Biotic interactions are expected to be impacted by rising temperatures due to climate change, particularly in climate‐threatened ecosystems such as the tropical montane cloud forest (TMCF). In ...assisted migration plantings, novel interactions between previously non‐overlapping species may emerge while other interactions may disappear. However, these processes require study. Herbivory is particularly important in tree early stages, and can vary with elevation and plant species traits. We assessed whether leaf herbivory occurs in translocated tree saplings and varies with elevation, and whether herbivory affects sapling growth in six shade‐tolerant TMCF tree species translocated to seven enrichment plantings along an elevation gradient (1,250–2,500 m a.s.l.), including sites located above the reported distributional limit of the species, in eastern Mexico. Given the conservative strategy of the studied plant species, limited damage was expected. Since insects are ectothermic, we expected decreasing herbivory pressure with increased elevation. After 4 years, sapling survival was high (77.9–92.1%). Moderate herbivory was recorded in all species and at all sites (1.0–6.6%), with no effect on growth in any of the species. Herbivory decreased with elevation in three species and was unaffected in the other three. The results indicate that plant‐herbivore interactions can continue at new locations; however, the contribution of generalist and specialist insect herbivores requires further study. The reduced herbivory at higher elevation in some species supports the expected trend, which could represent an advantage for upward assisted migration of endangered TMCF tree species in restoration plantings to mitigate climate change effects.
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Abstract Agroecosystem simplification for greater food production has led to the loss of ecosystem services such as pest control by predators. Plant diversification has shown excellent potential to ...improve the diversity of crop predators such as spiders. However, in agroecosystems with frequent disturbances such as annual crops, it is unknown whether the effect of plant diversification on spiders depends on the surrounding landscape and the stages of the agricultural cycle (i.e., periods with differences in vegetation, weather and agricultural practices). Here, we evaluated the effect and interaction of local management (plant diversification), landscape (forest areas) and agricultural cycle on the richness and abundance from the main spider guilds of a maize polyculture in Mexico. We found that greater crop diversification (i.e., addition of legumes and leafy plants) caused a greater abundance of ground‐hunting spiders. We also show that a larger area of forest around the crop favours a greater richness and abundance of ground‐ and vegetation‐hunting spiders. We found that each stage of the agricultural cycle had a different spider richness and abundance, ground hunters were more common at the beginning of the agricultural cycle, while vegetation hunters and web‐builders were more common during the peak developmental stages of the crops. Our findings support the idea that to foster functionally diverse spider communities that potentially enhance natural pest control, we must jointly manage plant elements within the crop, in the surrounding landscape, considering the high dynamics of spider communities throughout the agricultural cycle.
Resumen La simplificación de los agroecosistemas para una mayor producción de alimentos ha llevado a la pérdida de servicios ecosistémicos como el control de plagas por parte de los depredadores. La diversificación de plantas ha demostrado un excelente potencial para mejorar la diversidad de depredadores de los cultivos como las arañas. Sin embargo, en agroecosistemas con perturbaciones frecuentes, como los cultivos anuales, se desconoce si el efecto de la diversificación de plantas sobre las arañas depende del paisaje circundante y de las etapas del ciclo agrícola (es decir, períodos con diferencias en vegetación, clima y prácticas agrícolas). Aquí, evaluamos el efecto y la interacción del manejo local (diversificación de plantas), el paisaje (áreas forestales) y el ciclo agrícola sobre la riqueza y abundancia de los principales gremios de arañas de un policultivo de maíz en México. Descubrimos que una mayor diversificación de cultivos (es decir, la adición de leguminosas y plantas hojosas) provocó una mayor abundancia de arañas cazadoras del suelo . También demostramos que una mayor superficie de bosque alrededor del cultivo favorece una mayor riqueza y abundancia de arañas cazadoras del suelo y cazadoras de la vegetación . Descubrimos que cada etapa del ciclo agrícola tenía una riqueza y abundancia de arañas diferente; las cazadoras del suelo eran más comunes al comienzo del ciclo agrícola, mientras que las cazadoras de la vegetación y las constructoras de telarañas eran más comunes durante las etapas de máximo desarrollo de los cultivos. Nuestros hallazgos respaldan la idea de que para fomentar comunidades de arañas funcionalmente diversas que potencialmente mejoren el control natural de plagas, debemos gestionar conjuntamente los elementos vegetales dentro del cultivo, en el paisaje circundante y considerando la alta dinámica de las comunidades de arañas a lo largo del ciclo agrícola.
