Gradient Evolution of Body Colouration in Surface- and Cave-Dwelling Poecilia mexicana and the Role of Phenotype-Assortative Female Mate Choice

Table 1

Body length (SL) and sample sizes (𝑁) of males used for the analyses of body colouration and general habitat properties in terms of light availability and turbidity.

Population origin	N	Standard length ± SE	Light availability	Turbidity [NTU]
Arroyo Bonita (AB)	12	42.8±1.8	++	0.0
El Azufre (EA)	9	27.8±0.73	++	67.0–104.3
Cueva del Azufre (CA-II, chamber II)	22	28.9±0.7	o	81.4
Cueva del Azufre (CA-V, chamber V)	40	30.0±0.5	−	45.3–85.0
Cueva del Azufre (CA-X, chamber X)	8	30.1±1.0	−−	39.0–74.6

Light availability is defined as ++: regular surface waters; +: surface water with reduced light availability due to high turbidity; o: cave habitat with dim light available through skylights; −: cave habitat with dim light available only in some areas; −−: perpetually dark cave habitat. Turbidity was measured using a shuttered turbidity probe in nephelometric turbidity units (NTU); data were taken from Tobler et al. (2006) [17].