scholarly journals Decline towards extinction of Mexico's vaquita porpoise ( Phocoena sinus )

2019 ◽  
Vol 6 (7) ◽  
pp. 190598 ◽  
Author(s):  
Armando M. Jaramillo-Legorreta ◽  
Gustavo Cardenas-Hinojosa ◽  
Edwyna Nieto-Garcia ◽  
Lorenzo Rojas-Bracho ◽  
Len Thomas ◽  
...  
Keyword(s):  
Population Size ◽  
Total Population ◽  
Population Decline ◽  
Credible Interval ◽  
Critically Endangered ◽  
Posterior Mean ◽  
Bayesian Credible Interval ◽  
Independent Estimate ◽  
Rate Of Decline ◽  
Passive Acoustic

The vaquita ( Phocoena sinus ) is a small porpoise endemic to Mexico. It is listed by IUCN as Critically Endangered because of unsustainable levels of bycatch in gillnets. The population has been monitored with passive acoustic detectors every summer from 2011 to 2018; here we report results for 2017 and 2018. We combine the acoustic trends with an independent estimate of population size from 2015, and visual observations of at least seven animals in 2017 and six in 2018. Despite adoption of an emergency gillnet ban in May 2015, the estimated rate of decline remains extremely high: 48% decline in 2017 (95% Bayesian credible interval (CRI) 78% decline to 9% increase) and 47% in 2018 (95% CRI 80% decline to 13% increase). Estimated total population decline since 2011 is 98.6%, with greater than 99% probability the decline is greater than 33% yr −1 . We estimate fewer than 19 vaquitas remained as of summer 2018 (posterior mean 9, median 8, 95% CRI 6–19). From March 2016 to March 2019, 10 dead vaquitas killed in gillnets were found. The ongoing presence of illegal gillnets despite the emergency ban continues to drive the vaquita towards extinction. Immediate management action is required if the species is to be saved.

scholarly journals Severe inbreeding and gene loss in the historical and extant population of the critically endangered Devils Hole pupfish

2021 ◽  
Author(s):  
David Tian ◽  
Bruce J. Turner ◽  
Christopher Herbert Martin
Keyword(s):  
Population Size ◽  
Stop Codon ◽  
Population Decline ◽  
Critically Endangered ◽  
Hypoxia Tolerance ◽  
Mitochondrial Activity ◽  
Low Oxygen ◽  
Genetic Rescue ◽  
A Genome ◽  
Devils Hole

Small populations with limited geographic distributions are predicted to be threatened by inbreeding and lack of genetic diversity, both of which may negatively impact fitness and exacerbate population decline. One of the most extreme natural examples is the Devils Hole pupfish (Cyprinodon diabolis), an iconic and critically endangered species with the smallest known habitat range of any vertebrate. This imperiled species has experienced severe declines in population size over the last thirty years and suffered major, repeated bottlenecks in 2007 and 2013, when the population sunk to 38 and 35 individuals, respectively. Here we sequenced contemporary and historical genomes of Devils Hole and neighboring Death Valley and Ash Meadows desert pupfishes to examine the genomic consequences of small population size. We found extreme inbreeding (FROH = 0.71 - 0.82) and increased genetic load in the Devils Hole pupfish. We also document unique fixed loss-of-function (LOF) alleles and deletions in genes associated with sperm motility, stress, and hypoxia within the extant Devils Hole pupfish population that likely reduce fitness. Comparisons between contemporary samples (2008 - 2012) and a genome sequenced from a 1980 formalin-fixed museum specimen suggest that inbreeding has increased 6% as the population has declined, but that many putatively deleterious variants have been segregating in the population since at least 1980. This includes a fixed early stop codon in cfap43 (n = 8/8 samples), which is associated with sperm flagellum defects and causes infertility in humans and mice. Out of ninety-four unique deletions, fifteen were detected within 2 kb of annotated genes. Five have roles in physiological responses to hypoxia and mitochondrial activity, such as redd1 (n = 7/7 samples), suggesting impaired hypoxia tolerance in this species despite the low oxygen concentrations of Devils Hole. We thus document one of the most extreme inbreeding events in a natural population and a set of candidate deleterious variants to inform management and potential genetic rescue in this conservation icon.

