Contributions towards a new classification of Eugenia L. (Myrtaceae) in Southern Africa

Abstract

This study extends the work on the comparative stem and leaf anatomy of the southern African species of Eugenia presented by the author as an M.Sc. thesis in 1978. Additional sources of potential taxonomic evidence were studied in the light of the new taxonomic framework suggested by the anatomical fmdings. The principal objective was to evaluate the taxonomic significance of various characters as an aid towards a regional revision of this taxonomically difficult genus. Contributions are presented on reproductive biology, foliar leaf organography, morphology and ontogeny of the seed and the structure of the stomata, wood, bark and pollen. The thesis is a compilation of 12 papers published in scientific journals over a period of about seven years. It also contains a synthesis of the principal fmdings, an outline of a proposed new classification of Eugenia in southern Africa with keys to the principal taxa, supplemented by notes on diagnostic characters, synonymy, typification and geographical distribution. Anatomical and morphological data from different sources (especially the frrst-formed stem periderm, bark, stomata, inflorescences, seeds and fruits) provide convincing evidence that Eugenia in southern Africa constitutes a heterogeneous assemblage of two co-ordinate groups of species. Group X seems to be most closely related to the mainly New World species of Eugenia, whereas group Y relates to the Old World genusJossinia OC. (usually reduced to the synonymy of Eugenia). Owing to the lack of comparative data on Eugenia elsewhere, bothsupraspecific groups are provisionally maintained as informal categories. The present study has rendered untenable the inclusive specific circumscriptions recently proposed for Eugenia in southern Africa. In a new classification, 14 species (five new) and five subspecies are proposed for the FSA region, compared to two species and at least six subspecies maintained by White (1977 & 1978). New taxa lacking valid names are provisionally referred to by alphabetical characters. Group X consists of E. capensis (Eckl. & Zeyh.) Sond. with subspp. capensis, gueinzii (Sond.) F. White and A [probably within the concept of subsp. aschersoniana (F. Hoffm.) F. White1 E. natalitia Sond., E. simii Duemmer and E. umtamvunensis VanWyk: Group Y includes E. albanensis Son d., E. erythrophylla Strey, E. pusilla N.E. Br ., E. verdoomiae VanWyk, E. woodii Duemrner with subspp. woodii and A, E. zeyheri (Harv.) Harv., E. zuluensis Duemmer and Eugenia spp. A, B and C. Species diagnoses are mainly based on habit, habitat, geographical distribution, bark structure, foliar leaf organography, type of indumentum, inflorescence structure and floral morphology-particularly the stigma and hypanthium in structural hermaphrodites. Noteworthy findings include the presence of water-stomata, conspicuous lipid bodies in the subsidiary cells, wood with pith flecks (pathological) and prismatic crystals enclosed by a thick lignified sheath, bark with a pseudocortex in group X and two types of phelloid cells. A new term 'anomostaurocytic' is proposed for the stomatal type in the native species. For the first time pollen dimorphism and a pachychalazal seed coat are reported for members of the Myrtaceae. Eugenia in southern Africa displays morphological androdioecy but is functionally dioecious.

Die huidige ondersoek is 'n voortsetting van die vergelykende stingel- en blaaranatomiese werk op die Suider-Afrikaanse Eugenia-spesies wat in 1978 as 'n M.Sc.-verhandeling voorgele is. Bykomende bronne van potensiiHe taksonomiese getuienis is ondersoek in die lig van die nuwe taksonomiese raamwerk wat deur die anatomiese bevindings daargestel is. Die hoofdoelwit was die evaluering van die taksonomiese belangrikheid van verskillende kenmerke as hulpmiddels in 'n plaaslike hersiening van hierdie taksonomies-moelike genus. Bydraes oor veral die voortplantingsbiologie, loofblaarorganografie, saadmorfologie en -ontogenie en struktuur van die stomas, hout, bas en stuifmeel word verskaf. Die proefskrif is uit 12 artikels wat oor 'n tydperk van om trent sewe jaar in wetenskaplike tydskrifte gepubliseer is, saamgestel. Dit bevat ook 'n sintese van die belangrikste bevindings, die raamwerk van 'n voorgestelde nuwe klassifikasie van Eugenia in Suider-Afrika met sleutels tot die belangrikste taksons, aangevul deur aantekeninge oor diagnostiese kenmerke, sinonimie, tipifisering en geografiese verspreiding. Anatomiese en morfologiese gegewens van verskillende bronne (veral die eerste-gevormde stingelperiderm, bas, stomas, bloeiwyses, saad en vrugte) verskaf oortuigende getuienis dat Eugenia in Suider-Afrika 'n heterogene groepering is wat uit twee gelykwaardige spesiegroepe bestaan. Spesiegroep X is skynbaar die naaste verwant aan dieEugeniaspesies van hoofsaaklik die Nuwe Wereld, terwyl groep Y verwantskap met Jossinia DC. (gewoonlik as 'n sinoniem van Eugenia beskou) in die Ou Wereld vertoon. Weens die gebrek aan vergelykende inligting oor Eugenia in ander werelddele, word beide supraspesifieke groepe voorlopig as informele kategoriee gehandhaaf. Die huidige ondersoek maak die omvattende spesie-omgrensings wat onlangs vir Eugenia in Suider-Afrika voorgestel is, onaanvaarbaar. In 'n nuwe klassifikasie word 14 spesies (vyf nuut) en vyf subspesies vir die FSA-gebied voorgestel, teenoor die twee spesies en minstens ses subspesies wat White (1977 & 1978) onderskei. Letters van die alfabet word voorlopig gebruik om na nuwe taksons sonder geldige name te verwys. Groep X bestaan uit E. capensis (Eckl. & Zeyh.) Sond. met subspp. capensis, gueinzii (Sond.) F. White en A [moontlik binne die konsep van subsp. aschersoniana (F. Hoffm.) F. White], E. natalitia Sond., E. simii Duemmer en E. umtamvunensis VanWyk. Groep Y sluit in E. albanensis Son d., E. erythrophylla Strey, E. pusilla N.E. Br., E. verdoomiae VanWyk, E. woodii Duemmer met subspp. woodii en A, E.zeyheri (Harv.)Harv., E.zuluensis DuemmerenEugenia spp. A, Ben C. Spesiediagnoses is hoofsaaklik gebaseer op groeivorm, habitat, geografiese verspreiding, basstruktuur, loofblaarorganografie, indumentum- tipe, bloeiwysestruktuur en blommorfologie-veral die stempel en hipantium van strukturele hermafrodiete. Vermeldingswaardige bevindings sluit in die aanwesigheid van waterstomas, opvallende lipiedliggame in die hulpselle, hout met murgvlekke (patologies) en prismatiese kristalle omsluit deur 'n gelignifiseerde skede, bas met 'n pseudokorteks by groep X en twee tipes felloiedselle. Die nuwe term 'anomostaurosities' word vir die stomatipe van die inheemse spesies voorgestel. Stuifmeeldimorfisme en 'n pagichalasale saadhuid is vir die eerste keer by verteenwoordigers van die Myrtaceae aangeteken. Eugenia in Suider-Afrika vertoon morfologiese andresie maar is eintlik funksioneel tweehuisig.