Reproductive biology and plant species selection for habitat restoration in the Venezuelan Gran Sabana plateau/Biologia reproductiva y seleccion de especies de plantas para restauracion de habitat en la Gran Sabana, Venezuela/Bilogia reproductiva e selecao de especies de plantas para restauracao de habitat na Gran Sabana, Venezuela.
Plant species selection for the restoration of borrow pits in the Venezuelan Gran Sabana Plateau was based in plant species having high reproductive performance. The reproductive traits used are: 1--high and continuous seed production, 2--breeding system that promotes self-pollination and low expression of deleterious characters, 3--floral morphology allowing a large diversity of visitors, 4--a generalist biotic pollination system or wind pollination, and 5--abiotic dispersal syndrome of diaspores and/or capacity for colonization and eventual immigration. Plant life form is considered as a complementary character: After evaluations of 14 characters (scale from 0 to 1 for each character), 45 of 157 plant species were selected having a score >65%. The highest store for woody species (69.75%) was lower than that in herbaceous species (81.12%). The highest scores of herbaceous species were for Perama galioides (Rubiaceae), Aristida torta, A. recurvata, Panicum cyanescens, Andropogon selloanus (Poaceae) and Rhynchospora caracasana (Cyperaceae), and the highest scores of woody species were for Gongylolepis benthamiana and Chromolaena laevigata (Asteraceae). Reproductive store (selected/non-selected species), natural distribution (disturbed/undisturbed distribution), and colonization of borrow pit (colonizing/non-colonizing species) interact significantly in the three factor dependence analysis ([chi square] = 6.1, df = 1: P= 0.013519), indicating dependence of these variables on the colonization process. The combination of high reproductive score. (70-81%), natural distribution on disturbed areas and capacity for spontaneous colonization of borrow pits is the best combination of traits for herbaceous species, other characters of which must be evaluated to design management and restoration plans for degraded areas.
KEYWORDS Degraded Land / Dispersal Syndrome / Floral Morphology / Gran Sabana Plateau / Pollination / Restoration
El uso de caracteristicas reproductivas en la seleccion de plantas para la restauracion de areas profundamente perturbadas (prestamos) en la Gran Sabana se baso en la seleccion de especies con una alta capacidad reproductiva utilizando las siguientes caracteristicas reproductivas: 1- elevada y permanente produccion de semillas, 2- sistema reproductivo que promueva autopolinizacion y baja expresion de caracteres deletereos, 3- morfologia floral que permita la polinizacion por una amplia diversidad de visitantes, 4- sistema de polinizacion generalista o polinizacion por el viento, y 5- sindromes de dispersion de diasporas abiotico y/o con capacidad de colonizacion y eventual inmigracion. La forma de vida de las plantas fue considerada como un caracter complementario. El analisis de 14 caracteres (escala 0-1 para cada caracter) permitio seleccionar 45 de 157 especies de plantas con puntaje >65%. La mayor puntuacion para especies lenosas (69,75%) fue menor que para especies herbaceas (81,12%). Las herbaceas con mayor puntuacion fueron Perama galioides (Rubiaceae), Aristida torta, A. recurvata, Panicum cyanescens, Andropogon selloanus (Poaceae) y Rhynchospora caracasana (Cyperaceae), y las lenosas con mayor puntuacion fueron Gongylolepis benthamiana y Chromolaena laevigata (Asteraceae). La condicion de seleccion reproductiva (seleccionadas/no seleccionadas), distribucion natural (en areas perturbada/no perturbadas), y colonizacion espontanea de prestamos (colonizadoras/no colonizadoras) interactuan significativamente en el analisis de dependencia ([chi square]= 6,1; df= 1; P= 0,013519) indicando dependencia de estas variables en el proceso de colonizacion. La combinacion de alto valor reproductivo (70-81%), distribucion natural en areas perturbadas y capacidad de colonizar los prestamos espontaneamente permite la mejor seleccion de especies herbaceas, que deben ser evaluadas en otros caracteres para disenar planes de manejo y restauracion de areas degradadas.
O uso de caracteristicas reprodutivas na selecao de plantas para a restauracao de dreas profundamente perturbadas (emprestimos) na Gran Sabana baseou-se na selecao de especies com uma alta capacidade reprodutiva utilizando as seguintes caracteristicas reprodutivas: 1- elevada e permanente producao de sementes, 2- sistema reprodutivo que promova autopolinizacao e baixa expressao de caracteres deleterios, 3- morfologia floral que permita a polinizacao por uma ampla diversidade de visitantes, 4- sistema de polinizacao generalista ou polinizacao pelo vento, e 5 - sindromes de dispersao de didsporas abiotico e/ou com capacidade de colonizacao e eventual imigracao. A forma de vida das plantas foi considerada como um carater complementario. A analise de 14 tipos de carater (escala 0-1 para cada carater) permitiu selecionar 45 de 157 especies de plantas com pontuacao >65%. A maior pontuacao para especies lenhosas (69, 75%) foi menor que para especies herbaceas (81,12%). As herbaceas com maior pontuacao foram Perama galioides (Rubiaceae), Aristida torta, A. recurvata, Panicum cyanescens, Andropogon selloanus (Poaceae) e Rhynchospora caracasana (Cyperaceae), e as lenhosas com maior pontuacao foram Gongylolepis benthamiana e Chromolaena laevigata (Asteraceae). A condicao de selecao reprodutiva (selecionadas/nao selecionadas), distribuicao natural (em areas perturbada/nao perturbadas), e colonizacao espontanea de emprestimos (colonizadoras/nao colonizadoras) interatuam significativamente na analise de dependencia ([chi square]= 6,1; df= 1; P= 0,013519) indicando dependencia destas variaveis no processo de colonizacao. A combinacao de alto valor reprodutivo (70-81%), distribuicao natural em areas perturbadas e capacidade de colonizar os emprestimos espontaneamente permite a melhor selecao de especies herbaceas, que devem ser avaliadas em outros tipos de carater para desenhar planos de manejo e restauracao de areas degradadas.
One of the greatest problems during the last decades has been the progressive anthropogenic disturbance of natural habitats. Many environmental agencies direct economic resources to stop non-reversible environmental damage and to promote spontaneous restoration. In many cases, programs of environmental management are designed for multiple purposes but privilege the use of woody species (forestation), while shrubs and herbaceous species are less commonly considered for habitat restoration. The main reason is that spontaneous colonization of degraded areas by herbaceous species commonly occurs at the beginning of natural succession. However, in deeply disturbed areas where the soil has been removed non-vegetated areas remain (Rosales et al., 1997). These disturbed areas are frequently planted with exotic species to avoid soil erosion. Bradshaw (1987) pointed out, however, that restoration of degraded areas would more likely be successful if native species were used. The current widespread interest in native herbs is due, in part, to the recent availability of plant material as well as recognition of the role of native herbal species in the restoration of biological diversity and the conservation of endangered species and habitats (Knapp and Rice, 1996). Restoration of plant communities structurally and functionally similar to those that pre-dated the site degradation could be accomplished if plant species from the same area were used in the restoration programs. Native species can be more appropriate than exotics because they are better adapted to local environmental conditions and seed and other propagules are locally available (Montagnini, 2001).
