Laurales Introductory article

Susanne S Renner, University of Munich (LMU), Germany Article Contents . Introduction . Families Included

. General Characters and Relationships of Laurales

Online posting date: 16th May 2011

The Laurales are an order of flowering plants comprising have tepals and stamens arranged in three-part whorls and seven families that contain some 2500–2800 species in 100 stamens with valvate anthers. In terms of species richness genera. Most Laurales are tropical trees or shrubs, often and morphological diversity, the family is centred in tro- with scented wood of great durability. Besides being a pical America and Australasia; it is poorly represented in continental Africa, but species-rich in Madagascar source of high quality timber, the Laurales also include the (Chanderbali et al., 2001). Relatively few species, such as avocado tree (Persea americana), a native of Mexico and spice bush, Lindera benzoin, sassafras, Sassafras albidum, Central America, the cinnamon tree and the camphor tree and true or bay laurel, Laurus nobilis, now survive in (Cinnamomum species), native in Southeast Asia, and the temperate zones, but during Palaeocene and Eocene bay laurel (Laurus nobilis), native in the Mediterranean warmer climates Lauraceae were abundant in the northern region. The earliest lauraceous fossils are from the early landmass of Laurasia. The fossil record of the family goes Cretaceous, and within flowering plants, the order is back 110 Ma, and at least 500 species of Lauraceae are among the oldest groups to diversify. The presently known from the early Cretaceous through to the late Ter- accepted classification of the seven families is based on tiary (e.g., Eklund, 2000; Balthazar et al., 2007). See also: molecular sequence data. Dispersal: Biogeography; Fossil Record A genus whose membership in the family was unclear before the advent of molecular data is the herbaceous Introduction parasite Cassytha. Cassytha comprises 16–20 species in tropical Australia, Southeast Asia and Africa that have The order Laurales is part of the earliest radiation of leafless twining stems linked to the host by small haustoria. flowering plants and is the sister group of the Magnoliales. Molecular data show that Cassytha is a part of the core Lauralean fossils date back to the early Cretaceous. This Lauraceae (Rohwer and Rudolph, 2005). See also: Molecu- article presents each family, followed by the few morpho- lar Phylogeny Reconstruction logical characters that unite subgroups of families within the The family’s great economic importance has three order. The absence of a character that would unite all sources. One is the high content of ethereal oils in the wood Laurales historically has led to much controversy about the and leaves of many Lauraceae, which are sources of per- order’s circumscription, with several basal angiosperm fumes, spices and flavourings, such as camphor and cin- families, such as Amborellaceae, Trimeniaceae and Chlor- namon. Another is their hard wood, which makes them one anthaceae, variously being included or excluded in Laurales. of the most valuable sources of tropical timber. Third is the The monophyly of the seven families now considered to avocado, the oil-rich fruit of Persea americana, domesti- form the Laurales first became apparent based on molecular cated several thousand years ago in Central America and data (Renner, 1999). See also: Flowering Plants, Evolution now cultivated in tropical and subtropical climates worldwide. The other species traditionally placed in the genus Persea do not all derive from a common ancestor, Families Included requiring an improved classification (van der Werff, 2002; Rohwer et al., 2009). See also: Crop Plants: Evolution Lauraceae Monimiaceae By far the largest lauralean family is the Lauraceae, with Monimiaceae comprises about 200 in 28 genera, many of 2200–2500 species in 55 genera (Rohwer, 1993). Lauraceae them comprising but one species. They are shrubs or tree- generally are large trees with highly typical flowers that lets occurring in the tropics and subtropics of the southern hemisphere. Until 1999, the family appeared morpho- ELS subject area: Plant Science logically unusually heterogeneous owing to the inclusion of extraneous elements, such as Amborellaceae, Ather- How to cite: ospermataceae, Siparunaceae and Trimeniaceae. Molecu- Renner, Susanne S (May 2011) Laurales. In: eLS. John Wiley & Sons, lar data have revealed a monophyletic family Monimiaceae Ltd: Chichester. in which the oldest divergence is between a group formed DOI: 10.1002/9780470015902.a0003695.pub2 by the South American Peumus boldus, the Australia genus

