Review Article |
Corresponding author: Michael D. Pirie ( michael.pirie@uib.no ) Academic editor: Anina Coetzee
© 2024 E. Charles Nelson, Michael D. Pirie, Dirk U. Bellstedt.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Nelson EC, Pirie MD, Bellstedt DU (2024) Redefining the megagenus Erica L. (Ericaceae): the contributions of E. G. H. Oliver and I. M. Oliver (née Nitzsche) to taxonomy and nomenclature. PhytoKeys 244: 39-55. https://doi.org/10.3897/phytokeys.244.121705
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The megagenus Erica L. (Ericaceae), as it is recognised today, includes 851 species of evergreen shrubs or small trees, the majority of which are endemic to the Cape Floristic Region of South Africa. From the first descriptions in Linnaeus’s Genera plantarum, a succession of authors ascribed the steadily accumulating numbers of known species to various of a total of 72 different genera. Until the latter half of the twentieth century, so called ‘minor genera’ such as Philippia Klotzsch and Blaeria L. were still recognised for many African species. The now uncontroversial inclusive circumscription of Erica, and a substantial proportion of its currently recognised species diversity, was conceptualised, described, and illustrated by the South African botanists E. G. H. (‘Ted’) Oliver and Inge M. Oliver in a succession of works published from 1964 to the present day. We review the historical development of generic delimitation in Erica sens. lat., focusing on the contribution of the Olivers to the current state of systematic knowledge of the genus, and presenting an overview and complete lists of literature and of taxa that they authored.
Ericoideae, nomenclature, taxonomy
Erica L. (subfamily Ericoideae, family Ericaceae), as understood today, is one of the largest genera in the Angiospermae. World Flora Online (WFO; www.wfo.org) currently recognizes 851 included species (https://wfoplantlist.org/taxon/wfo-4000013772-2024-06;
The taxonomic and nomenclatural history of Erica is complicated. Carl Linnaeus’s Genera plantarum (
In the first edition of Species plantarum Linnaeus described and named only 23 species of Erica. His artificial method of classification led him to nest the widespread, northern-hemisphere shrubby Calluna vulgaris L. within Erica (as Erica vulgaris L.:
Vegetatively, Erica species (commonly called heaths or heathers) are relatively similar, being shrubs or less frequently small trees with small, evergreen, linear-oblong (‘needle-like’) leaves arranged in whorls. The leaves often have revolute margins that can touch on the underside – this general type of leaf morphology is termed ‘ericoid’. As the individual taxa are so similar in foliage, taxonomists, since Linnaeus’s time, have traditionally relied on floral characteristics to demarcate subgeneric taxa and distinguish between species, rather than foliage morphology (for example, see
The eighteenth-century and nineteenth-century botanists who worked to identify, name, and describe Erica sens. lat. species and who attempted to subdivide the numerous species into discrete genera were almost all based in Europe. A few had travelled and collected in Africa. Thus, most of their work entailed examining a relatively small number of pressed and dried specimens. Access to living material was largely limited to the species indigenous in the northern hemisphere, and to the relatively small number of cultivated plants maintained in European gardens. While there was a ‘mania’ for cultivating southern African Erica (the so-called ‘Cape heaths’) particularly during the first part of the nineteenth century (
The only universal treatment available before 1900 was George Bentham’s contribution to the seventh volume of "Agustin Pyramus de Candolle’s Prodromus systematis naturalis regni vegetabilis" published in 1839 (
Edward (‘Ted’) George Hudson Oliver became fascinated by the diversity of Cape flora and especially fynbos vegetation after he enrolled as an undergraduate, to study zoology, at the University of Cape Town in the late 1950s. His attention was soon diverted from animals, and he became ‘obsessed’ by the Cape heaths because ‘they were small and delicate with a seemingly infinite variety of shapes and colours’ (
Erica oliveri H.A. Baker, drawn by E. G. H. Oliver (
Following graduation, he undertook a study of Acrostemon, one of the ‘minor’ genera, presenting his Master’s thesis in October 1964. In this (
The relationship of [Stokoeanthus] appears to me to be with Erica and Blaeria and to some extent with Eremia, but it does not fit into any of them as presently constituted. From Erica it differs in having 4 stamens and a 2-celled ovary, from Blaeria in having 2 cells to the ovary and from Eremia in having 4 stamens and more than 1 ovule per cell. To change the generic limits of any of these genera to force the inclusion of the new taxon would, in my opinion, be impracticable and would cause repercussions in the relationships of and differences between many other genera of the Ericoideae.
