La relation entre l'allocation aux composés secondaires et le taux de croissance relatif chez les Asteraceae

Differences in resource availability have been shown to generate variation in defense chemistry in some species, but proper interspecific studies are rare and give conflicting results. This study focused on the trade-off between growth and production of chemical compounds of plants grown under different resource availabilities. I tested the hypothesis that: (1) contrasting plant species grown under controlled and enriched environmental conditions will show a negative correlation between their relative growth rates and their secondary compounds; (2) there is a negative correlation between mobile defenses (measured by the toxicity bioassay) and immobile defenses (measured by total phenol concentration) of plants grown under suboptimal environmental conditions; (3) plants grown under light-stressed conditions but optimal nutrient conditions will produce less carbon-based secondary compounds than plants grown under nutrient-stressed conditions but optimal fight conditions; and (4) plants grown under optimal environmental conditions will have a high RGR but will produce less secondary compounds than plants grown under stressful environmental conditions. Hypothesis 1 was tested experimentally using 31 species of Asteraceae grown with high levels of mineral and light resource availability under controlled conditions. Hypothesis 2 was tested in 20 species of Asteraceae by examining if there is any correlation between relative growth rate and secondary metabolism, and if there is any correlation between the type of chemical defense (mobile and immobile) in plants grown under controlled conditions of high light intensity but suboptimal levels of mineral nutrients. To test hypotheses 3 and 4, I conducted an experiment using six species of Asteraceae grown under 11 different combinations of light and mineral resources availabilities. Also, I investigated if there was any difference concerning the amount of specific secondary compounds, measured with HPLC produced by high light intensity and two levels of mineral resources availabilities in two of the six species ( Chrysanthemum leucanthemum and Rudbeckia hirta ). This thesis provided evidence that the resources availabilities affect the growth and the chemical parameters in different ways, but the data of this thesis shows no trade-off between growth and chemical defense when comparing species within a given experiment. The relative growth rate and the specific leaf area are affected by reducing the mean values under nutrient stress. In contrast, the root:shoot ratio increased under such conditions. As expected, leaf nitrogen content was reduced under nitrogen stress. The complication occurs in the parameters related to chemical defense; while total phenolics content increased, toxicity decreased. Finally, I did not detect the presence of any polyacetylenes or sesquiterpene lactones by HPLC in the leaves of the two species tested. The amount of pentaynene produced in the flowers of Rudbeckia hirta decreased significantly with age but increased significantly when the plant was subjected to a reduced nutrient availability

Impacts des mammifères néotropicaux sur les graines

Seeds dispersal and predation by mammals are two key processes affecting the dynamics of plant communities. Neotropical rainforests, which are of great complexity, have many different relationships involving plant propagules and mammals. Dispersal allows the seed to escape competition and predation, to colonize new sites and to establish in favorable micro-sites. Seed predation reduces the number of seeds able to germinate, can affect dispersal of the remaining seeds and is one of the mecanisms that maintain a high plant species diversity in tropical rainforests. Didelphimorphs and chiropteras are very good dispersers that have a primary role in forest regeneration. Seed predation is very rare in these taxons. Primates, the most studied group on this subject, are also very good dispersers, sometimes predators, and possess an extremely diverse diet. Ungulates can be either dispersers, predators, or both. Their importance is due to their ability to consume generally larger seeds than other mammals. Rodents do not show a net profile and are distinctive by their synzoochore behaviour, consisting of hiding seeds and feeding on them later. An important part of cached seeds can be forgotten and later germinate. The role of carnivores in seed predation or dispersal is poorly known but a few studies show that they could be effective dispersers. Key words: dispersal, mammal, neotropical, predation, seed, zoochory.La dispersion et la prédation des graines par les mammifères sont deux processus-clés de la dynamique des communautés végétales. Les forêts humides néotropicales, dont la grande complexité est reconnue, présentent un éventail très vaste de relations mammifèrespropagules des plantes. La dispersion permet aux graines d’échapper à la compétition, à la prédation, de coloniser de nouveaux sites et de s’établir dans des micro-sites favorables. La prédation diminue le nombre de graines candidates à la germination, peut affecter la dispersion des graines restantes et constitue un mécanisme de maintien de la grande diversité végétale en forêt tropicale. Les didelphimorphes et les chiroptères sont de très bons disperseurs qui ont un rôle primordial dans la régénération de la forêt. Les cas de prédation des graines dans ces deux taxons sont très rares. Les primates, taxon le plus étudié à ce jour sur le sujet, sont également de très bons disperseurs, parfois prédateurs, qui possèdent une diète extrêmement variée. Les ongulés peuvent être disperseurs ou prédateurs, l’un n’excluant pas l’autre. Leur importance se situe dans leur habilité à consommer des graines en général plus grosses que les autres mammifères. Les rongeurs ne présentent pas un profil net et se distinguent par leur comportement de synzoochorie, consistant à cacher des graines afin de s’en nourrir plus tard. Une part importante de ses graines sera cependant oubliée et candidate à la germination. Le rôle des membre de l’ordre des carnivores est très peu connu, mais quelques études effectuées montrent qu’ils peuvent être d’efficaces disperseurs. Mots-cles: dispersion, graine, mammifère, néotropical, prédation, zoochorie

