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Affinities of the Ocotea (Lauraceae) species from Cuba
Abstract
The affinities of the Ocotea species from Cuba are examined based on sequences of the nuclear ITS region and the chloroplast psbA-trnH spacer, supplemented by SEM studies on stomatal morphology. The species with bisexual flowers, all of them endemic either to the Greater Antilles or Cuba only, form (at least) two phylogenetically distinct groups. Ocotea bucheri, O. libanensis, O. moaensis, O. reticularis, and an undescribed species, all of them endemics of Eastern Cuba, form the sister group to the genus Damburneya. The remaining species form two clades nested in the Praelicaria clade. It remains uncertain if these two clades are sister to each other or not. The two widespread dioecious species show the expected affinities to conspecific material from other parts of the Neotropics.
Two new species of Ocotea (Lauraceae) from Cuba are described based on morphological data combined with the result of a previous molecular phylogenetic analysis.
Cinnamomum is among the largest genera of the Lauraceae, including species from tropical to temperate Asia and from tropical to subtropical America. However, previous studies indicated that Cinnamomum might not be monophyletic in its current circumscription. We therefore re-investigated the genus and possible relatives with an increased taxon sample, particularly of the Neotropical species. Our results, based on sequences of the nuclear ITS region and the chloroplast spacers psbA-trnH and trnG-trnS, show that the Neotropical Cinnamomum species indeed do not form a monophyletic group with the Paleotropical species. Instead, the American species form a clade in which most species of the Neotropical genus Aiouea are nested within
several subclades. According to the ITS data the Aiouea/Cinnamomum clade is sister to the likewise predominantly Neotropical Ocotea complex, rather than the two Paleotropical Cinnamomum clades. Therefore, Cinnamomum cannot be upheld in its current circumscription. As the type C. verum, is from Asia, the Neotropical species need to be placed in a different genus. We decided to transfer them to Aiouea here, because this is the oldest generic name in the Aiouea/Cinnamomum clade, and the only character separating Aiouea from Neotropical Cinnamomum is the number of pollen sacs per anther (di- vs. tetrasporangiate),
a feature that is known to be variable within several other genera as well. This transfer requires 42 new combinations and two nomina nova. In addition, six species described in the unpublished Ph.D. thesis of one of the authors (FLH) are validated in Aiouea here, and the only species of the genus Mocinnodaphne is transferred to Aiouea as well.
The Araucaria Forests in southern Brazil are part of the Atlantic Rainforest, a key hotspot for global biodiversity. This habitat has experienced extensive losses of vegetation cover due to commercial logging and the intense use of wood resources for construction and furniture manufacturing. The absence of precise taxonomic tools for identifying Araucaria Forest tree species motivated us to test the ability of DNA barcoding to distinguish species exploited for wood resources and its suitability for use as an alternative testing technique for the inspection of illegal timber shipments. We tested three cpDNA regions (matK, trnH-psbA, and rbcL) and nrITS according to criteria determined by The Consortium for the Barcode of Life (CBOL). The efficiency of each marker and selected marker combinations were evaluated for 30 commercially valuable woody species in multiple populations, with a special focus on Lauraceae species. Inter- and intraspecific distances, species discrimination rates, and ability to recover species-specific clusters were evaluated. Among the regions and different combinations, ITS was the most efficient for identifying species based on the 'best close match' test; similarly, the trnH-psbA + ITS combination also demonstrated satisfactory results. When combining trnH-psbA + ITS, Maximum Likelihood analysis demonstrated a more resolved topology for internal branches, with 91% of species-specific clusters. DNA barcoding was found to be a practical and rapid method for identifying major threatened woody angiosperms from Araucaria Forests such as Lauraceae species, presenting a high confidence for recognizing members of Ocotea. These molecular tools can assist in screening those botanical families that are most targeted by the timber industry in southern Brazil and detecting certain species protected by Brazilian legislation and could be a useful tool for monitoring wood exploitation.
