Productivity is a key driver of ecosystem structure and function, so long‐term studies are critical to understanding ecosystems with high temporal variation in productivity. In some deserts, ...productivity, driven by moisture availability, varies immensely over time (rainfall) and space (landscape factors). At high productivity, species richness is expected to be driven in opposing directions by abundance (More Individuals Hypothesis – MIH) and competition. While studies investigating the impacts of spatial variation in productivity on community structure are common, the impacts of temporal variability on productivity are poorly understood.
We tested how well rainfall predicted the activity, species numbers and assemblage composition of ants and if responses were moderated by landscape position. We also asked whether the number of species (richness per sampling unit and estimated species richness) responded directly to rainfall or was moderated by ant activity or competition from dominant ants.
Over a 22‐year period, when annual rainfall fluctuated between 79 mm and 570 mm, we sampled ants using pitfall traps in paired dune and swale habitats in the Simpson Desert, Australia. We used climate records over this period to model changes in ant assemblages.
Activity of dominant ants responded primarily to long‐term rainfall, increasing exponentially, while subordinate ants responded to short‐term weather and time. Consistent with the MIH, the number of ant species was best predicted by activity, particularly that of subordinate ants. Activity of dominant ants had a declining positive effect on numbers of species. Landscape position strongly predicted species composition, while long‐term rainfall determined composition at genus level but not species level. Over time, species composition fluctuated, but several genera consistently increased in activity.
Productivity moderators such as long‐term rainfall and landscape position are key drivers of ant activity and composition in the study ecosystem, acting indirectly on numbers of species. Numbers of species were explained largely by ant activity, making a strong case for the MIH, but not competition. Longer periods of low rainfall may indirectly reduce species richness in desert ecosystems. However, a trend to increasing richness over time may indicate that conservation management can ameliorate this impact.
This study reports results for the longest study of ant communities ever conducted in an arid environment with highly variable rainfall. This is significant because long‐term studies are necessary to understand community dynamics in highly variable ecosystems. This work improves our understanding of long‐term faunal responses to variation in rainfall in arid environments, which is particularly important in the context of a changing climate.
Under the Ecosystem Exploitation Hypothesis ecosystem productivity predicts trophic complexity, but it is unclear if spatial and temporal drivers of productivity have similar impacts. Long-term ...studies are necessary to capture temporal impacts on trophic structure in variable ecosystems such as deserts. We sampled ants and measured plant resources in the Simpson Desert, central Australia over a 22-year period, during which rainfall varied 10-fold. We sampled dune swales (higher nutrient) and crests (lower nutrient) to account for spatial variation in productivity. We asked how temporal and spatial variation in productivity affects the abundance of ant trophic guilds. Precipitation increased vegetation cover, with the difference more pronounced on dune crests; seeding and flowering also increased with precipitation. Generalist activity increased over time, irrespective of productivity. Predators were more active in more productive (swale) habitat, i.e. spatial impacts of productivity were greatest at the highest trophic level. By contrast, herbivores (seed harvesters and sugar feeders) increased with long-term rainfall; seed harvesters also increased as seeding increased. Temporal impacts of productivity were therefore greatest for low trophic levels. Whether productivity variation leads to top-down or bottom-up structured ecosystems thus depends on the scale and dimension (spatial or temporal) of productivity.
In recent years the focus in ecology has shifted from species to a greater emphasis on functional traits. In tandem with this shift, a number of trait databases have been developed covering a range ...of taxa. Here, we introduce the GlobalAnts database.
Globally, ants are dominant, diverse and provide a range of ecosystem functions. The database represents a significant tool for ecology in that it (i) contributes to a global archive of ant traits (morphology, ecology and life history) which complements existing ant databases and (ii) promotes a trait‐based approach in ant and other insect ecology through a broad set of standardised traits.
The GlobalAnts database is unique in that it represents the largest online database of functional traits with associated georeferenced assemblage‐level data (abundance and/or occupancy) for any animal group with 9056 ant species and morphospecies records for entire local assemblages across 4416 sites.
