Chromosomes and evolution in New Zealand endemic angiosperms and gymnosperms

In situ hybridization with genomic and rDNA probes reveals complex origins for polyploid New Zealand species ofPlantago(Plantaginaceae)

“…The New Zealand angiosperm flora is now thought to be of relatively recent origin (< 26 Ma and for many genera < 1-5 Ma) and characterized by species radiations in which there is low genetic divergence, as measured by the variation in DNA sequences of both nuclear and plastid genomes, but an apparently high incidence of autochthonous polyploidy (Murray & de Lange 2011). There are several examples of autochthonous polyploids thought to be derived from one or a few relatively recent colonization events (cited in Murray & de Lange 2011).…”

“…There are several examples of autochthonous polyploids thought to be derived from one or a few relatively recent colonization events (cited in Murray & de Lange 2011). The great majority (201 of 210 for which data is available in the form of a published photograph) of the New Zealand polyploids are bivalent-forming at meiotic metaphase I and thus appear to be alloploids (Murray & de Lange 2011).…”

“…There are several examples of autochthonous polyploids thought to be derived from one or a few relatively recent colonization events (cited in Murray & de Lange 2011). The great majority (201 of 210 for which data is available in the form of a published photograph) of the New Zealand polyploids are bivalent-forming at meiotic metaphase I and thus appear to be alloploids (Murray & de Lange 2011). This scenario with allopolyploidy associated with low genetic divergence presents a paradox as Complex genomes in Plantago polyploids 325 allopolyploid formation is more likely to follow hybridization between parental species that show a high level of genetic differentiation with hybridization between more genetically similar parents more likely to result in homoploid hybrid species (Paun et al 2009).…”

“…An often stated case is the increase in polyploidy in temperate compared with tropical floras or in regions that have been recently glaciated compared with non-glaciated areas (Stebbins 1950;Brochmann et al 2004). Polyploidy is also particularly prevalent in the angiosperm floras of many oceanic islands, for example, c. 80% of the flowering plants of both the Hawaiian Islands (Carr 1998) and New Zealand (Murray & de Lange 2011) are polyploid. In New Zealand, the majority of the polyploids appear to be alloploids, based on the formation of bivalents only at meiotic metaphase I (Murray & de Lange 2011).…”

“…Polyploidy is also particularly prevalent in the angiosperm floras of many oceanic islands, for example, c. 80% of the flowering plants of both the Hawaiian Islands (Carr 1998) and New Zealand (Murray & de Lange 2011) are polyploid. In New Zealand, the majority of the polyploids appear to be alloploids, based on the formation of bivalents only at meiotic metaphase I (Murray & de Lange 2011). However, phylogenetic analyses of most New Zealand angiosperm genera show low levels of DNA sequence divergence between species (Winkworth et al 1999) and, at least in some cases, for example Veronica (as Hebe), it has been suggested that species radiation has occurred after a single introduction (Wagstaff & Garnock-Jones 1998;Wagstaff et al 2002).…”