Lauraceae | |
---|---|
Litsea glutinosa with laurophyll or lauroide leaves. | |
Scientific classification | |
Kingdom: | Plantae |
(unranked): | Angiosperms |
(unranked): | Magnoliids |
Order: | Laurales |
Family: | Lauraceae Juss. |
Genera | |
Many; see text |
The Lauraceae or Laurel family comprises a group of flowering plants included in the order Laurales. The family includes about 55 genera with perhaps as many as 4000 species world-wide, mostly from warm or tropical regions, especially Southeast Asia and South America. Most are aromatic evergreen trees or shrubs, but one or two genera, including Sassafras are deciduous, and Cassytha is a genus of parasitic vines.
Contents |
Overview
The Lauraceae are the botanical family that includes the "True Laurel" and its closest relatives. They comprise a cosmopolitan family, but with most species occurring in the tropics. The Lauraceae are important components of tropical forests ranging from low-lying to montane. In several forested regions Lauraceae are among the top five families in terms of the number of species present.
Apart from their general presence in tropical forests, members of the Lauraceae form a characteristic and often dominant component of habitats known as Laurel forests. The Laurisilva of Macaronesia present a marked example, but, excepting only Antarctica, laurel forests of various types occur on all continents or on associated major islands.
Although the total number of species in the Lauraceae is uncertain, estimates suggest over 3000, and possibly 4000, species in 52 genera worldwide. Compared to other plant families, their taxonomy still is poorly understood. This is partly because of the great diversity of species, partly because of technical difficulties in identification, and partly because of inadequate investment in taxonomic effort. However, recent interest has advanced systematic knowledge of the family.
The Lauraceae are well represented in various types of forests. Because of the special lack of worldwide knowledge about the family in general, very little is known about their diversity. The knowledge of this family to national level, is that to be expected in countries with limited economic means with the vast majority of species indeterminate or even poorly determined. On the other hand, a high percentage of recently described new species come from collections made in these countries. Therefore an increase in the study of family, at national level, is of utmost importance for the progress of the systematics of the family in general.
Recent monographs of genera of lauraceae in small and medium genera, up to 100 species, have produced a high increase in the number of known species. This high increase in the number of species is expected for other genera, particularly for those with more than 150 species recorded, bringing an expected considerable increase in the total number of species of the family.[2]
Trees of the laurel family predominate in the world's laurel forests and cloud forest, which occur in tropical, subtropical and mild temperate regions of the northern and southern hemispheres, highlighting the Macaronesian islands, southern Japan, Madagascar, and central Chile. Trees usually evergreen, rarely parasitic climber plants as Cassytha genus.
There are three main economical uses for this family. A high content of essential oils are found in many Lauraceae that are important for spices and perfumes. Avocados are important oil-rich fruit that are now planted in warm climates across the world. The hard wood of many species is a source for timber around the world. A great number of species are in danger of extinction due to over exploitation as medicinal plants or timber extraction and also for loss of habitat.
The following genera include species with commercial value and are consequently among the best known: Cinnamomum: Cinnamon, Cassia and Camphor Laurel, Laurus: Bay Laurel, Lindera: Spicebush, Persea: Avocado, Sassafras: Sassafras.
Ecology
The leaves of some species have domatias in the axils of the nerves, inhabited by mites. Other species, as some in genus Pleurothyrium, live in symbiosis with ants that protect and defend the tree. Other defense mechanism that protect and defend are the bad-taste and bad-smelling, sometimes toxic, corrosive, or poisonous, of wood, flowers, leaves, sap etc. The flowers are protogynous, often with a complex flowering system to prevent inbreeding. The fruits are an important food source for birds, as some palaeognathae highly dependent on this food. Usually the birds are from specialized genera: Cotingidae, Columbidae, Trogonidae, Turdidae, Rhamphastidae, etc. Birds eat the whole fruit and regurgitate seeds intact, expanding the seeds in the best conditions for germination (ornitochory). Secondly, the seed dispersal is carried out by monkeys, chipmunks, porcupines, opossums and fishes. We know the hydrochory in Caryodaphnopsis.
