Recent analyses have reported catastrophic global declines in vertebrate populations
. However, the distillation of many trends into a global mean index obscures the variation that can inform ...conservation measures and can be sensitive to analytical decisions. For example, previous analyses have estimated a mean vertebrate decline of more than 50% since 1970 (Living Planet Index
). Here we show, however, that this estimate is driven by less than 3% of vertebrate populations; if these extremely declining populations are excluded, the global trend switches to an increase. The sensitivity of global mean trends to outliers suggests that more informative indices are needed. We propose an alternative approach, which identifies clusters of extreme decline (or increase) that differ statistically from the majority of population trends. We show that, of taxonomic-geographic systems in the Living Planet Index, 16 systems contain clusters of extreme decline (comprising around 1% of populations; these extreme declines occur disproportionately in larger animals) and 7 contain extreme increases (around 0.4% of populations). The remaining 98.6% of populations across all systems showed no mean global trend. However, when analysed separately, three systems were declining strongly with high certainty (all in the Indo-Pacific region) and seven were declining strongly but with less certainty (mostly reptile and amphibian groups). Accounting for extreme clusters fundamentally alters the interpretation of global vertebrate trends and should be used to help to prioritize conservation efforts.
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GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
Concerns over the consequences of global climate change for biodiversity have spurred a renewed interest in organismal thermal physiology. However, temperature is only one of many environmental axes ...poised to change in the future. In particular, hydrologic regimes are also expected to shift concurrently with temperature in many regions, yet our understanding of how thermal and hydration physiology jointly affect performance and fitness is still limited for most taxonomic groups. Here, we investigated the relationship between functional performance, hydration state and temperature in three ecologically distinct amphibians, and compare how temperature and water loss can concurrently limit activity under current climate conditions. We found that performance was maintained across a broad range of hydration states in all three species, but then declines abruptly after a threshold of 20-30% mass loss. This rapid performance decline was accelerated when individuals were exposed to warmer temperatures. Combining our empirical hydrothermal performance curves with species-specific biophysical models, we estimated that dehydration can increase restrictions on species' activity by up to 60% compared to restriction by temperature alone. These results illustrate the importance of integrating species' hydration physiology into forecasts of climate vulnerability, as omitting this axis may significantly underestimate the effects of future climate change on Earth's biological diversity.
A deadly amphibian disease goes global Greenberg, Dan A; Palen, Wendy J
Science (American Association for the Advancement of Science),
03/2019, Volume:
363, Issue:
6434
Journal Article
Peer reviewed
Chytrid infection is linked to the decline of more than 500 amphibian species
Trade routes have shaped human history by connecting distant civilizations, allowing the exchange of materials, ...technology, and people, but also diseases ( 1 ). Pathogens have been frequent hitchhikers, bringing them in contact with new hosts that provide the fuel for epidemic outbreaks of disease. Humans are not the only victims of trade-driven diseases, but scientists have only recently begun to appreciate the risk to biodiversity of inadvertently introducing new pathogens to naïve evolutionary arenas. On page 1459 of this issue, Scheele et al. ( 2 ) demonstrate the consequences of globalized pathogen exchange by reconstructing the hidden history of disease-driven declines and extinctions for hundreds of amphibian species.
Salamanders have some of the largest, and most variable, genome sizes among the vertebrates. Larger genomes have been associated with larger cell sizes, lower metabolic rates, and longer embryonic ...and larval durations in many different taxonomic groups. These life-history traits are often important for dictating fitness under different environmental conditions, suggesting that a species' genome size may have the potential to constrain its ecological distribution. We test how genome size varies with the ephemerality of larval habitat across the salamanders, predicting that species with larger genomes will be constrained to more permanent habitats that permit slower development, while species with smaller genomes will be more broadly distributed across the gradient of habitat ephemerality. We found that salamanders with larger genomes are almost exclusively associated with permanent aquatic habitats. In addition, the evolutionary transition rate between permanent and ephemeral larval habitats is much higher in salamander lineages with smaller genome sizes. These patterns suggest that genome size may act as an evolutionary constraint on the ecological habitats of salamanders, restricting those species with large genomes and slower development to habitats with permanent sources of water.
The state of biodiversity for most of the world is largely enigmatic due to a lack of long‐term population monitoring data. Citizen science programs could substantially contribute to resolving this ...data crisis, but there are noted concerns on whether methods can overcome the biases and imprecision inherent to aggregated opportunistic observations. We explicitly test this question by examining the temporal correlation of population time‐series estimated from opportunistic citizen science data and a rigorous fishery‐independent survey that concurrently sampled populations of coral‐reef fishes (n = 87) in Key Largo, Florida, USA, over 25 years. The majority of species exhibited positive temporal correlations between population time‐series, but survey congruence varied considerably amongst taxonomic and trait‐based groups. Overall, these results suggest that citizen scientists can be effective sentinels of ecological change, and that there may be substantial value in leveraging their observations to monitor otherwise data‐limited marine species.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
New species of marine fishes are found to emerge at a faster rate in high-latitude oceans, which have lower densities of species, than in the species-rich tropics. Are the tropics too crowded for new ...species to take hold?
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KISLJ, NUK, SBMB, UL, UM, UPUK
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