Plant speciation in the Namib Desert: potential origin of a widespread derivative species from a narrow endemic

References

• Abbott RJ. 2017. Plant speciation across environmental gradients and the occurrence and nature of hybrid zones. J Syst Evol. 55(4):238–258. doi:10.1111/jse.12267.
   Google Scholar
• Abbott RJ, Albach D, Ansell S, Arntzen JW, Baird SJE, Bierne N, Boughman J, Brelsford A, Buerkle CA, Buggs CA, et al. 2013. Hybridization and speciation. J Evol Biol. 26(2):229–246. doi:10.1111/j.1420-9101.2012.02599.x.
   Google Scholar
• Alexander JCM. 1979. Mediterranean species of Senecio sections Senecio and Delphinifolius. Notes Roy Bot Gard Edinb. 37(3):387–428.
   Google Scholar
• Anacker BL, Strauss SY. 2014. The geography and ecology of plant speciation: range overlap and niche divergence in sister species. Proc R Soc Ser B. 281(1778):20132980. doi:10.1098/rspb.2013.2980.
   Google Scholar
• Axelrod DI. 1967. Drought diatrophism, and quantum evolution. Evolution. 21(2):201–209. doi:10.1111/j.1558-5646.1967.tb00149.x.
   Google Scholar
• Axelrod DI. 1972. Edaphic aridity as a factor in angiosperm evolution. Am Nat. 106(949):311–320. doi:10.1086/282773.
   Google Scholar
• Baker HG. 1955. Self-compatibility and establishment after ‘long-distance’ dispersal. Evolution. 9(3):347–349. doi:10.1111/j.1558-5646.1955.tb01544.x.
   Google Scholar
• Balinsky BI. 1962. Patterns of animal distribution of the African continent. Ann Cape Prov Mus. 2:299–310.
   Google Scholar
• Banfield LM, van Damme K, Miller AG. 2011. Evolution and biogeography of the flora of the Socotra Archipelago (Yemen). In: Bramwell D Caujapé-Castells J, editors. The biology of island floras. Cambridge (UK): Cambridge University Press; p. 197–225.
   Google Scholar
• Barrett SCH. 2014. Evolution of mating systems: outcrossing versus selfing. In: Losos J, editor. The Princeton guide to evolution. Princeton (NJ): Princeton University Press; p. 356–362.
   Google Scholar
• Beckman NG, Bullock JM, Salguero-Gómez R, Violle C. 2018. High dispersal ability is related to fast life-history stragegies. J Ecol. 106(4):1349–1362. doi:10.1111/1365-2745.12989.
   Google Scholar
• Bellstedt DU, Galley C, Pirie MD, Linder HP. 2012. The migration of the palaeotropical arid flora: Zygophylloideae as an example. Syst Bot. 37(4):951–959. doi:10.1600/036364412X656608.
   Google Scholar
• Berger WH, Lange CB, Wefer G. 2002. Upwelling history of the Benguela-Namib system: a synthesis of Leg 175 results. Proc ODP, Sci Results. 175:1–103.
   Google Scholar
• Billiard S, Lenormand T. 2005. Evolution of migration under kin selection and local adaptation. Evolution. 59(1):13–23. doi:10.1111/j.0014-3820.2005.tb00890.x.
   Google Scholar
• Breiner FT, Guisan A, Bergamini A, Nobis MP. 2015. Overcoming limitations of modelling rare species by using ensembles of small models. Methods Ecol Evol. 6(10):1210–1218. doi:10.1111/2041-210X.12403.
   Google Scholar
• Brown JL, Carnaval AC. 2019. A tale of two niches: methods, concepts and evolution. Front Biogeogr. 11(4):e44158. doi:10.21425/F5FBG44158.
   Google Scholar
• Busch JW. 2005. The evolution of self-compatibility in geographically peripheral populations of Leavenworthia alabamica (Brassicaceae). Am J Bot. 92(9):1503–1512. doi:10.3732/ajb.92.9.1503.
   Google Scholar
• Childers JL, Kirchhof S, Bauer AM. 2021. Lizards of a different stripe: phylogenetics of the Pedioplanis undata species complex (Squamata, Lacertidae), with the description of two new species. Zoosyst Evol. 97(1):249–272. doi:10.3897/zse.97.61351.
   Google Scholar
• Coleman M, Forbes DG, Abbott RJ. 2001. A new subspecies of Senecio mohavensis (Compositae) reveals Old–New world species disjunction. Edinb J Bot. 58(3):389–403. doi:10.1017/S0960428601000713.
   Google Scholar
• Coleman M, Liston A, Kadereit JW, Abbott RJ. 2003. Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae). Am J Bot. 90(10):1446–1454. doi:10.3732/ajb.90.10.1446.
   Google Scholar
• Collins GE, Hogg ID, Baxter JR, Maggs-Kölling G, Cowan DA. 2019. Ancient landscapes of the Namib Desert harbor high levels of genetic variability and deeply divergent lineages for Collembola. Ecol Evol. 9(8):4969–4979. doi:10.1002/ece3.5103.
