Laurus
Encyclopedia
- This article is about the Laurus genus. For information on the church hierarch, see Metropolitan LaurusMetropolitan LaurusMetropolitan Laurus of New York was First Hierarch of the Russian Orthodox Church Outside Russia, the fifth cleric to hold that position...
. For the saint, see Florus and LaurusFlorus and LaurusSaints Florus and Laurus are venerated as Christian martyrs of the 2nd century. According to a Greek tale, they were twin brothers who worked as stonemasons...
.
Overview
Laurus is a genus of evergreenEvergreen
In botany, an evergreen plant is a plant that has leaves in all seasons. This contrasts with deciduous plants, which completely lose their foliage during the winter or dry season.There are many different kinds of evergreen plants, both trees and shrubs...
tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
s belonging to the Laurel family, Lauraceae
Lauraceae
The Lauraceae or Laurel family comprises a group of flowering plants included in the order Laurales. The family contains about 55 genera and over 3500, perhaps as many as 4000, species world-wide, mostly from warm or tropical regions, especially Southeast Asia and South America...
. The genus includes three species, whose diagnostic key characters often overlap (Mabberley 1997).
- Laurus azoricaLaurus azoricaLaurus azorica is a species of plant in the Lauraceae family, related to laurus nobilis. It is a member of the genus Laurus and is commonly known as Azores Laurel. Laurus is a genus of evergreen trees belonging to the Laurel family, Lauraceae...
(Seub.) Franco, Known as Azores Laurel, or by the Portuguese names Louro, Loureiro, Louro-da-terra, and Louro-de-cheiro, is native to the laurisilvaLaurisilvaLaurisilva or laurissilva is a subtropical forest, found in areas with high humidity and relatively stable and mild temperatures. They are characterised by evergreen, glossy-leaved tree species that look alike with leaves of lauroide type...
forests of the AzoresAzoresThe Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
, and also locally introduced in Cortegada IslandCortegada IslandCortegada is an island in the coast of Pontevedra in Galicia, Spain. It is part of the Atlantic Islands of Galicia National Park.Originally a village of the municipally of O Carril , it was offered as a present to King Alfonso XIII at the start of XX century, then sold to a private company...
, Spain. - Laurus nobilis L.Carolus LinnaeusCarl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...
, known commonly as Bay LaurelBay LaurelThe bay laurel , also known as sweet bay, bay tree, true laurel, Grecian laurel, laurel tree, or simply laurel, is an aromatic evergreen tree or large shrub with green, glossy leaves, native to the Mediterranean region. It is the source of the bay leaf used in cooking...
, True Laurel, Sweet Bay, Grecian Laurel, or simply Laurel, is the source of the spice Bay leafBay leafBay leaf refers to the aromatic leaf of the bay laurel . Fresh or dried bay leaves are used in cooking for their distinctive flavor and fragrance. The leaves are often used to flavor soups, stews, braises and pâtés in Mediterranean cuisine...
. It was also the source of the Laurel wreathLaurel wreathA laurel wreath is a circular wreath made of interlocking branches and leaves of the bay laurel , an aromatic broadleaf evergreen. In Greek mythology, Apollo is represented wearing a laurel wreath on his head...
of ancient GreeceGreeceGreece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
. It is distributed across the Mediterranean region from SpainSpainSpain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
to TurkeyTurkeyTurkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
. - Laurus novocanariensisLaurus novocanariensisLaurus novocanariensis is a evergreen large shrub or tree with aromatic, shiny dark-green foliage. belonging to Laurus genus of evergreen trees belonging to the Laurel family, Lauraceae. The genus includes three species, whose diagnostic key characters often overlap . Under favorable conditions it...
Rivas Mart., Lousã, Fern. Prieto, E.Díaz, J.C. Costa & C. Aguiar, syn. L. canariensis Webb & Berth. (an illegitime name). Formerly included in L.azorica, and also known as the same Portuguese names as L. azorica, is native to the laurisilvaLaurisilvaLaurisilva or laurissilva is a subtropical forest, found in areas with high humidity and relatively stable and mild temperatures. They are characterised by evergreen, glossy-leaved tree species that look alike with leaves of lauroide type...
forests of Madeira Islands and Canary IslandsCanary IslandsThe Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
, and also locally in MoroccoMoroccoMorocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...
.
Fossils dating from before the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
glaciations show that species of Laurus were formerly distributed more widely around the Mediterranean and North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
, when the climate was more humid and mild than at present. It is currently thought that the drying of the Mediterranean basin during the glaciations caused Laurus to retreat to the mildest climate refuges, including southern Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
, Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
and the Macaronesia
Macaronesia
Macaronesia is a modern collective name for several groups of islands in the North Atlantic Ocean near Europe and North Africa belonging to three countries: Portugal, Spain, and Cape Verde...
n islands. With the end of the last glacial period, L. nobilis recovered some of its former range around the Mediterranean.
