Diversity and geographic distribution of riboprints from three cosmopolitan species of Colpoda Muller (Ciliophora : Colpodea)

Ribosomal RNA gene restriction site polymorphisms were determined for 114 i solates of three cosmopolitanly distributed species of Colpoda, a common so il ciliate genus. Isolates were obtained from soil samples and identificati ons confirmed using silver staining techniques. Based on restriction site a nalysis of a 1095 bp region of the large subunit (LSU) rRNA gene, thirty-on e distinct riboprints were observed; 11 unique to Colpoda steinii, 8 unique to Colpoda inflata, 10 unique to Colpoda cucullus, and two riboprints shar ed by several isolates of C. inflata and C. cucullus. The average intraspec ific genetic distance estimated from riboprint data was greatest among C. s teinii isolates (0.0790, n = 37), intermediate among C. cucullus isolates ( 0.0519, n = 37), and the least among C. inflata isolates (0.0383, n = 40). Phylogenetic analysis of riboprint data using distance methods revealed no geographic pattern in the distribution of riboprints in any of the species examined. Furthermore, many of the riboprints were globally distributed, su ggesting no equatorial barrier to species dispersal in the species examined . Several riboprints, however, appeared to be restricted on the basis of te mperature, suggesting the possibility of fitness differences among riboprin ts with respect to environmental variables. Shared riboprints between two s pecies of Colpoda indicates the limitations of riboprints in species discri mination within in this group, possibly due to the retention of ancestral p olymorphisms or the inadequate resolution of the region of LSU rRNA gene th at we examined. Additional molecular markers will be needed in order to res olve this issue.