The Tribal Position of Hypocalyptus Thunberg (Fabaceae)

The tribal position of Hypocalyptus Thunberg in the Fabaceae subfamily Papilionoideae is investigated. A phylogenetic analysis in which the Australian Bossiaeeae and Mirbelieae, African Podalyrieae and Crotalarieae, South American Sophoreae and Millettieae, and northern temperate Thermopsideae and Genisteae are included, indicates that there is no direct relationship between Hypocalyptus and any of the tribes. It is therefore proposed that the monotypic subtribe Hypocalyptinae Yakovlev be raised to tribal level as Hypocalypteae (Yakovlev) A. L. Schutte. A description of the tribe is presented, followed by an enumeration of the three species recognized. Hypocalyptus Thunberg is a genus of papilionoid legumes confined to the Cape Floristic Region of South Africa. The genus is easily recognized by its trifoliolate leaves, magenta-pink flowers with a yellow nectar guide, intrusive calyx base, and fused stamens. It comprises three distinct species, which are restricted to the fynbos vegetation of the Western and Eastern Cape Provinces (Dahlgren, 1972). Despite its well-defined generic circumscription, the tribal affinities of Hypocalyptus have been uncertain ever since Bentham's (1837, 1839) fundamental classification of the subfamily was published. This is clearly reflected in the number of times the genus has been transferred from one tribe or subtribe to another. Bentham (1837, 1839, 1844) placed the genus in the tribe Loteae subtribe Genistinae, which he later changed to the tribe Genisteae subtribe Cytisinae (Bentham, 1865). Harvey (1862) retained the genus in the Genisteae, recognizing no subtribes. In 1964 Hutchinson raised the Cytisinae to tribal level and allocated Hypocalyptus to the Cytiseae. Polhill (1976, 1981f) transferred the genus to the tribe Liparieae, which Yakovlev (1991) subdivided into the subtribes Lipariinae and Hypocalyptinae. He placed Hypocalyptus in the monotypic Hypocalyptinae. The problem regarding the tribal position of Hypocalyptus is thus quite evident. This has, in fact, also been pointed out by several authors (Dahlgren, 1972; Polhill, 1976, 1981e, 1994; Goldblatt, 1981; Bell et al., 1978; Van Wyk et al., 1994; Van Wyk & Schutte, 1995; Schutte & Van Wyk, 1997). As part of a taxonomic study of the tribes Podalyrieae and Liparieae, Schutte (1995) investigated the position of Hypocalyptus within the tribes. Morphological, anatomical, cytological, and chemical characters were examined and analyzed cladistically to determine interand infratribal relationships. The results clearly indicated that Hypocalyptus is misplaced in the Liparieae and should be excluded, while the Podalyrieae and remainder of the Liparieae are monophyletic and should be united (Schutte, 1995; Schutte & Van Wyk, 1997). Hypocalyptus deviates from the Podalyrieae (including the Liparieae) in no less than nine critical characters (Table 1). Of particular interest are the micromorphological characters, i.e., floral pigmentation (Van Wyk et al., 1994); the accumulation of canavanine in the seed (Bell et al., 1978); a chromosome base number of x = 10 (Goldblatt, 1981; Van Wyk & Schutte, 1995); and ephemeral antipodals in the female gametophyte (Schutte, 1997). These, in addition to the five macromorphological characters of the stamens, seed, and pods, indicate unambiguously that Hypocalyptus does not fit in the Podalyrieae. The aim of this paper is to examine the phylogenetic position of Hypocalyptus within the subfamily Papilionoideae. To this end we scanned the literature and selected all the tribes which are assumed to, or have previously been suggested to, be possibly related to the genus. Based on these criteria, the Australian Bossiaeeae and Mirbelieae, African Podalyrieae and Crotalarieae, northern temperate Genisteae and Thermopsideae, and South American Sophoreae and Millettieae were chosen as outgroups (see, e.g., Dahlgren, 1972; Polhill, 1976, 1981a, 1981g, 1994; Crisp & Weston, 1987). It is important to note that the primary objective of this study is to establish whether Hypocalyptus is directly related to any of the tribes, and not to analyze the relationships among the different tribes. NovoN 8: 178-182. 1998. This content downloaded from 157.55. 39.177 on Sat, 19 Nov 2016 04:23:38 UTC All use subject to http://about.jstor. org/terms Volume 8, Number 2 1998 Schutte & van Wyk Tribal Position of Hypocalyptus 179 Table 1. Taxonomic differences between Hypocalyptus and the tribe Podalyrieae. Character Podalyrieae Hypocalyptus 1. Stamen fusion free to open sheath closed tube 2. Seed aril shape interrupted at the micropylar end continuous around the hilum 3. Micropyle type punctate y-shaped 4. Micropyle position within hilar region outside hilar region 5. Pods sessile stipitate 6. Chromosome base number x = 9 x = 10 7. Antipodals persistent ephemeral 8. Floral pigments esters of cyanidin-3-glucoside malvidin-3-glucoside 9. Canavanine absent present ANALYSIS AND RESULTS The data matrix, characters, and character states used for the tribal analysis are given in Table 2. These have largely been taken from Van Wyk and Schutte (1995), with some additions and alterations, e.g., the inclusion of Hypocalyptus as a separate taxonomic unit, the incorporation of the Millettieae and the omission of the Argyrolobium group (now included in the Genisteae; Van Wyk & Schutte, 1995). Data for the Australian Bossiaeeae and Mirbelieae came mainly from Polhill (1976, 1981c, 1981d) and Crisp and Weston (1987, 1995). Information on the Millettieae and Sophoreae has been taken from Geesink (1981) and Polhill (1981b), respectively. Polhill (1976) and Bisby (1981) were consulted for information on the Genisteae, and Turner (1981) for data on the Thermopsideae. Variation in the characters and polarization of character states are discussed in the references given at the end of each character. Where plesiomorphic and apomorphic states co-occur, the taxon was scored for the plesiomorphic state. Autapomorphies for the taxa were excluded from the analyses, since they serve no purpose as grouping char-