Multivariate Analysis of Leaf Shape Patterns in Asian Species of The

Blackwell Science, LtdOxford, UKBOJBotanical Journal of the Linnean Society0024-4074The Linnean Society of London, 2003? 2003 1433 231242 Original Article LEAF SHAPE ANALYSIS IN ASIAN UVARIA C. MEADE and J. PARNELL Botanical Journal of the Linnean Society, 2003, 143, 231–242. With 5 figures Multivariate analysis of leaf shape patterns in Asian species of the Uvaria group (Annonaceae) Downloaded from https://academic.oup.com/botlinnean/article-abstract/143/3/231/2433588 by Maynooth University user on 05 July 2019 CONOR MEADE1,2* and JOHN PARNELL1 1Department of Botany, Trinity College Dublin, Ireland 2Institute of Bioengineering and Agroecology, National University of Ireland, Maynooth, Co. Kildare, Ireland Received November 2002; accepted for publication July 2003 Multivariate analysis of leaf radian measurements was used to investigate variation in leaf shape among 34 Asian species of the Uvaria group, a large palaeotropical group of climbing Annonaceae characterized by imbricate petals and stellate hairs. Raw data were normalized by conversion into 15 ratio characters and using the log10 transformation. All species surveyed showed a unique leaf-shape ‘bauplan’. The ratio character with the greatest discrimi- nating power in both the Principal Components Analysis and Discriminant Analysis (DA) results was a measure of the shape of the leaf base. Ratio characters with the highest factor loadings for principal components 1 and 2 clearly separated the sampled taxa when plotted against one another and provided support for the retention of several taxa as distinct species or varieties. Classification of cases into taxa using DA yielded a correct classification rate of only 52% for the ratio-transformed data; however, division of taxa in the dataset into smaller subgroups defined by discrete morphological characters significantly increased the accuracy of case identification to between 67 and 100% of cases correctly classified, depending on the group. Case identification using DA on log10-transformed data was higher than for the ratio values in the entire dataset (61.7%) and the larger subgroups. However, the rate of correct case assignment was lower in the smaller groups than for the ratio data. © 2003 The Linnean Society of London, Botan- ical Journal of the Linnean Society, 2003, 143, 231–242. ADDITIONAL KEYWORDS: classification – key – liana – Magnoliales – palaeotropical – systematics – taxonomy – variation. INTRODUCTION Ciofani & Miramontes, 2002). Statistical analysis of this type of data has revealed that it can be a powerful Leaf morphology has always played an important role key for taxonomic differentiation among species, pop- in plant taxonomy, particularly for identifying taxa in ulations and hybrids across a broad systematic and which variation in floral structures is uninformative taxonomic spectrum, e.g. Aceraceae (Jensen et al., (e.g. Quercus spp.) or in which flowering specimens are 2002), Araceae (Ray, 1992), Asteraceae (Hodálová & infrequent owing to, for example, a limited flowering Marhold, 1998), Fagaceae (Jensen et al., 1993), Notho- season (Stace, 1989). However, the relative paucity of fagaceae (Premoli, 1996), and Rosaceae (Parnell & informative leaf characters in many taxa means that Needham, 1998; Rumpunen & Bartish, 2002). often the most effective way to characterize taxonomic Although the analysis of landmark data has become variation is to sample extensively a set of landmarks a popular choice for leaf morphology studies (see or other measures of leaf shape and so generate an Jensen et al., 2002, for a recent review), analysis of accurate numerical representation of the leaf types in leaf measurement data using multivariate techniques each sample (Dickinson, Parker & Strauss, 1987; such as Principal Components Analysis (PCA; Sneath Stace, 1989; Marcus, 1990; Marcus, Bello & García- & Sokal, 1973) is also employed successfully for the Valdecasas, 1993; McLellan & Endler, 1998; Jensen, investigation of taxonomic relationships (e.g. Premoli, 1996; Hodálová & Marhold, 1998; Parnell & Needham, 1998; Clausing, Meyer & Renner, 2000). Canonical *Corresponding author. E-mail: [email protected] Discriminant Analysis (DA) is another powerful mul- © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 143, 231–242 231 232 C. MEADE and J. PARNELL tivariate method, which uses patterns of variation in reclassification of the taxonomic group that emerged multidimensional space as a basis for defining and dis- from the study: a new subspecies was identified tinguishing among taxonomic groups, providing mea- largely using leaf shape characters; and overall four of sures of group coherence and probability of group the ten most important clustering characters were membership for individual