Obsolete subgenus within the former genus "Dryandra"
Dryandra" subg. "Diplophragma is an obsolete subgenus within the former genus "Dryandra" (now "Banksia" ser. "Dryandra"). It was first published by Robert Brown in 1830, but was discarded by George Bentham in 1870. It was reinstated with a new circumscription by Alex George in 1996, but was ultimately discarded again in 2007 when Austin Mast and Kevin Thiele sank "Dryandra" into "Banksia".
According to Brown.
"Diplographma" was first published by Brown in his 1830 "Supplementum primum prodromi florae Novae Hollandiae". Brown's arrangement divided "Dryandra" into three groups according to what Brown perceived to be variations in the number of seed separators. He allowed for these groups to be treated at subgenus or section rank, but they are now treated as having been published as sections.
"D." sect. "Diplophragma" was defined as containing a single species, "D. bipinnatifida" (now "Banksia bipinnatifida"), which Brown thought contained two seed separators. The epithet "Diplophragma" is from the Greek "diplo" ("two") and "phragma" ("barrier"). It is not clear how Brown came to believe that this species has two seed separators, as it actually has none.
The placement and circumscription of "D." sect. "Diplophragma" in Brown's 1830 arrangement may be summarised as follows:
Dryandra (now "B." ser. "Dryandra")
"Dryandra verae" (18 species)
D." sect. "Diplophragma
"D. bipinnatifida" (now "B. bipinnatifida")
"D." sect. "Aphragma" (4 species)
"Hemiclidia" (1 species)
According to Meissner.
In 1856, Carl Meissner published a revision of "Dryandra". He retained all three of Brown's sections, but added bipinnatifid leaves (that is, leaves that are divided into lobes that are themselves divided) to the defining characters of "D." sect. "Diplophragma", and included in it the species "D. preissii" (now "Banksia acuminata"), which had been published in 1845. The placement and circumscription of "D." sect. "Diplophragma" in Meissner's arrangement thus looks like this:
Dryandra (now "Banksia" ser. "Dryandra")
"D." sect. "Eudryandra" (8 series, 47 species, 7 varieties)
D." sect. "Diplophragma
"D. bipinnatifida" (now "B. bipinnatifida")
"D. Preissii" (now "B. acuminata")
"D." sect. "Aphragma" (4 species, 4 varieties)
"Hemiclidia" (1 species)
According to Bentham.
Along with many of Meissner's infrageneric taxa, which were overly reliant on leaf characters, Bentham discarded "D." sect. "Diplophragma" in his 1870 arrangement. Despite having seen only a few seeds, he correctly observed that the characteristics of the fruit upon which Brown based the section were not constant: ;templatestyles src="Template:Blockquote/styles.css" / ;"[I]n the few seeds that I have been able to examine, the separation of the integument from the nucleus when not consolidated with the corresponding integument of the other seed has not appeared to me to be at all constant. The whole question requires further investigation on the part of those who may have a sufficient supply of good fruits of the several species." Bentham also recognised that the two species placed in "D." sect. "Diplophragma" by Meissner are not closely related; he placed "D. bipinnatifida" in "D." sect. "Aphragma", and "D. preissii" in "D." sect. "Eudryandra" ser. "Niveae".
According to George.
When Alex George published his revision of "Dryandra" in 1996, he recognised that "D. bipinatifida" possessed a number of very distinctive characters, especially in its fruiting structure. These include unusually large follicles and seeds; seeds that are set within the seed wings rather than along the base or one side; and unusual double wings that are attached to each side of the seed. In addition, the species has extremely long involucral bracts, and floral bracts that enlarge more than any other species. Recognising the need for this species to be placed in its own subgenus, George resurrected "Diplophragma", promoting it to subgenus rank as "D." subg. "Diplophragma".
The placement and circumscription of "D." subg. "Diplophragma" in George's arrangement, as amended in 1999 and 2005, may be summarised as follows:
Dryandra (now "Banksia" ser. "Dryandra")
"D." ser. "Dryandra" (24 series, 91 species, 39 subspecies, 23 varieties)
"D." ser. "Hemiclidia" (2 species)
D." subg. "Diplophragma
"D. bipinnatifida" (now "Banksia bipinnatifida")
Recent developments.
Since 1998, Austin Mast has been publishing results of ongoing cladistic analyses of DNA sequence data for the subtribe Banksiinae. His analyses have provided compelling evidence of the paraphyly of "Banksia" with respect to "Dryandra"; that is, it seems that "Dryandra" arose from within the ranks of "Banksia". Early in 2007, Mast and Kevin Thiele initiated a rearrangement of "Banksia" by sinking "Dryandra" into it as "B." ser. "Dryandra". This transfer necessitated the setting aside of George's infrageneric arrangement of "Dryandra"; thus "D." subg. "Diplophragma" is no longer current. Mast and Thiele have foreshadowed publishing a full arrangement once DNA sampling of "Dryandra" is complete.
References.
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