Variation in reproductive isolation across a species range

Abstract

Reproductive isolation is often variable within species, a phenomenon that while largely ignored by speciation studies, can be leveraged to gain insight into the potential mechanisms driving the evolution of genetic incompatibilities. We used experimental greenhouse crosses to characterize patterns of reproductive isolation among three divergent genetic lineages of Campanulastrum americanum that occur in close geographic proximity in the Appalachian Mountains. Substantial, asymmetrical reproductive isolation for survival due to cytonuclear incompatibility was found among the lineages (up to 94% reduction). Moderate reductions in pollen viability, as well as cytoplasmic male sterility, were also found between some Mountain populations. We then compared these results to previously established patterns of reproductive isolation between these Mountain lineages and a fourth, widespread Western lineage to fully characterize reproductive isolation across the complete geographic and genetic range of C. americanum. Reproductive isolation for survival and pollen viability was consistent across studies, indicating the evolution of the underlying genetic incompatibilities is primarily determined by intrinsic factors. In contrast, reproductive isolation for germination was only found when crossing Mountain populations with the Western lineage, suggesting the underlying genetic incompatibility is likely influenced by environmental or demographic differences between the two lineages. Cytoplasmic male sterility was also limited in occurrence, being restricted to a handful of Mountain populations in a narrow geographic range. These findings illustrate the complexity of speciation by demonstrating multiple, independent genetic incompatibilities that lead to a mosaic of genetic divergence and reproductive isolation across a species range.

REFERENCES Barnard-Kubow, K. B., Debban, C. L., & Galloway, L. F. (2015). Multiple glacial refugia lead to genetic structuring and the potential for reproductive isolation in an herbaceous plant. American Journal of Botany, 102, 1842–1853. Barnard-Kubow, K. B., McCoy, M. A., & Galloway, L. F. (2017). Biparental chloroplast inheritance leads to rescue from cytonuclear incompatibility. New Phytologist, 213, 1466–1476. Barnard-Kubow, K. B., Sloan, D. B., & Galloway, L. F. (2014). Correlation between sequence divergence and polymorphism reveals similar evolutionary mechanisms acting across multiple timescales in a rapidly evolving plastid genome. BMC Evolutionary Biology, 14, 268. Barnard-Kubow, K. B., So, N., & Galloway, L. F. (2016). Cytonuclear incompatibility contributes to the early stages of speciation. Evolution, 70, 2752–2766. Bogdanova, V. S. (2007). Inheritance of organelle DNA markers in a pea cross associated with nuclear-cytoplasmic incompatibility. Theoretical and Applied Genetics, 114, 333–339. Brys, R., Broeck, A. V., Mergeay, J., & Jacquemyn, H. (2014). The contribution of mating system variation to reproductive isolation in two closely related Centarium species (Gentianaceae) with a generalized flower morphology. Evolution, 68, 1281–1293. Burton, R. S., Pereira, R. J., & Barreto, F. S. (2013). Cytonuclear genomic interactions and hybrid breakdown. Annual Review of Ecology, Evolution, and Systematics, 44, 281–302. Case, A. L., & Willis, J. H. (2008). Hybrid male sterility in Mimulus (Phrymaceae) is associated with a geographically restricted mitochondrial rearrangement. Evolution, 62, 1026–1039. Catchen, J. M., Amores, A., Hohenlohe, P., Cresko, W., & Postlethwait, J. H. (2011). Stacks: Building and genotyping loci de novo from short-read sequences. G3: Genes, Genomes, Genetics, 1, 171–182. Catchen, J., Hohenlohe, P. A., Bassham, S., Amores, A., & Cresko, W. A. (2013). Stacks: An analysis tool set for population genomics. Molecular Ecology, 22, 3124–3140. Charron, G., Leducq, J. B., & Landry, C. R. (2014). Chromosomal variation segregates within incipient