A recent study found that native stands classified as L. nobilis in northern Spain shared greater genetic and morphological similarity to L. azorica than to populations of L. nobilis native to rest of Spain, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
and Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
[Arroyo-Garcia et al. 2001]. This populations like the Cortegada Island
Cortegada Island
Cortegada is an island in the coast of Pontevedra in Galicia, Spain. It is part of the Atlantic Islands of Galicia National Park.Originally a village of the municipally of O Carril , it was offered as a present to King Alfonso XIII at the start of XX century, then sold to a private company...
population, in Galicia
Galicia
-Geographic regions:* Galicia , an autonomous community in northwestern Spain** Gallaecia, a province of the Roman Empire** Kingdom of Galicia, a medieval kingdom**Nueva Galicia :*** Nueva Galicia, a region of New Spain, now in Mexico...
, famous for its large grove of laurels, come from seeds dispersed by birds but is not indigenous to the island, as this islander forest originated spontaneously from laurel specimens that were planted after the original vegetation was destroyed.
Ecology
The genus come from a few relict species living in temperate areas and more distributed in the Tertiary. The main centers are found inhabiting montane forests or coastal forest in low-altitude. Some species have adapted to more extreme conditions but mostly depending on favorable soil edaphic conditions, as presence of aquifers, groundwater periodic flows, etc.The patterns of speciation in the Lauraceae
Lauraceae
The Lauraceae or Laurel family comprises a group of flowering plants included in the order Laurales. The family contains about 55 genera and over 3500, perhaps as many as 4000, species world-wide, mostly from warm or tropical regions, especially Southeast Asia and South America...
family, where laurus genus belong, indicate that since the onset of aridification on the continents 15 million years ago, rainforest diversified in species numbers with the majority of species the product of vicariance
Vicariance
Vicariance is a process by which the geographical range of an individual taxon, or a whole biota, is split into discontinuous parts by the formation of a physical barrier to gene flow or dispersal. Vicariance of whole biotas occurs following large-scale geophysical events such as the uplift of a...
. 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.
Laurus genus 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. The extant laurel species of this group are relatively young.
The laurus genus features have named many botanical species that are having similar foliage to the Laurus 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 laurina, laurifolia, laurophylla, lauriformis, and lauroides are often used to name species of other plant families that resemble the laurus genus and the Lauraceae family. 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
Laurelia
Laurelia is a genus of flowering plants included in the order Laurales, in the family Atherospermataceae. They are Evergreen fragrant laurifolia trees formerly in the Monimiaceae family....
genus in southern hemisphere, in the family Atherospermataceae
Atherospermataceae
The Atherospermataceae, commonly known as the southern sassafrases, are a family of broadleaf evergreen trees and shrubs. The family includes 14 species in seven genera. The atherosperms are native to the southern hemisphere, with two species native to southern Chile and 12 species native to...
is equivalent to this of Laurus. The three laurel species in the genus laurus are dispersed by birds columbiform, mainly.
History
The laurus genus is characteristic of the formations of laurel forestLaurel forest
Laurel forest is a subtropical or mild temperate forest, found in areas with high humidity and relatively stable and mild temperatures. They are characterized by tree species with evergreen, glossy, enlongated leaves, known as laurophyll or lauroide...
and was more widespread in the Tertiary. It has led to endemic species on islands, but not so widespread geographically as in the past.
The ecological requirements of the species, are those of the laurel forest
Laurel forest
Laurel forest is a subtropical or mild temperate forest, found in areas with high humidity and relatively stable and mild temperatures. They are characterized by tree species with evergreen, glossy, enlongated leaves, known as laurophyll or lauroide...
and like most of their counterparts laurifolia in the world, they are vigorous species with a great ability to populate the habitat that is conducive.
The phylogeography
Phylogeography
Phylogeography is the study of the historical processes that may be responsible for the contemporary geographic distributions of individuals. This is accomplished by considering the geographic distribution of individuals in light of the patterns associated with a gene genealogy.This term was...
of this group provides a nice example of various speciation
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
mechanisms at work. This group became isolated during the Quaternary
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...
glaciations and expansion of the polar ice caps, resulting in widespread cooling of the climate, the flora of central and southern Europe retreated to more southerly latitudes in search of milder conditions. Also the sea level was lower, with lands today submerged forming land bridges.
