Acacia Aroma Research Articles

Evaluation of the Subchronic Toxicity of Two Extracts of Tusca Leaves (Acacia aroma) on Rats’ Kidneys, Liver, and Stomach

Background: Acacia aroma (A. aroma), or Tusca, is a South American plant frequently used in medicine. We recently reported the antiulcer effect of two Tusca leaf extracts in rats: a 5% infusion and a 10% hydroalcoholic. This study aimed to investigate the in vitro cytotoxicity and the in vivo oral subchronic toxicity of these two extracts in rats. Methods: Cytotoxicity was evaluated through cell viability assays using the 50% lethal concentration (LC50) on lung cells, which was calculated for each extract. Oral subchronic toxicity was studied in Wistar rats, and the clinical parameters were determined during a 90-day treatment period. Following the experimental period, biochemical parameters were analyzed, and histopathological analyses of the stomach, liver, and kidneys were performed. Results: The in vitro cytotoxicity was low in both extracts (LC50=966.78±48.34 µg/ml for the 5% infusion and 562.28±28.11 µg/ml for the 10% hydroalcoholic extract). The in vivo clinical, behavioral, and biochemical parameters, body weight, and food intake had no significant differences (P≥0.05) compared to the control group. There were also no histopathological alterations in the analyzed organs. Conclusion: The present study contributes to expanding the knowledge on the safety of the two extracts derived from A. aroma (5% infusion and 10% hydroalcoholic). Therefore, the extracts can possibly be used in the treatment or prevention of gastric diseases in future studies.

Gastroprotective Effect of Acacia aroma Gill. ex Hook. and Arn. Leaves Extracts in Gastric Ulcer Models in Rats

Background: Peptic ulcer is a disease caused by imbalance between protective and aggressive factors in the gastric mucosa. Acacia aroma Gill. ex Hook. and Arn. (tusca) is widely used in Argentinian’s folk medicine for gastrointestinal disorders. The present study was designed to evaluate the protective effect of two A. aroma leaf extracts, 5% infusion and 10% hydroalcoholic extract in experimental models of acute gastric ulceration in rats. Methods: The gastroprotective action of the extracts was evaluated in absolute ethanol-induced gastric lesion models in adult Westar rats through macroscopic, histological and biochemical analyses of the stomach and gastric wall. We also determined the effects on the gastric juice parameters with a pylorus ligature model in rats. Evaluation of the acute toxicity of each extract was performed in adult normal Wistar rats. All results were statistically analyzed. Results: The lowest effective dose was 150 mg/Kg for each extract. Both of them showed a high protection of the mucosa against absolute ethanol. Pre-treatments with the extracts produced a significant increase in adherent mucus. These extracts showed a free radical scavenging capacity and they caused a significant reduction of the malondialdehyde, reduced glutathione levels, catalase and myeloperoxidase activities. The animals presented no signs of acute toxicity indicating a high safety margin for both extracts. Conclusion: This study shows for the first time the gastroprotective efficacy of 5% infusion and 10% hydroalcoholic extract of A. aroma leaves, highlighting their benefits as a prophylactic approach to maintain the integrity of the gastric mucosa.

Evidence of local adaptation and stabilizing selection on quantitative traits in populations of the multipurpose American species Acacia aroma (Fabaceae)

Abstract Economically and ecologically important quantitative traits of Acacia aroma are related to life history and the size and shape of fruits and leaves. Substantial variation is observed for these traits in natural populations, suggesting a possible genetic basis that could be useful for selection programmes. Our objective was to detect signals of selection on 12 phenotypic traits in 170 individuals belonging to seven populations of A. aroma in the Chaco Region of Argentina. Phenotypic traits were compared with molecular markers assessed in the same populations. Here, we search for signatures of natural selection by comparing quantitative trait variation to neutral genetic variation through the PST–FST test. We further test for differences among populations for the 12 phenotypic traits, an association of phenotypic variation with environmental variables and geographical distance, and we compare the power of discrimination between the phenotypic and AFLP datasets. The PST–FST test suggested directional selection for tree height and stabilizing selection for the remaining traits. Analyses of variance showed significant differentiation for eight phenotypic traits. These results suggest selecting among provenances as a management strategy to improve tree height (which showed divergent selection), whereas significant genetic gain for the other traits might be obtained by selection within provenances.

