Plague and Climate: Scales Matter

Plague is enzootic in wildlife populations of small mammals in central and eastern Asia, Africa, South and North America, and has been recognized recently as a reemerging threat to humans. Its causative agent Yersinia pestis relies on wild rodent hosts and flea vectors for its maintenance in nature. Climate influences all three components (i.e., bacteria, vectors, and hosts) of the plague system and is a likely factor to explain some of plague's variability from small and regional to large scales. Here, we review effects of climate variables on plague hosts and vectors from individual or population scales to studies on the whole plague system at a large scale. Upscaled versions of small-scale processes are often invoked to explain plague variability in time and space at larger scales, presumably because similar scale-independent mechanisms underlie these relationships. This linearity assumption is discussed in the light of recent research that suggests some of its limitations

BioTIME 2.0: Expanding and Improving a Database of Biodiversity Time Series

Motivation Here, we make available a second version of the BioTIME database, which compiles records of abundance estimates for species in sample events of ecological assemblages through time. The updated version expands version 1.0 of the database by doubling the number of studies and includes substantial additional curation to the taxonomic accuracy of the records, as well as the metadata. Moreover, we now provide an R package (BioTIMEr) to facilitate use of the database. Main Types of Variables Included The database is composed of one main data table containing the abundance records and 11 metadata tables. The data are organised in a hierarchy of scales where 11,989,233 records are nested in 1,603,067 sample events, from 553,253 sampling locations, which are nested in 708 studies. A study is defined as a sampling methodology applied to an assemblage for a minimum of 2 years. Spatial Location and Grain Sampling locations in BioTIME are distributed across the planet, including marine, terrestrial and freshwater realms. Spatial grain size and extent vary across studies depending on sampling methodology. We recommend gridding of sampling locations into areas of consistent size. Time Period and Grain The earliest time series in BioTIME start in 1874, and the most recent records are from 2023. Temporal grain and duration vary across studies. We recommend doing sample-level rarefaction to ensure consistent sampling effort through time before calculating any diversity metric. Major Taxa and Level of Measurement The database includes any eukaryotic taxa, with a combined total of 56,400 taxa. Software Format csv and. SQL

EFFECTS OF VERTEBRATE PREDATION ON A CAVIOMORPH RODENT, THE DEGU (OCTODON-DEGUS), IN A SEMIARID THORN SCRUB COMMUNITY IN CHILE

The effects of vertebrate predation have been monitored since 1989 on 16 replicated 0.56 ha study plots in a semiarid thorn scrub community in north-central Chile. Using fences of different heights with and without holes and suspended game netting to alter principal predator (foxes and raptors) and large rodent herbivore (Octodon degus) access, four grids each have been assigned to the following treatments: 1) low fencing and holes allowing free access of predators and small mammals; 2) low fencing without holes to exclude degus only, 3) high fencing and netting with holes to exclude predators only; and 4) high fencing and netting without holes to exclude predators and degus. Small mammal population censuses are conducted monthly using mark-recapture techniques. Degu population trends during 1989 and 1990 showed strongly but nonsignificantly lower numbers in control plots during months when densities were characteristically low (September November) for this seasonally reproductive species; since March 1991, differences have become persistent and increasingly significant. Predators appear to have greater numerical effects when their prey populations are low. Survival times of degus, particularly established adults, were significantly longer in predator exclusion grids during the 2 1/2 years of observation; thus, predation also affects prey population structure

A long-term study of vertebrate predator responses to an El Nino (ENSO) disturbance in western South America

We analyzed the putative effects of the El Nino Southern Oscillation (ENSO) of 1991-92 in a semi-arid locality of northern Chile. We obtained 30 months of pre ENSO data, followed by 36 months of peak and post ENSO data (total = 5.5 yr). The rainy winter of 1991 resulted in a three-fold increase in total seed bank (perennial and ephemerals pooled) and in ephemeral (but not perennial) herb cover. Seed and herbage eaters (rodents) irrupted to population levels ca 20 times higher during the breeding season of 1991 than the preceding wintering season. Diurnal carnivorous predators (hawks, owls, and foxes) showed a delayed response to the irruption, increasing from seven individuals sighted during the wintering season of 1991 to 13 during the wintering season of 1992. A seemingly counterclockwise trajectory of predator abundance versus prey levels suggested a pattern of prey-driven dynamics, but confidence intervals were likely broad. In this semiarid locality, it appears that ENSO effects did not cascade down from higher to lower trophic levels, but rather the opposite. In this bottom-up scenario, we predict that as primary productivity varies with rainfall, so should secondary (mammal prey densities), and tertiary productivity (vertebrate predators). Long-term monitoring of this terrestrial ecosystem is needed to test this prediction

