Diagnóstico molecular de plagas de la dehesa y protocolos de gestión para facilitar su control biológico por el ganado

Póster presentado al I Congreso Ibérico de la Dehesa y el Montado, celebrado en Badajoz del 6 al 7 de noviembre de 2013.La investigación sobre las plagas y patógenos que reducen la producción de bellotas plantea aún numerosos retos. Presentamos los resultados de nuestros estudios con los gorgojos (coleópteros) parásitos de las bellotas. Las técnicas moleculares nos permitieron identificar larvas para las que no existen claves; a partir ahí pudimos conocer con detalle los ciclos vitales de las diferentes especies. Comprobamos que los ciervos y jabalíes depredan intensamente sobre las larvas (especialmente de las especies tempranas), pudiendo llegar a reducir las tasas de infestación de bellotas. Ahora pretendemos perfeccionar el diagnóstico molecular de plagas y patógenos aumentando la base de datos con secuencias de ADN de más especies. También investigaremos el papel del ganado como depredador de insectos plaga y dispersante de patógenos, para así desarrollar pautas de manejo ganadero que maximicen el vigor del arboladoPeer Reviewe

Unexpected consequences of a drier world: evidence that delay in late summer rains biases the population sex ratio of an insect

The complexity of animal life histories makes it difficult to predict the consequences of climate change on their populations. In this paper, we show, for the first time, that longer summer drought episodes, such as those predicted for the dry Mediterranean region under climate change, may bias insect population sex ratio. Many Mediterranean organisms, like the weevil Curculio elephas, become active again after summer drought. This insect depends on late summer rainfall to soften the soil and allow adult emergence from their underground refuges. We found that, as in many protandric species, more C. elephas females emerged later in the season. Male emergence timing was on average earlier and also more dependent on the beginning of late summer rainfall. When these rains were delayed, the observed weevil sex ratio was biased towards females. So far, the effects of global warming on animal sex ratios has been reported for temperature-dependent sex determination in reptiles. Our results show that rainfall timing can also bias the sex ratio in an insect, and highlight the need for keeping a phenological perspective to predict the consequences of climate change. We must consider not just the magnitude of the predicted changes in temperature and rainfall but also the effects of their timing.R.B. was funded by a contract of the Atracción de Talento Investigador Programme (Gobierno de Extremadura). A.M. was funded by a Juan de la Cierva contract (Ministerio de Educación). J.M.A. and M.H. were funded by the Spanish Research Council (CSIC). J.M.E. is contracted by the CREAF Institute. The work was financed by the projects: CONSOLIDER-MONTES CSD2008-00040 CONSOLIDER-MICINN, PII1C09-0256-9052 and PPII-2014-01-PJCCM ESF and CGL2008-00095/BOS MICINN.Peer Reviewe

Effectiveness of predator satiation in masting oaks is negatively affected by conspecific density

