Raymond P. Guries

GENETIC DIVERSITY AND POPULATION STRUCTURE IN PITCH PINE (PINUS RIGIDA MILL.)

Electrophoretic studies of protein polymorphisms in plants have focused upon herbaceous species, primarily inbreeding annuals, in efforts to characterize the levels and patterns of genic variation within and between populations (Clegg and Allard, 1972; Gottlieb, 1973, 1975; Levin, 1975, 1978; Levy and Levin, 1975; Schaal, 1975; Roose and Gottlieb, 1976; Brown et al., 1978; and others). These studies have indicated that predominantly outbreeding species maintain higher levels of intrapopulation variation than predominantly inbreeding species, while inbreeders exhibit a greater degree of population differentiation than outbreeders (Brown, 1979; Hamrick et al., 1979). This relationship is by no means perfect as Levin (1978) points out, because of differences in ecological requirements, breeding systems, dispersal mechanisms, evolutionary history, and other factors which affect the genetic system (Grant, 1958, 1971; Brown, 1979; Hamrick et al., 1979). Whether longlived perennials such as forest trees conform to the general pattern is still an open question. Allozyme studies of forest tree species have suggested that levels of genic variation are exceptionally high in natural populations (Tigerstedt, 1973; Rudin et al., 1974; Lundkvist and Rudin, 1977; Yang et al., 1977; Hamrick, 1979; Hamrick et al., 1979; Lundkvist, 1979), that certain populations appear to be moderately inbred (Rudin et al., 1974; Mejnartowicz and Bergmann, 1975; Phillips and Brown, 1977), and that populations have become differentiated over relatively short distances (Sakai and Park, 1971; Mitton et al., 1977). However, many inferences have been drawn from only one or a few loci, or only from loci known to be highly polymorphic. Valid estimates of mating system parameters may be obtained by examining only a few loci, but for estimates of heterozygosity, genic diversity, and the extent of differentiation, a large number of loci is preferred (Lewontin, 1974; Nei, 1975). As part of a continuing study of the genetics and ecology of pitch pine (Pinus rigida Mill.), we have surveyed 21 enzymatic loci in 11 populations across the species range. Pitch pine occurs from coastal Maine and southern Quebec to northern Georgia and from the Atlantic Coast to central Ohio, but almost always on relatively infertile sites. In spite of a history of overexploitation, it appears to have retained appreciable variation (Ledig and Fryer, 1974). Pitch pine demonstrates clinal patterns of variation in cone serotiny (Ledig and Fryer, 1972), wood properties (Ledig et al., 1975), and seedling growth (Ledig et al., 1976), as well as seed and needle characters (Ledig, unpubl.). It is uncertain whether these clinal patterns are the result of gene flow among pockets of differential fitness or reflect a continuous gradient in selection pressures (Endler, 1977; Givnish, 1981). The objectives of the present study were to determine the levels of genic diversity characteristic of pitch pine, and to examine the organization of genic variability within the species and the patterning of genic differentiation between populations. Among other comparisons, we contrasted marginal vs. central populations and the

