There are many genera shared between Australian and Papua New Guinean rainforests. Species in the rare rainforest herbaceous genus Romnalda have a relictual and disjunct distribution within the major rainforest blocs of southern Queensland, north Queensland, and New Guinea. There are only four species in this genus: R. strobilacea, R. grallata, and R. sp.‘Cooper Ck’ from Australia, and R. papuana from New Guinea. The Australian species have restricted distributions and high conservation status. Allozymes were used to study the genetic variation and distinctiveness of all four species. Genetic diversity varied significantly amongst the four species. The species in the centre of the genus distribution contained the highest genetic diversity, regardless of rarity. The undescribed R. sp.‘Cooper Ck’ was identified as a clearly distinct species with morphological affinities to R. papuana, but genetic affinities to R. grallata. The study showed that, where the distributions of R. grallata and R. sp.‘Cooper Ck’ overlapped, there was evidence of hybridization. Reproductive participation within populations was typically low with limited flowering synchrony. Populations of all four species were inbred, but higher levels of inbreeding were not correlated with lower genetic diversity. The timing of flowering appeared to be determined by climate. Altitudinal variation in phenological timing in R. sp.‘Cooper Ck’ has led to genetic isolation within the species, but has also limited its genetic introgression with the co‐occurring R. grallata. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157, 455–474.

Rain forests are expected to be amongst the ecosystem types most affected by fragmentation due to their high species diversity, high endemism, complexity of interactions, and contrast with surrounding altered matrix. Due to their shorter life cycles and dependence on canopy cover, rain forest understory herbs are expected to indicate the effects of recent fragmentation more rapidly than canopy trees. This study investigated all four known species of the genus Romnalda, all of which are rare rain forest herbaceous species, to investigate the possible effects of habitat fragmentation and isolation on genetic diversity and gene flow. Allozymes were used as genetic markers and regional remnant vegetation maps were used to compare landscape fragmentation. We found that R. strobilacea populations in a highly fragmented landscape were genetically depauperate compared with those of its congeneric species that are found within continuous rain forest habitats and that allelic diversity decreased with decreasing population size but not geographic distance in R. strobilacea. Given the similarity among the species, our results indicate that all Romnalda species are potentially susceptible to loss of genetic diversity due to habitat fragmentation within relatively short timeframes. The results indicate that populations are not highly genetically differentiated and there is little evidence of genetic provenance where the species have restricted geographic ranges. Thus, species recovery programs would be better to focus on maintaining population size and genetic diversity rather than population differentiation.

A new species, Etlingera frederikii, is described and illustrated, and is the first record of the genus in the Bougainville Region. Etlingera frederikii and E. cevuga, which occurs in Fiji and Samoa, are the two most easterly species in the distribution range of the genus. The new species differs from Etlingera cevuga in its much larger leaves, with a conspicuously silky-haired band on the ligule; the smaller, narrowly ovoid to cylindrical inflorescence with pale brown bracts (not hemiglobose with reddish brown bracts); and fewer, smaller flowers.