Thus, Ted laid down the basis for the work that consumed his time for the next 35 years, culminating in the elimination of all the ‘minor genera’ (
From about 1974, Oliver was assisted in his work on Erica, especially the ‘minor genera’, by Inge Magdalene Nitzsche (1947–2003), who had studied botany and zoology at the University of Cape Town (1967–1969) and also had a diploma in fine arts (1971–1972). They married in February 1974. Inge’s remarkable pen-and-ink drawings of anatomical and morphological details of the species (often not signed) were to be an integral component of papers about Erica (and the ‘minor genera’) published from 1976 onwards: early (unsigned) examples of Inge Oliver’s extraordinary illustrations were published in the paper ‘revising’ Eremia and Eremiella (
In 1988, a grant enabled Inge to be employed as research assistant in the BRI Herbarium at the University of Stellenbosch ‘to help with all the technical work – the numerous dissections, drawings and recording of all the details of variations in the plants. This … helped tremendously with the research and … Inge’s work also helped with the finalisation of the analvses of the minor ericaceous genera …’ (
Ericas of the Cape Peninsula by Inge and Ted Oliver (2000, published by the Protea Atlas Project, National Botanical Institute, Cape Town); left (cover: 106 × 148mm): E. mammosa, pen-and-ink drawing by Inge Oliver: text page and accompanying illustrations by Inge Oliver, showing E. paniculata and “E. tenuis” (now E. oliveranthus E.C.Nelson & Pirie;
Having come into contact with Colonel H. A. Baker by the early 1960s, Ted Oliver became co-author with Baker of "Ericas of South Africa" (
Writing for The Heather Society (of which he was an honorary member) in 2000, Ted noted that:
"Having begun work on the Ericaceae some 40 years ago as a student, I now find that I am getting to know the group properly, the more so recently because of the rapidly increased knowledge that Inge has also acquired. I am no longer a single person struggling in a “sea of ericas”. There are now two of us to discuss the problems of species de-limitation, species evolution and the phylogeny, ecology or phytogeography of this fascinating genus. There are quite a number of new species to be described and surprisingly, other un-described species are still being brought in. The biggest problem ahead is that of sub-generic classification. The new techniques of DNA analysis will help to throw some light on this problem, which is now being tackled by a group of international experts with material that I am supplying for them."
In Table
Milestones in the careers of E. G. H. Oliver and I. M. Oliver, relating to their studies, separately and jointly, of the megagenus Erica (1937–2024).
