MYRICACEAE

Weakley, Alan S., Kees, John C., Sorrie, Bruce A., Ward, Scott G., Poindexter, Derick B., Brock, Mason, Estes, L. Dwayne, Bridges, Edwin L., Orzell, Steve L., Levin, Geoffrey A., McClelland, R. Kevan Schoonover, Schmidt, Ryan J. & Namestnik, Scott A., 2023, Studies In The Vascular Flora Of The Southeastern United States. Ix, Journal of the Botanical Research Institute of Texas 17 (1), pp. 191-257 : 227-229

MYRICACEAE

MORELLA : Taxonomic recognition and names in Southeastern United States Morella Primary author:Alan S.Weakley & Derick B. Poindexter

The taxonomy of bayberries of the southeastern United States (and beyond) has been unsettled and controversial at all ranks below family. In the last several decades, a consensus as to genera has developed, with four genera recognized in the family: Comptonia L’Hér. 1789 , Myrica L. 1753, Morella Lour. 1790 , and the New Caledonian endemic Canacomyrica Guillaumin 1940 . Within Morella , and in eastern North America, though, there has been controversy about the number of taxa to be recognized and their rank, with some taxa not having correct and available names in Morella at the appropriate rank (because of the prevailing use until 1995 of Myrica or Cerothamnus for these taxa).

Based on our field experience across the region, we support the recognition of five taxa, each at species rank: Morella inodora (Bartram) Small , Morella caroliniensis (Mill.) Small , M. pensylvanica (Mirbel) Kartesz , M. cerifera (L.) Small, and a fifth species which until now has lacked an appropriate name at species rank in Morella (provided below). Each species is morphologically distinctive, and in general (see discussion below) does not show introgression, hybridization, or ambiguity when co-occuring in close proximity to congeneric taxa. Morella inodora is uncontroversially recognized at species rank. The other four taxa form two pairs, each of which has sometimes been treated at species rank, sometimes at variety rank , and sometimes lumped.

Morella pensylvanica has a largely northeastern distribution, rather common and widespread from Newfoundland west to Quebec and Ontario, south to s. Michigan, n. Ohio, w. NY, and MD, and along the coast to Dare County, North Carolina, where it reaches its southermost occurrence about 100 meters south of the southern town limit of Avon (formerly Kinnakeet). Morella caroliniensis has a more southern distribution, largely restricted to the southeastern Coastal Plain, but less commonly inland, from e. Texas (Pineywoods) and s. Arkansas east to the Florida peninsula (south to Highlands County), and north along the Atlantic Coastal Plain to s. New Jersey. The two are thus sympatric in the mid-Atlantic area from New Jersey to northeastern North Carolina. In that area, they differ in morphology, primary habitats, and primary geography. M. pensylvanica is largely a species of dry to moist, upland, sandy sites, especially maritime dunes, has narrower and more revolute leaves that are more deciduous, larger fruits, and whitish bark, while M. caroliniansis is a species of saturated wetlands, with broader and less revolute leaves that are more evergreen, smaller fruits, and dark bark; see Weakley & Southeastern Flora Team (2022a) for details. When they occur in proximity to one another in northeastern North Carolina and eastern Virginia, they generally retain these differences; but previous workers have been troubled with ambiguities, especially in southern New Jersey, and especially when dealing with herbarium specimens rather than the plants in the field. Wilbur’s (2002) dismissal of the taxonomic difference of these two species seems based in part on “herbarium botany” and his lack of familiarity with (especially) M. pensylvanica in the field. He opines that “in my experience, species are separable by more and stronger characters than those differentiating these alleged species,” but the relative convenience of the morphological characters used in the herbarium does not change the fact that these two species are morphologically distinctive across more than 95% of their collective distribution, and even in some parts of their shared (overlapped) distribution. I believe they therefore warrant recognition as separate entities and at species rank, that there are two entities on separate evolutionary trajectories, with the acknowledgment that some introgression or intermediacy is present in (especially) southern New Jersey. A deeper understanding of the situation there will require genetic analysis and perhaps local population studies.

