COMPARATIVE EXTERNAL MORPHOLOGY IN THE GENUS CROTALARIA L. IN JOS, NIGERIA USING NUMERICAL TAXONOMY. *Agyeno, O. E. and Azzuwut, P. A.

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1 COMPARATIVE EXTERNAL MORPHOLOGY IN THE GENUS CROTALARIA L. IN JOS, NIGERIA USING NUMERICAL TAXONOMY *Agyeno, O. E. and Azzuwut, P. A. *Department of Plant Science and Technology, University of Jos, Nigeria. Received 1 st June, 2014; accepted 19 th October, 2014 ABSTRACT Numerical methods were used to undertake a comparative study of 37 exo-morphological characters in 11 species of Crotalaria L. The study was aimed at assessing their relevance in the identification and classification of the species. The study was carried out in situ and ex situ through random sampling. Qualitative morphological characters such as leaf type, leaf apices and habit were discrete while the others were continuous. Highly significant differences (P<0.01) were recorded for most quantitative characters studied, suggesting that there were overlapping similarities across species. Cluster analysis separates dendrogram into two clades at 68% similarity. The highest percentage similarity was between C. goreensis and C. anagyroides (86%) while the lowest was recorded between C. lugardiorum and C. mucronata (46%). Ordination method revealed associative contrast since C. senegalensis and C. incana that were not clustered closely have now been located close to each other in space. It may be concluded that cluster analysis can fail to delimit some taxa in a precise manner. Keywords: Numerical taxonomy, Crotalaria, Exo-morpology, Characters. INTRODUCTION The genus Crotalaria belongs to the sub-family Papilionoideae and family Leguminosae (now Fabaceae). In Nigeria, the genus contains fifty one species (Hutchinson et al., 1958) and worldwide, Crotalaria includes 1,415 scientific plant names of species rank and of this number 698 are accepted species names (Polhill, 1968, 1981a). Members of Crotalaria range in habit from small shrubs to under-shrubs or herbs, erect or prostrate, easily recognized by its yellow flowers (but whitish to purplish or bluish flowers also occur) and its inflated pods with simple, unifoliate or digitately (3-7) foliate leaves. Stamens are monadelphous with the sheath split at least at the very base, dimorphic anthers and inflated legumes. Sustainable crop production is achieved through the management of soil fertility and cover crops play a key role in soil fertility through a reduction in synthetic nutrients applied. Legumes are effective in the fixation of nitrogen and can accumulate large amounts of biomass that help to increase the nutrient availability and organic matter in the soil. Some of the long term benefits obtained from the use of cover crops include weed suppression through competition or allelopathy and possible insect control (Phatak et al., 2002). While some species of Crotalaria are poisonous, others like C. retusa, C. micronata, C. falcate and C. vogelii remain some of the important fodder plants for cattle and small ruminants. The need to ascertain the Nigerian species of Crotalaria that may serve these and many other purposes cannot be overemphasized (Cook and White, 1996). Cardoso et al. (2013) studied the phylogenetic relationships in the Papilionoideae and concluded that link between Crotalaria and Genisteae were never absolutely certain and suggested that

