Race (biology)

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Four different ecotypes, i.e. ecological races, of the species Physcomitrella patens, stored at the International Moss Stock Center Ecotypes of Physcomitrella patens.JPG
Four different ecotypes, i.e. ecological races, of the species Physcomitrella patens , stored at the International Moss Stock Center

In biological taxonomy, race is an informal rank in the taxonomic hierarchy for which various definitions exist. Sometimes it is used to denote a level below that of subspecies, while at other times it is used as a synonym for subspecies. [1] It has been used as a higher rank than strain, with several strains making up one race. [2] [3] Races may be genetically distinct populations of individuals within the same species, [4] or they may be defined in other ways, e.g. geographically, or physiologically. [5] Genetic isolation between races is not complete, but genetic differences may have accumulated that are not (yet) sufficient to separate species. [6]

Contents

The term is recognized by some, but not governed by any of the formal codes of biological nomenclature. Taxonomic units below the level of subspecies are not typically applied to animals. [7]

Other terms

In botany, the Latin words stirps and proles were traditionally used, and proles was recommended in the first botanical Code of Nomenclature, published in 1868. [8]

Definitional approaches

Races are defined according to any identifiable characteristic, including gene frequencies. [9] "Race differences are relative, not absolute." [9] Adaptive differences that distinguish races can accumulate even with substantial gene flow and clinal (rather than discrete) habitat variation. [10] Hybrid zones between races are semi-permeable barriers to gene flow, [11] see for example the chromosome races of the Auckland tree wētā. [12] {{

; while the name of a race is added after the binomial scientific name (and may be arbitrary, e.g. an alphanumeric code, usually with the word "race"): " Podosphaera xanthii race S". [13]

A physiological race is not to be confused with a physiologic race, an obsolete term for cryptic species. [14] Neither biological form nor forma specialis should be confused with the formal botanical taxonomic rank of forma or form, or with the zoological term form, an informal description (often seasonal) which is not taxonomic.

The term race has also historically been used in relation to domesticated animals, as another term for breed ; [4] this usage survives in combining form, in the term landrace, also applied to domesticated plants. The cognate words for race in many languages (Spanish: raza; German: Rasse; French: race) may convey meanings the English word does not, and are frequently used in the sense of 'domestic breed'. [15]

Distinguishing from other taxonomic ranks

If the races are sufficiently different or if they have been tested to show little genetic connection regardless of phenotype, two or more groups/races can be identified as subspecies or (in botany, mycology, and phycology) another infraspecific rank, and given a name. Ernst Mayr wrote that a subspecies can be "a geographic race that is sufficiently different taxonomically to be worthy of a separate name." [16] [17]

Study of populations preliminarily labelled races may sometimes lead to classification of a new species. For example, in 2008, two populations of the brown planthopper (Nilaparvata lugens) in the Philippines, one adapted to feeding on rice, and another on Leersia hexandra grass, were reclassified from races into "two distinct, but very closely allied, sympatric species", based on poor survival rate when given the opposite food source, barriers to hybridization between the populations, uniform preference for mating between members of the same population, differences in mating sounds, oviposition variances, and other distinguishable characteristics. [18]

For pathogenic bacteria adapted to particular hosts, races can be formally named as pathovars. For parasitic organisms governed by the International Code of Nomenclature for algae, fungi, and plants , the term forma specialis (plural formae speciales) is used.

In mycology and phytopathology

Classification of fungal microbes into races is done frequently in mycology, the study of fungi, and especially in phytopathology, the study of plant diseases, which are often fungal. The term "physiologic race" was recommended for use over "biologic form" at the International Botanical Congress of 1935. Although historically the term has been used inconsistently by plant pathologists, the modern trend is to use race to refer to "groups of host genotypes permitting characterization of virulence" [19] (in simpler terms: grouping the parasitic fungi into races based on how strongly they affect particular host plants).

