Table 1.

Hypotheses proposed through the Diehl and Bush (1984) framework with predicted population level patterns for each

		Predicted population level responses
Diehl & Bush categories	Hypothesis	Gene flow	Structure	Genotypic diversity
Nongenetic	Biotypic differences are not genetic in origin, but are likely associated with phenotypic plasticity, environmental effects, and endosymbionts	Ubiquitous	No structure	Little to no deviation between biotypes. Shared *MLGs common
Ubiquitous genetic	Biotypes are the product of adaptive genetic variation, but gene flow is uninhibited. Biotypic traits subject to population level drift and selection	Ubiquitous	No structure	Limited deviation between biotypes if monogenic. None if polygenic
Geographic race	Biotypes are geographically separate during sexual stages, limiting gene flow. Biotypes evolved via geographic isolation	Restricted	Strong structure by biotype and geographic gradient	Deviation in richness between biotypes. Few Shared MLGs
Host race	Biotypes associate with different primary hosts causing near sexual isolation and divergent evolutionary trajectories	Restricted	Structure between biotypes and primary host	Deviation in richness between biotypes. Few Shared MLGs
Species	Biotypes are indicative of separate species that share no gene flow	None	Strong structure by biotype populations	Genotypes significantly divergent, few or no MLG shared between biotypes

^*MLG, multilocus genotype.