   Google Scholar
• Collins JA, Schefuß E, Govin A, Mulitza S, Tiedemann R. 2014. Insolation and glacial–interglacial control on southwestern African hydroclimate over the past 140,000 years. Earth Planet Sci Lett. 398:1–10. doi:10.1016/j.epsl.2014.04.034.
   Google Scholar
• Collins JA, Schefuß E, Heslop D, Mulitza S, Prange M, Zabel M, Tjallingii R, Dokken TM, Huang E, Mackensen A, et al. 2011. Interhemispheric symmetry of the tropical African rainbelt over the past 23,000 years. Nat Geosci. 4(1):42–45. doi:10.1038/ngeo1039.
   Google Scholar
• Comes HP, Abbott RJ. 2001. Molecular phylogeography, reticulation, and lineage sorting in Mediterranean Senecio sect. Senecio (Asteraceae). Evolution. 55(10):1943–1962. doi:10.1111/j.0014-3820.2001.tb01312.x.
   Google Scholar
• Coyne JA, Orr HA. 2004. Speciation. Sunderland (MA): Sinauer Associates.
   Google Scholar
• Craven P. 2009. Phytogeographic study of the Kaokoveld centre of endemism [ PhD thesis]. University of Stellenbosch.
   Google Scholar
• Craven P, Craven D. 2000. The flora of the Brandberg, Namibia. In: Kirk-Sprigs ME, editor. Biodiversity of the Brandberg Massif. Vol. 9. Namibia: Cimbebasia Memoir; p. 49–67.
   Google Scholar
• Craven P, Kolberg H. 2021. Plants of Namibia, BRAHMS online. [accessed 2021 December 10]. https://herbaria.plants.ox.ac.uk/bol/namibia.
   Google Scholar
• Craven P, Vorster P. 2006. Patterns of plant diversity and endemism in Namibia. Bothalia. 36(2):175–189. doi:10.4102/abc.v36i2.360.
   Google Scholar
• Crawford DJ. 2010. Progenitor–derivative species pairs and plant speciation. Taxon. 59(5):1413–1423. doi:10.1002/tax.595008.
   Google Scholar
• Cruden RW. 1977. Pollen-ovule ratios: a conservative indicator of breeding systems in flowering plants. Evolution. 31(1):32–46. doi:10.1111/j.1558-5646.1977.tb00979.x.
   Google Scholar
• Dempster AP, Laird NM, Rubin DB. 1977. Maximum Likelihood from incomplete data via the EM algorithm. J R Stat Soc Ser B (Stat Methodol). 39(1):1–38. doi:10.1111/j.2517-6161.1977.tb01600.x.
   Google Scholar
• de Winter B. 1966. Remarks on the distribution of some desert plants in Africa. Palaeoecology of Africa. 1:188–189.
   Google Scholar
• de Winter B. 1971. Floristic relationships between the northern and southern arid areas in Africa. Mitt Bot Staatssamml München. 10:424–437.
   Google Scholar
• Donoghue MJ, Sanderson MJ. 2015. Confluence, synnovation, and depauperons in plant diversification. New Phytol. 207(2):260–274. doi:10.1111/nph.13367.
   Google Scholar
• Drummond AJ, Ho SY, Phillips MJ, Rambaut A. 2006. Relaxed phylogenetics and dating with confidence. PLoS Biol. 4(5):e88. doi:10.1371/journal.pbio.0040088.
   Google Scholar
• Drummond AJ, Suchard MA, Xie D, Rambaut A. 2012. Bayesian phylogenetics with BEAUti and the BEAST 1.7. Mol Biol Evol. 29(8):1969–1973. doi:10.1093/molbev/mss075.
   Google Scholar
• Drury DG, Watson L. 1966. A bizarre pappus form in Senecio. Taxon. 15(8):309–311. doi:10.2307/1216115.
   Google Scholar
• Durvasula A, Fulgione A, Gutaker RM, Alacakaptan SI, Flood PJ, Neto C, Tsuchimatsu T, Burbano HA, Picó FX, Alonso-Blanco C, et al. 2017. African genomes illuminate the early history and transition to selfing in Arabidopsis thaliana. Proc Natl Acad Sci U S A. 114:5213–5218.
   Google Scholar
• Ebersbach J, Tkach N, Röser M, Favre A. 2020. The role of hybridisation in the making of the species-rich arctic-alpine genus Saxifraga (Saxifragaceae). Diversity. 12:440. doi:10.3390/d12110440.
   Google Scholar
• Edler D, Klein J, Antonelli A, Silvestro D. 2021. raxmlGUI 2.0: a graphical interface and toolkit for phylogenetic analyses using RAxML. Methods Ecol Evol. 12(2):373–377. doi:10.1111/2041-210X.13512.
   Google Scholar
• Edmands S. 2002. Does parental divergence predict reproductive compatibility? Trends Ecol Evol. 17(11):520–527. doi:10.1016/S0169-5347(02)02585-5.
