RESUMO

Differences in the feeding habits between phytophagous and predatory species can determine distinct ecological interactions between mites and their host plants. Herein, plant-mite networks were constructed using available literature on plant-dwelling mites from Brazilian natural vegetation in order to contrast phytophagous and predatory mite networks. The structural patterns of plant-mite networks were described through network specialization (connectance) and modularity. A total of 187 mite species, 65 host plant species and 646 interactions were recorded in 14 plant-mite networks. Phytophagous networks included 96 mite species, 61 host plants and 277 interactions, whereas predatory networks contained 91 mite species, 54 host plants and 369 interactions. No differences in the species richness of mites and host plants were observed between phytophagous and predatory networks. However, plant-mite networks composed of phytophagous mites showed lower connectance and higher modularity when compared to the predatory mite networks. The present results corroborate the hypothesis that trophic networks are more specialized than commensalistic networks, given that the phytophagous species must deal with plant defenses, in contrast to predatory mites which only inhabit and forage for resources on plants.

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The influence of Calacarus heveae Feres on physiological processes was evaluated in two rubber tree clones. Experiments were conducted in a greenhouse with 5-month-old potted seedlings of RRIM 600 and GT 1 clones, that were either infested with C. heveae or not (non-infested control). The level of photosynthetic pigments, net photosynthetic rate, stomatal conductance, transpiration rate, changes in relative humidity between leaf surface and ambient air (Δw) and intercellular CO(2) concentration (Ci CO(2)) were evaluated. Infested plants showed significant reductions in the rate of transpiration, the rate of photosynthesis, stomatal conductance and Δw. RRIM 600 seedlings showed more pronounced physiological damage than GT 1 seedlings, indicating a lower physiological tolerance of the former clone to the mite. However, carotenoid levels were reduced only in GT 1 seedlings. Photosynthesis was probably reduced due to a decrease in stomatal opening, as indicated by reductions in transpiration rate and stomatal conductance and by the absence of differences in chlorophyll levels between treatments. Our results indicate that populations of C. heveae reduce the productivity of rubber trees. Thus, farmers must to be aware to control this mite pest in rubber tree plantations.

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The suitability of rubber tree clones to Calacarus heveae was inferred from the life cycle, reproduction and survivorship of this mite. The assays were performed under controlled conditions with leaflets detached from 6-year-old plants. The development of 20 C. heveae individuals on each of the clones GT 1, PB 235 and RRIM 600 was analysed. This experiment was performed four times during periods when C. heveae was abundant in the field: (P1) November-December 2005, (P2) January-February, (P3) March-April and (P4) May-June 2006. Accordingly, the leaflets used in each assay represented the physiological condition of the host plant during each period. This approach allowed us to evaluate the seasonal suitability of rubber tree clones to C. heveae. We observed seasonal differences in the suitability of rubber tree clones to mite attack. The mites reared on the PB235 had a shorter development period, the highest egg production and highest survivorship. This evidence showed that the PB 235 was the most suitable of those tested. We also observed that the leaflets used in the assays during periods P2 and P3 were the most favourable for the development of C. heveae. This finding emphasises the seasonal suitability of rubber tree leaflets. On the other hand, GT 1 showed higher resistance against C. heveae than did RRIM 600 and PB 235, primarily during the period from November to February. This result indicated that use of the GT 1 clone to control the mite might represent an alternative for growers.

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We conducted experiments by blocking off pit-like domatia from old and new leaves of Coffea arabica L., using tiny resin drops, to investigate the role of domatia on i) mite abundance at the community level and on ii) leaf damages. More than 77 percent of the mites collected were predators, whereas 19 and 3.3 percent were omnivores and phytophages, respectively. Domatia blockage treatment had no influence either on mite abundances or leaf damages. However, predatory and omnivorous mites were more abundant on new than on the old leaves; phytophagous mites occurred at very low density and occupied only plants having open domatia. The absence of mutualism between mites and C. arabica probably occurred because the entrances of domatia were too small and did not enable the entry of fitoseid predators in these structures.

