Janzen-Connell effects shape gene flow patterns and realized fitness in the tropical dioecious tree Spondias purpurea (ANACARDIACEAE).

Pollination and seed dispersal patterns determine gene flow within plant populations. In tropical forests, a high proportion of trees are dioecious, insect pollinated and dispersed by vertebrates. Dispersal vectors and density dependent factors may modulate realized gene flow and influence the magnitude of Fine Scale Genetic Structure (FSGS), affecting individual fitness. Spondias purpurea is a vertebrate-dispersed, insect-pollinated dioecious tropical tree. We assessed the influence of sex ratio, effective and realized gene flow on genetic diversity, FSGS and individual fitness within a 30 ha plot in the tropical dry forest reserve of Chamela-Cuixmala, Mexico. All individuals within the plot were tagged, geo-referenced and sampled for genetic analysis. We measured dbh and monitored sex expression during two reproductive seasons for all individuals. We collected seeds directly from maternal trees for effective pollen dispersal analysis, and analyzed established seedlings to assess realized pollen and seed dispersal. Nine microsatellite loci were used to describe genetic diversity parameters, FSGS and gene flow patterns among different size classes. A total of 354 individuals were located and classified into three size classes based on their dbh (<10, 10-20, and >20 cm). Population sex ratios were male biased and diametric size distributions differed among sexes, these differences may be the result of precocious male reproduction at early stages. Autocorrelation analyses indicate low FSGS (Fj <0.07) across all size classes. Long realized pollen and seed dispersal and differences among effective and realized gene flow were detected. In our study site low FSGS is associated with high gene flow levels. Effective and realized gene flow indicate a population recruitment curve indicating Janzen-Connell effects and suggesting fitness advantages for long-distance pollen and seed dispersal events.

Chemical investigations of male and female leaf extracts from Schinus molle L.

The pepper-tree Schinus molle is an evergreen ornamental plant with various and diversified list of medical uses. In this article we analysed the chemical composition of male and female leaves of this plant during the off-flowering and flowering seasons. The leaf extracts were obtained by using a sequential extraction with solvents of different polarities and the chemical composition was investigated by GC-MS. The results showed a total of twenty-three components, in which elemol is the most abundant constituent followed by bicyclogermacrene, γ-eudesmol, α-eudesmol, ß-eudesmol and isocalamendiol. The petroleum ether and diethyl ether extracts from male and female flowering and off-flowering leaves consisted of sesquiterpene hydrocarbons as a major constituent followed by monoterpene hydrocarbons, while the acetone extracts showed a different composition. The obtained results show differences in the chemical composition between male and female and flowering and not flowering.

Spondias tuberosa Arruda (Anacardiaceae), a threatened tree of the Brazilian Caatinga? / Spondias tuberosa Arruda (Anacardiaceae), uma árvore ameaçada de extinção da Caatinga?

Abstract Spondias tuberosa Arr., a fructiferous tree endemic to the northeast Brazilian tropical dry forest called Caatinga, accounts for numerous benefits for its ecosystem as well as for the dwellers of the Caatinga. The tree serves as feed for pollinators and dispersers as well as fodder for domestic ruminants, and is a source of additional income for local smallholders and their families. Despite its vantages, it is facing several man-made and natural threats, and it is suspected that S. tuberosa could become extinct. Literature review suggests that S. tuberosa suffers a reduced regeneration leading to population decrease. At this juncture S. tuberosa cannot be considered threatened according to the International Union for Conservation of Nature Red List Categories and Criteria, as it has not yet been assessed and hampered generative regeneration is not considered in the IUCN assessment. The combination of threats, however, may have already caused an extinction debt for S. tuberosa. Due to the observed decline in tree density, a thorough assessment of the S. tuberosa population is recommended, as well as a threat assessment throughout the entire Caatinga.

