Nothofagus


Nothofagus, also known as the southern beeches, is a genus of 43 species of trees and shrubs native to the Southern Hemisphere in southern South America and Australasia. The species are ecological dominants in many temperate forests in these regions. Some species are reportedly naturalised in Germany and Great Britain. The genus has a rich fossil record of leaves, cupules, and pollen, with fossils extending into the late Cretaceous period and occurring in Australia, New Zealand, Antarctica, and South America. In the past, they were included in the family Fagaceae, but genetic tests revealed them to be genetically distinct, and they are now included in their own family, the Nothofagaceae.
The leaves are toothed or entire, evergreen or deciduous. The fruit is a small, flattened or triangular nut, borne in cupules containing one to seven nuts.
Nothofagus species are used as food plants by the larvae of hepialid moths of the genus Aenetus, including A. eximia and A. virescens.
Many individual trees are extremely old, and at one time, some populations were thought to be unable to reproduce in present-day conditions where they were growing, except by suckering, being remnant forest from a cooler time. Sexual reproduction has since been shown to be possible. Although the genus now mostly occurs in cool, isolated, high-altitude environments at temperate and tropical latitudes, the fossil record shows that it survived in climates that appear to be much warmer than those that Nothofagus now occupies.

Taxonomy

The genus Nothofagus was first formally described in 1850 by Carl Ludwig Blume who published the description in his book Museum botanicum Lugduno-Batavum, sive, Stirpium exoticarum novarum vel minus cognitarum ex vivis aut siccis brevis expositio et descriptio.
Four sub-genera are recognized, based on morphology and DNA analysis:
The following is a list of species, hybrids and varieties accepted by the Plants of the World Online as at April 2020:
In 2013, [Peter Brian Heenan and Rob D. Smissen proposed splitting the genus into four, turning the four recognized subgenera into the new genera Fuscospora, Lophozonia and Trisyngyne, with the five South American species of subgenus Nothofagus remaining in genus Nothofagus. The proposed new genera are not accepted at the World Checklist of Selected Plant Families.

Extinct species

The following additional species are listed as extinct:
The pattern of distribution around the southern Pacific Rim suggests the dissemination of the genus dates to the time when Antarctica, Australia, and South America were connected in a common land-mass or supercontinent referred to as Gondwana. However, genetic evidence using molecular dating methods has been used to argue that the species in New Zealand and New Caledonia evolved from species that arrived in these landmasses by dispersal across oceans. Uncertainty exists in molecular dates and controversy rages as to whether the distribution of Nothofagus derives from the break-up of Gondwana, or if long-distance dispersal has occurred across oceans. In South America, the northern limit of the genus can be construed as La Campana National Park and the Vizcachas Mountains in the central part of Chile.

Ecology

The species of subgenus Brassospora are evergreen, and distributed in the tropics of New Guinea, New Britain, and New Caledonia. In New Guinea and New Britain Nothofagus is characteristic of lower montane rain forests between 1000 and 2500 meters elevation, occurring infrequently at elevations as low as 600 meters and in upper montane forests between 2500 and 3150 meters elevation. Nothofagus is most commonly found above the Castanopsis-Lithocarpus zone in the lower montane forests, and below the conifer-dominated upper montane forests. Nothofagus grows in mixed stands with trees of other species or in pure stands, particularly on ridge crests and upper slopes. The Central Range has the greatest diversity of species, with fewer species distributed among the mountains of western and northern New Guinea, New Britain, and Goodenough and Normanby islands.
The New Caledonian species are endemic to the main island, most commonly on soils derived from ultramafic rocks between 150 to 1350 meters elevation. They occur in isolated stands, forming a low or stunted and irregular and fairly open canopy. The conifers Agathis and Araucaria are sometimes present as emergents, rising 10 to 20 meters above the Nothofagus canopy.

Beech mast

Every four to six years or so, Nothofagus produces a heavier crop of seeds and is known as the beech mast. In New Zealand, the beech mast causes an increase in the population of introduced mammals such as mice, rats, and stoats. When the rodent population collapses, the stoats begin to prey on native bird species, many of which are threatened with extinction. This phenomenon is covered in more detail in the article on stoats in New Zealand.