Plastid DNA from the extinct Trilepidea adamsii confirms its close relationship to Alepis and Peraxilla (Loranthaceae)

Abstract

ABSTRACT The generic relationships of the extinct Trilepidea adamsii (Cheeseman) Tiegh. from New Zealand have been uncertain due to the paucity and age of available plant material. Last seen nearly seventy years ago in 1954, fresh material has not been available for comparative studies. Trilepidea adamsii has morphological affinities to Alepis flavida (Hook.f.) Tiegh., Peraxilla colensoi (Hook.f.) Tiegh. and P. tetrapetala (L.f.) Tiegh. with all taxa being placed in subtribe Elytranthinae, but precise phylogenetic relationships have not been determined. Using leaf material of Trilepidea adamsii from a specimen in Allan Herbarium (CHR) collected in 1920 from near Thames, Coromandel Peninsula, North Island, we recovered approximately 93% of the plastid genome by mapping Illumina sequence reads to a plastid genome sequence of Elytranthe albida (Blume) Blume, with Elytranthe being another genus of Loranthaceae. We also sequenced plastid genomes of Alepis flavida, Peraxilla colensoi and Peraxilla tetrapetala and conducted a phylogenetic analysis using other Loranthaceae plastid genome sequences from GenBank. Phylogenetic analyses of the plastid genome sequences confirmed T. adamsii as sister to a clade comprising Alepis and Peraxilla. While the level of sequence divergence is low, we do not consider that the generic boundaries need to be reassessed. We suggest re-examination of anatomical and morphological traits is warranted to better understand evolution in this lineage of four endemic mistletoe species.