Resumo Spondias tuberosa Arr., é uma árvore frutífera endêmica da Caatinga, floresta seca tropical localizada no Nordeste do Brasil. A árvore traz diversos benefícios para o ecossistema e para a população local. Ela serve de alimento tanto para polinizadores e dispersores quanto para ruminantes domésticos e é fonte de renda extra para os agricultores familiares da região. Apesar de seus benefícios, esta árvore enfrenta várias ameaças naturais e antrópicas que podem levar a sua extinção. A revisão da literatura científica sugere que S. tuberosa sofre de reduzida capacidade de regeneração, o que leva à diminuição da população. Todavia, S. tuberosa não é considerada uma espécie ameaçada de extinção de acordo com as categorias e critérios da Lista Vermelha da União Internacional para a Conservação da Natureza, já que a espécie ainda não foi avaliada e capacidade regenerativa reduzida não é considerado critério pelo UICN. A combinação de ameaças, entretanto, pode já ter levado ao débito de extinção da S. tuberosa. Devido ao declínio observado da densidade das árvores, recomenda-se uma avaliação completa da população de S. tuberosa e uma avaliação de todas as ameaças sofridas pela árvore na Caatinga.

Spondias tuberosa Arruda (Anacardiaceae), a threatened tree of the Brazilian Caatinga?

Spondias tuberosa Arr., a fructiferous tree endemic to the northeast Brazilian tropical dry forest called Caatinga, accounts for numerous benefits for its ecosystem as well as for the dwellers of the Caatinga. The tree serves as feed for pollinators and dispersers as well as fodder for domestic ruminants, and is a source of additional income for local smallholders and their families. Despite its vantages, it is facing several man-made and natural threats, and it is suspected that S. tuberosa could become extinct. Literature review suggests that S. tuberosa suffers a reduced regeneration leading to population decrease. At this juncture S. tuberosa cannot be considered threatened according to the International Union for Conservation of Nature Red List Categories and Criteria, as it has not yet been assessed and hampered generative regeneration is not considered in the IUCN assessment. The combination of threats, however, may have already caused an extinction debt for S. tuberosa. Due to the observed decline in tree density, a thorough assessment of the S. tuberosa population is recommended, as well as a threat assessment throughout the entire Caatinga.

Improved Predictions of the Geographic Distribution of Invasive Plants Using Climatic Niche Models.

Climatic niche models for invasive plants are usually constructed with occurrence records taken from literature and collections. Because these data neither discriminate among life-cycle stages of plants (adult or juvenile) nor the origin of individuals (naturally established or man-planted), the resulting models may mispredict the distribution ranges of these species. We propose that more accurate predictions could be obtained by modelling climatic niches with data of naturally established individuals, particularly with occurrence records of juvenile plants because this would restrict the predictions of models to those sites where climatic conditions allow the recruitment of the species. To test this proposal, we focused on the Peruvian peppertree (Schinus molle), a South American species that has largely invaded Mexico. Three climatic niche models were constructed for this species using high-resolution dataset gathered in the field. The first model included all occurrence records, irrespective of the life-cycle stage or origin of peppertrees (generalized niche model). The second model only included occurrence records of naturally established mature individuals (adult niche model), while the third model was constructed with occurrence records of naturally established juvenile plants (regeneration niche model). When models were compared, the generalized climatic niche model predicted the presence of peppertrees in sites located farther beyond the climatic thresholds that naturally established individuals can tolerate, suggesting that human activities influence the distribution of this invasive species. The adult and regeneration climatic niche models concurred in their predictions about the distribution of peppertrees, suggesting that naturally established adult trees only occur in sites where climatic conditions allow the recruitment of juvenile stages. These results support the proposal that climatic niches of invasive plants should be modelled with data of naturally established individuals because this improves the accuracy of predictions about their distribution ranges.

Climate change effects on the geographic distribution of specialist tree species of the Brazilian tropical dry forests.

The aim of this study was to evaluate the ecological niche models (ENMs) for three specialist trees (Anadenanthera colubrina, Aspidosperma pyrifolium and Myracrodruon urundeuva) in seasonally dry tropical forests (SDTFs) in Brazil, considering present and future pessimist scenarios (2080) of climate change. These three species exhibit typical deciduousness and are widely distributed by SDTF in South America, being important in studies of the historical and evolutionary processes experienced by this ecosystem. The modeling of the potential geographic distribution of species was done by the method of maximum entropy (Maxent).We verified a general expansion of suitable areas for occurrence of the three species in future (c.a., 18%), although there was reduction of areas with high environmental suitability in Caatinga region. Precipitation of wettest quarter and temperature seasonality were the predictor variables that most contributed to our models. Climatic changes can provide more severe and longer dry season with increasing temperature and tree mortality in tropics. On this scenario, areas currently occupied by rainforest and savannas could become more suitable for occurrence of the SDTF specialist trees, whereas regions occupied by Caatinga could not support the future level of unsustainable (e.g., aridity). Long-term multidisciplinary studies are necessary to make reliable predictions of the plant's adaptation strategies and responses to climate changes in dry forest at community level. Based on the high deforestation rate, endemism and threat, public policies to minimize the effects of climate change on the biodiversity found within SDTFs must be undertaken rapidly.