We describe the structure of the database, types of traits included and present a summary of data coverage. The value of the database is demonstrated through an initial examination of trait distributions across subfamilies, continents and biomes.
Striking biogeographic differences in ant traits are highlighted which raise intriguing questions as to the mechanisms generating them.
The decline of ecosystem engineers alters ecosystems, with impacts cascading through to other organisms. Through engineering and predation, digging mammals may affect burrowing invertebrate ...assemblages, leading to changes in invertebrate-driven soil engineering. Using a mammal reintroduction sanctuary in southern Australia, we tested how digging mammals alter invertebrate burrows (density and size of burrow entrances) and whether these impacts were scale-dependent. We examined the micro-site (pit-scale) effects of mammal foraging pits on invertebrate burrowing activity by comparing natural and artificial pits and bare-ground, and artificial pits of different dimensions within different microhabitat types. To test how mammals affected invertebrate burrows and soil physical and chemical properties at larger scales, we used an exclusion experiment (plot-scale) and surveys inside and outside a reintroduction reserve (landscape scale). Invertebrate burrows were more numerous in mammal pits than bare-ground and artificial pits, and larger in mammal pits than bare-ground. The density and size of invertebrate burrows depended on pit morphology, with burrow density greatest in narrow bilby pits and large burrows favoured by bettong pits. However, the influence of foraging pits on invertebrate burrows was scale-dependent: changes in invertebrate burrows were not detected at the plot or landscape scale. Only 4.5% of land surface area was occupied by pits and this might be insufficient to alter burrow or soil properties detectably in un-stratified surveys at larger scales. Digging mammals altered the small-scale (but not large-scale) distribution of invertebrate burrows, suggesting that their reintroduction provides an avenue through which to restore the heterogeneity of other organisms and functions in ecosystems.
•Mammal foraging pits increases abundances and size of invertebrate burrows.•Narrower pits support a greater density of invertebrate burrows per unit area.•At larger scales, digging mammals increase heterogeneity, rather than total activity.
The relationship between levels of dominance and species richness is highly contentious, especially in ant communities. The dominance‐impoverishment rule states that high levels of dominance only ...occur in species‐poor communities, but there appear to be many cases of high levels of dominance in highly diverse communities. The extent to which dominant species limit local richness through competitive exclusion remains unclear, but such exclusion appears more apparent for non‐native rather than native dominant species. Here we perform the first global analysis of the relationship between behavioral dominance and species richness. We used data from 1,293 local assemblages of ground‐dwelling ants distributed across five continents to document the generality of the dominance‐impoverishment rule, and to identify the biotic and abiotic conditions under which it does and does not apply. We found that the behavioral dominance–diversity relationship varies greatly, and depends on whether dominant species are native or non‐native, whether dominance is considered as occurrence or relative abundance, and on variation in mean annual temperature. There were declines in diversity with increasing dominance in invaded communities, but diversity increased with increasing dominance in native communities. These patterns occur along the global temperature gradient. However, positive and negative relationships are strongest in the hottest sites. We also found that climate regulates the degree of behavioral dominance, but differently from how it shapes species richness. Our findings imply that, despite strong competitive interactions among ants, competitive exclusion is not a major driver of local richness in native ant communities. Although the dominance‐impoverishment rule applies to invaded communities, we propose an alternative dominance‐diversification rule for native communities.
Our global analysis of more than 1,200 local ant communities reveals that in the absence of non‐native dominant species high levels of behavioral dominance commonly occur with high diversity. Diversity tends to be lower when communities include non‐native dominant species, but in native ant communities it is higher with than without dominant species. Despite strong competitive interactions among ants, our findings indicate that competitive exclusion is not a major driver of local richness in native ant communities. Although the dominance‐impoverishment rule applies to invaded communities, we propose an alternative dominance‐diversification rule for native communities.
