Diversidad de los artrópodos fitófagos del cultivo de arándano (Vaccinium corymbosum) en la Argentina. Atributos poblacionales y factores de mortalidad de las principales especies

• Autores: Margarita Rocca
• Directores de la Tesis: Graciela Mareggiani (dir. tes.), Nancy M. Greco (codir. tes.)
• Lectura: En la Universidad Nacional de La Plata ( Argentina ) en 2010
• Idioma: español
• Enlaces
  • Tesis en acceso abierto en:  sedici.unlp.edu.ar  doi.org 
• Resumen
  • español

    El arándano, Vaccinium corymbosum, es un arbusto perenne originario del hemisferio Norte, donde constituye un cultivo importante y tradicional. En América del sur, se introdujo en Chile en la década del 80, y una década después en nuestro país. En la actualidad existen más de 4.700 ha con plantaciones de arándanos principalmente en Buenos Aires, Entre Ríos y Tucumán. En EEUU se conocen más de 300 especies de herbívoros en el cultivo de arándano, aunque sólo algunas causan pérdidas económicas. En Chile, la mayoría de las especies no se consideran plagas y en la Argentina la información sobre los artrópodos en el cultivo de arándano es escasa. En los sistemas agrícolas la diversidad de las comunidades locales puede explicarse a partir de la composición específica regional, por lo cual es importante estudiarla considerando distintas escalas espaciales (local, de paisaje, de región). La introducción del arándano significa un cambio en el ambiente, fundamentalmente en términos de recursos alimenticios, para las comunidades de herbívoros presentes en el ecosistema. Cuando un cultivo es introducido en una región son los insectos nativos, o los que forman parte del conjunto regional de especies, los que se adaptan a utilizar este nuevo recurso, y la mayoría de estos insectos son polífagos. La composición de las comunidades locales dependerá además del paisaje al cual pertenezcan. El objetivo principal de esta Tesis fue conocer la composición taxonómica y funcional de la comunidad de herbívoros de los cultivos de arándano de las provincias de Buenos Aires y Entre Ríos, interpretar los patrones encontrados, analizar las variaciones numéricas de las especies más frecuentes y/o abundantes e identificar sus enemigos naturales y la mortalidad que producen. La estructura de las comunidades de herbívoros se analizó en este estudio a través de tres enfoques: la diversidad de especies, la organización funcional y las interacciones entre las especies.

  • English

    The blueberry, Vaccinium corymbosum, is a perennial shrub native to the northern hemisphere, where it is an important and traditional culture. In South America, where it was introduced in the '80 in Chile, and a decade later it was introduced into our country. Actually, there are more than 4,700 hectares planted with blueberries, mainly in Buenos Aires, Entre Ríos and Tucumán. In the U.S. there are more than 300 species of herbivores present in the crop, but only some of them reach densities enough to cause economic losses. In Chile, the majority of arthropods recorded in cultivation are not considered pests. In Argentina, information on arthropods in the crop is sparse.

    In agricultural systems the diversity of local communities can be explained from the regional pool of species, so it is important to study considering different spatial scales (local, landscape, region). The introduction of blueberry means a change in the environment, primarily in terms of food resources for the communities of herbivores present in the ecosystem. When a crop is introduced into a region, are native insects or those who are part of the regional pool of species which are adapted to use this new resource, and most of these insects are polyphagous. The composition of local communities would also depend on the landscape to which they belong.

    The main objective of this Thesis was to study the taxonomic and functional composition of the herbivore community of blueberry crop in the provinces of Buenos Aires and Entre Ríos, interpret the patterns found and analyze the numerical variations of the most frequent and / or abundant species and identify their natural enemies and the mortality that they causes.

    In Buenos Aires, one blueberry crop was selected in Colonia Urquiza, one in Chascomús, one in San Pedro and one in Gebernador Castro. In Entre Rios, two crops were selected in Concordia. The blueberry crops were located in different landscapes.

    Sampling was conducted from June 2006 until December 2008, samples were taken monthly at sites of Buenos Aires while in Entre Rios they were taken for each phenological stage. Samples were obtained from the aerial parts of the plant (leaves, buds, flowers and fruits), and in some cases soil samples. All insects present were registered.

    The richness of herbivorous families registered at all sites throughout the study period was 31, belonging to orders Hemiptera, Lepidoptera, Coleoptera, Orthoptera, Thysanoptera and Hymenoptera. The richness varied over the years of study among the different sites of Buenos Aires, reflecting a decrease in 2008 in San Pedro and Gobernador Castro, probably due to the presence of tourist species in 2007. Gobernador Castro crop had the highest richness, which is surrounding by a diversity of crops.

    The variation between different crop phenological stages was also significant, presenting the richest variation, the stages V2 and V3. At sites of Entre Rios, there were no significant differences in the richness of families across sites, phenological stages and years.

    In Buenos Aires and Entre Rios, diversity calculated by Shannon-Wiener index was not significantly among different sites, phenological stages and years. In relation to the dominance of families, aphids presented the highest abundance in all sites. The highest values of Simpson's index (λ) were recorded at sites of Chascomús and San Pedro. In Chascomús, surrounded by extensive crops, followed in abundance Thripidae and Tortricidae. In Gobernador Castro, in a landscape composed of citrus and natural crops were important Margarodidae and Coccidae, in Colonia Urquiza, horticultural and floricultural area, the families Aleyrodidae and Thripidae. In Concordia (A) and (B), in a citrus area, other "berries" and natural vegetation, Thripidae and Aphidae families were the best represented.

