly eXI;erienced when the morphological and biological species concepts arc applied. The most consistent identifications are obt.ained with the phylogenet.ic species concept. Resul L'i from recen t studies have presented an example of discordance between the biological and phylogenetic species concepts, where a group of F sllbglutinans sensu sllicto isolates, i.e., isolates belonging to mating population E of the G. Jiljilwroi complex, could be sub-divided into more than one phylogenetic lineage. The aim of this study was to determine whether this sub-di\ision represented species divergence or intraspecific diversity in F suhglutillalls. For this purpose, we included 29 F subglutinans isolates helonging to the E-mating population that were colleered from either maize or teosinte, from a wide geographic range. DNA sequence data for six nuclear regions in each of these isolates were obtained and used in phylogenetic concordance analYses. These analyses revealed the presence of two maj(')r groups repre~enting cryptic species in f·: subAccepted for publication Ap"il 28. 2002. I Corresponding amhor, Email: [email protected]; current address: Departmcnt of Biolul-,'Y, Uni\ersity oflllrk. PO Box 373. York 1'010 ,,)11'. UK. glutinans. These cryptic species were further sub-divided into a number of smaller groups that appear to be reproductively isolated in nature. This suggests not only that the existing F. subglutinans populations are in the process of divergence, but also that each of the resulting lineages are undergoing separation into distinct taxa. These divergences did not appear to be linked to geographic origin, host, or phenotypic characters such as morphology.