Evolutionary origins of Gondwanan interactions: How old are Araucaria beetle herbivores?

Abstract

Studies of a variety of phenomena, ranging from rates of molecular substitution to rates of diversification, draw on estimates of geological age. Studies incorporating estimates of timing from fossils or other geological evidence are largely of relatively young, Tertiary divergences, to which older systems may provide useful comparisons. One apparently old assemblage comprises the beetle groups associated with the ancient genus Arau,caria that share comparable, ostensibly Gondwanan distributions with their host. Our previous studies suggested a possibly Cretaceous age for Araucaria associations in bark beetles. However, the absence of confirmed bark beetle fossils earlier than the Tertiary has been taken as evidence of Cretaceous absence, and their confirmed phylogenetic position within the primitively angiosperm-feeding weevil family rules out pre-angiosperm, Jurassic origins. Nevertheless, an early shift from angiosperms t o Araucaria seemed plausible in the light of Araucaria fossil history which spans the Mesozoic since the Jurassic. To resolve the phylogenetic affinities and to estimate divergence times of the Australian and South American bark beetle genera affiliated with Araucaria we analysed DNA sequences of nuclear and mitochondria1 genes: protein coding elongation factor alpha, enolase and cytochrome oxidase I. The most parsimonious reconstruction of the host relationships of Tomicini from the combined dataset corroborates the ancestral association with the genus Araucaria of both South American and Australian Tomicini. Bayesian estimation of divergence times indicates that the divergence between the Australian and the South American Araucaria-feeding taxa occurred at the very latest in the Cretaceous/Paleocene border and that the age of the first Scolytinae-Araucaria association would then be during the later stages of the Late Cretaceous, while other known beetle/Araucaria associations are Jurassic. 0 2001 The Linnean Society of LondonADDITIONAL KEY WORDS: Tomicinibark beetles -South America -Australiaphylogenycytochrome oxidase Ielongation factor l aenolase -Bayesian inferenceage estimation -Late Cretaceous divergence.

Temporal lags and overlap in the diversification of weevils and flowering plants

“…Some curculionid tribes are intimately associated with gymnosperms; however, they are all nested within clades of angiospermfeeders. Thus, while some primitive weevils may be primary associates of gymnosperms (e.g., certain Nemonychidae, Belidae, Attelabidae, and Caridae), others, such as gymnospermassociated Curculionidae and Brentidae, are most likely secondary colonists, an interpretation consistent with other authors (2,11,18,31,32). † Basal Curculionidae most likely first colonized core eudicots and certain other land-plant groups that were locally abundant, unoccupied, or underexploited by other herbivores, and occurred in close ecological association with their ancestral mono- † Supported by their comparatively early appearance in the fossil record (when known), Gondwanan distributions (at least of the oldest, and often conifer-associated lineages), and phylogenetic position, generally at the base of their respective groups (6).…”

Biogeography and divergence times in the mulberry family (Moraceae)

“…5). Second, the best examples of this phytogeographic pattern come from warm temperate and tropical montane lineages such as Nothofagaceae (Manos, 1997) and Araucariacae (Sequeira and Farrell, 2001) while the Moraceae are dominated by lowland tropical lineages. In order for a southern hemisphere origin and vicariance to be plausible after Africa and India had separated from Gondwanaland, a trans-Antarctic pathway must be invoked during the early Tertiary at the time when the New and Old World lineages diverged (Fig.…”

“…By the time angiosperms originated in the early Cretaceous (Magallón and Sanderson, 2001), the supercontinent of Pangea had already split into Gondwanaland in the southern hemisphere and Laurasia in the north. Many extant plant lineages are distributed across these former landmasses, and vicariance and dispersal events have been invoked to support or reject scenarios of Gondwanan versus Laurasian origin (Bremer, 2002;Manos, 1997;Sequeira and Farrell, 2001).…”

“…Machado et al (2001) developed a biogeographic hypothesis for Ficus on the assumption that Wg and Wg wasp origins were temporally and geographically congruent owing to the complete reproductive interdependence of the mutualists. This assumption has enabled the ages of other specialized plant-insect interactions to be estimated (Machado et al, 2001;Pellmyr and Leebens-Mack, 1998;Sequeira and Farrell, 2001) but few studies have compared independent divergence times for interacting lineages (Percy et al, 2004).…”

The sudden emergence of pathogenicity in insect–fungus symbioses threatens naive forest ecosystems

“…(b) From phloem-feeders to fungus farmers The ancestral diet of bark and ambrosia beetles was freshly dead phloem [20], and their most common fungal associates were weakly pathogenic fungi [21]. The association between phloem-feeding beetles and fungi has repeatedly evolved into a variety of other relationships.…”