Melichrus hirsutus

Melichrus hirsutus View in CoL and Melichrus gibberagee

Melichrus hirsutus View in CoL and M. gibberagee View in CoL were each collected separately for the first time several years after Paterson’s (1958) revision was published. Despite the geographic proximity in north-eastern NSW, the taxonomic status was strongly supported by distinct morphological characteristics and these were published as new species ( Kennedy et al. 2020). These two species are included in this study to test their status as distinct species based on molecular evidence.

Aims and approach of the study

The species-level taxonomy for Melichrus has never been tested using either a numerical morphological approach or any form of genetic data. We use both in an integrative taxonomic approach to determine robust species boundaries in line with the unified species concept. We developed a new, comprehensive morphological dataset representing the eastern Australian Melichrus species and applied an analytical pipeline to thoroughly explore patterns of similarity in the dataset. A complementary DArTseq ( Kilian et al. 2012) dataset for the genus was interrogated using various clustering, ancestry estimation and population genetics analyses to identify discontinuities in the dataset, examine population structure and therefore test boundaries of species in the study group. Within the broader aim of species delimitation we address several specific questions, namely: (1) are there six species of Melichrus in eastern Australia ( M. urceolatus , M. erubescens , M. procumbens , M. adpressus , M. hirsutus and M. gibberagee ) as currently described or are there up to 19 undescribed species as indicated by the phrase names in use at the Queensland Herbarium (BRI) and N.C.W. Beadle Herbarium (NE)? (2) Is Melichrus urceolatus a natural group or has this been used as a ‘catch-all’ taxon for specimens that could not be adequately identified under the status quo taxonomic classification? (3) Where does the boundary lie between the often-confused taxa, M. urceolatus and M. erubescens? We address these and other questions of species’ limits and provide detailed recommendations for a revised taxonomy of Melichrus .