ABSTRACT Studies about seed dispersal and germination are important to understand patterns of plant distribution and abundance, and help establish strategies for environmental conservation. We evaluated the role of two different dispersers, the ant Atta laevigata and the maned wolf Chrysocyon brachyurus, in the germination of Copaifera arenicola seeds, a characteristically myrmecochorous plant species. Germination was evaluated for seeds subjected to four treatments: (1) seeds manipulated by the ant, (2) seeds ingested by the maned wolf, (3) seeds that had the elaiosome removed manually, and (4) seeds with elaiosome (unmanipulated seeds). Seeds manipulated by the ant and seeds that had the elaiosome removed manually required less time to germinate and had higher germination percentages (98.6% and 95.8%, respectively) than the other treatments. However, seeds ingested by the maned wolf also had a high germination percentage (87.7%), above that of unmanipulated seeds (34.7%). Probably, elaiosomes of unmanipulated seeds and small remnants of this structure that resist digestion by maned wolf can decrease to some extent seed germination. We argue that dispersal of C. arenicola seeds by the ant and by the maned wolf result in different patterns of seed distribution in the environment and that they have complementary roles in structuring plant populations.

Resumen Las hormigas son sensibles a cambios ambientales y la estructura de la comunidad puede ser moldeada por la heterogeneidad ambiental y las interacciones interespecíficas. Probamos 2 hipótesis: (1) la estructura de la vegetación afecta negativamente la diversidad de hormigas en hábitats simplificados y (2) las interacciones interespecíficas dan forma a las comunidades de hormigas. Colectamos hormigas en arbustos de 16 unidades de muestreo de 100 m2 utilizando paraguas entomológicos y bateo en un área en regeneración de Cerrado, Brasil. La riqueza, abundancia y altura promedio de plantas se utilizaron como medida de heterogeneidad ambiental. Muestreamos 457 hormigas de 17 especies. Observamos una mayor riqueza de especies en parcelas con mayor abundancia de plantas y menor altura, y una relación negativa entre la abundancia y la altura de plantas. Corroboramos que la estructura de la vegetación afecta negativamente la diversidad de hormigas en hábitats simplificados. Los valores observados del índice de coexistencia difirieron de lo esperado en matrices simuladas, sugiriendo que la competencia moldea la comunidad de hormigas en hábitats simplificados. Destacamos la importancia de conservar árboles pequeños en hábitats menos complejos, porque representan elementos clave que albergan una gran diversidad.

Abstract Ant species are highly sensitive to environmental changes, and ant community structure can be shaped by environmental heterogeneity and interspecific interactions. We tested 2 hypotheses: (1) vegetation structure negatively affecting ant diversity in simplified habitats and (2) interspecific interactions shaping ant communities. We collected ants on shrubs distributed in 16 sampling units of 100 m2 using the entomological umbrella and beating technique in a regenerating Cerrado area of Brazil. The richness, abundance and average height of the plants were used as a measure of environmental heterogeneity. A total of 457 ants belonging to 17 species were sampled. We observed higher ant species richness in plots with greater plant abundance and lower plant height. We observed a negative relationship between ant abundance and plant height per plot. These results corroborate that vegetation structure negatively affects ant diversity in simplified habitats. The observed values of co-occurrence index differed from the expected values of simulated matrices, suggesting that competition shaping ant community in simplified habitats. We highlight the importance of conserving small trees, especially in structurally less complex habitats, because they represent key elements that harbor high ant species diversity.

Abstract Background and Aims: Environmental factors can interact with plant life history to determinate the reproductive strategies of adult plants and seedling recruitment. We expect that widely distributed tree species produce heavier seed and with greater variation in seed size than shrubs of restricted geographic distribution. We also predict that widely distributed tree species should be capable to germinate and develop under variable range of light conditions, while sun-adapted shrubs should germinate and develop better under high light intensity. We used as models two congeneric species of Fabaceae. Copaifera langsdorffii is a widely distributed arboreal species and C oblongifolia is a shrub with restricted distribution. Methods: Seeds were collected from two plant species in a Cerrado vegetation area, northern Minas Gerais, Brazil. The effects of light available on seed germination and seedling development was conducted in a germination chamber with controlled photoperiod, temperature and light intensity. Key results: The widely distributed tree (C. langsdorffii) had greater seed mass than the shrub (C. oblongifolia). Seeds of C. langsdorffii germinated faster under available high light, while the shrub C. oblongifolia seeds required less time to germinate under available low light and darkness. Under high light intensity, germination percentage of C. langsdorffii and C. oblongifolia seeds did not vary. However, seeds of the shrub showed a higher germination percentage under low light intensity and darkness. In general, seed mass showed a negative relationship with germination percentage, but this relationship varied in function of species and the availability of light. Copaifera langsdorffii seedlings had larger shoots and roots than C. oblongifolia. In contrast, the root:shoot ratio was higher in shrub than in tree species. Conclusions: Our results have important implications for understanding the patterns of distribution of two Copaifera species and explain the ability of C. oblongifolia to colonize disturbed areas.

