Cryptantha echinosepala, Macbride, 1918

Simpson, Michael G. & Rebman, Jon P., 2021, Research in Boraginaceae: A new variety of Cryptantha maritima, Cryptantha pondii resurrected, and Johnstonella echinosepala transferred back to Cryptantha, Phytotaxa 509 (2), pp. 185-210 : 202-203

Variation in Cryptantha echinosepala

In our study of Cryptantha echinosepala , we noted two disjunct regions of distribution, one in the islands adjacent to Magdalena Bay on the Pacific Ocean side of the Baja California peninsula, and one in the Sierra de La Giganta, Gulf of California coastal regions, and northeastern Cape region of the peninsula ( Fig. 10 ). These two regions are separated by the extensive Magdalena Plains ( Fig. 10B ). A comparison of specimens from these two regions revealed some morphological differences. Plants from Magdalena Island, the type locality of C. echinosepala , tend to have cauline leaves lacking strong bristle-like trichomes on the margins, shorter inflorescences with the flowers more clustered, and possibly smaller calyces. Plants from the Sierra de La Giganta near the Gulf side tend to have cauline leaves with prominent marginal setose trichomes, longer inflorescence cymules with the flowers more separated, and larger calyces. We do not think that these differences are sufficient enough to give different names to the populations of these two centers of distribution at present, pending more detailed studies. If future morphometric and/or molecular analyses show strong differences between populations of these two regions, there may be justification for separating them taxonomically.

THE MARITIMAE CLADE

The Maritimae clade (after Johnston’s (1925: 44) series Maritimae) refers to a monophyletic group named in Simpson et al. (2017a) and Mabry & Simpson (2018). This clade was well-supported from molecular data and separate from the genus Cryptantha , although its placement within the subtribe Amsinckiinae varied depending on the type of sequence data analyzed. Hasenstab-Lehman & Simpson 2012 first discovered that the genus Cryptantha s.l. was polyphyletic and best separated into six groups: the genera Eremocarya , Greeneocharis , Johnstonella , and Oreocarya , plus two other clades: a large one (termed Cryptantha s.s. 1) containing the bulk of Cryptantha species and a smaller one (termed Cryptantha s.s. 2), containing the North and South American Cryptantha maritima (both C. maritima var. m. of North America and a South American specimen of C. maritima var. pilosa sampled) plus two South American species: C. granulosa ( Ruiz & Pavon 1799: 5) Johnston (1923: 54) and C. chaetocalyx (Philippi 1860: 39) Johnston (1927: 43) . Simpson et al. 2017a sampled considerably more taxa in the subtribe and obtained very similar results. This later study also retrieved the same four segregate genera and a diphyletic Cryptantha s.s. The bulk of the species occurred in a “core” Cryptantha s.s. clade, this largely equivalent to Cryptantha s.s. 1 and containing the type of the genus, C. glomerata Lehmann ex Don (1837: 373) . A few Cryptantha species , however, occurred in a smaller clade, termed the Maritimae clade as mentioned earlier, containing taxa similar to Cryptantha s.s. 2. The Maritimae clade of Simpson et al. (2017a) consisted of the North American Cryptantha clokeyi Johnston (1939: 387) , C. martirensis M.G.Simpson & Rebman (2013: 35) , and C. muricata ( Hooker & Arnott 1840: 369) Nelson & Macbride (1916: 42) var. muricata , plus a sister subclade of Cryptantha [ Johnstonella ] echinosepala , C. maritima var. m., and the South American C. subamplexicaulis (Philippi 1860: 39) Reiche (1907: 826) . ( Cryptantha granulosa and C. chaetocalyx were not sequenced in that study.) The Maritimae clade was well supported, but its relationship to other clades and genera of the subtribe was equivocal.

Of the five species placed by Johnston (1925: 44) in his series Maritimae, only two— Cryptantha echinosepala and C. maritima — occurred in the Maritimae clade of Simpson et al. (2017a). The other three species— Cryptantha dumetorum , C. micromeres , and C. recurvata —all group firmly within Cryptantha s.s. in their analyses. The similarities of Cryptantha pondii to C. maritima lead us to surmise that the former might also be best placed with the other taxa of the Maritimae clade, including C. echinosepala . Future sequencing of C. pondii will be needed to confirm this, although it may be difficult to obtain DNA material given its extreme rarity. However, we reiterate that this Maritimae clade forms a well-supported monophyletic group in the three molecular phylogenetic studies cited, a group separate from the genus Cryptantha s.s. The members of that clade may, in fact, best be placed in a new genus in the future, one separate from Cryptantha .

Figures

FIGURE 10. Cryptantha echinosepala [Johnstonella e.] distribution maps, coordinates from Baja Flora (2021).A. Topography map. Map from ©Google 2020, INEGI Data. B. Map from Baja Flora (2021) showing vegetation zones (after Rebman et al. 2016) where the species occurs.