Comparison of Alternative Hypotheses for the Origin of the Angiosperms

Abstract

The development of a phylogenetic system of classification for the flowering plants is dependent on the objective resolution between alternative hypotheses for their origination. Here six hypotheses have been selected for comparison. Contemporary systems are unanimous in their support for the “ranalean theory,” which was developed by Delpino (1890), Hallier (1912), and Bessey (1915). According to this theory, the order Magnoliales (Takhtajan, 1987; Dahlgren, 1989) or the family Winteraceae (Cronquist, 1981; Thorne, 1992a) are considered to be the most primitive angiosperms. The new Calycanthales hypothesis (Loconte and Stevenson, 1991) also conforms to the “ranalean theory.” These three hypotheses are compared to three other hypotheses that contradict the “ranalean theory.” Recently, Taylor and Hickey 1990a, Taylor and Hickey 1992) have elaborated the Chloranthaceae hypothesis. Even more recently, Chase et al. (1993) have supported the Ceratophyllaceae hypothesis (Les, 1988). Finally, the historical Casuarinaceae hypothesis of Engler (Melchior, 1964) will be considered.