A taxonomic revision of Capnophyllum (Apiaceae: Apioideae)

The Cape endemic genus Capnophyllum Gaertn. is revised. As a result of valuable recent collections and extensive fieldwork, this hitherto neglected genus was found to comprise four annual species, two of which are newly described, namely C. lutzeyeri Magee and B.-E.van Wyk, and C. macrocarpum Magee and B.-E.van Wyk. The four species are distinguished from one another by their fruit morphology (relative length of the styles, the shape and position of the stylopodium, fruit size, surface sculpturing, and the presence or absence of a sterile apical portion) and fruit anatomy (marginal wings slightly or prominently involute and secondary ribs present or absent). A comprehensive key to the species, their complete nomenclature and typification, together with complete descriptions and known geographical distributions for all the species are presented and illustrated. © 2009 SAAB. Published by Elsevier B.V. All rights reserved.


Introduction
Capnophyllum Gaertn. is a genus of small annual herbs endemic to South Africa. The name is derived from the Greek (kapnos = smoke, but is also the Greek name for Fumaria; phyllon = leaf) and refers to the distinctly glaucous leaves that closely resemble those of the genus Fumaria L. (Sonder, 1862;Adamson, 1950). Capnophyllum is sometimes extended to include the Mediterranean Krubera peregrinum Lowe (e.g. Tutin et al., 1968;Dyer, 1975;Downie et al., 1998). However, according to Meikle (1977), Krubera Hoffm. can be distinguished from Capnophyllum by fruit and floral differences. Burtt (1991) followed Meikle (1977) in considering Capnophyllum to be a South African endemic genus. Recently, Magee et al. (in press) using molecular and morphological data, provided strong support for the monophyly of Capnophyllum and for its placement within the Lefebvrea clade of the tribe Tordylieae, together with the Cape genera Dasispermum, Sonderina and Stoibrax capense (therein referred to as the Cap-nophyllum group). In contrast, Krubera was shown to be only distantly related, occupying a position somewhere between the tribes Apieae and Selineae (Downie et al., 1998(Downie et al., , 2000Winter et al., 2008;Magee et al., in press).
Until relatively recently, the genus in the strictest sense was considered to be monotypic, with two varieties of C. africanum (L.) Gaertn. recognised on the basis of fruit surface sculpturing. Goldblatt and Manning (2000), however, found that the two varieties were morphologically and geographically distinct and therefore raised C. africanum var. leiocarpon Sond. to the rank of species, as C. leiocarpon (Sond.) J.C. Manning and Goldblatt. As a result of valuable recent collections and extensive fieldwork, this hitherto neglected genus was found to comprise four species, two of which are as yet undescribed. We present here a detailed taxonomic treatment of the genus, including a key to the species, their complete nomenclature, typification, formal descriptions, as well as the known geographical distributions.

Materials and methods
The complete collections of Capnophyllum from the following herbaria were studied: BM, BOL, JRAU, K, NBG (including SAM and STE), PRE and S (herbarium acronyms as in Holmgren et al., 1990). Extensive field work was undertaken to study all the taxa in situ, thus providing crucial additional insight into the species concepts proposed in this study. From this material, together with geographical information from Leistner and Morris (1976), the recorded distribution of the species was carefully verified and mapped. The line drawings (Figs. 1 and 2) were made by the first author with the aid of a camera lucida attachment on a Wild M3Z stereomicroscope.
FAA and herbarium material were used to study fruit anatomy. The herbarium material was first rehydrated and then placed in FAA for a minimum of 24 h. The material was subsequently treated according to a modification of the method of Feder and O'Brien (1968) for embedding in glycol methacrylate (GMA). This modification involves a final infiltration of the material in GMA for five days. Staining was done according to the periodic acid Schiff/toluidine blue (PAS/TB) staining method (Feder and O'Brien, 1968). The terminology used to describe the fruit anatomy follows that proposed by Kljuykov et al. (2004). Voucher specimens for the fruit anatomical study are listed below. To study the three-dimensional structure of the vittae (oil canals), mature fruit were softened by soaking them in boiling water for 24 h. The exocarp was then peeled off while keeping the fruit submerged in water to prevent desiccation.

