CHAPTER 2 TAXONOMIC CLASSIFICATION OF PINES The major and minor southern pine species are of some of the historical events and may indicate fairly closely related, but their taxonomic relations future trends. have not been clearly delineated. This has led to rather important name changes in fairly recent years in regard to species, varieties, and races. TAXONOMY OF SOUTHERN PINES Names are important, of course, and when changes Even at this date universal agreement on the in names occur they bring about reviews of hypoth- name-terminology for southern pines has not been eses about relationships among species and groups achieved. Consequently, some confusion persists. of species that may or may not be important in Table 1 illustrates current grouping by Little and applied breeding. The characteristics of the indi- Critchfield (1969) vs. four earlier systems. vidual maternal or paternal parents are of primary The hard pines, subgenus Pinus (Diploxylon), importance and the bearing on the evaluation of the were rearranged from Shaw (1914) by Duffield progeny may be minimal, although the parents are (1952). This classification system was followed by designated as separate species, varieties, or races Critchfield and Little (1966) and Little and Critch- at different times by different taxonomists. field (1969). As shown in table 1, they retained An extremely large amount of silviculture and Sabinianae (group Macrocarpae of Shaw) as dis- forest products research has been done on the basis tinct and gave Latin names to Duffield's groups. of the tree species. The concept of grouping "similar Two pines, P. rigida and P. serótina, were trans- individual" trees under a species name has proven ferred from subsection Insignes to subsection Au- to be extremely useful in forest education, re- strales by Duffield (1952). Australes now includes search, management, and industry. Although indi- P. palustriSy P. taeda, P. echinata, P. glabra, P. vidual trees within different species may not repre- rigida, P. serótina, P. elliottii, P. pungens, as well sent the same degree of "similarity," average val- as nonlocal pines and P. caribaea, P. ocddentalis, ues for distinctive characteristics of each species and P. cubensis. Subsection Contortae contains two have great utility, and much research effort has southern pines, P. virginiana and P. clausa, plus been expanded in computing them. As intensity of P. banksiana of northern states and P. contorta of forest management and research increase with re- the western states, whose range overlaps with the spect to individual species, there is also an increase latter in west-central Canada. in recognition of the degree of "similarity" or lack of The species assigned to subsections 11 and 14 are it, and names or mathematical error terms are listed in the following excerpt quoted from "Sub- adapted to define the subdivisions of species. As divisions of the Genus Pinus (Pines)" by Little and might be expected, the traits or features of signifi- Critchfield (1969, p. 13-15): cant economic value may receive the most study. In the following chapters much will be said about Subsect. 11. Pinus subsect. Australes Loud., emend. variation among individuals or groups of individuals within species, or the degree of "similarity," and southern yellow pines special terms will be used to identify these differ- Pinus sect. ii. Ternatae § ix. Australes Loud., Arb. Frut. Brit. ences. Extremely large groups are recognized, but 4: 2255. 1838; emend. Holotype species: Pinus australis very small groups or individual trees are included Michx. f., Hist. Arb. Amér. Sept. 1: 64, t. 6. 1810 (P. palustris because genetics and tree breeding work is done on Mill, Gard. Diet. ed. 8, Pinus No. 14. 1768). this basis. Pinas palustris Mill., Gard. Diet. ed. 8, Pinus No. 14. 1768; longleaf pine. Southeastern United States. Pinus taeda L., Sp. PL 1000. 1753; loblolly pine. Southeastern TAXONOMY OF THE GENUS PINUS United States. Because of the importance of pines, a vast array Pinus echinata Mill., Gard. Diet. ed. 8, Pinus No. 12. 1768; of literature has accumulated on the phylogeny, shortleaf pine. Eastern United States. taxonomy, and species characteristics, which has Pinus glabra Walt., Fl, Carol. 237. 1788; spruce pine. South- eastern United States. been summarized by Mirov (1967) in a comprehen- Pinus rigida Mill., Gard. Diet. ed. 8, Pinus No. 10. 1768; pitch sive monograph "The Genus Pinus.'' Although the pine. Eastern United States. monograph includes the southern pines, there is a Pinus serótina Michx., Fl. Bor.-Amer. 2: 205. 1803; pond pine. need to review here some of the problems in Southeastern United States. taxonomy that have developed within the group. A Pinus pungens Lamb., Ann. Bot. 2: 198. 1805; Table-Mountain brief discussion will help develop an understanding pine. Eastern United States. 