E. G. H. (“Ted”) Oliver | Inge Magdalene Oliver (née Nitzsche) | |
---|---|---|
1938– | 1947–2003 | |
1959 | undergraduate, University of Cape Town (–1962) | |
1962 | commences Masters degree, in Bolus Herbarium; H. A. Baker describes and names Erica oliveri | |
1964 | submitted Masters thesis "Taxonomic studies in the genus Acrostemon Kl. and related genera"; M.Sc. awarded | |
Curator, Government Herbarium, University of Stellenbosch | ||
1967 | "Erica of South Africa" published; co-author Colonel Hugh A. Baker | undergraduate, University of Cape Town (–1969) |
1967 | South African Botanical Liaison Officer, Royal Botanic Gardens, Kew, UK | |
1970 | returned to herbarium, University of Stellenbosch | |
1971 | commenced Fine Arts diploma | |
1972: December | elected honorary member of The Heather Society | |
1974: February | marriage | |
1975 | Head of Herbarium Services and Curator National Herbarium, Pretoria | |
1976 | first illustrations (unsigned) of Erica published in E. G. H. Oliver, ‘Studies in the Ericoideae. I. The genera Eremia and Eremiella’, Bothalia 12 (1). | |
1981 | returns to Government Herbarium, University of Stellenbosch | |
1988 | research assistant at herbarium, University of Stellenbosch | |
1991 | Erica ingeana named and described in earliest co-authored research paper (‘Studies in the Ericoideae (Ericaceae). VIII. New species in Erica, section Pseuderemia, from southern Africa’. Bothalia 21 (2)) | |
1992 | "Ericas of South Africa": published; co-authors Dolf Schumann and Gerhard Kirsten | |
1999 | submits doctoral thesis ‘Systematic studies in the Tribe Ericeae (Ericaceae–Ericoideae)’ | |
2000 | Ph.D. awarded; monograph (Systematics of Ericeae (Ericaceae: Ericoideae) species with indehiscent and partially dehiscent fruits. "Contributions from the Bolus Herbarium" no. 19) published; contained 84 full-page illustrations by Inge M. Oliver | "Field guide to the Ericas of the Cape Peninsula" published; 104 species illustrated |
2003: July | deceased | |
2010 | visited Madagascar (with group including DUB & MDP; Heathers 8: 47–54. 2011) | |
2012 | Genus Erica An identification aid version 3.00 published (Contributions from the Bolus Herbarium 22); co-author Nigel Forshaw [version 4.00 published 2024] | |
2014 | visited Mauritius (Heathers 11: 38–42. 2014) |
Although big plant genera have expanded and contracted over time (
One example, Philippia Klotzsch, was characterised largely by reduced flowers without brightly coloured corollas or nectaries, but with greatly expanded stigmas (as illustrated in
Blaeria L., had been defined as including those species with four, rather than eight, stamens (
With the megagenus concept already firmly embedded, the Olivers set out to revise systematically groups of species following the arrangement in "Flora Capensis" (
By the end of the twentieth century, following almost 250 years of botanical exploration especially in the Cape Floristic Region of South Africa, the number of species of heaths and heathers known to botanists had exceeded eight hundred (
Erica amalophylla | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica annalis | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica cavartica | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica ceraria | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica croceovirens | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica gerhardii | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica hebdomadalis | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica jananthus | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica jugicola | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica lithophila | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica petrusiana | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica prolata | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica psittacina | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica schelpeorum | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica umbratica | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
Erica viridimontana | E.G.H.Oliv. & I.M.Oliv. | wfo-4000013772 |
No single author has had greater impact on the taxonomy of Erica/Ericeae than Ted Oliver in numbers of new species (as predicted by his mentor, H. A. Baker, in 1962), but this contribution must be interpreted as part of a team effort of two enormously talented botanists. Their combined contribution both of improved knowledge of alpha taxonomy and of broad understanding of the structure of that diversity is fundamental to, and will have a lasting influence on, all future developments in the field.
We thank Alan Elliott for help with summarising data from WFO, Tessa Oliver for consultation, and Benny Bytebier and Regine Claßen-Bockhoff for constructive and positive reviews.
The authors have declared that no competing interests exist.
No ethical statement was reported.
No funding was reported.
ECN: Writing – Original draft, Writing – Review and Editing. MDP: Writing – Review and Editing. DUB: Writing – Review and Editing.
E. Charles Nelson https://orcid.org/0000-0002-3909-4388
Michael D. Pirie https://orcid.org/0000-0003-0403-4470
Dirk U. Bellstedt https://orcid.org/0000-0002-6376-4855
All of the data that support the findings of this study are available in the main text or Supplementary Information.
Generic description of Erica by E. G. H.
Data type: docx
A complete list of Erica s.l. taxa at all ranks authored by E.G.H. Oliver and I.M. Oliver
Data type: xlsx
Explanation note: Including taxa new to science, replacement names, and new combinations, with synonymy and bibliographic data, derived from the World Flora Online (
A complete list of Erica related publications authored by E.G.H. Oliver and I.M. Oliver
Data type: docx