La variación en la disponibilidad de las semillas da forma a las comunidades de plantas, y se ve fuertemente afectada por la depredación de las semillas. En algunas especies de plantas, la variación temporal en la producción de semillas es especialmente alta y está sincronizada en grandes áreas, lo que se denomina "siembra en mástil". Una ventaja selectiva de este fenómeno es la saciedad de los depredadores, que supone que la siembra en mástil ayuda a las plantas a escapar de la depredación de las semillas mediante la inanición de los depredadores en los años de escasez y la saciedad en los años de mástil. Sin embargo, aunque se puede predecir que la depredación de la semilla tiene un fuerte componente espacial y depende de las densidades de las plantas, apenas se ha investigado si la eficacia de la saciedad de los depredadores en las plantas de mastelero cambia según el efecto Janzen-Connell. Estudiamos, durante un período de 8 años, la producción de semillas, los patrones espacio-temporales de depredación de semillas de gorgojos y la abundancia de gorgojos adultos en una población de encinas (Quercus ilex) que consiste en árboles intercalados en parches que cubren un continuo de densidad conespecífica. Los robles aislados sacian eficazmente a los depredadores, pero esto es superado por el aumento de la densidad de plantas conespecíficas. La falta de saciedad de los depredadores en los árboles que crecen en parches densos fue causada por la redistribución de los insectos entre las plantas que probablemente los atenuó contra la escasez de alimentos en los años de escasez, y cambió el tipo de respuesta funcional del gorgojo del tipo II en los árboles aislados al tipo III en los árboles que crecían en parches densos. Este estudio proporciona la primera evaluación empírica de la noción de que el apareamiento y la saciedad del depredador deberían ser más importantes en las poblaciones que empiezan a dominar sus comunidades, y es coherente con la observación de que el apareamiento es menos frecuente y menos intenso en bosques diversos.Variation in seed availability shapes plant communities, and is strongly affected by seed predation. In some plant species, temporal variation in seed production is especially high and synchronized over large areas, which is called ‘mast seeding’. One selective advantage of this phenomenon is predator satiation which posits that masting helps plants escape seed predation through starvation of predators in lean years, and satiation in mast years. However, even though seed predation can be predicted to have a strong spatial component and depend on plant densities, whether the effectiveness of predator satiation in masting plants changes according to the Janzen-Connell effect has been barely investigated. We studied, over an 8-year period, the seed production, the spatiotemporal patters of weevil seed predation, and the abundance of adult weevils in a holm oak (Quercus ilex) population that consists of trees interspersed at patches covering a continuum of conspecific density. Isolated oaks effectively satiate predators, but this is trumped by increasing conspecific plant density. Lack of predator satiation in trees growing in dense patches was caused by re-distribution of insects among plants that likely attenuated them against food shortage in lean years, and changed the type of weevil functional response from type II in isolated trees to type III in trees growing in dense patches. This study provides the first empirical evaluation of the notion that masting and predator satiation should be more important in populations that start to dominate their communities, and is consistent with the observation that masting is less frequent and less intense in diverse forests.• National Science Foundation (Polonia). Becas Preludio 2015/17/N/ NZ8/01565, y Etiuda no. 2015/16/T/NZ8/00018, para Michał Bogdziewicz • Foundation for Polish Science Start Scholarship. Ayuda para para Michał Bogdziewicz • Gobierno de Extremadura. Programa de Atracción de Talento Investigador. Ayuda TA13032, para Raúl Bonal Andrés • Junta de Comunidades de Castilla-La Mancha/Fondo Social Europeo. Proyectos PII1C09-0256-9052 y PPII-2014-01-P • Ministerio de Economía y Competitividad de España y la Unión Europea Fondo de Desarrollo Regional. Proyecto AGL2014-54739-R (I+D+i) • Generalitat de Catalunya. Proyecto BEEMED (SGR913)peerReviewe

Diversity in insect seed parasite guilds at large geographical scale: the roles of host specificity and spatial distance

[Aim]: Host specificity within plant-feeding insects constitutes a fascinating example of natural selection that promotes inter-specific niche segregation. If specificity is strong, composition of local plant parasitic insect guilds is largely dependent on the presence and prevalence of the preferred hosts. Alternatively, if it is weak or absent, historic and stochastic demographic processes may drive the structuring of insect communities. We assessed whether the species composition of acorn feeding insects (Curculio spp. guilds) and their genetic variation change geographically according to the local host community. [Location]: An 800 km transect across California, USA. [Methods]: We used DNA taxonomy to detect potential Curculio cryptic speciation and assessed intra-specific genetic structure among sampling sites. We monitored larval performance on different hosts, by measuring the weight of each larva upon emerging from the acorn. Our phylogenetic and spatial analyses disentangled host specificity and geographical effects on Curculio community composition and genetic structure. [Results]: DNA taxonomy revealed no specialized cryptic species. Californian Curculio spp. were sister taxa that did not segregate among Quercus species or, at a deeper taxonomic level, between red and white oaks. Curculio species turnover and intra-specific genetic differentiation increased with geographical distance among localities irrespective of local oak species composition. Moreover, larval performance did not differ among oak species or acorn sizes when controlling for the effect of the locality. [Main conclusions]: Historical processes have contributed to the structuring of acorn weevil communities across California. Trophic niche overlapped among species, indicating that ecologically similar species can co-exist. Acorn crop inter-annual variability and unpredictability in mixed oak forests may have selected against narrow specialization, and facilitated co-existence by means of an inter-specific time partitioning of the resources. Wide-scale geographical records of parasitic insects and their host plants are necessary to understand the processes underlying species diversity.This work was financed by the projects: CONSOLIDER-MONTES CSD2008-00040 MICINN, PII1C09-0256-9052JCCM and ESF, AGL2014-54739-R (MINECO), PPII-2014-01-PJCCM ESF and CGL2008-00095 ⁄ BOS (MICINN). A.M.was funded by a Juan de la Cierva contract and R.B. by acontract of the Atracción de Talento Investigador Programme (Gobierno de Extremadura TA13032). J.O. wasfunded by Severo Ochoa (SEV-2012-0262) and Ramón y Cajal (RYC-2013-12501) research fellowships.Peer reviewe

