scholarly journals Relaxed Molecular Clock Provides Evidence for Long-Distance Dispersal of Nothofagus (Southern Beech)

PLoS Biology ◽  
2005 ◽  
Vol 3 (1) ◽  
pp. e14 ◽  
Author(s):  
Michael Knapp ◽  
Karen Stöckler ◽  
David Havell ◽  
Frédéric Delsuc ◽  
Federico Sebastiani ◽  
...  
2011 ◽  
Vol 59 (3) ◽  
pp. 262 ◽  
Author(s):  
Gunnar Keppel ◽  
Peter Prentis ◽  
Ed Biffin ◽  
Paul Hodgskiss ◽  
Susana Tuisese ◽  
...  

We examined evolutionary relationships, hybridisation and genetic diversity in species of Dacrydium (Podocarpaceae) in Remote Oceania, where it is restricted to New Caledonia and Fiji. We used cpDNA sequence (trnL–trnF) data to construct a phylogeny and estimate taxon divergence by using a relaxed molecular clock approach. The phylogeny was verified using allozymes, which were also used to investigate genetic diversity of all species and the hybridisation dynamics of two endangered species, D. guillauminii and D. nidulum. Our results suggested that Dacrydium species in Remote Oceania form a monophyletic group that arose and diversified within the last 20 million years through long-distance dispersal and a range of speciation mechanisms. Whereas we detected no hybridisation between the Fijian species D. nausoriense and D. nidulum, we confirmed hybridisation between D. guillauminii and D. araucarioides in New Caledonia and determined introgression to be assymetric from the widespread D. araucarioides into the rare, restricted-range species D. guillauminii. In addition, D. guillauminii had lower genetic diversity than did the other species of Dacrydium studied, which had genetic diversity similar to that of other gymnosperms. Our results provided evidence for the recent and complex diversification of Dacrydium in Remote Oceania. In addition, low genetic diversity of and introgression from D. araucarioides, are of grave concern for the conservation of D. guillauminii.


2020 ◽  
Vol 33 (1) ◽  
pp. 103
Author(s):  
D. F. Comben ◽  
G. A. McCulloch ◽  
G. K. Brown ◽  
G. H. Walter

The genus Vachellia Wight & Arn. has a pantropical distribution, with species being distributed through Africa, the Americas, Asia and Australia. The relationships among the lineages from Africa and America are well understood, but the phylogenetic placement and evolutionary origins of the Australian species of Vachellia are not known. We, therefore, sequenced four plastid genes from representatives of each of the nine Australian species of Vachellia, and used Bayesian inference to assess the phylogenetic placement of these lineages, and a relaxed molecular clock to assess the timing of diversification. The Australian species of Vachellia form a well-supported monophyletic clade, with molecular-dating analysis suggesting a single dispersal into Australia 6.5 million years ago (95% range 13.9–2.7 million years ago). Diversification of the Australian clade commenced more recently, c. 3.1 million years ago (95% range 9.2–1.2 million years ago), perhaps driven by the increased aridification of Australia at this time. The closest relatives to the Australian Vachellia were not from the Malesian bioregion, suggesting either a long-distance dispersal from Africa, or two separate migrations through Asia. These results not only improve our understanding of the biogeography of Vachellia species, but also have significant implications for the biological control of invasive Vachellia species in Australia.


2001 ◽  
Vol 49 (3) ◽  
pp. 333 ◽  
Author(s):  
Gregory J. Jordan

Some 200 species of plants are currently recognised as being native to both Tasmania and New Zealand. It is argued that dispersal across the 1500–2000-km Tasman Sea has occurred in all of these species. Almost all (187) are herbs and constitute over 20% of the herbaceous flora of Tasmania. Common species, non-dioecious species, species with very small seeds, species from aquatic, coastal or wet habitats and possibly species with hooked fruit are all over-represented among the disjunct species of herbs. The incidence of disjunct species also varies significantly among families. In contrast, fleshy fruited species, or species with plumes or very hairy disseminules, are not over-represented among the herbaceous disjunct species. These data are used to model the probability that a species (past or present) with given traits would show a within-species trans-Tasman disjunction, and it is inferred that this can be used to give a crude approximation of the rates of long-distance dispersal for different types of species. The model can be tested by using molecular clock methods and could be made more robust by incorporating equivalent data from other disjunct regions.


2015 ◽  
Vol 39 (1) ◽  
pp. 290-293 ◽  
Author(s):  
Elizabeth A. Sinclair ◽  
Renae Hovey ◽  
John Statton ◽  
Matthew W. Fraser ◽  
Marion L. Cambridge ◽  
...  

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