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Lackey ACR, Murray AC, Mirza NA, Powell THQ. The role of sexual isolation during rapid ecological divergence: Evidence for a new dimension of isolation in Rhagoletis pomonella. J Evol Biol 2023. [PMID: 37173822 DOI: 10.1111/jeb.14179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 03/05/2023] [Accepted: 03/23/2023] [Indexed: 05/15/2023]
Abstract
The pace of divergence and likelihood of speciation often depends on how and when different types of reproductive barriers evolve. Questions remain about how reproductive isolation evolves after initial divergence. We tested for the presence of sexual isolation (reduced mating between populations due to divergent mating preferences and traits) in Rhagoletis pomonella flies, a model system for incipient ecological speciation. We measured the strength of sexual isolation between two very recently diverged (~170 generations) sympatric populations, adapted to different host fruits (hawthorn and apple). We found that flies from both populations were more likely to mate within than between populations. Thus, sexual isolation may play an important role in reducing gene flow allowed by early-acting ecological barriers. We also tested how warmer temperatures predicted under climate change could alter sexual isolation and found that sexual isolation was markedly asymmetric under warmer temperatures - apple males and hawthorn females mated randomly while apple females and hawthorn males mated more within populations than between. Our findings provide a window into the early speciation process and the role of sexual isolation after initial ecological divergence, in addition to examining how environmental conditions could shape the likelihood of further divergence.
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Affiliation(s)
- Alycia C R Lackey
- University of Louisville, Louisville, Kentucky, USA
- Binghamton University, Binghamton, New York, USA
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Enriquez MS, Swanson N, Putland RL, Tait T, Gluesenkamp AG, McGaugh SE, Mensinger AF. Evidence for rapid divergence of sensory systems between Texas populations of the Mexican tetra (Astyanax mexicanus). Front Ecol Evol 2023. [DOI: 10.3389/fevo.2023.1085975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023] Open
Abstract
Population divergence is often quantified using phenotypic variation. However, because sensory abilities are more difficult to discern, we have little information on the plasticity and rate of sensory change between different environments. The Mexican tetra (Astyanax mexicanus) is a fish distributed throughout Southern Texas and Northern Mexico and has evolved troglomorphic phenotypes, such as vestigial eyes and reduced pigmentation, when surface ancestors invaded caves in the past several hundred thousand years. In the early 1900s, surface A. mexicanus were introduced to the karstic Edwards-Trinity Aquifer in Texas. Subsequent cave colonization of subterranean environments resulted in fish with phenotypic and behavioral divergence from their surface counterparts, allowing examination of how new environments lead to sensory changes. We hypothesized that recently introduced cave populations would be more sensitive to light and sound when compared to their surface counterparts. We quantified divergence using auditory evoked potentials (AEPs) and particle acceleration levels (PALs) to measure differences in sound sensitivity, and electroretinography (ERGs) to measure light sensitivity. We also compared these results to measurements taken from native populations and lab-born individuals of the introduced populations. Honey Creek Cave fish were significantly more sensitive than proximate Honey Creek surface fish to sound pressure levels between 0.6 and 0.8 kHz and particle acceleration levels between 0.4 and 0.8 kHz. Pairwise differences were found between San Antonio Zoo surface and the facultative subterranean San Pedro Springs and Blue Hole populations, which exhibited more sensitivity to particle acceleration levels between 0.5 and 0.7 kHz. Electroretinography results indicate no significant differences between populations, although Honey Creek Cave fish may be trending toward reduced visual sensitivity. Auditory thresholds between wild-caught and lab-raised populations of recently invaded fish show significant differences in sensitivity, suggesting that these traits are plastic. Collectively, while these results may point to the rapid divergence of A. mexicanus in cave habitats, it also highlights the responsive plasticity of A. mexicanus auditory system to disparate environments.
