Cassia species in Queensland

Aim: Conservation Genomics
Project initiation: Aug 2020
Project lead: Laura Simmons | Queensland Herbarium, Department of Environment and Science

Reproduced with permission from Laura Simmons

Project description:

All native Australian species of Cassia occur in Queensland. There are four described species, viz. C. brewsteri, C. marksiana, C. queenslandica and C. tomentella and two taxa currently with phrase names: C. sp. (Kalpowar D.G.Fell+ DF2769) and C. sp. (Paluma Range G.Sankowsky+ 450). Historically, the taxonomy of Australian Cassia has proved difficult due to morphological variation within species, similarities across species and intergrades between species.

Cassia tomentella, one of the focal species of this study, has up to six distinct morphological variants across a latitudinal distribution. Some are restricted to small geographic areas, and if proven both genetically and morphologically distinct, warrant description at species or subspecies level and may require protection under state and federal legislation.

Cassia marksiana occurs in highly fragmented lowland rainforest in SE Qld and has an extent of occupancy (EOO) and area of occupancy (AOO) that results in the species eligible as Endangered under IUCN criteria (2014). Both species are closely related to C. brewsteri and at times have been considered varieties of this species.

Little is known about the relationship of the North Queensland species Cassia queenslandica, Cassia sp. (Kalpowar D.G.Fell+ DF2769) and Cassia sp. (Paluma Range G.Sankowsky+ 450), with the latter thought to have affinities to C. marksiana.

This study aims to: (1) resolve variants of C. tomentella; (2) investigate conservation genomics of C. marksiana; (3) resolve the taxonomic status of the two undescribed tropical species; and (4) contribute to the understanding of the Australian Caesalpinioideae. If the undescribed species and morphological variants within the complex are distinct, these taxa can then be evaluated for conservation listing using the Common Assessment Method (CAM).