Sassafras (Lauraceae) consists of three species disjunct between eastern Asia (S. tzumu and S. randaiense) and eastern North America (S. albidum). Phylogenetic analysis based on sequences of nuclear ribosomal ITS and three chloroplast non-coding regions (rpl16, trnL-F, and psbA-trnH) showed that Sassafras is monophyletic and that the eastern North American S. albidum is sister to the clade of its two eastern Asian counterparts. Their intercontinental divergence was estimated to be 13.80
± 2.29−16.69 ± 2.52 million years ago (mya) using the penalized likelihood method with the ITS and three chloroplast markers.
Biogeographic analyses combined with fossil evidence suggest that Sassafras has a relict distribution in the Northern Hemisphere without a Gondwanan link. The divergence time of the two eastern Asian
species (the continental Chinese Sassafras tzumu and S. randaiense endemic to Taiwan) is estimated to be 0.61 ± 0.75−2.23 ± 0.76 mya. Sassafras randaiense from Taiwan was most likely derived from an ancestor from continental China.
Premise:
The Ocotea complex contains the greatest diversity of Lauraceae in the Neotropics. However, the traditional taxonomy of the group has relied on only three main floral characters, and previous molecular analyses have used only a few markers and provided limited support for relationships among the major clades. This lack of useful data has hindered the development of a comprehensive classification, as well as studies of character evolution.
Methods:
We used RAD-seq data to infer the phylogenetic relationships of 149 species in the Ocotea complex, generating a reference-based assembly using the Persea americana genome. The results provide the basis for a phylogenetic classification that reflects our current molecular knowledge and for analyses of the evolution of breeding system, stamen number, and number of anther locules.
Results:
We recovered a well-supported tree that demonstrates the paraphyly of Licaria, Aniba, and Ocotea and clarifies the relationships of Umbellularia, Phyllostemonodaphne, and the Old World species. To begin the development of a new classification and to facilitate precise communication, we also provide phylogenetic definitions for seven major clades. Our ancestral reconstructions show multiple origins for the three floral characters that have routinely been used in Lauraceae systematics, suggesting that these be used with caution in the future.
Conclusions:
This study advances our understanding of phylogenetic relationships and character evolution in a taxonomically difficult group using RAD-seq data. Our new phylogenetic names will facilitate unambiguous communication as studies of the Ocotea complex progress.
Ocotea is one of the largest genera in the Lauraceae (c. 400 spp.), and it has been known to be paraphyletic with respect to most other genera of the New World Lauraceae for almost 20 years. In the traditional circumscription, Ocotea contains not only Neotropical species, but also about 45 species from the African region, including Macaronesia, Madagascar, and the Comoro and Mascarene Islands. Only a few of the species have been included in previous molecular systematic analyses. Here we present a phylogenetic analysis, based on ITS and psbA-trnH sequences of 168 Lauraceae species, including 151 taxa from the Ocotea complex, among them 26 of the 45 Palaeotropical species currently placed in Ocotea. Our results show that the Old World species belong to two well-supported and morphologically distinguishable clades, one of which is placed unresolved among the Neotropical clades of the Ocotea complex, whereas the other is sister to Cinnamomum section Cinnamomum. The two clades can also be differentiated based morphologically. As a step towards a phylogenetic classification, we recognize the second group as the new genus Kuloa.
The large genus Ocotea (c. 400 species) has been known to be paraphyletic with respect to most other Neotropical genera of Lauraceae for almost 20 years, but a phylogenetic classification has not yet been proposed. Here we present a phylogenetic analysis, based on ITS and psbA-trnH sequences of 123 species from the Ocotea complex, focused on
the Neotropical species with bisexual flowers. Our results show that several well supported clades can be recognized morphologically. We discuss the principles of splitting monophyletic genera from large paraphyletic groups, and we reinstate the genus Mespilodaphne as a first step towards a phylogenetic classification. In addition, three species previously included in Aiouea are transferred to Damburneya.