The relation of growth to heterozygosity in pitch pine

The connection between fitness and heterozygosity has eluded geneticists for decades. The classic form of the Neo-Darwinian argument hypothesizes that heterozygosity confers genetic homeostasis (Lerner, 1954); i.e., multiple, molecular forms of the same enzyme endow the organism with a broader range of tolerance to environmental variation because different forms may differ in their optima for temperature, pH, and other factors (Johnson, 1976). In maize (Zea mays L.), inbred lines and their hybrids are similar in growth rate when raised under constant conditions at optimal temperatures, but hybrid superiority becomes progressively more obvious as conditions deviate from the optimum (McWilliam and Griffing, 1965). Apparently, homozygotes in maize can only deal successfully with a narrow range of conditions as compared to heterozygotes. In a variety of organisms, including butterflies, fish, and oysters, variance for morphological traits decreased with increasing heterozygosity at enzyme loci (Eanes, 1978; Mitton, 1978; Zouros et al., 1980), and bilateral symmetry, a measure of developmental homeostasis, increased with heterozygosity in lizards and bivalves (Soule, 1979; Kat, 1982). Growth rate increased with heterozygosity in oysters and salamanders (Singh and Zouros, 1978; Zouros et al., 1980; Pierce and Mitton, 1982). The perennial herb, cylindric blazing star (Liatris cylindracea Michx.), can be roughly aged by counting rings in the corm, the subterranean perennating organ. In natural populations, heterozygosity was higher among older than among younger individuals, suggesting poor survival for homozygotes (Schaal and Levin, 1976). Grown in a uniform environment, biomass production and reproductive potential of the herb were weakly, but positively, related to the level of enzyme heterozygosity. However, Mitton and colleagues (Mitton and Grant, 1980; Knowles and Grant, 1981; Mitton et al., 1981) noted conflicting results in forest trees, which are among the most polymorphic of organisms (Hamrick, 1979; Hamrick et al., 1979). In only one of three tree species was there a positive association between mean width of the annual ring, taken as a measure of growth and fitness, and heterozygosity. In two of the species, variance in ring width increased with increasing heterozygosity and in the third, it decreased. The relationship between growth and heterozygosity in trees is confusing, and more data are needed to draw firm conclusions. Our objective was to relate growth to heterozygosity in pitch pine (Pinus rigida Mill.), for which we had information on 21 enzyme loci in several populations. We were also interested in whether heterozygotes had greater longevity and whether annual growth was more or less well-buffered in heterozygotes than in homozygotes. A positive association be-

Ethnobotanical value and conservation of sacred groves of the Kpaa Mende in Sierra Leone

Sacred groves in the Moyamba District of Sierra Leone were assessed for their value to local herbalists and traditional folk medicine practitioners of the Kpaa Mende people. Herbalists (tufablaa) collecting in 23 sacred groves were interviewed regarding their general knowledge of medicinal plants, and their perceptions regarding changes in the occurrence of medicinal plants. Over 75 medicinal plant remedies are currently in use among the Kpaa Mende, with some plants reported here for the first time in terms of their medicinal uses in Sierra Leone. A significant feature of Kpaa Mende ethnobotany is the employment of 2 or more kinds of plants in combination as a remedy for particular afflictions. The discovery of rare and uncommon plants in the groves and their medicinal uses are discussed in terms of the role of the sacred groves in medicinal plant conservation.RésuméDes bosquets sacrés du district de Moyamba, Sierra Leone, furent évalués quant à leur utilité aux herboristes locaux et aux practiciens de médicine populaire du peuple Kpaa Mende. Des herboristes (tufablaa) récoltant dans 23 bosquets sacrés furent interrogés sur leur connaissance générate des plantes médicinales et sur lews impressions concernant les changements survenus à la flore médicinale. Plus de soixante-quinze re`edes d’origine végétale sont actuellement utilisés par les Kpaa Mende, quelques unes de ces plantes sont ici reconnues pour la premiére fois, pour leur valeur médicinale au Sierra Leone. Un aspect significatif de l’ethnobotanique des Kpaa Mende est l’utilisation combinée de deux ou plusiers types de plantes pour guérir certains maux. La découverte de plantes rares ou peu fréquentes dans les bosquets, ainsi que lew utilité médicinale, aménent à discutir le rôle des bosquets sacrés dans la conservation des plantes médicinales.

