by
B.T. Styles, Forest Botanist
Department of Forestry, Commonwealth Forestry Institute,
South Parks Road, Oxford, OX1 3RB, U.K.
In the late 1940's FAO requested the assistance of the German forest pathologist Fritz Schwerdtfeger to investigate the depredations brought about by a particularly serious outbreak of the bark beetle Dendroctonus (Scolytidae) in the pine forests of Guatemala in Central America. Having arrived in the country his researches on the biology of the insect were immediately hampered because he could not obtain any information on the extent of the natural pine forests or on the individual species of which they were comprised. He was, therefore, forced to study the systematics of the local pines before starting work on an investigation of the beetle and the damage it had caused. Such a situation is not unknown today in many tropical countries where there is a lack of botanical expertise and a properly curated collection of reference herbarium specimens. Although Schwerdtfeger's final report is entitled “The Forest Entomology of Guatemala” only the first part dealing with a systematic account of the Pines was ever published (Schwerdtfeger, 1953). For its time it is a remarkably comprehensive taxonomic revision of this economically important group of trees in a then botanically little-known region of Central America. He recognized 9 taxa native to Guatemala and gave each a good botanical description together with distribution maps, keys and illustrations. Schwerdtfeger recognized P. tenuifolia Benth. [now P. maximinoi H.E. Moore] as a species distinct from P. pseudostrobus Lindl. He followed Loock (1950) in naming the mainland populations of P. caribaea var. hondurensis (Sénécl.) Barr. & Golf. as P. hondurensis Loock. He also gave subspecific rank to P. chiapensis (Mart.) Andresen which was then known as P. strobus var. chiapensis Mart. Unfortunately he, like several more recent workers, confused the commonly occurring large-coned P. michoacana Mart. with P. montezumae Lamb., a species which may not even occur as far south as Guatemala. This monograph is also important because in it Schwerdtfeger described a remarkable new species to which he gave the name ‘Pinus tecumumanii’. This name commemorates Tecun Umán, the last leader of the Quiché Indians in Guatemala who was killed in 1524 by Pedro de Alvarado of Spain during the conquest of the Central American Isthmus.
Unfortunately this binomial was invalid on publication because the new species was described in Spanish (not in Latin as the Rules of Botanical Nomenclature demand) and because the author failed to designate a holotype (a single dried specimen or nomenclatural type to which the new name is permanently attached).
Whilst all botanists and foresters who work on Central American pines unanimously agree that this taxon belongs to the closed-cone group subsection Oocarpae (sensu Little & Critchfield 1969; Barnes & Styles 1983) in the genus Pinus, its actual taxonomic rank and relationships within the group have been the source of argument and debate since its discovery. Even the spelling of the specific name has been the object of discussion and controversy.
Standley and Steyermark (1958) who studied the Pinaceae for the Flora of Guatemala considered Schwerdtfeger's discovery to be no more than a deviant form of P. oocarpa or [even more unlikely] a hybrid between P. oocarpa and P. pseudostrobus. Aguilar (1962) and Mittak (1977) also suggested that it is only a variety of P. oocarpa, [P. oocarpa var. tecumumanii], but again do not form the new combination correctly according to the Botanical Code. More recently Eguiluz and Perry (1983) have studied Schwerdtfeger's pine in detail in Guatemala and have concluded that it is a distinct species and have legitimized the specific name with a slight change in the spelling of the epithet to P. tecunumanii. These authors are also of the opinion that the species is most closely related to P. oocarpa.
In this short paper I shall present evidence to support my view that Schwerdtfeger's pine is neither a new species, nor a form of P. oocarpa, nor indeed a hybrid, but represents southerly populations of the well-known upland Mexican species P. patula which extend into Central America. Interestingly this is the name which Schwerdtfeger gave to the trees when he first collected them in Guatemala (Styles and Hughes, 1983).
