Divergence of male courtship displays between sympatric forms of anadromous threespine stickleback

Abstract

SummaryCourtship displays are an important component of animal reproduction, and divergence in these displays can play an integral role in promoting or maintaining reproductive isolation between species. The courtship behaviour of the threespine stickleback (Gasterosteus aculeatus) has been extensively characterized. In Japan, there are two lineages of threespine stickleback that are genetically differentiated and reproductively isolated when found in regions of sympatry. We have previously shown that males of the Pacific Ocean lineage perform the zig-zag dance, while sympatric males of the Japan Sea lineage perform a different dance, which we have termed the rolling dance (Kitano et al., 2007, Biol. J. Linn. Soc. 91: 671-685). As a first step towards understanding the role of the courtship display in female mate choice and sexual isolation between this sympatric pair, we conducted a more detailed analysis of divergence between the courtship displays of the Pacific Ocean and Japan Sea males. Kinematic analysis revealed that the tempo of the zig-zag dance is two times faster than the tempo of the rolling dance. A detailed analysis of head movements during the courtship dance revealed that the Japan Sea males erect their gill covers, extend their red throats, and open their mouths more frequently during the rolling dance than the Pacific Ocean males do during the zig-zag dance. These results demonstrate that there is extensive divergence between sympatric Pacific Ocean and Japan Sea males in both the motor patterns and the tempo of their courtship displays. Thus, the Japanese sympatric stickleback pair provides a good system to study the role of courtship behaviour in speciation, as well as the genetic mechanisms that underlie the divergence of kinematics and motor patterns in courtship behaviour.

RNA sequencing reveals small RNAs differentially expressed between incipient Japanese threespine sticklebacks

“…Fish were brought to a laboratory to examine the brain transcriptome of courting male and spawning female fish, and mating experiments were conducted in June and July 2007, as described previously [60,63,96]. Once the male fish had constructed a nest, a conspecific gravid female fish was placed in the same tank.…”

“…In contrast, the Pacific Ocean form has a simple XY sex chromosome system [62]. Previously, we found that the Pacific Ocean and Japan Sea forms diverge in male courtship behaviors and female mate choice behaviors, contributing to behavioral isolation between these two forms [60,62,63]. Furthermore, we found that divergence in the intensity of courtship behaviour, which is important for mate choice, mapped to a neo-sex chromosome (LG 9).…”

Toward conservation of genetic and phenotypic diversity in Japanese sticklebacks

“…First, G. nipponicus has a neo-sex chromosome system, which was created by Y-autosome fusion (Kitano et al, 2009;Yoshida et al, 2014). Second, the courtship dance performed by G. nipponicus males is different from the zigzag dance that is typical of G. aculeatus males (Ishikawa and Mori, 2000;Kitano et al, 2007Kitano et al, , 2008 (Fig. 2).…”

Confusion and dependence in uses of history

“…Ishikawa and Mori call the different mating dance of Japan Sea sticklebacks the "lateral display". Kitano et al (2007Kitano et al ( , 2008 identify and discuss the same mating dance of Japan Sea sticklebacks, though they give it the possibly more descriptive name of the "rolling dance". None of these scientists started out knowing any evolutionary or other history of the rolling dance.…”

“…In contrast to the claim that we need to know the history of this behavior in order successfully to predict and explain it, Rowe et al (2004) and Kitano et al (2007Kitano et al ( , 2008 first identify and understand the subtle details and dynamics of this behavior using nonhistorical sciences, and then-as a second step-they include, suggest, and/or request evolutionary explanations for the behavior. In addition, as described in exhibit (C) toward the end of Sect.…”