The interplay of biotic and abiotic factors in a semiarid Chilean mammal assemblage

Since early 1989, we have conducted a large-scale ecological manipulation in a semiarid thorn scrub community in north-central Chile. We have excluded vertebrate predators (raptors and mammalian carnivores), and larger small mammal herbivore/competitors (i.e., degus, Octodon degus) from replicated 0.56-ha plots, and monitored small mammal population and plant responses over more than ten years. Repeated measures ANOVAs on minimum number known alive (MNKA) estimates of small mammals for a six-year period (1990-1996) spanning an El Nino event in 1991-1992 showed strong responses of some species to predator exclusions (e.g., O. degus; Darwin's leaf-eared mouse, Phyllotis darwini; the chinchilla-rat, Abrocoma bennetti). However, responses varied in time with significant effects during pre-El Nino (1990-1992) and El Nino (1992-1994) periods (i.e., 0. degus), or pre-El Nino and post-El Nino (1994-1996) periods (P. darwini. A. bennetti). Other species showed no responses to predator exclusions (e.g., olivaceous field mouse, Akodon olivaceus; long-haired field mouse, Abrothrix longipilis; long-tailed rice rat, Oligoryzomys longi caudatus). Some effects of competitor (degu) exclusions were detected (e.g., A. bennetti during the El Nino and post-El Nino periods; O. longicatrrlntus during the El Nino). "Top-down," factors (i.e., biotic interactions) appear to have greater effects on "core species" (i.e., P. darwini, O. degus) which persist in the thorn scrub. Other species (e.g., A. longipilis, O. longicaudatus) are transitory residents or "opportunistic" with lesser effects of biotic interactions, and their populations may be controlled by source-sink dynamics. All species had strong, responses to the 1991-1992 El Nino indicating primary control by "bottom-up" factors

SPATIAL-DISTRIBUTION OF SOIL NUTRIENTS AND EPHEMERAL PLANTS UNDERNEATH AND OUTSIDE THE CANOPY OF PORLIERIA-CHILENSIS SHRUBS (ZYGOPHYLLACEAE) IN ARID COASTAL CHILE

Soil nutrients and density and biomass of annual plants underneath and outside the canopy of Porlieria chilensis shrubs were measured at the end of the growing season in a protected arid coastal site in Chile. Levels of soil nitrogen, phosphorus and organic matter were significantly higher underneath than outside the canopies of shrubs. Almost 4 times as many plants occurred outside than underneath shrubs, but no significant differences in total aboveground biomass were found. Several species had higher densities and/or biomass outside rather than underneath shrubs, whereas others showed the opposite trend. Species richness was lower underneath P. chilensis canopy. The spatial microdistribution of ephemeral species may be explained by differential water and nutrient requirements. Comparison of the patterns observed in our protected site versus surrounding unprotected areas supports the generalization that man, by removing shrubs and trees, has changed a previous heterogeneous spatial distribution of nutrients to a more homogenous one

HETEROGENEOUS RESPONSES OF SMALL MAMMALS TO AN EL-NINO SOUTHERN-OSCILLATION EVENT IN NORTHCENTRAL SEMIARID CHILE AND THE IMPORTANCE OF ECOLOGICAL SCALE

A prolonged El Nino Southern Oscillation (ENSO) event during 1991-1992 with three times the normal annual 85-mm rainfall was accompanied by major changes in numbers of small mammals at a semiarid Mediterranean site in northcentral Chile. Several demographic patterns were evident. Akodon olivacerrs, an omnivore, had a rapid increase in population size of more than an order of magnitude. Phyllotis darwini, a granivore-herbivore, showed somewhat delayed, smaller increases superimposed on annual oscillations. Octodon degus, an herbivore, showed a delayed response with larger increases and extended breeding in 1992-1993. Finally, Oligorzyzomys longicaudatus, a granivore, experienced increases during both a dry (1990, ppt = 32 mm) and a wet year (1992). Other species such as Aborthrix longipilis, Abrocoma bennetti, and Thylamys elegans had smaller, delayed demo,oraphic responses. Reproductive rates for the first three species were higher due to the ENSO event only in O. negus males and P. darwini as a quadratic function of time. Survival rates of all four principal species were significantly greater during the 1991-1992 ENSO. Finally, average movement between captures was lower during ENSO years, suggesting behavioral changes. Explanations for these patterns include rainfall-related increases in food-resource levels (A. olivaceus and P. darwini), the importance of source-sink processes in vagile species from more mesic, adjacent habitats (O. longicaudatus), and delayed responses to extrinsic events in species with long gestation (O. degus, A. bennetti). The heterogeneity of species responses suggests different capabilities for small mammals to respond to an extrinsic, large-scale event, and it emphasizes the importance of long-term studies in semiarid systems