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"Dirzo, Rodolfo"
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Before they vanish : saving nature's populations--and ourselves
\"This work is a new, hopeful analysis from the world's top natural scientists that shows us the way to save the endangered species of the world\"-- Provided by publisher.
BOOK
Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines
The population extinction pulse we describe here shows, from a quantitative viewpoint, that Earth’s sixth mass extinction is more severe than perceived when looking exclusively at species extinctions. Therefore, humanity needs to address anthropogenic population extirpation and decimation immediately. That conclusion is based on analyses of the numbers and degrees of range contraction (indicative of population shrinkage and/or population extinctions according to the International Union for Conservation of Nature) using a sample of 27,600 vertebrate species, and on a more detailed analysis documenting the population extinctions between 1900 and 2015 in 177 mammal species. We find that the rate of population loss in terrestrial vertebrates is extremely high—even in “species of low concern.” In our sample, comprising nearly half of known vertebrate species, 32% (8,851/27,600) are decreasing; that is, they have decreased in population size and range. In the 177 mammals for which we have detailed data, all have lost 30% or more of their geographic ranges and more than 40% of the species have experienced severe population declines (>80% range shrinkage). Our data indicate that beyond global species extinctions Earth is experiencing a huge episode of population declines and extirpations, which will have negative cascading consequences on ecosystem functioning and services vital to sustaining civilization. We describe this as a “biological annihilation” to highlight the current magnitude of Earth’s ongoing sixth major extinction event.
Journal Article
Patterns, Causes, and Consequences of Anthropocene Defaunation
Anthropocene defaunation, the global extinction of faunal species and populations and the decline in abundance of individuals within populations, has been predominantly documented in terrestrial ecosystems, but indicators suggest defaunation has been more severe in freshwater ecosystems. Marine defaunation is in a more incipient stage, yet pronounced effects are already apparent and its rapid acceleration seems likely. Defaunation now impacts the planet's wildlife with profound cascading consequences, ranging from local to global coextinctions of interacting species to the loss of ecological services critical for humanity. Slowing defaunation will require aggressively reducing animal overexploitation and habitat destruction; mitigating climate disruption; and stabilizing the impacts of human population growth and uneven resource consumption. Given its omnipresence, defaunation should receive status of major global environmental change and should be addressed with the same urgency as deforestation, pollution, and climatic change. Global action is needed to prevent defaunation's current trajectory from catalyzing the planet's sixth major extinction.
Journal Article
Phenotypic plasticity in plant defense across life stages
As they develop, many plants deploy shifts in antiherbivore defense allocation due to changing costs and benefits of their defensive traits. Plant defenses are known to be primed or directly induced by herbivore damage within generations and across generations by long-lasting epigenetic mechanisms. However, little is known about the differences between life stages of epigenetically inducible defensive traits across generations. To help fill this knowledge gap, we conducted a multigenerational experiment to determine whether defense induction in wild radish plants was reflected in chromatin modifications (DNA methylation); we then examined differences between seedlings and reproductive plants in current and transgenerational plasticity in chemical (glucosinolates) and physical (trichomes) defenses in this species. Herbivory triggered genome methylation both in targeted plants and their offspring. Within one generation, both defenses were highly inducible at the seedling stage, but only chemical defenses were inducible in reproductive plants. Across generations, herbivory experienced by mother plants caused strong direct induction of physical defenses in their progeny, with effects lasting from seedling to reproductive stages. For chemical defenses, however, this transgenerational induction was evident only in adults. Transgenerational priming was observed in physical and chemical defenses, particularly in adult plants. Our results show that transgenerational plasticity in plant defenses in response to herbivore offense differs for physical and chemical defense and changes across plant life stages.
