Riding the ice age El Niño? Pacific biogeography and evolution of Metrosideros subg. Metrosideros (Myrtaceae) inferred from nuclear ribosomal DNA

Abstract

Metrosideros subg. Metrosideros (Myrtaceae) comprises Ϸ26 species distributed widely across the Pacific basin. They occur on the ancient Gondwanan landmasses of New Zealand and New Caledonia, as well as on the volcanic islands of the remote Pacific, from Melanesia to tropical Polynesia and the Bonin Island. Phylogenetic analysis based on nuclear ribosomal DNA spacer sequences from all named species showed Metrosideros umbellata of New Zealand as basal in the subgenus, with the remaining species falling into three monophyletic clades. One includes the seven New Caledonian species together with three daughters in western Oceania that probably dispersed during the mid͞late Tertiary. A second contains six taxa located in east Melanesia and Samoa that may also have arisen from a mid͞late Tertiary dispersal, in this instance from New Zealand. The third includes three New Zealand endemics along with all of the taxa in remote Polynesia and accounts for much of the total range of the subgenus. These dispersed taxa in Polynesia either are identical to the New Zealand species Metrosideros excelsa or differ by a single nucleotide change. We suggest that they are all derived from a Pleistocene dispersal out of New Zealand. A relatively recent dispersal is surprising, given that this winddispersed genus has occupied New Zealand for much of the Tertiary and that some of the islands in remote Polynesia date to at least the Miocene. We attribute this dramatic range expansion to climate change-specifically changes in wind flow patterns-in the southern hemisphere during worldwide glaciation.climate change ͉ dispersal

Using matK sequence data to unravel the phylogeny of Casuarinaceae

“…Recently, Swenson et al (2001) hypothesised that Nothofagus had reached New Caledonia via long distance dispersal from New Zealand, and that the closely related group of extant species there have probably evolved from a single colonist species. A similar scenario may well be true for Gymnostoma-as well as New Caledonian species of Araucaria, Agathis (Setoguchi et al, 1998) and Metrosideros (Wright et al, 2000(Wright et al, , 2001)-and would explain the well defined clade of extant species in New Caledonia. This hypothesis requires further testing to distinguish it from the possiblity that the New Caledonian species are descendents from a single Gondwanan ancestor.…”

Progressive island colonization and ancient origin of Hawaiian Metrosideros (Myrtaceae)

“…The presence of Metrosideros throughout the Pacific region has long been considered the result of highly effective dispersal via small wind dispersed seeds that can be transported by air currents over long distances and endure periods of immersion in salt water (Corn 1972;Carlquist 1974;Wright et al 2000Wright et al , 2001. Such efficient dispersal should make the repeated colonization of islands more likely.…”

Dispersals of Hyoscyameae and Mandragoreae (Solanaceae) from the New World to Eurasia in the early Miocene and their biogeographic diversification within Eurasia

“…Taxa with small propagules such as Metrosideros Banks ex Gaertn. of Myrtaceae (Wright et al, 2000), orchids (Carlquist, 1996;Winkworth et al, 2002) and ferns (Mcglone et al, 2001) may disperse over long-distances via winds. Lycium L. (Solanaceae) has been suggested to be dispersed in a single event by birds from the New World to Eurasia followed by spreading into southern Africa (Fukuda et al, 2001;Levin and Miller, 2005).…”