Abstract
BackgroundThe genus Acronychia (Citrus family, Rutaceae) contains 49 species of trees and shrubs that are found mainly in rain forest. The genus has a large distributional range from mainland southern Asia to Australia and New Caledonia, but most species are endemic to either New Guinea or Australia. This study aimed to provide the first detailed molecular phylogeny of Acronychia and use it to test the taxonomic value of fruit morphological characters, and infer the historical biogeography of the genus.MethodologyPhylogenetic analyses (Bayesian Inference, Maximum Likelihood) were undertaken on nucleotide sequence data from two plastid (psbA-trnH, trnL-trnF) and three nuclear markers (ETS, ITS, NIAi3) from 29 Acronychia species (59% of the genus) and representatives of related genera.Results and ConclusionsThe results indicate that the South-East Asian genus Maclurodendron is nested phylogenetically within Acronychia and must be synonymized to render Acronychia monophyletic. Fruit morphological characters have been used previously to infer relationships within Acronychia and our analyses show that these characters are informative for some subclades but are homoplasious for the group as a whole. Apocarpous fruits are the ancestral state in Acronychia and subapocarpous and fully syncarpous fruits are derived. The unisexual flowers of Maclurodendron are derived from bisexual flowers, which are found in all species of Acronychia as well as its relatives. Acronychia probably first evolved on Australia with range expansion to New Guinea via stepping-stone dispersal or direct land connections within the Sahul Shelf, followed by two independent dispersals to areas west of New Guinea. Most species of Acronychia occur in either Australia or New Guinea, but no species occurs in both regions. This is surprising given the close proximity of the landmasses, but might be explained by ecological factors.
Highlights
Acronychia belongs to a clade of mainly Australasian rain forest genera in the citrus family, Rutaceae [1, 2]
The results indicate that the South-East Asian genus Maclurodendron is nested phylogenetically within Acronychia and must be synonymized to render Acronychia monophyletic
Fruit morphological characters have been used previously to infer relationships within Acronychia and our analyses show that these characters are informative for some subclades but are homoplasious for the group as a whole
Summary
Acronychia belongs to a clade of mainly Australasian rain forest genera in the citrus family, Rutaceae [1, 2]. Very few species occur outside of this area and the relatively large distribution area of the genus as a whole is mainly due to two species: A. pedunculata, which is distributed in southern Asia from India to Taiwan and throughout the Malesian region; and A. trifoliolata, which occurs from Java and Sulawesi to the Solomon Islands. The genus Acronychia (Citrus family, Rutaceae) contains 49 species of trees and shrubs that are found mainly in rain forest. The genus has a large distributional range from mainland southern Asia to Australia and New Caledonia, but most species are endemic to either New Guinea or Australia. This study aimed to provide the first detailed molecular phylogeny of Acronychia and use it to test the taxonomic value of fruit morphological characters, and infer the historical biogeography of the genus
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