Spatial ecology and conservation of two sloth species in a cacao landscape in limón, Costa Rica

The spatial ecology of sloths was studied in an agricultural landscape in Limón Province, Costa Rica. Two sloth species, the three-toed sloth (Bradypus variegatus) and the two-toed sloth (Choloepus hoffmanni), actively used and traveled through a cacao agroforest and its contiguous living fence rows and riparian forests. This agroecosystem was embedded in an agricultural landscape dominated by banana and pineapple plantations and pastures with dispersed trees. The two-toed sloth (C. hoffmanni) was found in 101 tree species and used 34 for food; the three-toed sloth (B. variegatus) was found in 71 tree species and used 15 for food. Choice of preferred species differed between the two sloth species. Trees commonly used by sloths for food and/or refuge in the cacao agroforest included Erythrina poeppigiana, Cecropia obtusifolia, Leucaena leucocephala; in the living fence rows, Cordia alliodora, Erythrina poeppigiana, Ocotea sinuata and Trophis racemosa; in the riparian forests, Coussapoa villosa, Cecropia obtusifolia, Hura crepitans, Pterocarpus officinalis and Spondias mombin; and in the pastures with dispersed trees, Cordia alliodora, Coussapoa villosa, Erythrina poeppigiana, Ocotea sinuata and Hura crepitans. This study demonstrates the importance of the cacao agroforest as well as arboreal elements in other land uses in providing resources for sloth conservation in a larger agricultural landscape.

Patterns of hybridization and introgression between invasive Ulmus pumila (Ulmaceae) and native U. rubra.

Natural hybridization between introduced species and their native congeners occurs frequently and can create serious conservation concerns. Ulmus pumila (Siberian elm) is an introduced Asian elm species that has naturalized in the United States and is now considered invasive in 41 states. Red elm (U. rubra), a native to the eastern United States, often occurs in sympatry with Siberian elm, and the two species are thought to hybridize. Here, we genetically characterized reference populations of the two elm species to identify species-specific microsatellite alleles. These markers were used to classify individuals in putative hybrid zones as parental species or hybrids, assess the extent of hybridization, and track patterns of introgression. We identified nine U. rubra, 32 U. pumila, and 51 hybrid individuals in our hybrid zones. Of the 51 hybrids, 35 were classified as first-generation hybrids and 16 as backcrosses. The majority of the backcrosses (88%) were introgressed toward U. pumila. Our classification of genotypes was consistent whether we used manual classification, principal coordinate analyses or Bayesian clustering. We observed greater genetic diversity and new combination of alleles in the hybrids. Our study indicates widespread hybridization between U. pumila and U. rubra and an asymmetric pattern of introgression toward U. pumila.

GENETIC CONSEQUENCES OF SEED DISPERSAL IN THREE SYMPATRIC FOREST HERBS. I. HIERARCHICAL POPULATION‐GENETIC STRUCTURE

To examine the effects of seed dispersal on spatial genetic structure, we compare three sympatric species of forest herbs in the family Apiaceae whose fruits differ widely in morphological adaptations for animal‐attached dispersal. Cryptotaenia canadensis has smooth fruits that are gravity dispersed, whereas Osmorhiza claytonii and Sanicula odorata fruits have appendages that facilitate their attachment to animals. The relative seed‐dispersal ability among species, measured as their ability to remain attached to mammal fur, is ranked Sanicula > Osmorhiza > Cryptotaenia. We use a nested hierarchical sampling design to analyze genetic structure at spatial scales ranging from a few meters to hundreds of kilometers. Genetic differentiation among population subdivisions, estimated by average genetic distance and hierarchical F‐statistics, has an inverse relationship with dispersal ability such that Cryptotaenia > Osmorhiza > Sanicula. In each species, genetic differentiation increases with distance among population subdivisions. Stochastic variation in gene flow, arising from seed dispersal by attachment to animals, may partly explain the weak relationship between pairwise spatial and genetic distance among populations and heterogeneity in estimates of single locus F‐statistics. A hierarchical island model of gene flow is invoked to describe the effects of seed dispersal on population genetic structure. Seed dispersal is the predominant factor affecting variation in gene flow among these ecologically similar, taxonomically related species.

