Human-mediated introduction of Livistona palms into central Australia: conservation and management implications.

Molecular phylogenies and their application to biogeoGiven the insights of Kondo et al. [1] regarding the graphic questions, as illustrated by Kondo et al. [1] in their study of Livistona palms in Australia, are providing unprecedented insight into speciation and the historical movement of taxa around the world [2]. While such studies often allow for the clarification of taxonomic relationships, they can also raise challenging dilemmas in regard to species management plans and the policy that underpins these strategies [3]. Although framed as a test of species range formation, the Kondo et al. [1] study generates conclusions that are particularly relevant for policy relating to the management of non-native populations. In this commentary, we highlight the broader relevance of the article by Kondo et al. [1] to concepts that define native or non-native status, and discuss the implications for conservation and management policies. Kondo et al. [1] used nuclear microsatellite data to investigate the relationship between Livistona mariae F.Muell., an iconic palm endemic to central Australia, and its nearest relative, Livistona rigida Becc. Their study establishes that L. mariae and L. rigida diverged from a common ancestor around 15 375 years ago (90% highest posterior density interval: 6625–30875 year BP) [1]. This timeframe invalidates the hypothesis that L. mariae is a relictual population which has survived since before the aridification of central Australia (15 Ma) [4,5], and also the alternate explanation of dispersal via Pliocene river connections. The two taxa were found to be very closely related, in a pattern which indicates that they should be treated as a single species or subspecies rather than fully separate species; this finding strongly supports recent long-distance dispersal of a common ancestor into central Australia. Two types of long-distance dispersal vectors are considered by Kondo et al. [1]: fruit-eating birds and bats, or humans. The former vectors are known to consume and distribute the seeds. Early human colonizers were present (at least sporadically) in central Australia during the timeframe established for genetic divergence between the two palms [6]. Moreover, the growing shoot (palmheart) of L. mariae was eaten as a vegetable [7], which may have provided an incentive for humans to attempt to establish populations in new areas. As discussed by Kondo et al. [1], the vast distance between L. rigida and L. mariae (ca 1000 km) makes it highly improbable that birds or bats dispersed the seeds. Therefore, human dispersal remains the only plausible explanation for L. mariae in central Australia.