In the Gran Sabana Plateau, Venezuela, disturbed areas along the roads have remained without vigorous vegetation for 8 years since soil disturbance (Cuenca and Lovera, 1992: Lovera and Cuenca, 1996) and only a few native species have colonized these areas (Rosales et al., 1997). They represent lands where soil horizons have been partially or completely removed. These areas are known as borrow pits; in some cases erosion has generated large gravel pits with deep furrows (Rosales et al., 1997). Borrow pits differ from other disturbed areas in the Gran Sabana Plateau because after soil has been removed plant colonization does not occur spontaneously under natural conditions in a short time. One of the most common exotic species used to avoid soil erosion in Venezuela is Brachiaria decumbens (Poaceae), which is sown in borrow pits (disturbed areas) close to roads (Cuenca and Lovera, 1992). This herbaceous species was sown 6 years ago without success in the Gran Sabana Plateau (Cuenca and Lovera, 1992). In these areas, the abundance of B. decumbens declines in the years following sowing, and some native species may colonize the area; however, the process is very slow (Gisela Cuenca, personal communication). In this context, the goal for restoration must be understood as a general strategy to overcome the various barriers to natural recovery. In addition to autochthonous species in habitat restoration, plant species selection has to be based on their adaptability to difficult site conditions, their probable biotic and abiotic influence on site conditions, and their future reproductive capacities, among other variables.
Reproductive biology is one of the most important aspects that should be considered in plant species selection for habitat restoration. The attributes should ensure high seed production, low mortality risk, and sustainability of the colonizing population (Bawa el al., 1989). For example, weeds have reproductive and ecological traits that enhance their capacity to invade highly disturbed areas (Baker, 1974). The knowledge of plant species phenology, pollination, mating system and seed dispersal can refine our capacity to manage natural and disturbed areas for conservation and restoration. Selection of autochthonous plant species for restoration of degraded areas in the high basin of the Caroni River, Venezuela, was based on reproductive attributes which enhance biological success in marginal conditions. This is associated with life history of colonizing plants (Bazzaz, 1986).
The purpose of this study was to select native plant species with a high reproductive potential. In other words, this research intends to find plant species from herbaceous and shrubby communities in the high basin of the Caroni River in the Gran Sabana Plateau that have the combination of reproductive traits that allow them a high reproductive output. These traits are: 1-high and continuous seed production. 2-a breeding system that promotes self-pollination, 3- a floral morphology that allows a large diversity of floral visitors, 4- a generalist biotic pollination system or wind pollination, and 5- seed dispersal syndromes of diaspores with the capacity to colonize distant areas. In addition, the predictive value of reproductive attributes was tested for native colonizing plant species growing spontaneously on the borrow pits.
Plant species were selected from seven communities in the high basin of the Caroni River of the Gran Sabana Plateau, Canaima National Park, Bolivar State, Venezuela (Figure 1). These plant communities included shrublands, savanna, broad-leaved meadow, and secondary vegetation (Table 1). The annual average temperature is 20.6[degrees]C and annual precipitation is 2428mm, abundant throughout the year, with maximum in August and minimum from January to March (Ramirez et al., 1988). Additional details of soil, climate and vegetation of the area can be found in Ramirez et al. (1988), Dezzeo and Foster (1994) and Huber (1994).
The shrublands have a physiognomy and floristic composition typical of the white-sand associations in Guayana, dominated by herbs and shrubs, and small trees. The shrublands are surrounded by Trachypogon savanna and frequently associated with broad-leaved meadows. The savanna is a typical grassland community, where T. plumosum is the most abundant species. Broad-leaved meadows are dominated by Xyridaceae, Rapateaceae, and Eriocaulaceae, being Stegolepis ptaritapuiense (Rapateaceae) the most frequent species. Secondary vegetation is represented by the re-growth of a forest deeply disturbed by anthropogenic activity, and an area of savanna abandoned after agricultural practices (fallow).
Plant species were studied in their reproductive attributes for 23 months in 4 years (1993-1996). Epiphytes, vascular parasitic, and Lentibulariaceae were excluded from the analysis. Voucher specimens were identified and deposited in the Herbario Nacional de Venezuela (VEN) and in the Missouri Botanical Garden (MO).
Methods and the significance of character selection
Methods and criteria employed followed an initial proposal of plant species selection for degraded areas (Ramirez, 1997) that was modified, using 14 characters. These characters are associated with the reproductive success and plant species performance, and potentially involved in invasion success (Baker, 1974: Sutherland. 2004: Lloret et al., 2005).
The selection of characters was based on their relation to high reproductive output. Characters were similar or contrasting alternatives, not necessarily opposites. Character selection was made irrespective of the presence of correlations or association among characters: each character was selected by itself and only in some cases some correlation existed. A preliminary evaluation indicated that most of the characters were not related, and in those cases when correlation existed, the coefficients of determination were low (0.025 to 0.314). In this first approximation, characters were not differentially weighted. For discrete variables, two or more states of each character were considered. Character states were ranked from 1 to n according to their capacity to enhance and promote reproduction. Each value assigned was divided by the maximum obtained, resulting in relative proportions. For continuous variables, most of the expressions were direct estimates of reproductive output.
Arbitrarily, the cumulative count of approximately 9 points, 65% of the 14 maximum possible points, was considered as the minimum required for selecting a plant species for restoration. Plant species with a minimum of 65% of the points have many of the characters enhancing reproductive output, with approximately 2/3 of the total count. To assess the validity of this minimum value of 65% for plant species selection, a standard discriminant analysis was performed, using field records of colonizing plant species on borrow pits as a grouping variable and their reproductive attributes as independent variables. The capacity of plant species to spontaneously colonize borrow pits was obtained from previous studies (Rosales et al., 1997). Plant species from the seven communities were classified as invaders and non-invaders of borrow pits. Besides, plant species were classified by the areas where they grow naturally: disturbed areas and/or undisturbed areas. When plant species occurred in disturbed and undisturbed areas, they were computed for both conditions. The number of communities where plant species grow naturally and their presence in borrow pits were compared with one way ANOVA (Sokal and Rohlf, 1995). Values were square-root transformed before analysis.
The level of dependence among plant species selected (score >65%), those non-selected (score <65%), their natural distribution, and their capacity to naturally invade borrow pits was established using a log-linear analysis of frequency. The three factors were used initially, and then a two factor model (StatSoft, 2001) was used. When the log-linear analysis was significant, then residual frequencies (observed minus expected frequencies) were estimated for each cell of the two-factor comparison, and residuals were standardized and tested for significance. This analysis indicated which pair of variables deviated significantly from the expected values (Legendre and Legendre, 1993) and, therefore, had a larger contribution to the association.
Plant characters examined
Plant species were classified as trees, shrubs, lianas, and herbs. Lianas were divided into woody and nonwoody lianas or creepers, and herbs were categorized as annual or perennial. Points were assigned according to the species colonizing ability: more points for herbaceous. including non-woody lianas, than for woody species (Table II).
Ripe fruit phenology was monitored in each community bimonthly, between 1993 and 1996. Data recorded during this period were pooled, and then the monthly presence of ripe fruit was established for each species. Plant species were characterized by the number of months producing ripe fruits, from a maximum of 12 months.
Information about plant sexuality comes from a previous study (Ramirez, 1993a), and other plant species were evaluated in this study. The points were assigned following the progressive separation of sexual organs, maximum rank to hermaphroditic and minimum rank to dioecious species (Table II).
Temporal variation in sex expression
Information about the temporal variation in sex expression, used to rank plant species, comes from a previous study (Ramirez, 1993a) and un published data. Maximum points were assigned to adichogamous species and in a decreasing order from protandry to protogyny (Table II). To avoid empty cells in the model, dioecious species were included in this category with the lowest points, because they have no self-pollination, and fruit and seed set depend on pollination activity.