Resumen Antecedentes y Objetivos: Los factores ambientales pueden interactuar con la historia de vida de las plantas determinando las estrategias reproductivas de individuos adultos y el reclutamiento de plántulas. Predecimos que las especies de árboles ampliamente distribuidas producen semillas más pesadas y con una mayor variación en el tamaño de las semillas que los arbustos de distribución geográfica restringida. Esperamos que las especies arbóreas ampliamente distribuidas deberían ser capaces de germinar y desarrollarse bajo un rango variable de condiciones de luz, mientras que los arbustos adaptados a condiciones de sol deberían germinar y desarrollarse mejor con una alta intensidad de luz. Usamos como modelo dos especies congenéricas de Fabaceae. Copaifera langsdorffii es una especie arbórea ampliamente distribuida y C. oblongifolia es un arbusto de distribución geográfica restringida. Métodos: Se colectaron semillas de estas especies de plantas en un área de vegetación de Cerrado, al norte del estado de Minas Gerais, Brasil. Los efectos de la disponibilidad de luz sobre la germinación de semillas y el desarrollo de plántulas se realizaron en una cámara de germinación con fotoperíodo controlado, temperatura e intensidad de luz. Resultados clave: El árbol de amplia distribución (C. langsdorffii) tuvo mayor masa de semillas que el arbusto (C. oblongifolia). Las semillas de C. langsdorffii germinaron más rápido bajo alta disponibilidad de luz, mientras que las semillas de C. oblongifolia requirieron menos tiempo para germinar bajo poca luz disponible y oscuridad. En alta intensidad de luz, las semillas de C. langsdorffii y de C. oblongifolia tuvieron similares porcentajes, mientras que las semillas de C. oblongifolia mostraron una mayor germinación en baja intensidad de luz y oscuridad. La masa de semillas mostró una relación negativa con el porcentaje de germinación, pero esta relación varió en función de las especies y de la disponibilidad de luz. Las plántulas de C. langsdorffii tuvieron mayor desarrollo de brotes y raíces que C. oblongifolia. En contraste, la relación raíz:brote fue mayor en arbustos que en árboles. Conclusiones: Nuestros resultados tienen implicaciones importantes para comprender los patrones de distribución de dos especies de Copaifera y poder explicar la capacidad de C. oblongifolia para colonizar áreas perturbadas.

Os insetos galhadores são herbívoros sedentários sofisticados que apresentam alto nível de especialização com sua planta hospedeira, mas sua performance pode ser afetada por fatores bióticos e abióticos. Neste estudo nós testamos duas hipóteses: a) plantas que possuem maior número de vizinhos coespecíficos apresentam maior riqueza e abundância de insetos galhadores, e b) a competição interespecífica é uma força capaz de molda a organização das comunidades de insetos herbívoros associados com uma planta super-hospedeira. O sistema Copaifera oblongifolia (Fabaceae)/ insetos galhadores associados foi usado para testar estas hipóteses. Os trabalhos de campo foram desenvolvidos em áreas de Cerrado do norte de Minas Gerais, Brasil. Para testar a primeira hipótese, nós avaliamos, com modelos lineares generalizados de efeitos mistos, os efeitos do número de vizinhos coespecíficos na riqueza e abundância de galhas associadas com 67 arbustos de C. oblongifolia pertencentes a duas populações. Para testar a segunda hipótese, nós usamos modelos nulos para avaliar se um arbusto de C. oblongifolia colonizado por uma espécie de inseto galhador é preferido ou evitado por uma outra espécie de inseto galhador. Um total de 2901 insetos galhadores pertencentes a 15 diferentes espécies foi coletado nos 67 arbustos de C. oblongifolia. Nós observamos uma relação negativa entre o número de vizinhos coespecíficos e a riqueza e a abundância de insetos galhadores associados com C. oblongifolia. Assim, nossos resultados não corroboraram a hipótese da concentração do recuro e nós usamos a teoria da diluição do recurso para explicar este resultado. Nossos resultados também mostraram que o padrão de co-ocorrência dos insetos galhadores na planta hospedeira não diferiu daquele esperado pelo acaso. Portanto, a estrutura da comunidade de insetos galhadores associada com C. oblongifolia não pode ser atribuída a eventos determinísticos com a competição interespecífica.