Climate change effects on the geographic distribution of specialist tree species of the Brazilian tropical dry forests / Efeitos das mudanças climáticas sobre a distribuição geográfica de espécies arbóreas especialistas de florestas secas tropicais brasileiras

AbstractThe aim of this study was to evaluate the ecological niche models (ENMs) for three specialist trees (Anadenantheracolubrina, Aspidosperma pyrifolium and Myracrodruon urundeuva) in seasonally dry tropical forests (SDTFs) in Brazil, considering present and future pessimist scenarios (2080) of climate change. These three species exhibit typical deciduousness and are widely distributed by SDTF in South America, being important in studies of the historical and evolutionary processes experienced by this ecosystem. The modeling of the potential geographic distribution of species was done by the method of maximum entropy (Maxent).We verified a general expansion of suitable areas for occurrence of the three species in future (c.a., 18%), although there was reduction of areas with high environmental suitability in Caatinga region. Precipitation of wettest quarter and temperature seasonality were the predictor variables that most contributed to our models. Climatic changes can provide more severe and longer dry season with increasing temperature and tree mortality in tropics. On this scenario, areas currently occupied by rainforest and savannas could become more suitable for occurrence of the SDTF specialist trees, whereas regions occupied by Caatinga could not support the future level of unsustainable (e.g., aridity). Long-term multidisciplinary studies are necessary to make reliable predictions of the plant’s adaptation strategies and responses to climate changes in dry forest at community level. Based on the high deforestation rate, endemism and threat, public policies to minimize the effects of climate change on the biodiversity found within SDTFs must be undertaken rapidly.

ResumoEste estudo tem como objetivo avaliar a modelagem de nicho ecológico (ENMs) para três espécies especialistas (Anadenantheracolubrina, Aspidosperma pyrifolium e Myracrodruon urundeuva) de florestas tropicais secas (FTSs) no Brasil, considerando o cenário de mudanças climáticas: presente e futuro pessimistas (2080). Estas três espécies são decíduas e amplamente distribuídas pelas FTSs na América do Sul, sendo importante em estudos sobre os processos históricos e evolutivos experimentados por este ecossistema. A modelagem da distribuição geográfica potencial das espécies foi construída através do método de máxima entropia (Maxent). Foi observada uma expansão geral de áreas adequadas para a ocorrência das três espécies no futuro (cerca de 18%), embora tenha existido uma redução das áreas com alta adequabilidade ambiental na região da Caatinga. A precipitação do trimestre mais úmido e a sazonalidade da temperatura foram os fatores que mais contribuíram para os nossos modelos. As mudanças climáticas podem gerar períodos secos mais severos e longos, com aumento da temperatura e mortalidade de árvores em regiões tropicais. Neste cenário, as áreas atualmente ocupadas por florestas úmidas e savanas poderiam tornar-se mais adequadas para a ocorrência das árvores especialistas em FTSs, enquanto que as regiões ocupadas por Caatinga não poderiam suportar o nível futuro da não adequabilidade (por exemplo, aridez). Estudos multidisciplinares de longa duração são necessários para fazer previsões confiáveis de estratégias adaptativas das plantas e respostas às variações climáticas em FTS em nível de comunidade. Com base na elevada taxa de desmatamento, endemismo e ameaça, políticas públicas para minimizar os efeitos das mudanças climáticas sobre a biodiversidade encontradas dentro FTSs devem ser realizadas rapidamente.

Molecular data and ecological niche modelling reveal the phylogeographic pattern of Cotinus coggygria (Anacardiaceae) in China's warm-temperate zone.