Information about herkogamy (the spatial separation of pollen presentation and pollen receptivity) comes from a previous study (Ramirez, 1993a) and unpublished data. Non-herkogamous species were assigned 3 points and 2 points were assigned to herkogamous species (Table 11). In addition, dioecious species were included in this category with the lowest points for three reasons: 1- to avoid empty cells in the model, and 2- dioecious species may be considered as herkogamous (see Webb and Lloyd, 1986). and 3- in dioecious species self-pollination did not occur, and fruit and seed set depend on pollination activity.
Information of pollination unit comes from a previous study (Ramirez, 2003). Pollination units were characterized according to flower arrangement in the inflorescence and pollinator behavior (Faegri and van der Pijl, 1979: Ramirez et al., 1990). Points were assigned according to the probability to be visited by a large variety of pollinators or potential pollinators, and hence promote fruit and seed set. Plant species with flower-inflorescence and inflorescence as a pollination unit were assigned 3 and 2 points, respectively. Flower as pollination units were assigned 1 point because they may represent the most specialized pollination units (Ramirez, 2003).
Information of floral types come from a previous study (Ramirez, 2003). A classification of blossom, flowers and inflorescences was used following the classification systems of Leppik (1969) and Faegri and van der Pijl (1979), modified according to Ramirez (2003). The progression from zygomorphic to amorphic blossom represents a series of decreasing complication and different levels of specialization. Therefore, points were assigned progressively from the more specialized to less specialized floral types (Table II), which is correlated with the fruit set (Ramirez, 2003).
Information about pollination comes from a previous study (Ramirez, 1993a) and unpublished data. Plant species were categorized according to the character of visits received (slightly modified from Faegri and van der Pijl, 1979). Points were assigned following decreasing levels of specialization, from specialized (monophily) to less specialized (polyphily) pollination systems. Anemophilous species were assigned the highest points because of their independence from biotic vectors.
Information about dispersal syndromes comes from a previous study (Lopez and Ramirez, 1989) and unpublished data. Dispersal syndromes were established according to the criteria of Dansereau and Lems (1957) and van der Pijl (1972). Points were assigned progressively from 1 to 5 following the level of dependency on specialized animals (Table 11).
Information about reproductive efficiency comes from previous studies (Ramirez, 1993b: Raimundez 2000) and unpublished data. Reproductive efficiency was established at four levels: 1- fruit set was determined by the proportion of hermaphrodite and/or female flowers per inflorescence that developed into mature fruits; 2- seed per ovule was determined by dividing the average number of seeds per fruit by the average number of ovules per flower: 3- seed abortion was determined directly in 50-100 mature fruits, and aborted seeds per fruit divided by the average number of seeds per fruit was used to determine the proportion of aborted seeds: 4- seed set or fecundity was defined as the proportion of well-developed seeds per ovule per inflorescence (Ramirez, 1992). In the case of seed per fruit, the value was obtained dividing the largest value of the number of seeds per fruit in all plant species considered by the number of seeds per fruit of each plant species, which resulted in a fraction from 0 to 1.
Results and Discussion
Plant reproductive characters and plant species selection
Of 157 plant species evaluated in 13 reproductive attributes and life forms, 45 (28%) species had more than 65% of cumulative points in the scale proposed, which included 41 herbaceous and three woody species (Table IV). The highest values were found in herbaceous species, which indicated that these plant species have reproductive attributes that could enhance colonization of degraded areas. However, the three woody species selected shared some reproductive attributes with the herbaceous species selected: hermaphroditism, adichogamy and wind dispersal. In addition, there were no plant species with the maximum of points (100%), which indicates the difficulty of getting specific trait combinations.
Reproductive traits in selected herbaceous species were similar in many cases. Similarity among herbaceous species stems from taxonomic affinity. Of the 41 herbaceous species, 21 were of the Cyperales order (11 Poaceae and 10 Cyperaceae), followed by eight Asteraceae, three Melastomataceae, and two Rubiaceae. The first group of 21 monocot species was anemophilous with amorphic floral traits, in many cases dispersed by granivourous or wind, one seeded fruits, and very different reproductive efficiency. The second group of herbaceous species differs from the first group in some attributes: zoophilous pollination, floral type, and many seeded per fruit, but also share some attributes with the first group: high reproductive efficiency and granivourous or wind dispersal.
Adichogamous and nonherkogamous species tend to be self-compatible and in many cases autogamous, because self-pollination is not avoided (Lloyd and Webb, 1986: Webb and Lloyd, 1986: Bertin and Newman, 1993). Adichogamy and non-herkogamy were found in many species (Aristida torta, A. recurvata, Panicum cyanescens, Andropogon selloanus, Perama galioides, Ludwigia erecta, Polygala adenophora, Borreria capimta and Axonopus anceps). Adichogamous species exhibir a lower frequency of cross-pollination compared to dichogamous species (Bertin and Newman, 1993) and non-herkogamy promotes self-deposition of pollen on the stigmas (Webb and Lloyd, 1986). Most of these plant species may be self-compatible. Self-fertilization in herbaceous species makes them successful weeds (Mulligan and Findlay, 1970). Self-compatibility has no deleterious consequences, and homozygosity may reduce genetic loads and increase seed set (Weins, 1984; Weins et al., 1987); normally outbred species response to inbreeding depression than normally inbred species (Richards, 1986). During restoration, relatively isolated populations, self-compatible species, may have less chance of genetic erosion. Self-pollination and the patchy natural distribution of the species are both likely to contribute to the low level of gene flow, and can facilitate the divergence of populations over small spatial scales (Knapp and Rice, 1996). In addition, autogamous self-compatible species allow a single plant or a few individuals to establish populations (Anderson et al., 1996).
Herbaceous species occurring in early seral stages frequently have anemochorous or epizoochorous dispersal syndromes (Opler et al., 1980). The presence of wind dispersal syndrome in the herbaceous and woody species selected agrees with the expected results. In this context, abiotic or anemochorous species should be selected for habitat restoration. However, some herbaceous species selected had a granivourous dispersal syndrome. Seed dispersal by granivoures depends on birds (Ridley, 1930), mammals (Janzen, 1984) and/or ants (van der Pijl, 1972). In spite of the generalist character of plant species dispersed by granivoures, the dissemination of seeds may be limited in the absence of their dispersing animals. This situation may be pronounced in areas where soil has been removed and plant cover is absent, such as the borrow pits in the Gran Sabana Plateau.
Reproductive efficiency of herbaceous species was high for A. torta, A. recurvata, P. cyanescens, Rhynchospora mexicana, P. galioides, L. erecta and P. adenophora, intermediate for Hypolytrum pulchrum and Rhynchospora rugosa, and low for T. plumosus, Echinolaena inflexa, A. anceps, Bulbostylis lanata and Lepidoploa ehretifolia. In a similar way, woody species show high (Chromolaena laevigata and Gongylolepis benthamiana) and intermediate (Mahurea exstipitata) values of reproductive efficiency. The success of invasive plants appears to be related to high seed production, allowing the initial establishment of large numbers of individuals (Anderson et al., 1996). In addition, ripe fruit phenology was longer for herbaceous than for woody species, and therefore reproductive efficiency is greater for herbaceous species. Extended reproductive activity increases the abundance of propagules and the probability of leaving offspring (Pianka, 1994). An organista can increase its reproductive output by breeding more often and breeding over a longer period of time (Pianka, 1994) and therefore, an active seed rain in the area, could improve establishment opportunities (Ramirez, 2002). This aspect has been demonstrated for alien plants on Mediterranean islands (Lloret et al., 2005). Besides, some plant species selected may have low sexual reproductive efficiency. Some of these plant species may show a high asexual propagation capacity, by stolons (i.e. H. pulchrum and E. inflexa). Plant species with asexual reproduction can be considered for revegetation plans of degraded areas because of a lower number of biotic interactions (pollination and dispersal) for seed production, and, therefore, plans for habitat restoration could be more successful under the two alternative modes of reproduction. Vegetative growth may enhance stand formation after initial colonization (Baret et al., 2005).