The family is distributed throughout tropical, subtropical areas, and cloud forest and a large part of species requires a high degree of moisture in the air. Lauraceae has several relict species living in temperate areas of both hemispheres. The main centers of diversity are found in the region Indomalaya and Central America and South America, with Africa having a smaller number of species than other ecologically equivalent areas. The family has its origin in the coastal laurel forests of Gondwana, which explains its distribución. Lauraceae inhabit montane tropical forests, reaching some species 4000 m, but are even more frequent in low-altitude rainforests. Some species have adapted to extreme conditions in semi-arid climates but mostly depending on favorable soil edaphic conditions, as presence of aquifers, groundwater periodic flows, periodically flooded forests in sand almost without nutrients. They are found in various species pneumatophores that are a type of root that grows upward, present in plants associated with water bodies. The pneumatophores favor the oxygenation of the plant parts that are submerged under water. Gondwanan plants related to lauraceae by belong to the same habitat or in addition to the same order laurales, for example, the single species, Amborella trichopoda that is the only member of both Amborella genus in the family Amborellaceae within the Amborellales formerly in laurales, from Gondwana in New Caledonia, have become very difficult to establish the relationships between species.
It has been suggested an age of onset of the family of 174 + / - 32 Ma, while some authors (seeLi et al.2004, references) do not believe the origin has to look beyond the Cretaceous medium. Known fossils flowers are attributed to this family in clays of Cenomanian (mid-Cretaceous, 90-98 Ma ago) of the United States Eastern (mirabilis Mauldinia). The family is common in the tertiary strata of Europe and North America, but virtually disappeared from central Europe in the Late Miocene. Because of their extraordinary fragility, Lauraceae pollen does not keep well and is known only in relatively recent strata.
The patterns of speciation in the Lauraceae indicate that since the onset of aridification on the continents 15 million years ago, rainforest diversified in species numbers with the majority of contemporary species the product of vicariance. One of the products of aridification is the current island like archipelagos of rainforests along the planet. The fragmentation of once more continuous rainforest facilitated isolation of populations and this likely caused the increase in the rate of speciation as found in the Lauraceae. While many of the young species show a very disjunct distribution with sister taxa occurring in other centres of rainforest and cloud forest diversity, indicating that this group is most likely of Gondwanan origin, others groups of lauraceae responded to favourable climatic periods and expanded across the available habitat, occur as opportunistic species across wide distribution with close relatives and few species, indicating the recent divergence of this species. Many of extant laurel species of this other groups are relatively young.
In the case of divergent evolution within lauraceae, this similarity, of course, is due to the common origin. In contrast, the convergent evolution is due to ecological or physical drivers toward a similar solution, including analogous structures. Many botanical species are having similar foliage to the Lauraceae due to convergent evolution. Plants of the laurel forests must adapt to high rainfall and humidity. The trees adapted by developing leaves that repel water. Laurophyll or lauroide leaves are characterized by a generous layer of wax, making them glossy in appearance, and narrow, pointed oval in shape with an apical mucro, or 'drip tip', which permit the leaves to shed water despite the humidity, allowing perspiration and respiration from plant. The scientific names Daphnidium, Daphniphyllum, Daphnopsis, Daphnandra, Daphne'[3] from Greek: Δάφνη, meaning "laurel", Laureliopsis, laureola, laurelin, Laurelindorinan, laurifolia, lauriformis, laurina, laurophylla, laurocerasus, and lauroide are often used to name species of other plant families that resemble Lauraceace.[4] Furthermore, it is common that the dispersal of seeds in many laurel forest species is due to birds that swallow them, so also the fruit and berries are often similar to attract birds. Although not closely related to Lauraceae family despite the similarity, Laurelia genus, in the family Atherospermataceae is equivalent to this of Lauraceae in southern hemisphere.
Deciduous lauraceae lose all of their leaves for part of the year depending on variations in rainfall. The leaf loss coincides with the dry season in tropical, subtropical and arid regions. In temperate or polar climates the dry season is due to the inability of the plant to absorb water available by to be in the form of ice.
The lauracea are usually trees, but the genus Cassytha are parasitic climber herbs with at least seventeen to twenty species of climber plants from most of Australia, but with species originating in Africa, the southern Asia, north of South America, Central America, southern the Florida, Japan and one (Cassytha filiformis) of Hawaii. This genus is universally recognized as monophyletic within Lauraceae. This postion within Lauraceae is supported by floral morphology and molecular data. It is a phenomenon of divergent evolution from the large evergreen trees, for occupy another ecological niche. Also it is a phenomenon of convergent evolution with climbing species as cuscuta or Laurel forest habitat climbing species as lauroide Ivy genus, spread by birds that helped to colonize large areas again.
