In the species-rich genus Impatiens, few natural hybrids are known, even though closely related species often occur sympatrically. In this study, we aim to bridge the gap between micro- and macro-evolution to disentangle pre- and postzygotic mechanisms that may prevent hybridization in the Impatiens purpureoviolacea complex from Central Africa. We analyzed habitat types, species distribution, pollination syndromes, pollinator dependency, genome sizes, and chromosome numbers of seven out of the ten species of the complex as well as of one natural hybrid and reconstructed the ancestral chromosome numbers of the complex. Several species of the complex occur in sympatry or geographically very close to each other. All of them are characterized by pre- and/or postzygotic mechanisms potentially preventing hybridization. We found four independent polyploidization events within the complex. The only known natural hybrid always appears as single individual and is self-fertile. But the plants resulting from self-pollinated seeds often die shortly after first flowering. These results indicate that the investigated mechanisms in combination may effectively but not absolutely prevent hybridization in Impatiens and probably occur in other genera with sympatric species as well.

Department of Biology Institute of Botany and Microbiology KU Leuven Leuven Belgium

Department of Botany Faculty of Science Charles University Prague Czech Republic

Institut für Integrierte Naturwissenschaften Biologie Universität Koblenz Landau Koblenz Germany

Institute of Botany The Czech Academy of Sciences Průhonice Czech Republic

Meise Botanic Garden Meise Belgium

Natural History Museum London UK

Nees Institute for Biodiversity of Plants University of Bonn Bonn Germany

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Abbott, R. , Albach, D. , Ansell, S. , Arntzen, J. W. , Baird, S. J. , Bierne, N. , Boughman, J. , Brelsford, A. , Buerkle, C. A. , Buggs, R. , Butlin, R. K. , Dieckmann, U. , Eroukhmanoff, F. , Grill, A. , Cahan, S. H. , Hermansen, J. S. , Hewitt, G. , Hudson, A. G. , Jiggins, C. , … Zinner, D. (2013). Hybridization and speciation. Journal of Evolutionary Biology, 26, 229–246. 10.1111/j.1420-9101.2012.02599.x PubMed DOI

Abrahamczyk, S. , Lozada‐Gobilard, S. , Ackermann, M. , Fischer, E. , Krieger, V. , Redling, A. , & Weigend, M. (2017). A question of data quality: Testing pollination syndromes in Balsaminaceae. PLoS One, 12, e0186125. 10.1371/journal.pone.0186125 PubMed DOI PMC

Araújo, E. D. , Costa, M. , Chaud‐Netto, J. , & Fowler, H. G. (2004). Body size and flight distance in stingless bees (Hymenoptera: Meliponini): Inference of flight range and possible ecological implications. Brazilian Journal of Biology, 64, 563–568. 10.1590/S1519-69842004000400003 PubMed DOI

Arnold, M. L. (1997). Natural hybridization and evolution. Oxford University Press.

Bartha, L. , Dragoş, N. , Molnár, V. A. , & Sramkó, G. (2013). Molecular evidence for reticulate speciation in Astragalus (Fabaceae) as revealed by a case study from sect. Dissitiflori . Botany‐Botanique, 91, 702–714.

Belyayev, A. , Paštová, L. , Fehrer, J. , Josefiová, J. , Chrtek, J. , & Mráz, P. (2018). Mapping of Hieracium (Asteraceae) chromosomes with genus‐specific satDNA elements derived from next generation sequencing data. Plant Systematic and Evolution, 304, 387–396. 10.1007/s00606-017-1483-y DOI

Birchler, J. A. (2014). Interploidy hybridization barrier of endosperm as a dosage interaction. Frontiers in Plant Science, 5, 281. 10.3389/fpls.2014.00281 PubMed DOI PMC

Bradshaw, H. D. Jr. , & Schemske, D. W. (2003). Allele substitution at a flower colour locus produces a pollinator shift in monkeyflowers. Nature, 426, 176–178. 10.1038/nature02106 PubMed DOI

Cai, L. , Xi, Z. , Amorim, A. M. , Sugumaran, M. , Rest, J. S. , Liu, L. , & Davis, C. C. (2019). Widespread ancient whole‐genome duplications in Malpighiales coincide with Eocene global climatic upheaval. New Phytologist, 221, 565–576. 10.1111/nph.15357 PubMed DOI PMC

Doležel, J. , Greilhuber, J. , Lucretti, S. , Meister, A. , Lysák, M. A. , Nardi, L. , & Obermayer, R. (1998). Plant genome size estimation by flow cytometry: Inter‐laboratory comparison. Annals of Botany, 82, 17–26. 10.1093/oxfordjournals.aob.a010312 DOI