Gall-forming insects are sophisticated sedentary herbivores that present high level of specificity with host plant, but their performance can be affected by biotic and abiotic factors. In this study we have tested two predictions: a) plants that have a greater number of conspecific neighbors have greater richness and abundance of gall-forming insects, and b) interspecific competition is a force capable of shaping the organization of gall-forming insect communities in super-host plants. We used the Copaifera oblongifolia (Fabaceae)/galling insects' system to test these predictions. Fieldwork was carried out in areas of Cerrado (Brazilian Savanna) in northern Minas Gerais, Brazil. To test the first hypothesis, we evaluated with generalized linear mixed models, the effects of the number of conspecific neighbors on the richness and abundance of galls associated with 67 C. oblongifolia individual plants belonging to two populations. To test the second hypothesis, we used null models to evaluate whether a plant of C. oblongifolia colonized by a species of gall is preferred or avoided by another species of gall. A total of 2901 gall-forming insects belonging to 15 species were collected from the host plant C. oblongifolia. We observed negative relationships between the number of conspecific neighbors and the abundance and richness of gall-forming insects associated C. oblongifolia. Thus, our data did not support the resource concentration hypothesis. Instead, we used the resource dilution theory to explain the negative relation between resource concentration and frequency of attack by galling insects. Our results also showed that the co-occurrence pattern of gall-forming insects in the host plant did not differ from those expected by chance. Therefore, the structure of the gall-forming insect community associated to single C. oblongifolia plants cannot be attributed to deterministic factors such as interspecific competition.

ABSTRACT Copaifera oblongifolia is a recurrent plant species in degraded areas yet there is little information about its seed biology and interactions with fungi. The aims of this study were to identify the fungal community (endophytic and non-endophytic) associated with C. oblongifolia seeds and to test the effects of these different fungal species on germination. In general, germination of C. oblongifolia seeds was high (about 85 %), initiating four days after sowing and continuing for a total of 20 days. External asepsis with sodium hypochlorite did not influence germinability of C. oblongifolia. Seed infestation with Aspergillus niger, A. flavus, Mucor sp. and Rhizopus stolonifer did not affect the time required for germination, however, infection with A. flavus negatively affected germination percentage. Endophytic fungi were not isolated from C. oblongifolia seeds, suggesting that this species does not transmit endophytic fungi vertically. Therefore, C. oblongifolia can be classified in Class 3 with regard to the transmission and presence of endophytes.

ABSTRACT Seed germination and seedling performance are affected by environmental factors and seed traits. In this study we investigated the effects of seed size and light intensity on germinability and seedling development of Copaifera oblongifolia. A total of 225 seeds were individually weighed and sown in three germination trays composed of 75 cells each. Each tray was placed in a different germination chamber with controlled photoperiod, temperature and light intensity. Seed size showed a positive relationship with time required for seed germination, and seeds exposed to high light intensity required more time to germinate. Seed size did not affect germination percentage, but seeds sown under high light intensity had a lower germination percentage than seeds sown under low light intensity and darkness. Seedling shoot mass showed a positive relationship with seeds mass, and seedlings grown in high light intensity had greater shoot mass than seedling growth in low light intensity and darkness. Thus, seed germinability of C. oblongifolia was higher in darkness while seedlings exhibited greater development under light. Looking to explain the ability of C. oblongifolia to colonize open/disturbed sites, it seems possible that plowing soil can bury seeds, thereby stimulating the germination of seeds present in the seed bank.

ABSTRACT The timing of phenological events varies within and among populations, affecting the performance of individual plants differently. We evaluated the effects of relative variation in sprouting time on the display of reproductive events, vegetative growth and herbivory in Copaifera langsdorffii (Fabaceae). A total of 93 trees of C. langsdorffii was monitored daily to determine their sprouting time. We collected ten terminal branches of each plant to evaluate vegetative growth, production of defense compounds and insect herbivore damage. The sprouting time for the studied population lasted 67 days. Variation in sprouting time did not affect the probability of plants to enter the reproductive stage. Plants that entered the reproductive stage showed greater vegetative biomass. Variation in sprouting time had a negative relationship with branch growth and a positive relationship with the number of leaflets. Leaf phenol concentration did not vary in relation to sprouting time or plant phenology, but herbivory was higher in plants that sprouted later. The relationships among plant sprouting time, vegetative development and display of reproductive stage in C. langsdorffii are discussed. The results of this study also suggest that early sprouting prior to the rainy season is a strategy used by C. langsdorffii to escape herbivores attacks.