   Google Scholar
• e-Flora of South Africa. 2018. South African National Biodiversity Institute. [accessed 2021 December 11]. http://ipt.sanbi.org.za/iptsanbi/resource?r=flora_descriptions&v=1.21.
   Google Scholar
• Ferrer MM, Good-Avila SV. 2006. Macrophylogenetic analyses of the gain and loss of self-incompatibility in the Asteraceae. New Phytol. 173(2):401–414. doi:10.1111/j.1469-8137.2006.01905.x.
   Google Scholar
• Fick SE, Hijmans RJ. 2017. WorldClim 2: new 1-km spatial resolution climate surfaces for global land areas. Int J Climatol. 37(12):4302–4315. doi:10.1002/joc.5086.
   Google Scholar
• Fishman L, Stratton DA. 2004. The genetics of floral divergence and postzygotic barriers between outcrossing and selfing populations of Arenaria uniflora (Caryophyllaceae). Evolution. 58(2):296–307. doi:10.1111/j.0014-3820.2004.tb01646.x.
   Google Scholar
• Foden W, Matlamela PF, Potter L, Kamundi DA. 2011. Senecio flavus (Decne.) Sch.Bip. National Assessment: Red List of South African Plants version 2020.1. [accessed 2021 December 9]. http://redlist.sanbi.org/species.php?species=3152-158.
   Google Scholar
• Fradera-Soler M, Rudall PJ, Prychid CJ, Grace OM. 2021. Evolutionary success in arid habitats: morpho-anatomy of succulent leaves of Crassula species from southern Africa. J Arid Environ. 185:104319. doi:10.1016/j.jaridenv.2020.104319.
   Google Scholar
• Gamisch A. 2019. Oscillayers: a dataset for the study of climatic oscillations over Plio-Pleistocene time-scales at high spatial-temporal resolution. Glob Ecol Biogeogr. 28(11):1552–1560. doi:10.1111/geb.12979.
   Google Scholar
• Gamisch A, Fischer G, Comes HP. 2015. Multiple independent origins of auto-pollination in tropical orchids (Bulbophyllum) in light of the hypothesis of selfing as an evolutionary dead end. BMC Evol Biol. 15(1):192. doi:10.1186/s12862-015-0471-5.
   Google Scholar
• García-Aloy S, Sanmartín I, Kadereit G, Vitales D, Millanes AM, Roquet C, Vargas P, Alarcón M, Aldasoro JJ. 2017. Opposite trends in the genus Monsonia (Geraniaceae): specialization in the African deserts and range expansions throughout eastern Africa. Sci Rep. 7(1):9872. doi:10.1038/s41598-017-09834-6.
   Google Scholar
• Giess W. 1981. Die in der Zentralen Namib von Südwestafrika/Namibia festgestellten Pflanzenarten und ihre Biotope. Dinteria (Windhoek). 15:13–71.
   Google Scholar
• Givnish TJ. 2001. The rise and fall of plant species: a population biologist’s perspective. Am J Bot. 88(10):1928–1934. doi:10.2307/3558369.
   Google Scholar
• Givnish TJ. 2010. Ecology of plant speciation. Taxon. 59(5):1326–1366. doi:10.1002/tax.595003.
   Google Scholar
• Gottlieb LD. 1984. Genetics and morphological evolution in plants. Am Nat. 123(5):681–709. doi:10.1086/284231.
   Google Scholar
• Gottlieb LD. 2004. Rethinking classic examples of recent speciation in plants. New Phytol. 161(1):71–82. doi:10.1046/j.1469-8137.2003.00922.x.
   Google Scholar
• Gould BA, Chen Y, Lowry DB. 2018. Gene regulatory divergence between locally adapted ecotypes in their native habitats. Mol Ecol. 27(21):4174–4188. doi:10.1111/mec.14852.
   Google Scholar
• Grant V. 1981. Plant speciation. 2nd ed. New York (NY): Columbia University Press.
   Google Scholar
• Griffiths AJF, Miller JH, Suzuki DT, Lewontin RC, Gelbart WM. 2000. An introduction to genetic analysis. 7th ed. New York (NY): WH Freeman.
   Google Scholar
• Habibzadeh N, Ghoddousi A, Bleyhl B, Kuemmerle T. 2021. Rear-edge populations are important for understanding climate change risk and adaptation potential of threatened species. Conserv Sci Pract. 3(5):e375. doi:10.1111/csp2.375.
   Google Scholar
• Heinrich S, Zonnenveld KAF, Bickert T, Willems H. 2011. The Benguela upwelling related to the Miocene cooling events and the development of the Antarctic Circumpolar Current: evidence from calcareous dinoflagellate cysts. Paleoceanography. 26(3):A3209. doi:10.1029/2010PA002065.
   Google Scholar
• He Z-W, Li X-N, Yang M, Wang X-F, Zhong C-R, Duke NC, Wu C-I, Shi S-H. 2019. Speciation with gene flow via cycles of isolation and migration: insights from multiple mangrove taxa. Natl Sci Rev. 6(2):275–288. doi:10.1093/nsr/nwy078.
