Conifer Families Evolution and Distribution
Conifers are classed as Gymnosperms because they have “naked seeds” which are not surrounded by an ovary. Gymno comes from the Greek for “naked”. Conifers have leaves that are needle-like or scale-like. They bear pollen and seed cones, not flowers and fruit. The word “Conifer” means cone-bearing. Wood from Conifers is called Softwood. Pine, Spruce, Cedar and Cypress are softwoods used in furniture manufacture. Only three conifers grow naturally in Britain – Scots Pine, Common Juniper and Yew. All the others have been introduced.
A Family is defined as a group of plants that share common characteristics and evolutionary history. A family is a taxonomic level. The two levels below it are the genus (plural genera) and the species. A Family usually consists of several genera. Conifer families evolution and distribution has been studied in detail in recent years as DNA analysis has allowed researchers to determine how closely plant species are related and how they evolved over time. It also allows researchers to combine fossil records and DNA analysis to examine the current distribution of species and explain how this has been influenced by climate change and geological events. There are estimated be 628 species of conifers in the world arranged in 7 families. These are shown in the table below along with the Ginkgo family which is usually included in literature on conifers, even though it is a gymnosperm not a conifer.
Ginkgo family. Also known as the Maidenhair Tree, the Ginkgo is a Gymnosperm but is strictly not a Conifer. It has catkin-like pollen cones like a Conifer but does not produce seed cones. Its seeds develop into round green fruits on the end of stalks. The fertilisation process involves motile sperm, a feature of Mosses, Liverworts and Ferns. Hence it is in a botanical class of its own and is often referred to as a “living fossil”. The Ginkgo, is the only surviving member of a family, which has existed since the Permian period 270 million years ago and the only surviving member of the Ginkgo genus, which has existed since the Jurassic era 180 million years ago. Fossil records indicate that various species of Ginkgo have existed in different parts of the world but, over time, the number of Ginkgo species has declined, leaving Gingko biloba as the only surviving species. The tree is native to a small area of China where it has been cultivated for centuries for its apricot-like “fruit”. In the forests of China individual trees may live for more than 3000 years. It was introduced to Britain in 1758 and has been planted widely in southern England, in large gardens, parks and new towns. To learn more about the Ginkgo click HERE.
Conifers There are fossil records of primitive conifers in the late Carboniferous period 300 million years ago. By the late Triassic 200 million years ago conifers were diverse and by the end of the Jurassic 145 Million years ago most of today’s conifer families had appeared. The forests were dominated by conifers with some tree ferns, cycads and ginkgos. With the appearance of angiosperms (flowering plants) 140 million years ago, conifers became less dominant and retreated to habitats that gave them an advantage over the rapidly diversifying angiosperms. Today they are found in areas with short growing seasons – northern latitudes or high altitudes – or arid areas that inhibit angiosperms. In the southern hemisphere, however, podocarps are found in tropical forests growing alongside angiosperms. Between the Early Triassic (250 million years ago)and the Middle Jurassic (175 million years ago), virtually all continents existed in the form of the supercontinent Pangea. Around 160 – 138 million years ago, Pangea broke up into two supercontinents: Laurasia, comprising land that eventually gave rise to North America, Europe, and much of Asia, and Gondwana, made up of land that subsequently gave rise to South America, Africa, India, Antarctica, and Australia. Cupressaceae originated during the period when Pangea was intact but then split into two sub-families, one in Laurasia and one in Gondwanaland. There are estimated be 628 species of conifers in the world. Pinaceae (232) and Taxaceae (17) are in the Northern Hemisphere, Podocarpaceae (174) Araucariaceae (41) and Cephalotaxaceae (11) are in the Southern Hemisphere and Cupressaceae (152) is split between Northern and Southern hemispheres. In total there are 363 species in the Northern Hemisphere and 265 in the Southern Hemisphere.
