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Wright DS, Rodriguez-Fuentes J, Ammer L, Darragh K, Kuo CY, McMillan WO, Jiggins CD, Montgomery SH, Merrill RM. Selection drives divergence of eye morphology in sympatric Heliconius butterflies. Evolution 2024; 78:1338-1346. [PMID: 38736286 PMCID: PMC7616201 DOI: 10.1093/evolut/qpae073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Revised: 05/02/2024] [Accepted: 05/10/2024] [Indexed: 05/14/2024]
Abstract
When populations experience different sensory conditions, natural selection may favor sensory system divergence, affecting peripheral structures and/or downstream neural pathways. We characterized the outer eye morphology of sympatric Heliconius butterflies from different forest types and their first-generation reciprocal hybrids to test for adaptive visual system divergence and hybrid disruption. In Panama, Heliconius cydno occurs in closed forests, whereas Heliconius melpomene resides at the forest edge. Among wild individuals, H. cydno has larger eyes than H. melpomene, and there are heritable, habitat-associated differences in the visual brain structures that exceed neutral divergence expectations. Notably, hybrids have intermediate neural phenotypes, suggesting disruption. To test for similar effects in the visual periphery, we reared both species and their hybrids in common garden conditions. We confirm that H. cydno has larger eyes and provide new evidence that this is driven by selection. Hybrid eye morphology is more H. melpomene-like despite body size being intermediate, contrasting with neural trait intermediacy. Overall, our results suggest that eye morphology differences between H. cydno and H. melpomene are adaptive and that hybrids may suffer fitness costs due to a mismatch between the peripheral visual structures and previously described neural traits that could affect visual performance.
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Affiliation(s)
- Daniel Shane Wright
- Division of Evolutionary Biology, Faculty of Biology, Ludwig Maximilian University of Munich, Munich, Germany
| | - Juliana Rodriguez-Fuentes
- Division of Evolutionary Biology, Faculty of Biology, Ludwig Maximilian University of Munich, Munich, Germany
| | - Lisa Ammer
- Division of Evolutionary Biology, Faculty of Biology, Ludwig Maximilian University of Munich, Munich, Germany
| | - Kathy Darragh
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
- Smithsonian Tropical Research Institute, Gamboa, Panama
| | - Chi-Yun Kuo
- Division of Evolutionary Biology, Faculty of Biology, Ludwig Maximilian University of Munich, Munich, Germany
| | | | - Chris D Jiggins
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
- Smithsonian Tropical Research Institute, Gamboa, Panama
| | - Stephen H Montgomery
- Smithsonian Tropical Research Institute, Gamboa, Panama
- School of Biological Science, University of Bristol, Bristol, United Kingdom
| | - Richard M Merrill
- Division of Evolutionary Biology, Faculty of Biology, Ludwig Maximilian University of Munich, Munich, Germany
- Smithsonian Tropical Research Institute, Gamboa, Panama
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Gates K, Sandoval-Castillo J, Brauer CJ, Unmack PJ, Laporte M, Bernatchez L, Beheregaray LB. Environmental selection, rather than neutral processes, best explain regional patterns of diversity in a tropical rainforest fish. Heredity (Edinb) 2023:10.1038/s41437-023-00612-x. [PMID: 36997655 DOI: 10.1038/s41437-023-00612-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 03/14/2023] [Accepted: 03/14/2023] [Indexed: 03/31/2023] Open
Abstract
AbstractTo conserve the high functional and genetic variation in hotspots such as tropical rainforests, it is essential to understand the forces driving and maintaining biodiversity. We asked to what extent environmental gradients and terrain structure affect morphological and genomic variation across the wet tropical distribution of an Australian rainbowfish, Melanotaenia splendida splendida. We used an integrative riverscape genomics and morphometrics framework to assess the influence of these factors on both putative adaptive and non-adaptive spatial divergence. We found that neutral genetic population structure was largely explainable by restricted gene flow among drainages. However, environmental associations revealed that ecological variables had a similar power to explain overall genetic variation, and greater power to explain body shape variation, than the included neutral covariables. Hydrological and thermal variables were the strongest environmental predictors and were correlated with traits previously linked to heritable habitat-associated dimorphism in rainbowfishes. In addition, climate-associated genetic variation was significantly associated with morphology, supporting heritability of shape variation. These results support the inference of evolved functional differences among localities, and the importance of hydroclimate in early stages of diversification. We expect that substantial evolutionary responses will be required in tropical rainforest endemics to mitigate local fitness losses due to changing climates.
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