   Google Scholar
• Hijmans RJ, Cameron SE, Parra JL, Jones PG, Jarvis A. 2005. Very high resolution interpolated climate surfaces for global land areas. Int J Climatol. 25(15):1965–1978. doi:10.1002/joc.1276.
   Google Scholar
• Hoetzel S, Dupont LM, Wefer G. 2015. Miocene-Pliocene vegetation change in south-western Africa (ODP Site 1081, offshore Namibia). Palaeogeogr Palaeoclimatol Palaeoecol. 423:102–108. doi:10.1016/j.palaeo.2015.02.002.
   Google Scholar
• Hu Q, Ma Y, Mandáková T, Shi S, Chen C, Sun P, Zhang L, Feng L, Zheng Y, Feng X, et al. 2021. Genome evolution of the psammophyte Pugionium for desert adaptation and further speciation. Proc Natl Acad Sci U S A. 118(42):e2025711118. doi:10.1073/pnas.2025711118.
   Google Scholar
• Igic B, Busch JW. 2013. Is self-fertilization an evolutionary dead end? New Phytol. 198(2):386–397. doi:10.1111/nph.12182.
   Google Scholar
• Irish J. 1994. The biomes of Namibia, as determined by objective categorisation. Res Nat Mus, Bloemfontein. 10:549–592.
   Google Scholar
• Iritani R, Cheptou PO. 2017. Joint evolution of differential seed dispersal and self-fertilization. J Evol Biol. 30(8):1526–1543. doi:10.1111/jeb.13120.
   Google Scholar
• Jeffrey C. 1979. Generic and sectional limits in Senecio (Compositae): II. Evaluation of some recent studies. Kew Bull. 34(1):49–58. doi:10.2307/4117970.
   Google Scholar
• Johnson N. 2008. Hybrid incompatibility and speciation. Nature Education. 1:20.
   Google Scholar
• Jürgens N. 1997. Floristic biodiversity and history of African arid regions. Biodivers Conserv. 6(3):495–514. doi:10.1023/A:1018325026863.
   Google Scholar
• Jürgens N, Oldeland J, Hachfeld B, Erb E, Schultz C. 2013. Ecology and spatial patterns of large-scale vegetation units within the central Namib Desert. J Arid Environ. 93:59–79. doi:10.1016/j.jaridenv.2012.09.009.
   Google Scholar
• Jürgens N, Strohbach B, Schmiedel U, Rügheimer S, Erb E, Wesuls D, Schrenk J, Dreber N, Schmidt M, Mayer C, et al. 2021. Photo guide to plants of Southern Africa. Hamburg, Germany: Research Unit Biodiversity, Evolution & Ecology (BEE) of Plants, Institute for Plant Science and Microbiology. [accessed 2021 December 10]. www.southernafricanplants.net.
   Google Scholar
• Kadereit JW. 1984a. The origin of Senecio vulgaris (Asteraceae). Pl Syst Evol. 145(1–2):135–153. doi:10.1007/BF00984036.
   Google Scholar
• Kadereit JW. 1984b. Some notes on annual species of Senecio L. (Asteraceae) from northern Africa and the Canary Islands. Bot J Syst. 104:509–517.
   Google Scholar
• Kadereit JW, Abbott RJ. 2021. Plant speciation in the Quaternary. Plant Ecol Divers. 14(3–4):105–142. doi:10.1080/17550874.2021.2012849.
   Google Scholar
• Kadereit JW, Comes HP, Curnow JC, Irwin JA, Abbott RJ. 1995. Chloroplast DNA and isozyme analysis of the progenitor-derivative species relationship between Senecio nebrodensis and S. viscosus (Asteraceae). Am J Bot. 82(9):1179–1185. doi:10.1002/j.1537-2197.1995.tb11590.x.
   Google Scholar
• Kadereit JW, Uribe-Convers S, Westberg E, Comes HP. 2006. Reciprocal hybridization at different times between Senecio flavus and Senecio glaucus gave rise to two polyploid species in North Africa and South-West Asia. New Phytol. 169(2):431–441. doi:10.1111/j.1469-8137.2005.01604.x.
   Google Scholar
• Kandziora M, Kadereit JW, Gehrke B. 2017. Dual colonization of the Palaearctic from different regions in the Afrotropics by Senecio. J Biogeogr. 44(1):147–157. doi:10.1111/jbi.12837.
   Google Scholar
• Kandziroa M. 2015. Evolution und historische Biogeographie von Senecio L. mit Fokus auf die Alte Welt [ PhD thesis]. Germany: University of Mainz.
   Google Scholar
• Kassambara A, Mundt F. 2017. R package factoextra. Extract and visualize the results of multivariate data analyses. Vienna, Austria: R Foundation for Statistical Computing. [accessed 2021 December 10]. https://cran.r-project.org/web/packages/factoextra/index.html.