    The cumulative alpha diversity for the entire study period was higher in Colonia Urquiza and Chascomús, and in Entre Ríos the largest cumulative alpha diversity was found in Concordia (A). The highest values of temporary beta diversity were recorded in Entre Rios, 60% in Concordia (A) and 50% in Concordia (B). In Buenos Aires, these values varied between 39 and 50%, and Colonia Urquiza had the largest temporary beta diversity value (49.3). This indicates that in all sites there was a significant replacement of families throughout the year, which could be due to the availability and type of resource that offers the blueberry to herbivores in different phenological stages.

    Analysis of beta diversity (β) showed low values (0.27) in the comparison of San Pedro and Gobernador Castro, ie, differ little in their composition. Beta diversity (β) was higher, however, in comparing Chascomús and San Pedro (0.38), which differ more from each other. Gamma diversity (γ) as a measure of regional diversity of the communities of herbivores in the blueberry crop was 29 families in Buenos Aires and 15 in Entre Rios In relation to the functional organization, we identified 7 guilds of herbivores:

    mobile sap feeders (ASM), sessile phloem feeders (AFS), mobile mesophyll feeders (MMA), chewing and sucking surface (MChS) and external chewers (ME). There were no sessile mesophyll feeders (AMS) and internal chewers (MI). In crops of Buenos Aires and Entre Rios, the most abundant category was ASM, and in all phenological stages. The ordination analysis explained 86.4% of the variation in the abundance of guilds by sites, and 93.47% by phenological stages.

    The guild AFS was found most associated with Gobernador Castro, AMM with Colonia Urquiza, MChS to Concordia (A) and ASM to Chascomús, San Pedro and Concordia (B). The MChS guild was associated with the states of V1/R2-R3 and V1/R2, AFS with V3, ME with V2, ASM and AMM with V1/R1, R3 and R4.

    The tortricids were present in blueberry crops almost throughout the study period, and Argyrotaenia sphaleropa was the predominant species. Colonia Urquiza presented the lowest abundance and Chascomús the highest. The percentage of parasitism ranged from 10 to 50% on the sites. The larval parasitoids were endoparasitoids koinobiont. Two endoparasitoids pupal idiobiont were found, Brachymeria sp. and Conura sp., and one ectoparasitoids gregarious, Eulophidae. The Chascomús food web was 25% higher than that of Colonia Urquiza. The number of real unions, connectance and union density were higher in Chascomús and Colonia Urquiza, and had equal magnitude in San Pedro and Gobernador Castro.

    . La trama trófica de Chascomús fue 25% mayor a la de Colonia Urquiza. El número de uniones reales, la conectancia y la densidad de uniones fueron mayores en Chascomús y Colonia Urquiza, y de igual magnitud en San Pedro y Gobernador Castro.

    The low number of interactions in food webs of tortricids communities and their parasitoids reflects the simplicity of them in the blueberry crops studied.

    In Buenos Aires, the family Aphidae was present in blueberry crops of all sites, in almost all phenological stages and during the three years of study. The highest abundances were recorded in San Pedro‟s crop. Eriopis connexa was the most abundant predatory species in all sites, except in Colonia Urquiza, where Cycloneda sanguinea and Harmonia axyridis prevailed. The percentages of parasitism varied between 30 and 60%. In Entre Ríos, the number of aphids per sample was similar in the two sites and significantly different among phenological stages. The syrphids were the dominant predators and parasitism rates recorded were low, between 10 and 20%.

    In blueberry crops of Buenos Aires and Entre Ríos, individuals belonging to the families Coccidae, Pseudococcidae and Margarodidae were found. The greater abundance of Coccoidea was found in the crop of Gobernador Castro, and in the stages of V3 and V1/R1 in 2008. Icerya purchasi was present in Entre Rios and Gobernador Castro and San Pedro blueberry crops. The highest abundances were recorded in Gobernador Castro, and the percentage of parasitism was 0.80. There were no significant differences in risk of parasitism for the three density categories. There were very few individuals of R. cardinalis by sample Thripidae family was represented by three genera, Frankliniella, Thrips and Caliothrips. In Buenos Aires, they were more abundant in Gobernador Castro y San Pedro, and in Entre Rios, in Concordia (A).

    We collected 18 species of grasshoppers. The species with highest abundance was Orphulella punctata. This family is an example of tourist species of the community, because although there was in high abundance in the crops of Concordia, the diet study indicated that they were not fed the blueberry The "fruit flies", C. capitata, were present only in blueberry crops from Concordia in the 2008. The MTD index was 0.2 flies / trap / day and the MK index averaged was 21.7 ± 5.36 pupae per kilogram of fruit.

    Melolonthidae species found in blueberry crops through soil samples were Cyclocephala signaticollis, C. modesta, C. putrida, Archophileurus vervex, Anomala testaceipennis and Heterogeniates bonariensis. The ordination analysis explained 88% of the association of each genus found in light traps with the sites.

    The communities of herbivorous of blueberry crops were organized around the regional pool of species. Changes in family richness and the relative abundance of these were associated with the surrounding landscape of blueberry crop. From the point of view of functional organization, all the guilds were ectophagous. The relative importance of each guild was influenced by the abundance of the dominant family at each site, which in turn is related to the agricultural landscape and the type of resource offered at different phenological stages