Plant species selection, natural distribution and colonization
Reproductive scores (comparing selected and non-selected species), natural distribution (comparing species occurring in disturbed and undisturbed sites) and colonization of borrow pits (colonizing and non-colonizing species) were significantly associated ([chi square]= 6.1; df= 1; P= 0.013519), which indicates the interdependence of these variables in the process of plant colonization. In this sense, plant species distribution and habitat type where plant species grow naturally must be considered as an important criterion for plant species selection for habitat restoration. The presence of species in disturbed areas (Table IV) shows their natural colonizing ability. The condition of selected and non-selected species is significantly associated with their natural distribution of plant species ([chi square]= 7.35; df= 1; P= 0.006688). Among selected species, 25 out of 44 plant species grow spontaneously in disturbed areas (Table III), which indicates their colonizing ability. However, plant species spontaneously colonizing borrow pits occur significantly ([F.sub.1,155] = 12.3: P = 0.000592) in more communities (X = 4.1 [+ or -] 2.4SD) than plant species that are non-colonizing in borrow pits (X= 2.5 [+ or -] 1.4SD), which indicates that plant species with broad distributions are better colonizers. This may be considered as an important criterion for species selection and management plans for habitat restoration. Among plants with a broad distribution and/or specially those growing naturally in disturbed areas are herbaceous species as P galioides (Rubiaceae). P cyanescens, T plumunosus. E. inflexa, A. anceps (Poaccae). H. pulchrum and R. rugosa (Cyperaceae), shruby species such as C. laevigata (Asteraceae), and M. exstipitata (Clusiaceae).
One of the characters occurring in most of the woody and herbaceous species selected was the low number of seeds per fruit, which seems to be primarily related with the taxonomic affinity of plant species (Poaceae, Cyperaceae, and Asteraceae). In the present study, the floristic evaluation of plant species growing in borrow pits in the Gran Sabana Plateau showed that many of the plant species had a low seed number per fruit, as was also shown by Rosales el al. (1997). This result is opposite to the general trend, where plant invasiveness is determined by high seed production (Naylor. 1984: Rejmanek and Richardson. 1996: Morgan el al., 2002: Murray: et al., 2002). Low seed numbers per fruit mar be selected in invading or colonizing species because of their reproductive significance. Low numbers of seeds per fruit may be related to the high efficiency in seed/ovule ratio (Uma Shaanker et al., 1988: Ramirez, 1992), and the advantage associated with the low pollen requirement and low competition among seeds (Nakamura. 1988; Uma Shaanker et al., 1988).
A large number of biotic interrelations may be considered a restrictive factor in colonization. The production and dissemination of seeds may be limited in the absence of their dispersing animals. Colonizing species found in degraded lands of the same geographic area studied, mainly showed abiotic reproduction modes, and the number of biotic interrelations was limited to one, when it occurred (Rosales et al., 1997). Under such circumstances, plant species with a low number of biotic interrelations can be considered as the most appropriate species to be used in the first stages of habitat restoration. The most important plant reproductive attributes for habitat colonization were ripe fruit phenology, adichogamy-non-herchogamy, anemophily or polyphily pollination, high reproductive efficiency, and abiotic or unspecialized seed dispersal. Moreover, the best choice for habitat restoration are those plant species with high scores, natural distribution on disturbed areas and natural invasion of borrow pits, such as A. torta, A. recurvata (Poaceae). B. capitata (Rubiaceae), H. pulchrum, Rhynchospora barbata (Cyperaceae) and E. inflexa (Poaceae).
Further studies must be considered before implementing management plans for habitat restoration in the Gran Sabana Plateau. Plant species selected by reproductive traits have to be examined for their recruitment capacity. The relationship between selected and non-selected species and natural colonization of borrow pits (Table III) was statistically significant ([chi square]= 11.04; dl= 1; P= 0.000891). Residual analyses showed that plant species selected (>65% of points) invaded borrow pits spontaneously. Spontaneous colonization of borrow pits can be considered as a measure of recruitment capacity. The results of discriminant analysis indicate that 66.7% (12 out of 18) of plant species colonizing borrow pits spontaneously are also classified as colonizing species according to reproductive attributes. Moreover, the reproductive attributes allow statistical discrimination of borrow pit colonizing and non-colonizing species (Squared Mahalanobis distance of 1.85; [F.sub.14,142]= 1.83: P= 0.038272). These results show that the reproductive attributes used in this study have a high predictive value in plant species selection for habitat restoration. For restoration purposes, plant species must establish themselves under harsh conditions and improve soil and other features of the environment for subsequent species. Reproductive biology as proposed in this study provides the basis of reproductive success in degraded areas. However, initial introduction of many plant species may be constrained by their obligate mycorrhizal association (Cuenca and Lovera. 1992: Lovera and Cuenca, 1996; Rosales et al., 1997: Cuenca et al., 2002) and the low percentage of germination in some herbaceous species (E. inflexa and A. anceps) studied by Cuenca et al. (2003). Initial habitat restoration depends on plant species recruitment success; then, germination and mycorrhizal-dependence information must be included in the plant species selection.
The author thanks H. Briceno for field and laboratory support; G. Cuenca for allowing the use of unpublished data; the Autoridad Gran Sabana and especially N. Vera ([dagger]), M. Marquez, R. Machuca and all the staff from Pampa Scientific Station at La Gran Sabana for field assistance; and to G. Agostini ([dagger]), L. Anderson, V.M. Badillo, R. Barneby ([dagger]), C. Benitez, P.E. Berry, B.M. Boom, L. Cardenas, G. Carnevali, N. Hensold, B. Holst, R. Leisner, J. Luteyn, P.J. Maas, G. Morillo, M. Ramia, G. Pedrali, J. Pipoly, G. Prance, C. Sastre, J. Steyermark ([dagger]), C.M. Taylor, S. Tillett, J.J. Wurdack ([dagger]), R. Kral, F. Zuluaga and J. Grande for plant species identification. This research was supported by the projects Seleccion de especies autoctonas de la Cuenca Alta del Rio Caroni (EDELCA) and CONICIT S1-96001695.
Anderson RC, Dhillion SS, Kelley TM (1996) Aspects of the ecology of an invasive plant, Garlic Mustard (Alliaria petiolata), in Central Illinois. Rest. Ecol. 4: 181-191.
Baker HG (1974) The evolution of weeds. Ann. Rev Ecol. Syst. 5: 1-24.
Baret S, Radjassegarane S, Bourgeois TL, Strasberg D (2005) Does the growth rate of different reproductive modes of an introduced plant cause invasiveness. Int. J. Bot. 1: 5-11.
