– Surface area, measured as the largest diameter and the diameter
perpendicular to it, and calculated as 2r
2
p (assuming colonies
approximate half spheres).
– The colour brightness (pigmentation) of the upward facing colony
surface, measured to the nearest half-score on a colour reference
chart with six graduations (‘1’ being almost white, ‘6’ being
very dark; Siebeck et al., 2006; Cooper and Fabricius, 2012).
– Partial mortality, visually estimated as the percentage of colony
surface without living tissue.
– Surface rugosity of the upward facing colony surface. In Study 1,
rugosity was measured as the ratio of contoured and stretched
length of a small-gauge chain positioned across each colony
(Darke, 1991). In Study 2, rugosity was estimated as the depth
of the five deepest grooves within each of three randomly
placed 15 15 cm quadrats, with strings across the quadrat
aiding 90 alignment between a narrow ruler placed in the bottom
of the grooves and the frame. Fewer quadrats were sampled
in colonies too small to accommodate three quadrats. In
colonies smaller than the quadrat, the five deepest grooves on
the entire colony were measured.