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New species of Isoglossa; A & B, I. pondoensis, with short inflorescences and round leaves below the inflorescence; C, Type locality of I. gracilenta; D, I. gracilenta, with gracile interrupted inflorescence; E & F, Variation between populations of I. woodii; E, compact young inflorescence of a plant at Ongoye Forest with a markedly fringed bract; F, longer, more mature inflorescence with no fringe of hairs on the bracts of a plant at Beach Road, Umlalazi.
Source publication
The taxonomy of the white-flowered species of Isoglossa Oerst. in southern Africa is reviewed. Morphology and indumentum of bracts and calyces, micromorphology of pollen and seeds, flowering times and distribution are documented. Several names are subsumed: Isoglossa densa N.E.Br. and Isoglossa sylvatica C.B.Clarke under Isoglossa ciliata (Nees) Li...
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Citations
... In the Flora of Tropical East Africa account for Isoglossa, 26 species were documented in Tanzania, of which three were undescribed and poorly known due to incomplete material (Darbyshire et al. 2010). Isoglossa s.l. is noteworthy for including a significant number of narrowly rangerestricted taxa, both in Tanzania and in wider tropical and southern Africa and Madagascar (Brummitt 1985;Darbyshire 2009;Darbyshire et al. 2010Darbyshire et al. , 2011Darbyshire et al. , 2023Balkwill et al. 2017;Champluvier & Fischer 2020). Although the genus occurs in a range of habitats, many of these range-restricted species are endemic to specific mountain ranges. ...
Isoglossa pareensis I.Darbysh. & Hemp (Acanthaceae), from submontane moist forest at Mwala in the South Pare Mountains of northeastern Tanzania, is described and illustrated. This species is considered to be related to I. gregorii (S.Moore) Lindau and I. punctata (Vahl) Brummitt & J.R.I.Wood, which are widespread in the montane forests of eastern Africa, but it clearly differs from these species in inflorescence structure and indumentum and in anther morphology. Notes on the habitat requirements and extinction risk of this new species are provided; it is considered to be Vulnerable under IUCN criterion D2 because of its extremely limited range and a plausible future threat from wildfires. The recent discovery of the Critically Endangered acanthaceous herb Asystasia masaiensis Lindau at lower, drier elevations at the same site is also reported and the first known photograph of that species is reproduced
... Genera of subtribe Isoglossinae (Acanthaceae: Acanthoideae: Justicieae), such as palaeotropical Isoglossa Oerst. and Brachystephanus Nees and neotropical Stenostephanus Nees, are noted to contain a high number of narrowly range-restricted species, with many confined to forest habitats (see, e.g., Daniel 1999;Champluvier & Darbyshire 2009;Darbyshire 2009;Darbyshire et al. 2011;Balkwill et al. 2017;Wood 2019aWood , 2019bChampluvier & Fischer 2020). As a result, many of these species are of high conservation concern, and it is important that the alpha diversity within Isoglossinae is documented and that localendemic species are described in a timely manner in order to help guide conservation planning. ...
Current generic delimitation in subtribe Isoglossinae of Acanthaceae is discussed using available morphological and molecular data. Particular consideration is given to the small genera endemic to Madagascar — Celerina Benoist, Melittacanthus S.Moore, Sphacanthus Benoist and the illegitimate Conocalyx Benoist — and how these relate to the current circumscription of Isoglossa Oerst. The relative merits and challenges of recognising a broadly circumscribed Isoglossa are considered. Isoglossa s.l. is readily recognisable by combining a bilabiate corolla, with an androecium comprising two bithecous stamens and lacking staminodes, and with the presence of gürtelpollen (i.e. bipororate pollen, circular in apertural view and with a pronounced interapertural “girdle” of tectate exine), whilst the segregate genera as currently defined are not separable morphologically. However, the limited molecular phylogenetic data available to date indicate that Isoglossa s.l. is paraphyletic. Pending further molecular studies of this group to clarify generic delimitation, it is proposed that all new taxa in bithecous Isoglossinae should be described in Isoglossa as an interim solution . Four new species of Isoglossa are described: I. eburnea Onjalal. & I.Darbysh., I. pterocalyx I.Darbysh. & Phillipson, I. pseudoanisotes I.Darbysh. and I. conocalyx I.Darbysh. & Callm., the lattermost of which is based on Conocalyx laxus Benoist nom. illegit. In addition, Justicia onilahensis Benoist (including Ritonia poissonii Benoist) and Anisotes perplexus T.F.Daniel, Letsara & Martín-Bravo are transferred to Isoglossa , and three names within Justicia L. are synonymised within existing taxa in Isoglossinae. Lectotypes are selected for Sphacanthus brillantaisia Benoist, S. humbertii Benoist and Justicia subpaniculata Benoist (= Celerina seyrigii Benoist var. egena Benoist).