Enhanced oxidative stability of meat by including tannin-rich leaves of woody plants in goat diet.

ObjectiveThe aim of this study was to evaluate the effect of dietary incorporation of tannin-rich woody species on meat oxidative stability, carcass traits and meat quality in goats.MethodsTwo tannin-rich species were tested using a three-treatments feeding trial, where treatments consisted of: Larrea divaricata and Acacia aroma both at 12.5% in dry matter basis of the diet and a control diet (alfalfa hay). All feeding diets were iso-protein and iso-energy. Carcass conformation, carcass compactness, carcass fatness and subcutaneous fat deposition were evaluated. Intake, liveweigh, Longissimus thoracis et lumborum muscles of goats were analyzed in order to evaluate quality parameters such as pH value, instrumental color evaluation, water holding capacity, total phenolic content, antioxidant activity, meat oxidative stability and fatty acid profiles in meat.ResultsFeed intake, liveweight gain, carcass, and meat traits did not differ among treatments. Changes in meat lipid profile among treatments were observed for oleic and elaidic acid contents. Meat total phenolic content and antioxidant activity did not differ among treatments; although, meat oxidative status after storage at room temperature, as well as under refrigerated and frozen conditions were different between control and both supplemented groups.ConclusionThe inclusion of Acacia aroma and Larrea divaricata leaves in goat diet enhanced meat oxidative stability. Modulation of the ruminal biohydrogenation of fatty acids produced by condensed tannins of these plant species need to be further investigated.

Spatial genetic structure within populations and management implications of the South American species Acacia aroma (Fabaceae).

The identification of factors that structure intraspecific diversity is of particular interest for biological conservation and restoration ecology. All rangelands in Argentina are currently experiencing some form of deterioration or desertification. Acacia aroma is a multipurpose species widely distributed throughout this country. In this study, we used the AFLP technique to study genetic diversity, population genetic structure, and fine-scale spatial genetic structure in 170 individuals belonging to 6 natural Argentinean populations. With 401 loci, the mean heterozygosity (HE = 0.2) and the mean percentage of polymorphic loci (PPL = 62.1%) coefficients indicated that the genetic variation is relatively high in A. aroma. The analysis with STRUCTURE showed that the number of clusters (K) was 3. With Geneland analysis, the number of clusters was K = 4, sharing the same grouping as STRUCTURE but dividing one population into two groups. When studying SGS, significant structure was detected in 3 of 6 populations. The neighbourhood size in these populations ranged from 15.2 to 64.3 individuals. The estimated gene dispersal distance depended on the effective population density and disturbance level and ranged from 45 to 864 m. The combined results suggest that a sampling strategy, which aims to maintain a considerable part of the variability contained in natural populations sampled here, would include at least 3 units defined by the clusters analyses that exhibit particular genetic properties. Moreover, the current SGS analysis suggests that within the wider management units/provinces, seed collection from A. aroma should target trees separated by a minimum distance of 50 m but preferably 150 m to reduce genetic relatedness among seeds from different trees.

Exploring the biological activity of condensed tannins and nutritional value of tree and shrub leaves from native species of the Argentinean Dry Chaco.