Classification
Lauraceae have always been considered a primeval group of Flowering plants. The APW (Angiosperm Phylogeny Website) considered it part of the advanced group of Order Laurales, being the most advanced family and the sister group of the Hernandiaceae (cf. AP-website).
The systematic internal in the family still raises many unresolved problems, p. eg., the division into genus is based on characters that can vary even within the same flower (teak 2 - or 4-sporangium, placing them, etc..), so are not reliable. In most phylogenetic analysis, hypodaphnis appears as the basal branch, sister group of the rest of the family. There is no overlap in the different analysis of whether Cassytha or the group of genera close to Cryptocarya and Beilschmiedia would be the next branch of phylogenetic tree. The couple Caryodaphnopsis + Neocinnamomum form the next branch, which is the sister group of the core of the Lauraceae. This nucleus, which seems to very short phylogenetic distances, would compound (branching order) by:
a) The group consisting of Chlorocardium and sub-genres called Mezilaurus.
b) The subset of Persea.
c) A poorly defined group which would include gender Lindera, Litsea, Neolitsea, Sassafras and perhaps Actinodaphne, part of the tribe Laureae in the classical sense.
d) A terminal group formed the subgroups advanced of Ocotea, of Aniba and the rest of the tribe Laureae, among which highlight the fact that neither gender Ocotea, or Nectandra and Cinnamomum would be monophyletic (as suspected already), and that there would be no real difference between the genus Aniba, Dicypellium and Urbanodendron. The genus Actinodaphne, Litsea, Neolitsea and Lindera would be not monophyletic (Li et al. 2004, see references).
Classification within the Lauraceae remains unresolved. Multiple classification schemes based on a variety of morphological and anatomical characteristics have been proposed but none are fully accepted. According to Judd et al. (2007),[5] the suprageneric classification proposed by van der Werff and Richter (1996)[6] is currently the authority. However, due to an array of molecular and embryological evidence that disagrees with the groupings, it is not fully accepted by the scientific community. Their classification is based on both inflorescence structure and wood and bark anatomy. It divides Lauraceae into two subfamilies, Cassythoideae and Lauroideae. The Cassythoideae comprises a single genus, Cassytha, and is defined by its herbaceous, parasitic habit. The Lauroidaeae is then divided into three tribes: Laureae, Perseeae, and Cryptocaryeae.
The subfamily, Cassythoideae, is not fully supported. Backing has come from matK sequences of chloroplast genes [7] while a questionable placement of Cassytha has been concluded from analysis of intergenetic spacers of chloroplast and nuclear genomes.[8] Embryological studies also appear contradictory. One study by Heo et al. (1998)[9] supports the subfamily. It found that Cassytha develops an ab initio cellular type endosperm and rest of the family (with one exception) develops a nuclear type endosperm. Kimoto et al. (2006) [10] suggests that Cassytha should be placed in the Cryptocaryeae tribe because it shares a glandular anther tapetum and an embryo sac protruding from the nucellus with other members of the Cryptocaryeae.
The Laureae and Perseeae tribes are not well supported by any molecular or embryological studies. Sequences of the matK chloroplast gene [7] as well as sequences of chloroplast and nuclear genomes[8] reveal close relationships between the two tribes. Embryological evidence does not support a clear division between the two tribes either. Genera such as Caryodaphnopsis and Aspidostemon that share embryological characteristics with one tribe and wood and bark characteristics or inflorescence characteristics with another tribe blur the division of the these groups.[9] All available evidence, except for inflorescence morphology and wood and bark anatomy, fails to support separate Laureae and Perseeae tribes.
