7022 - Laserfiche WebLink

Home Browse Search

Jill!! ?I?I?? lid 832 I I ( I I I I I I I I I I I I I ` ?' III I I I I I U o a, V '. ch DO ,n w .. V a m mrn-- ? CIS Z V 1 w 1 C4 V u 3 I I I I III I 1--1? ^ G d 00 CO I I I I III I a III I I I I I ?' III an 00 s to OO n ci r- cq COPEIA, 1991, NO. 3 GV -. CO 'Do' n C-1 -. CO co r` nl 00 ao rn In 00 00 II i i I I - cq G in to r` an co .n ao CIeq I 1 I I I I I I I I I I 00 I 11= C4 00 a v 000 v v ?' ?' c? CJ o4 dW is o U .4 a a Gila robusta and G. elegans) suggest that P. lucius is the most primitive species, and that P. umpquae and P. oregonensis are the most derived, sister taxa." Our cladogram (Fig. 5) rooted using two taxa of sister lineages of Plychocheilus depicts the former pattern of divergence. A sister-group relationship between Ptychocheilus and the Gila robusta complex has not been recognized; there- fore, choice of outgroup taxa from within the latter would be inappropriate. The choice of ingroup fossils, and scenarios built upon their minimum-reported age, instead of direct com- parisons using legitimate outgroup taxa, caused Carney and Page to favor their second hypoth- esis of relationships. A phylogenetic classification developed from the sequential hierarchy of relationships within Ptychocheilus (Fig. 5) would not include any com- bination of taxa as subspecies regardless of their degree of overall similarity. The two most sim- ilar species, P. oregonensis and P. umpquae, do not share a sister-group relationship, and each step they represent is supported by multiple syn- apomorphies. Similarities shared by these two species represent primitive traits and are not evidence of gene flow or conspecificity. There- fore, neither intrageneric nor intraspecific tax- onomic changes are warranted. Mylopharodon and Ptychocheilus may be distin- guished morphologically. However, taxonomic change based on "degree of difference" has no place in a phylogenetic classification scheme (Bush and Mayden, 1981; Buth, 1984) regard- less of whether the characters involved are mor- phological or biochemical. Placing Mylopharo- don and Ptychocheilus in synonymy would communicate their close relationship, but would obscure the sister-group relationship of Mylo- pharodon conocephalus to the clade of Ptychochei- lus and represent a loss of information. The recognition of these two lineages as subgenera might accomplish the former goal but would not alleviate the latter problem of communi- cation. Thus, we advocate continued recogni- tion of Mylopharodon while additional studies of western North American cyprinids are in prog- ress. A KEY TO THE SPECIES OF PMHOCHEfLUS The most detailed key to the species of Ptycho- cheilus was provided by Moore (1968). Unfor- tunately, Moore erred in reporting nine anal rays for P. oregonensis (critical in the first couplet of the key). Eddy and Underhill (1969) reported