Australian biogeographical connections and the phylogeny of large genera in the plant family Myrtaceae

Abstract

Aim To compare the phylogeny of the eucalypt and melaleuca groups with geological events and ages of fossils to discover the time frame of clade divergences. Location Australia, New Caledonia, New Guinea, Indonesian Archipelago. Methods We compare published molecular phylogenies of the eucalypt and melaleuca groups of the plant family Myrtaceae with geological history and known fossil records from the Cretaceous and Cenozoic. Results The Australasian eucalypt group includes seven genera, of which some are relictual rain forest taxa of restricted distribution and others are species‐rich and widespread in drier environments. Based on molecular and morphological data, phylogenetic analyses of the eucalypt group have identified two major clades. The monotypic Arillastrum endemic to New Caledonia is related in one clade to the more species‐rich Angophora, Corymbia and Eucalyptus that dominate the sclerophyll vegetation of Australia. Based on the time of rifting of New Caledonia from eastern Gondwana and the age of fossil eucalypt pollen, we argue that this clade extends back to the Late Cretaceous. The second clade includes three relictual rain forest taxa, with Allosyncarpia from Arnhem Land the sister taxon to Eucalyptopsis of New Guinea and the eastern Indonesian archipelago, and Stockwellia from the Atherton Tableland in north‐east Queensland. As monsoonal, drier conditions evolved in northern Australia, Arnhem Land was isolated from the wet tropics to the east and north during the Oligocene, segregating ancestral rain forest biota. It is argued also that the distribution of species in Eucalyptopsis and Eucalyptus subgenus Symphyomyrtus endemic in areas north of the stable edge of the Australian continent, as far as Sulawesi and the southern Philippines, is related to the geological history of south‐east Asia‐Australasia. Colonization (dispersal) may have been aided by rafting on micro‐continental fragments, by accretion of arc terranes onto New Guinea and by land brought into closer proximity during periods of low sea‐level, from the Late Miocene and Pliocene. The phylogenetic position of the few northern, non‐Australian species of Eucalyptus subgenus Symphyomyrtus suggests rapid radiation in the large Australian sister group(s) during this time frame. A similar pattern, connecting Australia and New Caledonia, is emerging from phylogenetic analysis of the Melaleuca group (Beaufortia suballiance) within Myrtaceae, with Melaleuca being polyphyletic. Main conclusion The eucalypt group is an old lineage extending back to the Late Cretaceous. Differentiation of clades is related to major geological and climatic events, including rifting of New Caledonia from eastern Gondwana, development of monsoonal and drier climates, collision of the northern edge of the Australian craton with island arcs and periods of low sea level. Vicariance events involve dispersal of biota.

Microsatellites retain phylogenetic signals across genera in eucalypts (Myrtaceae)

“…The outgroup taxa formed a clade at the base of the tree, with the relationship (Stockwellia, Eucalyptopsis + Allosyncarpia). On flower development, the clade of these three rainforest genera had the relationship: Allosyncarpia, (Stockwellia + Eucalyptopsis) (Carr et al, 2002;Ladiges et al, 2003), which was also supported by Parra-O et al (2006) based on a combined data set of nrETS and ITS. The monophyly of Corymbia has previously been proposed based on morphological and anatomical characters (Hill and Johnson, 1995;Ladiges et al, 1995), and recently, by DNA data from the ETS (Parra-O et al, 2006).…”

“…This observation may indicate that Eucalyptus is a faster evolving clade, thereby accumulating more mutations in the flanking sequences of the SSRs. SSR analysis excluded Arillastrum because available morphological and molecular data (Hill and Johnson, 1995;Udovicic and Ladiges, 2000;Wilson et al, 2001;Steane et al, 2002) put this genus the farthest from Corymbia among the eucalypts; Ladiges et al (2003) suggested, based on biogeography, that the divergence of Arillastrum from the other eucalypt genera may be as old as Late Cretaceous (70 MYA; see also Crisp et al (2004). These data suggested a potentially low prospect of transferring Corymbia SSRs to Arillastrum.…”

“…In the case of eucalypt genera Corymbia and Angophora, the differentiation in question is among species rather than just between populations of the same species. Hence the between species and between genera F ST values are expected to be large since the two genera have diverged for tens of millions of years (Ladiges et al, 2003). Apart from SSRs, proteins have been used in phylogenetic reconstruction.…”

Flammable biomes dominated by eucalypts originated at the Cretaceous–Palaeogene boundary

“…Why then have eucalypts not taken over the seasonally dry regions of the world? During the Miocene, eucalypts were present in New Zealand and Southeast Asia in association with other sclerophyll and xeric flora, such as acacias, chenopods and Casuarinaceae 7,29,30 . At this time, there was an abundance of charcoal, indicating frequent burning in these communities 29,30 .…”

Leaf micromorphology and anatomy of Myrceugenia rufa (Myrtaceae). An endemic coastal shrub of north-central Chile

“…is a pantropical family of trees and shrubs with approximately 5500 species, divided into two subfamilies, 17 tribes and 142 genera (Wilson et al 2005, Govaerts et al 2008). This family is particularly diverse in the southern hemisphere (Ladiges et al 2003), with a high diversity in Central America (McVaugh 1968), South America (Landrum 1988) and Australia (Lucas et al 2007, Thornhill & Crisp 2012. The members of this family are woody, with entire, simple, evergreen and mostly opposite leaves, with internal phloem and oil glands (Ciccarelli et al 2008, Cronquist 1981, Metcalfe & Chalk 1979.…”