Tropical tree or shrub leaves are an important source of nutrients for ruminants and a potential source of biologically active compounds that may affect ruminal metabolism of nutrients. Therefore, eight woody species from the native flora of Argentinean Dry Chaco, rich in secondary compounds such as condensed tannins (CT), were assessed for their nutritional value, CT fractions and in vitro true digestibility of dry matter, as well as biological activity (BA). Differences among species were found in contents of total phenol, protein-precipitating phenols (PPP), bound proteins to PPP (BP) and BP/PPP (P < 0.0001). The BP/PPP ratio reveals differences among species in potential BA as indicated by protein precipitation. The major CT of each species were isolated and purified for use as a standard. Although Schinopsis balansae had the most (P ≤ 0.05) total CT (19.59% DM), Caesalpinia paraguariensis had greater (P ≤ 0.05) BA with the most PPP (530.21% dry matter). Larrea divaricata, at 0.97, followed by Acacia aroma, at 0.89, had CT with the highest (P ≤ 0.05) BP/PPP ratios, followed by Prosopis alba (0.59). There were differences in nutritive value and bioactivity among species. Those with the greatest CT were not necessarily those with the most BA. Caesalpinia paraguariensis, S. balansae and L. divaricata were the most promising species as native forage CT sources. Cercidiurm praecox (20.87% CP; 18.14% acid detergent fiber) and Prosopis nigra (19.00% CP; 27.96% acid detergent fiber) showed the best (P ≤ 0.05) nutritive values. According to their nutritive traits, these species might be complementary in grass-based ruminant diets. © 2017 Society of Chemical Industry.

REVEGETACIÓN POST-INCENDIO EN MATORRALES DE ACACIA SPP. EN LAS SIERRAS DE CÓRDOBA, ARGENTINA CENTRAL

In the Sierras Chicas of Cordoba (Argentina), Acacia aroma and A. caven form substitution shrublands in sites where fire is the main factor modifying the landscape. The evaluation of the post-fire dynamics is important in order to study the dynamic of vegetation recovery, as an ecological strategy for natural recovery of fire-prone environments. The objective of this work was to identify the colonizing species in the affected site, its colonization mechanisms and velocity of recovery in the disturbed environment, as well as the ecological succession in the short term. Revegetation was studied in a burned woodland originally dominated by Acacia aroma and A. caven. The Quadrat method was applied over 50 x 50 cm sectors under the canopy of Acacia spp. species, and individual species coverage was measured in three moments after the fire in two topographic positions (i.e hill and half hill). Plant cover recovery was quick because of the occurrence of low intensity wildfire and the adequate provision in soil organic carbon, nitrogen and phosphorous content compared to control. Dominant species found (Acacia aroma, Acalypha communis, Cantinoa mutabilis, Cyperus rotundus, Nothoscordum gracile, Parthenium hysterophorus L., Setaria spp. y Sida argentina) had good ability for resprouting and germination due to the therophyte, hemicriptophyte and geophyte life form. They possess good ability for competition by rapid biomass production after disturbances and, in some cases, by the ability of production of allelopathic substances. According to ecological interactions, some species are favored by water accumulation into the soil profile in midlands zones (A. aroma, C. mutabilis y C. rotundus), while other species (Setaria spp., P. hysterophorus y S. argentina) would have better differential development in highlands, under the effect of lower total coverage.

The role of seed germination in the invasion process of Honey locust (Gleditsia triacanthos L., Fabaceae): comparison with a native confamilial

AbstractIdentifying plant traits that promote invasiveness has been a major goal in invasion ecology. Germination plays a central role in the life cycle of plants and therefore could be a key trait in determining species invasiveness. In this study, seed germination of two confamilial, co‐occurring species that share ecological characteristics, the exotic invasive Gleditsia triacanthos L and the native Acacia aroma Gillies ex. Hook. &amp; Arn., was compared. Seeds were obtained from individuals of three localities in the Chaco Serrano region of Córdoba, Argentina. Percent of seed germination and mean germination time were recorded in chemically and mechanically scarified seeds, and the former variable was also recorded in seeds subjected to: passage through the digestive tract of dispersers, fire simulations, fire simulation plus mechanical scarification, seed longevity, and dormancy break over time. In general, both species showed similar germination percentage. However, non‐scarified seeds of the exotic species lost physical dormancy when subjected to experiments of dormancy break over time, whereas, the native species had shorter mean germination time. The greater percentage of seed germination over time of the exotic species than of the native one might be triggering the spread of the former, whereas the shorter mean germination time might be hindering its expansion to more arid regions. The study of different mechanisms for achieving seed germination, particularly in hard seed species, could provide important information on the expansion of invasive species as well as useful knowledge for their management.