Bawa KS, Ashton PS, Primack RB, Terborgh J, Nor SM, Ng FSP, Hadley M (1989) Reproductive ecology of tropical forest plants: research insights and management implication. Biology International Special Issue 21. UNESCO. Paris, France. 57 pp.
Bazzaz FA (1986) Life history of colonizing plants: some demographic, genetic, physiological features. In Mooney H, Drake JA (Eds.) Ecology of biological invasions of North America and Hawaii. Springer. New York, USA. pp. 96-110.
Bertin RI, Newman CM (1993) Dichogamy in Angiosperms. Bot. Rev. 59: 112-152.
Bradshaw A (1987) The restoration of derelict land and the ecology of ecosystems. In Jordan W, Gilpin M, Aber J (Eds.) Restoration Ecology: a synthetic approach to ecological research. Cambridge University Press. New York, USA. pp. 57-72.
Cuenca G, Lovera M (1992) Vesicular-arbuscular mycorrhizae in disturbed and revegetated sites from La Gran Sabana, Venezuela. Can. J. Bot. 70: 73-79.
Cuenca G, De Andrade Z, Lovera M, Fajardo L, Meneses E, Marquez M, Machuca R (2002) El uso de arbustos nativos micorrizados para la rehabilitacion de areas degradadas de la Gran Sabana, Estado Bolivar, Venezuela. Interciencia 27: 165-172.
Cuenca G, De Andrade Z, Lovera M, Fajardo L, Meneses E, Marquez M, Machuca R (2003) Pre-seleccion de plantas nativas y produccion de inoculos de hongos micorrizicos arbusculares (HMA) de relevancia en la rehabilitacion de Areas degradadas de la Gran Sabana, Estado Bolivar, Venezuela. Ecotropicos 16: 27-40.
Dansereau P, Lems K (1957) The grading of dispersal types in plant communities and their ecological significance. Contributions de I'Institut Botanique de I'Universite de Montreal No 71. Montreal, Canada. 51 pp.
Dezzeo N, Foster H (1994) Los suelos. In Dezzeo N (Ed.). Ecologia de la altiplanicie de la Gran Sabana (Guayana Venezolana). I. Investigaciones sobre la dinamica bosque-sabana en el sector S-E: subcuencas de los rios Yuruani Arabapo y Alto Kukenan. Scientia Guaianae 4. Caracas, Venezuela. 45-78 pp.
Faegri K, van der Piel L (1979) The principles of pollination ecology. Pergamon. Oxford, UK. 244 pp.
Huber O (1994) Vegetacion. In Dezzeo N (Ed.). Ecologia de la altiplanicie de la Gran Sabana (Guayana Venezolana). L Investigaciones sobre la dinamica bosque-sabana en el sector S-E: subcuencas de los rios Yuruani, Arabapo y Alto Kukenan. Scientia Guaianae 4. Caracas, Venezuela. 106-115 pp
Janzen DH (1984) Dispersal of small seeds by big herbivores: foliage is the fruit. Am Nat. 123: 338-353.
Knapp EE, Rice KJ (1996) Genetic structure and gene flow in Elymus glaucus (Blue wildrye): Implications for native grassland restoration. Rest. Ecol. 4: 1-10.
Legendre L, Legendre P (1993) Numerical Ecology. Elsevier. Amsterdam, Netherlands. 419 pp.
Leppik EE (1969) Morphogenic classification of flower types. Phytomorphology 18: 451-466.
Lloret F, Medall F, Bmndu G, Camarda I, Moragues E, Rita J, Lambdon P, Hulme PE (2005) Species attributes and invasion success by alien plants on Mediterranean island. J. Ecol. 93: 512-520.
Lloyd DG, Webb CJ (1986) The avoidance of interference between the presentation of pollen and stigma in angiosperms. I. Dichogamy. New Zeal. J. Bot. 24: 135-162.
Lopez M, Ramirez N (1989) Caracteristicas morfologicas de frutos y semillas y su relacion con los sindromes de dispersion de una comunidad arbustiva en la Guayana Venezolana. Acta Cient. Venez. 40: 354-371.
Lovera M, Cuenca G (1996) Arbuscular mycorrhizal infection in Cyperaceae and Gramineae from natural, disturbed and restored savannas in La Gran Sabana, Venezuela. Mycorriza 6:111-118.
Montagnini F (2001) Strategies for the recovery of degraded ecosystems: experiences from Latin America. Interciencia 26: 496-503.
Morgan A, Carthew SM, Sedgley M (2002) Breeding system, reproductive efficiency and weed potential of Acacia baileyana. Aust. J. Bot. 50: 357-364.
Mulligan GA, Findlay JN (1970) Reproductive systems and colonization in Canadian weeds. Cun. J. Bot. 48: 859-860.
Murray BR, Thrall PH, Gill AM, Nicotra AB (2002) How plant life-history and ecological traits relate to species rarity and commonness at varying spatial scales. Austral Ecol. 27: 291-310.
Nakamura HL (1988) Seed abortion and seed size variation within fruits of Phaseolus vulgaris: pollen donor and resource limitation effects. Am. J. Bot. 75: 1003-1010.
Naylor REI (1984) Seed Ecology. In Thompson RJ (Ed.). Advances in Research and Technology of Seeds. Part 9,3. pp. 61-93.
Opler PA, Baker HG, Gordon GW (1980) Plant reproductive characteristics during secondary succession in neotropical lowland forest ecosystems. Biotropica Succ. (Suppl. 12): 40-46.
Pianka ER (1994) Evolutionary Ecology. 5th ed. Harper Collins. New York, USA. 356 pp.
Raimundez E (2000) Evaluacion de algunos aspectos reproductivos y ecologicos de plantas de comunidades naturales de la Gran Sabana (Parque Nacional Canaima, Estado Bolivar). Thesis. Universidad Central de Venezuela. 203 pp.
Ramirez N (1992) Las caracteristicas de las estructuras reproductivas, niveles de aborto y semillas producidas. Acta Cient. Venez. 43: 167-177.
Ramirez N (1993a) Reproductive biology in a tropical shrubland of Venezuelan Guayana. J. Veg. Sci. 4: 5-12.
Ramirez N (1993b) Produccion y costo de frutos y semillas entre formas de vida. Biotropica 25: 46-60.
Ramirez N (1997) Biologia reproductiva y seleccion de especies autoctonas para la recuperacion de areas degradadas: metodos y significado. Acta Bot. Venez. 20: 43-66.
Ramirez N (2002) Reproductive phenology, life-forms, and habitats of the Venezuelan Central Plain. Am. J. Bot. 89: 836-842.
Ramirez N (2003) Floral specialization and pollination: a quantitative analysis and comparison of the Leppik and Faegri and van der Pijl classification systems. Taxon 52: 687-700.
Ramirez N, Gil C, Lopez M, Hokche O, Brito Y (1988) Caracterizacion floristica y estructural de una comunidad arbustiva en la Guayana Venezolana (Gran Sabana, Edo. Bolivar). Acta Cient. Venez. 39: 457-469.
Ramirez N, Gil C, Hokche O, Seres A, Brito Y. (1990) Biologia floral de una comunidad arbustiva tropical en la Guayana venezolana. Ann. Missouri Bot. Gard. 77: 383-397.
Rejmanek M, Richardson DM (1996) What attributes make some plant species more invasive? Ecology 77: 1655-1661.
Richards AJ (1986) Plant breeding systems. Allen & Unwin. London, UK. 529 pp.
Ridley HN (1930) The dispersal of plants throughout the world. Reeve. Ashford, UK. 744 pp.