Doležel, J. , Greilhuber, J. , & Suda, J. (2007). Estimation of nuclear DNA content in plants using flow cytometry. Nature Protocols, 2, 2233–2244. 10.1038/nprot.2007.310 PubMed DOI

Escudero, M. , Hipp, A. L. , Waterway, M. J. , & Valente, L. M. (2012). Diversification rates and chromosome evolution in the most diverse angiosperm genus of the temperate zone (Carex, Cyperaceae). Molecular Phylogenetics and Evolution, 63, 650–655. 10.1016/j.ympev.2012.02.005 PubMed DOI

Fischer, E. , Abrahamczyk, S. , Holstein, N. , & Janssens, S. B. (2021). Evolution of Impatiens (Balsaminaceae) in the Albertine Rift—The endemic Impatiens purpureoviolacea complex consists of ten species. Taxon. 10.1002/tax.12566 DOI

Gadella, T. W. J. (1977). In IOPB chromosome number reports LVI. Taxon, 26, 257–274. 10.1002/j.1996-8175.1977.tb04167.x DOI

Gadella, T. W. (1982). IOPB chromosome number reports LXXVI. Taxon, 31, 595–596.

Gill, L. S. , & Chinnappa, C. C. (1977). Chromosome numbers from herbarium sheets in some Tanzanian Impatiens L. (Balsaminaceae). Caryologia, 30, 375–379.

Glennon, K. L. , Rissler, L. J. , & Church, S. A. (2012). Ecogeographic isolation: A reproductive barrier between species and between cytotypes in Houstonia (Rubiaceae). Evolutionary Ecology, 26, 909–926. 10.1007/s10682-011-9539-x DOI

Glick, L. , & Mayrose, I. (2014). ChromEvol: Assessing the pattern of chromosome number evolution and the inference of polyploidy along a phylogeny. Molecular Biology and Evolution, 31, 1914–1922. 10.1093/molbev/msu122 PubMed DOI

Grey‐Wilson, C. (1980a). Impatiens of Africa. Balkema.

Grey‐Wilson, C. (1980b). Hybridization in African Impatiens: Studies in Balsaminaceae: II. Kew Bulletin, 34, 689–722. 10.2307/4119063 DOI

Grey‐Wilson, C. (1980c). Notes on east African Impatiens: Studies in Balsaminaceae: III. Kew Bulletin, 35, 173–201. 10.2307/4117014 DOI

Grimshaw, J. M. , & Grey‐Wilson, C. (1997). Impatiens kilimanjari subspecies pocsii Balsaminaceae. Curtis's Botanical Magazine, 14, 23–30.

Han, T. S. , Zheng, Q. J. , Onstein, R. E. , Rojas‐Andrés, B. M. , Hauenschild, F. , Muellner‐Riehl, A. N. , & Xing, Y. W. (2020). Polyploidy promotes species diversification of Allium through ecological shifts. New Phytologist, 225, 571–583. PubMed

Husband, B. C. , & Sabara, H. A. (2004). Reproductive isolation between autotetraploids and their diploid progenitors in fireweed, Chamerion angustifolium . New Phytologist, 161, 713. PubMed

Janeček, Š. , Bartoš, M. , & Njabo, K. Y. (2015). Convergent evolution of sunbird pollination systems of Impatiens species in tropical Africa and hummingbird systems of the New World. Biological Journal of the Linnean Society, 115, 127–133.

Janssens, S. B. , Knox, E. B. , Huysmans, S. , Smets, E. F. , & Merckx, V. S. (2009). Rapid radiation of Impatiens (Balsaminaceae) during Pliocene and Pleistocene: Result of a global climate change. Molecular Phylogenetics and Evolution, 52, 806–824. 10.1016/j.ympev.2009.04.013 PubMed DOI

Jeelani, S. M. , Rani, S. , Kumar, S. , Gupta, R. C. , & Kumari, S. (2010). Cytomorphological diversity in some species of Impatiens Linn. (Balsaminaceae) from Western Himalayas (India). Cytologia, 75, 379–387. 10.1508/cytologia.75.379 DOI

Johnson, L. A. , & Soltis, D. E. (1998). Assessing congruence: Empirical examples from molecular data. In Soltis D. E., Soltis P. S., & Doyle J. J. (Eds.), Molecular systematics of plants II (pp. 297–348). Springer.

