Abstract

Cyanotis is the third largest genus of Commelinaceae in Africa, with approximately 25 species. The genus is widespread outside of forested habitats, occurring often in dry habitats, but it also includes an aquatic species. Using morphological and anatomical differences, Cyanotis sp. nov, a new perennial African species, is described from tropical Africa. Plants differ from the similar species C. foecunda and C. nyctitropa in lacking a distinct base, having solely axillary inflorescences, and in the shape of the terminal swelling of the style. Two distinct subspecies are recognized, C. sp. nov. and C. sp. nov. subsp. nov, based on geographic and cytological evidence.

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Introduction

The Commelinaceae (spiderworts, dayflowers, and wandering Jews) is a family of monocots comprising approximately 41 genera and 650 species (Faden 1998.) The family occurs worldwide, but it is most diverse in the tropics. The greatest diversity is in Africa, where more then 270 species representing 17 genera (Faden 1983) are native. The genus Cyanotis contains approximately 50 species in the Old World with about 25 species occurring in Africa (Faden 1983, Faden 1998). Cyanotis species are generally succulent perennials with fleshy leaves or occasionally annuals. The small blue to violet flowers have the petals united into a tube and 6 equal, densely bearded stamens. Species of Cyanotis occur mainly in dry habitats, and some species exhibit underground storage organs (Faden 2001).

Three African and Arabian Peninsular species (C. sp. nov., C. foecunda, and C. nyctitropa) form a natural group. They share an unusual basic chromosome number of x=13 as well as a glabrous style. Historically there has been confusion among the three species in the herbarium. This project hopes to characterize what has previously been called Cyanotis sp. A., to describe it as a new species, and to contrast it with the other two species. Morphological and anatomical characteristics will be studied to look for patterns of variation and species distinct traits.

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Methods and Materials

Plant material was collected from specimens of C. sp. nov., C. sp nov. subsp. nov, C. foecunda, and C. nyctitropa growing at the Smithsonian Institution Botany Research Greenhouse. Fresh flowers were examined uncoated with a Philips XL30 ESEM (Environmental Scanning Electron Microscope). Additional flowers were preserved in 70% FAA (formyl-acetic acid) for later study. Leaves were fixed in 50% FPA (formyl-propionic acid). Leaf material was prepared for study using epidermal scrapes, wholemount clearings, and sectioning of paraffin embedded material. Slides were examined for distinctive anatomical characteristics. Herbarium specimens for study were prepared from living plant material. Specimens from the U.S. National Herbarium were also studied. Root tips were collected at the S.I. Botany Research Greenhouse for mitotic chromosome counts using the methods of Faden and Suda (1980) slightly modified according to Suda and Faden (1991). Measurements of preserved flowers and dried seeds were made from field collected and cultivated specimens. A distribution map was prepared from all known collections of Cyanotis sp. nov.

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Results

Cyanotis sp. nov. was recognized as a distinct species and was compared and contrasted with the related species C. foecunda and C. nyctitropa. C. sp. nov. lacks a definite base and has only axillary inflorescences whereas Cyanotis foecunda and C. nyctitropa both have a definite base and have both axillary and terminal inflorescences. Cyanotis nyctitropa seeds differ from those of the other two species in lacking transverse grooves. Cyanotis sp. nov. was divided into two subspecies, based on geographic range (figure 5) as well as cytological differences. Cyanotis sp. nov. is described from eastern Kenya and Tanzania and is diploid (2n=26) (Faden and Suda 1980). Cyanotis sp. nov. subsp. nov. ranges from western Kenya across the Congo forest to Gabon. Counts have been tetraploid (2n=52) and hexaploid (2n=78) (Faden and Suda 1980).

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Discussion

Cyanotis sp. nov is morphologically very similar to African C. foecunda and Arabian Peninsular C. nyctitropa. In this region they uniquely share characteristics of a glabrous style and a basic chromosome of x=13. The morphological differences outlined in the results, were considered sufficient to separate the species. Cyanotis sp. nov. subsp. nov. has been in horticulture for many years under the name “Cyanotis somaliensis.” True C. somaliensis, from northern Somalia, may be a synonym of C. nyctitropa, which differs from the plant in cultivation by having a definite base and terminal and axillary inflorescences, whereas C. sp. nov. lacks a definite base and has solely axillary inflorescences.

Cytology can provide some insight into the distinction between the species. Counts by Faden and Suda (1980) provide us with a distinction between C. sp. nov. and C. sp. nov. subsp nov, with the typical subspecies (listed as Cyanotis sp. ‘A’) being a diploid (2n=26) and subspecies sp. nov. (listed as Cyanotis sp. ‘B’) being a hexaploid (2n=78). Unpublished chromosome counts (Faden, personal communication) from three additional collections of the typical subspecies from Kenya were also diploid, whereas a population of subspecies robusta from southwestern Kenya was tetraploid (2n=52). A single, approximate mitotic chromosome count for another collection of C. sp. nov. subsp. nov. (Climatron, Missouri Botanical Garden), obtained in this study, was 2n= ca. 76, which would suggest a hexaploid. All published and unpublished counts by Faden (personal communication) of C. foecunda and C. nyctitropa were diploid (2n=26).

Geographic separation occurs in Cyanotis sp. nov., with the two subspecies being isolated, with the exception of a single collection from Uganda (Lind 345). This collection is morphologically similar to that of the typical subspecies, but it is widely separated from the other populations of this subspecies occurring just outside the range of subspecies nov. This collection is also from the highest recorded elevation for the typical subspecies. It may represent a relict of a once broader distribution of this subspecies.

Distribution of Cyanotis sp. nov. (triangles) and Cyanotis sp. nov. subsp. nov. (squares).

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Acknowledgments

This project was completed as part of the 2002 Research Training program at the National Museum of Natural History, Smithsonian Institution. This research was supported by a grant from the National Science Foundation Research Experiences for Undergraduates program, Award Number DBI-9820303. I thank Stanley Yankowski for assistance in the laboratory, Scott Whittaker for help in the SEM laboratory, Dan Cole for help with the distribution map and Alice Tangerini for the drawings of the specimen.

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Works Cited

Faden, R. B. 1983. Phytogeography of African Commelinaceae. Bothalia 14: 553-557.

----. 1998. Commelinaceae. Pp. 109-128 in The Families and Genera of Vascular Plants, vol. 4, ed K. Kubitzki. Springer: Berlin.

----. 2001. The Commelinaceae of Northeast Tropical Africa (Eritrea, Ethiopia, Djibouti, Somalia, and Kenya): diversity and phytogeography. In I. Friis and O. Ryding (eds.), Biodiversity Research in the Horn of Africa Region. Proceedings of the third International Symposium on the Flora of Ethiopia and Eritrea at the Carlsberg Academy, Copenhagen, August 25-27, 1999. Biologiske Skrifter 54: 213-231.

---- and Y. Suda. 1980. Cytotaxonomy of Commelinaceae; chromosome numbers of some African and Asiatic species. Botanical Journal of the Linnean Society 81: 301-325.

Suda, Y. and R.B. Faden 1991. A modified McClintock method for making temporary slides permanent. The Science Reports of the Tohoku University, Fourth Series, Biology 40(1): 39-45.

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