Journal Article
Defaunation in the Anthropocene
We live amid a global wave of anthropogenically driven biodiversity loss: species and population extirpations and, critically, declines in local species abundance. Particularly, human impacts on animal biodiversity are an under-recognized form of global environmental change. Among terrestrial vertebrates, 322 species have become extinct since 1500, and populations of the remaining species show 25% average decline in abundance. Invertebrate patterns are equally dire: 67% of monitored populations show 45% mean abundance decline. Such animal declines will cascade onto ecosystem functioning and human well-being. Much remains unknown about this \"Anthropocene defaunation\"; these knowledge gaps hinder our capacity to predict and limit defaunation impacts. Clearly, however, defaunation is both a pervasive component of the planet's sixth mass extinction and also a major driver of global ecological change.
Journal Article
Functional Traits Shape Seed–Rodent Interactions in a Subtropical Forest: Insights From Individual‐Based Tracking With Double‐Duplex PIT Tagging
Functional traits of plants and animals play a pivotal role in shaping mutualistic or predatory interactions within plant–animal systems, directly regulating the structure and function of forest ecosystems. Yet, the outcomes of multispecies interactions—particularly in seed–rodent systems—remain inadequately resolved, largely because traditional methods fail to track individual‐level interactions and seed fates with sufficient precision. To address this gap, we applied a novel double‐duplex passive integrated transponder (PIT) tagging technique to investigate the fates of seeds from four sympatric tree species (with distinct seed traits) when exploited by two sympatric rodent species (with contrasting body sizes) in a subtropical forest of Southwest China from 2018 to 2019. Our results revealed that rodent body size and seed size are key determinants of seed fates. The larger rat Niviventer confucianus scatter‐hoarded and consumed seeds of all four trees, with a significant preference for large‐sized seeds of Quercus variabilis and Lithocarpus harlandii . In contrast, the smaller mouse Apodemus draco did not hoard the large‐sized seeds of L. harlandii and showed a significant preference for small‐sized seeds of Camellia oleifera . Additionally, N. confucianus exhibited a higher interspecific pilfering rate on seeds of C. oleifera and L. harlandii than A. draco . Our study highlights the significant role of size traits in shaping the mutualistic or predatory interactions in seed–rodent systems and demonstrates the utility of individual‐based tracking in disentangling complex species interactions.
Journal Article
Association between anthropization and rodent reservoirs of zoonotic pathogens in Northwestern Mexico
The world is facing a major pulse of ecological and social changes that may favor the risk of zoonotic outbreaks. Such risk facilitation may occur through the modification of the host’s community diversity and structure, leading to an increase in pathogen reservoirs and the contact rate between these reservoirs and humans. Here, we examined whether anthropization alters the relative abundance and richness of zoonotic reservoir and non-reservoir rodents in three Socio-Ecological Systems. We hypothesized that anthropization increases the relative abundance and richness of rodent reservoirs while decreasing non-reservoir species. We first developed an Anthropization index based on 15 quantitative socio-ecological variables classified into five groups: 1) Vegetation type, 2) Urbanization degree, 3) Water quality, 4) Potential contaminant sources, and 5) Others. We then monitored rodent communities in three regions of Northwestern Mexico (Baja California, Chihuahua, and Sonora). A total of 683 rodents of 14 genera and 27 species were captured, nine of which have been identified as reservoirs of zoonotic pathogens (359 individuals, 53%). In all regions, we found that as anthropization increased, the relative abundance of reservoir rodents increased; in contrast, the relative abundance of non-reservoir rodents decreased. In Sonora, reservoir richness increased with increasing anthropization, while in Baja California and Chihuahua non-reservoir richness decreased as anthropization increased. We also found a significant positive relationship between the anthropization degree and the abundance of house mice ( Mus musculus ) and deer mice ( Peromyscus maniculatus ), the most abundant reservoir species in the study. These findings support the hypothesis that reservoir species of zoonotic pathogens increase their abundance in disturbed environments, which may increase the risk of pathogen exposure to humans, while anthropization creates an environmental filtering that promotes the local extinction of non-reservoir species.
