Turner Review No. 2Southern Conifers in Time and Space

The three southern conifer families, Araucariaceae, Cupressaceae and Podocarpaceae, have a longhistory and continue to be an important part of the vegetation today. The Araucariaceae have the mostextensive fossil record, occurring in both hemispheres, and with Araucaria in particular having anancient origin. In the Southern Hemisphere Araucaria and Agathis have substantial macrofossil records,especially in Australasia, and Wollemia probably also has an important macrofossil record. At least oneextinct genus of Araucariaceae is present as a macrofossil during the Cenozoic. Cupressaceaemacrofossils are difficult to identify in older sediments, but the southern genera begin their record in theCretaceous (Athrotaxis) and become more diverse and extensive during the Cenozoic. Several extinctgenera of Cupressaceae also occur in Cretaceous and Cenozoic sediments in Australasia. ThePodocarpaceae probably begin their macrofossil record in the Triassic, although the early history is stilluncertain. Occasional Podocarpaceae macrofossils have been recorded in the Northern Hemisphere, butthey are essentially a southern family. The Cenozoic macrofossil record of the Podocarpaceae isextensive, especially in south-eastern Australia, where the majority of the extant genera have beenrecorded. Some extinct genera have also been reported from across high southern latitudes, confirmingan extremely diverse and widespread suite of Podocarpaceae during the Cenozoic in the region.In the Southern Hemisphere today conifers achieve greatest abundance in wet forests. Those whichcompete successfully with broad-leaved angiosperms in warmer forests produce broad, flatphotosynthetic shoots. In the Araucariaceae this is achieved by the planation of multiveined leaves intolarge compound shoots. In the other two families leaves are now limited to a single vein (exceptNageia), and to overcome this limitation many genera have resorted to re-orientation of leaves and twodimensionalflattening of shoots. The Podocarpaceae show greatest development of this strategy with 11of 19 genera producing shoots analogous to compound leaves. The concentration of conifers in wetforest left them vulnerable to the climate change which occurred in the Cenozoic, and decreases indiversity have occurred since the Paleogene in all regions where fossil records are available. Informationabout the history of the dry forest conifers is extremely limited because of a lack of fossilisation in suchenvironments. The southern conifers, past and present, demonstrate an ability to compete effectivelywith angiosperms in many habitats and should not be viewed as remnants which are ineffectual againstangiosperm competitors.