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Larson EL, Brassil MM, Maslan J, Juárez D, Lilagan F, Tipton H, Schweitzer A, Skillman J, Monsen-Collar KJ, Peterson MA. The effects of heterospecific mating frequency on the strength of cryptic reproductive barriers. J Evol Biol 2019; 32:900-912. [PMID: 31162735 DOI: 10.1111/jeb.13495] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Revised: 05/22/2019] [Accepted: 05/28/2019] [Indexed: 01/02/2023]
Abstract
Heterospecific mating frequency is critical to hybrid zone dynamics and can directly impact the strength of reproductive barriers and patterns of introgression. The effectiveness of post-mating prezygotic (PMPZ) reproductive barriers, which include reduced fecundity via heterospecific matings and conspecific sperm precedence, may depend on the number, identity and order of mates. Studies of PMPZ barriers suggest that they may be important in many systems, but whether these barriers are effective at realistic heterospecific mating frequencies has not been tested. Here, we evaluate the strength of cryptic reproductive isolation in two leaf beetles (Chrysochus auratus and C. cobaltinus) in the context of a range of heterospecific mating frequencies observed in natural populations. We found both species benefited from multiple matings, but the benefits were greater in C. cobaltinus and extended to heterospecific matings. We found that PMPZ barriers greatly limited hybrid production by C. auratus females with moderate heterospecific mating frequencies, but that their effectiveness diminished at higher heterospecific mating frequencies. In contrast, there was no evidence for PMPZ barriers in C. cobaltinus females at any heterospecific mating frequency. We show that integrating realistic estimates of cryptic isolation with information on relative abundance and heterospecific mating frequency in the field substantially improves our understanding of the strong directional bias in F1 production previously documented in the Chrysochus hybrid zone. Our results demonstrate that heterospecific mating frequency is critical to understanding the impact of cryptic post-copulatory barriers on hybrid zone structure and dynamics, and that future studies of such barriers should incorporate field-relevant heterospecific mating frequencies.
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Affiliation(s)
- Erica L Larson
- Department of Biological Sciences, University of Denver, Denver, Colorado, USA.,Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Margaret M Brassil
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Jonathan Maslan
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Danielle Juárez
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Flordeliza Lilagan
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Hallie Tipton
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Andrew Schweitzer
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Joe Skillman
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | | | - Merrill A Peterson
- Biology Department, Western Washington University, Bellingham, Washington, USA
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Castillo DM, Moyle LC. Conspecific sperm precedence is reinforced, but postcopulatory sexual selection weakened, in sympatric populations of Drosophila. Proc Biol Sci 2019; 286:20182535. [PMID: 30900533 PMCID: PMC6452082 DOI: 10.1098/rspb.2018.2535] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 03/06/2019] [Indexed: 12/21/2022] Open
Abstract
Sexual selection can accelerate speciation by driving the evolution of reproductive isolation, but forces driving speciation could also reciprocally feedback on sexual selection. This might be particularly important in the context of 'reinforcement', where selection acts directly to increase prezygotic barriers to reduce the cost of heterospecific matings. Using assays of sperm competition within and between two sister species, we show a signature of reinforcement where these species interact: populations of Drosophila pseudoobscura that co-occur with sister species D. persimilis have an elevated ability to outcompete heterospecific sperm, consistent with selection for increased postcopulatory isolation. We also find these D. pseudoobscura populations have decreased sperm competitive ability against conspecifics, reducing the opportunity for sexual selection within these populations. Our findings demonstrate that direct selection to increase reproductive isolation against other species can compromise the efficacy of sexual selection within species, a collateral effect of reproductive traits responding to heterospecific interactions.
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Affiliation(s)
- Dean M. Castillo
- Department of Biology, Indiana University, 1001 East Third Street, Bloomington, IN 47405, USA
- Department of Molecular Biology and Genetics, Cornell University, 526 Campus Road, Ithaca, NY 14853, USA
| | - Leonie C. Moyle
- Department of Biology, Indiana University, 1001 East Third Street, Bloomington, IN 47405, USA
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Detwiler KM. Mitochondrial DNA Analyses of Cercopithecus Monkeys Reveal a Localized Hybrid Origin for C. mitis doggetti in Gombe National Park, Tanzania. INT J PRIMATOL 2018. [DOI: 10.1007/s10764-018-0029-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Mitchell SM, Muehlbauer LK, Freedberg S. Nuclear introgression without mitochondrial introgression in two turtle species exhibiting sex-specific trophic differentiation. Ecol Evol 2016; 6:3280-8. [PMID: 27252833 PMCID: PMC4870212 DOI: 10.1002/ece3.2087] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 02/15/2016] [Accepted: 02/22/2016] [Indexed: 12/24/2022] Open
Abstract
Despite the presence of reproductive barriers between species, interspecific gene introgression has been documented in a range of natural systems. Comparing patterns of genetic introgression in biparental versus matrilineal markers can potentially reveal sex-specific barriers to interspecific gene flow. Hybridization has been documented in the freshwater turtles Graptemys geographica and G. pseudogeographica, whose ranges are largely sympatric. Morphological differentiation between the species is restricted to females, with female G. geographica possessing large heads and jaws compared to the narrow heads of G. pseudogeographica females. If hybrid females are morphologically intermediate, they may be less successful at exploiting parental feeding niches, thereby limiting the introgression of maternally inherited, but not biparental, molecular markers. We paired sequence data with stable isotope analysis and examined sex-specific genetic introgression and trophic differentiation in sympatric populations of G. geographica and G. pseudogeographica. We observed introgression from G. pseudogeographica into G. geographica at three nuclear loci, but not at the mitochondrial locus. Analysis of ∂(15)N and ∂(13)C was consistent with species differences in trophic positioning in females, but not males. These results suggest that ecological divergence in females may reduce the opportunity for gene flow in this system.
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Affiliation(s)
- Sarah M Mitchell
- Department of Ecology, Evolution, and Organismal Biology Iowa State University Ames Iowa 50011-1020
| | - Laura K Muehlbauer
- Department of Biology St. Olaf College 1520 St. Olaf Avenue Northfield Minnesota 55057
| | - Steven Freedberg
- Department of Biology St. Olaf College 1520 St. Olaf Avenue Northfield Minnesota 55057
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Noncompetitive Gametic Isolation between Sibling Species of Cricket: A Hypothesized Link between Within-Population Incompatibility and Reproductive Isolation between Species. INTERNATIONAL JOURNAL OF EVOLUTIONARY BIOLOGY 2012; 2012:593438. [PMID: 23251826 PMCID: PMC3517841 DOI: 10.1155/2012/593438] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 10/20/2012] [Accepted: 10/22/2012] [Indexed: 11/18/2022]
Abstract
Postmating, prezygotic phenotypes are a common mechanism of reproductive isolation. Here, we describe the dynamics of a noncompetitive gametic isolation phenotype (namely, the ability of a male to induce a female to lay eggs) in a group of recently diverged crickets that are primarily isolated from each other by this phenotype. We not only show that heterospecific males are less able to induce females to lay eggs but that there are male by female incompatibilities in this phenotype that occur within populations. We also identify a protein in the female reproductive tract that correlates with the number of eggs that she was induced to lay. Functional genetic tests using RNAi confirm that the function of this protein is linked to egg-laying induction. Moreover, the dysfunction of this protein appears to underlie both within-population incompatibilities and between-species divergence—thus suggesting a common genetic pathway underlies both. However, this is only correlative evidence and further research is needed to assess whether or not the same mutations in the same genes underlie variation at both levels.
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