One of the greatest current challenges to human society is ensuring adequate food production and security for a rapidly growing population under changing climatic conditions. Climate change, and ...specifically rising temperatures, will alter the suitability of areas for specific crops and cultivation systems. In order to maintain yields, farmers may be forced to change cultivation practices, the timing of cultivation, or even the type of crops grown. Alternatively, farmers can change the location where crops are cultivated (e.g., to higher elevations) to track suitable climates (in which case the plants will have to grow in different soils), as cultivated plants will otherwise have to tolerate warmer temperatures and possibly face novel enemies. We simulated these two last possible scenarios (for temperature increases of 1.3°C and 2.6°C) in the Peruvian Andes through a field experiment in which several traditionally grown varieties of potato and maize were planted at different elevations (and thus temperatures) using either the local soil or soil translocated from higher elevations. Maize production declined by 21%–29% in response to new soil conditions. The production of maize and potatoes declined by >87% when plants were grown under warmer temperatures, mainly as a result of the greater incidence of novel pests. Crop quality and value also declined under simulated migration and warming scenarios. We estimated that local farmers may experience severe economic losses of up to 2,300 US$ ha−1 yr−1. These findings reveal that climate change is a real and imminent threat to agriculture and that there is a pressing need to develop effective management strategies to reduce yield losses and prevent food insecurity. Importantly, such strategies should take into account the influences of non‐climatic and/or biotic factors (e.g., novel pests) on plant development.
Using a series of field experiments performed in the remote Peruvian Andes, we show that the dangers of climate change for crops include not only the direct effects of rising temperatures but also the indirect effects of changing biotic conditions. Our findings reveal that climate change is a real and imminent threat to agriculture.
1. The idea that variable fire regimes (pyrodiversity) may increase habitat heterogeneity and, consequently, increase biodiversity at the landscape level is a relatively old one. However, this idea ...has been recently challenged by studies showing that the biota of fire-prone ecosystems is so resilient to fire that variation in fire regime has little ecological consequences. 2. We evaluated how communities of ants - a dominant faunal group - differ with variation in the frequency and seasonal timing of fire in Brazilian Cerrado (savanna), a global biodiversity hotspot. We compared the number and composition of ant species foraging on the ground and in trees among experimental treatments with three fire frequencies (unburned for 37 years and burned every 2 or 4 years for the past 16 years) and three seasonal timings (early, mid and late dry season) of fire with a biennial frequency. 3. There were no significant differences in ant species richness in trees, and there were no significant differences in the richness of ground-dwelling ants among plots burned at different times of the dry season. However, unburned plots had fewer ground-dwelling ant species than those burned at 2 or 4 year intervals. We detected marked differences in species composition across regimes varying in both the frequency and the timing of fire, which were related to fire-induced changes in vegetation structure. Over 40% of the overall ant species richness recorded in our study site was attributed to differences in species composition among fire treatments. 4. Synthesis and applications. Our study shows that Cerrado ant diversity at the landscape scale is promoted by a diversity of fire regimes, and therefore supports the validity of the pyrodiversity-biodiversity hypothesis for the Cerrado biome. Our findings suggest that the current policy of fire suppression in Cerrado protected areas has a negative effect on overall biodiversity and therefore should be reconsidered.
Correlation between gut microbiota and host phylogeny could reflect codiversification over shared evolutionary history or a selective environment that is more similar in related hosts. These ...alternatives imply substantial differences in the relationship between host and symbiont, but can they be distinguished based on patterns in the community data themselves? We explored patterns of phylogenetic correlation in the distribution of gut bacteria among species of turtle ants (genus Cephalotes), which host a dense gut microbial community. We used 16S rRNA pyrosequencing from 25 Cephalotes species to show that their gut community is remarkably stable, from the colony to the genus level. Despite this overall similarity, the existing differences among species' microbiota significantly correlated with host phylogeny. We introduced a novel analytical technique to test whether these phylogenetic correlations are derived from recent bacterial evolution, as would be expected in the case of codiversification, or from broader shifts more likely to reflect environmental filters imposed by factors such as diet or habitat. We also tested this technique on a published data set of ape microbiota, confirming earlier results while revealing previously undescribed patterns of phylogenetic correlation. Our results indicated a high degree of partner fidelity in the Cephalotes microbiota, suggesting that vertical transmission of the entire community could play an important role in the evolution and maintenance of the association. As additional comparative microbiota data become available, the techniques presented here can be used to explore trends in the evolution of host‐associated microbial communities.