What forces structure ecological assemblages? A key limitation to general insights about assemblage structure is the availability of data that are collected at a small spatial grain (local ...assemblages) and a large spatial extent (global coverage). Here, we present published and unpublished data from 51,388 ant abundance and occurrence records of more than 2,693 species and 7,953 morphospecies from local assemblages collected at 4,212 locations around the world. Ants were selected because they are diverse and abundant globally, comprise a large fraction of animal biomass in most terrestrial communities, and are key contributors to a range of ecosystem functions. Data were collected between 1949 and 2014, and include, for each geo-referenced sampling site, both the identity of the ants collected and details of sampling design, habitat type, and degree of disturbance. The aim of compiling this data set was to provide comprehensive species abundance data in order to test relationships between assemblage structure and environmental and biogeographic factors. Data were collected using a variety of standardized methods, such as pitfall and Winkler traps, and will be valuable for studies investigating large-scale forces structuring local assemblages. Understanding such relationships is particularly critical under current rates of global change. We encourage authors holding additional data on systematically collected ant assemblages, especially those in dry and cold, and remote areas, to contact us and contribute their data to this growing data set.
"Storefronts run in fads," said Commissioner John Baird in a telephone interview after the vote. He remembered when Karroll's Inc., the ground-floor menswear shop at the Reliance Building at 32 N. ...State St., put up a modern storefront that was later removed as part of the city-subsidized restoration of the turn-of-the-century skyscraper, now known as the Hotel Burnham. Among those elements, the owner said, are the removal of the fire escapes on the State Street facade as well as the grill-like screens that try to hide them. The owners plan to redesign the Monroe Street entrance, using the hand-forged, bronze doors with a peacock motif that marked the C.D. Peacock jewelry store at the hotel. As the current hotel replaced that building in the 1920s, guests were moved from the old structure to the new one, allowing the hotel to remain open even as it grew. Its main entertainment venue, the Empire Room, featured such performers as Maurice Chevalier, Guy Lombardo, Jack Benny, Carol Channing and the Merriel Abbott dancers.
Although countless highly penetrant variants have been associated with Mendelian disorders, the genetic etiologies underlying complex diseases remain largely unresolved. By mining the medical records ...of over 110 million patients, we examine the extent to which Mendelian variation contributes to complex disease risk. We detect thousands of associations between Mendelian and complex diseases, revealing a nondegenerate, phenotypic code that links each complex disorder to a unique collection of Mendelian loci. Using genome-wide association results, we demonstrate that common variants associated with complex diseases are enriched in the genes indicated by this “Mendelian code.” Finally, we detect hundreds of comorbidity associations among Mendelian disorders, and we use probabilistic genetic modeling to demonstrate that Mendelian variants likely contribute nonadditively to the risk for a subset of complex diseases. Overall, this study illustrates a complementary approach for mapping complex disease loci and provides unique predictions concerning the etiologies of specific diseases.
Display omitted
•Analyzed over 100 million unique patient records from the United States and Denmark•Discovered a nondegenerate, Mendelian comorbidity code for complex diseases•Results predict genetic loci enriched with a spectrum of complex disease variants•Inferred widespread epistasis among loci that harbor deleterious Mendelian variants
By mining the medical records of over 110 million patients, thousands of previously unappreciated associations between Mendelian and complex diseases are detected.
Most forced migrants around the world are displaced within the Global South. We study whether and how de jure policies on forced displacement affect where forced migrants flee in the developing ...world. Recent evidence from the Global North suggests migrants gravitate toward liberal policy environments. However, existing analyses expect de jure policies to have little effect in the developing world, given strong presumptions that policy enforcement is poor and policy knowledge is low. Using original data on de jure displacement policies for 92 developing countries and interviews with 126 refugees and policy makers, we document a robust association between liberal de jure policies and forced migrant flows. Gravitation toward liberal environments is conditional on factors that facilitate the diffusion of policy knowledge, such as transnational ethnic kin. Policies for free movement, services, and livelihoods are especially attractive. Utility-maximizing models of migrant decision making must take de jure policy provisions into account.
PDF
