Sargent, Charles S. 1889. Vaccinium hirsutum. Gard. & Forest. 2: 364, 365, fig. 119.
Ericaceae
Species Description - Plants crown-forming, with several stems, or suckering to fornm a compact colony, but rarely more than 0.' m. in diameter at the base, or larger in some forms, 1-3 (4) meters high. Leaves deciduous, green to subglaucous, or sometimes quite glaucous; the lower surface non-glandular, glabrous, pubescent on the veins or over the entire surface; narrowly to broadly elliptic, often ovate and apically acuminate, 2-3 cm. wide, 4-8 cm. long; the margin entire, subserrate, or sharply serrate. Corolla cylindraceous to broadly urceolate (or sometimes subcampanulate, or even subglobose), 6-10 mm. long, usually white, but often dull or pinktinged. Fruit blue, dull, or even black, 5-10 mm. in diam., of variable but usually good flavor, or even excellent.
Vaccinium albiflorum Hooker, Bot. Mag. 9: pl. 3428. 1835.
V. corymbosum var. glabrum A. Gray, Man. ed. 2. 250. 1856.
V. corymbosum var. amoenum A. Gray, Man. ed. 2. 250. 1856. Not V. amoenutn Ait.
V. corymbosum var. pallidum A. Gray, Man. ed. 2. 250. 1856. Not V. pallidutrn Ait.
V. corymbosum var. fuseatum A. Gray, Syn. Fl. N. A. ed. 2. 2: 23. 1886. Not V. fuseatum Ait.
Vaccinium vicinum Bicknell, Bull. Torrey Crub 41: 425. 1914.
Cyanococcus corymbosus Rydb. Brittonia 1: 94. 1931.
x Vaccinium corymbosum f. typicum Camp, Am. Midl. Nat. 23: 177. 1940.
x V. corymbosum f. albiftlorum (Hook.) Camp, Ibid.
x V. corymbosum f. glabrum (A. Gray) Camp, Ibid.
Tetraploid (2n = 48).
From the standpoint of its development, V. corymbosu.m is perhaps one of our most interesting species; certainly, as here defined, its variability requires some explanation. In the past, attempts have been made to resolve this complexity into a system by the application of varietal names, mostly derived from previously described species. Other authors who did not favor the use of subspecific names attempted to see various species in this population. And, being pressed for the identification of an accumulation of specimens, a few years ago the author of the present paper made an abortive attempt to solve the problem by splitting the population into a series of formae. The only advantage of this system lay in the fact that the names used did apply to plants within the range of corymbosum; that it included both tetraploids and diploids was lnot known at the time. 'The names of these forms were prefixed by the hybrid sign, also in an attempt to indicate the nature and origin of the general population. Information which has accumulated since that time indicates that the ancestry of corymbosum is even more complicated and involved than was then supposed, yet there seems to be no need to continue the use of the symbol. Regardless of its ancestry and variability, as here defined, the material deserves recognition under a normal binomial.
Whether or not one wishes to Fecognize subspecific units under corymbosum is purely a matter of taste. For the most part, those so far proposed have been essentially artificial and in only a slight way are related to the fundamental pattern of variability, serving only as a method of pigeonholing a variable series of specimens. In fact, only one, of those proposed as new can be said to have had any real significance; this was var. atrococcum, which has since been removed from corymbosum and recognized as a distinct species. Nor has the present author yet been able to devise any workable system of subspecific units in this species which would be biologically sound and at the same time be practical under the present system of nomenclature.
An understanding of the complexity of corymbosum cannot be obtained solely by a study of its materials. They are too variable and one must first look to other species. For those who cannot study the basic materials in the field, perhaps the next best way to gain an understanding of it is to read the descriptions of V. arkansanum, simulatum, australe, marianum, lamarckii, and brittonii. Then mix them together-much as if one were producing all possible hybrid combinations in a long-term breeding program, and in succeeding generations, covering at least 10,000 years, to back-cross, and re-cross further in all possible combinations- and then select all those plants over 1 m. in height whose leaves are over 2 cm. wide and 4 cm. long. The result would be Vaccinium corymbosumwhich is not an imaginary population but a very real one, and quite as complex as the results of our hypothetical experiment would have been.