Evaluation of Cytotoxicity and Genotoxicity ofAcacia aromaLeaf Extracts

Acacia aroma, native plant from San Luis, Argentina, is commonly used as antiseptic and for healing of wounds. The present study was conducted to investigate the in vitro cytotoxicity and genotoxicity of hot aqueous extract (HAE) and ethanolic extract (EE) of A. aroma. The cytotoxic activity was assayed by neutral red uptake assay on Vero cell. Cell treatment with a range from 100 to 5000 μg/mL of HAE and EE showed that 500 μg/mL and 100 μg/mL were the maximum noncytotoxic concentrations, respectively. The CC50 was 658 μg/mL for EE and 1020 μg/mL for HAE. The genotoxicity was tested by the single-cell gel electrophoresis comet assay. The results obtained in the evaluation of DNA cellular damage exposed to varied concentrations of the HAE showed no significant genotoxic effect at range of 1–20 mg/mL. The EE at 20 mg/mL showed moderate genotoxic effect related to the increase of the DNA percentage contained in tail of the comet; DNA was classified in category 2. At concentrations below 5 mg/mL, the results of cytotoxicity and genotoxicity of aqueous and ethanolic extracts of Acacia aroma guarantee the safety at cell and genomic level. However further studies are needed for longer periods including animal models to confirm the findings.

Shrub biomass estimation in the semiarid Chaco forest: a contribution to the quantification of an underrated carbon stock

The quantification of biomass of woody plants is at the basis of calculations of forest biomass and carbon stocks. Although there are well-developed allometric models for trees, they do not apply well to shrubs, and shrub-specific allometric models are scarce. There is therefore a need for a standardized methodology to quantify biomass and carbon stocks in open forests and woodlands. To develop species-specific biomass estimation models for common shrubs, as well as a multispecies shrub model, for the subtropical semiarid Chaco forest of central Argentina. Eight shrub species (Acacia aroma, Acacia gilliesii, Aloysia gratissima, Capparis atamisquea, Celtis ehrenbergiana, Larrea divaricata, Mimozyganthus carinatus, and Moya spinosa) were selected, and, on average, 30 individuals per species were harvested. Their total individual dry biomass was related with morphometric variables using regression analysis. Crown area as well as crown-shaped variables proved to be the variables with the best performance for both species-specific and multispecies shrub models. These allometric variables are thus recommended for standardized shrub biomass assessments. By accounting for the shrub component of the vegetation, our models provide a way to improve the quantification of biomass and carbon in semiarid open forest and woodlands.

Physical dormancy and histological features of seeds of five Acacia species (Fabaceae) from xerophytic forests in central Argentina

Physical dormancy (impermeability of seed coats to water) is related to histological features of the seed coat. This mechanism has ecological importance since it determines the time and space of germination. The aim of the present study was to compare the histology and impermeability of the seed coat in five Neotropical Acacia species from xerophytic forests of central Argentina: Acacia aroma, A. caven, A. atramentaria, A. gilliesii and A. praecox. An imbibition experiment was performed to determine the presence or absence of physical dormancy. Seed coat structure was studied through histochemical analysis. The seeds of A. gilliesii and A. praecox were treated with ammonium ferrous sulfate to identify the sites of water entry. Acacia aroma, A. caven and A. atramentaria exhibited physical dormancy; the seed coat was very thick and compact, with a wide, sclerified parenchyma and a “water gap” for water uptake. Seed coat impermeability in these species was mainly attributed to characteristics of the lignified epidermis. By contrast, A. gilliesii and A. praecox did not have physical dormancy and showed thin seed coats with a much narrower sclerified parenchyma. Water entered the seeds of A. gilliesii and A. praecox not only through the hilar zone but also through the entire surface of the seed coat. Differences in the seed coat structure among species could be related to different regenerative responses to environmental conditions that would facilitate the coexistence of these Acacia species in the xerophytic forests of Córdoba, Argentina.