The botanical features of this pine have already been described in detail by Eguiluz and Perry (1983), and Styles and Hughes (1983) and its excellent phenotypic and silvicultural characteristics are discussed by Barnes and Styles (1983). Schwerdtfeger's pine is remarkable in several ways. To foresters it probably has the best and most imposing form of all Central American pines and can reach the largest dimensions; trees with heights of over 50 m having been frequently recorded. The bole is normally very straight, up to 1.40 m in diameter, with a small, light crown of few, thin, lateral branches. The bark is extremely characteristic being strikingly reddish-brown in colour, almost papery in the upper part of the trunk and scaling in wafer thin, smooth flakes or strips. This contrasts strongly with the thick greyishblack, platy bark of P. oocarpa which is sloughed off in squarish chunky pieces. The reddish-flaky bark however strongly resembles that of typical P. patula. The majority of the needles are borne in groups of four per bundle enclosed in slender smooth sheaths, but fascicles with 3 and 5 needles occur. The needles are normally very slender and are either pendulous or spreading. The internal anatomy of the needles is very characteristic with 2 or 3 resin canals constantly found in the medial position in the chlorenchyma. This contrasts strongly with foliage of typical P. oocarpa which normally has stiff, broad needles with scaly black sheaths, mostly borne erect in fascicles of five. At least one and sometimes up to eight resin canals per needle, always occur in the sepal position in typical P. oocarpa. The number and position of resin canals in P. patula is identical to those found in Schwerdtfeger's taxon.
The female cones of Schwerdtfeger's pine strongly resemble those of P. patula in shape and are borne very sparingly on the tree, either singly or in pairs. They are usually smaller than those of P. oocarpa, rarely measuring more than 7.0 cm in length × 3.5 cm in breadth. They tend to be narrowly conoidal with a pointed apex and a rounded base, the scales having a varnished appearance when newly opened and a persistent or deciduous prickle. The cones, which are strongly serotinous, are pedunculate or sometimes completely sessile, both types occurring on the same tree throughout the entire range. They normally ripen between January and March but sometimes as late as April. Mature seed has also been collected in November in Honduras. Seed-yield per cone is generally low or very low. The cones of P. oocarpa are quite different in form, tending to be almost as broad as long, dark dull brown in colour with a ‘rose’ shape when open and wider scales. The base is distinctly flattened. Cones are usually borne abundantly on any particular tree and seed production is heavy, maturing in February and March. Schwerdtfeger's pine therefore differs markedly from P. oocarpa in its phenology, in that it flowers and cones over a longer period, and in its general morphology. Seeds are generally smaller in Schwerdtfeger's pine (see Barnes and Styles 1983).
Geographically and ecologically too this new taxon illustrates some interesting features. Schwerdtfeger mentioned that he had found it in three locations in Guatemala at altitudes between 1 900 – 2 700 m. More recently, it has been shown to be much more widespread in Central America, being particularly common in the highlands of Honduras and Nicaragua and El Salvador at altitudes ranging from 600 – 2 000 m above sea level (Styles and Hughes, 1983). On a recent collecting trip to S. Mexico its presence there was also confirmed in the States of Oaxaca and Chiapas in similar habitats. In Guatemala and Honduras the tree grows at altitudes above those normal for P. oocarpa, usually on the more fertile upland valley sites with higher rainfall and deeper soils. Forests with this pine often contain a mixture of higher altitude species such as P. ayacahuite Ehrenb., P. maximinoi H. E. Moore, P. pseudostrobus Lindl., Abies guatemalensis Rehder and Cupressus lusitanica Mill. The understorey flora is often rich and diverse, with a well-developed shrub and herb layer. Such forests generally merge into broad-leaved montana forest dominated by Quercus spp. Liquidambar styraciflua L., a magnificent broad-leaved timber tree, appears to be ubiquitously present at almost all sites as an associated species, perhaps indicating the wetter climatic and richer soil conditions. I have already indicated that this type of habitat characterises that in which P. patula is abundant in Central and Southern Mexico, but which is generally too high for P. oocarpa, although the two species do sometimes grow together in mixture here and in other parts of the range (Styles, 1976).