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The current global pollinator crisis highlights the need to investigate the diversity and distribution of ecologically and socially relevant taxa such as tropical stingless bees. We analyzed the ...diversity and composition of stingless bee (Meliponini) communities at a regional scale in west‐central Mexico using an extensive direct search along an altitudinal gradient encompassing different climate and vegetation types. Our hypothesis was that meliponine bee diversity would be greater in tropical warmer. We found a total of 14 meliponine bee species, including two new records for the region. We identified three types of bee assemblages: one in hot lowland climates with tropical dry forest vegetation, one in temperate highland climates with mixed oak‐pine forest vegetation, and one in the warm ecotone with mixed subdeciduous forest vegetation between the hot and temperate zones. As expected, the lowland assemblage in the tropical dry forest vegetation had the greatest diversity (11 species). In the warm ecotone, meliponine species from temperate highlands and hot lowland habitats converged; this region should therefore be considered a high conservation priority area. Fifty percent of the meliponine bees found are endemic and have a very low incidence, suggesting that their populations may be endangered. Given the extensive and ongoing change of land use to avocado plantations in the warm ecotone and temperate highlands with mixed oak‐pine forest vegetation cover, specific conservation plans should be generated to conserve the natural ecosystems and this important native pollinator group.
in Spanish is available with online material.
Resumen
La actual crisis mundial de los polinizadores enfatiza la necesidad de investigar la diversidad y distribución de taxones relevantes desde el punto de vista ecológico y social. Analizamos la diversidad y composición de las comunidades de abejas sin aguijón (Meliponini) a escala regional en el centro‐oeste de México. Se realizó una búsqueda directa en un gradiente altitudinal considerando clima y tipos de vegetación. Nuestra hipótesis era que la comunidad de meliponinos sería más diversa hacia las regiones más cálidas. Encontramos un total de 14 especies de meliponinos, incluidos dos nuevos registros para la región. Identificamos tres tipos de ensamblajes de abejas: uno en tierras bajas de clima caliente y árido, uno en tierras altas de clima templado y uno en el ecotóno cálido entre zonas calientes y templadas. La zona de tierras bajas de clima caliente y árido concentró más especies (11 meliponinos) concordando con la hipótesis planteada. En el ecotono cálido convergen especies de hábitat templado de tierras altas y de tierras bajas de clima caliente, sugerimos debe considerarse área prioritaria de conservación. El cincuenta por ciento de meliponinos encontrados en este estudio son endémicos y tienen una incidencia muy baja, lo que sugiere que sus poblaciones pueden estar en peligro. Dado el extenso y continuo cambio de uso de la tierra a plantaciones de aguacate en el ecotono cálido y las tierras altas templadas, se deben generar planes de manejo específicos para conservar los ecosistemas naturales y este importante grupo de polinizadores nativos.
We found a total of 14 stingless bee species, including two new records for the region. We identified three types of bee assemblages: one in hot lowland climates with tropical dry forest vegetation, one in temperate highland climates with mixed oak‐pine forest vegetation, and one in the warm ecotone with mixed subdeciduous forest vegetation between the hot and temperate zones. The habitats of meliponine bee in temperate highland and warm ecotone require urgent actions to safeguard the conservation of their natural ecosystems and of this important group of native pollinators.