Commercial Cucumis melo (cantaloupe and muskmelon) production, for example, has been engaged in a biological "arms race", since 1925, against cucurbit powdery mildew, caused by successively arising races of Podosphaera xanthii fungus, with new cultivars of melons being developed for resistance to these pathogens. [13] [20]

A 2004 literature review of this issue concluded that "race identification is important for basic research and is especially important for the commercial seed industry", but was seen as having little utility in horticulture for choosing specific cultivars, because of the rapidity with which the local pathogen population can change geographically, seasonally, and by host plant. [13]

Classification of fungal races can be difficult because host plants' responses to particular populations of fungi can be affected by humidity, light, temperature, and other environmental factors; different host plants may not all respond to particular fungal populations or vice versa; and identification of genetic differences between populations thought to form distinct fungal races can be elusive. [13]

See also

Related Research Articles

<span class="mw-page-title-main">Ascomycota</span> Division or phylum of fungi

Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The defining feature of this fungal group is the "ascus", a microscopic sexual structure in which nonmotile spores, called ascospores, are formed. However, some species of Ascomycota are asexual and thus do not form asci or ascospores. Familiar examples of sac fungi include morels, truffles, brewers' and bakers' yeast, dead man's fingers, and cup fungi. The fungal symbionts in the majority of lichens such as Cladonia belong to the Ascomycota.

<span class="mw-page-title-main">Subspecies</span> Taxonomic rank subordinate to species

In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species have subspecies, but for those that do there must be at least two. Subspecies is abbreviated as subsp. or ssp. and the singular and plural forms are the same.

<span class="mw-page-title-main">Powdery mildew</span> Fungal plant disease

Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of ascomycete fungi in the order Erysiphales. Powdery mildew is one of the easier plant diseases to identify, as the signs of the causal pathogen are quite distinctive. Infected plants display white powdery spots on the leaves and stems. This mycelial layer may quickly spread to cover all of the leaves. The lower leaves are the most affected, but the mildew can appear on any above-ground part of the plant. As the disease progresses, the spots get larger and denser as large numbers of asexual spores are formed, and the mildew may spread up and down the length of the plant.

A Biopesticide is a biological substance or organism that damages, kills, or repels organisms seens as pests. Biological pest management intervention involves predatory, parasitic, or chemical relationships.

<span class="mw-page-title-main">Species complex</span> Group of closely related similar organisms

In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each other, further blurring any distinctions. Terms that are sometimes used synonymously but have more precise meanings are cryptic species for two or more species hidden under one species name, sibling species for two species that are each other's closest relative, and species flock for a group of closely related species that live in the same habitat. As informal taxonomic ranks, species group, species aggregate, macrospecies, and superspecies are also in use.

<i>Forma specialis</i> Informal taxonomic group

Forma specialis, abbreviated f. sp. without italics, is an informal taxonomic grouping allowed by the International Code of Nomenclature for algae, fungi, and plants, that is applied to a parasite which is adapted to a specific host. This classification may be applied by authors who do not feel that a subspecies or variety name is appropriate, and it is therefore not necessary to specify morphological differences that distinguish this form. The literal meaning of the term is 'special form', but this grouping does not correspond to the more formal botanical use of the taxonomic rank of forma or form.

<span class="mw-page-title-main">Erysiphales</span> Order of fungi

Erysiphales are an order of ascomycete fungi. The order contains one family, Erysiphaceae. Many of them cause plant diseases called powdery mildew.

<i>Blumeria graminis</i> Fungal pathogen of grasses

Blumeria graminis is a fungus that causes powdery mildew on grasses, including cereals. It is the only species in the genus Blumeria. It has also been called Erysiphe graminis and Oidium monilioides or Oidium tritici.

<i>Podosphaera leucotricha</i> Species of fungus

Podosphaera leucotricha is a plant pathogen that can cause powdery mildew of apples and pears.

<i>Podosphaera macularis</i> Species of fungus

Podosphaera macularis is a plant pathogen infecting several hosts including chamomile, caneberrie, strawberries, hop, hemp and Cineraria. It causes powdery mildew of hops.

<i>Podosphaera pannosa</i> Species of fungus

Podosphaera pannosa is a plant pathogen. It produces a powdery mildew on members of the rose family.

<i>Podosphaera fuliginea</i> Species of fungus

Podosphaera fuliginea is a plant pathogen that causes powdery mildew on cucurbits. Podosphaera fuliginea and Erysiphe cichoracearum are the two most commonly recorded fungi causing cucurbit powdery mildew. In the past, Erysiphe cichoracearum was considered to be the primary causal organism throughout most of the world. Today, Podosphaera fuliginea is more commonly reported.

<i>Podosphaera fusca</i> Species of fungus

Podosphaera fusca is a fungus that parasitically infects plants. It is one cause of powdery mildew in melons and gourds.