The phylogeography of common and widespread species helps to elucidate the history of local flora and vegetation. In this study, we selected Cotinus coggygria, a species widely distributed in China's warm-temperate zone. One chloroplast DNA (cpDNA) region and ecological niche modelling were used to examine the phylogeographic pattern of C. coggygria. The cpDNA data revealed two phylogeographic groups (Southern and Northern) corresponding to the geographic regions. Divergence time analyses revealed that divergence of the two groups occurred at approximately 147,000 years before the present (BP), which coincided with the formation of the downstream area of the Yellow River, indicating that the Yellow River was a weak phylogeographic divide for C. coggygria. The molecular data and ecological niche modelling also indicated that C. coggyria did not experience population expansion after glaciations. This study thus supports the fact that Pleistocene glacial cycles only slightly affected C. coggygria, which survived in situ and occupied multiple localised glacial refugia during glaciations. This finding is contrary to the hypothesis of large-scale range habitat contraction and retreat into a few main refugia.

An AFLP estimation of the outcrossing rate of Spondias tuberosa (Anacardiaceae), an endemic species to the Brazilian semiarid region.

The umbu tree (Spondias tuberosa) is one of the most important endemic species to the Brazilian tropical semiarid region. The umbu tree has edible fruits with a peculiar flavor that are consumed in natura or in a semi-industrialized form, such as jams, candies and juices. The majority of endemic species to Brazilian semiarid region have not been studied or sampled to form germ-plasm collections, which increases the risk of losing genetic variability of the adapted species to xerophytic conditions. The aim of this study was to estimate outcrossing rates in S. tuberosa using a multilocus mixed model in order to guide genetic resources and breeding programs of this species. DNA samples were extracted from 92 progenies of umbu trees, which were distributed among 12 families. These trees were planted by seed in 1991 in Petrolina, PE, Brazil. The experimental design was a randomized block, with a total of 42 progenies sampled in three regions. The experimental units were composed by five plants and five replications. The outcrossing rate was estimated by the multilocus model, which is available in the MLTR software, and was based on 17 polymorphic AFLP bands obtained from AAA_CTG and AAA_CTC primer combinations. The observed heterozygotes ranged from 0.147 to 0.499, with a maximum frequency estimated for the AAA_CTC 10 amplicon. The multilocus outcrossing estimation (t(m)) was 0.804 +/- 0.072, while the single-locus (t(s)) was 0.841 +/- 0.079, which suggests that S. tuberosa is predominantly an outcrossing species. The difference between t(m) and t(s) was -0.037 +/- 0.029, which indicates that biparental inbreeding was nearly absent. The mean inbreeding coefficient or fixation index (F) among maternal plants was--0.103 +/- 0.045, and the expected F was 0.108, which indicates that there was no excess of heterozygotes in the maternal population. The outcrossing estimates obtained in the present study indicate that S. tuberosa is an open-pollinated species. Biometrical models applied to this species should therefore take into account the deviation from random outcrossing to estimate genetic parameters and the constitution of broad germplasm samples to preserve the genetic variability of the species. Outcrossing rates based on AFLP and the mixed-mating model should be applied to other studies of plant species in the Brazilian semiarid region.

AFLP estimation of the outcrossing rate of Spondias tuberosa (Anacardiaceae), an endemic species to the Brazilian semiarid region / Una estimación AFLP de la tasa de fecundación cruzada de Spondias tuberosa (Anacardiaceae), una especie endémica de la región semiárida de Brasil

The umbu tree (Spondias tuberosa) is one of the most important endemic species to the Brazilian tropical semiarid region. The umbu tree has edible fruits with a peculiar flavor that are consumed in natura or in a semi-industrialized form, such as jams, candies and juices. The majority of endemic species to Brazilian semiarid region have not been studied or sampled to form germ- plasm collections, which increases the risk of losing genetic variability of the adapted species to xerophytic conditions. The aim of this study was to estimate outcrossing rates in S. tuberosa using a multilocus mixed model in order to guide genetic resources and breeding programs of this species. DNA samples were extracted from 92 progenies of umbu trees, which were distributed among 12 families. These trees were planted by seed in 1991 in Petrolina, PE, Brazil. The experimental design was a randomized block, with a total of 42 progenies sampled in three regions. The experimental units were composed by five plants and five replications. The out- crossing rate was estimated by the multilocus model, which is available in the MLTR software, and was based on 17 polymorphic AFLP bands obtained from AAA_CTG and AAA_CTC primer combinations. The observed heterozygotes ranged from 0.147 to 0.499, with a maximum frequency estimated for the AAA_CTC_10 ampli- con. The multilocus outcrossing estimation ( ) was 0.804±0.072, while the single-locus ( ) was 0.841±0.079, which suggests that S. tuberosa is predominantly an outcrossing species. The difference between and was -0.037±0.029, which indicates that biparental inbreeding was nearly absent. The mean inbreeding coefficient or fixation index ( ) among maternal plants was - 0.103±0.045, and the expected was 0.108, which indicates that there was no excess of heterozygotes in the maternal population. The outcrossing estimates obtained in the present study indicate that S. tuberosa is an open-pollinated species. Biometrical models applied to this species should therefore take into account the deviation from random outcrossing to estimate genetic parameters and the constitution of broad germplasm samples to preserve the genetic variability of the species. Outcrossing rates based on AFLP and the mixed-mating model should be applied to other studies of plant species in the Brazilian semiarid region.