The end of glaciations coincided with the spread of deserts in North Africa, notably the Sahara, so this type of forest was reduced to those areas, which act as boundaries between temperate and tropical. At that time, the climate of southern Europe was warmer and wetter than today, and the vegetation that surrounded the ancient shores of the Mediterranean Sea was likely similar to that of the current Macaronesian laurisilva. The Ice Age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
which took place at the end of that period and for much of the Quaternary
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...
forced the laurel forest
Laurel forest
Laurel forest is a subtropical or mild temperate forest, found in areas with high humidity and relatively stable and mild temperatures. They are characterized by tree species with evergreen, glossy, enlongated leaves, known as laurophyll or lauroide...
s to move to warmer southern regions, where conditions were more conducive to their survival, settling in this way on the northwest coast of Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
and in the Macaronesian archipelagos.
The ocean permitted the plants' migration to more suitable areas, where they survived.
With the general warming of the atmosphere and the consequent withdrawal of the ice, flora tertiary survivors could not regain their range in southern Europe, as the new post-glacial climate was drier than that of the Tertiary, and to these new environmental requirements, the primitive tropical European flora evolved and gave rise to the present flora of the Mediterranean sclerophyll.
At the same time, isolated from the mainland, the tertiary Macaronesian laurel species evolved independently, which has led endemic species.
Physical separation of the poblations begin a process of change to adapt to new conditions. This mechanism is called allopatric speciation
Allopatric speciation
Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration...
. Over time, survivors specimens of the laurus genus, adapted to different ecological niches. This led to reproductive isolation
Reproductive isolation
The mechanisms of reproductive isolation or hybridization barriers are a collection of mechanisms, behaviors and physiological processes that prevent the members of two different species that cross or mate from producing offspring, or which ensure that any offspring that may be produced is not...
, an example of ecological speciation
Sympatric speciation
Sympatric speciation is the process through which new species evolve from a single ancestral species while inhabiting the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap or are even identical, so that...
.
In Europe the genus is represented by a single species, the named Laurus nobilis. In macaronesian islands this former arose from a common ancestor in the area of laurisilva
Laurisilva
Laurisilva or laurissilva is a subtropical forest, found in areas with high humidity and relatively stable and mild temperatures. They are characterised by evergreen, glossy-leaved tree species that look alike with leaves of lauroide type...
in the Mediterranean area.
The islander laurels of Macaronesia
Macaronesia
Macaronesia is a modern collective name for several groups of islands in the North Atlantic Ocean near Europe and North Africa belonging to three countries: Portugal, Spain, and Cape Verde...
in the eastern Atlantic, are present in the Azores
Azores
The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
, Madeira Islands, and western Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
, from 400 m to 1200 m elevation, in the laurel forest habitat in the islands.
The laurisilva
Laurisilva
Laurisilva or laurissilva is a subtropical forest, found in areas with high humidity and relatively stable and mild temperatures. They are characterised by evergreen, glossy-leaved tree species that look alike with leaves of lauroide type...
forests of Macaronesia are relict
Relict
A relict is a surviving remnant of a natural phenomenon.* In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas....
s of a vegetation
Vegetation
Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...
type which originally covered much of the Mediterranean Basin
Mediterranean Basin
In biogeography, the Mediterranean Basin refers to the lands around the Mediterranean Sea that have a Mediterranean climate, with mild, rainy winters and hot, dry summers, which supports characteristic Mediterranean forests, woodlands, and scrub vegetation...
when the climate
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
of the region was more humid
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
. With the drying of the Mediterranean Basin
Messinian salinity crisis
The Messinian Salinity Crisis, also referred to as the Messinian Event, and in its latest stage as the Lago Mare event, was a geological event during which the Mediterranean Sea went into a cycle of partly or nearly complete desiccation throughout the latter part of the Messinian age of the Miocene...
during the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
, the laurel forests gradually retreated, replaced by more drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
-tolerant sclerophyll
Sclerophyll
Sclerophyll is the term for a type of vegetation that has hard leaves and short internodes . The word comes from the Greek sclero and phyllon ....
plant communities. Most of the last remaining laurisilva forests around the Mediterranean are believed to have disappeared approximately 10,000 years ago at the end of the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
, when the Mediterranean basin became drier and with a harsher climate, although some remnants of the laurel forest flora still persist in the mountains of southern Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
, north-center of Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
and northern Morocco
Morocco
Morocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...
, and two constituent species (Laurus nobilis
Bay Laurel
The bay laurel , also known as sweet bay, bay tree, true laurel, Grecian laurel, laurel tree, or simply laurel, is an aromatic evergreen tree or large shrub with green, glossy leaves, native to the Mediterranean region. It is the source of the bay leaf used in cooking...
and Ilex aquifolium
European Holly
Ilex aquifolium, holly, or european holly, is a species of holly native to western and southern Europe, northwest Africa and southwest Asia.- Overview :...
) remain widespread. The location of the Macaronesian Islands in the North Atlantic Ocean moderated these climatic fluctuations, and maintained the relatively humid and mild climate which has allowed these forests to persist to the present day.