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Kharva H, Feder JL, Hahn DA, Olsson SB. Rapid brain development and reduced neuromodulator titres correlate with host shifts in Rhagoletis pomonella. ROYAL SOCIETY OPEN SCIENCE 2022; 9:220962. [PMID: 36117862 PMCID: PMC9449811 DOI: 10.1098/rsos.220962] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 08/16/2022] [Indexed: 05/27/2023]
Abstract
Host shifts are considered a key generator of insect biodiversity. For insects, adaptation to new host plants often requires changes in larval/pupal development and adult behavioural preference toward new hosts. Neurochemicals play key roles in both development and behaviour and therefore provide a potential source for such synchronization. Here, we correlated life-history timing, brain development and corresponding levels of 14 neurochemicals in Rhagoletis pomonella (Diptera: Tephritidae), a species undergoing ecological speciation through an ongoing host shift from hawthorn to apple fruit. These races exhibit differences in pupal diapause timing as well as adult behavioural preference with respect to their hosts. This difference in behavioural preference is coupled with differences in neurophysiological response to host volatiles. We found that apple race pupae exhibited adult brain morphogenesis three weeks faster after an identical simulated winter than the hawthorn race, which correlated with significantly lower titres of several neurochemicals. In some cases, particularly biogenic amines, differences in titres were reflected in the mature adult stage, when host preference is exhibited. In summary, life-history timing, neurochemical titre and brain development can be coupled in this speciating system, providing new hypotheses for the origins of new species through host shifts.
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Affiliation(s)
- Hinal Kharva
- Naturalist-Inspired Chemical Ecology lab, National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore 560065, India
- School of Life Sciences, The University of Trans-Disciplinary Health Sciences and Technology, 74/2, Jarakabande Kaval, Post Attur via Yelahanka, Bangalore 560064, India
| | - Jeffrey L. Feder
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Daniel A. Hahn
- Department of Entomology and Nematology, University of Florida, Gainesville, FL 32611, USA
| | - Shannon B. Olsson
- Naturalist-Inspired Chemical Ecology lab, National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore 560065, India
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Tait C, Kharva H, Schubert M, Kritsch D, Sombke A, Rybak J, Feder JL, Olsson SB. A reversal in sensory processing accompanies ongoing ecological divergence and speciation in Rhagoletis pomonella. Proc Biol Sci 2021; 288:20210192. [PMID: 33757346 DOI: 10.1098/rspb.2021.0192] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Changes in behaviour often drive rapid adaptive evolution and speciation. However, the mechanistic basis for behavioural shifts is largely unknown. The tephritid fruit fly Rhagoletis pomonella is an example of ecological specialization and speciation in action via a recent host plant shift from hawthorn to apple. These flies primarily use specific odours to locate fruit, and because they mate only on or near host fruit, changes in odour preference for apples versus hawthorns translate directly to prezygotic reproductive isolation, initiating speciation. Using a variety of techniques, we found a reversal between apple and hawthorn flies in the sensory processing of key odours associated with host fruit preference at the first olfactory synapse, linking changes in the antennal lobe of the brain with ongoing ecological divergence. Indeed, changes to specific neural pathways of any sensory modality may be a broad mechanism for changes in animal behaviour, catalysing the genesis of new biodiversity.
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Affiliation(s)
- Cheyenne Tait
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Hinal Kharva
- Naturalist-Inspired Chemical Ecology, National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore 560065, India.,School of Life Sciences, The University of Trans-Disciplinary Health Sciences and Technology, 74/2, Jarakabande Kaval, Post Attur via Yelahanka, Bangalore 560064, India
| | - Marco Schubert
- Department of Biology, Chemistry and Pharmacy, Institute of Biology, Free University Berlin, Berlin 14195, Germany
| | - Daniel Kritsch
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans Knöll Strasse 8, Jena 07745, Germany
| | - Andy Sombke
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans Knöll Strasse 8, Jena 07745, Germany
| | - Jürgen Rybak
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans Knöll Strasse 8, Jena 07745, Germany
| | - Jeffrey L Feder
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Shannon B Olsson
- Naturalist-Inspired Chemical Ecology, National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore 560065, India
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