Domácias são pequenas estruturas presentes na junção entre as nervuras principal e secundárias das folhas de muitas espécies de plantas, que podem mediar interações mutualísticas entre ácaros e plantas. Em experimento, nós bloqueamos as domácias em formato de covas de folhas novas e velhas de Coffea arabica L. com gotas de resina, a fim de investigar o seu papel i) na abundância de ácaros na comunidade e ii) nos danos foliares. Mais de 77 por cento dos ácaros coletados são predadores, enquanto 19 e 3,3 por cento são onívoros e fitófagos, respectivamente. Não houve influência do bloqueio das domácias tanto na abundância quanto nos danos foliares. Entretanto, os ácaros predadores e micófagos foram mais abundantes nas folhas novas do que nas velhas; os ácaros fitófagos ocorreram em pequena densidade e ocuparam somente as plantas com domácias abertas. A ausência de mutualismo entre os ácaros e plantas de C. arabica pode ter ocorrido porque as entradas das domácias analisadas eram muito pequenas, não permitindo a entrada dos predadores fitoseídeos nessas estruturas.

RESUMO

Foram estudadas as comunidades de ácaros em indivíduos de Hymenaea martiana Hayne (Leguminosae) com diferentes tamanhos, localizados em fragmento de Mata Estacional Semidecidual com transição para o Cerrado. As plantas analisadas foram selecionadas com base no gradiente de altura e perímetro do tronco a 10 cm acima do solo. Foram realizadas coletas quinzenais no período de março de 2007 a março de 2008. Em cada amostragem foram retiradas três folhas dos ramos externos e três dos ramos internos, ao redor da região mediana da copa de cada planta selecionada. Para comparar os padrões ecológicos das comunidades de ácaros entre as plantas, foram aplicados índices descritores da diversidade. Em H. martiana, foram registrados 109.445 ácaros pertencentes a 28 espécies de 14 famílias. Nove espécies de ácaros, dentre as 19 classificadas como frequentes e acessórias, tiveram sua densidade populacional influenciada pelo tamanho da planta. Enquanto a densidade populacional de Chiapacheylus edentatus De Leon, 1962, Euseius cf. errabundus, Pronematus sp., Brevipalpus phoenicis (Geijskes, 1939) e Tarsonemus sp., apresentou correlação positiva com a altura da planta, a de Aberoptus aff. cerostructor, Euseius sibelius (De Leon, 1962), Typhlodromalus aripo De Leon, 1967 e Phytoseius nahuatlensis De Leon, 1959, apresentou correlação negativa. Não houve influência da altura da planta sobre a riqueza de espécies e densidade total de ácaros entre ramos internos e externos das plantas com diferentes alturas. As variações fisiológicas entre os indivíduos de diferentes estágios ontogenéticos de H. martiana, juntamente com fatores abióticos, podem ter influenciado a ocorrência e a distribuição dessas espécies de ácaros sobre essa planta.

The mite communities on plants with different sizes of Hymenaea martiana Hayne (Leguminosae) were studied in a remnant of Mata Estacional Semidecidual in transition to Cerrado forest. The plants were selected according to the height and perimeter of trunk at 10 cm from the soil. Biweekly samples from March 2007 to March 2008 were performed, with three leaves collected from the outer and three from the inner branches at level of median canopy region for each plant selected. Diversity indexes were applied in order to verify the ecological patterns of mite community among the plants. We recorded 109,445 mites belonging to 28 species and 14 families on H. martiana. The population density of nine species of mites, among 19 classified as frequent and accessory, varied according to the plant size. While the population densities of Chiapacheylus edentatus De Leon, 1962, Euseius cf. errabundus, Pronematus sp., Brevipalpus phoenicis (Geijskes, 1939) and Tarsonemus sp. had positive correlation with the plant size, the densities of Aberoptus aff. cerostructor, Euseius sibelius (De Leon, 1962), Typhlodromalus aripo De Leon, 1967 and Phytoseius nahuatlensis De Leon, 1959 had negative correlation. There was no influence of the plant height on the species richness and total density of mites between leaves from the inner and outer branches sampled in plants with different sizes. The physiological variations between individuals of H. martiana in different ontogenetic stages, in addition to abiotics traits, might have influenced the occurrence and distribution of mites on this plant.