From seed production to seedling establishment: Important steps in an invasive process

It is widely accepted that exotic invasive species are one of the most important ecological and economic problems. Reproductive and establishment traits are considered key features of a population expansion process, but few works have studied many of these simultaneously. This work examines how large the differences are in reproductive and establishment traits between two Fabaceae, the exotic invasive, Gleditsia triacanthos and the native, Acacia aroma. Gleditsia is a serious leguminous woody invader in various parts of the world and Acacia is a common native tree of Argentina. Both species have similar dispersal mechanisms and their reproductive phenology overlaps. We chose 17 plants of each species in a continuous forest of the Chaco Serrano Forest of Córdoba, Argentina. In each plant we measured fruit production, fruit removal (exclusion experiments), seed predation (pre- and post-dispersal), seed germination, seed bank (on each focal tree, three sampling periods during the year), and density of seedlings (around focal individuals and randomly in the study site). Gleditsia presented some traits that could favour the invasion process, such as a higher number of seeds per plant, percentage of scarified seed germination and density of seedlings around the focal individuals, than Acacia. On the other hand, Gleditsia presented a higher percentage of seed predation. The seed bank was persistent in both species and no differences were observed in fruit removal. This work highlights the importance of simultaneously studying reproductive and establishment variables involved in the spreading of an exotic invasive species. It also gives important insight into the variables to be considered when planning management strategies. The results are discussed from the perspective of some remarkable hypotheses on invasive species and may contribute to rethinking some aspects of the theory on invasive species.

Antibacterial activity of extracts of Acacia aroma against methicillin-resistant and methicillin-sensitive Staphylococcus

Antibacterial activity of organic and aqueous extracts of Acacia aroma was evaluated against methicillin-resistant Staphylococcus aureus (MRSA), methicillin sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus epidermidis. Inhibition of bacterial growth was determined using agar diffusion and bioautographic methods. Among all assayed organic extracts only ethanolic and ethyl acetate extracts presented highest activities against all tested Staphylococcus strains with minimal inhibitory concentration (MIC) values ranging from 2.5 to 10 mg/ml and from 2.5 to 5 mg/ml respectively. The aqueous extracts show little antibacterial activity against Staphylococcus strains. The bioautography assay demonstrated well-defined growth inhibition zones against S. aureus in correspondence with flavonoids and saponins. A. aroma would be an interesting topic for further study and possibly for an alternative treatment for skin infections.

Argentinean native wood species: Physical and mechanical characterization of some Prosopis species and Acacia aroma (Leguminosae; Mimosoideae)

One of the problems in marketing the wood of Prosopis and Acacia is the lack of standardization of its qualities. The aim of this paper was to obtain a preliminary detection of some properties of the wood of four species of the genus Prosopis and one species from Acacia grown in Argentina. To accomplish this objective, the content of extractives and some physical and mechanical characteristics were analyzed. The density ρ 12 of all the species indicates that these woods range from heavy to very heavy (⩾0.69 g/cm 3). The total volumetric shrinkage values are low, less than 10%, for all species. The parallel compression strength and the shear strength for all the species indicate a very resistant wood (⩾46.93 MPa and ⩾18.35 MPa, respectively). Brinell hardness was higher than 5 kg/mm 2 in all cases. The species with less content of extractives is P. ruscifolia (approximately 9% of anhydrous mass) whereas A. aroma was the one with the greatest content (approximately 25% of anhydrous mass in the heartwood).

Suitability of the native woody species of the Chaco region, Argentina, for use in dendroecological studies of fire regimes