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Palmeria, and the Re´union endemic genus Monimia on Their wood, especially that of Atherosperma moschatum or the one hand, and the remaining genera on the other hand Tasmanian sassafras, is exploited commercially. The family (Renner et al., 2010). Africa has only a single species, is known from fossil wood and pollen from the Cretaceous Xymalos monospora, which occurs in tropical Africa. of Antarctica. South America has relatively few and species-poor genera; Madagascar and the Mascarene Islands harbour the larg- Gomortegaceae est genus, Tambourissa with some 50 species (Lorence, 1985); and New Zealand, New Caledonia, Australia and Gomortegaceae consists of a single species in Chile, tropical Australasia are the centre of the family’s diversity. Gomortega nitida, a tree in danger of extinction because of The wood of a few species is used for timber and the leaves overharvesting and anthropogenic forest fires. The family’s for medicinal teas. earliest record is fossil wood from late Oligocene–early Miocene deposits in Chilean Patagonia. Hernandiaceae Siparunaceae Hernandiaceae consists of about 60 species in five genera of Siparunaceae consists of two genera, Glossocalyx with one shrubs, treelets and lianas (Kubitzki, 1993a; Michalak et al., species in West Africa and Siparuna with about 65 species 2010). The largest genus, Hernandia, occurs throughout the in the neotropics, mostly in the Andes (Renner and tropics, and several of its species are extremely widespread Hausner, 2005). The family has no confirmed fossil record owing to transoceanic dispersal of their floating fruits. and no commercial interest but the lemon-scented leaves Hazomalania contains a single species that is endemic to play a role in indigenous healing ceremonies of many South Madagascar. Illigera has about a dozen species in China, America tribes. Indochina and Malaysia, three in mainland Africa, and one that occurs in East Africa as well as Madagascar (Figure 1). Calycanthaceae In China, a drug derived from Illigera is used widely to treat arthritis. Gyrocarpus has five species, of which one, Gyro- Calycanthaceae contains three genera and 10 species carpus americanus, may occur in tropical coastal vegetation (Kubitzki, 1993b; Zhou et al., 2006). Calycanthus (includ- worldwide. Sparattanthelium occurs in the Guyana and ing Sinocalycanthus) comprises the frequently cultivated Brazilian shield regions and the Amazon basin. See also: ornamental, Carolina allspice, Calycanthus floridus, the Dispersal: Biogeography Californian allspice, Calycanthus occidentalis, and a Chi- nese species. Chimonanthus comprises six species in China Atherospermataceae of which wintersweet, Chimonanthus praecox, is a widely cultivated ornamental. Finally, Idiospermum consists of The southern sassafrases or Atherospermataceae are a one species in Queensland. This last species, first discovered family of trees and shrubs with two species in Chile and 12 in 1912 and morphologically very different from the other in Australasia (Renner et al., 2000). Atherosperms are an Calycanthaceae, is sometimes placed in a separate family, important element of temperate forests of the southern Idiospermaceae. hemisphere, where they are consistent ecological associates of the southern beeches (Nothofagus, Nothofagaceae). General Characters and Relationships of Laurales

Although molecular data have shown that the seven families described above descended from a common ancestor, no single morphological character is known that reliably distinguishes the order Laurales from all other orders. Part of the reason for this may be that the Laurales diverged from their sister group, the Magnoliales, some- time in the Lower Cretaceous and have since lost their ancestral morphological characters. Two examples of this process are given below. Another reason may be that Laurales are predominantly tropical trees; the morph- ology, anatomy and embryology of which is poorly known. A character seen in most Laurales is a well-developed floral cup, or cupule, that initially encloses the stamens and car- pel (or numerous carpels) and later plays a role in seed Figure 1 Flowers of Illigera cf. thorelii from Vietnam. Photo by Duc Trong dispersal by supporting and displaying the single-seeded Nghiem, Department of Botany, Ha Noi University of Pharmacy, Vietnam. fruits (Figure 2). See also: Cladistics

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A phylogeny of the Laurales (Figure 3) has Calycantha- have apical ovules, whereas Atherospermataceae, Gomor- ceae as forming the first branch, followed by two clusters tega and Siparunaceae ancestrally had basal ovules, a of families, Lauraceae, Monimiaceae and Hernandiaceae, condition lost in Gomortega. Calycanthaceae lack floral and atherosperms, Gomortega and Siparunaceae. This nectaries, whereas most other Laurales have paired nectar phylogeny agrees with the distribution of several mor- glands on the filaments. These glands were lost in Sipar- phological characters. For example, Calycanthaceae have unaceae and in higher Monimiaceae concomitant with a two ovules, whereas all other Laurales have solitary change in pollinators away from nectar-foraging flies and ovules. Lauraceae, Monimiaceae and Hernandiaceae all bees to nonnectar-feeding beetles and gall midges (Endress, 1980; Endress and Lorence, 1983; Feil, 1992). Finally, most Laurales, except Calycanthaceae and Monimiaceae, have stamens with anthers dehiscing by two or four apically hinged valves. Depending on the correct placement of a Calycanthaceae-like fossil flower with laterally hinged valves (Friis et al., 1994), valvate anther dehiscence of some form may be ancestral in Laurales and lost in modern Calycanthaceae and Monimiaceae. See also: Molecular Phylogeny Reconstruction; Phylogeography