Unexpected consequences of a drier world: evidence that delay in late summer rains biases the population sex ratio of an insect

La complejidad de la historia de la vida animal hace difícil predecir las consecuencias del cambio climático sobre sus poblaciones. En este trabajo se presenta, por primera vez, que los episodios de sequía del verano, como los previstos para la región mediterránea seca en relación con el cambio climático, pueden sesgar la proporción del sexo de la población de insectos. Muchos organismos del Mediterráneo, como el gorgojo Curculio elephas, vuelve a activarse después de la sequía del verano. Este insecto depende de las lluvias del verano tardío para ablandar el suelo y permiten la emergencia del adulto, desde sus refugios subterráneos. Hemos descubierto que, como en muchas especies protándricas, como C. elephas emergieron hembras más tardíamente. La aparición de ejemplares machos dependió del promedio de distribución anterior y también del comienzo de las lluvias a finales de verano. Cuando estas lluvias se demoraron, la observación del comportamiento sexual del gorgojo se centró en las gorgojos hembras. Hasta ahora, los efectos del calentamiento global sobre las proporciones de sexo animal se han relacionado con la actividad sexual de los reptiles y los niveles de temperatura. Nuestros resultados muestran que la distribución de lluvias también puede sesgar la proporción sexual en un insecto, y resaltar la necesidad de mantener una perspectiva fenológica para predecir las consecuencias del cambio climático. Debemos considerar no sólo la magnitud de los cambios pronosticados en la temperatura y la precipitación, sino también los efectos de su distribución.The complexity of animal life histories makes it difficult to predict the consequences of climate change on their populations. In this paper, we show, for the first time, that longer summer drought episodes, such as those predicted for the dry Mediterranean region under climate change, may bias insect population sex ratio. Many Mediterranean organisms, like the weevil Curculio elephas, become active again after summer drought. This insect depends on late summer rainfall to soften the soil and allow adult emergence from their underground refuges. We found that, as in many protandric species, more C. elephas females emerged later in the season. Male emergence timing was on average earlier and also more dependent on the beginning of late summer rainfall. When these rains were delayed, the observed weevil sex ratio was biased towards females. So far, the effects of global warming on animal sex ratios has been reported for temperature-dependent sex determination in reptiles. Our results show that rainfall timing can also bias the sex ratio in an insect, and highlight the need for keeping a phenological perspective to predict the consequences of climate change. We must consider not just the magnitude of the predicted changes in temperature and rainfall but also the effects of their timing.Trabajo financiado por: Gobierno de Extremadura. Contrato del Programa de atracción de talento investigador, para Raúl Bonal Andrés Ministerio de Educación. Contrato Juan de la Cierva, para Alberto Muñoz Muñoz Consejo Superior de Investigaciones Científicas. Patrocinio para José Miguel Aparicio Munera y Marisa Hernández Gómez Ministerio de Economía, Industria y Competitividad. Proyectos CONSOLIDER-MONTES CSD2008-00040 CONSOLIDER-MICINN, PII1C09-0256-9052 y PPII PJCCM-2014-01-FSE y CGL2008-00095/BOS MICINNpeerReviewe

