. The Canadian field-naturalist. Natural history. 2003 Aoki and Bodaly: Gillraker Forms of Cisco 51 E 1-2 c 0 0) (0 O o = 0 i -Hi BDugn BS o a „ p D Bo "D-D- Log Fork Length (mm) Figure 2. Relationship between gillraker length and fork length for low and high gillraker ciscoes from Lake Athapapuskow. technique or to actual changes in gillraker numbers over the 30-year interval between sampling. The primary debates regarding the origin of close- ly related sympatric forms of coregonid fishes centre on timing (post-glacial vs. glacial) and mechanism (sym
. The Canadian field-naturalist. Natural history. 2003 Aoki and Bodaly: Gillraker Forms of Cisco 51 E 1-2 c 0 0) (0 O o = 0 i -Hi BDugn BS o a „ p D Bo "D-D- Log Fork Length (mm) Figure 2. Relationship between gillraker length and fork length for low and high gillraker ciscoes from Lake Athapapuskow. technique or to actual changes in gillraker numbers over the 30-year interval between sampling. The primary debates regarding the origin of close- ly related sympatric forms of coregonid fishes centre on timing (post-glacial vs. glacial) and mechanism (sympatric vs. geographic) of speciation. Many recent authors have tended to favour a post-glacial, sympatric origin for these forms (, Clarke 1973; Todd and Smith 1992; Turgeon et al. 1999). Schluter (1996) has emphasized the role of resource- driven selection pressures and competition for resources in producing reproductive isolation within lakes. Successive waves of invading populations during post-glacial colonization of lakes may also have provided the opportunity for microgeographic speciation. Two questions remain regarding the ciscoes of Lake Athapapuskow. First, has the Shortjaw Cisco disappeared from the lake? Further sampling is need- ed at greater depths. Second, are the two forms of Cisco completely reproductively isolated in the lake? The existence of reproductive isolation between the sympatric ecotypes will require more intensive work on the timing and location of spawning and also on the genetic relationship between the two forms. Acknowledgments We thank Robert Fudge and James Johnson for capturing the fish and James Reist and Robert Fudge for assistance in the lab. Thanks also to Mme. Radi for valuable advice. Literature Cited Clarke, R. M. 1973. The systematica of ciscoes (Coregonidae) in central Canada. thesis. University of Manitoba, Winnipeg. Manitoba. Henault, and R. Fortin. 1989. Comparison o\' meris- tic and morphometrie characters among sp
Size: 1756px × 1423px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectnaturalhistory, booky
