Phylogenetics of Cucumis (Cucurbitaceae)

Background: Melon, Cucumis melo, and cucumber, C. sativus, are among the most widely cultivated crops worldwide. Cucumis, as traditionally conceived, is geographically centered in Africa, with C. sativus and C. hystrix thought to be the only Cucumis species in Asia. This taxonomy forms the basis for all ongoing Cucumis breeding and genomics efforts. We tested relationships among Cucumis and related genera based on DNA sequences from chloroplast gene, intron, and spacer regions (rbcL, matK, rpl20-rps12, trnL, and trnL-F), adding nuclear internal transcribed spacer sequences to resolve relationships within Cucumis. Results: Analyses of combined chloroplast sequences (4,375 aligned nucleotides) for 123 of the 130 genera of Cucurbitaceae indicate that the genera Cucumella, Dicaelospermum, Mukia, Myrmecosicyos, and Oreosyce are embedded within Cucumis. Phylogenetic trees from nuclear sequences for these taxa are congruent, and the combined data yield a well-supported phylogeny. The nesting of the five genera in Cucumis greatly changes the natural geographic range of the genus, extending it throughout the Malesian region and into Australia. The closest relative of Cucumis is Muellerargia, with one species in Australia and Indonesia, the other in Madagascar. Cucumber and its sister species, C. hystrix, are nested among Australian, Malaysian, and Western Indian species placed in Mukia or Dicaelospermum and in one case not yet formally described. Cucumis melo is sister to this Australian/Asian clade, rather than being close to African species as previously thought. Molecular clocks indicate that the deepest divergences in Cucumis, including the split between C. melo and its Australian/Asian sister clade, go back to the mid-Eocene. Conclusion: Based on congruent nuclear and chloroplast phylogenies we conclude that Cucumis comprises an old Australian/Asian component that was heretofore unsuspected. Cucumis sativus evolved within this Australian/Asian clade and is phylogenetically far more distant from C. melo than implied by the current morphological classification

Structure and Development of Flowers and Inflorescences in Burmannia (Burmanniaceae, Dioscoreales)

Species of the genus Burmannia possess distinctive and highly elaborated flowers with prominent floral tubes that often bear large longitudinal wings. Complicated floral structure of Burmannia hampers understanding its floral evolutionary morphology and biology of the genus. In addition, information on structural features believed to be taxonomically important is lacking for some species. Here we provide an investigation of flowers and inflorescences of Burmannia based on a comprehensive sampling that included eight species with various lifestyles (autotrophic, partially mycoheterotrophic and mycoheterotrophic). We describe the diversity of inflorescence architecture in the genus: a basic (most likely, ancestral) inflorescence type is a thyrsoid comprising two cincinni, which is transformed into a botryoid in some species via reduction of the lateral cymes to single flowers. Burmannia oblonga differs from all the other studied species in having an adaxial (vs. transversal) floral prophyll. For the first time, we describe in detail early floral development in Burmannia. We report presence of the inner tepal lobes in B. oblonga, a species with reportedly absent inner tepals; the growth of the inner tepal lobes is arrested after the middle stage of floral development of this species, and therefore they are undetectable in a mature flower. Floral vasculature in Burmannia varies to reflect the variation of the size of the inner tepal lobes; in B. oblonga with the most reduced inner tepals their vascular supply is completely lost. The gynoecium consists of synascidiate, symplicate, and asymplicate zones. The symplicate zone is secondarily trilocular (except for its distal portion in some of the species) without visible traces of postgenital fusion, which prevented earlier researchers to correctly identify the zones within a definitive ovary. The placentas occupy the entire symplicate zone and a short distal portion of the synascidiate zone. Finally, we revealed an unexpected diversity of stamen-style interactions in Burmannia. In all species studied, the stamens are tightly arranged around the common style to occlude the flower entrance. However, in some species the stamens are free from the common style, whereas in the others the stamen connectives are postgenitally fused with the common style, which results in formation of a gynostegium

Biogeography of the monocotyledon astelioid clade (Asparagales): A history of long-distance dispersal and diversification with emerging habitats