RESUMO

Life cycle of Tenuipalpus heveae Baker (Acari, Tenuipalpidae) on leaflets from three rubber tree clones. The biological cycle of Tenuipalpus heveae Baker, 1945 (Tenuipalpidae), a potential rubber tree pest mite, was studied by the observation of individuals reared on leaflets of the clones GT 1, PB 235 and RRIM 600, in controlled environmental conditions. Three daily observations were done of 60 eggs on leaflets from each clone in order to verify the development of immature stages and the female oviposition. The fertility life table was constructed based in the collected data. Mites reared on PB 235 had faster rate of development, requiring less time in days, to double its population in number (TD), and had the highest values for egg production, female longevity, net reproductive rate (Ro), intrinsic rate of natural increase (r m) and finite rate of increase (λ). Lower reproductive values and the longest time necessary to reach adult stage were recorded for the mites on GT 1. In all studied clones, the deutonymphal phase had the highest viability, while the larval phase had the lowest, highlighted by the survivorship curve that indicated high mortality during this life stage. The clone PB 235 allowed the most suitable conditions for the development of T. heveae, followed by RRIM 600, while GT 1 was the less suitable substratum to rear this mite species.

O ciclo de vida de Tenuipalpus heveae Baker, 1945 (Tenuipalpidae), um potencial ácaro-praga da seringueira, foi estudado a partir de indivíduos criados sobre folíolos destacados dos clones GT 1, PB 235 e RRIM 600, em condições controladas. Três observações diárias foram realizadas, acompanhando-se o desenvolvimento de 60 ovos e de sua prole em folíolos de cada um dos clones, para verificação da oviposição das fêmeas e dos estágios de desenvolvimento. A partir dos dados obtidos, foi elaborada uma tabela de vida de fertilidade. Os ácaros criados sobre folíolos de PB 235 apresentaram rápido ciclo biológico, com menor tempo gasto, em dias, para duplicar sua população (TD) e os maiores valores para a produção de ovos, longevidade de fêmeas, taxa líquida de reprodução (Ro), taxa intrínseca de crescimento populacional (r m) e taxa finita de crescimento populacional (λ). Em GT 1 foram observados valores inferiores e o maior tempo de desenvolvimento necessαrio para atingir a fase adulta. Em todos os clones estudados a fase de maior viabilidade foi a deutoninfal, enquanto a menor, a larval, como evidenciado tambιm pelas curvas de sobrevivência, que indicaram maior mortalidade nesse estágio juvenil. O clone PB 235 possibilitou melhor desenvolvimento para T. heveae, seguido por RRIM 600, enquanto que GT 1 foi o menos favorável ao desenvolvimento dessa espécie.

RESUMO

Foi estudada a dinâmica populacional de Calacarus heveae Feres, 1992, Phyllocoptruta seringueirae Feres, 1998 (Eriophyidae) e Tenuipalpus heveae Baker, 1945 (Tenuipalpidae) em seis clones de seringueira (Hevea brasiliensis Muell. Arg.), com o intuito de conhecer a sazonalidade e as possíveis diferenças nos níveis de infestação dessas espécies sobre os diferentes clones, em seringal localizado no sul do Estado de Mato Grosso. Para isso, no período de março de 2004 a março de 2005, foram realizadas coletas num intervalo médio de catorze dias em seis parcelas clonais. Em cada amostragem, foram analisados 100 folíolos de cada parcela, registrando-se o número total de ßcaros encontrados em ambas as faces. Os níveis de infestação das espécies variaram entre os diferentes clones. O clone RRIM 600 apresentou maior abundância de T. heveae, enquanto que PB 235 e PB 260 de P. seringueira e C. heveae, respectivamente. Por outro lado, esse último clone apresentou menor número de indivíduos de T. heveae e P. seringueirae, e PB 235 de C. heveae. O primeiro semestre foi o período crítico de infestação, porém a duração da ocorrência e o pico de abundância dos fitófagos variaram nos diferentes clones.

