Figure 2.

Scatterplot of two disease susceptibility variables versus estimated host population genetic diversity (heterozygosity) values. (a) Louse abundance versus host population genetic diversity. Closed circles, average amblyceran abundance ±95% confidence intervals (Colpocephalum turbinatum, Laemobothrion maximum, and Kurodaia sp.; r=−0.949, n=9, p<0.0001); open circles, average ischnoceran abundance ±95% confidence intervals (Degeeriella regalis; r=−0.854, n=9, p<0.01). Dyads with heterozygosity values greater than 0.9 represent a mainland B. swainsoni population and the remaining values represent eight island populations of B. galapagoensis. Island populations reading left to right are as follows: Santa Fe, Española, Pinzón, Marchena, Pinta, Isabela, Fernandina, Santiago; (b) average agglutination titres (NAbs)±SDM from 46 B. galapagoensis individuals versus estimated host population genetic diversity (the relationship between NAb agglutination titres and genetic diversity was not linear, although significant differences existed in average NAb agglutination titres among island-populations, one-way ANOVA: F_6,39, p<0.01). Island populations reading left to right are as follows: Santa Fe, Española, Marchena, Pinta, Isabela, Fernandina, Santiago.