Reproductive character displacement generates reproductive isolation among conspecific populations: an artificial neural network study

Abstract

When interactions with heterospecifics prevent females from identifying conspecific mates, natural selection can promote the evolution of mating behaviours that minimize such interactions. Consequently, mating behaviours may diverge among conspecific populations in sympatry and in allopatry with heterospecifics. This divergence in conspecific mating behaviours-reproductive character displacement-can initiate speciation if mating behaviours become so divergent as to generate reproductive isolation between sympatric and allopatric conspecifics. We tested these ideas by using artificial neural networks to simulate the evolution of conspecific mate recognition in populations sympatric and allopatric with different heterospecifics. We found that advertisement calls diverged among the different conspecific populations. Consequently, networks strongly preferred calls from their own population to those from foreign conspecific populations. Thus, reproductive character displacement may promote reproductive isolation and, ultimately, speciation among conspecific populations.

Figure 1

(a) Mean (±s.d.) for principal components that describe the combined variation in four call characters (dominant frequency, call duration, pulse rate and inter-call interval) for: the evolved calls from the three different conspecific populations (A, AB and AC), the heterospecific calls presented to the AB and AC populations during their evolution (B and C, respectively) and the initial conspecific call (ancestral A). Intersection of x-axis and y-axis standard deviation lines is the point of the mean for each. (b) Mean (±95%CI) for same principal components above comparing the evolved calls from A, AB and AC only. Non-overlapping confidence intervals indicate significant differences. Labels on axes indicate loading of call parameters on each principal component.

Figure 2

Mean (±95% CI) preference for advertisement calls from networks' own population (local calls) versus calls of alternative populations (foreign calls) over time. (a) Results for A networks; (b) results for the AB networks and (c) results for AC networks. Non-overlapping confidence intervals indicate significant differences. Dashed horizontal line shows network preferences for local calls versus those from alternative replicates of same population type in final generation.