Genetic analysis of a genus of plant mimics (Alseuosmia A.Cunn; Alseuosmiaceae) reveals incongruence between morphology and phylogeny and possible mimetic polymorphism

Abstract

Abstract Alseuosmia (Alseuosmiaceae) is an endemic New Zealand genus of small trees and shrubs, which is unusual in that some taxa appear to morphologically mimic unrelated species. The taxonomy of the group has long been debated, with the extreme morphological diversity in A. banksii causing much of the confusion. Here we use ddRADseq to examine the genetic relationships between species of the genus, with a particular focus on the morphological forms of A. banksii. Our analyses revealed that for species in the northern part of the distribution, genetic relationships largely matched geography rather than species boundaries based on morphology, and that hybridization between morphs appears to be common. A diversity of morphologies is present within these northern Alseuosmia, including multiple forms that appear to mimic unrelated genera, and these may constitute a single gene pool. Further south, two species (A. turneri and A. pusilla) were genetically distinct in sympatry. We suggest maintaining the current taxonomy until further research can be undertaken.