Fig. 3

3D analysis of optic parameters in D. simulans and D. mauritiana eyes. a–d Ommatidial lens volumes from 3 males and 3 females from each of the two species. Eye maps show the smallest and largest eye of each of the two species, which also happen to be one male and female of each. Each dot of the scatter plot represents the location of an individual ommatidium in polar coordinates coloured by its 3D volume according to the colour scale indicated in the x- and y-axes of b and c. Line colours in b and c and dot colours in d indicate the fly’s rank in order of eye size per species, such that the darkest one is the largest eye of that species. The volume data is divided into 20 evenly spaced bins of elevation (b) and azimuth (c) with error bars indicating 3 times the standard error of the mean. d Ordinary least squares were used to regress lens volume on azimuthal position to estimate and compare the azimuthal slope of lens volume between the two species. The resulting slope coefficients from those models are plotted. e–h IO angle from three males and females from each of the two species, plotted as in a–d except for the elevation plot in f. The IO angle value used for each lens represents the average IO angle between that lens and all immediate neighbours. f The same IO angle data from e but sampling ommatidia from a narrow vertical band between 0 ± 15° azimuth. Note that this is different from b, c, and g because plotting the binned averages obfuscates the horizontal band of high acuity along the equator, likely due to the large range of IO angles along azimuth. h Ordinary least squares was used to regress IO angle on azimuthal position as in d. All the eyes demonstrated negative azimuthal slopes, with no significant difference between species. i–m Scatterplots of total lens count (i), mean lens diameter (j), median IO angle (k), median equatorial IO angle (l), and IO angle interquartile range (m) plotted along the y-axes and their allometric relationship to the surface area of their eye along the x-axis. Lines in the 2D scatter plots represent the predicted mean and the bands represent the 95% CI of the mean based on ordinary least squares regression of each y variable on surface area. Note that simple group differences based on ANOVA are indicated in the left margins and group differences after accounting for surface area using linear regression are indicated at the top of each scatterplot with the following key: * = p < .05, ** = p < .01, and *** = p < .001. Data provided in Fig. 3_share.zip on figshare [29]