Gwilym P. Lewis

Phylogenetic Relationships in the Caesalpinioideae (Leguminosae) as Inferred from Chloroplast trnL Intron Sequences

Abstract The basal subfamily Caesalpinioideae of the Leguminosae generally is subdivided into four or five tribes, but their monophyly remains questionable. Recent cladistic analyses based on morphological characters and chloroplast rbcL sequences suggest conflicting hypotheses of relationships among tribes and subtribal groupings and of the identification of the basal Caesalpinioideae. Our phylogenetic analysis of the chloroplast trnL intron for 223 Caesalpinioideae, representing 112 genera, plus four Papilionoideae, 12 Mimosoideae and three outgroup taxa, provides some well-supported hypotheses of relationships for the subfamily. Our analysis concurs with the rbcL studies in suggesting that a monophyletic Cercideae is sister to the remainder of the Leguminosae. Among the other tribes of Caesalpinioideae, only the broadly circumscribed Detarieae (including Amherstieae or Macrolobieae) is also supported as monophyletic. The Detarieae s.l. occurs as sister to all Leguminosae, excluding Cercideae. Cassieae subtribes Dialiinae and Labicheinae together are sister to the remaining Leguminosae, which includes a monophyletic Papilionoideae, a paraphyletic Mimosoideae, and several monophyletic groups that correspond to previously defined generic groups or subtribes in the Caesalpinioideae. The trnL intron analysis suggests that basal legumes are extremely diverse in their floral morphology, and that presence of simple, actinomorphic flowers may be a derived feature in a number of lineages in the family. Communicating Editor: Matt Lavin

Phylogenetic patterns and diversification in the caesalpinioid legumesThis paper is one of a selection of papers published in the Special Issue on Systematics Research.

Subfamily Caesalpinioideae is a paraphyletic grade of 171 genera that comprises the first branches of the Leguminosae and from which are derived the monophyletic subfamilies Mimosoideae and Papilionoideae. We have sequenced the chloroplast matK gene, and the trnL and 3′-trnK introns for 153 genera of caesalpinioid legumes. Parsimony and Bayesian phylogenetic analyses of these data support the monophyly of several major groups within the caesalpinioid legumes: the Cercideae, Detarieae, Detarieae s. str., Prioria, Amherstieae, Dialiinae, Cassia, Caesalpinia, Peltophorum, and Tachigali clades. Relationships among the first branching lineages of the legumes are not well supported, with Cercideae, Detarieae, and the genus Duparquetia alternatively resolved as sister group to all of the legumes. The division of certain large genera (e.g., Caesalpinia s. l., Bauhinia s. l.) into segregate genera generally is supported by our molecular data. Using 18 well-documented fossils as calibration points, fixing the stem ...

Contrasting plant diversification histories within the Andean biodiversity hotspot

The Andes are the most species-rich global biodiversity hotspot. Most research and conservation attention in the Andes has focused on biomes such as rain forest, cloud forest, and páramo, where much plant species diversity is the hypothesized result of rapid speciation associated with the recent Andean orogeny. In contrast to these mesic biomes, we present evidence for a different, older diversification history in seasonally dry tropical forests (SDTF) occupying rain-shadowed inter-Andean valleys. High DNA sequence divergence in Cyathostegia mathewsii, a shrub endemic to inter-Andean SDTF, indicates isolation for at least 5 million years of populations separated by only ca. 600 km of high cordillera in Peru. In conjunction with fossil evidence indicating the presence of SDTF in the Andes in the late Miocene, our data suggest that the disjunct small valley pockets of inter-Andean SDTF have persisted over millions of years. These forests are rich in endemic species but massively impacted, and merit better representation in future plans for science and conservation in Andean countries.

The genus Bauhinia s.l. (Leguminosae): a phylogeny based on the plastid trnL-trnF region.

As the largest genus in tribe Cercideae, the pantropical genus Bauhinia has been the subject of a number of regional treatments in which it has been recognized either as a single genus with several subgenera or as several distinct genera. With the aim to better understand the taxon relationships within Bauhinia and between it and related genera, we have sequenced the plastid trnL–trnF region for 85 species, which together are representative of the eight genera recognized within Bauhinia sensu lato by some workers. In addition, representative taxa were verified for the presence or absence of the plastid rpl2 intron, which previous studies indicated might be a marker for specific lineages within Bauhinia s.l. Both Bayesian and parsimony analyses indicate that Bauhinia s.l. is paraphyletic with the monospecific genus Brenierea clustered within it. This genus, usually described as sister to Bauhinia s.l., forms a clade with the genera Piliostigma and Bauhinia sensu stricto. The remaining genera (Gigasiphon, T...

Reproductive biology ofCaesalpinia calycina andC. pluviosa (Leguminosae) of the caatinga of north-eastern Brazil

The pollination biology, breeding system and fruiting success ofCaesalpinia calycina andC. pluviosa var.sanfranciscana were studied in caatinga vegetation in Bahia, NE Brazil. The principal pollinators for both species were carpenter bees.Caesalpinia calycina is andromonoecious but inC. pluviosa all flowers are hermaphrodite. InC. calycina all selfed flowers were abscised within 72 h despite rapid self-pollen tube growth to the ovary and ovule penetration. Prevention of selfing therefore seems to be controlled by a post-zygotic mechanism. Both species had very low fruit-set and it is suggested that this is at least in part due to geitonogamous pollinations with ovule penetration by self pollen tubes.

