Talk:Taxodium

WS can not take side when there are taxonomic opinions that are supported by a number of authorities. The extant genus is treated as monospecific by many authors (e.g. Adams et al. 2012, Govaerts et al. 2020). However, Ikezaki et al. (2016) seemed to indicate that differentiation into one or two species is a matter of taxonomic opinion, but did not deal with T. mucronatum/T. d. var. mexicanum. Taxodium mucronatum is usually treated as a separate species in Mexico and Central America, which is it natural range (Farjon in Flora Mesoamerica, 2020). Natural and artificial hybridisation resulting in viable and fertile offspring between all the putative species is common and exploited in horticulture (Creech et at., 2011 & Duan et al., 2020), which may support a monotypic genus. Andyboorman (talk) 13:31, 8 October 2020 (UTC)

@Andyboorman: viable fertile offspring doesn't support (or deny) a monospecific genus; if it was taken to indicate conspecificity, you'd also have to accept e.g. "Pinus strobus var./subsp. wallichiana", etc., as they (and numerous other related white pine species) also hybridise freely with fertile progeny (and many more similar nightmares in Abies, Larix, and Picea, too). What is most interesting is the new evidence in the Duan et al. 2020 paper, that the relationship is ((mucronatum-distichum) ascendens), when everyone previously has assumed (mucronatum (distichum-ascendens)), as in e.g. GRIN's and Farjon's taxonomy. This, with the distinct distichum populations mentioned in the Ikezaki et al. 2016 paper, raises to me an interesting possibility: could distichum be a natural postglacial range expansion hybrid between mucronatum (from a "Tex-mex" refugium) and ascendens (from a Florida refugium)? Something that might be worth further investigation; it has notably much the largest cones of the three taxa, hinting at possible heterosis. [PS I've corrected a typo in your paragraph above, hope that's OK!]. - MPF (talk) 23:23, 8 October 2020 (UTC)