   Google Scholar
• Kay KM, Whittall JB, Hodges SA. 2006. A survey of nuclear ribosomal internal transcribed spacer substitution rates across angiosperms: an approximate molecular clock with life history effects. BMC Evol Biol. 6(1):36. doi:10.1186/1471-2148-6-36.
   Google Scholar
• Kim M, Cui M-L, Cubas P, Gillies A, Lee K, Chapman MA, Abbott RJ, Coen E. 2008. Regulatory genes control a key morphological and ecological trait transferred between species. Science. 322(5904):1116–1119. doi:10.1126/science.1164371.
   Google Scholar
• Kirkpatrick M, Barton NH. 1997. Evolution of a species’ range. Am Nat. 150(1):1–23. doi:10.1086/286054.
   Google Scholar
• Kissling WD, Blach-Overgaard A, Zwaan RE, Wagner P. 2016. Historical colonization and dispersal limitation supplement climate and topography in shaping species richness of African lizards (Reptilia: Agaminae). Sci Rep. 6(1):34014. doi:10.1038/srep34014.
   Google Scholar
• Klaassen ES, Kwembeya EG. 2013. A checklist of Namibian indigenous and naturalised plants. Windhoek (Namibia): Occasional Contributions No. 5 National Botanical Research Institute.
   Google Scholar
• Kulmuni J, Butlin RK, Lucek K, Savolainen V, Westram AM. 2020. Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers. Phil Trans R Soc B. 375(1806):20190528. doi:10.1098/rstb.2019.0528.
   Google Scholar
• Lamb T, Bond JE. 2013. A multilocus perspective on phylogenetic relationships in the Namib darkling beetle genus Onymacris (Tenebrionidae). Mol Phylogenet Evol. 66(3):757–765. doi:10.1016/j.ympev.2012.10.026.
   Google Scholar
• Lankinen A. 2009. Upper petal lip colour polymorphism in Collinsia heterophylla (Plantaginaceae): genetic basis within a population and its use as a genetic marker. J Genet. 88(2):205–215. doi:10.1007/s12041-009-0029-7.
   Google Scholar
• Lawrence ME. 1981. Relationships of south-east Australian species of Senecio (Compositae) deduced from studies of morphology, reproductive biology and cytogenetics [ PhD thesis]. University of Adelaide.
   Google Scholar
• Levin DA. 2000. The origin, expansion, and demise of plant species. Oxford (UK): Oxford University Press.
   Google Scholar
• Levin DA. 2004. The ecological transition in speciation. New Phytol. 161(1):91–96. doi:10.1046/j.1469-8137.2003.00921.x.
   Google Scholar
• Linder HP. 2014. The evolution of African plant diversity. Front Ecol Evol. 2:38. doi:10.3389/fevo.2014.00038.
   Google Scholar
• Liston A, Rieseberg LH, Elias TS. 1989. Genetic similarity is high between intercontinental disjunct species of Senecio (Asteraceae). Am J Bot. 76(3):383–388. doi:10.1002/j.1537-2197.1989.tb11325.x.
   Google Scholar
• López P, Tremetsberger K, Kohl G, Stuessy T. 2012. Progenitor–derivative speciation in Pozoa (Apiaceae, Azorelloideae) of the southern Andes. Ann Bot. 109(2):351–363. doi:10.1093/aob/mcr291.
   Google Scholar
• Lowe AJ, Abbott RJ. 2000. Routes of origin of two recently evolved hybrid taxa: Senecio vulgaris var. hibernicus and York radiate groundsel (Asteraceae). Am J Bot. 87(8):1159–1167. doi:10.2307/2656652.
   Google Scholar
• Luebert F, Jacobs P, Hilger HH, Muller LAH. 2014. Evidence for nonallopatric speciation among closely related sympatric Heliotropium species in the Atacama Desert. Ecol Evol. 4(3):266–275. doi:10.1002/ece3.929.
   Google Scholar
• Maggs GL, Craven P, Kolberg HH. 1998. Plant species richness, endemism, and genetic resources in Namibia. Biodivers Conserv. 7(4):435–446. doi:10.1023/A:1008819426848.
   Google Scholar
• Mallet J. 2005. Hybridization as an invasion of the genome. Trends Ecol Evol. 20(5):229–237. doi:10.1016/j.tree.2005.02.010.
   Google Scholar
• Marlow JR, Lange CB, Wefer G, Rosell‐Melé A. 2000. Upwelling intensification as part of the Pliocene‐Pleistocene climate transition. Science. 290(5500):2288–2291. doi:10.1126/science.290.5500.2288.
   Google Scholar
• Ma T, Wang K, Hu Q, Xia Z, Wan D, Wang Q, Feng J, Jiang D, Ahani H, Abbott RJ, et al. 2018. Ancient polymorphisms and divergence hitchhiking contribute to genomic islands of divergence within a poplar species complex. Proc Natl Acad Sci U S A. 115(2):E236–243. doi:10.1073/pnas.1713288114.
   Google Scholar
• Mayr E. 1963. Animal species and evolution. Cambridge (MA): Harvard University Press.