Because of the basic morphological, ecological and phenological similarities between Schwerdtfeger's taxon and P. patula outlined above, I am proposing that P. tecunumanii should be united with P. patula but given subspecific rank within it - viz. P. patula subspecies tecunumanii. This reflects the minor differences in which it departs from populations of the typical species.
In a previous paper, I have already produced evidence to show that P. oocarpa var. ochoterenae Mart. belongs to P. patula var. longipedunculata Loock and this fact is now widely accepted by botanists and foresters actively working in pine taxonomy (Styles, 1976). Still further evidence supporting my view is emerging from trials involving the former taxon.
Two trees of P. oocarpa var. ochoterenae have been raised in Zimbabwe at the John Meikle Forest Research Station (1 550 m) from seed collected by L.M. Hodgson in 1961 from El Tapanal, Oaxaca, Mexico. L.J. Mullin states (in litt.) “Their appearance has always been that of P. patula, especially in the reddish flaky bark, but the needles are less completely pendulous, although definitely within the range of P. patula in Zimbabwe. These two trees would not stand out in a plantation of P. patula as being noticeably different from the general population except in one respect - one tree is totally devoid of cones and the other has (25.5.78) only a few undersized ones. Coneless P. patula of this age (now 16 years) and at this altitude are not common in Zimbabwe but they are by no means unknown.”
Eguiluz and Perry (1983) state that P. tecunumanii is closely related to P. oocarpa var. ochoterenae but can be distinguished by its taller, broader and straighter trunk, and by minor cone and terpene differences. They admit, however, that trees with intermediate characteristics do exist. Clearly on these characters this pine is only a variation within a polymorphic species complex and is scarcely worthy of specific status.
It is my view that the chemo-taxonomic evidence which these authors publish to separate this variety of P. oocarpa and their P. tecunumanii is too sparse and is based on too few samples to be convincing.
Investigations of terpene differences in progress at Oxford suggest that the situation is less clear cut and that terpenes may be of little use in defining species limits in this closed-cone group of pines (CFI staff, personal communications). On evolutionary grounds it would also seem most improbable that a completely new species of pine would have evolved within the relatively small geographical area of C. America. All species or infraspecific taxa of pine occurring in the Central American Isthmus occur in Mexico as well, reflecting the north to south spread of the group from a centre of endemism in the north and central parts of that country.
From the provenance trials of P. oocarpa organized by the Commonwealth Forestry Institute over the past fifteen years (Greaves, 1979) it has become apparent that provenances from N. Nicaragua at age eight years are already showing significantly superior growth and form over all the others represented in the international trials being conducted in the tropics. Seeds of these provenances were obtained from natural forest populations at Yucul, Las Camelias and San Rafael in the Departments of Matagalpa, Nueva Segovia and Jinotega between 900 – 1 200 m altitude. Trees of these provenances are very vigorous in height growth, have straighter stems and more slender crowns, together with thinner bark and a greater bole diameter at breast height. Parent trees of these three provenances were obviously mistaken for P. oocarpa by CFI staff during the early days of their exploration and seed collecting in C. America before the taxonomy of the native pines had been worked out. Examination of herbarium voucher specimens and cones collected at the same time as the seed, together with botanical material from the progeny show that they all closely resemble Schwerdtfeger's pine in morphological features and must now be referred to as P. patula subsp. tecunumanii. The fact that these high altitude populations can grow naturally at much lower altitudes in the far south of the range has been admirably explained on climatic grounds by Hastenrath (1968). P. oocarpa, P. pseudostrobus and Cupressus lusitanica also behave similarly in Honduras where they occur at altitudes much lower than in Mexico and N. Guatemala.
Ecologically the forests of N. Nicaragua resemble the upland areas of Guatemala and Honduras and trees of the subspecies in the native forests all show the excellent form of P. patula. Nodal swellings were also noticed on the trees in 1971 when the first seed was collected. This is a characteristic of P. patula but not of P. oocarpa.