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1. Ecological interaction networks constantly reorganize as interspecific interactions change across successional stages and environmental gradients. This reorganization can also be associated with ...the extent to which species change their preference for types of niches available in their local sites. Despite the pervasiveness of these interaction changes, previous studies have revealed that network reorganizations have a minimal or insignificant effect on global descriptors of network architecture, such as connectance, modularity and nestedness. However, little is known about whether these reorganizations may have an effect on community dynamics and composition. 2. To answer the question above, we study the multi-year dynamics and reorganization of plant-herbivore interaction networks across secondary successional stages of a tropical dry forest. We develop new quantitative tools based on a structural stability approach to estimate the potential impact of network reorganization on species persistence. Then, we investigate whether this impact can explain the likelihood of persistence of herbivore species in the observed communities. 3. We find that resident (early-arriving) herbivore species increase their likelihood of persistence across time and successional stages. Importantly, we demonstrate that, in late successional stages, the reorganization of interactions among resident species has a strong inhibitory effect on the likelihood of persistence of colonizing (late-arriving) herbivores. 4. These findings support earlier predictions suggesting that, in mature communities, changes of species interactions can act as community-control mechanisms (also known as priority effects). Furthermore, our results illustrate that the dynamics and composition of ecological communities cannot be fully understood without attention to their reorganization processes, despite the invariability of global network properties.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
Dung beetle activity causes many changes in the soil when they remove feces from the surface. In temperate grasslands and in greenhouse experiments, these changes have been found to positively affect ...established plants, but information about these effects under natural conditions in tropical forests is practically nonexistent. In a tropical rainforest (Los Tuxtlas, Mexico), we carried out field experiments with seedlings of six tree species (Brosimum alicastrum, Calophyllum brasiliense, Cymbopetalum baillonii, Diospyros digyna, Omphalea oleifera, and Poulsenia armata), to assess whether feces burial by dung beetles had any positive effect on them. We estimated foliar nitrogen and phosphorus, seedling survival, growth and resource allocation, under three treatment levels: (a) feces added and beetles active, (b) feces added and beetles excluded, and (c) no feces added (and consequently no beetles active). We analyzed data at two levels: community (all plant species together) and individual species. Dung beetle activity did not increase the concentration of foliar nutrients or seedling performance (survival, growth); in one species, it modified resource allocation. At the community level and for two species, dung beetle activity decreased the probability of seedlings growing in height. Our study provides evidence on how extrapolating the effects of dung beetle activity from other study systems into tropical forests can be problematic. More studies will be needed before we can have a clearer idea of the effects that feces burial by dung beetles have on established plants in tropical forests.
in Spanish is available with online material.
Resumen
La actividad de los escarabajos coprófagos provoca muchos cambios en el suelo cuando remueven heces de la superficie. En pastizales templados y en experimentos de invernadero se ha encontrado que estos cambios tienen efectos positivos en plantas establecidas, pero la información sobre estos efectos bajo condiciones naturales en bosques tropicales es prácticamente inexistente. En un bosque tropical (Los Tuxtlas, México) realizamos experimentos de campo con plántulas de seis especies arbóreas (Brosimum alicastrum, Calophyllum brasiliense, Cymbopetalum baillonii, Diospyros digyna, Omphalea oleifera y Poulsenia armata), para evaluar si el enterramiento de heces por escarabajos tenía algún efecto positivo sobre ellas. Estimamos el nitrógeno y fósforo foliar, supervivencia de plántulas, crecimiento y asignación de recursos, bajo tres niveles del tratamiento: (a) heces adicionadas y actividad de escarabajos, (b) heces adicionadas y escarabajos excluidos, y (c) sin heces adicionadas (y consecuentemente sin escarabajos). Analizamos los datos a dos niveles: comunitario (todas las especies de plantas juntas) y especies individuales. La actividad de los escarabajos coprófagos no incrementó la concentración de los nutrientes foliares o el desempeño de las plántulas (supervivencia, crecimiento); en una especie modificó la asignación de recursos. A nivel comunitario y para dos especies, la actividad de los escarabajos coprófagos redujo la probabilidad de crecimiento en altura de las plántulas. Nuestro estudio proporciona evidencia sobre cómo extrapolar los efectos de la actividad de los escarabajos coprófagos, a partir de otros sistemas de estudio a los bosques tropicales, puede ser problemático. Más estudios serán necesarios antes de que podamos tener una idea más clara de los efectos que el enterramiento de heces por escarabajos coprófagos tiene sobre plantas establecidas en bosques tropicales.