species and correlates with reproductive isolation. Molecular Ecology, 23, 4362–4372. Chase, C. D. (2007). Cytoplasmic male sterility: A window to the world of plant mitochondrial-nuclear interactions. Trends in Genetics, 23, 81–90. Corbett-Detig, R. B., Zhou, J., Clark, A. G., Hartl, D. L., & Ayroles, J. F. (2013). Genetic incompatibilities are widespread within species. Nature, 504, 135. Coyne, J. A., & Orr, H. A. (2004). Speciation. Sunderland, MA: Sinauer Associates. Crespi, B., & Nosil, P. (2013). Conflictual speciation: Species formation via genomic conflict. Trends in Ecology & Evolution, 28, 48–57. Cutter, A. D. (2012). The polymorphic prelude to Bateson-Dobzhansky-Muller incompatibilities. Trends in Ecology & Evolution, 27, 209–218. Dobzhansky, T. (1937). Genetics and the origin of species. New York, NY: Columbia Univ. Press. Etterson, J. R., Keller, S. R., & Galloway, L. F. (2007). Epistatic and cytonuclear interactions govern outbreeding depression in the autotetraploid Campanulastrum americanum. Evolution, 61, 2671–2683. Fishman, L., & Willis, J. H. (2006). A cytonuclear incompatibility causes anther sterility in Mimulus hybrids. Evolution, 60, 1372–1381. Galloway, L. F., Cirigliano, T., & Gremski, K. (2002). The contribution of display size and dichogamy to potential geitonogamy in Campanula americana. International Journal of Plant Sciences, 163, 133–139. Galloway, L. F., & Etterson, J. R. (2005). Population differentiation and hybrid success in Campanula americana: Geography and genome size. Journal of Evolutionary Biology, 18, 81–89. Galloway, L. F., Etterson, J. R., & Hamrick, J. L. (2003). Outcrossing rate and inbreeding depression in the herbaceous autotetraploid, Campanula americana. Heredity, 90, 308–315. Garner, A. G., Kenney, A. M., Fishman, L., & Sweigart, A. L. (2016). Genetic loci with parent-of-origin effects cause hybrid seed lethality in crosses between Mimulus species. New Phytologist, 211, 319–331. Greiner, S., Rauwolf, U., Meurer, J., & Herrmann, R. G. (2011). The role of plastids in plant speciation. Molecular Ecology, 20, 671–691. Hill, G. E. (2016). Mitonuclear coevolution as the genesis of speciation and the mitochondrial DNA barcode gap. Ecology and Evolution, 6, 5831–5842. Johnson, N. A. (2002). Sixty years after “Isolating mechanisms, evolution and temperature”: Muller's legacy. Genetics, 161, 939–944. Johnson, S. G., Delph, L. F., & Elderkin, C. L. (1995). The effect of petal-size manipulation on pollen removal, seed set, and insect-visitor behavior in Campanula americana. Oecologia, 102, 174–179. Josefsson, C., Dilkes, B., & Comai, L. (2006). Parent-dependent loss of gene silencing during interspecies hybridization. Current Biology, 16, 1322–1328. Kearns, C. A., & Inouye, D. W. (1993). Techniques for pollination biologists. Niwot, Colorado: University Press of Colorado. Kirk, J. T. O., & Tilney-Bassett, R. A. E. (1978). The plastids, their chemistry, structure, growth, and inheritance. Amsterdam: Elsevier/North Holland Biomedical Press. Leppala, J., & Savolainen, O. (2011). Nuclear-cytoplasmic interactions reduce male fertility in hybrids of Arabidopsis lyrata subspecies. Evolution, 65, 2959–2972. Levin, D. A. (2003). The cytoplasmic factor in plant speciation. Systematic Botany, 28, 5–11. Levy, F. (1991). A genetic analysis of reproductive barriers in Phacelia dubia. Heredity, 67, 331–345. Lowry, D. B., Modliszewski, J. L., Wright, K. M., Wu, C. A., & Willis, J. H. (2008). The strength and genetic basis of reproductive isolating barriers in flowering plants. Philosophical Transactions of the Royal Society B-Biological Sciences, 363, 3009–3021. Martin, H., Touzet, P., Dufay, M., Gode, C., Schmitt, E., Lahiani, E., … Van Rossum, F. (2017). Lineages of Silene nutans developed rapid, strong, asymmetric postzygotic reproductive isolation in allopatry. Evolution, 71, 1519–1531. Martin, N. H., & Willis, J. H. (2010). Geographical variation in postzygotic isolation and its genetic basis within and between two Mimulus