The population dynamics of Calacarus heveae Feres, 1992, Phyllocoptruta seringueirae Feres, 1998 (Eriophyidae) and Tenuipalpus heveae Baker, 1945 (Tenuipalpidae) was studied on six rubber tree clones (Hevea brasiliensis Muell. Arg.) in south of Mato Grosso State, Brazil, in order to verify the seasonality and the possible differences on the infestation levels of these mites. The samplings were made from March 2004 to March 2005, with an average interval of fourteen days between each sampling. In each sampling, 100 leaflets were taken from each clone crop, and the total number of mites found in both leaf surfaces was registered. The infestation levels of mites differed among the clones. The clone RRIM 600 showed the highest number of T. heveae, while PB 235 and PB 260 had the highest abundance of P. seringueirae and C. heveae, respectively. On the other hand, this latter clone had the smallest infestation of T. heveae and P. seringueirae, while in PB 235 the lowest population of C. heveae. The critical period of mite infestation was observed in the first semester, although, there was variation in the duration of phytophagous occurrence and the infestation peak on six rubber trees clones studied.

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Foi estudada a diversidade e a sazonalidade da comunidade de ácaros em três euforbiáceas nativas de um fragmento de mata estacional semidecidual, através de coletas mensais realizadas de maio de 2003 a abril de 2004. Foram aplicados índices descritores de diversidade, dominância e de equitatibilidade, para estudar os padrões ecológicos da comunidade, e a correlação linear de Pearson, para relacionar a abundância dos ácaros com a pluviosidade. Foram registrados 11.515 ácaros pertencentes a 111 espécies de 73 gêneros e 25 famílias. Dessas espécies, 44 por cento são generalistas enquanto que 21 e 35 por cento são fitófagas e predadoras, respectivamente. As fitófagas foram as mais abundantes, representando 45,7 por cento do material coletado, seguido pelas predadoras e generalistas, que constituíram 40,5 e 13,7 por cento dos espécimes amostrados, respectivamente. Phytoseiidae foi a família com a maior riqueza de espécies (23), seguida por Tarsonemidae (18) e Tydeidae (16). As três euforbiáceas estudadas apresentaram grande diversidade de espécies, pois os índices calculados foram superiores a 50 por cento da diversidade máxima teórica prevista. O padrão de abundância da comunidade foi igualmente descrito pelos padrões geométrico e logarítmico. Das três espécies de plantas estudadas, apenas Acalypha diversifolia apresentou potencial para utilização em programas de Manejo Integrado de Pragas.

The diversity and seasonality of mite community on three indigenous euphorbiaceous plants from a Semidecidual forest remnant were studied by means of monthly samplings performed from May 2003 to April 2004. Diversity, dominance and equitability indexes were applied in order to verify community ecological patterns, and the Pearson correlation coefficient was used to relate mite abundance with the rainfall. About 11,515 mites belonging to 111 species of 73 genera in 25 families were recorded. Among these species, 44 percent of them were generalists, while 21 and 35 percent are phytophagous and predatory, respectively. The phytophagous mites were the most abundant, performing 45.7 percent of mites collected, followed by the predatory and generalist species, which represented 40.5 and 13.7 percent of material sampled, respectively. The Phytoseiidae family showed the highest species richness (23), followed by Tarsonemidae (18) and Tydeidae (16). The three euphorbiaceous plants studied showed great species diversity, as the results of indexes were higher than 50 percent of theoretical maximum diversity. The species-abundance patterns determined for mite community was equally represented by geometric and log series models. Out of three plant species studied, only Acalypha diversifolia showed potential usage in Integrated Pest Management programs.

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