15 Pinas elliottii Engelm., Acad. Sei. St. Louis Trans. 4: 186, t. 1-3. studied intensively, P. echinata apparently has a 1380; slash pine. Southeastern United States. karyotype closely resembling that of loblolly and Pinus caribaea Morelel, Rev. florl. Côte d'Or L: 107. 1851; longleaf pines. On the basis of later work, it was Caribbean pine. Bahama Islands, Cuba, and Central America. concluded that P. echinata differs the most from Pinus occidenlalis Sw., Nov. Gen. Sp. PI. 103. 1788; West Indian the general pattern in Australes and it was the pine. Hispaniola and Cuba. most nearly similar to P. taeda (Saylor 1972). It Pinus cubensis Criseb., Amer. Acad. Mem., Ser. 2, 8: 530. 1862; Cuban pine. Cuba. was learned also that P. rigida had a distinguishing feature in which the b arm of a chromosome other Subsect. 14. Pinus subsect. Contortae Little & than number one is the longest. No differences Critchfield were detected between the two varieties of P. el- Pinus subgen. Pinus sect. Pinus subsect. Conlorlae Little & liottii. A very noticeable difference was found be- Critchfield, U.S. Dep. Agr. Misc. Pub 991: 15. 1966. Holo- tween the b arm sequence of the closely related P. type species: Pinus contona Üougl. ex Loud., Arb. Frut. Brit caribaea and P. elliottii. In Contortae, all species 4: 2292, fig, 2210-2211, 1838. have a b arm pattern of 5, 7, 9, except P. clausa, Pinus banksiana Lamb., Descr. Genus Pinus 1: 7, pi. 3, 1803 ; which differs at position 10. jack pine. Northeastern United States and nearly across Canada. Pinus contorta Dougl. ex Loud., Arb. Frut. Brit. 4: 2292, fig. 2210-2211. 1838; lodgepole pine. Western North America from Yukon and southeastern Alaska to northern Baja California, Pinus virginiana Mill., Gard. Diet. ed. 8, Pinus No. 9. 1768; Virginia pine. Eastern United States. Pinus chusa (Chapm.) Vasey ex Sarg., U.S. Census, 10th, 1880, vol. 9 (Rpt. Forests No. Amer.) : 199. 1884; sand pine. Florida and southern Alabama» Removal of P. resinosa from subsection Au- strales, where it was placed by Shaw (1914), ap- pears logical. In his karyotype analysis of several pine species, Say lor (1961) observed differences in chromosome shape between P. resinosa and both P. taeda and P. palustris. The anatomical features of the wood are sufficiently different to separate P. resinosa from southern pines (Hudson 1960). Kim (1963) also noted close similarities in the karyotypes of P. taeda and P. rígida. Karyotypes of these two southern pines and that indicated for P. echinata were similar. On the basis of interspecific hybridization work in Korea, Ahn (1963) concluded that crossabiUty in terms of production rate of fertile hybrid seed was Figure 13.—Pinus taeda chromosomes from a root tip sub- jected to 33 hours pretreatment in oxyquinoline. Ar- high between species which are closely related rows denote the smallest chromosomes with subme- taxonomically. dian centromeres. 1650x. (Saylor 1961) The karyotypes of some of the southern pines are very similar but do show differences among species (Saylor 1961) (figures 13 and 14). The b arm pat- A karyotype analysis of P. rigida, P. taeda, and terns and the location of the chromosomes with the their Fi hybrid was made by Kim (1963). He found most median and submedian centromeres (all three that the mean chromosome length of P. xHgitaeda features are possible diagnostic features of the is the shortest and that of P. rigida the longest. In karyotype) have been determined. According to general, there are close similarities between the Baylor's analysis, four different karyotypes exist. chromosomes of P. taeda and the hybrid. When The karyotypes of P. taeda and P. palustris agree chromosomes are arranged in descending order of in all three features and thus can be considered the length of the short arm, the lengths of the long similar. The others, P. strobus and P. resinosa, arms do not form continuous descending sequences. appear to differ sufficiently from this type and The chromosomes in which the long arms are out of among themselves to be regarded as distinctive. order are different in each species, as shown in The number and position of secondary construc- figure 14. In P. rigida, they are 4th, 6th, and 10th tions have thus far proved unreliable as diagnostic chromosomes, but 5th, 6th, and 9th inP. taeda, and features of the karyotypes. Although it was not 3rd, 6th, 8th, and 9th in the Fi hybrid. 16 ¡3 .S ^ g « g fl 50 fl a. SS o go o y^ 'E. 'S, •ä S ^ es s s ¿ ci ^ ü U w Q pq Tf t» Öi u5 o? có ¿ o j- C^ ^ -se ^—*s ^o Oi 'S ^ CO I c^ Ci (O ï >H ofl J J •«s»•Í3 •c es ^ ' 'S V CO ri I to I CO T. i S fe CO o •SX 1ce I" ki X XI 0 -ft, «• M w H ^ . S s "^ ^ s 1 I • &. fe Ö ^ io 11 ¿^-+0 •^o s O ■io CO CO II -♦0 I ^w' to g -^Î- ^-40 ^ to •c 5Í § Ö 1 4 s is .1 .1 >H 1 9 Cembra 9 robus >H mbra fe fe pq 9 lí fe H CO ^ i I Si 1.