John River drainage did not support the hypothesis that they all originated from the secondary contact between two monophyletic whitefish groups that evolved allopatrically
in the Acadian and Atlantic glacial refugia during the last glaciation events (Bernatchez and Dodson 1990a).
Studies of taxonomy and morphological variation in darters have revealed allopatrically
distributed sister taxa for several species, suggesting that vicariant events have been a major force in the evolution of the group (Mayden 1988).
Although distantly related within the genus (Emsley 1965; Brown 1981; Brower 1994a), these two species share remarkable convergence of color patterns in their allopatrically
or parapatrically distributed races, which range from southern Mexico to northern Argentina [ILLUSTRATION FOR FIGURE 2-3 OMITTED].
The tiger salamander, Ambystoma tigrinum, comprises a single species with 5-7 parapatrically or allopatrically
distributed subspecies (Gehlbach 1967; Jones et al.
They are, for the most part, allopatrically
distributed (Hall 1981), but are known to occur sympatrically at one locality: 2.5 miles north of Wenden, La Paz County, Arizona (Hoffmeister 1986; this study).
The weakness of this argument is that such sedentary creatures might speciate allopatrically
in a very small area.
Determining whether it is more likely that these host races diverged sympatrically or allopatrically
depends on obtaining additional information on the genetic basis of oviposition preference, mating preference, and physiological adaptation to the host plant.