Conifer Families Evolution. This figure shows how the different conifer families are related. The Pinaceae family evolved first and gave rise to later forms of conifer. The ancestral conifers are believed to have had leaves that resembled those of modern-day ferns and were more broad and flat. Over time, conifers underwent adaptations that led to the development of specialised needle-like or scale-like leaves. In the late Permian (250 million years ago) seed cones diverged. In Pinaceae, Araucariaceae, Sciadopityaceae and most Cupressaceae, the cones are woody, and when mature the scales usually spread open allowing the seeds to fall out and be dispersed by the wind. In the families Podocarpaceae, Cephalotaxaceae, Taxaceae, and one Cupressaceae genus (Juniperus), the scales are soft, fleshy, sweet and brightly coloured, and are eaten by fruit-eating birds, which then pass the seeds in their droppings.
Pine family (Pinaceae):
This is the conifer family with the largest number of species (232). It includes familiar species like Pines, Firs, Spruces, Cedars, Larches and Hemlocks. The fossil record of the Pinaceae family extends back to the Mesozoic Era (200 million years ago). For more information on this family click HERE to go to the Conifer Cone Key
Pines (genus Pinus) are the most diverse and widespread group within the Pinaceae family with over 120 species. The oldest pine tree fossil found was dated at 140 million years ago. Pines can be found in a variety of habitats, ranging from tropical to subarctic regions in the Northern Hemisphere and are particularly abundant in North America, where they occupy vast forests across the continent. They are also present in Europe, Asia, and parts of Africa. The Douglas Fir (genus Pseudotsuga) is native to western North America and is particularly abundant in the coastal regions of the Pacific Northwest, where it forms extensive forests. Firs (genus Abies) with over 50 species are primarily found in the Northern Hemisphere, including North America, Europe, and Asia. Firs generally prefer cooler climates and are often found in mountainous regions. Spruces (genus Picea) with over 35 species are also found in the Northern Hemisphere. They are well-adapted to cold and boreal climates and are common in forests across North America, Europe, and Asia. Cedars (genus Cedrus) includes 3 species – Atlas Cedar, native to the Atlas Mountains of Morocco and Algeria in North Africa,Deodar Cedar native to the western Himalayas in parts of India, Pakistan, Afghanistan, and Nepal and Lebanon Cedar native to the mountains of Lebanon, western Syria, and southwestern Turkey. Larch (genus Larix) consists of about 12 species – European Larch, native to the mountains of central Europe, Siberian Larch which forms extensive forests in Siberia, Japanese Larch, Eastern Larch, also known as Tamarack, found in the northern parts of the United States and Canada. Hemlocks (genus Tsuga) with 10 species are primarily found in eastern North America and eastern Asia. They thrive in moist, cool environments, such as forests near streams and rivers.
Monkey Puzzle family (Araucariaceae):
The origins of the Araucariaceae family can be traced back to the late Triassic period, around 200 million years ago. Fossil evidence suggests that the family first evolved in what is now the Southern Hemisphere, with Gondwana playing a crucial role in its early diversification.The family diversified and flourished during the Jurassic and Cretaceous periods, with widespread distribution across Gondwana. The family’s evolution continued through the fragmentation of continents and changing climatic conditions. There are 40 species in this family which includes the two genera Araucaria (20) Monkey Puzzle trees and Agathis (19) Kauri trees. They are primarily found in the Southern Hemisphere, specifically in regions with a temperate or tropical climate. Kauri trees are large evergreen conifers native to the Pacific region, including Southeast Asia, New Guinea, Australia, and some Pacific Islands. Monkey Puzzle trees are found in South America, New Guinea, Australia, New Caledonia and Norfolk island. New Caledonia in the Pacific Ocean, 1200km east of Australia, is home to 19 of the Araucariaceae species and 19 Podocarpaceae species.