The Chaco region is one of the most extensive areas of dry forests and savannas in South America and fire plays a major role in its ecology. We studied the types of wounds caused by fire on the native woody species of Chaco and evaluated their suitability for fire dendroecological studies. The selected species were “quebracho colorado santiagueño” ( Schinopsis lorentzii (Griseb). Engl.), “quebracho blanco” ( Aspidosperma quebracho- blanco Schlecht), “algarrobo blanco” ( Prosopis alba Griseb), “algarrobo negro” ( Prosopis nigra (Griseb.) Hieron), “tusca” ( Acacia aroma Gill. Ex Hook. et Arn.) and “ garabato” ( Acacia furcatispina Burkart). Sampling sites were spread across different locations in the Province of Santiago del Estero, Argentina. A selection was made of individual trees with external signs of fire. Cross-sections of boles and branches were taken from each tree at heights of 0.3 and 1.3 m from the ground. The types of wounds were classified according to the percentage of damaged bole perimeter and the patterns of growth interruption. Species suitability for dendroecological studies was based on longevity, patterns of annual ring growth, type of wound, bark thickness and difficulty in dating the fire event. Two types of wound were studied: fire scars and fire marks. It was determined that S. lorentzii, A. quebracho- blanco, P. alba and P. nigra are the most suitable for dendroecological studies since their longevity and thicker bark development enable them to survive in moderate to high intensity fires. Prosopis and Acacia species have better tree ring demarcation and therefore provide more certainty in fire event dating. Despite the lower longevity and higher susceptibility to fire damage of the Acacia species, they are suitable for dendroecological studies that require analysis over a few decades in environments with lower intensity fire regimes. The distribution areas of the studied species means that they can be used for dendroecological studies of fire in the Western, Eastern and Mountain Chaco areas and the phytogeography provinces of Monte and Espinal.

Passage time, viability, and germination of seeds ingested by foxes

Seed passage through the gut of vertebrates is critical for endozoochorus seed dispersal because it may influence seed viability and germination capacity. Foxes are important fruit-eaters and presumed seed dispersers in the Chaco ecoregion. We experimentally assessed the seed passage time (SPT) and its effect on seed viability and germination in two fox species ( Pseudalopex gymnocercus and Cerdocyon thous) that occur in the Chaco. Passage time was measured using both artificial seeds of three sizes and wild seeds of four native fleshy-fruit species commonly consumed by foxes ( Ziziphus mistol, Acacia aroma, Celtis tala, and Syagrus romanzoffiana). The average SPT was 6.8 h for the Pampa fox and 7.7 h for the crab-eating fox. Passage time did not differ either among seeds of different sizes or between fox species. Passage through digestive tract of both fox species did not affect seed survival, whereas germination rate was slightly improved. Our data suggest that both fox species are legitimate seed dispersers of the four species studied, having a positive effect on both germination rate and dispersal distance from the parent plant.

Dormancy and germination in three Acacia (Fabaceae) species from central Argentina

We studied dormancy and germination requirements of seeds of Acacia aroma, A. caven and A. furcatispina from a semi-arid region of central Argentina. Imbibition experiments were performed to determine the rate of water uptake in seeds. To determine optimal temperature for germination, seeds were incubated at three temperature regimes (15/5, 25/15 and 35/20°C) with a 12/12 h daily photoperiod or in total darkness. Additionally, differences in dormancy and germination in seed colour morphs of A. aroma were studied. Seeds of A. aroma and A. caven had impermeable coats, while those of A. furcatispina did not. Seeds of the three species showed the same pattern of germination. Germination percentages were significantly lower at 15/5°C than at 25/15 or 35/20°C. The germination temperature pattern found for these species is probably related to the summer seasonal nature of rainfall in the study area. In A. aroma, seeds of the two colour morphs showed a similar pattern of dormancy and germination.

Antibacterial activity of ethanolic and aqueous extracts of Acacia aroma Gill. ex Hook et Arn

The purpose of the present study was to investigate the antibacterial activity of seven ethanolic extracts and three aqueous extracts from various parts (leaves, stems and flowers) of A. aroma against 163 strains of antibiotic multi-resistant bacteria. The disc diffusion assay was performed to evaluate antibacterial activity of the A. aroma crude extracts, against several Gram-positive bacteria ( E. faecalis, S. aureus, coagulase-negative stahylococci, S. pyogenes, S. agalactiae, S. aureus ATCC 29213, E. faecalis ATCC 29212) and Gram-negative bacteria ( E. coli., K. pneumoniae, P. mirabilis, E. cloacae, S. marcescens, M morganii, A. baumannii, P. aeruginosa, S. maltophilia, E. coli ATCC 35218, P. aeruginosa ATCC 27853, E. coli ATCC 25922). All ethanolic extracts showed activity against gram-positive bacteria. Among all obtained extracts, only leaf and flower fluid extracts showed activity against Gram-negative bacteria. Based on this bioassay, leaf fluid extracts tended to be the most potent, followed by flower fluid extracts. Minimal inhibitory concentration (MIC) values of extracts and antibiotics were comparatively determined by agar and broth dilution methods. Both extracts were active against S. aureus, coagulase-negative stahylococci, E. faecalis and E. faecium and all tested Gram-negative bacteria with MIC values from 0.067 to 0.308 mg/ml. In this study the minimal bactericidal concentration (MBC) values were identical or twice as high than the corresponding MIC for leaf extracts and four or eight times higher than MIC values for flower extracts. This may indicate a bactericidal effect. Stored extracts have similar antibacterial activity as recently obtained extracts. The A. aroma extracts of leaves and flowers may be useful as antibacterial agents against Gram- negative and Gram-positive antibiotic multi-resistant microorganisms.

