Species groups in the genus <i>Ehrharta</i> (Poaceae) in southern Africa

Abstract

Ehrharta Thunb. is a genus o f Gondwanaland distribution with its centre o f diversity in the winter rainfall Fynbos Biome o f southern Africa. In recent subfamily treatments Ehrharta has proved difficult to place satisfactorily, and during the past five years it has been moved between Bambusoideae and Arundinoideae. However, most previous systematic studies using cryptic characters have covered only four taxa out o f about 35. The present study includes all African taxa, and demarcates seven species groups on the basis of both spikelet morphology and leaf blade anatomy. Parallelism and/or convergence in vegetative macromorphology within and between the species groups is widespread, and is similar, in some cases, to adaptations found in other plant families in the Fynbos Biome. However, these macromorphological trends are not reflected in the leaf anatomy. Leaf anatomy is generally consistent with the spikelet morphology. Some anatomical differences between the species groups in Ehrharta appear to be as great as differences between taxa of much higher ranks elsewhere in the Poaceae. This wide range of variability may be related to an early divergence o f Ehrharteae from other grasses, as suggested by the Gondwanaland distribution, and may explain the difficulty of placing this fascinating yet baffling genus in a subfamily. UITTREKSELEhrharta is 'n genus van Gondwanaland-verspreiding met sy middelpunt van verskeidenheid in die winterreenval-Fynbosbioom van suidelike Afrika. In onlangse subfamilie-behandelings is dit moeilik gevind om Ehrharta bevredigend te plaas, en gedurende die afgelope vyf jaar is dit oor en weer in Bambusoideae en Arundinoideae geplaas. Die meeste vorige sistematiese ondersoeke waarin verskuilde kenmerke gebruik is, het slegs vier taksons uit ongeveer 35 gedek. Die onderhawige ondersoek sluit al die Afrika-taksons in, en baken sewe spesiegroepe af op grond van die morfologie van die blompakkie en die anatomie van die blaarskyf. Parallelisme en/of konvergensie in vegetatiewe makromorfologie binne en tussen spesiegroepe is wydverspreid en is in sommige gevalle soortgelyk aan aanpassings wat by ander plantfamilies in die Fynbosbioom aangetref word. Hierdie makromorfologiese neigings word nie in die blaaranatomie weerspieel nie. Blaaranatomie is oor die algemeen in ooreenstemming met die morfologie van die blompakkie. Sommige anatomiese verskille tussen die spesiegroepe in Ehrharta blyk net so groot te w ees soos verskille tussen taksons van 'n veel hoer rang elders in die Poaceae. Hierdie wye verskeidenheid mag verband hou met 'n vroee divergensie van Ehrharteae vanaf ander grasse, soos aangedui deur die Gondwanaland-verspreiding, en mag 'n verklaring bied waarom hierdie bekorende maar raaiselagtige

Leaf anatomy of the genus <i>Ehrharta</i> (Poaceae) in southern Africa: the Villosa group

“…The group does not occupy such an isolated position within the genus as does the Seta cea group (Ellis 1987) which possesses such taxonomically significant diagnostic features as arm cells and distinct microhairs and silica bodies. There are also no anatom ical interm ediates between the Seta cea group and any of the other species groups.…”

“…Engelbrecht (1956) recognized two basic groups of species in Ehrharta -one with invaginated chloren chyma and one without. E. villosa is placed in the group with invaginations together with taxa of the Setacea and Ram osa species groups as here consti tuted (Gibbs Russell & Ellis 1987). The present find ings are in disagreem ent with Engelbrecht's (1956) grouping, as the Setacea group is the only group in which arm cells were observed (Ellis 1987) and the Setacea and Villosa groups are not considered to be closely related.…”

“…The herbarium voucher specimens used in this anatom ical study were included in the sample on which the above taxonom ic conclusions were based. The m ethodology is described in Gibbs Russell & Ellis (1987) and the form at of the paper follows that of the first paper in the series (Ellis 1987a).…”

“…are distinguished morphologically by their large spikelets with profusely hairy, conspicu ously bearded and m ucronate sterile lemmas (Gibbs Russell & Ellis 1987). The leaf blades are reduced and rolled and the culms are suffrutescent, som e times with swollen or tuberous bases.…”

ZotoviaandMicrolaena:New Zealand Ehrhartoid Gramineae*

“…Watson & Dallwitz (1992) excluded Microlaena, Petriella, and Tetrarrhena from Ehrharta but still commented that Petriella seemed scarcely distinguishable from Ehrharta and Tetrarrhena. The work of Gibbs Russell and of Ellis on the morphological and anatomical characters of the South African species of Ehrharta, summarised in Gibbs Russell & Ellis (1987), provided a wealth of information about Ehrharta against which Australasian/Malesian Microlaena, Australian Tetrarrhena, and New Zealand "Petriella" can be compared. Here we accept Microlaena as distinct from Ehrharta; Kellogg & Campbell (1987, p. 316) found that Willemse's Downloaded by [193.189.117.180] at 16:16 06 June 2016…”