   Google Scholar
• Merxmüller H. 1967. Senecio L. In: Merxmüller H, editor. Prodromus einer Flora von Südwestafrika, Asteraceae. Vol. 139. Stuttgart, Germany: Verlag J Cramer, Lehre; p. 162–173.
   Google Scholar
• Milton JJ. 2009. Phylogenetic analyses and taxonomic studies of Senecioninae: Southern African Senecio sect. Senecio [ PhD thesis]. University of St Andrews.
   Google Scholar
• Mutanen M, Kivelä SM, Vos RA, Doorenweerd C, Ratnasingham S, Hausmann A, Huemer P, Dinca V, van Nieukerken EJ, Lopez-Vaamonde C, et al. 2016. Para- and polyphyly in DNA barcode trees: strong operational bias in European Lepidoptera. Syst Biol. 65(6):1024–1040. doi:10.1093/sysbio/syw044.
   Google Scholar
• Neumann F, Scott L. 2018. E.M. van Zinderen Bakker (1907–2002) and the study of African Quaternary palaeoenvironments. Quat Int. 495:153–168. doi:10.1016/j.quaint.2018.04.017.
   Google Scholar
• Nylinder S, Razafimandimbison SG, Anderberg AA. 2016. From the Namib around the world: biogeography of the Inuleae-Plucheinae (Asteraceae). J Bioegogr. 43(9):1705–1716. doi:10.1111/jbi.12764.
   Google Scholar
• Ornduff R. 1969. Reproductive biology in relation to systematics. Taxon. 18(2):121–133. doi:10.2307/1218671.
   Google Scholar
• Orr HA, Turelli M. 2001. The evolution of postzygotic isolation: accumulating Dobzhansky-Muller incompatibilities. Evolution. 55(6):1085–1094. doi:10.1111/j.0014-3820.2001.tb00628.x.
   Google Scholar
• Otero A, Vargas P, Valcárcel V, Fernández-Mazuecos M, Jiménez-Mejías P, Hipp AL. 2022. A snapshot of progenitor-derivative speciation in action in Iberodes (Boraginaceae). Mol Ecol. 31(11):3192–3209. doi:10.1111/mec.16459.
   Google Scholar
• Panero JL, Francisco-Ortega J, Jansen RK, Santos-Guerra A. 1999. Molecular evidence for multiple origins of woodiness and a New World biogeographic connection of the Macaronesian island endemic Pericallis (Asteraceae; Senecioneae). Proc Natl Acad Sci U S A. 96(24):13886–13891. doi:10.1073/pnas.96.24.13886.
   Google Scholar
• Paun O, Forest F, Fay MF, Chase MW. 2009. Hybrid speciation in angiosperms: parental divergence drives ploidy. New Phytol. 182(2):507–518. doi:10.1111/j.1469-8137.2009.02767.x.
   Google Scholar
• Pelser PB, Kennedy AH, Tepe EJ, Shidler JB, Nordenstam B, Kadereit JW, Watson LE. 2010. Patterns and causes of incongruence between plastid and nuclear Senecioneae (Asteraceae) phylogenies. Am J Bot. 97(5):856–873. doi:10.3732/ajb.0900287.
   Google Scholar
• Pelser PB, Nordenstam B, Kadereit JW, Watson LE. 2007. An ITS phylogeny of tribe Senecioneae (Asteraceae) and a new delimitation of Senecio L. Taxon. 56(4):1077–1104. doi:10.2307/25065905.
   Google Scholar
• Perkins JS. 2020. Take me to the river along the African drought corridor: adapting to climate change. Botsw J Agric Appl Sci. 14(1):60–71. doi:10.37106/bojaas.2020.77.
   Google Scholar
• Pflugbeil G, Affenzeller M, Tribsch A, Comes HP. 2021. Primary hybrid zone formation in Tephroseris helenitis (Asteraceae), following postglacial range expansion along the central Northern Alps. Mol Ecol. 30(7):1704–1720. doi:10.1111/mec.15832.
   Google Scholar
• Phillips SJ, Anderson RP, Dudík M, Schapire RE, Blair ME. 2017. Opening the black box: an open-source release of Maxent. Ecography. 40(7):887–893. doi:10.1111/ecog.03049.
   Google Scholar
• Pokorny L, Riina R, Mairal M, Meseguer AS, Culshaw V, Cendoya J, Serrao Pérez LM, Carbajal Vilaverde R, Ortiz Núnes S, Heuertz M, et al. 2015. Living on the edge: timing of Rand Flora disjunctions congruent with ongoing aridification in Africa. Front Genet. 6:154. doi:10.3389/fgene.2015.00154.
   Google Scholar
• QGIS Development Team. 2019. QGIS Geographic Information System. Open Source Geospatial Foundation Project. [accessed 2021 December 10]. http://qgis.osgeo.org.
