CLASSIFICATION AND RELATIONSHIPS

Hapaline has always occupied an anomalous position in the various proposed aroid classifications. Schott (1860) produced a family classification based primarily on floral characters. Paleotropical Hapaline went in otherwise neotropical subtribe Syngoninae of tribe Caladieae (including Caladium Vent., Syngonium Schott and Xanthosoma Schott); evidently he had realised Hapaline was rather different from the palaeotropical genera of his tribe Caladieae. Engler (1876a, 1876b), working mainly with vegetative characters, redefined tribe Caladieae of his subfamily Colocasioideae, removing all but Caladium and Xanthosoma and not suggesting a placement for Hapaline. Engler (1879) expanded on this arrangement, including all genera known to him and placed Hapaline in tribe Caladieae. Engler maintained this classification for NatÙrlichen Pflanzenfamilien (Engler 1889) but by 1920 had reconsidered the generic position of Hapaline and recognized a new monogeneric subtribe, Hapalininae, (tribe Colocasieae: subfamily Colocasioideae), to emphasize the apparent isolation of the genus (Engler & Krause 1920). Grayum (1990) produced a classification based on a wider range of characters but retained Hapaline in much the same position as Engler. Bogner & Nicolson (1991) produced an essentially updated Englerian classification and did not alter the position of Hapaline from that of Engler (1920). Recently Mayo, Bogner & Boyce (in press) have undertaken a cladistic analysis of the Araceae as part of the ëGenera of Araceae‰ project. This has radically altered the topography of Engler's suprageneric family classification. Some of Engler's subfamilies, including the Colocasioideae, have been dismantled. Hapaline is assigned to Caladieae, one of two tribes in the ëCaladium alliance‰ . Besides Hapaline, tribe Caladieae contains all the neotropical genera recognized by Engler in his subfamily Colocasioideae. The other palaeotropical genera of Engler's Colocasiodeae are placed in Colocasieae, one of 15 tribes for which no alliance has been established.