El árbol de umbu (Spondias tuberosa) es una de las especies endémicas más importantes de la región semiárida del Brazil. El mismo tiene frutos comestibles con sabor distinto y puede ser consumido fresco o semiindustrializado, como mermeladas y zumos. La mayoría de las especies endémicas de la región semiárida del Brazil no fueron estudiadas o muestreadas para formar colecciones de germoplasma, aumentando el riesgo de pérdida de la variabilidad genética. El objetivo de este trabajo fue estimar las tasas de polinización cruzada en S. tuberosa basada en el modelo multi-locus mixto, con el fin de orientar los recursos genéticos y los programas de mejoramiento de esta especie. Muestras de ADN fueron extraídas de 92 progenies de árboles umbuzeiro, distribuidos en 12 familias, que se establecieron en Petrolina, PE, Brazil, 09º09’ S - 40º22’ W. El diseño experimental fue de bloques al azar con un total de 42 progenies muestreadas en tres regiones. La tasa de fecundación cruzada fue estimada por el modelo multi-locus disponible en el software MLTR, basado en 17 bandas de AFLP polimórficas obtenidas a partir de las combinaciones de cebadores AAA_CTG y AAA_CTC. Los heterocigotos observados oscilaron entre 0.147 y 0.499 con la frecuencia máxima estimada para AAA_CTC 10 amplicón. El valor estimado de cruzamiento multi-locus ( ) fue 0.804±0.072, mientras que el locus de uno-locus ( ) fue 0.841±0.079, lo que sugiere que S. tuberosa es predominantemente una especie de polinización cruzada. La diferencia entre el y fue de -0.037± 0,029, lo que indica que la endogamia bi-parental fue casi inexistente. La media del coeficiente de fijación ( ) entre las plantas maternas fue - 0.103±0.045, mientras que la esperada fue 0.108, lo que indica que no hubo un exceso de heterocigotos en la población materna. Las estimaciones obtenidas en este trabajo indican que S. tuberosa es una especie de polinización cruzada. Los modelos biométricos aplicados a esta especie deben tener en cuenta la desviación del cruce aleatorio para estimar los parámetros genéticos y la formación de grandes muestras para preservar la variabilidad genética de esta especie. La tasa de fecundación cruzada basada en AFLP y el apareamiento mezclado debe ser aplicado a otros estudios de especies de plantas de la región semiárida del Brazil.

Efeito fungitóxico do óleo essencial de aroeira da praia (Schinus terebinthifolius RADDI) sobre Colletotrichum gloeosporioides / Fungitoxic effect of essential oil from aroeira (Schinus terebinthifolius RADDI) on Colletotrichum gloeosporioides

Neste trabalho foi avaliado o efeito do óleo essencial do fruto de Schinus terebinthifolius sobre o crescimento micelial do fungo Colletotrichum gloeosporioides in vitro, e no desenvolvimento da antracnose no período de pós-colheita em mamões. As diferentes concentrações de óleo foram diluídas em Tween 80 a 8%. No experimento in vitro foram preparados meios de cultura BDA nas concentrações de 0,05; 0,10; 0,25 e 0,50% do óleo essencial. O controle negativo foi realizado apenas com meio BDA e o controle solvente com meio BDA e Tween 80 a 8%. A inibição do crescimento do fungo foi diretamente proporcional à quantidade do óleo e a maior inibição encontrada foi de 79,07% na concentração de óleo de 0,50%. No experimento in vivo os frutos do mamoeiro foram inoculados com o fungo em quatro tratamentos: com biofilme; com biofilme mais 0,50% do óleo; com fungicida Prochloraz e frutos controle. Embora o tratamento com óleo tenha sido eficiente contra o fungo, não foi indicado comercialmente, pois apresentou valores elevados de perda de massa fresca, de firmeza, e também sintomas de fitotoxidade. O óleo tem propriedade antifúngica contra C. gloeosporioides in vitro e in vivo, contudo, não é recomendado para o mamão em função da fitotoxidez.