Impacts des mammifères néotropicaux sur les graines

Seeds dispersal and predation by mammals are two key processes affecting the dynamics of plant communities. Neotropical rainforests, which are of great complexity, have many different relationships involving plant propagules and mammals. Dispersal allows the seed to escape competition and predation, to colonize new sites and to establish in favorable micro-sites. Seed predation reduces the number of seeds able to germinate, can affect dispersal of the remaining seeds and is one of the mecanisms that maintain a high plant species diversity in tropical rainforests. Didelphimorphs and chiropteras are very good dispersers that have a primary role in forest regeneration. Seed predation is very rare in these taxons. Primates, the most studied group on this subject, are also very good dispersers, sometimes predators, and possess an extremely diverse diet. Ungulates can be either dispersers, predators, or both. Their importance is due to their ability to consume generally larger seeds than other mammals. Rodents do not show a net profile and are distinctive by their synzoochore behaviour, consisting of hiding seeds and feeding on them later. An important part of cached seeds can be forgotten and later germinate. The role of carnivores in seed predation or dispersal is poorly known but a few studies show that they could be effective dispersers. Key words: dispersal, mammal, neotropical, predation, seed, zoochory.La dispersion et la prédation des graines par les mammifères sont deux processus-clés de la dynamique des communautés végétales. Les forêts humides néotropicales, dont la grande complexité est reconnue, présentent un éventail très vaste de relations mammifèrespropagules des plantes. La dispersion permet aux graines d’échapper à la compétition, à la prédation, de coloniser de nouveaux sites et de s’établir dans des micro-sites favorables. La prédation diminue le nombre de graines candidates à la germination, peut affecter la dispersion des graines restantes et constitue un mécanisme de maintien de la grande diversité végétale en forêt tropicale. Les didelphimorphes et les chiroptères sont de très bons disperseurs qui ont un rôle primordial dans la régénération de la forêt. Les cas de prédation des graines dans ces deux taxons sont très rares. Les primates, taxon le plus étudié à ce jour sur le sujet, sont également de très bons disperseurs, parfois prédateurs, qui possèdent une diète extrêmement variée. Les ongulés peuvent être disperseurs ou prédateurs, l’un n’excluant pas l’autre. Leur importance se situe dans leur habilité à consommer des graines en général plus grosses que les autres mammifères. Les rongeurs ne présentent pas un profil net et se distinguent par leur comportement de synzoochorie, consistant à cacher des graines afin de s’en nourrir plus tard. Une part importante de ses graines sera cependant oubliée et candidate à la germination. Le rôle des membre de l’ordre des carnivores est très peu connu, mais quelques études effectuées montrent qu’ils peuvent être d’efficaces disperseurs. Mots-cles: dispersion, graine, mammifère, néotropical, prédation, zoochorie

Occurrence of gall complexes along a topographic gradient in an undisturbed lowland forest of central Amazonia