ResumenLas plantas tienen recursos limitados para invertir en reproducción, crecimiento vegetativo y defensa contra herbívoros. El cambio en la distribución de recursos promueve variaciones en rasgos vegetales, que pueden afectar los niveles tróficos superiores. Durante dos años consecutivos de alta y baja inversión reproductiva se evaluó el cambio de recursos entre crecimiento vegetativo y defensa, y su efecto indirecto sobre la herbivoría en Copaifera langsdorffii. Nos preguntamos: i) ¿La inversión de recursos para la reproducción causa reducción del crecimiento vegetativo, como predice la hipótesis de equilibrio carbono/nutrientes, haciendo posible gastar más recursos en defensa? ii) ¿La variación en distribución de recursos para crecimiento y defensa entre años de alta y baja fructificación modifica indirectamente la herbivoría? Se monitorearon treinta y cinco árboles durante 2008 (gran fructificación) y 2009 (sin fructificación) en un área de vegetación de cerrado (Brasil), para evaluar la inversión diferencial en rasgos vegetativos (biomasa, crecimiento y No. de ramificaciones), defensa (concentración de taninos e hipersensibilidad vegetal) y herbivoría. De acuerdo a nuestra primera pregunta, se observó que en el año de fructificación la biomasa leñosa afectó negativamente la concentración de taninos, indicando que la producción de frutos redujo los recursos que podían invertirse en crecimiento y defensa. Además, la resistencia de las plantas y el ataque de agallas fueron influidos positivamente por la concentración de taninos y la biomasa foliar, lo que sugiere que la resistencia de los árboles a la herbivoría es un buen indicador de defensa vegetal y una estrategia efectiva de defensa de C. langsdorffii, además hay evidencia de respuesta trófica indirecta, como se postula en la segunda pregunta. En resumen, el patrón de fructificación supra-anual provoca varios efectos en el desarrollo de las plantas, mostrando la importancia de evaluar diversos rasgos vegetales al caracterizar la inversión de recursos de una especie. Como se esperaba, el cambio en la distribución de recursos modifica la producción de compuestos de defensa y los patrones de herbivoría. El entendimiento de este elemento importante de las interacciones insecto-planta será fundamental para descifrar la historia natural coevolutiva y las interacciones entre reproducción vegetal y ataque herbívoro. Además de eso, solo a través de estudios a largo plazo vamos a ser capaces de construir modelos y desarrollar pronósticos más precisos acerca de los factores que desencadenan el efecto de abajo hacia arriba en el rendimiento de la herbivoría, así el efecto de arriba hacia abajo de los herbívoros sobre la evolución de las plantas.

AbstractPlants have limited resources to invest in reproduction, vegetative growth and defense against herbivorous. Trade-off in resources allocation promotes changes in plant traits that may affect higher trophic levels. In this study, we evaluated the trade-off effect between years of high and low fruiting on the investment of resources for growth and defense, and their indirect effects on herbivory in Copaifera langsdorffii. Our questions were: (i) does the resource investment on reproduction causes a depletion in vegetative growth as predicted by the Carbon/Nutrient Balance hypothesis (CNBH), resulting in more availability of resources to be allocated for defense?, (ii) does the variation in resource allocation for growth and defense between years of high and low fruiting leads to indirect changes in herbivory? Thirty-five trees located in a Cerrado area were monitored during 2008 (year of high fruiting) and 2009 (year of no fruiting) to evaluate the differential investment in vegetative traits (biomass, growth and number of ramifications), plant defense (tannin concentration and plant hypersensitivity) and herbivory (galling attack and folivory). According to our first question, we observed that in the fruiting year, woody biomass negatively affected tannin concentration, indicating that fruit production restricted the resources that could be invested both in growth as in defense. In the same way, we observed an inter-annual variation in herbivorous attack, and found that plants with higher leaf biomass and tannin concentration, experienced higher galling attack and hypersensitive reaction, regardless years. These findings suggested that plants’ resistance to herbivory is a good proxy of plant defense and an effective defense strategy for C. langsdorffii, besides the evidence of indirect responses of the third trophic level, as postulated by the second question. In summary, the supra-annual fruiting pattern promoted several changes on plant development, demonstrating the importance of evaluating different plant traits when characterizing the vegetative investment. As expected by theory, the trade-off in resource allocation favored changes in defense compounds production and patterns of herbivory. The understanding of this important element of insect-plant interactions will be fundamental to decipher coevolutionary life histories and interactions between plant species reproduction and herbivory. Besides that, only through long-term studies we will be able to build models and develop more accurate forecasts about the factors that trigger the bottom-up effect on herbivory performance, as well the top-down effect of herbivores on plant trait evolution. Rev. Biol. Trop. 64 (2): 507-520. Epub 2016 June 01.

