Large emergent forms of S. minor were even thought by B. J. Simpson (1988) to be hybrids of that species with S. palmetto, but his claim is undocumented and unsubstantiated.Simpson's brief comment in his A Field Guide to Texas Trees would appear to be directed solely at S. minor forms in E. Texas and Louisiana, not the Brazoria population [p. 309]:
There are a few tree forms of S. minor, but most authors state that these tall plants are the result of a high water table, frequent flooding, and shade. Here the tall form of S. minor is considered an introgressed hybrid with S. palmetto and is not included [RTH: as a tree].Simpson's willingness to entertain the possibility of hybridization with S. palmetto is quite curious, given that that species is not shown by Zona as native west of the Florida panhandle.
In the article for S. mexicana Zona again mentions hybridizaion with S. minor, and specifically with relevance to the Brazoria palms:
L. Lockett (1991) suggested that hybridization between Sabal mexicana and S. minor is possibly evidenced by a small population of caulescent palms in Brazoria County, Texas (L. Lockett 1991). Further research is needed to test this hypothesis.