Edwards Owen M, Balchan Neil R, Banks Kaleb M, Zhang Bo, Machado Fabio A, Reichert Michael S, Esquerré Damien
Department of Biology Oklahoma State University Stillwater Oklahoma USA.
Oklahoma Biological Survey University of Oklahoma Norman Oklahoma USA.
Ecol Evol. 2025 Aug 31;15(9):e72035. doi: 10.1002/ece3.72035. eCollection 2025 Sep.
Hybridization is increasingly understood as common throughout and beyond the speciation process, rather than an anomaly. Sympatric taxa are expected to exhibit strong reproductive isolation, and although hybridization may occur, it often results in inviable offspring. We investigated hybridization among three ranid frogs (, , and ) in eastern Oklahoma, where their distributions and breeding phenology overlap. Using micro-CT scans of cranial morphology, genomic SNP data, and phenological records, we confirmed two putative hybrids collected in the field-remarkable given the phylogenetic distance between these non-sister taxa. Genomic data show split ancestry from parental populations, representing one × and one × . Cranial morphology indicates hybrids exhibit intermediate phenotypes, and our assessment identified a third likely hybrid, a specimen collected two decades earlier from the same area. Both confirmed hybrids were backcrosses, but minimal introgression throughout the dataset suggests hybrid fitness may be lower than that of parental populations. Hybridization appears facilitated by overlapping breeding strategies and ecological factors leading to misdirected amplexus. This study provides the first documentation of natural hybridization in , a species of conservation concern throughout its range. Our findings emphasize the utility of high-resolution morphological data (micro-CT) in complementing genomic approaches for hybrid diagnosis and suggest cranial morphology may be an effective method for hybrid identification in similar systems. Understanding this atypical three-species hybridization has important implications for conservation, as hybrid fitness and introgression can influence population dynamics and genetic integrity.
杂交越来越被认为在物种形成过程中及之外都很常见，而非异常现象。同域分类群预计会表现出强烈的生殖隔离，虽然可能会发生杂交，但通常会产生无法存活的后代。我们调查了俄克拉荷马州东部三种蛙科蛙类（、和）之间的杂交情况，它们的分布和繁殖物候重叠。利用颅骨形态的显微CT扫描、基因组SNP数据和物候记录，我们证实了在野外采集到的两个推定杂种——考虑到这些非姐妹分类群之间的系统发育距离，这很值得注意。基因组数据显示其祖先来自亲本种群，分别代表一个×和一个×。颅骨形态表明杂种表现出中间型表型，我们的评估还确定了第三个可能的杂种，是一个二十年前从同一地区采集的标本。两个已证实的杂种都是回交后代，但整个数据集中的基因渗入极少，这表明杂种的适应性可能低于亲本种群。重叠的繁殖策略和导致抱对错误的生态因素似乎促进了杂交。这项研究首次记录了的自然杂交情况，是一个在其分布范围内都受到保护关注的物种。我们的研究结果强调了高分辨率形态数据（显微CT）在补充基因组杂交诊断方法方面的作用，并表明颅骨形态可能是类似系统中杂种鉴定的有效方法。了解这种非典型的三物种杂交对保护具有重要意义，因为杂种适应性和基因渗入会影响种群动态和遗传完整性。