Most comparative studies of biological communities in different biogeographical regions highlight ecological convergence under matched environments. Here we use savanna ant communities as a striking ...example where such convergence has not occurred. The savanna ant faunas of Australia, Brazil and Africa have very different functional composition due to their highly contrasting evolutionary origins.We synthesise the literature relating to the diversity and composition of savanna ant communities in the three continents, along with ant community responses to fire and aridity.Australian savannas evolved in association with a desert biome and its fauna is strongly arid adapted: it is exceptionally thermophilic, granivorous species are extremely diverse and abundant, high diversity is maintained with increasing aridity, and communities are highly resilient to simplification of vegetation structure induced by frequent fire. Brazilian savannas evolved surrounded by rainforest and have a forest‐derived ant fauna; this fauna is not so highly thermophilic, granivory is almost absent, diversity declines with increasing aridity and communities are highly sensitive to fire‐induced vegetation change. Africa has a very generalised ant fauna that has moderate representations of highly thermophilic and granivorous species, diversity appears to decline with increasing aridity, but communities are highly resilient to fire.The different biogeographical histories of tropical savannas in Australia, Brazil and Africa have led to functionally distinct ant faunas that display contrasting responses to environmental stress and disturbance. Phylogenetic niche conservatism seems to be particularly strong for granivory and thermophilia. Such intercontinental differences have important implications for understanding biodiversity responses to land management and climate change.
We report the rediscovery of the exceedingly rarely collected and enigmatic fungus-farming ant species Mycetosoritis asper. Since the description of the type specimen in 1887, only four additional ...specimens are known to have been added to the world's insect collections. Its biology is entirely unknown and its phylogenetic position within the fungus-farming ants has remained puzzling due to its aberrant morphology. In 2014 we excavated and collected twenty-one colonies of M. asper in the Floresta Nacional de Chapecó in Santa Catarina, Brazil. We describe here for the first time the male and larva of the species and complement the previous descriptions of both the queen and the worker. We describe, also for the first time, M. asper biology, nest architecture, and colony demographics, and identify its fungal cultivar. Molecular phylogenetic analyses indicate that both M. asper and M. clorindae are members of the genus Cyphomyrmex, which we show to be paraphyletic as currently defined. More precisely, M. asper is a member of the Cyphomyrmex strigatus group, which we also show to be paraphyletic with respect to the genus Mycetophylax. Based on these results, and in the interest of taxonomic stability, we transfer the species M. asper, M. clorindae, and all members of the C. strigatus group to the genus Mycetophylax, the oldest available name for this clade. Based on ITS sequence data, Mycetophylax asper practices lower agriculture, cultivating a fungal species that belongs to lower-attine fungal Clade 2, subclade F.
Fire is an important agent of disturbance in tropical savannas, but relatively few studies have analyzed how soil-and-litter dwelling arthropods respond to fire disturbance despite the critical role ...these organisms play in nutrient cycling and other biogeochemical processes. Following the incursion of a fire into a woodland savanna ecological reserve in Central Brazil, we monitored the dynamics of litter-arthropod populations for nearly two years in one burned and one unburned area of the reserve. We also performed a reciprocal transplant experiment to determine the effects of fire and litter type on the dynamics of litter colonization by arthropods. Overall arthropod abundance, the abundance of individual taxa, the richness of taxonomic groups, and the species richness of individual taxa (Formiciade) were lower in the burned site. However, both the ordinal-level composition of the litter arthropod fauna and the species-level composition of the litter ant fauna were not dramatically different in the burned and unburned sites. There is evidence that seasonality of rainfall interacts with fire, as differences in arthropod abundance and diversity were more pronounced in the dry than in the wet season. For many taxa the differences in abundance between burned and unburned sites were maintained even when controlling for litter availability and quality. In contrast, differences in abundance for Collembola, Formicidae, and Thysanoptera were only detected in the unmanipulated samples, which had a lower amount of litter in the burned than in the unburned site throughout most of our study period. Together these results suggest that arthropod density declines in fire-disturbed areas as a result of direct mortality, diminished resources (i.e., reduced litter cover) and less favorable microclimate (i.e., increased litter desiccation due to reduction in tree cover). Although these effects were transitory, there is evidence that the increasingly prevalent fire return interval of only 1-2 years may jeopardize the long-term conservation of litter arthropod communities.
