Browsing by Author "Grez, Audrey A."

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    Apparent niche differences between native and exotic lady beetles
    (2023) Croy, Jordan R.; Zaviezo, Tania; Crossley, Michael S.; Smith, Olivia M.; Snyder, William E.; Grez, Audrey A.
    Generalist predators can enhance biological control by filling unique niches and complementing other natural enemies, or disrupt it by preying upon other predators and parasitoids, complicating their net value for biological control. We searched for evidence of complementarity and/or interference between native (primarily Eriopis chilensis and E. eschscholtzi) and exotic (primarily Hippodamia variegata and Harmonia axyridis) lady beetles attacking aphids in alfalfa (Medicago sativa) fields near Santiago, Chile. Across 60 fields and three growing seasons, exotic lady beetle adults and larvae reached peak abundance relatively earlier in the growing season than the natives. Furthermore, exotic lady beetle peaks aligned more closely with aphid peak abundance than did native lady beetle peaks. Abundances of native lady beetle adults and larvae were weakly positively correlated with those of exotics, and peak aphid densities were generally lowest in fields where native and non-native lady beetle adults were similarly abundant. Therefore, we did not see evidence of strong interference between exotics and natives. Natural-agricultural habitat edges reduced native, but not exotic, larval lady beetle lag behind aphid peaks and was associated with greater lady beetle and lower aphid densities. Moreover, farms embedded in landscapes with greater natural habitat cover supported more exotic, but not native, lady beetles, and increased the lag between larval lady beetles and aphids for natives but not exotics. These findings support the idea that farms embedded within mosaics of natural and agricultural habitats may provide greater interaction potential between native lady beetles and aphid pests on farms as they move across the landscape, leading to greater top -down control. In contrast, exotic lady beetle lags were unaffected by landscape composition or configuration, but their greater densities in farms surrounded by more natural habitats might reflect a 'concentration effect' whereby exotic lady beetle abundance becomes concentrated in the agricultural habitats that they prefer. Our findings suggest that some lady beetles introduced for biocontrol may be better adapted to intensively managed habitats than natives, possibly leading to spatiotemporal complementarity between native and exotic lady beetles.
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    Citizen Science and Phytosanitary Surveillance Systems Are Complementary Tools to Follow the Invasion of Harmonia axyridis
    (2023) Grez, Audrey A.; Zaviezo Palacios, Tania; Orellana, Ignacio; Pino, Luna; Roy, Helen E.; Torres, Fernando; Rebolledo, Claudia
    Citizen science is a valuable tool for early detection, distribution, and spread of invasive alien species (IAS). Nevertheless, citizen science initiatives have several potential biases and may be complemented with long-term structured monitoring schemes. We analyzed the spatial-temporal dynamics of the invasion of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in Chile, based upon two citizen sciences databases (WEB and INAT) and one structured monitoring (SAG). We collected 8638 H. axyridis occurrences between 2009 and 2020. WEB had a higher number of records than SAG and INAT, and in all databases, the number of records has increased over time. The three databases showed that the invasion started in central Chile and then spread toward the north and south. The WEB and SAG recorded occurrences in the extreme north and south, whereas INAT concentrated all the occurrences in a more limited area, included in WEB and SAG. Both citizen science initiatives concentrated their records in areas of high human populations whereas SAG records had a more even distribution across regions. At 2020, WEB accounted for 55%, SAG 54%, and INAT 8% of the total area accumulated with H. axyridis, with only 16% of area shared among databases. WEB and INAT obtained most of their records in urban and industrial land cover types, while SAG records were more evenly represented in different land cover types. Our results confirm that combined methods, including citizen science initiatives, national surveillance system, and localized samplings, complement each other in providing knowledge to understand the patterns, processes, and consequences of this invasion.
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    Defining corridors for movement of multiple species in a forest-plantation landscape
    (2020) Pliscoff, Patricio; Simonetti, Javier A.; Grez, Audrey A.; Vergara, Pablo M.; Barahona-Segovia, Rodrigo M.
    Forestry plantations of Pinus radiata, managed through clearcutting method, would offer resistance to the movement of native fauna among remnants of native forest. In this study, we evaluate the possibilities of establishing connectivity corridors for native fauna in a forest landscape dominated by P. radiata, focusing on seven species with some level of specialisation in the use of different land covers and that exhibit different movement strategies. We sampled presences and abundances using several types of sampling to determine the abundance and crossing edge probabilities for the ground-dwelling beetle Ceroglossus chilensis; the mesocarnivores Conepatus chinga, Lycalopex culpaeus and Leopardus guigna; the terrestrial frogs Eupsophus septentrionalis and Pleuroderma thaul, and the understory bird Pteroptochos castaneus. We use species distribution modelling and circuit theory to calculate connectivity for each species. Finally, a spatial priorization approach was applied to obtain two scenarios of least-cost corridors. The results show that species with more specific requirements such as L. guigna, P. castaneus, P. thaul and E. septentrionalis, are unlikely to move through clear cuttings and young plantations, but their movement is possible through adult pine plantations with understory. For species that are habitat generalists such as C. chinga and L. culpaeus plantations were suitable for movement. The management of forest plantations should use multi-taxa assessments in the design of biological corridors that allow the connection of forest fragments. (C) 2020 The Authors. Published by Elsevier B.V.