2 Crotalaria was a direct ancestor of Lupinus whereas Polhill (1981a) had considered Crotalaria and Lupinus as distinct evolutionary lines albeit with many parallels in distribution and biology. The numerical evaluation of the similarity between groups of organisms and the ordering of these groups into higher ranking taxa on the basis of these similarities has proven useful in delimiting several angiospermic genera including Solanum and Oryza. Also, several angiospermic taxa have been reclassified using numerical methods (El-Gazzar, 2008). The phenological information given by Hussaini and Iwo (1992), who have worked extensively on the genus, were treated using conventional taxonomic methods. The specific objective of this research was to apply phenetic and taximetric methods in predicting relationships between species encountered. MATERIALS AND METHODS Climate and physical features of the study area The higher altitude of Plateau State has a near temperate climate with an average temperature of between 18 and 22 o C. The mean annual rainfall varies from cm in the southern part to 146 cm on the Plateau. The Jos Plateau is believed to be an area of younger granite which was introduced through an area of old granite rock, making up the surrounding States. These younger granites formed the unusual scenery of the Jos Plateau due to volcanic activity which occurred several million years ago. The elevated nature of this region makes it the source of many rivers in northern Nigeria including the Kaduna, Gongola, Hadeija and Yobe Rivers (Adegbola and Onayinka, 1976). Collection of specimens Field trips were made to selected locations within Jos-North, Jos-South and Jos-East Local Government Areas to collect samples through random sampling (Figs. 1-3). The freshly collected specimens were examined using naked eye and hand lens to derive 37 quantitative and qualitative characters. The following species were finally distinguished and taken to the Herbarium of the University of Jos for comparison with preserved materials. DISCUSSION Exo-morphological characters have been extensively used for constructing classifications (Agyeno et al., 2014). Observed and recorded character states of vegetative and floral parts have been utilized by Jayeola (2001) in the numerical evaluation of similarities among taxa. Although some of these characters such as pigmentation could show plasticity, their traditional natures have made them indispensible to the taxonomist. Characters such as leaf type, apex, stem colour, habit and life span as observed in this research must have played important roles in delimiting members of this genus due to their discontinuity or discreteness. Raj et al. (2011) highlighted

3 habit, leaf type, presence and type of stipule as well as corolla colour as phylogenetically important qualitative characters in this genus; they also attributed the same importance to quantitative characters such as pod length and seed number, petiole length and size of stipules. Originally, the genus Crotalaria was divided into 2 groups based on whether members are simple- leaved or 3-foliate and digitately leaved (Shweta Subramaniam, 2013). Later researchers considered other characters such as petiole length, presence or absence of petiole and their sizes. The results in this research have shed light on interspecific relationship in the genus Crotalaria. The range of variation in the characters of leaf, stem and corolla colour observed in this research could be as a result of the effect of seasonal changes and the environment which could result in marked variations particularly in the overlapping quantitative characters. In predicting a phylogeny, all the Crotalaria species studied may be said to be primitive due to the following characters: being terrestrial in habitat, flowers with petals, chlorophyll present and tropical habitat, or, advanced species due to absence of stipule, small seeds, biennial or annual habit. Based on woody habit, C. anthyllopsis, C. atrorubens, C. mucronata, C. goreensis, C. palida, C. retusa and C. senegalensis are primitive while C. hyssopifolia, C. incana, C. lugardiorum and C. anagyriodes are advanced. C. atrorubens and C. hyssopifolia may be exploited as green manure since they produced more vegetative parts and seeds (Tumuhairwe et al., 2007). A graphical summary of the levels of closeness as depicted by the dendrogram and distance between species reveals interesting contrast in terms of the relationship between the species. Majority of the species studied are embedded within the 81% and 84% phenon lines. This is an indication of a weak clear-cut boundary in the circumcscription of sampled Crotalaria species. This is amply shown by the dendrogram of relationship among taxa studied. Phenon lines show clustering of species based on similarities at different levels of relationship. The interesting contrast here is that species such as C. anagyroides and C. goreensis which were clustered closely have now been located far apart in space when polar ordination method was applied. This means that although cluster analysis indicates how close this species were to each other, it has failed to delimit the species in a precise manner. The polar ordination method placed the species in space and indicates the position they specifically occupy in relation to each other (Rolf, 1972). Thus, cluster analysis and ordination method maybe applied simultaneously so as to complement each other to give a credible classification. Conclusion and recommendation The results of this study have clearly brought to the fore the importance of taximetrics in resolving upscale relationship between members of a taxon. The classification obtained through numerical taxonomy may be said to provide more information than conventional method of taxonomy since it treats all characters with equal weightage. However, a comprehensive study involving more species of Crotalaria is necessary so as to obtain a more credible and satisfactory classification. Molecular and anatomical studies involving chromosome count and composition of the epidermis, respectively, are recommended to support the exo-morphological characters used in this research.