This study evaluated the effect of essential oil from Schinus terebinthifolius fruit on the mycelial growth of the fungus Colletotrichum gloeosporioides in vitro and on the anthracnose development during the postharvest period of papaya fruits. The different oil concentrations were diluted in 8% Tween 80. For the in vitro experiment, PDA culture media were prepared at the concentrations of 0.05, 0.10, 0.25 and 0.50% essential oil. Negative control was prepared with PDA medium alone, while solvent control was prepared with PDA medium and 8% Tween 80. Fungal growth inhibition was directly proportional to the oil amount and the greatest inhibition was 79.07% at 0.50% oil concentration. For the in vivo experiment, papaya fruits were inoculated with the fungus in four treatments: with biofilm, with biofilm plus 0.50% oil, with the fungicide Prochloraz and control fruits. Although treatment with oil was efficient against the fungus, it was not commercially recommended since it presented high values of loss of fresh mass and firmness, as well as phytotoxicity symptoms. The oil has antifungal property against C. gloeosporioides both in vitro and in vivo; however, it is not recommended for papaya fruits due to its phytotoxicity.

Analysis of umbu (Spondias tuberosa Arruda (Anacardiaceae)) in different landscape management regimes: a process of incipient domestication?

Plant domestication is an evolutionary process guided by human groups who modify the landscape for their needs. The objective of this study was to evaluate the phenotypic variations between populations of Spondias tuberosa Arruda (umbuzeiro) when subjected to different local landscape management strategies. The influence of the landscape management system on these populations was evaluated in five identified regional units (mountains, base of mountains, pastures, cultivated areas and home gardens). Ten individuals were randomly selected from each region and subjected to morphological and chemical fruit analysis. The diversity index, based on Simpson's index, was determined for the different populations. We then evaluated the morphological differences between the individual fruits from the distinct landscape areas. We observed no significant differences in morphological diversity between the areas studied. Our data suggest that the umbuzeiro specimens in this region may be in the process of incipient domestication.

[Responses of Cotinus coggygria var. cinerea photosynthesis to soil drought stress].

By using a portable photosynthetic system (CIRAS-2), this paper studied the photosynthetic characters of 3-year-old Cotinus coggygria var. cinerea under effects of different soil water regime (enough supply, light stress, medium stress, and heavy stress) and light intensity. Soil water regime had significant effects on the photosynthetic parameters of C. coggygria. With increasing drought stress, the net photosynthetic rate, transpiration rate, and apparent yield all declined apparently, while the light compensation point increased. The highest water use efficiency was found under light water stress (soil relative water content being about 60% -65%). C. coggygria had higher net photosynthetic rate and higher water use efficiency under a wide range of high light intensity (photosynthetically active radiation being 1000-1800 micromol x m(-2) x s(-1)), but had lower efficiency of light absorbance and conversion, i.e., lower apparent quantum yield, under low light intensity, which was declined more significantly when the soil water stress was intensified.

Fire feedbacks facilitate invasion of pine savannas by Brazilian pepper (Schinus terebinthifolius).

* Fire disturbance can mediate the invasion of ecological communities by nonnative species. Nonnative plants that modify existing fire regimes may initiate a positive feedback that can facilitate their continued invasion. Fire-sensitive plants may successfully invade pyrogenic landscapes if they can inhibit fire in the landscape. * Here, we investigated whether the invasive shrub Brazilian pepper (Schinus terebinthifolius) can initiate a fire-suppression feedback in a fire-dependent pine savanna ecosystem in the southeastern USA. * We found that prescribed burns caused significant (30-45%) mortality of Brazilian pepper at low densities and that savannas with more frequent fires contained less Brazilian pepper. However, high densities of Brazilian pepper reduced fire temperature by up to 200 degrees C, and experienced as much as 80% lower mortality. * A cellular automaton model was used to demonstrate that frequent fire may control low-density populations, but that Brazilian pepper may reach a sufficient density during fire-free periods to initiate a positive feedback that reduces the frequency of fire and converts the savanna to an invasive-dominated forest.

[Pollen dispersion and reproductive success of four tree species of a xerophytic forest from Argentina]. / Dispersión polínica y éxito reproductive de cuatro especies arbóreas de un bosque xerófito de Argentina.