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    Effects of habitat loss and fragmentation on the abundance and species richness of aphidophagous beetles and aphids in experimental alfalfa landscapes
    (CZECH ACAD SCI, INST ENTOMOLOGY, 2008) Grez, Audrey A.; Zaviezo, Tania; Diaz, Sandra; Camousseigt, Bernardino; Cortés Hinojosa, Galaxia Andrea
    In agro-ecosystems, habitat loss and fragmentation may alter the assemblage of aphidophagous insects, Such as foliar-foraging (coccinellids) and ground-foraging predators (carabids), potentially affecting intraguild interactions. We evaluated how habitat loss (0, 55 and 84%), fragmentation (1, 4 and 16 fragments) and their combination affected the abundance and species richness of coccinellids and carabids, and aphid abundance, both in the short-term (summer: December to February) and over a longer time span (autumn: March to May), when different demographic mechanisms may participate. We created four types of 30 x 30 in patches (landscapes) in which alfalfa was grown: Control (IF - 0%, 30 x 30 ill patch of alfalfa with no fragmentation or habitat loss), 4F - 55% (4 alfalfa fragments, with 55% total habitat loss), 4F - 84% (4 alfalfa fragments, with 84% total habitat loss), and 16F - 84% (16 alfalfa fragments, with 84% total habitat loss). Each landscape type was replicated five times. Insects were sampled by sweep-netting and pitfall traps, from December (summer) to May (autumn). Total abundance and species richness of carabids, in the short-term, was highest in the 1 6F - 84% landscapes. Total abundance of adult coccinellids was similar among landscapes, but at the species level Hyperaspis sphaeridioides, in the short-term, and Adalia bipunctata, in the long-term, had their highest densities in fragments within landscapes with high habitat loss (84%), independently of habitat fragmentation. Species richness in the long-term was higher in the landscapes with 84% habitat loss. Among aphids, in the long term Aphis craccivora was less abundant in landscapes with high habitat loss and fragmentation (16-84%), while Therioaphis trifolii showed the opposite trend. These results suggest that habitat loss and fragmentation may increase the density and diversity of aphidophagous insects, while their effects oil aphids are more variable.
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    Effects of habitat loss, habitat fragmentation, and isolation on the density, species richness, and distribution of ladybeetles in manipulated alfalfa landscapes
    (WILEY, 2006) Zaviezo, Tania; Grez, Audrey A.; Estades, Cristian F.; Perez, Astrid
    1. Habitat loss and fragmentation are the main causes of changes in the distribution and abundance of organisms, and are usually considered to negatively affect the abundance and species richness of organisms in a landscape. Nevertheless, habitat loss and fragmentation have often been confused, and the reported negative effects may only be the result of habitat loss alone, with habitat fragmentation having nil or even positive effects on abundance and species richness.
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    Foliar and ground-foraging predators of aphids associated with alfalfa crops in Chile: Are they good or bad partners?
    (TAYLOR & FRANCIS LTD, 2007) Grez, Audrey A.; Rivera, Pamela; Zaviez, Tania
    Carabids and coccinellids are the most abundant aphid predators in alfalfa. Depending on the amount of prey consumed, the impact of their combined effect can be additive, antagonistic, or synergistic. Laboratory trials demonstrated that a higher proportion of Aphis craccivora Koch dropped from the alfalfa plants in the presence of coccinellids, and that the interaction between these predators was additive or synergistic, but never antagonistic, suggesting that they might be good partners in controlling aphids.
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    Harmonia axyridis in Chile : a new threat.
    (2010) Grez, Audrey A.; Zaviezo Palacios, Tania; González, Guillermo; Rothmann Toro, Sergio Alejandro
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    Migration of coccinellids to alfalfa fields with varying adjacent vegetation in Central Chile
    (2010) Grez, Audrey A.; Torres, Constanza; Zaviezo, Tania; Lavandero, Blas; Ramirez, Marcelo
    A. A. Grez, C. Torres, T. Zaviezo, B. Lavandero, and M. Ramirez. Migration of coccinellids to alfalfa fields with varying adjacent vegetation in Central Chile. 2010. Cien. Inv. Agr. 37(2): 111-121. Permanent and permeable edges, where natural enemies can feed, overwinter or easily cross over, should enhance the early arrival of these predators to crops. We evaluated the abundance and species richness of coccinellids migrating to alfalfa fields adjacent to Eucalyptus, a mix of false acacia, blackberries and poplar (F-B-P), vineyards, corn and annual vegetables. From September 2007 to May 2008, we captured coccinellids in three sticky traps (2.64 m(2)) placed at the borders between alfalfa fields and adjacent vegetation. We also estimated the abundance of aphid populations in the alfalfa fields, by counting the number of individuals per alfalfa stem in spring, summer and autumn. We collected 90,396 coccinellids from 14 species. Neither total abundance nor species richness of coccinellids was significantly affected by adjacent vegetation, but Adalia deficiens, Psyllobora picta and Cycloneda sanguinea were more abundant in alfalfa adjacent to Eucalyptus and F-B-P, meanwhile Olla v-nigrum next to annual crops and Hyperaspis sphaeridioides next to vineyards. Edge height and orientation explained 94% of the variance in species abundance. Particularly, P picta and O. v-nigrum were positively and negatively influenced by border height, respectively. Hyperaspis sphaeridioides was negatively affected by northern exposure and none of the species was affected by edge permeability. Aphids were less abundant in alfalfa fields adjacent to F-B-P, especially in spring. These results show that most species of coccinellids were not affected by the composition of crop edges, although tall permanent edges may enhance the arrival of particular coccinellid species to alfalfa fields.