Rosales J, Cuenca G, Ramirez N, De Andrade Z (1997) Native colonizing species and degraded land restoration in La Gran Sabana. Rest. Ecol. 5: 147-155.
Sokal R, Rohlf F (1995) Biometry. Freeman. San Francisco, USA. 887 pp.
StatSoft (2001) Statistica for Windows. StatSoft Inc. Tulsa, OK, USA.
Sutherland S (2004) What makes a weed a weed: life history traits of native and exotic plant in USA. Oecologia 141: 24-39.
Uma Shaanker R, Ganeshaih KN, Bawa KS (1988) Parent-offspring conflict, sibling rivality, and brood size patterns in plants. Ann. Rev. Ecol. Syst. 19: 177-205.
van der Pijl L (1972) Principles of dispersal in higher plants. Springer. Berlin, Germany. 161 pp.
Webb CJ, Lloyd DG (1986) The avoidance of interference between the presentation of pollen and stigmas in angiosperms II. Herkogamy. New Zeal J. Bot. 24: 163-178.
Weins D (1984) Ovule survivorship, brood size, life history, breeding system, and reproductive success in plants. Oecologia 64: 47-53.
Weins D, Calvin CL, Willson CA, Davern CI, Frank D, Seavey SR (1987) Reproductive success, spontaneous embryo abortion and genetic load in flowering plants. Oecologia 71: 501-509.
Received: 03/04/2005 Modified: 03/13/2006. Accepted: 03/14/2006.
Nelson Ramirez. Doctor of Science in Botanics, Universidad Central de Venezuela (UCV). Professor, UCV. Venezuela. Address: Centro de Botanica Tropical, Instituto de Biologia Experimental, Facultad de Ciencias, UCV. Aptdo. 48312, Caracas 1041A, Venezuela. e-mail: firstname.lastname@example.org
TABLE I CHARACTERISTICS OF THE STUDY SITES Locality Type of Community Coordinates Elevation (m) 1- Mareman Shrubland 5[degrees]44.49'N, 61[degrees]24.20'W 1,386 2- Liworiwo Shrubland 5[degrees]36.88'N, 61[degrees]29.66'W 1,208 3- Guamu-pe Shrubland 5[degrees]35.00'N, 61[degrees]43.00'W 1,350 4- 168 Km Broad-leaved Meadow 5[degrees]38.55'N, 61[degrees]22.94'W 1,343 5- Parupa Savanna 5[degrees]42.68'N, 61[degrees]31.30'W 1,302 6- Parupa Secondary forest, 5[degrees]44.42'N, untilled 61[degrees]32.54'W 1,300 7- Parupa Secondary savanna, 5[degrees]44.42'N, fallow 61[degrees]32.54'W 1,300 TABLE II QUALITATIVE CHARACTERS AND THEIR CORRESPONDING POINTS ASSIGNED IN A CONTINUOUS SCALE Characters Points (respective fraction) Life Form Annual herbs 5 (1.00) Perennial herbs 4 (0.80) Lianas 3 (0.60) Shrubs 2 (0.40) Trees 1 (0.20) Sexuality Hermaphrodite 5 (1.00) Andromonoecious 4 (0.80) Gynomonoecious 3 (0.60) Monoecious 2 (0.40) Dioecious 1 (0.20) Herkogamy Non-herkogamous 3 (1.00) Herkogamous 2 (0.67) Dioecious * 1 (0.33) Dichogamy Adichogamous 4 (1.00) Protandrous 3 (0.75) Protogynous 2 (0.50) Dioecious * 1 (0.25) Pollination Unit Flower-inflorescence 3 (1.00) Inflorescence 2 (0.67) Flower 1 (0.33) Floral type Amorphic 6 (1.00) Haplamorphic 5 (0.83) Actinomorphic 4 (0.67) Dish to bowl 3 (0.50) Stereomorphic 2 (0.33) Zygomorphic 1 (0.16) Pollination system Wind 4 (1.00) Polyphilous 3 (0.75) Oligophilous 2 (0.50) Monophilous 1 (0.25) Dispersal syndrome Wind and autochory 5 (1.00) Granivorous 4 (0.80) Epizoochorous 3 (0.60) Birds and mammals 2 (0.40) Birds 1 (0.20) * Dioecious species were included in these categories to avoid empty cells in the score of the plant species (see text for details). TABLE III FREQUENCY DISTRIBUTION OF SELECTED AND NON-SELECTED PLANT SPECIES RELATIVE TO NATURAL DISTRIBUTION IN THE AREA AND THE INVASION CAPACITY ON BORROW PITS Score [greater < 65% Total Plant species than or (Non- equal to] selected) N(%) 65% N(%) (Selected) N(%) Natural distribution Disturbed areas 25 (33.8) 49 (66.2) 74 (47.1) Undisturbed areas 19 (22.9) 64 (77.1) 83 (52.9) Natural invasion Colonizing borrow pits 11 (61.1) * 7 (38.9) 18 (11.5) Non-colonizing borrow pits 33 (23.7) 106 (76.3) 139 (88.5) Total 44 (28.0) 113 (72.0) 157 (100) N(%): Observed frequency and percentage. * Significant of residual analysis at P<0.05 TABLE IV PLANT SPECIES, FAMILY, DISTRIBUTION, LIFE FORM, NUMBER AND PERCENTAGE OF POINTS ACCUMULATED FOR 157 SPECIES STUDIED Plant species Family (1) Locality (2) Life form (3) Perama galioides RUB 1-2-3-4-5-6-7 AH Aristida torta ** POAC 5-6 PH Aristida recurvata ** POAC 4-5-7 PH Panicum cyanescens POAC 1-4-5-6-7 PH Andropogon selloanus POAC 5 AH Rhynchospora caracasana CYP 1-2-3-5 PH Rhynchospora mexicana CYP 5 PH Borreria capitata ** RUB 3-5-6 PH Rhynchospora velutina CYP 5 AH Hypolitrum pulchrum * ** CYP 1-4-5-6-7 PH Ludwigia erecta ONAG 6 AH Mesosetum sp. POAC 4 AH Rhynchospora rugosa CYP 5-6-7 PH Ludwigia sp. ONAG 6 AH Polygala adenophora POLYG 5 PH Axonopus anceps POAC 1-2-3-4-5-6-7 PH Rhynchospora barbata ** CYP 1-2-3-4-5-6-7 PH Echinolaena inflexa ** POAC 1-2-3-4-5-6-7 PH Bulbostylis lanata CYP 1-5-7 PH Gongylolepis benthamiana AST 1-2-3 SH var. pubescens Chromolaena laevigata AST 1-3-5:6-7 SH Irlbachia nemorosa GENT 1-3-4 AH Panicum micranthum ** POAC 5-6 PH Xyris fallax XYR 4 PH Desmoscelis villosa MELAST 5 AH Lepidoploa ehretifolia AST 5 PH Syngonanthus ERIOC 1-2-3-4 PH xeranthemoides Leiothrix flavescens ERIOC 4 PH Brachiaria decumbens ** POAC 6-7 PH Mahurea exstipitata CLUS 6 TR Trachypogon plumosum * ** POAC 1-2-3-4-5-6-7 