The species richness of gall-inducing insects and their host plants, in an undisturbed lowland forest in central Amazonia, was analyzed to test whether there is a higher occurrence of galls in mesic campinarana habitats when compared to plateaus, slopes and valleys. In October 2005, 300 plants, which were 1 to 2 meters tall, were sampled along ten transects (5 meters wide) per habitat. Gall-inducing insects were found in only 35 (3%) of the 1200 plants studied. Thirteen families, eight genera and 27 morphospecies of plants were identified. The families Burseraceae and Rubiaceae had the highest number of host plant species. There was no significant difference in species richness between habitat types. However, the gall-inducing insects and host plant species were exclusive to each habitat. Furthermore, the frequency of host plants in campinarana was not higher when compared to the other habitats. Probably, tree canopies present more structural complexity, light availability and incidence of leaves with scleromorphic characteristics than understory plants, resulting in vertical stratification with a higher amount of gall-inducing insects in canopies when compared with individuals of the same species in the understory. The higher plant diversity and variation of physical characteristics of the forests in central Amazonia can help explain why specific interactions and the frequency of gall-inducing insects were found in each habitat. The results of this study indicate that central Amazonian forests have a high diversity of gall-inducing insects with an exclusive fauna related to each habitat, which is potentially due to the greater environmental heterogeneity, and suggests the importance of conducting additional studies about galling insects, principally in forest canopies.(Ocorrência de galhas ao longo de um gradiente topográfico em uma floresta de terra firma na Amazônia Central). A riqueza de insetos galhadores e plantas hospedeiras foram investigadas em uma floresta de terra firme, na Amazônia Central, para testar se haveria uma maior ocorrência de galhas em habitats mais secos, como campinarana, comparados aos platôs, vertentes e baixios. Em outubro de 2005, foram amostradas 300 plantas em 10 transecções (com 5 m de largura cada) por habitat, totalizando 1.200 plantas.  As galhas induzidas por insetos foram encontradas em apenas 35 (3%) das 1.200 plantas estudadas. Treze famílias, oito gêneros e 27 morfoespécies de plantas foram identificados, sendo que as famílias Burseraceae e Rubiaceae apresentaram maior número de espécies de plantas hospedeiras. Não foi observada nenhuma diferença significativa na riqueza de espécie de galhas induzidas por insetos entre os habitats, porém as interações foram exclusivas de cada habitat. Além disso, campinarana não apresentou maior frequência de plantas hospedeiras, em comparação aos outros habitats. Provavelmente, as copas das árvores apresentam maior complexidade estrutural, disponibilidade de luz e ocorrência de plantas com características escleromórficas do que o sob-bosque, resultando em uma estratificação vertical e maior frequência de galhas nas copas quando comparada com indivíduos da mesma espécie no sub-bosque. A alta diversidade vegetal e a variação abiótica podem explicar a especificidade e frequência de interações em cada habitat. Nossos resultados indicam que a vegetação da Amazônia Central apresenta uma alta riqueza de galhas entomógenas, além de um grande potencial para uma exclusiva fauna associada a cada habitat, devido a grande heterogeneidade ambiental, e recomenda o desenvolvimento de estudos com insetos galhadores, principalmente nas copas das árvores

Predação e disponibilidade de reservas em sementes de

Predação e disponibilidade de reservas em sementes de <Clitoria fairchildiana na fase de pré-dispersão em  duas populações presentes em ambientes distintos</htm

Richness of gall morphospecies along a secondary successional gradient of Atlantic Forest in northeastern Brazil