Jones, K. , & Smith, J. B. (1966). The cytogeography of Impatiens L. (Balsaminaceae). Kew Bulletin, 20, 63–72. 10.2307/4107885 DOI

Karrenberg, S. , Liu, X. , Hallander, E. , Favre, A. , Herforth‐Rahmé, J. , & Widmer, A. (2019). Ecological divergence plays an important role in strong but complex reproductive isolation in campions (Silene). Evolution, 73, 245–261. PubMed

Kato, M. , Itino, T. , Hotta, M. , & Inoue, T. (1991). Pollination of four Sumatran Impatiens species by hawkmoths and bees. Tropics, 1, 59–73. 10.3759/tropics.1.59 DOI

Katoh, K. , Misawa, K. , Kuma, K. , & Miyata, T. (2002). MAFFT: A novel method for rapid multiple sequence alignment based on fast Fourier transform. Nucleic Acids Research, 30, 3059–3066. 10.1093/nar/gkf436 PubMed DOI PMC

Lafon‐Placette, C. , & Köhler, C. (2016). Endosperm‐based postzygotic hybridization barriers: Developmental mechanisms and evolutionary drivers. Molecular Ecology, 25, 2620–2629. PubMed

Lee, C. B. , Page, L. E. , McClure, B. A. , & Holtsford, T. P. (2008). Post‐pollination hybridization barriers in Nicotiana section Alatae . Sexual Plant Reproduction, 21, 183–195. 10.1007/s00497-008-0077-9 DOI

Liang, H. , Ren, Z. X. , Tao, Z. B. , Zhao, Y. H. , Bernhardt, P. , & Wang, H. (2018). Impact of pre‐ and post‐pollination barriers on pollen transfer and reproductive isolation among three sympatric Pedicularis species. Plant Biology, 20, 662–673. PubMed

Lozada‐Gobilard, S. , Weigend, M. , Fischer, E. , Janssens, S. B. , Ackermann, M. , & Abrahamczyk, S. (2019). Breeding systems in Balsaminaceae in relation to pollen/ovule ratio, pollination syndromes, life history and climate zone. Plant Biology, 21, 157–166. 10.1111/plb.12905 PubMed DOI

Lumaret, R. , Guillerm, J. L. , Delay, J. , Loutfi, A. A. L. , Izco, J. , & Jay, M. (1987). Polyploidy and habitat differentiation in Dactylis glomerata L. from Galicia (Spain). Oecologia, 73, 436–446. PubMed

Merlin, C. M. , & Grant, W. F. (1986). Hybridization studies in the genus Impatiens . Canadian Journal of Botany, 64, 1069–1074.

Morgan, R. J. (2007). Impatiens: The vibrant world of busy lizzies, balsams, and touch‐me‐nots. Timber Press.

Mota, L. , Torices, R. , & Loureiro, J. (2016). The evolution of haploid chromosome numbers in the sunflower family. Genome Biology and Evolution, 8, 3516–3528. 10.1093/gbe/evw251 PubMed DOI PMC

Mouly, A. , Razafimandimbison, S. G. , Khodabandeh, A. , & Bremer, B. (2009). Phylogeny and classification of the species‐rich pantropical showy genus Ixora (Rubiaceae ‐ Ixoreae) with indications of geographical monophyletic units and hybrids. American Journal of Botany, 96, 686–706. PubMed

Neri, J. , Wendt, T. , Leles, B. , Dos Santos, M. F. , & Palma‐Silva, C. (2017). Variation in reproductive systems facilitates species boundaries of sympatric Vriesea (Bromeliaceae). Botanical Journal of the Linnean Society, 184, 272–279. 10.1093/botlinnean/box026 DOI

Oginuma, K. , & Tobe, H. (1991). Karyomorphology of two species of Impatiens from Kenya. Acta Phytotaxonomica Et Geobotanica, 42, 67–71.

Ornduff, R. (1967). Hybridization and regional variation in Pacific northwestern Impatiens (Balsaminaceae). Brittonia, 19, 122–128. 10.2307/2805269 DOI

Otto, F. (1990). DAPI staining of fixed cells for high‐resolution flow cytometry of nuclear DNA. In Crissman H. A., & Darzynkiewicz Z. (Eds.), Methods in cell biology (vol. 33, pp. 105–110). Academic Press. PubMed

Pijnacker, L. P. , & Ferwerda, M. A. (1984). Giemsa C‐banding of potato chromosomes. Canadian Journal of Genetics and Cytology, 26, 415–419. 10.1139/g84-067 DOI

Pirie, M. D. (2015). Phylogenies from concatenated data: Is the end nigh? Taxon, 64, 421–423. 10.12705/643.1 DOI

Posada, D. (2008). jModelTest: Phylogenetic model averaging. Molecular Biology and Evolution, 25, 1253–1256. PubMed

R Development Core Team . (2017). R: A language and environment for statistical computing. R Foundation for Statistical Computing.