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    Migration of coccinellids to alfalfa fields with varying adjacent vegetation in Central Chile.
    (2010) Grez, Audrey A.; Torres, Constanza; Zaviezo, Tania; Lavandero, Blas; Ramírez, Marcelo
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    Natural enemy communities of aphids in alfalfa fields assessed through video recordings of sentinel cards in scenarios of contrasting aphid abundance
    (2024) Grez, Audrey A.; Zaviezo, Tania; Molina, Gabriela
    The first step to better understand the relationship between natural enemy communities and pest control is to know which, when, and how frequently different natural enemies interact with their prey. In alfalfa fields of central Chile, aphids are the most common pests and are consumed by predators such as coccinellids, syrphids, and spiders. In this study, through video recording, we analyzed how natural enemy communities visiting aphid sentinel cards vary between scenarios of low and high abundance of aphids in alfalfa in spring. On 15 occasions, during the day, we monitored the natural enemies visiting cards with sentinel aphids (60 cards per field; total 900) located in fields with high (n = 6) and low (n = 9) aphid abundance. We also analyzed whether the abundance of coccinellid species visiting sentinel cards was related to their abundance in each field. In 750 h of video recording, we found 2749 natural enemies visiting the sentinel cards; 86.2% of them were coccinellids of five species. Total natural enemies and coccinellid visits were three times higher in low than in high aphid abundance scenarios. In contrast, the species richness and diversity of natural enemies and coccinellids visiting cards did not differ between aphid scenarios. The abundance of coccinellids in the field was positively associated with the abundance of coccinellids visiting cards, for the three most abundant species. Our study shows that video recording is useful for identifying changes in the communities of natural enemies of aphids in alfalfa, providing important new insights into trophic interactions in field situations.
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    Predators and parasitoids of the harlequin ladybird, harmonia axyridis, in its native range and invaded areas
    (2018) Ceryngier, Piotr; Nedvěd, Oldřich; Grez, Audrey A.; Riddick, Eric W.; Roy, Helen E.; San Martin, Gilles; Steenberg, Tove; Veselý, Petr; Zaviezo Palacios, Tania; Zúñiga Reinoso, Álvaro; Haelewaters, Danny
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    Rapid spread of Harmonia axyridis in Chile and its effects on local coccinellid biodiversity
    (2016) Grez, Audrey A.; Zaviezo Palacios, Tania; Roy, Helen E.; Brown, Peter M. J.; Bizama, Gustavo
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    The invasive coccinellid Harmonia axyridis (Coleoptera: Coccinellidae) is a less suitable host for parasitism than resident species
    (2020) Romero, Violeta; Zaviezo, Tania; Grez, Audrey A.
    Harmonia axyridis (Pallas) has invaded most continents in the world, including South America. In Chile, it became invasive after 2010, turning into a dominant species in coccinellid guilds in alfalfa crops, where it coexists with the introduced species Hippodamia variegata (Goeze) and the native species Eriopis chilensis Hofmann, the populations of which declined after the invasion of H. axyridis. One of the mechanisms attributed to the success of invasive species is the enemy release hypothesis (ERH), which predicts that natural enemies will have a lesser impact on the invasive species in the newly invaded areas than on resident species. Dinocampus coccinellae (Hymenoptera: Braconidae) is a cosmopolitan parasitoid of coccinellids, which vary in their suitability to parasitism according to species and location. The present study evaluated whether H. axyridis is a less suitable host than H. variegata and E. chilensis for D. coccinellae by assessing each step in the parasitism process, from oviposition to adult emergence in field and laboratory conditions. In the field, successful parasitism in H. axyridis (7%) was significantly lower than in H. variegata (33%) and E. chilensis (36%). H. axyridis was also the only species in which failed parasitoid larval development was greater than successful parasitism (adult emergence). In the laboratory, D. coccinellae never successfully oviposited in H. axyridis, while it did in the other two species. These results suggest that in Chile, H. axyridis is a less suitable host than the resident species for D. coccinellae. This mechanism, among others, may explain the dominance of this species in this early stage of invasion.