Galling insects have been recommended as an excellent tool to evaluate environmental changes and habitat quality. In this study, we assessed the richness of gall morphospecies, as well as host-plant richness and abundance, to detect environmental changes in six patches of secondary Atlantic Forest in Northeast Brazil. The patches of forest varied in age (between 25 and 42 yrs) and size. In each patch, the plants between 1 and 3 meters tall were evaluated for a period of one hour, totaling six hours. A total of 50 gall morphospecies were found on 37 host-plant species (88 plant individuals). We identified 27 (72%) host-plant species belonging to 19 plant families. Richness of gall morphospecies and host-plant richness and abundance were not significantly affected by the age and size of the patch. However, the richness of gall morphospecies increased significantly as the host-plant percentage of shade-tolerant trees increased. Considering that the differences observed in this study, between younger and older patches, developed in a relatively short time period of forest recovery (c. 18 yrs), and that some host-plant species occurred exclusively in older patches, this study showed that gall-inducing insects are a good tool for evaluating changes in a secondary successional gradient. The use of gall-inducing insects as bioindicators in restoration and conservation programs is not only a good opportunity to advance this type of study but is also a useful application, at local and regional scales, to monitor the successional progress of forests.(Riqueza de morfoespécies de galhas ao longo de um gradiente sucessional em trechos de floresta Atlântica secundária no nordeste do Brasil). Insetos galhadores têm sido indicados como uma excelente ferramenta para avaliar as mudanças ambientais e a qualidade do habitat. Neste estudo, a riqueza de morfoespécies de galhas como também a riqueza e abundância de plantas hospedeiras foram avaliadas para detectar possíveis mudanças ambientas em seis trechos de floresta secundária em um remanescente de Floresta Atlântica localizado no nordeste do Brasil. Os trechos apresentaram diferentes tamanhos e idades de regeneração (entre 25 e 42 anos). Em cada trecho, as plantas entre 1-3 metros de altura foram inspecionadas durante uma hora, totalizando seis horas. Um total de 50 morfoespécies foi encontrado em 37 plantas hospedeiras (88 indivíduos). Foram identificadas 27 (72%) plantas distribuídas em 19 famílias. A riqueza de morfoespécies e a riqueza e abundância de plantas hospedeiras não foram afetadas com a idade de regeneração ou pelo tamanho do trecho. Porém, a riqueza de morfoespécies aumentou significantemente aumentando a porcentagem de plantas hospedeiras tolerantes à sombra. Considerando que nossos resultados foram observados em um curto intervalo sucessional (ca. 18 anos), e que algumas das plantas hospedeiras ocorreram exclusivamente em trechos mais avançados, é possível indicar os insetos galhadores como uma eficiente ferramenta de biomonitoramento. O uso destes insetos como bioindicadores em programas de restauração e conservação não é apenas uma boa oportunidade para avançar os estudos e tornar sua aplicação viável em uma escala local e regional, mas também decisivo no monitoramento do progresso sucessional

Variação nas concentrações de compostos fenólicos e nas taxas de herbivoria em Aspidosperma pyrifolium Mart. em áreas antropizadas de Caatinga

Disponibilidade de recursos e perturbações antrópicas possuem relevância nas respostas à atuação dos herbívoros. Ao longo da evolução as plantas desenvolveram estratégias de defesa contra a herbivoria, como as defesas químicas. O objetivo deste trabalho foi analisar a relação entre as taxas de herbivoria e caracteres biométricos de Aspidosperma pyrifolium Mart, e o conteúdo foliar de compostos fenólicos/taninos, em áreas de Caatinga, com e sem perturbações antrópicasna microrregião de Itaparica, Pernambuco. Foram realizadas medidas de taxa de herbivoria, biometria,e conteúdo de carbono, nitrogênio e compostos fenólicos/taninos. Os dados foram analisados através de ANOVA fatorial seguida de teste de Tukey (5%), e análises correlação e regressão linear simples. Os parâmetros biométricos não apresentaram diferenças entre as áreas, nem relação com o conteúdo de compostos fenólicos. Os conteúdos de nitrogênio foram maiores no mês mais seco, enquanto os de carbono foram maiores no fim da estação chuvosa. Concentrações de compostos fenólicos/taninos tiveram relação negativa com as taxas de herbivoria das áreas impactadas, mas nas áreas preservadas essa relação não foi observada. O consumo prévio das folhas por caprinos pode ter estimulado o aumento na produção de compostos de defesa nas áreas impactadas, o que ocasionou queda nas taxas de herbivoria por insetos. Já nas áreas preservadas a diminuição significativa da herbivoria em Junho pode estar ligada ao fim do ciclo de crescimento de alguns invertebrados Embora a influência da pecuária extensiva possa ser notada em áreas impactadas ela não pode ser considerada a causa única da relação herbivoria/produção de compostos fenólicos