This taxon is probably under more threat of genetic erosion and in greater need of conservation than any other Central American Pine since it grows on the deeper more fertile valley soils which are being intensely encroached on for agricultural production. In some areas, e.g. near Siguatepeque in Honduras, whole populations have already been completely destroyed for maize cultivation and a similar situation is being witnessed in parts of Guatemala.
The formal taxonomy proposed is given as follows:
Pinus patula Schiede and Deppe in Schlecht. and Cham., Linnaea 6: 354 (1831) subspecies tecunumanii (Eguiluz and Perry) Styles. Type: Guatemala, Finca INAFOR, San Jeronimo, Baja Vera Paz. Eguiluz 2 (A-holotype; F; NCSC; ENCB; UACH).
Syn. P. tecunumanii Eguiluz and Perry, Ciencia Forestal 8 (41): 4 (1983). Type
as above.
P. tecumumanii Schwerdtfeger (1953) nom. invalid
P. oocarpa var. tecumumanii (Schwerdtfeger) Aguilar (1962) nom. invalid
The subspecies differs from the typical species in having short, broader needles which may be spreading or sometimes ± erect. The cones, which are smaller, are most often pedunculate.
ACKNOWLEDGEMENTS
I would like to thank my colleagues at the Commonwealth Forestry Institute, Oxford, particularly C. E. Hughes and P. S. McCarter, for their help in the study of this pine both in the field and in the laboratory. The views expressed, however, are entirely my own.
REFERENCES
Aguilar, J.I. 1962 Pinos de Guatemala. Ministerio de Agricultura. 33 p.
Barnes, R.D. and Styles, B.T. 1983 The Closed-Cone Pines of Mexico and Central America. Comm. For. Rev. 62 (2): 81–84.
Barrett, W.H.G. 1971 Variación de carácteres morfológicos en poblaciones naturales de Pinus patula Schlecht et Cham. en Mexico. Idia, Suppl. Forestal 7: 9–35
Eguiluz, T. and Perry, J.P. 1983 Pinus tecunumanii: una especie nueva de Guatemala. Ciencia Forestal 8 (4): 3–22.
Greaves, A. 1979 Descriptions of Seed Sources and Collections for Provenances of Pinus oocarpa. Tropical Forestry Papers 13. 144 p.
Hastenrath, S. 1968 Certain Aspects of the Three-Dimensional Distribution of Climate and Vegetation Belts in the Mountains of C. America and Sourthern Mexico. In Geo-Ecology of the Mountainous Regions of the Tropical Americas. (Colloquium Geographicum Bonn (Ed. Troll)) 9: 122–130
Little, E.L. and Critchfield, W.B. 1969 Subdivisions of the Genus Pinus (Pines). US Dept. Agriculture Forest Service. Misc. Publ. No. 1144.
Loock, E.E.M. 1950 The Pines of Mexico and British Honduras. Ed. 1. Bulletin No. 35, Union of South Africa Department of Forestry.
Mittak, W.L. 1977 Fortalecimiento al sector forestal. Guatemala. Estudios para la reforestación nacional. FAO/FO:DP/GUA/72/006. Documento de trabajo 25.64 p.
Schwerdtfeger, F. 1953 Informe al Gobierno de Guatemala sobre la entomologiá forestal de Guatemala 1. Los pinos de Guatemala. Informe FAO/ETAP. FAO, Rome No. 202. 58 p.
Standley, P.C. and Steyermark, J.A. 1958 Podocarpaceae, Pinaceae and Taxaceae in Flora of Guatemala. Fieldiana, (Botany): 20–63.
Styles, B.T. 1976 Studies of Variation in Central American Pines. I. The Identity of Pinus oocarpa var. ochoterenai Martinez. Silvae Genetica 25: 109–118.
Styles, B.T. and Hughes, C.E. 1983 Studies of Variation in Central American Pines III. Notes on the Taxonomy and Nomenclature of the Pines and Related Gymnosperms in Honduras and Adjacent Latin American Republics. Brenesia 21: 269–291
Manuscript received in July 1984