Abstract Dengue is a major worldwide public health problem, especially in the tropical and subtropical regions of the world. Primary infection with a single Dengue virus serotype causes a mild, self-limiting febrile illness called dengue fever. However, a subset of patients who experience secondary infection with a different serotype can progress to a more severe form of the disease, called dengue hemorrhagic fever. The four Dengue virus serotypes (1–4) are antigenically and genetically distinct and each serotype is composed of multiple genotypes. In this study we isolated one Dengue virus 1 serotype, named BR/Alfenas/2012, from a patient with dengue hemorrhagic fever in Alfenas, South Minas Gerais, Brazil and molecular identification was performed based on the analysis of NS5 gene. Swiss mice were infected with this isolate to verify its potential to induce histopathological alterations characteristic of dengue. Liver histopathological analysis of infected animals showed the presence of inflammatory infiltrates, hepatic steatosis, as well as edema, hemorrhage and necrosis focal points. Phylogenetic and evolutionary analyses based on the envelope gene provided evidence that the isolate BR/Alfenas/2012 belongs to genotype V, lineage I and it is probably derived from isolates of Rio de Janeiro, Brazil. The isolate BR/Alfenas/2012 showed two unique amino acids substitutions (SER222THRE and PHE306SER) when compared to other Brazilian isolates from the same genotype/lineage. Molecular models were generated for the envelope protein indicating that the amino acid alteration PHE 306 SER could contribute to a different folding in this region located within the domain III. Further genetic and animal model studies using BR/Alfenas/2012 and other isolates belonging to the same lineage/genotype could help determine the relation of these genetic alterations and dengue hemorrhagic fever in a susceptible population.

Resumen:El compromiso o balance adaptativo de las semillas en tamaño/ número (trade-off seed size/number) es un reconocido fenómeno capaz de dar forma a los procesos ecológicos de la colonización y el establecimiento de especies de plantas. Los estudios que describen el compromiso adaptativo de las semillas en tamaño/número en especies con fructificación supra-anual siguen siendo raros. En este estudio, se probaron dos hipótesis predictivas para compromiso adap-tativo de las semillas en tamaño/número: (i) una a escala poblacional, semillas producidas durante el año de mayor inversión reproductiva mostraran un tamaño reducido, y (ii) otra a escala individual que se dará una relación inversa entre el tamaño y número de semillas producidas por la planta individual. Para probar estas predicciones, 102 plantas adultas de Copaifera langsdorffii fueron monitoreadas mensualmente entre enero y septiembre, durante cuatro años consecutivos (2008-2011) con el fin de estudiar la inversión reproductiva de las plantas. Plantas langsdorffii C. exhibieron actividad reproductiva sólo durante el 2008 y 2011. El número promedio de semillas por rama fue 26.4 % mayor en 2008 en comparación con 2011. También se observó que el tamaño de la semilla fue mayor en 2008, cuando las plantas producen mayor número de frutos. Por lo tanto, los datos no apoyan la primera hipótesis de predicción de tamaño/número. En ambos años reproductivos, existía una relación negativa entre el tamaño de la semilla y el número de semillas, comprobando la segunda hipótesis de predicción del tamaño/número de semillas. El periodo de interacción con el año reproductivo sugiere que el compromiso adaptativo de las semillas en tamaño/número fue de hecho más fuerte en 2011, cuando las plantas produjeron baja cantidad de semillas. Por último, este estudio llama la atención por el patrón de fructificación supra-anual en C. langsdoffii, y sugiere que los patrones fenológicos contribuyen a explicar la amplia variación en el tamaño de la semilla y la distribución geográfica.