References

Balthazar M von, Pedersen KR, Crane PR, Stampanoni M and Friis EM (2007) Potomacanthus lobatus gen. et sp. nov., a new flower of probable Lauraceae from the Early Cretaceous (Early to Middle Albian) of Eastern North America. American Journal Figure 2 Fruits of Mollinedia ovata from Bolivia. Photo by Michael Nee, of Botany 94: 2041–2053. The New York Botanical Garden, New York, USA. Chanderbali AS, van der Werff H and Renner SS (2001) The relationships and historical biogeography of Lauraceae: evi- dence from the chloroplast and nuclear genomes. Annals of the Idiospermum Missouri Botanical Garden 88: 104–134. Calycanthus Calycanthaceae Eklund H (2000) Lauraceous flowers from the Late Cretaceous of Chimonanthus North Carolina, USA. Botanical Journal of the Linnean Society Cinnamonum 132: 397–428. Endress PK (1980) Ontogeny, function and evolution of extreme Lindera Lauraceae floral construction in Monimiaceae. Plant Systematics and Beilschmiedia Evolution 134: 79–120. Hortonia Endress PK and Lorence DH (1983) Diversity and evolutionary Palmeria Monimiaceae trends in the floral structure of Tambourissa (Monimiaceae). Monimia Plant Systematics and Evolution 142: 53–81. Peumus Feil JP (1992) Reproductive ecology of dioecious Siparuna Hernandia (Monimiaceae) in Ecuador – a case of gall midge pollination. Illigera Hernandiaceae Botanical Journal of the Linnean Society 110: 171–203. Sparattanthelium Friis EM, Eklund H, Pedersen KR and Crane PR (1994) Virgi- Gyrocarpus nianthus calycanthoides gen. et sp. nov.: a calycanthaceous Nemuaron flower from the Potomac Group (Early Cretaceous) of eastern Atherosperma North America. International Journal of Plant Sciences 155: Laureliopsis 772–785. Laurelia (Chile) Kubitzki K (1993a) Hernandiaceae. In: Kubitzki K, Rohwer JG Laurelia Atherospermataceae and Bittrich V (eds) The Families and Genera of Vascular Plants, (New Zealand) Dryadodaphne vol. 2, pp. 334–338. Berlin: Springer-Verlag. Doryphora Kubitzki K (1993b) Calycanthaceae. In: Kubitzki K, Rohwer JG Daphnandra and Bittrich V (eds) The Families and Genera of Vascular Plants, Gomortega Gomortegaceae vol. 2, pp. 197–200. Berlin: Springer-Verlag. Lorence DH (1985) A monograph of the Monimiaceae (Laurales) Siparuna Siparunaceae of the Malagasy region (Southwest Indian Ocean). Annals of the Glossocalyx Missouri Botanical Garden 72: 1–165. Liriodendron Magnoliales Michalak I, Zhang LB and Renner SS (2010) Trans-Atlantic, Magnolia trans-Pacific, and trans-Indian Ocean dispersal in the small Figure 3 Phylogeny of the Laurales based on chloroplast DNA sequences Gondwanan Laurales family Hernandiaceae. Journal of Bio- (Renner, 1999). geography 37: 1214–1226.

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Renner SS (1999) Circumscription and phylogeny of the Laurales: Rohwer JG (1993) Lauraceae. In: Kubitzki K et al. (eds) The evidence from molecular and morphological data. American Families and Genera of Vascular Plants, vol. 2, pp. 366–391. Journal of Botany 86: 1301–1315. Berlin: Springer-Verlag. Renner SS and Hausner G (2005) Siparunaceae. In: Flora Neo- Rohwer JG, Li J, Rudolph B et al. (2009) Is Persea (Lauraceae) tropica Monograph, vol. 95, pp. 1–256. New York: The New monophyletic? Evidence from nuclear ribosomal ITS York Botanical Garden Press. ISBN: 0893274623. sequences. Taxon 58: 1153–1167. Renner SS, Murray D and Foreman D (2000) Timing transan- van der Werff H (2002) A synopsis of Persea (Lauraceae) in tarctic disjunctions in the Atherospermataceae (Laurales): Central America. Novon 12: 575–586. evidence from coding and noncoding chloroplast sequences. Zhou S, Renner SS and Wen J (2006) Molecular phylogeny and Systematic Biology 49: 579–591. inter- and intracontinental biogeography of Calycanthaceae. Renner SS, Strijk JS, Strasberg D and The´baud C (2010) Bio- Molecular Phylogenetics and Evolution 39: 1–15. geography of the Monimiaceae (Laurales): a role for East Gondwana and long distance dispersal, but not West Gon- dwana. Journal of Biogeography 37: 1227–1238. Further Reading Rohwer J and Rudolph B (2005) Jumping genera: the phylo- genetic positions of Cassytha, Hypodaphnis, and Neo- Renner SS (2005) Variation in diversity among Laurales, Early cinnamomum (Lauraceae) based on different analyses of trnK Cretaceous to Present. Biologiske Skrifter, Copenhagen 55: intron sequences. Annals of the Missouri Botanical Garden 92: 441–458. 153–178.

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