Effects of Longer Droughts on Holm Oak Quercus ilex L. Acorn Pests: Consequences for Infestation Rates, Seed Biomass and Embryo Survival

The effects of climate change on oaks Quercus spp. constitute a main environmental concern for the conservation of temperate forests. In this context, we assessed the consequences of longer droughts on the interactions between the holm oak Quercus ilex L. and its main acorn pests. Infested acorns were prematurely abscised before reaching their potential size. The volume of the acorns attacked by Cydia fagiglandana (Lepidoptera) was smaller than those attacked by Curculio elephas (Coleoptera); however, their weight did not differ because Curculio larvae consumed more cotyledon. For the same reason, embryo survival likelihood was not lower in Cydia acorns despite their smaller size. Delays of late summer rain reduced infestation by Curculio, as soil hardness hampers adult emergence from their underground cells. By contrast, late and scarce precipitations benefited Cydia; rainfall might hamper adult flight and eggs/L1 larvae survival. There was not a “zero-sum” effect, because the decrease of Curculio infestation rates was not fully compensated by an increase of Cydia. Under the longer droughts projected for the Mediterranean Basin, our results predict lower infestation rates and higher acorn survival likelihood. However, further studies including other environmental factors are needed to better forecast the net consequences for holm oak fitness

Looking for variable molecular markers in the chestnut gall wasp Dryocosmus kuriphilus: first comparison across genes

La rápida propagación de la avispa de la hiel de la castaña Dryocosmus kuriphilus en Europa constituye un ejemplo destacado de la reciente invasión biológica asistida por el hombre, con dramáticas pérdidas económicas. Hemos examinado por primera vez un conjunto de cinco genes nucleares y mitocondriales de D. kuriphilus recogidos en la Península Ibérica, y hemos comparado las secuencias con las disponibles en el área de distribución nativa e invasora de la especie. No encontramos variabilidad genética en Iberia en ninguno de los cinco genes, además, los tres genes comparados con otras muestras europeas tampoco mostraron variabilidad. Registramos cuatro haplotipos del citocromo b en Europa; uno era ADN mitocondrial genuino y el resto copias nucleares de ADN mitocondrial (numts), lo que subraya la necesidad de realizar análisis cuidadosos en silicio. Los numts formaban un grupo separado en el árbol genético y al menos dos de ellos podían ser ortólogos, lo que sugiere que la invasión podría haber comenzado con más de un individuo. Nuestros resultados apuntan a un bajo tamaño inicial de la población en Europa seguido de un rápido crecimiento de la población. Los futuros estudios que evalúen la expansión de esta plaga deberían incluir un gran número de sitios de muestreo y utilizar marcadores nucleares potentes (por ejemplo, polimorfismos de un solo nucleótido) para detectar la variabilidad genética.The quick spread of the chestnut gall wasp Dryocosmus kuriphilus in Europe constitutes an outstanding example of recent human-aided biological invasion with dramatic economic losses. We screened for the first time a set of five nuclear and mitochondrial genes from D. kuriphilus collected in the Iberian Peninsula, and compared the sequences with those available from the native and invasive range of the species. We found no genetic variability in Iberia in none of the five genes, moreover, the three genes compared with other European samples showed no variability either. We recorded four cytochrome b haplotypes in Europe; one was genuine mitochondrial DNA and the rest nuclear copies of mitDNA (numts), what stresses the need of careful in silico analyses. The numts formed a separate cluster in the gene tree and at least two of them might be orthologous, what suggests that the invasion might have started with more than one individual. Our results point at a low initial population size in Europe followed by a quick population growth. Future studies assessing the expansion of this pest should include a large number of sampling sites and use powerful nuclear markers (e. g. Single Nucleotide Polymorphisms) to detect genetic variability.• Junta de Extremadura. Programa de Atracción de Talento Investigador, para Raúl Bonal Andrés y Ángela Martín Cuevas • Junta de Comunidades de Castilla-La Mancha. Proyecto PPII-2014-01-P • Ministerio de Economía y Competitividad y el Fondo Europeo de Desarrollo Regional (FEDER) de la Unión Europea. Proyectos AGL2013-48017-C2-1-R, AGL2014-54739-R y AGL2014-53822-C2-1-R (I+D+i)peerReviewe

