A SYNOPSIS OF THE GENUS CHARA, SERIES GYMNOBASALIA (SUBSECTION WILLDENOWIA RDW)

The series Gymnobasalia, a sharply differentiated subgeneric complex within the genus Chara, consists of at least seven morphologically distinct species. All seven species are reproductively isolated from one another. No evidence of even limited hybridization between the seven was encountered. The two dioecious members of the complex occupy restricted and, possibly partially overlapping ranges in South America. Monoecious members are in general more widely distributed but still appear to have originated in Central or South America. The holotype of C. zeylanica Klein ex Willdenow was examined and found to be tetrascutate. For the abundant and widely distributed monoecious-conjoined, octoscutate member of the complex, previously shown to be distinct from C. zeylanica, the earlier name C. haitensis Turpin is here validated. Chara foliolosa Muhl. ex Willdenow is considered conspecific with, but to hold priority over, C. sejuncta Braun. THE CLASSIFICATION of most algae is today based largely upon morphological and physiological data. In contrast to the experimental approaches of many vascular plant taxonomists, phycologists have rarely given consideration to either the degree of reproductive isolation existing between populations or, in turn, to the variation, the viability, or the fertility of any resulting offspring. Their failure to do so doubtlessly stems largely from difficulties associated with the culture of many forms (particularly marine), the rarity or even the absence of sexual reproduction among certain groups, and finally the impossibility of ensuring the integrity of crosses between homothallic individuals. Whatever the cause, the end result has been that we still know little or nothing of the nature of most algal species. Though it is often assumed that a particular species is essentially cosmopolitan in its distribution, in most such instances it is probably more correct to state only that morphologically similar individuals are to be found over a wide area. Seldom have data been presented with respect to the presence or absence of reproductive barriers between such spatially isolated populations. Exceptions to the preceding statement have been provided by several recent studies involving breeding patterns among the, Charophyta and especially members of the genus Chara (McCracken, Proctor, and Hotchkiss, 1966; Proctor et al., 1967; Proctor and Wiman, 1971; Proctor, 1970, 1971). That morphologically similar charophytes are to be found at widely separated points around the world has been known from the 1 Received for publication 16 September 1970. Financial assistance was provided by National Science Foundation grant GB-8570. efforts of such early collectors as Braun and Nordstedt (1882) and Groves and BullockWebster (1920, 1924). The possibility for evaluating attempted crosses between designated clones subsequently arose with the realization that most m mbers of the genus Chara could be maintained indefinitely in the sexually mature state under laboratory conditions, and still later that monoecious plants could be physically emasculated. The most complete study to date (Proctor and Wiman, 1971) along these lines concerns those monoecious-conjoined members of the "Chara zeylanica complex" (Series Gymnobasalia Zaneveld; Subsection Wilidenowia R. D. W.). This complex encompasses a morphologically well defined and widely distributed group of organisms including, in addition to the aforementioned monoecious-conjoined species, both monoecioussejoined and dioecious entities. In our opinion, there are at least seven reproductively isolated and morphologically distinct species within the complex. Most of these seven members can be successfully cultured with a minimum of effort. It is already apparent that several of these species will be increasingly utilized in a variety of disciplines, though often by non-taxonomically oriented biologists. Accordingly, since several are separable only by rather subtle combinations of external cytological features, the potential for significantly augmenting our existing knowledge of the complex is unlikely to be realized unless the experimental material is correctly identified. To that end we here present a brief synopsis of the Gymnobasalia. Several changes in nomenclature are suggested. All involve the validation of earlier names; no new combinations are proposed. Known members of the G?umnobasalia share in