<i>Uncinula</i> Genus of fungi

Uncinula is a genus of fungi. Its species are plant pathogens that cause powdery mildew diseases on various plant hosts. The genus is characterized by its dark chasmothecia which bear filamentous, hyaline appendages with hooked tips. Over one hundred species have been described from mostly dicotyledenous hosts. Braun and Takamatsu (2000) suggested that Uncinula should be considered a later synonym of Erysiphe; not all subsequent researchers have accepted their conclusions.

<i>Melothria scabra</i> Species of flowering plant

Melothria scabra, commonly known as the cucamelon, Mexican miniature watermelon, Mexican sour cucumber, Mexican sour gherkin, mouse melon, or pepquinos, is a species of flowering plant in the cucurbit family grown for its edible fruit. Its native range spans Mexico to Venezuela. Fruits are about the size of grapes and taste like cucumbers with a tinge of sourness. It may have been eaten by indigenous peoples before the European colonization of the Americas began.

<i>Podosphaera</i> Genus of fungi

Podosphaera is a genus of fungi in the family Erysiphaceae. Species in this genus are plant pathogens, causing powdery mildew.

<i>Ampelomyces quisqualis</i> Species of fungus

Ampelomyces quisqualis is an anamorphic fungus that is a hyperparasite of powdery mildews. This parasitism reduces growth and may eventually kill the mildew. These mycoparasites can live up to 21 days on mildew-free host plant surfaces, attacking powdery mildew structures as soon as they appear. A. quisqualis is used as the active ingredient in a commercial fungicide.

<span class="mw-page-title-main">Ectomycorrhiza</span> Non-penetrative symbiotic association between a fungus and the roots of a vascular plant

An ectomycorrhiza is a form of symbiotic relationship that occurs between a fungal symbiont, or mycobiont, and the roots of various plant species. The mycobiont is often from the phyla Basidiomycota and Ascomycota, and more rarely from the Zygomycota. Ectomycorrhizas form on the roots of around 2% of plant species, usually woody plants, including species from the birch, dipterocarp, myrtle, beech, willow, pine and rose families. Research on ectomycorrhizas is increasingly important in areas such as ecosystem management and restoration, forestry and agriculture.

<i>Podosphaera filipendulae</i> Species of fungus

Podosphaera filipendulae is a fungal species that belongs to the genus Podosphaera and the order Erysiphaceae. It was first described with meadowsweet as the host plant.

<i>Golovinomyces orontii</i> Species of fungus

Golovinomyces orontii is a species of fungus that causes powdery mildew disease and it is in the family Erysiphaceae. It is an obligate biotroph that infects plants in several families including Acanthaceae, Asteraceae, Brassicaceae, Cucurbitaceae, and Lamiaceae.