Morella cerifera is the most abundant and widespread species of the genus in our region, with a similar though more extensive distribution than M. caroliniensis in the continental United States, but also extending extensively into the West Indies, Mexico, and Central America. In the United States, it is also now spreading in inland areas because of its horticultural use. This small tree or large, clump-forming shrub (to 15 m tall) is especially common in near-coastal wetlands, variously salt-influenced or fresh, but sometimes occurs in mesic or even sub-xeric upland sites, including longleaf pine flatwoods and dunes. A second entity, the “Dwarf Bayberry,” has been recognized (or not) at species or variety rank , and in various genera): Morella pumila (Michx.) Small , Cerothamnus pumilus (Michx.) Small , Myrica cerifera L. var. pumila Michx. , and Myrica pusilla Raf. Dwarf Bayberry is a low-growing, clonal shrub, usually 0.2–0.6 meters tall, and found in upland longleaf pine flatwoods and sandhills from southeastern Virginia to Florida, and west to southeastern Texas, strictly on the Coastal Plain and completely included within the distribution of Morella cerifera , usually in either deep sandy soils or in sandy spodosol soils (seasonally very dry, but with a spodic hardpan sometimes elevating the water table).

Dwarf Bayberry was first given a scientific name by André Michaux (1803), as Myrica cerifera L. var. pumila Michx. , which he described as “fruticulosa, foliis minoribus, magis cuneatis” [short-shrubby, with smaller leaves that are more narrowly cuneate at the base] and with habitat “in aridis, a Carolina ad Floridam” [in dry places, from Carolina to Florida ”]. A few decades later C.S. Rafinesque (1838) also named Dwarf Bayberry, as a species, with the description: “ Myrica pusilla Raf. cerif. pumila Bartr ? caule pumilo piloso angulato, fol. sessilib. obov. and cuneatis, apice ineq. serratis acutis, supra rugosis, subtus ferrugineis glabris, margine et nervo ciliatis—minute shrub, only 3–6 inches high, in Alabama and Florida, leaves very unequal and less than one inch long, Bartram calls them sinuate and yellow pulverulent.” Rafinesque’s references to Bartram and “cerif. pumila Bartr ” might suggest that Bartram named a taxon, but his “Travels” ( Harper 1958) do not show a nomenclatural act; clearly, though, Rafinesque’s mention of Bartram in regards to this species are derived from the following passages. On p. 187 (near Alachua, Florida) Bartram describes “we soon entered a level, grassy plain, interspersed with low, spreading, three leaved pine trees, large patches of low shrubs, consisting of Prinos glaber, low Myrica, Kalmia glauca, Andromedas of several species, and many other shrubs. …” On page 242 (near the Suwanee River, Florida), Bartram describes “some remarkable barren plains” and that “I was struck with astonishment at their dreary appearance; the view Southerly seemed endless wastes, presenting rocky, gravelly, and sandy barren plains, producing scarcely any vegetable substances, except a few scrubby, crooked Pine trees, growing out of heaps of white rocks …; with clumps of mean shrubs, which served only to perpetuate the persecuting power and rage of fire, and to testify the aridity of the soil; the shrubs I observed were chiefly the following, Myrica cerifera , two or three varieties, one of which is very dwarfish; the leaves small, yet toothed or sinuated, of a yellowish green colour, owing to a farinaceous pubescence or vesicula which covers their surfaces; Prinos, varieties, Andromeda ferruginae, Andr.nitida , varieties, Rhamnus frangula, Sideroxilon sericium, Ilex aquifolium , Ilex myrtifolium, Empetrum, Kalmia ciliata, Cassine, and a great variety of shrub oaks, evergreen and deciduous, some of them singularly beautiful; Corypha repens, with a great variety of herbage …” ( Harper 1958).

The descriptions by Michaux, Rafinesque, and Bartram each capture essential features of this species: its short, clonal habit, its growth in dry pinelands or “barrens” with other short heath and holly shrubs, the shorter and proportionately narrower leaves, very narrowly cuneate at the base, noticeably smaller towards the tips of the branches, and densely punctate glandular, giving a yellowish-green to ferruginous cast to the leaves, especially when young (see Fig. 21 for a representative modern specimen). In our experience, these two plants clearly behave as two distinct species.Particularly in outer Coastal Plain dryish pine flatwoods and sandhills, one can see the two growing interspersed (and also sometimes with Morella caroliniensis ), and maintaining their morphological distinctions. Even when these pinelands are fire-suppressed, the Dwarf Bayberry remains short and clonal, while Morella cerifera grows taller.