A phylogenetic reappraisal of the Peltophorum group (Caesalpinieae: Leguminosae) based on the chloroplast trnL-F, rbcL and rps16 sequence data

The monophyly of the Peltophorum group, one of nine informal groups recognized by Polhill in the Caesalpinieae, was tested using sequence data from the trnL-F, rbcL, and rps16 regions of the chloroplast genome. Exemplars were included from all 16 genera of the Peltophorum group, and from 15 genera representing seven of the other eight informal groups in the tribe. The data were analyzed separately and in combined analyses using parsimony and Bayesian methods. The analysis method had little effect on the topology of well-supported relationships. The molecular data recovered a generally well-supported phylogeny with many intergeneric relationships resolved. Results show that the Peltophorum group as currently delimited is polyphyletic, but that eight genera plus one undescribed genus form a core Peltophorum group, which is referred to here as the Peltophorum group sensu stricto. These genera are Bussea, Conzattia, Colvillea, Delonix, Heteroflorum (inedit.), Lemuropisum, Parkinsonia, Peltophorum, and Schizolobium. The remaining eight genera of the Peltophorum group s.l. are distributed across the Caesalpinieae. Morphological support for the redelimited Peltophorum group and the other recovered clades was assessed, and no unique synapomorphy was found for the Peltophorum group s.s. A proposal for the reclassification of the Peltophorum group s.l. is presented.

Floral morphology in caesalpinioid legumes: Testing the monophyly of the Umtiza clade

The legume subfamily Caesalpinioideae forms a basal grade in the family, within which the subfamilies Mimosoideae and Papilionoideae are nested. Monophyletic groups within Caesalpinioideae include the tribes Cercideae, which is grouped sister to all remaining legumes, and Detarieae s.l., which is monophyletic only if the monospecific genus Umtiza is excluded. Umtiza is endemic to South Africa and has traditionally been included in the Detarieae, but its placement there has long been questioned. We present phylogenetic analyses of data from the chloroplast trnL intron and trnL‐F spacer and morphology that resulted in a single most parsimonious tree in which Umtiza is grouped with six other small caesalpinioid genera in an association of taxonomically and biogeographically disparate taxa. Umtiza, Gleditsia, and Gymnocladus form a clade that is sister to Ceratonia, Acrocarpus, Arcoa, and Tetrapterocarpon. Although these seven genera are dissimilar in many respects, they share several potential morphological synapomorphies, one of which is the presence of dioecy, which occurs in Gymnocladus, Gleditsia, Ceratonia, Arcoa, and Tetrapterocarpon. However, the occasional occurrence of apparently bisexual flowers in several of these genera complicates our understanding of the evolutionary history of sexual expression in these plants. Flowers in the Umtiza clade are small and green to white in color (green with a colorful hypanthium in Acrocarpus). Perianth structure has been of interest in this group, especially in Gleditsia and Gymnocladus, which have been portrayed as having a poorly differentiated calyx and corolla. This has been interpreted as evidence that they are among the most archaic members of the family. However, although the calyx and corolla are similarly colored, they are easily distinguished on the basis of size and texture. Thus, the characterization is inaccurate, and the evolutionary interpretation is unsupported. The greenish perianth and other unusual aspects of floral morphology observed in the Umtiza clade are clearly apomorphies and not plesiomorphic features for the family.

Maraniona. A new dalbergioid legume genus (Leguminosae, Papilionoideae) from Peru

Abstract A new papilionoid legume genus, Maraniona, is described based on recent collections from the Marañon Valley in northern Peru. The sister group relationships of Maraniona are analyzed using a combination of non-molecular and chloroplast DNA matK/trnK sequence data that incorporate comprehensive generic level sampling across the dalbergioid legumes. This analysis places Maraniona in a strongly supported subclade of the informal Pterocarpus clade of the dalbergioid legumes. We discuss the endemic status of Maraniona in relation to overall endemism in the upper Marañon Valley as well as the possible affinities of Maraniona to the genus Tipuana from Argentina and Bolivia.

Taxonomic and functional implications of stigma morphology in species ofCassia, Chamaecrista, andSenna (Leguminosae:Caesalpinioideae)

Two stigma forms occur inChamaecrista andSenna, but only one inCassia. In the common chambered form, a stigma pore is positioned on the reflexed style tip and is the entrance to a tapering chamber. The pore rim is fringed by hairs which vary in number, size, distribution and shape. In the alternative form the stigma is situated at the apex of the curved style and is crateriform. The crater rim is fringed by hairs of variable number and shape. The stigmatic hairs are predominantly unicellular and cutinized. Stigma and hair differences aid in the taxonomy of the genera. Their functions in pollination biology are discussed.

Alpha e-taxonomy: responses from the systematics community to the biodiversity crisis

SummaryThe crisis facing the conservation of biodiversity is reflected in a parallel crisis in alpha taxonomy. On one hand, there is an acute need from government and non-government organisations for large-scale and relatively stable species inventories on which to build major biodiversity information systems. On the other, molecular information will have an increasingly important impact on the evidential basis for delimiting species and is likely to result in greater scientific debate and controversy on their circumscription. This paper argues that alpha-taxonomy built on the Internet (alpha e-taxonomy) can provide a key component of the solution. Two main themes are considered: (1) the potential of e-taxonomic revisions for engaging both the specialist taxonomic community and a wider public in gathering taxonomic knowledge and deepening understanding of it, and (2) why alpha-species will continue to play an essential role in the conventional definition of species and what kinds of methodological development this implies for descriptive species taxonomy. The challenges and requirements for sustaining e-taxonomic revisions in the long-term are discussed, with particular reference to models being developed by five initiatives with botanical exemplar websites: CATE (Creating a Taxonomic E-Science), Solanaceae Source, GrassBase and EDIT (European Distributed Institute of Taxonomy) exemplar groups and scratchpads. These projects give a clear indication of the crucially important role of the national and regional taxonomic organisations and their networks in providing both leadership and a fruitful and beneficial human and technical environment for taxonomists, both amateur and professional, to contribute their expertise towards a collective global enterprise.