Fig. 6: Evolved gene expression divergence between urban and forest lineages measured through a common garden experiment.
Lizards from urban and forest lineages from Mayagüez were born and raised in a common garden laboratory setting to study patterns of evolved divergence in gene expression between habitats types. A The relationship between ancestral (forest) plasticity of gene expression (25 °C vs. 32 °C) and evolved divergence in gene expression under heat challenge (forest vs urban at 32 °C). Each dot represents a single gene from the focal set of CTMAX-associated genes (n = 632). Dots displayed in black represent genes with a positive correlation between ancestral plasticity and evolved divergence. Those displayed in white represent genes with a negative association between ancestral plasticity and evolved divergence (Spearman’s ρ = −0.61). Among genes associated with heat tolerance, evolved divergence reverses the direction of ancestral plasticity. Inset: the observed correlation coefficient (red line) is more negative than the lower 95th percentile of a randomized null distribution (black line). B Bar graph representing the number of genes displaying adaptive vs. maladaptive plasticity in common garden lineages from forest (green) and urban (gray) habitats. Figure 5 outlines the methodology of plasticity categorization. Among genes associated with heat tolerance, urban lineages possess a significantly larger proportion displaying adaptive plasticity and a significantly lower proportion that displaying a maladaptive plasticity in response to increased temperature. Asterisks represent degree of significance (equality of proportions test within habitat types, exact binomial test between habitat types: *p < 0.05, ***p < 0.001). C Violin plot displaying heat-induced regulatory plasticity (log-fold change in expression from 25 °C to 32 °C) in forest (green) and urban (gray) lineages. Individual genes are represented by gray dots. Urban lineages display an overall lower magnitude of gene expression plasticity (Welch two-sample t-test: p < 0.001), congruent with evolutionary attenuation of maladaptive plasticity. Sixteen animals from common garden conditions were used for these analyses (25 °C; forest n = 4, urban n = 5) or average urban (32 °C, forest n = 3, urban n = 4).
