The Southern Conifer Family Araucariaceae: History, Status, and Value for Paleoenvironmental Reconstruction

Abstract

The Araucariaceae are important to biogeography because they have an ancient origin and are a distinctive and sometimes dominant component of southern hemisphere forest communities. This paper examines recent information on ecology and phylogeny and on pollen and macrofossil assemblages to assess the history and present-day status of the family and its potential for refinement of past environmental, particularly climatic, conditions. From an origin in the Triassic, the family expanded and diversified in both hemispheres in the Jurassic and Early Cretaceous and remained a significant component of Gondwanan vegetation until the latter part of the Cenozoic. The development of angiosperms in the Middle Cretaceous probably assisted in the demise of some araucarian components but there was also evolution of new genera. Recorded diversity in the early Cenozoic of Australia is as high as it was in the Early Cretaceous. Continental separation and associated climatic drying, cooling, and increased variability progressively reduced the ranges of conifers to moist, predominantly mesothermal climates on continents. However, tectonic and volcanic activity, partially associated with Australia's collision with Southeast Asia, provided new opportunities for some araucarian components on Asia-Pacific islands. Araucarians provide information on climatic conditions suitable for rainforest vegetation throughout their recorded period, even prior to the recognition or even existence of these forests in the fossil record. High pollen abundance is also indicative of marginal rainforest environments where these canopy emergents can compete effectively with angiosperm forest taxa. Despite their apparent relictual status in many areas, they provide precise paleoclimatic estimates in late Quaternary pollen records and have particular value in providing evidence of climatic variability that has otherwise been difficult to detect.

Determination of the molecular signature of fossil conifers by experimental palaeochemotaxonomy – Part 1: The Araucariaceae family

“…These phylogenitic relationships of Araucariaceae species were also confirmed by Setoguchi et al (1998) based on rbcL gene sequences: most Agathis species occupy the tropical islands (Dettmann and Clifford, 2005). These two genera, extending within the equatorial region of New Guinea and Southeast Asia at lower latitude grow under a mesothermal climate, limited to the lower montane zone (Kershaw and Wagstaff, 2001). The monotypic genus Wollemia is by far the most endemic genus and its few wild species (about 40 adult plants) live deep in a wilderness rainforest of the Wollemi National Park in New South Wales (Australia).…”

“…The first pollen record is from the early Triassic of Australia (as ancestor) just after the Permo-Triassic extinction, and the unequivocal Araucariaceae representatives were found in the Middle Jurassic of North Yorkshire (Stockey, 1982;Kershaw and Wagstaff, 2001;Kunzmann, 2007b). The maximum worldwide distribution was achieved in both hemispheres during the Cretaceous (Krassilov, 1978;Kunzmann, 2007b).…”

“…During the Jurassic, Araucaria (especially the Eutacta and the Bunya sections) was the first genus to appear and diversify. Its macrofossils and pollens broadened a wide range of habitats in the two hemispheres (Gondwana and Laurasia), where Jurassic climate condition was subtropical to warmtemperate (Kershaw and Wagstaff, 2001). During the Cretaceous, the first effective Agathis and Wollemia fossils appeared, but remained restricted to Australia and New Zealand (Hill and Bigwood, 1987;Stockey, 1994).…”

Biological activities and chemical constituents of Araucaria angustifolia : An effort to recover a species threatened by extinction

“…The genus Araucaria includes approximately nineteen species, all confined to the Southern Hemisphere (Kershaw and Wagstaff, 2001). Two species grow in South America, Araucaria angustifolia and Araucaria araucana.…”

Improved method for isolation of coupled mitochondria of Araucaria angustifolia (Bert.) O. Kuntze

“…The Araucariaceae family has an ancient origin in the Triassic Period and the araucarians appear to have maintained a preference for subtropical or mesothermal conditions, illustrated by the present distribution of A. angustifolia in southern Brazil (Kershaw and Wagstaff, 2001). A comparison between this ancient gymnosperm and the much more studied angiosperm mitochondria (Beavis and Vercesi, 1992;Fortes et al, 2001;Calegario et al, 2003;Ruy et al, 2004;Camacho et al, 2004) could be of great importance.…”