   Google Scholar
• Randle AM, Slyder JB, Kalisz S. 2009. Can differences in autonomous selfing ability explain differences in range size among sister-taxa pairs of Collinsia (Plantaginaceae)? An extension of Baker’s Law. New Phytol. 183(3):618–629. doi:10.1111/j.1469-8137.2009.02946.x.
   Google Scholar
• R Development Core Team. 2017. R: a language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing. [accessed 2021 December 10]. https://www.r-project.org.
   Google Scholar
• Revell LJ. 2012. Phytools, an R package for phylogenetic comparative biology (and other things). Methods Ecol Evol. 3(2):217–223. doi:10.1111/j.2041-210X.2011.00169.x.
   Google Scholar
• Richards TJ, Ortiz-Barrientos D. 2016. Immigrant inviability produces a strong barrier to gene flow between parapatric ecotypes of Senecio lautus. Evolution. 70(6):1239–1248. doi:10.1111/evo.12936.
   Google Scholar
• Rieseberg LH. 2000. Crossing relationships among ancient and experimental sunflower hybrid lineages. Evolution. 54(3):859–865. doi:10.1111/j.0014-3820.2000.tb00086.x.
   Google Scholar
• Rommerskirchen F, Condon T, Mollenhauer G, Dupont L, Schefuß E. 2011. Miocene to Pliocene development of surface and subsurface temperatures in the Benguela Current system. Paleoceanography. 26(3):A3216. doi:10.1029/2010PA002074.
   Google Scholar
• Rothfels CJ, Johnson AK, Hoevenkamp PH, Swofford DL, Roskam HC, Fraser-Jenkins CR, Windham MD, Pryer KM. 2015. Natural hybridization between genera that diverged from each other approximately 60 million years ago. Am Nat. 185(3):433–442. doi:10.1086/679662.
   Google Scholar
• Satokangas I, Martin SH, Helanterä H, Saramäki J, Kulmuni J. 2020. Multi-locus interactions and the build-up of reproductive isolation. Phil Trans R Soc B. 375(1806):20190543. doi:10.1098/rstb.2019.0543.
   Google Scholar
• Schluter D. 2001. Ecology and the origin of species. Trends Ecol Evol. 16(7):372–380. doi:10.1016/S0169-5347(01)02198-X.
   Google Scholar
• Schoener TW. 1968. The Anolis lizards of Bimini: resource partitioning in a complex fauna. Ecology. 49(4):704–726.
   Google Scholar
• Schrire BD, Lavin M, Barker NP, Forest F. 2009. Phylogeny of the tribe Indigofereae (Leguminosae – Papilionoideae): geographically structured more in succulent-rich and temperate settings than in grass-rich environments. Am J Bot. 96(4):816–852. doi:10.3732/ajb.0800185.
   Google Scholar
• Sexton JP, McIntyre PJ, Angert AL, Rice K. 2009. Evolution and ecology of species range limits. Ann Rev Ecol Evol Syst. 40(1):415–436. doi:10.1146/annurev.ecolsys.110308.120317.
   Google Scholar
• Sicard A, Lenhard M. 2011. The selfing syndrome: a model for studying the genetic and evolutionary basis of morphological adaptation in plants. Ann Bot. 107(9):1433–1443. doi:10.1093/aob/mcr023.
   Google Scholar
• Singhal S, Roddy AB, DiVittorio C, Sanchez-Amaya A, Henriquez CL, Brodersen CR, Fehlberg S, Zapata F. 2021. Diversification, disparification and hybridization in the desert shrubs Encelia. New Phytol. 230(3):1228–1241. doi:10.1111/nph.17212.
   Google Scholar
• Slopa C, Dias MC, Castro M, Loureiro J, Castro S. 2020. Is selfing a reproductive assurance promoting polyploid establishment? Reduced fitness, leaky self-incompatibility and lower inbreeding depression in neotetraploids. Am J Bot. 107(3):526–538. doi:10.1002/ajb2.1441.
   Google Scholar
• Sobel JM, Chen GF, Watt LR, Schemske DW. 2010. The biology of speciation. Evolution. 64(2):295–315. doi:10.1111/j.1558-5646.2009.00877.x.
   Google Scholar
• Stadler T, Rabosky DL, Ricklefs R, Bokma F. 2014. On age and species richness of higher taxa. Am Nat. 184(4):447–455. doi:10.1086/677676.
   Google Scholar
• Stamatakis A. 2014. RAxML version 8: a tool for phylogenetic analysis and post-analysis of large phylogenies. Bioinformatics. 30(9):1312–1313. doi:10.1093/bioinformatics/btu033.
   Google Scholar
• Stebbins GL. 1952. Aridity as a stimulus to plant evolution. Am Nat. 86(826):33–44. doi:10.1086/281699.
   Google Scholar
• Stebbins GL. 1972. Ecological distribution of centers of major adaptive radiation in angiosperms. In: Valentine D, editor. Taxonomy, phytogeography, and evolution. New York (NY): Academic Press; p. 7–34.
   Google Scholar
• Stebbins GL. 1974. Flowering plants: evolution above the species level. Cambridge (MA): Harvard University Press.
