7829 - Laserfiche WebLink

Home Browse Search

McELROY AND DOUGLAS-MORPHOLOGICAL VARIATION IN GILA 643 were found to be distinct morphologically both in sympatry and in allopatry. Second, at both Desolation and Cataract canyons, heterospecific populations were more similar to one another than they were to conspecific populations from other localities (Fig. 6, 7). Populations at these sites tended to group by locality rather than by taxonomic affinity. Results of UPGMA cluster- ing suggest that this morphological conver- gence is a within-locality (as opposed to a his- torical) phenomenon; the node separating the Desolation and Cataract canyon clusters is deep (Fig. 7). DISCUSSION Data presented here demonstrate significant among-group structure in morphological vari- ation for G. robusta and G. cypha at three levels of biological organization. Intraspecific analy- ses indicate that population divergence exists in both G. robusta and G. cypha; however, geo- graphic proximity alone is insufficient to ac- count for the hierarchical relationships ob- served among populations of either species. Comparison between species suggests that G. robusta and G. cypha represent distinct mor- phologies, both in sympatry and in allopatry. Nevertheless, patterns of variation at the ge- neric level indicate that heterospecific popula- tions at Desolation and Cataract canyons are morphologically more similar to one another than to allopatric conspecifics. These results have implications for the identification of evo- lutionary and conservation units, the potential Black Rxks Yampa River WesW_' Cr. anG-b- Debegw Canyon Rifle Desolation canyon Desolation Canyon Camel canyon Caramel canyon Black Rocks Wens -Canyon G. ryyM c.ana canymr Yampa Riva 56.0 48A 40.0 32.0 24.0 16.0 8.0 Fig. 7. Hierarchical relationships among sympat- ric and allopatric populations of Gila robusta and G. cypha. Dendrogram represents UPGMA clustering of generalized-squared Mahalanobis distances among group means. A strict consensus topology based on UPGMA, complete linkage, and single linkage clus- tering is nearly identical; a single branch (indicated by a dashed line) collapses in the consensus topology. effects of hybridization and local adaptation on morphology, and the design of conservation strategies for these fishes. Population divergence.-Previous studies of mor- phological variation among Gila from the upper Colorado Basin (Smith et al., 1979; Douglas et al., 1989; Kaeding et al., 1990) have been con- cerned with partitioning morphological varia- tion at the species level. In general, these studies TABLE 2. CLASSIFICATION OF Gila robusta AND G. cypha SPECIMENS BY SPECIES AND POPULATION. The overall classification error rate was 0.075; however, 89% of misclassifications occurred within (error rate = 0.066) as opposed to among (error rate = 0.008) species. Rows represent actual group membership; population labels are the same as for columns. Labels for each population are as in Table 1. B G. robusta C D Q R w Predicted group y B G. cypha C D G w y B 18 - - - 1 - - - - - - - - C - 6 - - - - - - - - - - - D - - 24 - - - - - - - - - - Q - - - 19 1 - - - - - - - - R - - - 1 24 - - - - - - - - W 3 - - 1 - 51 1 - - - - - - Y 1 - - 3 - 2 59 - - - - - - B - - - 1 - - - 21 - - - 3 - C - - - - - - - - 11 - - - - D - - 1 - - - - - - 22 - - - G - - - - - - - - - - 26 2 - W - - - - - 1 - 5 - - - 51 - I - - - - - - - - - - - - 5