Dieta de Tapirus terrestris Linnaeus em um fragmento de Mata Atlântica do Nordeste do Brasil

The lowland tapir (Tapirus terrestris Linnaeus, 1758) is the largest mammalian herbivore in Brazil. Only small numbers remain in Atlantic Forest fragments in north-east Brazil. The population downfall of the lowland tapir is linked to hunting, and to the destruction and fragmentation of its habitat. Changes in the environment may impact the diet of this potentially at-risk mammal. We focused on tapirs living in the Mata dos Pintos, a 3 000 ha forest fragment on the Usina Serra Grande land (state of Alagoas, Brazil). We determined diet by following the paths of tapirs to collect plant species they foraged on. Foraging occurrence was assessed by visual identification of markings (teeth marks on stems and leaves) and seeds identification in the feces. Fifty-five plant species were identified as consumed by tapirs of Mata dos Pintos including 42 browsed species. The mostcommon plant families consumed were Rubiaceae, Melastomataceae and Arecaceae, which are all specific to secondary forest types or forest edge. Seeds of 19 plant species were found in the feces of tapirs. Of these species, fifteen were found with intact seeds and six of these possessed large seeds (>1,5 cm). The size of the intact seeds found in tapir feces and the long gastrointestinal passage time of this species implies that tapirs may act as long-distance seed dispersers for large-seeded plant species, which may have few alternative dispersal mechanisms in highly fragmented forests.A anta (Tapirus terrestris Linnaeus, 1758) é o maior mamífero herbívoro do Brasil. A população de anta está restrita somente a poucos indivíduos, nos fragmentos de mata Atlântica do nordeste brasileiro. Esta população reduzida está ligada à caça, à destruição e à fragmentação de seu habitat, uma vez que as mudanças ocorridas em seu ambiente podem impactar sua rotina diária e sua dieta. Duas antas que vivem no fragmento ”Mata dos Pintos”, Usina Serra Grande (Alagoas) foram o foco principal deste trabalho. A dieta das antas foi determinada seguindo suas trilhas. As plantas que apresentavam marcas de dentes nos caules e folhas foram coletadas, bem como as sementes encontradas nos excrementos. Quarenta e duas espécies vegetais foram consumidas pelas antas da mata dos Pintos, das quais as mais frequentes foram Rubiaceae, Melastomataceae e Arecaceae, típicas de florestas secundárias. Sementes de dezenove espécies foram encontradas nos excrementos das antas, destas 15 estavam intactas, sendo seis sementes grandes (> 1,5cm). O porte grande e o tempo de passagem digestivo da anta implica na dispersão a longas distâncias de sementes grandes, com poucos mecanismos alternativos de dispersão na floresta Atlântica altamente fragmentada

Plant organ abscission and the green island effect caused by a coleopteran’s gall on Miconia cf cinnamomifolia (Melastomataceae): larval survival and mortality factors

Galls are characterized by inducing cellular differentiation (hyperplasia or hypertrophy) resultant of the action of some organisms, mainly insects, on structures/organs of their host plants. The galls cause physiological changes in host plants, altering host traits, and their growth and survival. The early abscission of galled plant organs can be a form of plant defense. Therefore, the galls decayed more slowly than the healthy leaves, or the surrounding healthy leaf tissue in some abscised galled leaves, forming “green island galls”. This study reported an instance where the host plant Miconia cinnamomifolia (Melastomataceae) abscises leaves galled by an unidentified coleopteran’s gall on the soil of a fragment of Atlantic Forests, Brazil. Once on the forest soil galls were exposed to a new set of potential natural enemies, as pathogens and predators. Consequently, larval survival decrease of 79% to 36% in four months and fungal infestation increase of 2% to 21%. Neither size nor weight of the galls differed between categories of mortality factors and larval survival. It was discussed the adaptive nature of the “Green Island Effect” as a counter-response of gallers to leaf abscission, which is a known plant defense strategy