We carried out field experiments with seedlings of six rainforest tree species, which were subject to: (a) feces and access to dung beetles, (b) feces and dung beetles excluded, and (c) no feces or beetles. Dung burial by beetles did not increase foliar nutrient concentrations, seedling survival, or growth in any of the species. We reach two main conclusions: (i) Results from other systems (e.g., greenhouse experiments, studies in temperate grasslands) cannot be extrapolated to tropical forests; (ii) Much remains to be investigated about the effects that dung beetle activity may have on tropical forest soils, and what the consequences might be for plants and other ecosystem components.
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Ecological restoration in tropical dry forests urgently needs to incorporate experimental evidence to increase effectiveness. The main barriers for tree establishment are adverse microenvironmental ...conditions and competition with exotic grasses. Therefore, management should address such barriers in order to enhance tree performance. We evaluated the effect of plastic mulching, grass removal, and no management on survival after 2 months and stem volume and canopy size after 2 years and integrated response index (IRI) in plantings of 11 native tree species with different growth rates in pastures near the tropical dry forest of Chamela, Mexico. Results revealed that: (1) initial seedling mortality was minimal in all treatments (8%) and lowest under no management (2%); (2) plastic mulching, but not grass removal, leads to increased size for most species, irrespective of their growth rank; (3) a trade‐off between initial plant survival and size after 2 years occurred due to plastic mulching; and (4) most species showed similar values of the IRI because of high survival, stem volume, or canopy cover. Grass removal decreased early survival of all species and increased stem volume only for one slow‐growing species. The use of plastic mulching increased stem volume for slow‐growing species, whereas fast‐growing species developed larger canopies with that treatment. Effects of grass removal and mulching seem to be very species‐specific and not dependent in growth rank of species, although overall mulching seems to provide better conditions for seedling performance than grass removal alone.
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Forest succession can influence herbivore communities through changes in host availability, plant quality, microclimate, canopy structure complexity and predator abundance. It is not well known, ...however, if such influence is constant across years. Caterpillars have been reported to be particularly susceptible to changes in plant community composition across forest succession, as most species are specialists and rely on the presence of their hosts. Nevertheless, in the case of tropical dry forests, plant species have less defined successional boundaries than tropical wet forests, and hence herbivore communities should be able to persist across different successional stages. To test this prediction, caterpillar communities were surveyed during eight consecutive years in a tropical dry forest in four replicated successional stages in Chamela, Jalisco and Mexico. Lepidopteran species richness and diversity were equivalent in mature forests and early successional stages, but a distinctive caterpillar community was found for the recently abandoned pastures. Species composition tended to converge among all four successional stages during the span of eight years. Overall, our results highlight the importance of both primary and secondary forest for the conservation of caterpillar biodiversity at a landscape level. We also highlight the relevance of long‐term studies when assessing the influence of forest succession to account for across year variation in species interactions and climatic factors.
in French is available with online material.
