Using RADseq to resolve species boundaries in a morphologically complex group of yellow-flowered shrubs (Geleznowia, Rutaceae)

Abstract

The morphologically complex and charismatic genus Geleznowia (Rutaceae) is endemic to south-western Australia and faces existing and potential conservation issues associated with land clearing, climate change and commercial harvesting. Two species are currently recognised in the genus, but horticulturally recognised forms and phrase-named taxa reflect additional suspected species diversity. The genus exhibits complicated and subtle patterns of morphological variation that have historically inhibited delimitation of taxonomic entities and, as a result, precluded effective conservation assessments. Here we used ddRAD data from 25 populations across the range of Geleznowia to elucidate genomic diversity in the group in conjunction with morphological re-assessment so as to delimit species and revise the taxonomy. Our analyses consistently identified seven entities that maintain genomic distinctiveness even in sympatry with other entities, supporting the inference of reproductive barriers and lineage divergence. Morphological assessment of more than 300 specimens corroborated these seven taxa. Consequently, we recognise seven species of Geleznowia in Western Australia, retaining G. amabilis K.A.Sheph. & A.D.Crawford, recircumscribing G. verrucosa Turcz., reinstating G. calycina (J.Drumm. ex Harv.) Benth., and naming four new species as G. eximia K.A.Sheph. & A.D.Crawford, G. narcissoides K.A.Sheph. & A.D.Crawford, G. occulta K.A.Sheph. & A.D.Crawford, and G. uberiflora K.A.Sheph. & A.D.Crawford.