Vegetative morphology
The four species of Capnophyllum are all annual herbs which exhibit a sympodial growth pattern similar to that found in the closely related genus Sonderina H. Wolff (Magee et al., in press). In both these genera, the stem consists of a series of sympodial segments each ending in a terminal umbel which becomes laterally displaced by continued growth from the axillary bud of the uppermost leaf, which takes over as the main growth axis (Burtt, 1991). In Capnophyllum the plants are all well-branched sprawling herbs in which the branches become prostrate or decumbent (Fig. 1a-c). As the generic name implies, the leaves are always characteristically glaucous. They are pinnate to bi-pinnate and mostly cauline (Fig. 1), with the ultimate leaflet segments flat or subterete and less than 1 mm broad (Fig. 1d). All the species are relatively small in stature (ranging from 50-500 mm in height). Capnophyllum lutzeyeri appears to be more robust than the other species, while C. macrocarpum (Fig. 1a) is generally much smaller at maturity. However, as both these species are known from only a single locality, the size of the plants may eventually prove to be of limited diagnostic value.

Reproductive morphology
The relatively small compound umbels appear to be laterally borne along the stems but are in fact terminal and become leafopposed due to continued growth from the axillary shoots. The bracts of the involucre and involucel may be either free or connate at their bases, and the rays and raylets are invariably glabrous (Fig. 1f). The umbels of C. macrocarpum are always very sparse with only two or three rays consistently present (Fig. 1a). The other species usually have at least four rays, although two or three may rarely be present in C. leiocarpon and C. lutzeyeri.
The hermaphroditic flowers are pentamerous, with indistinct sepals and white, oblong to obovate, papillose petals with acuminate inflexed tips (Fig. 1e). The ovaries of C. africanum (Fig. 1f) and C. macrocarpum are distinctive in that they are prominently tubercled, while in the other species they are smooth.
The shape and position of the stylopodia in mature fruit were found to be useful diagnostic characters (Fig. 2). The stylopodia are either conical and raised above the fruit apex as in C. africanum ( Fig. 2a and e), C. leiocarpon ( Fig. 2c and g) and C. lutzeyeri ( Fig. 2b and f), or very shortly conical to flattish and diagnostically sunken below the fruit apex in C. macrocarpum ( Fig. 2d and h). The styles are at first erect and relatively short, but may lengthen as the fruit mature. Their relative length is an important diagnostic character. In C. macrocarpum ( Fig. 2d and h) the styles remain erect and relatively short whereas in the other species they lengthen markedly and become reflexed. The styles of C. leiocarpon become reflexed far beyond the base of the stylopodium ( Fig. 2c and g), while in the similar C. lutzeyeri they are reflexed only up to, at most, the stylopodium base ( Fig. 2f). In C. africanum there appears to be some variability in that the styles may become reflexed either up to or beyond the base of the stylopodium.
The fruit of Capnophyllum are dorsally compressed, with the marginal ribs expanded into narrow wings (Fig. 2) and the commissure extending over the full width of the mericarp (i.e. to the very edge of both marginal ribs). The marginal wings are distinct in that they are slightly to prominently involute, so that the commissural surface is very slightly to prominently concave (Fig. 3). In transverse sections of immature fruit, the commissural area between the marginal wings is composed of parenchymatous cells which do not become lignified with maturation of the fruit. Instead these cells disintegrate to create a hollow between the two mericarps ( Fig. 3a and b). The median and lateral ribs are slightly prominent to prominent and are diagnostically tubercled in C. africanum (Fig. 2a) and C. macrocarpum (Fig. 2d). Secondary ribs are often present above the vallecular and commissural vittae in C. africanum, C. leiocarpon and C. lutzeyeri (Fig. 3a, c and d).
The fruit of C. macrocarpum (Fig. 2d) are the largest in the genus, with even the smallest fruit of this species distinctly larger than the largest fruit of C. africanum (Fig. 2a). In transverse section there are two commissural vittae as well as four solitary vallecular vittae (Figs. 3 and 4) in each mericarp of all the species.
In Capnophyllum macrocarpum there is a prominent sterile apical portion on the fruit that can most easily be seen by comparing the extent of the commissural vittae (Fig. 4a). In this species the commissural vittae terminate well below the stylopodium; in C. lutzeyeri they terminate slightly below the stylopodium leaving a much smaller sterile portion (Fig. 4c). In the remaining species the commissural vittae terminate at the base of the stylopodium so that there is no conspicuous sterile portion ( Fig. 4b and d).