The "talares" in eastern Buenos Aires province, Argentina, are coastal xerophitic forests structured by few arboreal species surrounded by a lower and moister soil matrix. We studied the reproductive parameters of the most representative arboreal species (Celtis tala, Scutia buxifolia, Jodina rhombifolia, and Schinus longifolia). Pollen dispersion was studied through floral visitor traps (biotic dispersion) and using gravimetric pollen collectors (abiotic dispersion). The reproductive success (fruit formation rate) of the focal species was studied by enclosing flowers with different mesh bags. The reproductive system varied among the different species. C. tala was anemophilous and selfcompatible. S. buxifolia was entomophilous and floral visitors dependant. J. rhombifolia was entomophylous, although spontaneous autogamy could favor reproduction in the absence of pollinators. Lastly, S. longifolia could be an ambophilous species (pollinated by insects and by the wind). This dual system may be the result of system flexibility mechanism or an evolutionary transition.

Dispersión polínica y éxito reproductivo de cuatro especies arbóreas de un bosque xerófito de Argentina

Pollen dispersion and reproductive success of four tree species of a xerophytic forest from Argentina. The "talares" in eastern Buenos Aires province, Argentina, are coastal xerophitic forests structured by few arboreal species surrounded by a lower and moister soil matrix. We studied the reproductive parameters of the most representative arboreal species (Celtis tala, Scutia buxifolia, Jodina rhombifolia,and Schinus longifolia). Pollen dispersion was studied through floral visitor traps (biotic dispersion) and using gravimetric pollen collectors (abiotic dispersion). The reproductive success (fruit formation rate) of the focal species was studied by enclosing flowers with different mesh bags. The reproductive system varied among the different species. C. tala was anemophilous and selfcompatible. S. buxifolia was entomophilous and floral visitors dependant. J. rhombifolia was entomophylous, although spontaneous autogamy could favor reproduction in the absence of pollinators. Lastly, S. longifolia could be an ambophilous species (pollinated by insects and by the wind). This dual system may be the result of system flexibility mechanism or an evolutionary transition. Rev. Biol. Trop. 57 (1-2): 283-292. Epub 2009 June 30.

Los "talares" del E de la provincia de Buenos Aires son bosques xerófitos costeros estructurados por pocas especies arbóreas rodeados de una matriz de suelos más bajos y húmedos. Estudiamos los parámetros reproductivos de las especies arbóreas más representativas (Celtis tala, Scutia buxifolia, Jodina rhombifolia y Schinus longifolia). La dispersión polínica fue estudiada a través de trampas para visitantes florales (dispersión biótica) y utilizando recolectores gravimétricos de polen (dispersión abiótica). El éxito reproductivo (tasa de formación de frutos) de las especies focales fue estudiado a través de embolsado de flores con bolsas de distintos tipos de malla. El sistema reproductivo varió entre las especies. C. tala resultó anemófila y autocompatible, S. buxifolia fue entomófila y dependiente de los visitantes florales. J. rhombifolia fue una especie entomófila, aunque la autogamia espontánea podría favorecer al aseguramiento reproductivo en caso de falta de polinizadores. Finalmente, S. longifolia podría ser una especie ambófila (polinizada por insectos y por el viento). Este sistema dual podría ser el resultado de un mecanismo de flexibilidad del sistema de polinización o una transición evolutiva.

Functional differences within a guild of tropical mammalian frugivores.

Many plants interact with groups of mutualist pollinators and seed dispersers. A key issue for both basic ecology and conservation is whether the different species within these guilds of mutualist animals are functionally equivalent. Comparing the relative effects of sympatric mutualists is important for understanding the evolution of multispecies mutualisms and for predicting mutualism stability in the face of anthropogenic change. However, empirical comparisons of the population-level impacts of mutualist animals on their host plant are rare, particularly for seed dispersal mutualisms in species-rich ecosystems. We compared the influence of three seed-dispersing tropical mammals, lar gibbons (Hylobates lar), sambar deer (Rusa unicolor), and red muntjac deer (Muntiacus muntjak), on the demography of a shared host tree in Thailand, Choerospondias axillaris (Anacardiaceae). Sambar and muntjac dispersed far more C. axillaris seeds than did gibbons. While sambar deposited many seeds under female tree canopies, muntjac were the only disperser to move seeds to open microhabitats, where C. axillaris seed germination, seedling survival, and initial growth are enhanced. Using stage-based population models, we assessed how disperser-specific seed dispersal, variation in the frequency of canopy gap formation, and their interaction influenced the potential population growth of C. axillaris. Large differences in dispersal quantity and small differences in dispersal quality among sambar and gibbons resulted in similar and negligible impacts on the tree's population dynamics. Muntjac, by taking some of the seeds to open microhabitats, are projected to have a greater positive impact on C. axillaris demography than either sambar or gibbons. Model comparisons of population-level species impacts may allow us to predict which ecological interactions are at risk from loss of critical species.