The Cryptocaryeae tribe is partially supported by molecular and embryological studies. Chloroplast and nuclear genomes supports a tribal grouping that contains all the genera circumscribed by van der Weff and Richter (1996)[6] as well as three additional genera.[8] Partial support for the tribe is also attained from the matK sequences of chloroplast genes [7] as well as embryology.[11]
Challenges in Lauraceae classification
The knowledge of all individuals comprising the Lauraceae is incomplete. As of 1991, approximately 25-30% of neotropical Lauraceae species had not been described.[12] As of 2001, embryological studies had only been completed on individuals from 26 genera yielding a 38.9% level of knowledge, in terms of embryology, for this family.[11] Additionally, the huge amount of variation within the family for any potential defining characteristic poses a major challenge for developing a reliable classification.[6][12] It is impossible to describe even one genus or tribe by a single well-defined character.[12] For this reason, all proposed classifications rely on a set of characteristics where the combination presents the most frequently observed traits for the group.[6][12]
Phytochemistry
The adaptation to new environments has been lauraceae following a long journey of evolution that has led many specializations including defensive or deterrent systems against other living beings
There is no standard common name for lauraceae as a whole. Common names of some species refer to their similarity to other Lauraceae such as laurel or sassafras. Many terms are used instead that refer to wood's aromatic, sometimes even nauseatingly pungent smell. Laurel is the better known term applied by the scent given off by many species that are not even in the family of the Lauraceae. Sweetwood is common in the genus Ocotea, it is hardly ever used for other plants.[13] Camphorwood is usually used for Cinnamomum camphora, a close relative of Ocotea and other tree species that scent given off. Stinkwood can refer to any number of quite unrelated trees with bad-smelling wood, as Oreodaphne bullata, of disagreeable odor found at the cape of Good Hope. Ocotea foetens in macaronesian islands, etc.
Alkaloids bencilisoquinolidinics are present, mainly aporphinans, oxoaporphinans and morphinans, as well as derivatives of Pavina. Essential oils widely distributed, especially terpenoids, benzyl benzoates, alilfenols and propenilfenols. Lignans and neolignans present, and flavonoids s-methyl 5-O, proanthocyanidins, cinamoilamidas, fenilpironas, estirilpironas, polyketides (acetogeninss), furanosesquiterpens and sesquiterpene lactones:germanacrolidous, elemanolidous, eudesmanolidous and guayanolidous.
Genera
The list of genus includes some genera of dubious validity, but the state of current knowledge of the systematics of the family not allows for greater accuracy. They have been compiled from recent work.[14][15] [16]: Some genus were before sometimes included as a subgenus.
References
- ^ US Fish and Wildlife Service: Species Recovery Plan: Lindera melissifolia.
- ^ http://botanica.uniandes.edu.co/investigacion/lauraceae.htm
- ^ Sunset Western Garden Book, 1995:606–607
- ^ Otto E. (Otto Emery) Jennings. "Fossil plants from the beds of volcanic ash near Missoula, western Montana" Memoirs of the Carnegie Museum, Volume 8, Number 2. p. 417. [1]
- ^ Judd, Walter, S.; Christopher Campbell, Elizabeth Kellog, Peter Stevens, and Michael Donoghue (2007). Plant Systematics a Phylogenetic Approach, third edition. Massachusetts, USA: Sinauer Associates, Inc.. ISBN 978-0-87893-407-2.
- ^ a b c d H van der Werff and J.G. Richter (1996). "Toward an improved classification of Lauraceae". Annals of the Missouri Botanical Garden (Annals of the Missouri Botanical Garden, Vol. 83, No. 3) 83 (3): 409–418. doi:10.2307/2399870. JSTOR 2399870.
- ^ a b c Rohwer, J.G. (2000). "Toward a phylogenetic classification of the Lauraceae: evidence from matK sequences". Systematic Botany (Systematic Botany, Vol. 25, No. 1) 25 (1): 60–71. doi:10.2307/2666673. JSTOR 2666673.
- ^ a b c Chanderbali, A.S.,van der Werff,H. and Renner, S.S. (2001). "Phylogeny and historical biogeography of Lauraceae: Evidence from the chloroplast and nuclear genomes". Annals of the Missouri Botanical Garden (Annals of the Missouri Botanical Garden, Vol. 88, No. 1) 88 (1): 104–134. doi:10.2307/2666133. JSTOR 2666133.
- ^ a b Heo,K.,van der Werff, H., and Tobe, H. (1998). "Embryology and relationships of Lauraceae(Laurales)". Botanical Journal of the Linnean Society 126 (4): 295–322. doi:10.1006/bojl.1997.0138.
- ^ Kimoto,Y.,Utame N., and Tobe, H. (2006). "Embryology of Eusideroxylon (Cryptocaryeae, Lauraceae) and character evolution in the family". Botanical Journal of the Linnean Society 150 (2): 187–201. doi:10.1111/j.1095-8339.2006.00458.x.
- ^ a b Kimoto,Y.,and H. Tobe (2001). "Embryology of Laurales: a review and perspectives". Journal of Plant Research 114 (3): 247–261. doi:10.1007/PL00013988.