Through the 1800s and early 1900s, flora authors universally recognized this taxon, according it species rank ( Mohr 1901; Small 1903, 1913, 1933; Harper 1906) or variety rank ( Chapman 1860, 1883, 1897; Radford et al. 1968; Clewell 1985), and described its habitat as “sandy pine barrens” ( Chapman 1860, 1883, 1897), “open pine woods, dry sandy soil” ( Mohr 1901), “sandy barrens” ( Small 1913), “usually in dry or intermediate pine-barrens ( Harper 1906), “sandy acid pinelands” ( Small 1933), “sandy pinelands and low woods” ( Radford et al. 1968), or “a diminutive colonial plant of flatwoods” ( Clewell 1985). Mohr (1901) went out of his way to comment that the taxon is “strictly distinct.” The features that distinguish Dwarf Bayberry from Morella cerifera are often difficult to distinguish definitively in herbarium specimens, though, and this has contributed to the non-recognition of the Dwarf Bayberry as taxonomically separate from Morella cerifera . Beginning in the 1980s, this taxon was largely lumped into Morella cerifera ( Godfrey & Wooten 1981; Godfrey 1988; Wilbur 1994, 2002; Bornstein 1997; Wunderlin & Hansen 2003, 2011, 2015). Was this because of new studies or observations which cast doubt on the taxonomic recognition of the Dwarf Bayberry? No!—at least not as can be determined from any published work. Probably not coincidentally, this was a time when lumping became fashionable in eastern North American floras, as documented and discussed by Weakley (2005) —the Era of the Big Lump. Poorly prepared herbarium specimens, also lacking good information about the habit, height, and habitat of the plant collected, likely contributed to an uneasiness about the taxonomic status of Dwarf Bayberry.

Field observation across the region reveal that the two entities have distinctive distributions, distinctive habitats (with limited overlap), and distinctive morphology; when they do grow in mixed populations they remain clearly distinct. There is some evidence that they are phenologically separated in flowering when growing in proximity, with the Dwarf Bayberry flowering about 3 weeks later ( Mohr 1901; Weakley & Southeastern Flora Team 2022a). This is the hallmark of two species—acting as independent evolutionary entities. That the two species can be difficult to sort from herbarium specimens (though easier from field observations and images recorded on iNaturalist) should not be a basis for non-recognition or recognition at only varietal rank—species do not evolve for the convenience of human observers.

Two similar epithets have been formally applied to Dwarf Bayberry, one at the rank of variety and one at the rank of species: Myrica cerifera L. var. pumila Michx. 1803 and Myrica pusilla Raf. 1838 . Small accepted species rank for the taxon, and made new combinations for it at species rank in three genera: Myrica pumila (Michx.) Small 1896 , Morella pumila (Michx.) Small 1903 , and Cerothamnus pumilus (Michx.) Small 1913 . He erred, at least under the modern ICNafp, however, in making new combinations using Michaux’s epithet ‘ pumila’ at species rank, as Rafinesque’s epithet ‘ pusilla ’ has priority at that rank. If one accepts that the Dwarf Wax-myrtle should be placed in the genus Morella and at species rank (which we do), a new combination is needed.

Morella pusilla (Raf.) Weakley & D.B. Poind. , comb. nov. BASIONYM: Myrica pusilla Raf., Alsogr.Amer. 10.1838. We have been unsuccessful in locating any type or other original material of Rafinesque’s or Bartram’s. Importantly, Rafinesque (1838) seemingly distinguished between two taxa:18. Myrica sessilifolia Raf. … “probably the M.cerifera pumila of Mx.not Bartr.” and20. Myrica pusilla Raf. “cerif. pumila Bartr. ” Therefore,while we believe that Myrica pusilla Raf. and Myrica cerifera var. pumila Michx. are conspecific (and we disagree with Rafinesque’s tentative identification of his M.sessilifolia , “on the Sea Shores of New Jersey to Florida, shrub 4 to 8 feet high,” which seems to us like salt-spray-dwarfed Morella cerifera , with Michaux’s Myrica cerifera var. pumila ),it seems best and most conservative to treat Myrica pusilla Raf. and Myrica cerifera var. pumila Michx. as heterotypic.In the apparent absence of any original material for the Rafinesquian name, we therefore here designate a neotype for it using a specimen that matches Bartram’s and Rafinesque’s descriptions and is geographically very close to where Bartram found in the plants in present-day Alachua County. TYPE: U.S. A. FLORIDA: Alachua Co.:Longleaf Flatwoods Reserve, SE of Rochelle on W side of Hwy 325, sandy pine savanna, low shrub, mostly ∼ 0.75 m tall, 12 Mar 2022, M. Brock 4294 w/T. Murphy (NEOTYPE, designated here: APSC0136923). Fig.21 .

Note.— Michaux’s name does have original material,but no designated type.

Figures

FIG. 21. Morella pusilla, modern specimen from Alachua County,Florida,from near where seen by William Bartram,designated as neotype of Myrica pusilla Raf.