Rambaut, A. , Suchard, M. A. , Xie, D. , & Drummond, A. J. (2014). TRACER vv 1.6. http://beast.bio.ed.ac.uk/Tracer

Ramsey, J. (2011). Polyploidy and ecological adaptation in wild yarrow. Proceedings of the National Academy of Sciences, 108, 7096–7101. 10.1073/pnas.1016631108 PubMed DOI PMC

Ramsey, J. , & Schemske, D. W. (1998). Pathways, mechanisms, and rates of polyploid formation in flowering plants. Annual Review of Ecology and Systematics, 29, 467–501.

Ruchisansakun, S. , Tangtorwongsakul, P. , Cozien, R. J. , Smets, E. F. , & van der Niet, T. (2016). Floral specialization for different pollinators and divergent use of the same pollinator among co‐occurring Impatiens species (Balsaminaceae) from Southeast Asia. Botanical Journal of the Linnean Society, 181, 651–666.

Seehausen, O. , Butlin, R. K. , Keller, I. , Wagner, C. E. , Boughman, J. W. , Hohenlohe, P. A. , Peichel, C. L. , Saetre, G.‐P. , Bank, C. , Brännström, Å. , Brelsford, A. , Clarkson, C. S. , Eroukhmanoff, F. , Feder, J. L. , Fischer, M. C. , Foote, A. D. , Franchini, P. , Jiggins, C. D. , Jones, F. C. , … Widmer, A. (2014). Genomics and the origin of species. Nature Reviews Genetics, 15, 176–192. 10.1038/nrg3644 PubMed DOI

Sobel, J. M. , & Chen, G. F. (2014). Unification of methods for estimating the strength of reproductive isolation. Evolution, 68, 1511–1522. 10.1111/evo.12362 PubMed DOI

Sobel, J. M. , Chen, G. F. , Watt, L. R. , & Schemske, D. W. (2010). The biology of speciation. Evolution, 64, 295–315. 10.1111/j.1558-5646.2009.00877.x PubMed DOI

Soltis, P. S. , & Soltis, D. E. (2009). The role of hybridization in plant speciation. Annual Review of Plant Biology, 60, 561–588. 10.1146/annurev.arplant.043008.092039 PubMed DOI

Song, Y. , Yuan, Y. M. , & Küpfer, P. (2003). Chromosomal evolution in Balsaminaceae, with cytological observations on 45 species from Southeast Asia. Caryologia, 56, 463–481. 10.1080/00087114.2003.10589359 DOI

Stamatakis, A. , Ludwig, T. , & Meier, H. (2005). RAxML III: A fast program for maximum likelihood‐based inference of large phylogenetic trees. Bioinformatics, 21, 456–463. 10.1093/bioinformatics/bti191 PubMed DOI

Suchard, M. A. , Lemey, P. , Baele, G. , Ayres, D. L. , Drummond, A. J. , & Rambaut, A. (2018). Bayesian phylogenetic and phylodynamic data integration using BEAST 1.10 Virus. Evolution, 4, vey016. 10.1093/ve/vey016 PubMed DOI PMC

Temsch, E. M. , Greilhuber, J. , & Krisai, R. (2010). Genome size in liverworts. Preslia, 82, 63–80.

Thiers, B. (2014). Index Herbariorum: A global directory of public herbaria and associate staff. New York Botanical Garden's Virtual Herbarium, Bronx, NY, USA [Accessed October, 2021].

Townsend, P. A. , & Levey, D. J. (2005). An experimental test of whether habitat corridors affect pollen transfer. Ecology, 86, 466–475. 10.1890/03-0607 DOI

Tsukaya, H. (2004). Gene flow between Impatiens radicans and I. javensis (Balsaminaceae) in Gunung Pangrango, central Java, Indonesia. American Journal of Botany, 91, 2119–2123. 10.3732/ajb.91.12.2119 PubMed DOI

Ugoletti, P. , Reidy, D. , Jones, M. B. , & Stout, J. C. (2013). Do native bees have the potential to promote interspecific pollination in introduced Impatiens species? Journal of Pollination Ecology, 11, 1–8.