Journal Article
Sex-Related Differences in Reproductive Allocation, Growth, Defense and Herbivory in Three Dioecious Neotropical Palms
Background: Frequently, in dioecious plants, female plants allocate more resources to reproduction than male plants. Therefore it is expected that asymmetrical allocation to reproduction may lead to a reproduction-growth tradeoff, whereby female plants grow less than male plants, but invest more in defenses and thus experience lower herbivory than male plants. Methodology/Principal Findings: We tested these expectations by comparing resource allocation to reproduction, growth and defense and its consequences on herbivory in three sympatric dioecious Chamaedorea palms (C. alternans, C. pinnatifrons and C. ernesti-augusti) using a pair-wise design (replicated male/female neighboring plants) in a Mexican tropical rain forest. Our findings support the predictions. Biomass allocation to reproduction in C. pinnatifrons was 3-times higher in female than male plants, consistent with what is known in C. alternans and C. ernesti-augusti. Growth (height and leaf production rate and biomass production) was higher in male plants of all three species. Female plants of the three species had traits that suggest greater investment in defense, as they had 4–16% tougher leaves, and 8–18% higher total phenolic compounds concentration. Accordingly, female plants sustained 53–78% lower standing herbivory and 49–87% lower herbivory rates than male plants. Conclusions/Significance: Our results suggests that resource allocation to reproduction in the studied palms is more costly to female plants and this leads to predictable intersexual differences in growth, defense and herbivory. We conclude that resource allocation to reproduction in plants can have important consequences that influence their interaction with herbivores. Since herbivory is recognized as an important selective force in plants, these results are of significance to our understanding of plant defense evolution.
Journal Article
Determinants of vector-borne avian pathogen occurrence in a mosaic of habitat fragmentation in California
Background
As habitat fragmentation increases, ecological processes, including patterns of vector-borne pathogen prevalence, will likely be disrupted, but ongoing investigations are necessary to examine this relationship. Here, we report the differences in the prevalence of Lyme disease (
Borrelia burgdorferi
sensu lato, s.l.) and haemoproteosis (
Haemoproteus
spp.) pathogens in avian populations of a fragmented habitat.
B. burgdorferi
s.l. is a generalist pathogen that is transmitted by
Ixodes pacificus
vectors in California, and
Haemoproteus
is an avian parasite transmitted by
Culicoides
vectors.
Methods
To determine whether biotic (avian and mammalian abundance) or abiotic characteristics (patch size and water availability) correlated with infection prevalence change, we screened 176 birds sampled across seven sites in oak woodland habitat in northern California.
Results
While biotic factors correlated with an increase in both pathogens, infection prevalence of
Haemoproteus
spp. was only associated with individual-level traits, specifically foraging substrate and diet, and
B. burgdorferi
s.l. was associated with community-level characteristics, both total mammal and, specifically, rodent abundance. Proximity to water was the only abiotic factor found to be significant for both pathogens and reinforces the importance of water availability for transmission cycles. Larger patch sizes did not significantly affect infection prevalence of
Haemoproteus,
but did increase the prevalence of
B. burgdorferi.
Conclusions
These results highlight that while environmental factors (specifically habitat fragmentation) have a limited role in vector-borne pathogen prevalence, the indirect impact to biotic factors (community composition) can have consequences for both
Haemoproteus
and
B. burgdorferi
prevalence in birds. Given the pervasiveness of habitat fragmentation, our results are of broad significance.
Graphical abstract
Journal Article
Transgenerational Plasticity in Flower Color Induced by Caterpillars
Variation in flower color due to transgenerational plasticity could stem directly from abiotic or biotic environmental conditions. Finding a link between biotic ecological interactions across generations and plasticity in flower color would indicate that transgenerational effects of ecological interactions, such as herbivory, might be involved in flower color evolution. We conducted controlled experiments across four generations of wild radish ( Raphanus sativus , Brassicaceae) plants to explore whether flower color is influenced by herbivory, and to determine whether flower color is associated with transgenerational chromatin modifications. We found transgenerational effects of herbivory on flower color, partly related to chromatin modifications. Given the presence of herbivory in plant populations worldwide, our results are of broad significance and contribute to our understanding of flower color evolution.
Journal Article