Figure 1.
Schematic consensus phylogeny of the East African cichlids based on mitochondrial and nuclear gene segments (after [1], [25], [36]).
The haplochromines (indicated by grey branches) are a derived and species-rich clade. The males of most haplochromine species display anal fin egg-spots, just as exemplified here for Astatotilapia burtoni. A few ancestral species, such as Pseudocrenilabrus multicolor, do not have egg-spots. Note that A. burtoni belongs to a riverine clade and occurs within Lake Tanganyika and surrounding rivers.
Figure 2.
Female preference tests in Pseudocrenilabrus multicolor using computer animated stimuli.
(A) The experimental set-up consists of an iMac computer behind an experimental aquarium (60×30×30 cm). Two animations are shown simultaneously (in this case a conspecific male and a heterospecific, Astatotilapia burtoni; see [B]). (B) Results from the ‘benchmark’ experiment, in which P. multicolor females were given the choice between a conspecific and a heterospecific (A. burtoni) male. The females reacted significantly more often with the animated image showing a conspecific male. (C) Results from the ‘red fringe’ experiments, in which P. multicolor were left the choice between a male with and one without the red fringe on the tip of the anal fin. We could not detect any difference in female response, which is also backed-up by two-way choice experiments with live fish (see Figure S1). (D) Results from the ‘egg-spot’ experiment, in which P. multicolor females could choose between a natural male and a male bearing an in- silico egg-spot. Females showed a significant preference for the male with the artificial egg-spot. Arrowheads indicate the minute differences between the images presented to the females.
Figure 3.
Color preference tests in different East African cichlid species.
(A) Set-up of the field experiment at Lake Tanganyika. Fishes were presented five color dots on a transparent foil and we measured the number of pecks towards each dot. (B) Set-up of the laboratory experiments. Individual fishes were presented five color dots on a computer screen. (C) Ancestral character state reconstruction of color preferences in a phylogenetically representative set of cichlids from Lake Tanganyika. Most species clearly preferred orange or red colors. Importantly, also the substrate spawning lamprologines showed such a preference. (D–F) Results from the color-dot preference experiments in the laboratory with the haplochromines Astatotilapia burtoni (D) and Pseudocrenilabrus multicolor (E) and the lamprologine Julidochromis ornatus (F). Significant differences between males and females are indicated.