References

  1. ↑ Keita, S. O. Y.; Kittles, R. A.; Royal, C. D. M.; Bonney, G. E.; Furbert-Harris, P.; Dunston, G. M.; Rotimi, C. N. (2004). "Conceptualizing human variation". Nature Genetics. 36 (11s): S17–S20. doi: 10.1038/ng1455 . PMID   15507998. Modern human biological variation is not structured into phylogenetic subspecies ('races'), nor are the taxa of the standard anthropological 'racial' classifications breeding populations
  2. ↑ Gotoh, T.; Bruin, J.; Sabelis, M. W.; Menken, S. B. J. (1993). "Host race formation in Tetranychus urticae: Genetic differentiation, host plant preference, and mate choice in a tomato and a cucumber strain" (PDF). Entomologia Experimentalis et Applicata (Submitted manuscript). 68 (2): 171–178. Bibcode:1993EEApp..68..171G. doi:10.1111/j.1570-7458.1993.tb01700.x. S2CID   86180826.
  3. ↑ Ritchie, D. F.; Dittapongpitch, V. (1991), "Copper- and streptomycin-resistant strains and host differentiated races of Xanthomonas campestris pv. vesicatoria in North Carolina" (PDF), Plant Disease, 75 (7): 733–736, doi:10.1094/pd-75-0733
  4. 1 2 Walker, Peter M. B., ed. (2004) [1999]. "Race". Chambers Dictionary of Science and Technology. Edinburgh / New Delhi: Chambers Harrap / Allied Chambers. Republished without known revision several times since 1999, and originally published as: The Wordsworth Dictionary of Science and Technology. W. R. Chambers Ltd / Cambridge University Press. 1988.
  5. ↑ Morris, Christopher, ed. (1992). "Race". Academic Press Dictionary of Science and Technology . San Diego / London: Academic Press (Harcourt Brace Jovanovich). "Biology" entry, p. 1777. ISBN   9780122004001. an interbreeding subgroup of a species whose individuals are geographically, physiologically, or chromosomally distinct from other members of the species
  6. ↑ Jaenike, J. (1981), "Criteria for Ascertaining the Existence of Host Races", The American Naturalist, 117 (5): 830–834, doi:10.1086/283771, JSTOR   2460772, S2CID   84136840
  7. ↑ Haig, S. M.; Beever, E. A.; Chambers, S. M.; Draheim, H. M.; Dugger, B. D. (December 2006). "Taxonomic considerations in listing subspecies under the U.S. Endangered Species Act". Conservation Biology. 20 (6): 1584–1594. Bibcode:2006ConBi..20.1584H. doi:10.1111/j.1523-1739.2006.00530.x. PMID   17181793. S2CID   9745612.
  8. ↑ de Candolle, A. (1868), Laws of Botanical Nomenclature adopted by the International Botanical Congress held at Paris in August 1867; together with an Historical Introduction and Commentary by Alphonse de Candolle, Translated from the French, London: L. Reeve and Co., "Article 14" p. 20-21, and "Commentary" p. 42
  9. 1 2 Rieger, R.; Michaelis, A.; Green, M. M. (1968). A glossary of genetics and cytogenetics: Classical and molecular . New York: Springer-Verlag. ISBN   9780387076683.
  10. ↑ Van Buskirk, J. (2014). "Incipient habitat race formation in an amphibian". Journal of Evolutionary Biology. 27 (3): 585–592. doi:10.1111/jeb.12327. PMID   26230250.
  11. ↑ Barton, N. H.; Hewitt, G. M. (1 November 1985). "Analysis of Hybrid Zones". Annual Review of Ecology and Systematics. 16 (1): 113–148. doi:10.1146/annurev.es.16.110185.000553. ISSN   0066-4162.
  12. ↑ Morgan-Richards, Mary; Wallis, Graham P. (2003). "A Comparison of Five Hybrid Zones of the Weta Hemideina Thoracica (orthoptera: Anostostomatidae): Degree of Cytogenetic Differentiation Fails to Predict Zone Width". Evolution. 57 (4): 849–861. doi:10.1111/j.0014-3820.2003.tb00296.x. ISSN   1558-5646. PMID   12778554. S2CID   34384565.
  13. 1 2 3 4 Cohen, R.; Burger, Y.; Katzir, N. (2004). "Monitoring Physiological races of Podosphaera xanthii (syn. Sphaerotheca fuliginea), the Causal Agent of Powdery Mildew in Curcubits: Factors Affecting Race Identification and the Importance for Research and Commerce". Phythoparasitica. 32 (2): 174–183. Bibcode:2004Phyto..32..174C. doi:10.1007/bf02979784. S2CID   27174422.
  14. ↑ Morris, Christopher, ed. (1992). "Physiological race" and "Physiologic race". Academic Press Dictionary of Science and Technology . San Diego / London: Academic Press. p.  1643. ISBN   9780122004001.
  15. ↑ See any comprehensive multilingual dictionaries, e.g The Velázquez Spanish and English Dictionary.
  16. ↑ Mayr, Ernst (1970). Populations, Species, and Evolution. Cambridge, Massachusetts: Belknap / Harvard University Press. ISBN   9780674690134. An abridgment and revision of Animal Species and Evolution (1963).
  17. ↑ Mayr, Ernst (Winter 2002). "The Biology of Race and the Concept of Equality". Daedalus . 131 (1): 89–94. JSTOR   20027740.
  18. ↑ Claridge, M. F.; Den Hollander, J.; Morgan, J. C. (May 1985). "The status of weed-associated populations of the brown planthopper, Nilaparvata lugens (Stål) – host race or biological species?". Zoological Journal of the Linnean Society. 84 (1): 77–90. doi:10.1111/j.1096-3642.1985.tb01717.x.
  19. ↑ Kirk, P. M.; Cannon, P. F.; Minter, D. W.; Stalpers, J. A. (2008). Dictionary of the Fungi (10th ed.). Wallingford, Oxfordshire: CAB International. p. 534. ISBN   9780851998268.
  20. ↑ McCreight, James D.; Coffey, Michael D. (June 2011). "Inheritance of Resistance in Melon PI 313970 to Cucurbit Powdery Mildew Incited by Podosphaera xanthii Race S". HortScience. 46 (6): 838–840. doi:10.21273/HORTSCI.46.6.838.
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