We conducted a meta-analysis of the effects of fire on the abundance and alpha diversity of ants based upon data published over the past 70 years. Overall, fire reduced ant diversity by 18 %, but had ...no effect on ant abundance. However, there was significant variation in the effect of fire on ant diversity amongst different vegetation types. Fire significantly decreased ant diversity in forests—especially in tropical forests—whereas in deserts, grasslands, and savannas it did not. Similarly, fire had a strong negative mean effect on ant diversity in sites where it is uncommon, but did not significantly affect diversity where it is a recurrent phenomenon. There is evidence that, in forests, wildfires have a stronger negative effect on ant diversity than does prescribed burning. In addition, we found marginally significant differences in the effect of fire on the abundance and diversity of forest ants among studies that sampled ants at different times post-fire, or that sampled ants from different soil strata. In contrast, fire did not significantly affect the abundance or diversity of savanna ants, and this was true even after we took into account the geographic location of the study, the ant community sampled, the time since fire, and the fire regime. Overall, the results of our study indicate that habitat type is an important predictor of ant community responses to fire. However, even within a given habitat, reported effects were quite variable among the studies reviewed, evidencing the idiosyncratic nature of fire effects on ants.
A possible response of many plant species to global warming is migration to higher elevations. However, these migrations may not be required if species can tolerate higher temperatures, or may be ...prevented if there are other factors such as changes in soil conditions that make upslope areas unsuitable.
We used a set of 3‐year field transplant experiments in the remote Peruvian Andes to simulate two possible responses of an abundant tropical montane cloudforest tree species (Weinmania bangii) to global warming: (a) ‘upward migration’, in which case seedlings of W. bangii's were grown at their current elevation/temperature but in soils transplanted from higher elevations and (b) ‘migration failure’, in which case seedlings were transplanted downslope along with their home soils into areas that are 1°C or 2°C warmer. We conducted separate experiments with populations from the upper/leading edge, middle and lower/trailing edges of W. bangii's elevational/thermal range to assess the influence of local adaptation on responses to changes in temperature or soil.
We found that seedling survival and growth were not affected by changes in soil conditions, regardless of the origin population. However, seedling survival decreased with temperature. A simulated warming of 1°C caused a significant reduction in the survival of seedlings transplanted from the mid‐range population, and 2°C warming caused a severe decrease in the survival of seedlings transplanted from both the mid‐range and bottom‐edge populations.
Synthesis. Our findings reveal that rising temperatures are a serious threat to plants, especially in populations growing in the hotter portion of their species’ range. At least in the case of W. bangii, novel soil conditions will not limit the establishment or growth of seedlings at higher elevations. As such, decreases in the survivorship at lower elevations may be offset through upward migrations as temperatures continue to increase.
Resumen
Una posible respuesta de muchas especies de plantas al calentamiento global es la migración a mayores elevaciones. Sin embargo, estas migraciones pueden no ser necesarias si las especies toleran temperaturas más altas, o la migración puede ser limitada por otros factores como los cambios en las condiciones del suelo, haciendo que a mayores elevaciones sean áreas inadecuadas.
Utilizamos un conjunto de experimentos de trasplante en campo (durante tres años) en áreas remotas en los Andes del Perú para simular dos posibles respuestas de una especie de árbol abundante del bosque nublado andino (Weinmania bangii) al calentamiento climático: (a) "migración ascendente", en el que las plántulas de W. bangii se trasplantaron en la misma elevación/temperatura actual pero con suelo traído desde elevaciones más altas; y (b) “falla en la migración”, en cuyo caso las plántulas juntamente con suelos de la misma elevación se trasplantaron cuesta abajo, a elevaciones que presentan 1°C ó 2°C más cálidas. Para evaluar la influencia de la adaptación local en las respuestas a los cambios en la temperatura o suelo, realizamos experimentos separados para poblaciones del borde superior, medio y borde inferior del rango altitudinal/térmico de W. bangii.
Encontramos que la sobrevivencia y crecimiento de las plántulas no fueron afectados por los cambios en las condiciones del suelo, independientemente de la población origen. Sin embargo, la sobrevivencia de las plántulas disminuyó con la temperatura. Un calentamiento simulado de 1°C causó una reducción significativa en la sobrevivencia de las plántulas trasplantadas de la población del rango medio, y el calentamiento de 2°C causó una disminución severa en la sobrevivencia de las plántulas trasplantadas de las poblaciones de rango medio e inferior.