cases. Raw data are related to leaf shape, with length-to-width ratio and unsuitable for these parametric analyses when it is the shape of the leaf base being the two most not normally distributed, and a transformation such important. as lnx or log10x is generally used to give the data a nor- The contrasting results of these two studies are ech- mal spread – although any transformation that nor- oed in results presented by Meade et al. (2002), which Downloaded from https://academic.oup.com/botlinnean/article-abstract/143/3/231/2433588 by Maynooth University user on 05 July 2019 malizes the data is in theory acceptable (Sokal & suggest that leaf characters display a high degree of Rohlf, 1981). homoplasy and must be treated with care in any phy- One such transformation is the conversion of raw logenetic analysis (as is the case with a large propor- data into ratios. Some authors have argued that ratios tion of floral and fruit characters in the Annonaceae: in themselves are not reliable summaries of variation van Heusden, 1992; Kessler, 1993; Doyle & Le Tho- because they can compound recording error (Sokal & mas, 1996). At the same time, however, Chatrou (1997) Rohlf, 1981) and do not completely factor out size demonstrates that the morphological variation (Bookstein et al., 1985). However, ratios can conve- present in leaf characters is extremely useful for elu- niently summarize data where, for example, the rela- cidating taxonomic relationships, particularly among tionships between a set of characters and one other closely related taxa. character are of interest over and above the relation- This current work stems from a revision of the ship among all the characters simultaneously, such as Uvaria group in continental Asia (Meade, 2000). is the case when analysing shape patterns that might Uvaria L. is the second largest palaeotropical genus in be of use in taxonomic keys. Furthermore, when the the Annonaceae and includes approximately 150 spe- analysis is complete, ratio characters with a high cor- cies (Kessler, 1993; Meade, 2000). All Uvaria species relation for the major summary axes in PCA can be are climbers and are typically found in lowland per- used to plot cases in a scatter diagram, thereby sepa- humid tropical forest, although certain taxa are com- rating cases along axes that are not too abstract from mon in riverine and montane forest habitats also. The reality, as can be the case with summary axes and, to climbing habit in Uvaria is facilitated by backward an extent, logarithmic transformations. orientated twining branchlets (Fig. 1A), and the genus There have been some investigations of leaf shape in can be readily distinguished from most other Annon- the Annonaceae aside from the general descriptions of aceae by the combined presence of stellate hairs, leaf morphology presented in taxonomic accounts. many-seeded apocarpous fruits and an imbricate peri- Jovet-Ast (1942) and van Setten & Koek-Noorman anth. Several genera share these characters and (1986) studied the general anatomy and venation pat- together these form the Uvaria group: Cyathostemma, terns of annonaceous leaf types, and although taxon Rauwenhoffia, Ellipeiopsis, Ellipeia and Anomianthus identification using leaf morphology is possible based (all in continental Asia), Tetrapetalum (in Malesia), on the findings of this work, both studies were largely and Balonga and Afroguatteria in Africa (van Heus- descriptive and did not include any comparative or den, 1992; van Setten & Koek-Noorman, 1992; statistical analysis of leaf shape. More recent system- Kessler, 1993; Meade, 2000). Ellipeiopsis is unique in atic work by van Zuilen, Koek-Noorman & Maas the group in having an exclusively shrubby habit. (1995) and Chatrou (1997) have included a more rig- Presently there is a reliable array of discrete char- orous analysis of leaf morphology – the first covering a acter differences that can be used to differentiate phylogenetic investigation of 60 species of the neotro- between taxa in the Uvaria group; however, a common pical genus Duguetia, the latter focusing on four spe- problem (as with Annonaceae material in general) is cies of Malmea in Central America. Although both of that a large number of duplicate sterile sheets are cre- these latter studies used clustering algorithms to dif- ated for each flowering or fruiting specimen, leading to ferentiate among samples, the categorical scoring a situation in which many herbaria have sterile dupli- used for all characters in the Duguetia analysis was cates received on exchange. In the absence of adequate unsuccessful and yielded a poorly resolved phylogeny labelling or an updated collectors’ database, most of as a result (with a consistency index score of 0.112). these specimens cannot be

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