Abstract:The trade-off seed size/number is a recognized phenomenon capable of shaping ecological processes of colonization and establishment of plant species. Studies that describe trade-offs size/number of seeds in supra-annual fruiting species are still rare. In this study, two predictions for trade-off size/number hypothesis were tested: (i) on a population scale, seeds produced during years of greater reproductive investment showed reduced size, and (ii) on individual scale there is an inverse relationship between size and number of seeds produced by individual plant. To test these predictions, 102 Copaifera langsdorffii adult plants were monitored monthly from January to September during four consecutive years (2008 to 2011) in order to study the reproductive investment of plants. C. langsdorffii plants exhibited reproductive activity only during years 2008 and 2011. The mean number of seeds per branch was 26.4 % greater in 2008 comparatively to 2011. It was also observed that seed size was greater in the year of 2008, when plants produced greater number of fruits. Thus, the data did not support the first prediction of seed size/number hypothesis. In both reproductive years, there was a negative relationship between seed size and number of seeds, supporting the second prediction of the seed size/number hypothesis. The interaction term with the reproductive year suggests that the trade-off size/number of seeds was indeed stronger in 2011, when the plants produced lower seed number. Finally, this study calls the attention to supra-annual fruiting pattern in C. langsdoffii, and suggests that the phenological patterns contribute to explain the wide variation in their seed size and geographical distribution.

The plant population dynamic is affected by ecological and evolutionary processes that operate at all stages of the plant life cycle. The aim of this study was to characterize the seed and seedling performance of Copaifera langsdorffii by testing four hypotheses: the resource concentration hypothesis; the relationship between seed size and germinability hypothesis; the relationship between seed size and seedling vigor hypothesis; and the intraspecific seedling competition hypothesis. All seeds used in the experiments were collected from 35 C. langsdorffii plants located in a fragment of the Brazilian cerrado (savanna). The number of fruits per plant negatively affected Rhinochenus brevicollis attacks on C. langsdorffii seeds. Therefore, this result does not support the resource concentration hypothesis, and predator satiation was used in order to explain the observed result. In general, seed germinability (percentage and time to emergence) was not influenced by seed size. The homogeneity of the experimental design, together with an abundant water supply, may have masked the effects of seed size on germinability. Seed size positively affected seedling development, corroborating the expected relationship between seed size and seedling vigor. The number of seedling per plastic bags negatively affected the growth of C. langsdorffii. The nutrient-limited soil probably promoted the below-ground competition for nutrients among seedlings. Finally, the role of evolutionary and ecological factors on C. langsdorffii population dynamics is discussed.

Predação de Sementes de Copaifera langsdorffi Desf. (Fabaceae: Caesalpinioideae) por Rhinochenus brevicollis Chevrolat (Coleoptera: Curculionidae) em uma Área de Cerrado do Brasil: Insetos predadores de sementes geralmente são herbívoros especializados que podem ser afetados por características da planta hospedeira. Neste estudo, a predação das sementes de Copaifera langsdorffi por Rhynochenus brevicollis foi caracterizada testando-se as hipóteses da concentração do recurso e da arquitetura da planta. O estudo foi realizado em um fragmento de cerrado localizado no norte do estado de Minas Gerais, Brasil. A percentagem de sementes de C. langsdorffi predadas por R. brevicollis variou de 1 to 30% (média±DP, 9.31±6.41). O número de frutos por ramos afetou negativamente a percentagem de predação das sementes por R. brevicollis.A predação de sementes pelo besouro mostrou relação positiva com a circunferência do tronco das árvores, mas a altura das árvores não afetou o ataque do predador. Assim, nossos dados não apresentaram suporte real para as duas hipóteses testadas. Finalmente, o estudo discute o papel da frutifcação supra-anual na regulação da população de R. brevicollis.

Seed predator insects are generally highly specialized herbivores that can be affected by several plant characteristics. In this study, the resource concentration hypothesis and the plant architecture hypothesis were tested by evaluating the attack of Rhynochenus brevicollis on Copaifera langsdorffi seeds. The study was conducted in a cerrado fragment situated in southeastern Brazil. The percentage of C. langsdorffi seed predation by R. brevicollis ranged from 1 to 30% (mean±SD, 9.31±6.41). The percentage of seed predation was negatively related to the number of fruits per branch. The predation of seeds by the beetle was positively affected by plant crown circumference, while plant height did not show any relationship with seed predation. Thus, our results did not support any of the two hypotheses evaluated. Finally, the study discusses the role of plant phenology (masting) in regulating the seed predator's population in cerrado vegetation.