The astelioid families (Asteliaceae, Blandfordiaceae, Boryaceae, Hypoxidaceae, and Lanariaceae) have centers of diversity in Australasia and temperate Africa, with secondary centers of diversity in Afromontane Africa, Asia, and Pacific Islands. The global distribution of these families makes this an excellent lineage to test if current distribution patterns are the result of vicariance or long-distance dispersal and to evaluate the roles of tertiary climatic and geological drivers in lineage diversification. Sequence data were generated from five chloroplast regions (petL-psbE, rbcL, rps16-trnK, trnL-trnLF, trnS-trnSG) for 104 ingroup species sampled across global diversity. The astelioid phylogeny was inferred using maximum parsimony, maximum likelihood, and Bayesian inference methods. Divergence dates were estimated with a relaxed clock applied in BEAST. Ancestral ranges were reconstructed in 'BioGeoBEARS' applying the corrected Akaike information criterion to test for the best-fit biogeographic model. Diversification rates were estimated in Bayesian Analysis of Macroevolutionary Mixtures [BAMM]. Astelioid relationships were inferred as Boryaceae(Blandfordiaceae(Asteliaceae(Hypoxidaceae plus Lanariaceae))). The crown astelioid node was dated to the Late Cretaceous (75.2 million years; 95% highest posterior densities interval 61.0-90.0 million years) with an inferred Eastern Gondwanan origin. However, astelioid speciation events have not been shaped by Gondwanan vicariance. Rather long-distance dispersal since the Eocene is inferred to account for current distributions. Crown Asteliaceae and Boryaceae have Australian ancestral ranges and diversified since the Eocene. In Hypoxidaceae, Empodium, Hypoxis, and Pauridia have African ancestral ranges; Curculigo and Molineria have an Asian ancestral range and have diversified since the mid-Miocene. Diversification of Pauridia and the Curculigo clade has occurred steadily, while diversification of Astelia and Hypoxis was punctuated over time. Diversification of those genera coincides temporally with the expansion of the habitat types occupied by extant taxa, e.g., grassland habitat in Africa during the late Miocene and alpine habitat in New Zealand during the Pliocene

New combinations in Aeridinae (Orchidaceae).

New combinations are made in the genera Arachnis, Brachypeza, Dimorphorchis, Grosourdya, Phalaenopsis, Renanthera, Robiquetia, Taeniophyllum, Thrixspermum, Trachoma and Trichoglottis. Two new subgenera are established in Phalaenopsis (subgen. Ornithochilus and Hygrochilus). These changes are proposed to begin aligning the genera recognized in subtribe Aeridinae with results of recent DNA analyses (published elsewhere)

Lactarius megalopterus, a new angiocarpous species from a tropical rainforest in Central Africa, shows adaptations to endozoochorous spore dispersal

A new sequestrate Lactarius species was found in a humid evergreen tropical rainforest dominated by Fabaceae of the subfamily Caesalpinioideae in Cameroon, Central Africa. It is described here as new to science and is named Lactarius megalopterus, referring to its spore ornamentation of extraordinarily high wings. Anatomical characters and molecular systematic analyses confirm its relationship to Lactarius subgenus Plinthogali. Phylogenetic analyses based on two nuclear DNA regions revealed its close relationship to Lactarius angiocarpus, which is also an angiocarpous species from Zambia in Africa. Molecular studies have shown that tuber-like, sequestrate sporocarps evolved independently in several lineages of Basidiomycota. The findings of sequestrate fungi in tropical rainforests raise questions regarding the evolutionary benefit of enclosing the spore-producing hymenium. The enclosure of spore-producing tissue has often been associated with the protection of the delicate hymenium against desiccation in arid habitats or against frost in cold habitats. However, these cannot be the selective factors in warm and humid areas like the tropics. This controversy is exemplarily studied and discussed in the family of Russulaceae, especially in the genus Lactarius. Characters shown by the angiocarpous sporocarp of the new Lactarius, such as thick-walled statismospores, an aromatic smell and mild taste, can be interpreted as adaptations to endozoochorous spore dispersal by mammals. Therefore, here we prefer the alternative hypothesis that sequestrate sporocarps are the result of adaptation to endozoochorous spore dispersal.ISSN:1617-416XISSN:1861-895

