Rubus is a large and diverse genus of flowering plants in the rose family, Rosaceae, subfamily Rosoideae, most commonly known as brambles. Fruits of various species are known as raspberries, blackberries, dewberries, cloudberries, and bristleberries. It is a diverse genus, and estimates of the number of Rubus species vary from 250 to over 1,000, found across all continents except Antarctica. Most of these plants have woody stems with prickles like roses; spines, bristles, and gland-tipped hairs are also common in the genus. The Rubus fruit, sometimes called a bramble fruit, is an aggregate of drupelets. The term "cane fruit" or "cane berry" applies to any Rubus species or hybrid, which is commonly grown with supports such as wires or canes, including raspberries, blackberries, and hybrids such as loganberry, boysenberry, marionberry, and tayberry. The stems of such plants are also referred to as canes.
Description Bramble bushes typically grow as shrubs (though a few are herbaceous), with their stems being typically covered in sharp prickles. They grow long, arching shoots that readily root upon contact with soil, and form a soil rootstock from which new shoots grow in the spring. The leaves are either evergreen or deciduous, and simple, lobed, or compound. The shoots typically do not flower or set fruit until the second year of growth (i.e. they are biennial). The rootstock is perennial. Most species are hermaphrodites, with male and female parts being present on the same flower. Bramble fruits are aggregate fruits formed from smaller units called drupelets. Around 60–70% of species of Rubus are polyploid (having more than two copies of each chromosome), with species ranging in ploidy from diploid (2×, with 14 chromosomes) to tetradecaploid (14×).
Taxonomy
Modern classification Rubus is the only genus in the tribe Rubeae. Rubus is very complex, particularly within the blackberry/dewberry subgenus (Rubus), with polyploidy, hybridization, and facultative apomixis apparently all frequently occurring, making species classification of the great variation in the subgenus one of the grand challenges of systematic botany. In publications between 1910 and 1914, German botanist Wilhelm Olbers Focke attempted to organize the genus into 12 subgenera, a classification system that since became widely accepted, though modern genetic studies have found that many of these subgenera are not monophyletic. Some treatments have recognized dozens of species each for what other, comparably qualified botanists have considered single, more variable species. On the other hand, species in the other Rubus subgenera (such as the raspberries) are generally distinct or else involved in more routine one-or-a-few taxonomic debates, such as whether the European and American red raspberries are better treated as one species or two (in this case, the two-species view is followed here, with R. idaeus and R. strigosus both recognized; if these species are combined, then the older name R. idaeus has priority for the broader species). The classification presented below recognizes 13 subgenera within Rubus, with the largest subgenus (Rubus) in turn divided into 12 sections. Representative examples are presented, but many more species are not mentioned here. A comprehensive 2019 study found subgenera Orobatus and Anoplobatus to be monophyletic, while all other subgenera to be paraphyletic or polyphyletic. Molecular data have backed up classifications based on geography and chromosome number, but following morphological data, such as the structure of the leaves and stems, do not appear to produce a phylogenetic classification.
Fossil record The genus has a likely North American origin, with fossils known from the Eocene-aged Florissant Formation of Colorado, around 34 million years old. Rubus expanded into Eurasia, South America, and Oceania during the Miocene. Fossil seeds from the early Miocene of Rubus have been found in the Czech part of the Zittau Basin. Many fossil fruits of †Rubus laticostatus, †Rubus microspermus and †Rubus semirotundatus have been extracted from bore hole samples of the Middle Miocene freshwater deposits in Nowy Sacz Basin, West Carpathians, Poland.
Species
Rubus is a diverse genus, with estimates of the number of species varying from 250 to over 1,000, found across all continents except Antarctica. Better-known species include:
A more complete subdivision is as follows:
Hybrid berries The term "hybrid berry" is often used collectively for those fruits in the genus Rubus, which have been developed mainly in the U.S. and U.K. in the last 130 years. As Rubus species readily interbreed and are apomicts (able to set seed without fertilisation), the parentage of these plants is often highly complex, but is generally agreed to include cultivars of blackberries (R. ursinus, R. fruticosus) and raspberries (R. idaeus). The British National Collection of Rubus stands at over 200 species, and although not within the scope of the National Collection, also hold many cultivars. The hybrid berries include:-
loganberry (California, U.S., 1883) R. ×loganobaccus, a spontaneous hybrid between R. ursinus 'Aughinbaugh' and R. idaeus 'Red Antwerp' boysenberry (U.S., 1920s) - a hybrid between R. idaeus and R. × loganobaccus nectarberry - a suspected variant of boysenberry, a hybrid between R. idaeus and R. × loganobaccus olallieberry (U.S., 1930s) - a hybrid between the loganberry and youngberry, themselves both hybrid berries veitchberry (Europe, 1930s) - a hybrid between R. fruticosus and R. idaeus skellyberry (Texas, U.S., 2000s) - a hybrid between R. invisus and R. phoenicolasius marionberry (1956) - now thought to be a blackberry cultivar R. 'Marion' silvanberry - R. 'Silvan', a hybrid between R. 'Marion' and boysenberry tayberry (Dundee, Scotland, 1979) - another blackberry/raspberry hybrid tummelberry, R. 'Tummel' - from the same Scottish breeding programme as the tayberry hildaberry (1980s) - a tayberry/boysenberry hybrid discovered by an amateur grower youngberry - a complex hybrid of raspberries, blackberries, and dewberries
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