Application of cecidomyiid galls to the systematics of the genus Machilus (Lauraceae) in Taiwan

Abstract

The species of the genus Machilus (Lauraceae) in Taiwan sustain diverse cecidomyiid galls induced by the insects of the genus Daphnephila (Cecidomyiidae). This work examines the feasibility of applying cecidomyiid galls to the systematics of the genus Machilus. Amplified fragment length polymorphism (AFLP) was used to analyze the 38 gall-bearing trees of four Machilus taxa including Machilus kusanoi, M. thimbergii, M. zyihoensis var. zuihoensis, and M. zuihoensis var. mushaensis. The UPGMA cluster analysis of the AFLP data revealed three distinct clusters, including M. kusanoi, M. thunbergii, and M. zuihoensis variety complex. Machilus zuihoensis var. zuihoensis and M. zuihoensis var. mushaensis were indistinguishable from the three primer combinations. These two varieties could be considered the same taxon. PCR and DNA sequencing methods were used to analyze the nucleotide sequences of the mitochondrial 16S rDNA gene of the twenty gall midges from three types of galls from four Machilus taxa. The phylogenetic tree from the partial 16S rDNA sequence by UPGMA method of proportion distance revealed that the gall midges can be divided into three groups according to gall types. The phylogenetic tree cannot separate the two varieties of M. zuihoensis within each group. Machilus zuihoensis var. zuihoensis and M. zuihoensis var. mushaensis cannot be distinguished according to the AFLP or DNA sequencing methods, and they are more closely related to M. thunbergii than to M. kusanoi. The systematic relationships among the Machilus from the data of host plants are congruent with the data from the gall inducers. Results in this study imply that the gall inducers of genus Daphnephila provide information for resolving the plant systematic relationships based on molecular techniques.