Resumen
La sucesión vegetal puede influenciar las comunidades de herbívoros a través de la disponibilidad de plantas hospederas, la calidad de las plantas, el microclima, la complejidad estructural del dosel o la abundancia de depredadores. Sin embargo, se desconoce si esta influencia es constante a través de los años. Se ha descrito que las larvas de lepidópteros son particularmente susceptibles a cambios en la composición de la comunidad de plantas a lo largo de la sucesión vegetal, dado que la mayoría de las especies son especialistas y dependen de la presencia de su planta hospedera. En el caso de los bosques tropicales caducifolios, las especies vegetales no tienen un estatus sucesional tan definido como las plantas de los bosques tropicales húmedos, y por lo tanto es probable que las comunidades de herbívoros persistan a través de diferentes estadios sucesionales. Para poner a prueba esta predicción, se evaluó la comunidad de orugas en cuatro estadios sucesionales del bosque tropical caducifolio en Chamela, Jalisco, México, durante ocho años consecutivos. La riqueza y diversidad de lepidópteros fueron equivalentes entre el bosque maduro y los estadios sucesionales tempranos, mientras que la composición de la comunidad fue distinta en el estadio inicial. La composición de especies tendió a convergir entre estadios sucesionales a través de los ocho años de estudio. En conjunto, nuestros resultados resaltan la importancia de los bosques primarios y secundarios para la conservación de lepidópteros a nivel de paisaje. Enfatizamos la importancia de los estudios de largo plazo para evaluar la influencia de la sucesión vegetal, y así tomar en cuenta la variación interanual en la interacción entre especies y los factores climáticos.
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Soil microorganisms play a key role in plant growth and health, and honey bees depend on plant pollen and nectar for their nutrition. Despite this clear above- and belowground connection, our ...knowledge about bee-plant-soil interactions is yet limited. Also, how these multitrophic interactions are affected by agricultural practices like pesticide applications is not well understood. Here we investigated possible non-target effects of soil application of the fungicide Benomyl on bee-plant-soil interactions in a greenhouse experiment with vetch (Vicia sativa L.). When plants were flowering honey bees were confined to their respective experimental soil treatments (untreated control, Benomyl and soil disinfection) in tents made from anti-insect mesh and micro-hives for foraging. At harvest, results showed that Benomyl and soil disinfection strongly affected key root and soil microorganisms essential for plant nutrition, such as mycorrhiza and rhizobia, and Gram-positive and Gram-negative bacteria, which coincided with phenotypic alterations in plant development and subsequently significant effects on honey bee nutrition and health, and finally honey production. In conclusion, our results show that soil application of the fungicide Benomyl strongly impact on bee-plant-soil multitrophic interactions, calling for further investigation on non-target effect of pesticides including multitrophic studies when evaluating environmental impacts of pesticides.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
1 The importance of tolerance to herbivory for plant survival has long been recognized, but capacity for regrowth following recurrent defoliation has rarely been studied. 2 A glasshouse experiment ...was conducted with eight grassland species. We chose both species favoured under herbivory (increasers) and those that become scarce (decreasers) and manipulated the ontogeny of the plant when first clipped, as well as frequency (up to eight times) and intensity of clipping. 3 Plant survival was high (88%) but both frequency and intensity of clipping increased plant mortality in all species investigated (P < 0.05). Immature plants showed the highest mortality (15.9%). 4 Plant biomass mirrored mortality with immature plants again the most affected. As expected, control plants were largest and plants experiencing 100% biomass removal smallest. Clipping frequency was also significant, but the effect was not linear and plants that were clipped more than twice were more dramatically affected. 5 Biomass compensation showed species-specific responses that were significantly related to an a priori definition of species status in the grassland: increaser species had significantly higher compensation ability after recurrent defoliation than decreaser species. 6 Tolerance to herbivory has been viewed as a marginal strategy for plant survival, but our results suggest that it plays an important role in explaining abundance and distribution of plant species in environments with recurrent defoliation. 7 Plants do not always respond linearly to environmental pressures (such as repeated defoliation) and cannot therefore be predicted by studies considering only the lower end of the possible intensities. Understanding the effects of environmental pressures on plant fitness requires the study of a broader range of intensities, at different ontogenic stages and consideration of possible response thresholds.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
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