- ^ a b c d Rohwer, J. G.,H. Richter, and H. van der Werff (1991). "Two new genera of neotropical Lauraceae and critical remarks on the generic delimitation". Annals of the Missouri Botanical Garden (Annals of the Missouri Botanical Garden, Vol. 78, No. 2) 78 (2): 388–4oo. doi:10.2307/2399568. JSTOR 2399568.
- ^ USDA (2008b)
- ^ http://www.plantsystematics.org/taxpage/0/binomial/Laurus_dioica
- ^ http://lauraceae.myspecies.info/category/lauraceae/lauraceae
- ^ http://www.tropicos.org/Name/42000016
- Lauraceae in L. Watson and M.J. Dallwitz (1992 onwards). The families of flowering plants.
- Kostermans, André Joseph Guillaume Henri 1957. Lauraceae. Reinwardtia 4(2): 193-256
- Meissner (né Meisner), Carl Daniel Friedrich 1864. Lauraceae (Ordo 162) in A. L. P. P. de Candolle (ed.), Prodromus Systematis Universalis Regni Vegetabilis 15(1): 1-260, Parisiis [Paris], Victoris Masson et Filii.
- Mez, Carl Christian 1889. Lauraceae Americanae Monographice Descripsit. Jahrbuch des Königlichen Botanischen Gartens und des Botanischen Museums zu Berlin 5: 1-556.
- Nees von Esenbeck, Christian Gottfried Daniel (1836): Systema Laurinarum, Berlin, Veitii et Sociorum. Until the page 352, available, free, on pdf files in Gallica
- Rohwer, Jens G. in Kubitzki, K.(Editor) 1993. The Families and Genera of Vascular Plants, Vol.2: K. Kubitzki, J. G. Rohwer & V. Bittrich, 366-390. ISBN 3-540-55509-9
- Wagner, W. L., D. R. Herbst, and S. H. Sohmer. 1990. Manual of the Flowering Plants of Hawai'i. Spec. Publ. 83. University of Hawaii Press and Bishop Museum Press. Bishop Museum. 1854 pp.
- 1. Judd, Walter, S.; Christopher Campbell, Elizabeth Kellog, Peter Stevens, and Michael Donoghue (2007). Plant Systematics a Phylogenetic Approach, third edition. Massachusetts, USA: Sinauer Associates, Inc.. ISBN 978-0-87893-407-2.
- 2. H. van der Werff and H. Richter (1996). "Toward an improved classification of Lauraceae". Annals of the Missouri Botanical Garden (Annals of the Missouri Botanical Garden, Vol. 83, No. 3) 83 (3): 409–418. doi:10.2307/2399870. JSTOR 2399870.
- 3. J. G. Rohwer, (2000). "Toward a phylogenetic classification of the Lauraceae: evidence from matK sequences". Systematic Botany (Systematic Botany, Vol. 25, No. 1) 25 (1): 60–71. doi:10.2307/2666673. JSTOR 2666673.
- 4. A.S., Chanderbali, H. van der Werff, and S.S. Renner (2001). "Phylogeny and historical biogeography of Lauraceae: Evidence from the chloroplast and nuclear genomes". Annals of the Missouri Botanical Garden (Annals of the Missouri Botanical Garden, Vol. 88, No. 1) 88 (1): 104–134. doi:10.2307/2666133. JSTOR 2666133.
- 5. K. Heo,H. van der Werff, and H. Tobe (1998). "Embryology and relationships of Lauraceae(Laurales)". Botanical Journal of the Linnean Society 126 (4): 295–322. doi:10.1006/bojl.1997.0138.
- 6. Y. Kimoto, N. Utame, and H. Tobe (2006). "Embryology of Eusideroxylon (Cryptocaryeae, Lauraceae) and character evolution in the family". Botanical Journal of the Linnean Society 150 (2): 187–201. doi:10.1111/j.1095-8339.2006.00458.x.
- 7. Y. Kimoto and H. Tobe (2001). "Embryology of Laurales: a review and perspectives". Journal of Plant Research 114 (3): 247–261. doi:10.1007/PL00013988.
- 8. J. G. Rohwer, H. Richter, and H. van der Werff (1991). "Two new genera of neotropical Lauraceae and critical remarks on the generic delimitation". Annals of the Missouri Botanical Garden (Annals of the Missouri Botanical Garden, Vol. 78, No. 2) 78 (2): 388–400. doi:10.2307/2399568. JSTOR 2399568.