Molecular phylogeny of the Nectria haematococca-Fusarium solani species complex

Abstract

Phylogenetic relationships and biogeography of the phytopathogenic Nectria haematococca-Fusarium solani species complex, section Martiella of Fusarium, were inferred from sequence data from the nuclear large subunit 28S rDNA, the nuclear ribosomal internal transcribed spacer (ITS) region and translation elongation factor (EF-la) gene introns and exons. Although a partition homogeneity test detected significant incongruence between the 28S rDNA and ITS datasets, results of the nonparametric Wilcoxon signed-ranks Templeton test indicated that the data could be combined. Maximum parsimony analysis of the combined dataset identified 26 phylogenetically distinct ingroup species, of which 15 are heterothallic, 7 are homothallic and 4 are putatively mitosporic. Included among these were 9 formae speciales described for F. solani which were all resolved as phylogenetically distinct species by the molecular phylogeny. Of these, F. solani f. sp. cucurbitae races 1 and 2 appear to represent reproductively isolated biological species with independent evolutionary origins. Results of the molecular phylogeny also provide strong support for clades within New Zealand, South America, Africa and India-Sri Lanka. The complex historical biogeography of this complex appears to reflect vicariant events associated with the fragmentation of Gondwanaland, possible gondwanic range expansions together with relatively recent distributional changes in these fungi associated with movement of economically important plants.