Fragmentation and Genetic Diversity in Romnalda (Dasypogonaceae), a Rare Rain forest Herbaceous Genus from New Guinea and Australia

Abstract

ABSTRACTRain 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.