Comparison of Capnophyllum and Krubera
The fruit of Capnophyllum and Krubera are superficially similar in having prominent ridges on the dorsal surface, a broad commissure, dorsally compressed mericarps and marginal ribs extended into wings. On close examination of the fruit anatomy, however, the two genera are clearly distinct. The fruit of Krubera (Fig. 3e) have extremely small, inconspicuous commis-sural and vallecular vittae unlike those of the species of Capnophyllum (Fig. 3a-d) where the vittae are relatively large and conspicuous. The fruit of Krubera also differ markedly in the presence of large rib oil ducts. The fruit anatomical data therefore supports the separation of the two genera as found by Magee et al. (in press).

Diagnostic characters
Species of Capnophyllum are annual, often sprawling, white-flowered herbs with soft, glaucous leaves resembling those of Fumaria. They differ from other vegetatively similar annual African genera by the dorsally compressed, narrowlywinged fruit with a broad commissure (100% of mericarp width). They are distinct from African peucedanoid genera in their sympodial growth pattern resulting in leaf-opposed umbels. All other African peucedanoid genera have a monopodial growth pattern with terminal umbels. Furthermore, the fruit differ from those of other annual African peucedanoids in the usually prominent median and lateral ribs, the narrowlywinged marginal ribs which are slightly to prominently involute, the often conspicuous secondary ribs on both the commissural and dorsal surfaces, the slightly to prominently concave commissural surface of the mericarps and the strongly elliptical outline in both dorsal and lateral views as a result of the convex outer surface.
The species often co-occur with the superficially similar and widespread Sonderina hispida (Thunb.) H.Wolff. Although the fruit of Capnophyllum are fundamentally different from those of Sonderina (in Sonderina the fruit are isodiametric, lack marginal wings and have a narrow commissure), when in flower they may easily be confused with one another. However, even when in flower Capnophyllum species can be distinguished by their prostrate habit, glaucous leaves, tubercled ovaries in C. africanum and C. macrocarpum (glabrous or more usually scabrous or pilose in Sonderina hispida), petals appearing truncate or at most shallowly-emarginate in dorsal view (deeply-emarginate in Sonderina), and glabrous umbels (scabrous in Sonderina hispida).

Distribution and habitat
The four species are endemic to the Cape Floristic Region of South Africa (Figs. 5 and 6) and occur in sandy soil near to the coast. The species are generally allopatric in their distributions; however there is some overlap between the ranges of C. africanum and C. leiocarpon around Langebaan and Saldanha.
Capnophyllum simplex Lagasca, Gen. and Sp. Nov. 13 (1816) The specimen in S is chosen here as the label is in Meyer's handwriting and bears the annotation "mihi".].

Diagnostic characters
Capnophyllum africanum is vegetatively similar to C. leiocarpon and C. lutzeyeri but differs in that both the ovaries and fruit are covered with tubercles on the median and lateral ribs, as in C. macrocarpum. It differs from the latter species, however, in the larger number of rays per umbel (4 or more), the smaller fruit (less than 8 mm long) without a sterile apical portion and with the shortly conical stylopodium raised above the fruit apex.

Distribution and habitat
Capnophyllum africanum is endemic to the Western Cape Province, occurring from Gordons Bay and the Cape Peninsula northwards along the coast to Vredenburg (Fig. 5). This species has also been collected on Robben Island. It occurs in open Strandveld on deep sandy soils.

Diagnostic characters
Capnophyllum leiocarpon differs from C. africanum and C. macrocarpum in the absence of tubercles on the ribs of both the ovaries and fruit. It can be distinguished from C. lutzeyeri by the longer styles of the mature fruit that become reflexed far beyond the base of the stylopodium, and the only very slightly concave commissural surfaces of the mericarps.

Diagnostic characters
As in Capnophyllum africanum, both the ovaries and fruit are covered with tubercles on the median and lateral ribs. Capnophyllum macrocarpum differs from this species in the larger fruit (more than 8.5 mm long) with a conspicuous sterile apical portion and the rudimentary stylopodium that is sunken below the apex of the fruit. Furthermore, the umbels of this species appear to have fewer rays (2 or 3).

Distribution and habitat
This species is known only from De Hoop Nature Reserve in the Western Cape Province (Fig. 6). It was collected in fynbos, on deep sandy soils. A search of the surrounding area did not reveal any further populations, indicating that the species may be highly localised.