The origin and speciation of orchids.

Orchids constitute one of the most spectacular radiations of flowering plants. However, their origin, spread across the globe, and hotspots of speciation remain uncertain due to the lack of an up-to-date phylogeographic analysis. We present a new Orchidaceae phylogeny based on combined high-throughput and Sanger sequencing data, covering all five subfamilies, 17/22 tribes, 40/49 subtribes, 285/736 genera, and c. 7% (1921) of the 29 524 accepted species, and use it to infer geographic range evolution, diversity, and speciation patterns by adding curated geographical distributions from the World Checklist of Vascular Plants. The orchids' most recent common ancestor is inferred to have lived in Late Cretaceous Laurasia. The modern range of Apostasioideae, which comprises two genera with 16 species from India to northern Australia, is interpreted as relictual, similar to that of numerous other groups that went extinct at higher latitudes following the global climate cooling during the Oligocene. Despite their ancient origin, modern orchid species diversity mainly originated over the last 5 Ma, with the highest speciation rates in Panama and Costa Rica. These results alter our understanding of the geographic origin of orchids, previously proposed as Australian, and pinpoint Central America as a region of recent, explosive speciation.

Larvicidal effect of Clinopodium macrostemum essential oil extracted by microwave-assisted hydrodistillation against Culex quinquefasciatus (Diptera: Culicidae).

INTRODUCTION: In the present study, we determined the chemical composition of Clinopodium macrostemum essential oil obtained by microwave-assisted hydrodistillation and its effect on the growth and development of Culex quinquefasciatus mosquito larvae. METHODS: The essential oil compounds were identified by gas chromatography-mass spectrometry analysis, and bioassays were conducted to evaluate the influence on the developmental stages of early second instar larvae of Cx. quinquefasciatus until the emergence of adults, using essential oil concentrations of 50, 100, 200, 400, and 800mg/L. RESULTS: The gas chromatography-mass spectrometry analyses revealed that the leaf essential oil of C. macrostemum contained 32 compounds and the major chemical compounds identified were linalool (55.4%), nerol (6.4%), caryophyllene (6.25%), menthone (5.8%), geraniol acetate (4.1%), terpineol (3.7%), and pulegone (2.8%). The essential oil yield obtained by microwave-assisted hydrodistillation was 0.8% at 20 min. The treatments showed lethal concentrations (LC50 and LC90) of 22.49 and 833.35mg/L, respectively, after the final measurement of the total number of dead larvae (second, third, and fourth instars), and LC50 and LC90 of 6.62 and 693.35mg/L, respectively, at the end of the experimental period. The essential oil inhibited the growth and development of the mosquito larvae by 32% (relative growth index = 0.68) at 50mg/L, and up to 47% (relative growth index = 0.53) at 800mg/L. CONCLUSION: The present study demonstrated the larvicidal effect of C. macrostemum essential oil on Cx. quinquefasciatus, which can be attributed to the oxygenate compounds obtained by the extraction method.

Larvicidal effect of Clinopodium macrostemum essential oil extracted by microwave-assisted hydrodistillation against Culex quinquefasciatus (Diptera: Culicidae)

Abstract INTRODUCTION: In the present study, we determined the chemical composition of Clinopodium macrostemum essential oil obtained by microwave-assisted hydrodistillation and its effect on the growth and development of Culex quinquefasciatus mosquito larvae. METHODS: The essential oil compounds were identified by gas chromatography-mass spectrometry analysis, and bioassays were conducted to evaluate the influence on the developmental stages of early second instar larvae of Cx. quinquefasciatus until the emergence of adults, using essential oil concentrations of 50, 100, 200, 400, and 800mg/L. RESULTS: The gas chromatography-mass spectrometry analyses revealed that the leaf essential oil of C. macrostemum contained 32 compounds and the major chemical compounds identified were linalool (55.4%), nerol (6.4%), caryophyllene (6.25%), menthone (5.8%), geraniol acetate (4.1%), terpineol (3.7%), and pulegone (2.8%). The essential oil yield obtained by microwave-assisted hydrodistillation was 0.8% at 20 min. The treatments showed lethal concentrations (LC50 and LC90) of 22.49 and 833.35mg/L, respectively, after the final measurement of the total number of dead larvae (second, third, and fourth instars), and LC50 and LC90 of 6.62 and 693.35mg/L, respectively, at the end of the experimental period. The essential oil inhibited the growth and development of the mosquito larvae by 32% (relative growth index = 0.68) at 50mg/L, and up to 47% (relative growth index = 0.53) at 800mg/L. CONCLUSION: The present study demonstrated the larvicidal effect of C. macrostemum essential oil on Cx. quinquefasciatus, which can be attributed to the oxygenate compounds obtained by the extraction method.

Stelis zootrophionoides (Orchidaceae: Pleurothallidinae), a new species from Mexico.

BACKGROUND: Stelis (Orchidaceae) encompasses approximately 1100 species of epiphytic orchids distributed throughout the Neotropics, with the highest diversity in Andean South America. Sixty-two species were recorded previously in Mexico. METHODS: We formally describe here Stelis zootrophionoides as a new species from Chiapas, Mexico. To determine its systematic position, we conducted a morphological comparison with other members of Pleurothallidinae and a phylogenetic analysis of nucleotide sequences from the plastid matK/trnK and trnL/trnF regions, as well as the nuclear ribosomal ITS region for 52 species of Pleurothallidinae. Sequences of 49 species were downloaded from GenBank and those of three species, including the new taxon, were newly generated for this work. The new species is described and illustrated; notes on its ecological preferences and a comparison with closely related species are presented. CONCLUSIONS: The new species, known only from one location and apparently restricted to the cloud forest in the central highlands of Chiapas, Mexico, is considered a rare species. This small epiphyte is unique among the Mexican species of Stelis by the combination of dark purple flowers with the distal third of the dorsal sepal adhered to the apices of the lateral sepals, which are partially united into a bifid synsepal, leaving two lateral window-like openings, and sagittate labellum. Stelis jalapensis, known from southern Mexico and Guatemala, also has the apices of the sepals adhered to each other, but it is distinguished by its larger flowers with lanceolate, acute dorsal sepal, completely fused lateral sepals (i.e. the synsepal is not bifid), and oblong-elliptic labellum. The phylogenetic analysis shows that S. zootrophionoides is closely related to other Mexican Stelis and corroborates previous suggestions that fused sepal apices have arisen independently in different lineages of Pleurothallidinae.