Phylogenetics of <it>Cucumis </it>(Cucurbitaceae): Cucumber <it/>(<it>C. sativus</it>) belongs in an Asian/Australian clade far from melon (<it>C. melo</it>)

<p>Abstract</p> <p>Background</p> <p>Melon, <it>Cucumis melo</it>, and cucumber, <it>C. sativus</it>, are among the most widely cultivated crops worldwide. <it>Cucumis</it>, as traditionally conceived, is geographically centered in Africa, with <it>C. sativus </it>and <it>C. hystrix </it>thought to be the only <it>Cucumis </it>species in Asia. This taxonomy forms the basis for all ongoing <it>Cucumis </it>breeding and genomics efforts. We tested relationships among <it>Cucumis </it>and related genera based on DNA sequences from chloroplast gene, intron, and spacer regions (<it>rbcL</it>, <it>matK</it>, <it>rpl20-rps12</it>, <it>trnL</it>, and <it>trnL-F</it>), adding nuclear internal transcribed spacer sequences to resolve relationships within <it>Cucumis</it>.</p> <p>Results</p> <p>Analyses of combined chloroplast sequences (4,375 aligned nucleotides) for 123 of the 130 genera of Cucurbitaceae indicate that the genera <it>Cucumella</it>, <it>Dicaelospermum</it>, <it>Mukia</it>, <it>Myrmecosicyos</it>, and <it>Oreosyce </it>are embedded within <it>Cucumis</it>. Phylogenetic trees from nuclear sequences for these taxa are congruent, and the combined data yield a well-supported phylogeny. The nesting of the five genera in <it>Cucumis </it>greatly changes the natural geographic range of the genus, extending it throughout the Malesian region and into Australia. The closest relative of <it>Cucumis </it>is <it>Muellerargia</it>, with one species in Australia and Indonesia, the other in Madagascar. Cucumber and its sister species, <it>C. hystrix</it>, are nested among Australian, Malaysian, and Western Indian species placed in <it>Mukia </it>or <it>Dicaelospermum </it>and in one case not yet formally described. <it>Cucumis melo </it>is sister to this Australian/Asian clade, rather than being close to African species as previously thought. Molecular clocks indicate that the deepest divergences in <it>Cucumis</it>, including the split between <it>C. melo </it>and its Australian/Asian sister clade, go back to the mid-Eocene.</p> <p>Conclusion</p> <p>Based on congruent nuclear and chloroplast phylogenies we conclude that <it>Cucumis </it>comprises an old Australian/Asian component that was heretofore unsuspected. <it>Cucumis sativus </it>evolved within this Australian/Asian clade and is phylogenetically far more distant from <it>C. melo </it>than implied by the current morphological classification.</p

Exine micromorphology and ultrastructure in Neottieae (Epidendroideae, Orchidaceae)

The diverse epidendroid orchid tribe Neottieae is characterized by multiple transitions between autotrophy and mycoheterotrophy, allogamous and autogamous mating systems, pollen released as tetrads or monads, and pollen exine tectate or semitectate. We use transmission and scanning electron microscopy on pollen of ten species of Neottieae to investigate whether the differences in pollen aggregation and exine micromorphology and ultrastructure reflect phylogenetic relationships, or whether this variation is subject to ecological constraints. Our results showed that differences in exine micromorphology are mostly concordant with phylogenetic relationships in Neottieae, i.e. an ascending tendency of pollen ornamentation from tectate (Cephalanthera) to semitectate (e.g. Neottia). In contrast, pollen aggregation, when plotted on the most recent phylogeny, shows repeated transitions between monads and tetrads that could be related to ecological constraints. Tetrads are present in species that are nectar rewarding, whereas monads are common in deceptive species. Cephalanthera is characterized by recalcitrant pollen, including the frequent occurrence of collapsed pollen. In this genus, the observed shifts from allogamous to autogamous or cleistogamous mating systems could help to reduce pollen damage caused by exposure to dry habitats. © 2013 Springer-Verlag Wien