Podocarp family (Podocarpaceae):
The family is a diverse group of conifers that primarily inhabit the Southern Hemisphere, including regions such as Australasia, South America, and Africa. The family probably originated 150million years ago in the supercontinent Gondwana. The Araucariaceae and Podocarpaceae families share similarities and are considered sister groups, meaning they are closely related and share a recent common ancestor. With the fragmentation of Gondwana during the Cenozoic era (66million years ago), the Podocarpaceae family became geographically isolated on different continents.
Podocarpaceae species are most diverse and abundant in Australasia (Australia, New Zealand, and neighbouring islands such as New Caledonia, Papua New Guinea), and Southeast Asia. Podocarpaceae species can also be found in South America, particularly in Chile and Argentina. Some Podocarpaceae species are found in Africa, mainly in tropical and subtropical regions, Podocarpus trees in South Africa are grown for timber and are known as Yellowwoods. Several Podocarpaceae species can be found in Pacific Island nations, including Fiji, Samoa, and the Solomon Islands. Shown here is a young Podocarpus totora.
Cypress and Redwood family (Cupressaceae): For more information on this family click HERE to go to the Conifer Cone Key
There are 152 species in this family of which 119 are in the Northern Hemisphere and 33 in the Southern Hemisphere. The family includes many well-known species such as Cypresses (genus Cupressus 26 species and genus Chamaecyparis 6 species), Juniper (genus Juniperus 66 species), Thuja (5 species including the Western Red Cedar), Coast and Dawn Redwoods, Giant Sequoia, Swamp Cypress, Japaneses Red Cedar and Incense Cedar. The family originated during the Triassic 200 million years ago when the super continent Pangea was intact. Around 160 – 138 million years ago, Pangea broke up into two supercontinents: Laurasia, comprising what are now North America, Europe, and much of Asia, and Gondwana which gave rise to South America, Africa, India, Antarctica, and Australia. Cupressaceae originated during the period when Pangea was intact but then split into two sub-families, one in Laurasia and one in Gondwana.In the Northern Hemisphere many Cupressaceae species are found in the Pacific Northwest of the USA e.g. Coast Redwood, Giant sequoia, Western Red Cedar and Lawson Cypress. In Asia notable species include the Hinoki Cypress, Japanese Red Cedar and the Dawn Redwood recently discovered in central China. In Europe the Italian Cypress is native to countries around the Mediterranean basin, including Greece, Italy, and Turkey. Junipers are widely distributed throughout the Northern Hemisphere in many habitats from the arctic to the tropics. Common juniper is the most widespread conifer in the world. It occurs across the Northern hemisphere from North America, Europe, northern Asia to Japan. In the Southern Hemisphere Cupressaceae species are found in Central and South America. The Alerce (Fitzroya cupressoides) is found in the Andes of Chile and Argentina. It is the largest tree in South America. In Africa the African Cypress (genus Widdringtonia) is native to countries such as South Africa, Zimbabwe, and Mozambique. In Australia and some Pacific islands the genus Callitris has 15 species, known as Cypress-pines which grow in arid regions.
Plum Yew family (Cephalotaxaceae): The family consists of a single genus of 11 species of evergreen trees and shrubs known as Plum Yews. The family is primarily found in East Asia, specifically in countries such as China, Japan, and Taiwan and its fossils can be dated back to the Jurassic period (about 201 to 145 million years ago). These fossils indicate that the family has remained relatively unchanged over millions of years. The family tends to thrive in cool temperate forests and mountainous areas with moist soil conditions. Shown here are the foliage and cones of the Chinese Plum Yew Tree
Yew family (Taxaceae):
The family consists of 17 species of evergreen trees and shrubs. They generally prefer shady, moist environments and are often found in forests, woodlands, and mountainous regions. The family is known for its main genus Taxus, common name Yew. Fossil evidence suggests that Taxaceae-like plants existed as early as the Triassic period (about 252 to 201 million years ago). They are now primarily found in temperate regions of the Northern Hemisphere, in Europe (Common Yew), Asia (Himalayan, Chinese and Japanese Yews), and North America (Canada and Pacific Yews).