La simplificación de los hábitats naturales conduce a una modificación de la comunidad asociada con una planta huésped. En la región central de Brasil es muy común encontrar árboles aislados de “pequi” (Caryocar brasiliense) en medio de monocultivos de soya, maíz, pastos o plantaciones de eucalipto. Bajo este escenario, nosotros predecimos que la modificación del hábitat afecta diferencialmente la diversidad de hormigas y herbívoros asociados a árboles de “pequi”. El objetivo de este artículo fue determinar que árboles de “pequi” localizados en hábitats modificados por actividades humanas (i.e. pastizales y plantaciones de Eucalyptus), soportan una menor abundancia y riqueza de especies de hormigas. Por el contrario, se espera una mayor abundancia y riqueza de especies de herbívoros en hábitats modificados. Este estudio fue realizado en un área de Cerrado (sabana brasileña) localizado en el Norte del estado de Minas Gerais, Brasil. Las hormigas y los herbívoros fueron muestreados usando técnicas de golpe. La riqueza de especies de hormigas fue mayor en árboles de “pequi” localizados en áreas preservadas de Cerrado, seguida por árboles de pastizales y finalmente por árboles de plantaciones de Eucalyptus. La abundancia de hormigas fue menor en plantaciones de Eucalyptus, pero no hubo diferencias en la abundancia de hormigas entre árboles de pastizales y áreas preservadas de cerrado. Por otra parte, el número de especies de insectos herbívoros fue menor en árboles de áreas preservadas de Cerrado que en pastizales y plantaciones de Eucalyptus. Concluimos que las actividades humanas reducen la complejidad del hábitat resultando en la pérdida de la diversidad de insectos y procesos ecológicos.

Simplification of natural habitats leads to a modification of the community associated with a host plant. Pequi trees (Caryocar brasiliense) are common to find in central Brazil, especially in the middle of monocultures, such as soy, corn, pasturelands or Eucalyptus plantations. On this scenario we hypothesized that habitat modification differentially affects the diversity of ants and herbivore insects associated with this species. The aim of the work was to test if C. brasiliense trees located in human modified habitats, support a lower species richness and abundance of ants, and a greater species richness and abundance of insect herbivores, compared to preserved cerrado habitats. The study was conducted in a Cerrado area located in Northern Minas Gerais State, Brazil. Ants and herbivore insects were collected monthly during 2005 using beating technique. The results showed that ant species richness was higher in pequi trees located in preserved Cerrado, followed by trees in pastureland and Eucalyptus plantation, respectively. The ant abundance was lower in the Eucalyptus plantation but no difference in ant abundance was observed between trees in pastureland and the preserved Cerrado. Moreover, herbivore insects exhibited lower number of species and individuals in trees located in the preserved Cerrado than in the pastureland and Eucalyptus plantation. We concluded that habitats simplified by human activities may result in diversity loss and may change species interactions.

Os frutos de Dimorphandra mollis são coletados de forma indiscriminada para fins comerciais, comprometendo a viabilidade das populações naturais. Este estudo teve como objetivo avaliar o efeito da qualidade do solo na germinação das sementes e no desenvolvimento de plântulas de D. mollis. Solos de três procedências (cerrado arenoso, cerrado argiloso e mata seca) foram usados como substratos nos testes de germinação e desenvolvimento das plântulas. As sementes de D. mollis apresentaram maior germinabilidade em solo de cerrado arenoso (60,5%), seguido por solo de cerrado argiloso (29,7%) e solo de mata seca (13,6%). Além disto, o índice de velocidade de germinação (IVG) das sementes de D. mollis foi maior no solo de cerrado arenoso. As raízes das plântulas cultivadas em solo de cerrado arenoso apresentaram maior comprimento do que as cultivadas nos solos de mata seca e cerrado argiloso. Contudo, a massa seca das raízes não variou entre os três tratamentos. As plântulas de D. mollis apresentaram maior crescimento e produção de biomassa da parte aérea quando cultivadas em solo de mata seca. Os solos das matas secas normalmente apresentam melhor qualidade nutricional que os solos do cerrado, justificando os resultados observados. Assim, para melhor sucesso da produção de mudas de D. mollis, as sementes devem ser germinadas em substratos que retêm pouca água e as plântulas devem ser cultivadas em solos de melhor qualidade nutricional.