Allelopathy at the land/sea interface: microalgae and Brazilian pepper.

Microalgae are significant contributors to biodiversity and primary production in shallow coastal habitats. The invasive Brazilian pepper (Schinusterebinthifolius) can occupy former mangrove habitats in disturbed areas, and its allelopathic capability can affect growth rates of microalgae. The four microalgae tested against dilution extracts of Schinus fruits varied in their growth response, suggesting variable but unpredictable impacts on microalgal biodiversity, primary production, and community structure.

Temperature-dependent development and potential distribution of Episimus utilis (Lepidoptera: Tortricidae), a candidate biological control agent of Brazilian peppertree (Sapindales: Anacardiaceae) in Florida.

The invasive Brazilian peppertree (Schinus terebinthifolius Raddi), native to South America, is widely established throughout central and south Florida. The defoliating leaflet-roller Episimus utilis Zimmerman was selected as potential biocontrol agent of this invasive species. The objectives of this study were to determine development rate and survival of E. utilis at seven constant temperatures (10, 15, 20, 25, 30, 33, and 35 degrees C) and generate prediction maps of the number of generations per year this species may exhibit in the United States. The rate of development of E. utilis as a function of temperature was modeled using linear regression to estimate a lower developmental threshold of 9.6 degrees C and the degree-day requirement of 588. The Logan nonlinear regression model was used to estimate an upper developmental threshold of 33 degrees C. Cold tolerance of E. utilis was examined using all insect stages, and each stage was exposed to three constant temperatures (10, 5, 0 degrees C) for 0.5, 1, 2, 4, and 8 d (or until all insects died). The pupal stage was the most cold tolerant with 100% mortality after 12 d at 0 degrees C. The pupal lethal times at 5 (Ltime50 = 10 d, Ltime90 = 28 d) and 0 degrees C (Ltime50 = 5 d, Ltime90 = 9 d) were used to generate isothermal lines to predict favorable regions for E. utilis establishment. A GIS map was generated to predict the number of generations of E. utilis (range, 0.5-9.8) across all Brazilian peppertree range in the United States. The potential for establishment of E. utilis and its probable distribution in the continental United States was examined.

Fitness consequences of host use in the field: temporal variation in performance and a life history tradeoff in the moth Rothschildia lebeau (Saturniidae).

That fitness varies as a function of using different hosts is a basic premise of theory addressing the ecology and evolution of oviposition behavior and host selection. Few data exist demonstrating: (1) the effects of different hosts on fitness in the field, and (2) how these effects vary spatially or temporally. Cohorts of caterpillars were followed from hatching to adulthood to test the hypotheses that: (1) hosts have significant effects on herbivore performance in nature, and (2) host "quality" for performance varies predictably (i.e., the rank order is consistent) across herbivore generations. In total, the fates of >2,000 caterpillars were followed on 238 individual host trees. Host species had significant effects on most, but not all, measured components of caterpillar performance in the field. Variation among generations was mainly quantitative rather than qualitative, with few changes in the rank order of hosts in their effects on performance. There was also a strong seasonal effect on performance such that caterpillar growth and survival were higher in the early wet season compared to the late wet season. Using estimates derived from these data, correlations among larval growth rate, larval survival, total development time, and final adult size were examined at the level of host plant species. Across generations, larval survival was consistently poor, development time was long, but final adult size attained was large on the host Spondias mombin. The converse was true for the host Exostema mexicanum. Relative performance on the host Casearia nitida was variable between the other two hosts. Overall, the data suggest that host use involves a predictable tradeoff between larval survival and final adult size, but argue that which is the "better" host from the female perspective will depend on the fitness consequences of producing a few, relatively large offspring versus producing more, relatively small offspring.