Abstract

BackgroundPostzygote isolation is an important part of species isolation, especially for fish, and it can be divided into two aspects: genetic isolation and ecological isolation. With the increase in parental genetic distance, the intensity of genetic isolation between them also increases. Will the increase in parental ecological niche differences also lead to the increase in ecological isolation intensity between them? This question is difficult to answer based on the current literature due to the lack of hybridization cases of contrasting ecological niche parents.ResultsCyprinid fish parents (Schizothorax wangchiachii and Percocypris pingi) with contrasting ecological niches (herbivorous and carnivorous) and their F1 hybrids were used as research objects. Fish and periphytic algae were selected as food corresponding to different parental resources. The foraging-related traits of these hybrids are generally the same between parents; however, the intermediate foraging traits of hybrids did not result in intermediate foraging performance for parental resources, and these hybrids could hardly forage for parental resources. The poor foraging performance of these hybrids for parental resources was caused not only by the decline in the foraging ability of these hybrids but, more importantly, by the decrease in foraging activity. Interestingly, these hybrids initially showed a high interest in foraging small fishes; however, after the first successful capture, these hybrids had difficulty ingesting fish and spit them out, which led to the subsequent decrease in foraging activity. We designed a series of experiments to explore the mechanism of the fish spitting of these hybrids, excluding the taste and the size of prey, and found that the decrease in their pharyngeal tooth puncture ability may be the reason.ConclusionsThis study was the first to demonstrate that these parents with contrasting ecological niches will produce great postzygotic ecological isolation for parental resources. The poor foraging performance of these hybrids for parental resources is mainly due to the decrease in foraging activity. Interestingly, these hybrids have obvious fish-spitting behaviour, which is a typical example of the incompatibility between intermediate traits and genetic behaviors.

Highlights

  • What are species? The biological species concept defines “species” as populations that can mate with each other and have isolating barriers with other populations, where isolation barriers can be divided into prezygote barriers and postzygote barriers [1]

  • Morphology Regarding the external and skeletal morphology, most PS traits were between Percocypris pingi (PP) and Schizothorax wangchiachii (SW) as supported by

  • It is worth mentioning that the tail length of PS is longer than that of the parents, which is the main reason why PCA2 of PS is different from that of the parents in the principal component analysis (PCA) of external morphology (Additional Tables 3 and 5)

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Summary

Introduction

The biological species concept defines “species” as populations that can mate with each other and have isolating barriers with other populations, where isolation barriers can be divided into prezygote barriers and postzygote barriers [1]. The postzygote isolation is important for fishes. Many studies have demonstrated intrinsic isolation, but the potential ecological contributions to postzygote isolation are very important [18,19,20,21]. Postzygote isolation is an important part of species isolation, especially for fish, and it can be divided into two aspects: genetic isolation and ecological isolation. With the increase in parental genetic distance, the intensity of genetic isolation between them increases. Will the increase in parental ecological niche differences lead to the increase in ecological isolation intensity between them? Will the increase in parental ecological niche differences lead to the increase in ecological isolation intensity between them? This question is difficult to answer based on the current literature due to the lack of hybridization cases of contrasting ecological niche parents

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