The exploitative collection of Dimorphandra mollis fruits by farmers has negatively affected the natural population dynamics of this species. The aim of this study was to compare the effects of three soil types (Cerrado sand soil, Cerrado clay soil and dry forest soil) on seed germination and seedling development of D. mollis. The seeds of D. mollis showed greater germinability in Cerrado sand soil (60.5%), followed by Cerrado clay soil (29.7%) and dry forest soil (13.6%). The seedling root growth in Cerrado sand soil was higher compared to Cerrado clay soil and dry forest soil. However, no differences were verified for root dry mass between the soil treatments. The seedlings of D. mollis cultivated in dry forest soil presented a higher growth rate and total dry mass. These results are probably associated with higher nutrient availability, which was verified in the dry forest soil when compared to the Cerrado soils. Our results indicate that D. mollis seeds need a low water-retaining substrate to increase the germination rate and that seedlings develop better in nutrient-rich soils.

La hipótesis de heterogeneidad espacial se ha utilizado para explicar el aumento en la diversidad de especies desde los polos a los trópicos: los trópicos pueden ser más diversos ya que están conformados por una mayor cantidad de hábitats y micro-hábitats. En este estudio, la hipótesis de heterogeneidad espacial se puso a prueba evaluando la variación en la riqueza de dos gremios de insectos herbívoros (formadores de agallas y de alimentación libre) asociados con B. dracunculifolia (Asteracea) a lo largo de un gradiente latitudinal en Brasil. Las diecisiete poblaciones de B. dracunculifolia seleccionadas para el muestreo de insectos herbívoros estaban en hábitats con una estructura similar, a lo largo del límite Norte-Sur de distribución de la planta hospedera, cerca de la costa brasileña. De cada población de planta hospedera, se muestrearon treinta arbustos y se obtuvo un total de 8 201 agallas y 864 insectos de alimentación libre pertenecientes a 28 familias y 88 especies. La mayoría de los insectos que se encontraron en B. dracunculifolia estaban restringidos a un sitio específico en lugar de tener una distribución geográfica similar a la de la planta hospedera. La riqueza de especies de insectos de alimentación libre no se vió afectada por el gradiente latitudinal, por lo que se corroboró la hipótesis de heterogeneidad espacial. Mientras que la riqueza de especies de insectos formadores de agallas se correlacionó positivamente con la latitud, probablemente debido a que los insectos asociados al género Baccharis se extendieron hacia el sur de Brasil. Otros índices de diversidad y equidad estimados no variaron con la latitud para ninguno de los dos grupos de insectos herbívoros evaluados, lo que sugirie una estructura general para diferentes conjuntos de herbívoros asociados con la planta hospedera B. dracunculifolia. Por lo tanto, es probable que, la muestra de insectos en cada sitio sea resultado de eventos a gran escala, como la especiación, migración y coevolución; mientras que a nivel local la población de estos insectos está regulada por fuerzas ecológicas que operan dentro del sistema.

The spatial heterogeneity hypothesis has been invoked to explain the increase in species diversity from the poles to the tropics: the tropics may be more diverse because they contain more habitats and microhabitats. In this paper, the spatial heterogeneity hypothesis prediction was tested by evaluating the variation in richness of two guilds of insect herbivores (gall-formers and free-feeders) associated with Baccharis dracunculifolia (Asteraceae) along a latitudinal variation in Brazil. The seventeen populations of B. dracunculifolia selected for insect herbivores sampling were within structurally similar habitats, along the N-S distributional limit of the host plant, near the Brazilian sea coast. Thirty shrubs were surveyed in each host plant population. A total of 8 201 galls and 864 free-feeding insect herbivores belonging to 28 families and 88 species were sampled. The majority of the insects found on B. dracunculifolia were restricted to a specific site rather than having ageographic distribution mirroring that of the host plant. Species richness of free-feeding insects was not affected by latitudinal variation corroborating the spatial heterogeneity hypothesis. Species richness of gall-forming insects was positively correlated with latitude, probably because galling insect associated with Baccharris genus radiated in Southern Brazil. Other diversity indices and evenness estimated for both gall-forming and free feeding insect herbivores, did not change with latitude, suggesting a general structure for different assemblages of herbivores associated with the host plant B. dracunculifolia. Thus it is probable that, insect fauna sample in each site resulted of large scale events, as speciation, migration and coevolution, while at local level, the population of these insects is regulated by ecological forces which operate in the system. Rev. Biol. Trop. 59 (3): 1419-1432. Epub 2011 September 01.