PH Calea cardonae AST 2-4-6 PH Comolia microphylla * MELAST 2-3-4-6 PH Brocchinia reducta BROM 1-2-3-4 PH Calea nana AST 5 PH Mikania micrantha AST 6 LI Paspalum lanciflorum ** POAC 1-4-5-7 AH Rhynchospora pilosa CYP 1-2-3-4-5 PH Bulbostylis paradoxa CYP 5 PH Scleria distans CYP 5 PH Calea alchioides AST 6 PH Cyrilla racemiflora CYR 1-2-3-4 PH Irlbachia purpurascens GENT 1-5-6 AH Mikania psilostachya AST 3-6 LI Sipanea galioides RUB 1-3-4-5-6 PH Xyris roraimae XYR 4 PH Macairea lasiophylla MELAST 1-4-5 AH Raddiella esembeckii POAC 5-6 PH Vernonia bolivarensis AST 3 AH Calea divaricata AST 1 PH Nietneria paniculata LIL 1-4 AH Baccharis leptocephala AST 5-6-7 PH Siphanthera cordifolia MELAST 1-2-3-4-5-6-7 AH Xyris setigera Oliver XYR 1-2-3-4-5 PH Bulbostylis conifera * ** CYP 5 PH Stomatochaeta condensata AST 1-2-3-4 PH Calea lucidivenia * ** AST 3 PH Pagameopsis garryoides RUB 3 PH Buchnera pallustris SCROPH 1-2-4-5-6 PH Stegolepis angustata RAP 1-2-3-4 PH Stegolepis RAP 2-3-4 PH ptaritapuiensis Rhynchospora globosa CYP I-4-5 PH Xyris involucrata XYR 3-4-6 PH Xyris uleana XYR 2-4 PH Remijia densiflora ssp. RUB 2-3 SH stenopetala Psycotria sp. RUB 1-2-6 PH Lagenocarpus rigidus * ** CYP 1-2-3-4-5-6-7 PH Albolboda acaulis XYR I-2-3-4 PH Xyris bicephala XYR 3-4 PH Roupala montana PROT 1 TR Erythroxylum citrifolium ERYTH 6 SH Bonnetia sessilis THEAC 1-2-3-4 SH Austroeupatorium AST 6-7 SH inulaefolium Albolboda machrostachya XYR 4 PH var. robusta Coutoubea reflexa GENT 1-4-5 PH Declieuxia fruticosa var. RUB 1-3-5-6-7 PH fruticosa Passiflora auriculata PASS 4-6-7 LI Fimbristylis sp. CYP 4 PH Marcetia taxifolia * ** MELAST 1-2-3-4-5-6-7 SH Metastelma hirtella ASCL 1-5-6 LI Sabicea velutina RUB 1-5-6 LI Solanum (sec. Maurella) SOL 6 AH sp. Centropogon commas CAMP 6 PH Dalbergia monetaria FAB 6 TR Microlicia MELAST 2-3-4 PH benthamiana * ** Chamaecrista ramosa CAES 2 PH Thesium tepuiense SANT 4 PH Lindmania guianensis BROM 1-2-3-4 PH var. vestita Scleria cyperina * ** CYP 1-2-3-4-5-6-7 PH Digomphia laurifolia BIGN 1-2-3-4 SH Vellozia tubiflora VELL 2-5 PH Mandevilla benthamii APOC 1-2-3-4-5-6 PH Ternstroemia pungens THEAC 1-2-3 SH Sauvagesia guianensis OCHN 4 PH Clidemia sericea MELAST 1-5-6-7 PH Ternstroemia crassifolia THEAC 1-2-3 SH Sisyrinchium vaginatum IRID 6 PH Chamaecrista devauxii CAES 1-2-5 PH var. mollisima Chalepophyllum guianense RUB 1-2-3-4 SH Miconia ciliata MELAST 1-2-3-4-6 PH Galactophora APOC 2-3 SH schomburgkiana Ochthocosmus IXON 1-2-4 SH longipedicellatus Passiflora sclerophylla PASS 1-3-4 LI Tibouchina fraterna MELAST 1-2-3-4 SH Ditassa tatei ASCL 1-2-3 PH Macairea pachyphylla MELAST 3 SH Bonyunia minor LOG 1-2-5 SH Miconia sp. MELAST 6 SH Miconia sp. MELAST 6 TR Tococa nitens MELAST 1-2-3-6 PH Chaetocarpus EUPH 1-6 TR schomburgkianus Trimezia fosteriana IRID 3-4 PH Securidaca paniculata POLYG 6 LI Hirtella scabra CHRYS 2 SH Humiria balsamifera HUM 1-2-3-4 SH Palicourea crocea RUB 6 SH Calliandra resupina MIM 2 LI Philodendron ptarianun ARAC 1-2-3 PH var. rugosum Brocchinia steyermarkii BROM 4 PH Ochthocosmus anenuatus IXON 2 TR Mandevilla leptophylla APOC 5-6 LI Solanum strantoniifolium SOL 6-7 PH Befaria sprucei ERIC 1-2-3-6 SH Poecilandra pumila OCHN 2-4 SH Elaeoluma schomburgkiana SAPOT 1-2 TR Notophora schomburgkii ERIC 1-2-3 SH Macairea parvifolia MELAST 2-3 SH Blepharodon ulei ASCL 2-4 LI Pagamea capitata RUB 1-2 SH Dycimbe fraterna ** CAES 2 SH Ditassa bolivarensis ASCL 5-6 LI Clidemia pustulata MELAST 1-5-6 SH Blepharodon nitidus ASCL 4-5-6 LI Vaccinium euryanthum ERIC 1-2-3 SH Byrsonima verbascifolia MALP 1-5-7 PH Miconia phaeophylla MELAST 1-3-6 TR Poecilandra retusa OCHN 1-2-3 SH Vantanea minor HUM 2 SH Euphronia guianensis EUPHR 1-2-3 TR Byrsonima crassifolia MALP 1-3-5-6 SH Byrsonima concinna MALP 1-6 SH Vismia guianensis CLUS 3-5-6 TR Aegiphila integrifolia VERB 6 SH var. guianensis Ilex retusa AQUIF 1-2-3 SH Miconia sp. MELAST 6 SH Clusia grandiflora CLUS 3-6 TR Miconia ibaguensis MELAST 6 SH Heliamphora heterodoxa SARR 3 PH Clusia schomburgkiana CLUS 1-6 TR Psycotria barbiflora RUB 6 SH Ilex danielis AQUIF 1-6 SH Clusia pusilla ssp. CLUS 1-3-4 SH pusilla Abarema ferruginea MIM 1 TR Solanum campaniforme SOL 5-6 SH Clusia focklana CLUS 1-2 TR Ouratea gillejana OCHN 1-2-3 SH Myrsine coriaceae MYRS 3-6 TR Plant species Score % (4) Perama galioides 11.36 81.12 Aristida torta ** 11.19 79.94 Aristida recurvata ** 11.02 78.72 Panicum cyanescens 11.01 78.67 Andropogon selloanus 10.90 77.88 Rhynchospora caracasana 10.67 76.24 Rhynchospora mexicana 10.61 75.77 Borreria capitata ** 10.61 75.77 Rhynchospora velutina 10.43 74.51 Hypolitrum pulchrum * ** 10.28 73.44 Ludwigia erecta 10.27 73.37 Mesosetum sp. 10.20 72.83 Rhynchospora rugosa 10.18 72.70 Ludwigia sp. 10.15 72.48 Polygala adenophora 10.14 72.46 Axonopus anceps 10.07 71.92 Rhynchospora barbata ** 10.05 71.77 Echinolaena inflexa ** 9.82 70.15 Bulbostylis lanata 9.82 70.13 Gongylolepis benthamiana 9.76 69.75 var. pubescens Chromolaena laevigata 9.76 69.73 Irlbachia nemorosa 9.76 69.70 Panicum micranthum ** 9.60 68.55 Xyris fallax 9.59 