Collaborative Research: Cognitive deficiency as a source of reproductive isolation between hybridizing species

当不同物种彼此繁殖或杂交时，这两个原始物种可能会失去它们的独特性，除非杂交变得不利，比它们的双亲更不适合。大多数关于杂交劣势的研究都集中在杂交不育或胚胎发育问题上。然而，学习和记忆等认知能力的下降也可能对混合动力车造成不利影响。学习和记忆对许多物种来说都很重要，但杂交种的学习和记忆缺陷是否能够保持物种的分离还是个未知数。这个合作项目将评估学习和记忆缺陷维持杂交山雀物种之间物种边界的可能性。这项工作将填补我们对物种发展和维持这一基本进化过程的理解的一个重要空白。它将启发进化论、行为学和神经科学研究的新途径。这项研究对生物多样性的保护也具有重要意义。通过这个项目，研究人员将培养博士后和研究生。此外，未被充分代表的本科生将获得研究和科学交流方面的综合培训。在本学年，参与每个机构指导研究的学生将在暑假期间在其他相关机构之一从事该项目的不同方面的工作。作为暑期体验的一部分，学生们将与康奈尔鸟类学实验室的鸟类学院合作，开发一个关于鸟类杂交的高流量在线模块。因此，他们将学会使用不同的研究方法来解决共同的问题，并向公众传播科学。混血儿的学习和记忆是如何发挥作用的，这方面的研究相对较少。这些特征是自然选择形成的，但它们在维持物种边界方面的作用尚不清楚。这项拟议研究的总体目标是将行为与神经解剖学和基因组学相结合，以评估认知能力杂交缺陷对合子后生殖隔离的贡献。利用自然杂交的黑帽山雀和卡罗莱纳山雀，这项拟议的研究将检验中心假设，即选择对记忆和学习能力不足的杂交种起作用，这些缺陷反映在神经解剖学和基因组变异上。这个系统非常适合测试认知在合子后生殖隔离中的作用，因为学习和记忆对两个物种的健康都很重要。初步数据表明，杂交山雀的记忆力不足，海马神经元较小，与学习和记忆相关的基因参与了生殖隔离。研究小组将在宾夕法尼亚州东部的一个混合区样带解决中心假说。通过学习和记忆的行为测试、比较神经解剖学、RNA测序和全基因组重测序，这项研究将：1)确定黑帽、卡罗莱纳和杂交山雀的相对学习和记忆能力；2)量化杂交山雀和亲本山雀之间的神经解剖学差异；3)识别生殖隔离和认知基因错误表达的特征。通过完成和整合这些目标，这项研究将在第一次混合学习和记忆缺陷测试中将认知与物种形成联系起来，作为合子后生殖隔离障碍。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

When different species breed with each other, or hybridize, the two original species can lose their distinctiveness unless hybrids become disadvantaged and less fit than their parents. Most research into hybrid disadvantage has focused on hybrid sterility or embryonic developmental problems. However, reductions in cognitive abilities such as learning and memory could also cause disadvantages for hybrids. Learning and memory are important for many species, but whether deficits in hybrids' learning and memory can function in keeping species separate is unknown. This collaborative project will evaluate the possibility that learning and memory deficiencies maintain the species boundary between hybridizing chickadee species. This work will fill an important void in our understanding of the development and maintenance of species, a fundamental evolutionary process. It will inspire new avenues of research in evolution, behavior, and neuroscience. The research also has important implications for the conservation of biodiversity. With this project, the researchers will train postdoctoral and graduate students. Additionally, underrepresented undergraduate students will gain integrative training in research and science communication. Students involved in mentored research at each institution during the academic year will work on a different aspect of the project at one of the other involved institutions during the summer. As a part of the summer experience, the students will collaborate with the Bird Academy at the Cornell Lab of Ornithology to develop a high-traffic online module on bird hybridization. They will therefore learn to employ diverse research approaches to address a common question, and to communicate science to the public. How learning and memory function in hybrids is relatively unexplored. These traits have been shaped by natural selection, but their role in the maintenance of species boundaries is unknown. The overall objective of the proposed research is to integrate behavior with neuroanatomy and genomics to evaluate the potential for hybrid deficiencies in cognitive ability to contribute to postzygotic reproductive isolation. Using naturally-hybridizing black-capped and Carolina chickadees, the proposed research will test the central hypothesis that selection acts against hybrids deficient in memory and learning, and that these deficiencies are reflected in neuroanatomic and genomic variation. This system is well suited for testing the role of cognition in postzygotic reproductive isolation because learning and memory are important for fitness in both species. Preliminary data suggest that hybrid chickadees have deficient memories and small hippocampal neurons, and that genes linked to learning and memory are involved in reproductive isolation. The research team will address the central hypothesis in an eastern Pennsylvania hybrid zone transect. With behavioral tests of learning and memory, comparative neuroanatomy, RNA sequencing, and whole-genome resequencing, the research will: 1) determine the relative learning and memory abilities of black-capped, Carolina, and hybrid chickadees; 2) quantify neuroanatomic differences between hybrid and parental-species chickadees; and 3) identify signatures of reproductive isolation and misexpression in genes underlying cognition. Through the completion and integration of these aims, this research will connect cognition with speciation in the first test of hybrid learning and memory deficiency as a postzygotic reproductive isolating barrier.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.