Role of seed size, phenology, oogenesis and host distribution in the specificity and genetic structure of seed weevils (Curculio spp.) in mixed forests

Synchrony between seed growth and oogenesis is suggested to largely shape trophic breadth of seed-feeding insects and ultimately to contribute to their co-existence by means of resource partitioning or in the time when infestation occurs. Here we investigated: (i) the role of seed phenology and sexual maturation of females in the host specificity of seed-feeding weevils (Curculio spp.) predating in hazel and oak mixed forests; and (ii) the consequences that trophic breadth and host distribution have in the genetic structure of the weevil populations. DNA analyses were used to establish unequivocally host specificity and to determine the population genetic structure. We identified 4 species with different specificity, namely Curculio nucum females matured earlier and infested a unique host (hazelnuts, Corylus avellana) while 3 species (Curculio venosus, Curculio glandium and Curculio elephas) predated upon the acorns of the 2 oaks (Quercus ilex and Quercus pubescens). The high specificity of C. nucum coupled with a more discontinuous distribution of hazel trees resulted in a significant genetic structure among sites. In addition, the presence of an excess of local rare haplotypes indicated that C. nucum populations went through genetic expansion after recent bottlenecks. Conversely, these effects were not observed in the more generalist Curculio glandium predating upon oaks. Ultimately, co-existence of weevil species in this multi-host-parasite system is influenced by both resource and time partitioning. To what extent the restriction in gene flow among C. nucum populations may have negative consequences for their persistence in a time of increasing disturbances (e.g. drought in Mediterranean areas) deserves further research

The Moran effect and environmental vetoes : phenological synchrony and drought drive seed production in a Mediterranean oak

Unidad de excelencia María de Maeztu MdM-2015-0552Masting is the highly variable production of synchronized seed crops, and is a common reproductive strategy in plants. Weather has long been recognized as centrally involved in driving seed production in masting plants. However, the theory behind mechanisms connecting weather and seeding variation has only recently been developed, and still lacks empirical evaluation. We used 12-year long seed production data for 255 holm oaks (Quercus ilex), as well as airborne pollen and meteorological data, and tested whether masting is driven by environmental constraints: phenological synchrony and associated pollination efficiency, and drought-related acorn abscission. We found that warm springs resulted in short pollen seasons, and length of the pollen seasons was negatively related to acorn production, supporting the phenological synchrony hypothesis. Furthermore, the relationship between phenological synchrony and acorn production was modulated by spring drought, and effects of environmental vetoes on seed production were dependent on last year's environmental constraint, implying passive resource storage. Both vetoes affected among-tree synchrony in seed production. Finally, precipitation preceding acorn maturation was positively related to seed production, mitigating apparent resource depletion following high crop production in the previous year. These results provide new insights into mechanisms beyond widely reported weather and seed production correlations

Trees increase ant species richness and change community composition in Iberian Oak savannahs

Iberian man-made oak savannahs (so called dehesas) are traditional silvopastoral systems with a high natural value. Scattered trees provide shelter and additional food to livestock (cattle in our study sites), which also makes possible for animals depending on trees in a grass-dominated landscape to be present. We compared dehesas with nearby treeless grasslands to assess the effects of oaks on ant communities. Formica subrufa, a species associated with decayed wood, was by far the most abundant species, especially in savannahs. Taxa specialized in warm habitats were the most common both in dehesas and grasslands, as expected in areas with a Mediterranean climate. Within dehesas, the number of species was higher below oak canopies than outside tree cover. Compared to treeless grasslands, the presence of oaks resulted in a higher species richness of aphid-herding and predator ants, probably because trees offer shelter and resources to predators. The presence of oaks changed also the species composition, which differed between grasslands and dehesas. In self-standing scattered oaks, ant communities did not differ between the trunks and soil below canopies. These results stress the conservation value of trees in dehesas; within grasslands, they offer an additional microhabitat for species that would otherwise be scarce or absent