   Google Scholar
• Takebayashi N, Morrell PL. 2001. Is self-fertilization an evolutionary dead end? Revisiting an old hypothesis with genetic theories and a macroevolutionary approach. Am J Bot. 88(7):1143–1150. doi:10.2307/3558325.
   Google Scholar
• Thiv M, van der Niet T, Rutschmann F, Thulin M, Brune T, Linder HP. 2011. Old–New World and trans-African disjunctions of Thamnosma (Rutaceae): intercontinental long-distance dispersal and local differentiation in the succulent biome. Am J Bot. 98(1):76–87. doi:10.3732/ajb.1000339.
   Google Scholar
• Tigano A, Friesen V. 2016. Genomics of local adaptation with gene flow. Mol Ecol. 25(10):2144–2164. doi:10.1111/mec.13606.
   Google Scholar
• Tripp EA, Tsai YHE, Zhuang Y, Dexter KG. 2017. RAD seq dataset with 90% missing data fully resolves recent radiation of Petalidium (Acanthaceae) in the ultra-arid deserts of Namibia. Ecol Evol. 7(19):7920–7936. doi:10.1002/ece3.3274.
   Google Scholar
• van Zinderen Bakker EM. 1975. The origin and palaeoenvironment of the Namib Desert biome. J Biogeogr. 2(2):65–73. doi:10.2307/3038074.
   Google Scholar
• Verdcourt B. 1969. The arid corridor between the northeast and southwest areas of Africa. Palaeoecol Afr. 4:140–144.
   Google Scholar
• Vu VQ. 2011. Ggbiplot: a ggplot2 based biplot. R package Version 0.55. [accessed 2021 December 11]. https://github.com/vqv/ggbiplot.
   Google Scholar
• Walter GM, Abbott RJ, Brennan AC, Bridle JR, Chapman M, Clark J, Filatov D, Nevado B, Ortiz-Barrientos D, Hiscock S. 2020. Senecio as a model system for integrating studies of genotype, phenotype and fitness. New Phytol. 226(2):326–344. doi:10.1111/nph.16434.
   Google Scholar
• Wang Q, Abbott RJ, Yu Q-S, Lin K, Liu J-Q. 2013. Pleistocene climate change and the origin of two desert plant species, Pugionium cornutum and Pugionium dolabratum (Brassicaceae), in northwest China. New Phytol. 199(1):277–287. doi:10.1111/nph.12241.
   Google Scholar
• Wang RJ, Ané C, Payseur BA. 2013. The evolution of hybrid incompatibilities along a phylogeny. Evolution. 67:2905–2922. doi:10.1111/evo.12173.
   Google Scholar
• Wang RJ, White M, Payseur BA. 2015. The pace of hybrid incompatibility evolution in house mice. Genetics. 201(1):229–242. doi:10.1534/genetics.115.179499.
   Google Scholar
• Wan T, Liu Z, Leitch IJ, Xin H, Maggs-Kölling G, Gong Y, Li Z, Marais E, Liao Y, Dai C, et al. 2021. The Welwitschia genome reveals a unique biology underpinning extreme longevity in deserts. Nature Comm. 12(1):4247. doi:10.1038/s41467-021-24528-4.
   Google Scholar
• Warren DL, Glor RE, Turelli M. 2010. ENMTools: a toolbox for comparative studies of environmental niche models. Ecography. 33(3):607–611. doi:10.1111/j.1600-0587.2009.06142.x.
   Google Scholar
• White F. 1983. Vegetation map of Africa. UNESCO. Nat Resour Res. 20:1–356. https://paperpile.com/n/natural-resources-research-abbreviation/
   Google Scholar
• Wickham H, François R, Henry L, Müller K. 2021. Dplyr: a grammar of data manipulation. R package version 1.0.6. [accessed 2021 December 11]. https://cran.r-project.org/web/packages/dplyr/index.html.
   Google Scholar
• Wielstra B. 2019. Historical hybrid zone movement: more pervasive than appreciated. J Biogeogr. 46(7):1300–1305. doi:10.1111/jbi.13600.
   Google Scholar
• Wilkinson MC, Roda F, Walter GM, James ME, Nipper R, Walsh J, Allen SL, North HL, Beveridge CB, Ortiz-Barrientos D. 2021. Adaptive divergence in shoot gravitropism creates hybrid sterility in an Australian wildflower. Proc Natl Acad Sci U S A. 118(47):e2004901118. doi:10.1073/pnas.2004901118.
   Google Scholar
• Winterbottom JM. 1967. Climatological implications of avifaunal resemblances between South Western Africa and Somaliland. Palaeoecol Afr. 2:77–79.
   Google Scholar
• Young D, Benaglia T, Chauveau D, Hunter D, Elmore R, Hettmansperger T, Thomas H, Xuan F 2020. Mixtools: tools for analyzing finite mixture models. R package version 1.2.0. [accessed 2021 December 11]. https://cran.r-project.org/web/packages/mixtools/index.html.
   Google Scholar