species. Philosophical Transactions of the Royal Society B-Biological Sciences, 365, 2469–2478. Matute, D. R., Gavin-Smyth, J., & Liu, G. (2014). Variable post-zygotic isolation in Drosophila melanogaster/D. simulans hybrids. Journal of Evolutionary Biology, 27, 1691–1705. Muller, H. J. (1942). Isolating mechanisms, evolution and temperature. Biological Symposia, 6, 71–125. Nosil, P. (2012). Ecological speciation. New York, NY: Oxford University Press, Oxford. Orr, H. A. (1995). The population-genetics of speciation – the evolution of hybrid incompatibilities. Genetics, 139, 1805–1813. Peterson, D. L., Kubow, K. B., Connolly, M. J., Kaplan, L. R., Wetkowski, M. M., Leong, W., … Edmands, S. (2013). Reproductive and phylogenetic divergence of tidepool copepod populations across a narrow geographical boundary in Baja California. Journal of Biogeography, 40, 1664–1675. Petit, R. J., Duminil, J., Fineschi, S., Hampe, A., Salvini, D., & Vendramin, G. G. (2005). Comparative organization of chloroplast, mitochondrial and nuclear diversity in plant populations. Molecular Ecology, 14, 689–701. Pinheiro, F., Cozzolino, S., de Barros, F., Gouveia, T. M. Z. M., Suzuki, R. M., Fay, M. F., & Palma-Silva, C. (2013). Phylogeographic structure and outbreeding depression reveal early stages of reproductive isolation in the neotropical orchid Epidendrum denticulatum. Evolution, 67, 2024–2039. Ramsey, J., Bradshaw, H. D., & Schemske, D. W. (2003). Components of reproductive isolation between the monkeyflowers Mimulus lewisii and M. cardinalis (Phrymaceae). Evolution, 57, 1520–1534. Rebernig, C. A., Lafon-Placette, C., Hatorangan, M. R., Slotte, T., & Köhler, C. (2015). Non-reciprocal interspecies hybridization barriers in the Capsella genus are established in the endosperm. PLoS Genetics, 11, e1005295. Sambatti, J. B. M., Strasburg, J. L., Ortiz-Barrientos, D., Baack, E. J., & Rieseberg, L. H. (2012). Reconciling extremely strong barriers with high levels of gene exchange in annual sunflowers. Evolution, 66, 1459–1473. SAS Institute Inc. 2011. Base SAS® 9.3 Procedures Guide: Statistical Procedures. Cary, NC, USA: SAS Institute Inc. Scopece, G., Lexer, C., Widmer, A., & Cozzolino, S. (2010). Polymorphism of postmating reproductive isolation within plant species. Taxon, 59, 1367–1374. Scopece, G., Widmer, A., & Cozzolino, S. (2008). Evolution of postzygotic reproductive isolation in a guild of deceptive orchids. The American Naturalist, 171, 315–326. Skrede, I., Brochmann, C., Borgen, L., & Rieseberg, L. H. (2008). Genetics of intrinsic postzygotic isolation in a circumpolar plant species, Draba nivalis (Brassicaceae). Evolution, 62, 1840–1851. Snoek, L. B., Orbidans, H. E., Stastna, J. J., Aartse, A., Rodriguez, M., Riksen, J. A. G., … Harvey, S. C. (2014). Widespread genomic incompatibilities in Caenorhabditis elegans. G3-Genes Genomes. Genetics, 4, 1813–1823. Sobel, J. M., Chen, G. F., Watt, L. R., & Schemske, D. W. (2010). The biology of speciation. Evolution, 64, 295–315. Stamatakis, A. (2014). RAxML version 8: A tool for phylogenetic analysis and post-analysis of large phylogenies. Bioinformatics, 30, 1312–1313. Sweigart, A. L., Mason, A. R., & Willis, J. H. (2007). Natural variation for a hybrid incompatibility between two species of Mimulus. Evolution, 61, 141–151. Sweigart, A. L., & Willis, J. H. (2012). Molecular evolution and genetics of postzygotic reproductive isolation in plants. F1000 Biology Reports, 4, 23. Turelli, M., & Moyle, L. C. (2007). Asymmetric postmating isolation: Darwin's corollary to Haldane's rule. Genetics, 176, 1059–1088. Ureshino, K., Miyajima, I., Ozaki, Y., Kobayashi, N., Michishita, A., & Akabane, M. (1999). Appearance of albino seedlings and ptDNA inheritance in interspecific hybrids of azalea. Euphytica, 110, 61–66. Weihe, A., Apitz, J., Pohlheim, F., Salinas-Hartwig, A., & Borner, T. (2009). Biparental inheritance of plastidial and mitochondrial DNA and hybrid variegation in Pelargonium. Molecular Genetics and Genomics, 282, 587–593.