Earlier studies indicated that the genus Nectandra, currently the second-largest genus of the Neotropical Lauraceae, might be diphyletic in its traditional circumscription, but the evidence was not quite conclusive. Our phylogenetic analyses based on nuclear (ITS) and chloroplast (psbA-trnH) sequences of 45 Nectandra species as well as 42 representatives of 18 genera of the core Lauraceae (Ocotea complex, Laureae, Aiouea, Asian Cinnamomum and Persea groups) confirm the suspicion that Nectandra is diphyletic. The two groups, Nectandra s.str. and the N. coriacea group, are each well supported in the maximum parsimony and Bayesian analyses, but they are not sister to each other. Nectandra s.str. is sister to Pleurothyrium, and the clade including Nectandra s.str. and Pleurothyrium is very likely closer to the dioecious taxa of the Ocotea complex. The N. coriacea group, on the other hand, appears to be closer to bisexual taxa known as the Ocotea helicterifolia group. In addition, Nectandra s.str. is characterized by a large deletion in the psbA-trnH spacer compared to all other core Lauraceae, including its sister group Pleurothyrium. Considering these facts, Nectandra cannot be maintained in the traditional sense. We therefore transfer the species of the N. coriacea group to the oldest generic name applied to this group, Damburneya. On the basis of fossil records from the American subcontinents and in accordance with previous phylogenetic and molecular clock studies we suggest a scenario of a climate-driven migration from North to South America, with a subsequent rapid radiation of Nectandra s.str. in South America.
Phylogenetic relationships among 122 species of Lauraceae representing 44 of the 55 currently recognized genera are inferred from sequence variation in the chloroplast and nuclear genomes. The trnL-trnF, trnT-trnL, psbA-trnH, and rpl16 regions of cpDNA, and the 5′ end of 26S rDNA resolved major lineages, while the ITS/5.8S region of rDNA resolved a large terminal clade. The phylogenetic estimate is used to assess morphology-based views of relationships and, with a temporal dimension added, to reconstruct the biogeographic history of the family. Results suggest Lauraceae radiated when trans-Tethyean migration was relatively easy, and basal lineages are established on either Gondwanan or Laurasian terrains by the Late Cretaceous. Most genera with Gondwanan histories place in Cryptocaryeae, but a small group of South American genera, the Chlorocardium-Mezilaurus clade, represent a separate Gondwanan lineage. Caryodaphnopsis and Neocinnamomum may be the only extant representatives of the ancient Lauraceae flora documented in Mid- to Late Cretaceous Laurasian strata. Remaining genera place in a terminal Perseeae-Laureae clade that radiated in Early Eocene Laurasia. Therein, non-cupulate genera associate as the Persea group, and cupuliferous genera sort to Laureae of most classifications or Cinnamomeae sensu Kostermans. Laureae are Laurasian relicts in Asia. The Persea group and Cinnamomum group (of Cinnamomeae) show tropical amphi-Pacific disjunctions here credited to disruption of boreotropical ranges by Eocene-Oligocene climatic cooling. The Ocotea complex accommodates remaining Cinnamomeae and shows a trans-Atlantic disjunction possibly derived from a Madrean-Tethyan ancestral distribution. These findings support Laurasian ancestry for most extant Lauraceae, with their considerable neotropical representation primarily derived from Early Miocene radiation of the Ocotea complex upon reaching South America.
Der Autor beschreibt 28 neue Arten von Bumen aus der Flora von Cuba, die anlßlich dendrologischer Studien und bei der Vorbereitung einer Dendroflora für Cuba aufgefunden und als neu erkannt wurden.The author gives the description of 28 species of cuban trees, found in dendrological studies and the preparation of a dendrological flora of Cuba.
Kritičeskie zametki o nekotoryh ėndemičnyh vidah roda Ocotea Aubl. (Lauraceae) flory Kuby (Notae criticae de generis Ocotea Aubl. (Lauraceae) speciebus endemicis nonnullis florae Cubae)
- Imchanitzkaja N. N.