Hibiscus Section Furcaria (Malvaceae) in Australia

Abstract

Of the approximately 50 species in Hibiscus section Furcaria DC. emend. Hochr., 15 native and one naturalized taxa are recognized in Australia. Thirteen of the 15 native taxa are endemic; four of these are described as new (Hibiscus arnhemensis, H. bymesii, H. minutibracteolus and H. mustiae). Of the other two species, H. meraukensis Hochr. is the only one that is wide ranging in Australia proper, being distributed from the Kimberleys of Western Australia to south-eastern Queensland; it occurs also in neighbouring southern New Guinea. The other one, H. diversifolius Jacq., is confined to the east coast from southern Queensland to central New South Wales in Australia, but its total distribution is pantropical. The single naturalized species, H. sabdariffa L., was introduced into Australia in the 19th century and grown for its fleshy calyces, which were processed and marketed as 'rosella jam'. Fourteen of the 15 native taxa form a morphologically coherent group within Hibiscus section Furcaria and are characterized by involucral bracteoles with entire apices and calyx lobes without nectaries on the midrib. The nine taxa for which chromosome numbers are available are also cytologically coherent (hexaploid: n = 54). H. diversifolius is set apart from the other taxa by its calyces with nectaries, its octoploid (n = 72) chromosome number, and its extra-Australian distribution. It most likely had a history in Australia distinct from that of the endemic species.