Síntesis. Nuestros resultados revelan que el aumento de la temperatura es una amenaza real para las plantas, especialmente en las poblaciones que crecen en la parte más cálida del rango de distribución de la especie. Al menos en caso de W. bangii, las nuevas condiciones del suelo no limitarán el establecimiento o el crecimiento de plántulas a elevaciones más altas. Así, las disminuciones en la sobrevivencia en elevaciones más bajas podría ser compensada por las migraciones ascendentes a medida que la temperatura continúe aumentando.
Our findings reveal that rising temperatures are a serious threat to plants, especially in populations growing in the hotter portion of their species’ range. At least in the case of W. bangii, novel soil conditions will not limit the establishment or growth of seedlings at higher elevations. As such, decreases in the survivorship at lower elevations may be offset through upward migrations as temperatures continue to increase.
Aim
Similar to species richness, ecological interactions can vary across latitudinal and environmental gradients. Knowing the patterns and drivers of such variation could help us to better understand ...the role of species interactions in maintaining biodiversity. In this study, we analysed the macroecological patterns of the structure and interaction beta diversity of interaction networks involving trees and ants.
Location
Twenty‐nine sites encompassing 20 degrees of latitude throughout the Neotropical savanna.
Time period
2010–2015.
Major taxa studied
Trees and arboreal nesting ants.
Methods
For each site, we built an interaction network and calculated network size, interaction diversity (Shannon diversity of interactions), specialization, modularity, nestedness, and interaction dissimilarity (contribution of each network to the regional pool of possible interactions). We also determined how interaction beta diversity varied among all sampling sites. Net primary productivity (NPP), temperature and rainfall were evaluated as potential correlates of the observed changes in network descriptors and interaction beta diversity.
Results
We found no latitudinal gradient in network specialization, nestedness or modularity. However, sites at higher latitudes had larger networks, higher interaction diversity and higher interaction dissimilarity, and this was correlated mainly with the latitudinal variation in NPP. Interaction rewiring generated by the reassembly of the interactions between the same species in different sites was the main contributor to the total interaction beta diversity. However, the level of interaction rewiring was independent of the geographical and environmental distance between sampling sites.
Main conclusions
Ant–tree network structure remained relatively invariant across the latitudinal and environmental gradient possibly due to high interaction rewiring among the partners. Moreover, our findings show that more productive sites, located at higher latitudes, have high dissimilarity to the regional pool of possible interactions (i.e., strong interaction filtering), indicating that these sites significantly contribute to the maintenance of interaction biodiversity in Neotropical savannas.
Aim
Arboreal and ground‐dwelling species experience distinct microclimates, have contrasting thermal tolerances and thus may be expected to respond differentially to geographic climatic gradients. We ...tested this idea by evaluating if the degree of vertical stratification of savanna ant assemblages varies along a latitudinal climatic gradient, and by determining how compositional dissimilarities within each stratum varies across increased geographical and climatic distances.
Location
Brazil.
Taxon
Ants.
Methods
We sampled ants foraging on the ground or in trees at 32 sites. Species were classified according to their main foraging stratum, as arboreal, ground‐dweller or strata generalist. We used linear models to evaluate the effects of latitude and sampling stratum on species richness, and the effect of latitude on the proportion of species typical from trees or from the ground in different sampling strata. The influence of geographic and climatic distances on the compositional differences between assemblages from the same stratum was assessed using regression on distance matrices.
Results
Species richness on the ground increased with latitude significantly faster than in trees. The turnover of species between strata was lower at lower latitudes, where there were proportionally more strata generalists and species typical from the ground stratum foraging in trees. Consequently, the compositional dissimilarity between vertical strata decreased with decreasing latitude. Despite that, the dissimilarities between vertical strata were, on average, as great or even greater than the dissimilarities between assemblages from the same stratum across the horizontal space.
Main Conclusions
We found support for the idea that climatic variation across latitude had different effects on arboreal compared with ground‐foraging assemblages. Overall, our results suggest that as Brazilian savanna becomes hotter and drier as forecast under climate change, ant assemblages may become not only less diverse, notably on the ground, but also more homogeneous vertically.
PDF