68.49 Desmoscelis villosa 9.56 68.27 Lepidoploa ehretifolia 9.50 67.87 Syngonanthus 9.50 67.87 xeranthemoides Leiothrix flavescens 9.47 67.68 Brachiaria decumbens ** 9.38 67.00 Mahurea exstipitata 9.38 66.99 Trachypogon plumosum * ** 9.35 66.81 Calea cardonae 9.35 66.79 Comolia microphylla * 9.32 66.57 Brocchinia reducta 9.32 66.57 Calea nana 9.28 66.26 Mikania micrantha 9.25 66.10 Paspalum lanciflorum ** 9.24 65.99 Rhynchospora pilosa 9.16 65.45 Bulbostylis paradoxa 9.16 65.43 Scleria distans 9.15 65.38 Calea alchioides 9.15 65.35 Cyrilla racemiflora 9.14 65.30 Irlbachia purpurascens 9.14 65.26 Mikania psilostachya 9.13 65.21 Sipanea galioides 9.07 64.79 Xyris roraimae 9.06 64.70 Macairea lasiophylla 9.01 64.34 Raddiella esembeckii 9.01 64.33 Vernonia bolivarensis 9.00 64.28 Calea divaricata 8.98 64.15 Nietneria paniculata 8.96 64.02 Baccharis leptocephala 8.96 63.97 Siphanthera cordifolia 8.93 63.78 Xyris setigera Oliver 8.91 63.63 Bulbostylis conifera * ** 8.88 63.45 Stomatochaeta condensata 8.88 63.43 Calea lucidivenia * ** 8.86 63.25 Pagameopsis garryoides 8.82 62.97 Buchnera pallustris 8.80 62.86 Stegolepis angustata 8.75 62.53 Stegolepis 8.73 62.38 ptaritapuiensis Rhynchospora globosa 8.69 62.06 Xyris involucrata 8.62 61.60 Xyris uleana 8.62 61.60 Remijia densiflora ssp. 8.60 61.40 stenopetala Psycotria sp. 8.57 61.20 Lagenocarpus rigidus * ** 8.53 60.94 Albolboda acaulis 8.53 60.91 Xyris bicephala 8.41 60.05 Roupala montana 8.40 59.97 Erythroxylum citrifolium 8.37 59.76 Bonnetia sessilis 8.35 59.64 Austroeupatorium 8.35 59.63 inulaefolium Albolboda machrostachya 8.35 59.61 var. robusta Coutoubea reflexa 8.34 59.59 Declieuxia fruticosa var. 8.32 59.40 fruticosa Passiflora auriculata 8.31 59.36 Fimbristylis sp. 8.27 59.08 Marcetia taxifolia * ** 8.23 58.81 Metastelma hirtella 8.22 58.71 Sabicea velutina 8.21 58.66 Solanum (sec. Maurella) 8.21 58.62 sp. Centropogon commas 8.19 58.48 Dalbergia monetaria 8.12 57.97 Microlicia 8.10 57.87 benthamiana * ** Chamaecrista ramosa 8.07 57.65 Thesium tepuiense 8.03 57.39 Lindmania guianensis 8.02 57.27 var. vestita Scleria cyperina * ** 8.01 57.25 Digomphia laurifolia 7_92 56.59 Vellozia tubiflora 7.92 56.57 Mandevilla benthamii 7.90 56.42 Ternstroemia pungens 7.89 56.33 Sauvagesia guianensis 7.84 55.99 Clidemia sericea 7.84 55.99 Ternstroemia crassifolia 7.81 55.81 Sisyrinchium vaginatum 7.78 55.59 Chamaecrista devauxii 7.78 55.55 var. mollisima Chalepophyllum guianense 7.71 55.06 Miconia ciliata 7.70 54.99 Galactophora 7.68 54.86 schomburgkiana Ochthocosmus 7.65 54.61 longipedicellatus Passiflora sclerophylla 7.64 54.60 Tibouchina fraterna 7.63 54.48 Ditassa tatei 7.59 54.18 Macairea pachyphylla 7.58 54.17 Bonyunia minor 7.54 53.83 Miconia sp. 7.53 53.83 Miconia sp. 7.53 53.78 Tococa nitens 7.51 53.63 Chaetocarpus 7.49 53.50 schomburgkianus Trimezia fosteriana 7.47 53.33 Securidaca paniculata 7.44 53.18 Hirtella scabra 7.43 53.10 Humiria balsamifera 7.42 52.99 Palicourea crocea 7.41 52.92 Calliandra resupina 7.40 52.88 Philodendron ptarianun 7.39 52.76 var. rugosum Brocchinia steyermarkii 7.37 52.65 Ochthocosmus anenuatus 7.33 52.36 Mandevilla leptophylla 7.30 52.15 Solanum strantoniifolium 7.21 51.49 Befaria sprucei 7.16 51.17 Poecilandra pumila 7.13 50.90 Elaeoluma schomburgkiana 7.09 50.66 Notophora schomburgkii 7.03 50.25 Macairea parvifolia 7.03 50.20 Blepharodon ulei 7.02 50.15 Pagamea capitata 6.98 49.86 Dycimbe fraterna ** 6.96 49.72 Ditassa bolivarensis 6.96 49.70 Clidemia pustulata 6.95 49.67 Blepharodon nitidus 6.95 49.62 Vaccinium euryanthum 6.94 49.60 Byrsonima verbascifolia 6.93 49.50 Miconia phaeophylla 6.93 49.48 Poecilandra retusa 6.92 49.45 Vantanea minor 6.90 49.29 Euphronia guianensis 6.86 48.99 Byrsonima crassifolia 6.84 48.83 Byrsonima concinna 6.81 48.66 Vismia guianensis 6.80 48.56 Aegiphila integrifolia 6.79 48.48 var. guianensis Ilex retusa 6.53 46.64 Miconia sp. 6.50 46.46 Clusia grandiflora 6.50 46.41 Miconia ibaguensis 6.46 46.17 Heliamphora heterodoxa 6.42 45.89 Clusia schomburgkiana 6.42 45.83 Psycotria barbiflora 6.39 45.61 Ilex danielis 6.39 45.61 Clusia pusilla ssp. 6.39 45.61 pusilla Abarema ferruginea 6.28 44.89 Solanum campaniforme 6.08 43.46 Clusia focklana 5.92 42.26 Ouratea gillejana 5.76 41.17 Myrsine coriaceae 5.29 37.76 (1) Family name abbreviation. (2) Plant species distribution (see Table 1). (3) Life forms. TR: trees, SH: shrubs, LI: lianas, PH: perennial herbs, AH: annual herbs. (4) Percentages are given as a relative value to the maximum score of 14 points. * Plant species growing spontaneously in borrow pits (from Rosales et al., 1997) ** Plant species growing spontaneously in borrow pits (from Cuenca et al., unpublished).
|Printer friendly Cite/link Email Feedback|
|Date:||May 1, 2006|
|Previous Article:||Numerical 3D modeling for organic matter maturation in sedimentary basins with complex structures/Modelado numerico 3D de la maduracion de la materia...|
|Next Article:||Behaviors and attitudes associated to garbage disposition in non planned urban areas/Comportamientos y actitudes asociados a la disposicion de la...|