Researchers at the University of California, Berkeley, just finished another thrilling study. Along the way, they discovered novel insights into the mating behavior of two species of jumping spiders, Habronattus americanus and Habronattus sansoni. The study found that these females are choosy and prefer red males. This preference for natural selection is pushing hybridization and could shape the evolutionary trajectory of these species. These results inform our understanding of mate choice as an important and complex driver of biodiversity.
The corresponding study demonstrated that Habronattus americanus and Habronattus sansoni both display visual courtship stages. These phases are especially striking in their equal length. They are very different in their multimodal courtship displays. Where Habronattus sansoni admits to expanding extended multimodal phases, Habronattus americanus cuts to the chase. This divergence in courtship strategies likely leads to differences in mating success between males of each species.
Mating Preferences and Success Rates
That led to interesting and unexpected female mating preferences in the two species. Specifically, females of Habronattus americanus showed a clear preference for their own species, mating with them 73% of the time. In contrast they went on to mate with Habronattus sansoni males only 24% of the time. In Habronattus sansoni females these males were consistently less successful. In fact, they consistently preferred Habronattus americanus males 74% of the time, while choosing their own kind only 31% of the time.
This preference indicates that females of both species are more directed to males of Habronattus americanus. Together, these findings raise important questions regarding the evolutionary origins and significance of these preferences. In particular, they emphasize genetic rescue effects on the outcome of future hybridization troughs.
Impact of Coloration on Mating Success
Coloration seems to be tremendously important for mating success in these spiders. In a more controlled experiment, researchers artificially painted Habronattus sansoni males red. Their audacity paid off, increasing their mating success by a whopping 4-fold to 45%. By contrast, their brown-painted controls had a mating success of just 11%.
Habronattus americanus males were always successful in copulation in both conditions. They went on to have a success rate of 54% for red-painted males, and 48% for brown-painted males. Color is incredibly important for Habronattus sansoni. Its pretty color and majestic plumage may not jolt the boys of Habronattus americanus quite the same.
Geographic Variation and Hybridization Risks
The study noted geographic variations within the Habronattus americanus subgroup, where non-red coloration appears in three specific regions: Utah–Colorado–southern Wyoming, northern Washington into British Columbia, and northeastern California near Portola. This geographic differentiation might align with genomic patterns that dictate male coloration.
These findings must be taken seriously. To do so, they propose that this form of hybridization virtually led by female choice poses a risk to the integrity of species. Our researchers caution that these filtered selective mating interactions can still push a species to extinction by hybridizing them out. The project highlights the need to study mating dynamics to better understand how these forces work together to create ecological diversity and evolutionary trajectories.