Efectos de la Fragmentatión Sobre la Aborción y Depredación de Semillas en el Chaco Serrano

RESUMENLas interacciones entre plantas e insectos pueden ser afectadas por la fragmentacion de los hábitats. En este estudio, realizado en el Chaco Serrano de Argentina, investigamos los efectos de la fragmentación sobre la cantidad de semillas abortadas, depredadas y sanas de Acacia aroma y Cercidium praecox. Encontramos que los efectos de la fragmentaci6n fueron diferentes en cada especie. A medida que se redujo el área del fragmento, aumentó el número de semillas abortadas en A. aroma, mientras que la depredación pre‐dispersión disminuyó y la cantidad de semillas sanas aumento en C. praecox. El aumento de semillas abortadas en los fragmentos pequeños no produjo un número menor de semillas sanas disponibles para la dispersión. En las dos especies, los niveles máximos de depredacion por parte de brúquidos fueron cercanos al 35 por ciento, mientras que la aborción de semillas no superó el 7 por ciento. Debido a los altos niveles de daño y la especificidad de los brúquidos, los cambios producidos por la fragmentacióon pueden ser muy importantes para las poblaciones de estas dos especies. Los efectos de la fragmentación sobre la polinización y la depredación pre‐dispersión de semillas de estas fabáceas pueden generar una mayor disponibilidad de semillas para su posterior dispersión en ambientes fragmentados.ABSTRACTHabitat fragmentation can have consequences on plant reproduction through several interactions with insects. We studied the effects of habitat fragmentation in die proportion of aborted, predated and undamaged seeds of Acacia aroma and Cercidium praecox. We performed this study in the Chaco Serrano of Argentina. We found that fragmentation effects differed between species. In small patches, the number of aborted seeds of A. aroma increased and the number of pre–dispersal predated seeds and undamaged seeds of C. praecox decreased and increased, respectively. However, higher numbers of aborted seeds in small patches did not lead to fewer available seeds for dispersion. For these species, seed predation by bruchids was about 35 percent and aborted seeds were around 7 percent. Because of the elevated levels of damage and the high specificity of bruchids, the changes caused by habitat fragmentation may be very important for the populations of these two species. Habitat fragmentation effects on pollination and pre–dispersal seed predation of these legumes may determine higher availability of seeds for dispersion in fragmented habitats.

Mating system and population structure of Acacia aroma and A. macracantha (Fabaceae)

Acacia aroma and A. macracantha are closely related species that inhabit northern and central Argentina. The reproductive barriers between them seem to be weak. They exhibit low genetic differentiation, high levels of interspecific gene flow, and extensive areas of sympatry. Isoenzymatic approaches were used to evaluate the population structure and mating system parameters in natural Argentine populations of A. aroma and A. macracantha and to provide new tools for the analysis of relationships between these two species. All studied populations had high levels of genetic variability and no significant departures from Hardy-Weinberg expectations, but the two species did not differ from each other. Most variability occured within populations. Mating system analysis showed high levels of outcrossing, no biparental inbreeding, and a high probability that individuals within progeny arrays are full rather than half sibs. In all A. aroma and A. macracantha populations, polymorphic loci had the same allelic variants, and no geographic or genetic isolation between species was found. The results favor the hypothesis that these two entities represent a single polymorphic species rather than two distinct species.