Phylogeny of Elms (Ulmus, Ulmaceae): Molecular Evidence for a Sectional Classification

The approximately 45 woody species of Ulmus (Ulmaceae) have been placed in five to nine sections on the basis of morphological characters. Cladistic analyses of chloroplast DNA restriction site variation were employed to examine phylogenetic relationships among 29 Ulmus accessions, including representatives from all proposed sections and subsections, and Zelkova serrata. Sufficient variation was detected to construct cladograms with branches both well-resolved and supported. The cpDNA results are largely congruent with those based on nuclear ribosomal DNA. Inclusion of 18 morphological/chemical characters further resolved relationships within the genus. Intrageneric relationships implied by the molecular and combined cladograms differ from previous classifications in a number of respects. Three species, U. crassifolia, U. serotina, and U. thomasii, which have been placed in two or three sections, were found to form a well differentiated monophyletic group (sect. Trichoptelea). The maintenance of sections Anisoptelea and Trichocarpus and the recog- nition of subsections Foliaceae and Glabrae within section Ulmus are not supported. The inclusion of U. mexicana, sometimes treated as the distinct genus Chaetoptelea, within Ulmus is supported. The molecular evidence supports the distinctiveness of U. rubra and the recognition of two subgenera: Oreoptelea (sects. Blepharocarpus, Chaetoptelea, and Trichoptelea s. 1.) and Ulmus (sects. Lanceifolia, Mi- croptelea, and Ulmus).

TheUlmaceae, one family or two? Evidence from chloroplast DNA restriction site mapping

The Ulmaceae is usually split into two subgroups, referred to as either tribes or more commonly subfamilies (Ulmoideae andCeltidoideae). The two groups are separated, with some exceptions, on the basis of leaf venation, fruit type, seed morphology, wood anatomy, palynology, chemistry, and chromosome number. Propositions to separate the two groups as distinct families have never gained general acceptance. Recent morphological and anatomical data have suggested, however, that not only is family status warranted but thatCeltidaceae are more closely related toMoraceae and otherUrticales than toUlmaceae. In order to test these alternative sets of relationships, restriction site mapping of the entire cpDNA was done with nine rare cutting enzymes using 11 genera ofUlmaceae s. l., three other families of theUrticales, and an outgroup family from theHamamelidae. Cladistic analysis of the data indicates thatUlmaceae s. l. is not monophyletic and that distinct families (Ulmaceae andCeltidaceae) are warranted; thatUlmaceae is the sister group toCeltidaceae plus all other families in the order; and thatCannabaceae might be nested withinCeltidaceae. Familial placements of various problematic genera (e.g.Ampelocera, Aphananthe) are resolved and character evolution of key morphological, anatomical, chemical, and chromosomal features are discussed.

The extent of hybridization and its impact on the genetic diversity and population structure of an invasive tree, Ulmus pumila (Ulmaceae).

Ulmus pumila is considered an invasive tree in 41 of the United States. In this study, we examined the extent of hybridization in naturalized populations of U. pumila, its impact on genetic diversity and genetic structure and its potential role in explaining the invasion process of U. pumila. Genetic analyses indicated widespread hybridization with native Ulmus rubra in naturalized U. pumila populations. Hybridization increased the genetic diversity of U. pumila populations and affected their genetic structure. The level of genetic diversity in ‘mature’ accessions, many of which may represent original plantings throughout the USA, was high and similar to the diversity of East Asian accessions. Hybridization with the native red elm may play an important role in the success of Siberian elm as an invader in temperate regions of the USA.

Biosystematics of the genus Pinus, subsection contortae

Gene frequency data from 42 isoenzyme loci were used to assess the phylogeny of taxa in the genus Pinus, subsection Contortae. The classification inferred from a phenogram based on Neis genetic distance measure (DN) was generally in good agreement with the current taxonomic treatment of the subsection. Pinus contorta appears to most closely resemble the ancestral taxon from which all other taxa in the subsection are derived. An alternative classification based upon Mahalonobis squared distances (DR) obtained from seed and cone measurements differed from the isoenzyme treatment by placing P. contorta subsp. murrayana in close association with P. virginiana.