It seems evident that the basic highbush elements of corymbosum came up out of the south during the Pleistocene and spread into the glaciated areas as new territory became available for plant occupation: these were V. arkansanum, simulatum, australe, and marianum. And today in appropriate segments of the population, one can still find plants of corymbosum which are quite similar to those of the southern species most directly connected by Pleistocene and post- Pleistocene migratioin routes (figs. 28-30). For example, the leaves of the western segment of corymbosum have textural qualities more nearly like those of arkansanum, and the fruits in the western part of the range, although often glaucous, average darker in color th,an in the eastern part. In certain parts of the south-central segment of corymbosum, in those areas most directly connected with the basic population of simnulatum by old migration routes, the leaves of about 50 per cent of the plants are quite simulatum-like. Also, when one recalls that the flowers of simulatum are cylindro-campanulate, one is not surprised in this same region to find simulatum-like flowers, but not always on the same plants with the simulatumm-like leaves. In these same areas, where the normal patterns of corolla characters have been reshuffled and unusual combinations of factors for -length, width, and size of orifice have come together in the same plant, a peculiar subglobose form of corolla sometimes appears. Then as one goes into the Lake Region of central New York, or toward the Atlantic seaboard, one notes the increase in the proportion of plants which are glabrous or nearly so, the much more conspicuous flowers, and the more glaucous fruit; in short, eastward, the plants are more austrate-like than in the western segment of corymbosum. In the northern and especially northeastern portion of corymbosum, the plants become more lamarckii-like or, in some instances, more brittonii-like. Briefly then, while the mixing' of the basic genetic elements of corymbosum would appear at first glance to be fairly general, a more careful analysis would indicate that the proportions of the various segregate biotypes follows a more or less regional pattern which is correlated with the primary distributions of the species which contributed them.
Sinee V. corymbosum was the first of this group to be described, and because of the elements which it contaiiLs, there may be some question why it has been dealt with-as a separate species; or, stated more properly, why I have recognized arkansanum, simulatum, australe, and marianum as species distinct from corymbosum. There certainly is precedent for treating them as one species. Today, arkansanum and simulatum are distributionally completely disjunct from the northern population, and eastward, only a narrow and probably migrationally ineffective corridor is open between australe, marianum, and corymbosum. As noted in another place (Camp & Gilly 1943, p. 348), since the Pleistocene there has been submergence along a portion of the Atlantic seaboard rather effectively isolating the southern and northern populations in that region; in the mid- Appalachians (which are lower than those farther south) the dense deciduous forests moved in, producing a discontinuity between simulatum and the northern population; and the post-Pleistocene xeric period drove a wedge of climate between arkansanum and the northern population which resulted in habitats unsuited to highbush blueberries. To say that the southern limit of corymbosum is the glacial,boundary is not to set an arbitrary line to facilitate the naming of specimens; it represents the southern boundary of an area in which a particular kind of population has developed. Because of its origin, corymbosum will contain some individuals which are quite similar to plants growing south of the glacial boundary, but taken as a unit-an independent interbreeding community-it is quite different from arkansanum, simulatum, australe, or marianum. By maintaining them as 'separate species a conscious effort has been made to 'have not only a functional nomenclatural system but also to keep it parallel with the phyletic development and dispersal of the group.
In the discussion of the distribution of V. australe it was noted that "somewhat similar forms [are] mixed with the V. corymbosutm population northward into Maine, central New York, and southern Canada." These seem not to be mixed with the general population, but occur in a definite pattern; one line (but poorly developed) is along the coastal swamps; the other (and much more pro,- nounced) is northward in the Hudson River valley and thence through the Champlain valley to the valley of the St. Lawrence River; an offshoot of this line is along the Mohawk River valley and into the Lake Region of central New York. It is not my intention to convey the idea that one will find plants in those places exactly like the australe plants of the mid-Atlantic seaboard swamps but, rather, that the population in the places indicated are more australe-like than in others. It seems likely that these plants represent a fairly recent re-introduction of autstrale along what are obviously easy migration routes, subsequent to the formation of the eastern segment of the highbush population during and immnediately after the Pleistocene from a combination of marianum and australe.
A complete analysis of corymbosum cannot be presented in this place. However, one more item should be noted. As mentioned previously, northward, and especially in the northeastern part of the range, the plants become more lamarckiilike, or in some areas more brittonii-like. Recently, Raup (1937) has shown that there has been a shift in the climate of New England and that species which at one time after the Pleistocene were farther north, are now graduLally disappearing, their places being taken by characteristically more northern species.. There is considerable evidence for a similar situation in the Vaccinium population of eastern Canada. While it is possible that the lower-statured and serrate-leafed forms of corymbosum might have been the only ones to have migrated into such areas as Nova Scotia, etc., it seems more likely that at some time since the last of the Pleistocene glaciations the taller, entire-leafed (i.e., australe x marianum) forms were growing there. It is very likely that those plants hybridized with the lowbush tetraploids just as they do today in, for example, Maine or Massachusetts. With the later shift in climate, there has been a selection toward biotypes which are more effective under the new conditions-that is, a progressive selection toward plants which are more and more lamarckii-like, or brittonii-like, depending upon which of the lowbush tetraploids had hybridized with the highbush material. These and other items pertinent to an understanding of the, local variability of corymbosum must await the opportunity for a more complete analysis of the origin and development of this species-a discussion which, to be fully developed, would necessitate a detailed review of the complete history of Pleistocene and, post-Pleistocene events in eastern North America. Such an analysis is outside the scope of the present paper.
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