... That said, the years since Scotland Version of Record & Vollesen's (2000) classification have witnessed major strides in our understanding of species diversity in Acanthaceae in many parts of the world, from monographic and floristic perspectives in addition to the aforementioned phylogenetic advances. Progress has been most notable in Africa (e.g., Balkwill & Welman, 2000;Darbyshire & Harris, 2006;Ensermu, 2006;Hedrén & Thulin, 2006;Vollesen, 2006Vollesen, , 2007Vollesen, , 2008Vollesen, , 2013Darbyshire & Vollesen, 2007;Champluvier & Darbyshire, 2009, 2012Daniel & Figueiredo, 2009;Darbyshire, 2009;Darbyshire & al., 2009Darbyshire & al., , 2010Darbyshire & al., , 2011Darbyshire & al., , 2019cBalkwill & al., 2017;Magnaghi & Daniel, 2017;Breteler & Wieringa, 2018;Steyn, 2018), the Americas (e.g., Durkee, 2001;Ezcurra, 2002Ezcurra, , 2018Daniel & Acosta, 2003;Daniel, 2004Daniel, , 2005Daniel, , 2010Daniel, , 2015bDaniel, , 2016Wasshausen & Wood, 2004;McDade & Tripp, 2007;Indriunas, 2011;Wasshausen, 2013;Franck & Daniel, 2015;Côrtes & al., 2016a;Braz & Monteiro, 2017;Da Silva Monteiro & al., 2018;Daniel & Tripp, 2018;Tripp & Luján, 2018;Da Costa-Lima & de Oliveira Chagas, 2019;McDade & al., 2019;Zanatta, 2019;Burgos-Hernández & Castillo-Campos, 2020;McDade, 2020;Braz & al., 2021) and, to a lesser extent, in tropical Asia (e.g., Moylan & al., 2002;Wood & al., 2003;Deng & al., 2006;Wood & Scotland, 2009;Shendage & Yadav, 2010;Hu & al., 2011;Wood, 2014;Gnanasekaran & al., 2016;Bongcheewin & al., 2019;Deng, 2019;Rueangsawang & al., 2020), as well as in groups that are wide-ranging (e.g., Vollesen, 2000;Daniel & McDade, 2014). These works have, in turn, increased the knowledge base for classification of this diverse and complex family. ...
Acanthaceae are among the most taxonomically diverse, geographically widespread, and morphologically and ecologically variable lineages of flowering plants. Most modern workers have estimated more than 4000 species and potentially more than 5000 species worldwide, thus placing Acanthaceae among the 12 or so most diverse families of angiosperms. This diversity is marked by exceptional morphological variation, particularly with respect to floral forms, growth forms, and pollen types. The present work represents a synthesis of knowledge generated over the past two decades on the taxonomy and systematics of this complex plant family. We place all 191 accepted genera within a revised classification of the family. Dichotomous keys (nine in total) to recognize the major lineages of Acanthaceae are presented together with geographically partitioned keys to all genera, covering (a) Africa, Madagascar, the Mediterranean region, and Arabia; (b) Asia and Australasia; and (c) the Americas. Finally, we validate several new tribes, subtribes, and genera, and provide new combinations for species where generic delimitation has changed. Our hope is that the present contribution serves to benefit future research on the systematics of Acanthaceae and provides a foundation upon which future classification efforts can be built.