4 REFERENCES Adegbola, A.A. and Onayinka, A.O. (1976). A review of range management problems in the southern guinea and derived savannah zones of Nigeria. Tropical Grassland, 10 (1): Agyeno O.E, Jayeola, A.A, Ajala., B.A. and Blessing J. Mamman. (2014). Exo- Morphology of Vegetative Parts Support the Combination of Solenostemon rotundifolius (Poir) J.K. Morton with Plectranthus esculentus N.E. Br. Natal (Lamiaceae) with insight into Infra specific variability. AAB Bioflux, 6 (1): Cardoso, D., Penington de Queiroz, R.T., Boatwright, L.P., Van Wyk, J.S., Wojciechowski, B.E. and Larvin, M.F.M. (2013). Reconstructing the deep branching relationship of the Papilioned legumes. South African Journal of Botany, 89: Cook, C.G. and White, G.A. (1996), Crotalaria juncea: A Potential Multi-Purpose Fiber Crop. In:Janick (ed), Progress in New Crops. ASHS Press, Arlington, VA. pp El-Gazzar, A. (2008). Taxonomic assessment of five numerical methods and its implication on the classification of Hyptis suaveolens Linn (Labiatae). Alabama Journal of Botany, 2: Hussaini, S.W.H. and Iwo, G.A. (1992). Cytomorphological studies of some weedy species of the Family Leguminosae from Jos Plateau, Nigeria. Feddes Repertorium, 101 (1 2): Hutchinson J., Dalziel, J.M. and Keay, R.W.J. (1958). Flora of West Tropical Africa. Crown Agents for Oversea Government and Administration, Millbank, London, S.W.I. Vol. 1, Part 2: Jayeola, A. A. (2001). Effects of numerical methods, quantity and composition of characters on the classification of the angrecoid orchids of Nigeria and Cameroun. Nigerian Journal of Ecology, 3: Phatak, S.C., Dozier, J.R., Bateman, A.G., Brunson, K.E. and Martini, N.L. (2002). Cover Crops and Conservation Tillage in Sustainable Vegetable Production. Proceedings 25 th Annual Southern Conservation Tillage Conference for Sustainable Agricultural Aubum, AL June Special Report No. 1. Alabama Agricultural Experiment Station and Aubum University, AL. Polhill, R.M. (1968). Miscellaneous notes on African species of Crotalaria L. Bulletin 22: Kew Polhill, R.M. (1981a). Papilionoidae. In: Advances in Legumes Systematics (R.M. Polhill and P.H. Raven, Eds.), Royal Botanic Garden, Kew, Vol. 1, pp

5 Raj, M. J. L., Britto, S. J., Prabhu, S. and Senthikumar, S. R. (2011). Identification of agronomically valuable species of Crotalaria based on phenetics. Agriculture and Biology Journal of North America, 2: Shweta Subramanian, A.K.P. (2013). Taxonomy and phylogeny of the genus Crotalaria (Fabaceae): An Overview. Acta Biologica Indica, 2(1) Rohlf, F. J. (1972). An empirical comparison of three ordination techniques in numerical taxonomy. Systematic Zoologist, 21: Tumuhairwe, J.B., Rwakaikara-Silver, M.C., Muwanga, S. and Natigo, S. (2007). Screening Legume Green Manure for Climatic Adaptability and Farmer Acceptance in the Semi-Arid Agro-Ecological Zone of Uganda In: Advances in Integrated Soil Fertility Management in Sub Saharan Africa: Challenges and Opportunities pp

Measurements of quantitative characters yield continuous data (value ranges) (Ex: plant height),

Measurements of quantitative characters yield continuous data (value ranges) (Ex: plant height), Taxonomic Evidence- Vegetative Characteristics Character and Character States An aspect of a plant, such as leaf shape or petal color is a character. Each character can have a character state, such as