... The genus Isoglossa (Acanthaceae: Acanthoideae: Justicieae: Isoglossinae; Kiel et al. 2006) is noteworthy for containing a high number of narrowly rangerestricted taxa in tropical and southern Africa (Brummitt 1985;Darbyshire 2009;Darbyshire et al. 2011;Balkwill et al. 2017;Champluvier & Fischer 2020). When preparing the account of Isoglossa for Flora Zambesiaca (Darbyshire et al. 2015), the first author was surprised by the absence on Mt Mulanje of any species of Isoglossa in the group with an open, paniculate thyrsoid inflorescence and stamens with markedly offset anther thecaethe I. dichotoma (Hassk.) ...
... The former two are species of lower elevation, usually riverine woodland and dry forest, and belong to a species group with spiciform inflorescences and anthers with thecae held at an equal height and parallel. Isoglossa milanjiensis, which is also recorded from the Manica Highlands of Mozambique and Zimbabwe, belongs to a group with spiciform inflorescences that are most diverse in South Africa (see Balkwill et al. 2017), and includes the type species of the genus, I. origanoides (Nees) Lindau (Brummitt 1974). All of these species are quite distinct from the I. dichotoma complex at least in morphological terms; the phylogenetic relationships between and within these groups have not yet been explored. ...
Two new species are described from the proposed Mulanje-Namuli-Ribáuè Centre of Endemism. Isoglossa perdita I.Darbysh. (Acanthaceae) is apparently restricted to the submontane forests of southeastern Mt Mulanje in Malawi, and is assessed as Critically Endangered. Agelanthus patelii Polhill & Timberlake (Loranthaceae) is recorded from the montane forests of Mt Mulanje and from Mt Namuli in Mozambique, and the earlier assessment of this species as Endangered is confirmed. The habitat preferences and taxonomic affinities of these species are discussed. This work contributes to the ongoing assessment of the biodiversity and endemism of this montane region, and to the identification of Important Plant Areas in Mozambique.
... This type of life history is well observed in the genus Strobilanthes Blume (1826: 796) ( Deng et al. 2010, Tsukaya et al. 2011). This synchronous flowering and monocarpy is also observed in other Acanthaceae like Acanthopale confertiflora, Brachystephanus Nees von Esenbeck (1847: 511) (Champluvier & Darbyshire 2009), Isoglossa Oersted (1854: 155) ( Darbyshire 2009, Darbyshire et al. 2011, Poriazis & Balkwill 2008, Balkwill et al. 2016) or other Mimulopsis species. Acanthopale confertiflora also showed mass flowering in March 2013 and was observed growing sympatrically with Mimulopsis champluvierae. ...
A new species, Mimulopsis champluvierae, from Rwanda and Burundi is described. It differs from M. solmsii in the linear bracts with revolute margin, the long violet glandular hairs on the whole inflorescence including bracts and calyx, the two bracteoles that are at least half as long as the sepals, the linear sepals, the yellow corolla with purplish patterning, the capitate stigma, and the ovary with only a few hairs at the apex. The plietesial life history of M. champluvierae and M. arborescens is described. The typical M. solmsii and M. excellens show no pronounced mass-flowering, and single inflorescences are present almost every year.
Hitherto characters derived mostly from macromorphology were used to distinguish among the members of Acanthopsis Harv., a taxonomically difficult group of plants endemic to arid parts of southern Africa. The taxonomic significance of leaf and bract indumentum in Acanthopsis was investigated using light, and scanning electron microscopy. Five non-glandular and three glandular trichome types were distinguished on the leaves and floral bracts. None of these trichome types are unique to the genus. Although the indumentum is variable in Acanthopsis, the density/dominance of specific trichome types was useful to distinguish among certain taxa, particularly on the abaxial surfaces of leaves and bracts. Each species of Acanthopsis has a characteristic trichome complement as far as dominant trichome types on both leaves and bracts are concerned. However, no obvious association between the type of trichomes and habitat (degree of aridity) or geographical distribution was evident.