scholarly journals Genomic consequences of population decline in critically endangered pangolins and their demographic histories

2020 ◽  
Vol 7 (4) ◽  
pp. 798-814 ◽  
Author(s):  
Jing-Yang Hu ◽  
Zi-Qian Hao ◽  
Laurent Frantz ◽  
Shi-Fang Wu ◽  
Wu Chen ◽  
...  
Keyword(s):  
Population Size ◽  
Human Activities ◽  
Environmental Changes ◽  
De Novo ◽  
Population Decline ◽  
Cholesterol Homeostasis ◽  
Critically Endangered ◽  
Conservation Units ◽  
High Quality ◽  
Reference Genomes

Abstract Pangolins are among the most critically endangered animals due to heavy poaching and worldwide trafficking. However, their demographic histories and the genomic consequences of their recent population declines remain unknown. We generated high-quality de novo reference genomes for critically endangered Malayan (Manis javanica, MJ) and Chinese (M. pentadactyla, MP) pangolins and re-sequencing population genomic data from 74 MJs and 23 MPs. We recovered the population identities of illegally traded pangolins and previously unrecognized genetic populations that should be protected as evolutionarily distinct conservation units. Demographic reconstruction suggested environmental changes have resulted in a population size fluctuation of pangolins. Additionally, recent population size declines due to human activities have resulted in an increase in inbreeding and genetic load. Deleterious mutations were enriched in genes related to cancer/diseases and cholesterol homeostasis, which may have increased their susceptibility to diseases and decreased their survival potential to adapt to environmental changes and high-cholesterol diets. This comprehensive study provides not only high-quality pangolin reference genomes, but also valuable information concerning the driving factors of long-term population size fluctuations and the genomic impact of recent population size declines due to human activities, which is essential for pangolin conservation management and global action planning.

scholarly journals Population decline of the Eurasian Curlew in Akershus (southeastern Norway)

2019 ◽  
Vol 42 ◽  
pp. 19-27
Author(s):  
Melissa Monthouel ◽  
Svein Dale
Keyword(s):  
Population Size ◽  
Nest Predation ◽  
Large Scale ◽  
Population Decline ◽  
Agricultural Practices ◽  
Population Size Estimate ◽  
Historical Observation ◽  
Rate Of Decline ◽  
Yearly Rate ◽  
Near Threatened

The Eurasian Curlew (Numenius arquata) is a species in decline, classified as near threatened (NT) worldwide, and vulnerable (VU) in Norway. In Akershus county, southeastern Norway, the population of breeding Eurasian Curlews was estimated at 50-60 pairs in 1982. No recent update exists of this population size estimate. In this study, we assessed the population size in 2017 in Akershus, and examined how the population size changed between 1971 and 2017 by using historical observation records of Eurasian Curlews. We estimated that there were 30 territories in Akershus in 2017 and found that the population declined by 47% since 1995 and 77% since 1971. In the period 1995-2017, the yearly rate of decline was 2.8%. We discuss possible reasons for the decline, such as intensive agricultural practices, high nest predation rates, and large-scale threats on the wintering grounds.

scholarly journals Assessing population size of the Chestnut-Capped Foliage-Gleaner

2012 ◽  
Vol 52 (24) ◽  
pp. 281-290
Author(s):  
Luciene Faria ◽  
Lucas A. Carrara ◽  
Frederico I. Garcia ◽  
Marcos Rodrigues
Keyword(s):  
Population Size ◽  
Geographic Distribution ◽  
Total Population ◽  
Conservation Status ◽  
Population Decline ◽  
Primary Objective ◽  
Habitat Destruction ◽  
Population Fluctuations ◽  
Total Population Size ◽  
Iucn Criteria

Chestnut-Capped Foliage-Gleaner (Hylocryptus rectirostris) is a Neotropical ovenbird species (Furnariidae) endemic to gallery forests of the Cerrado region of central Brazil. While it is not considered globally threatened, the degree of habitat loss occurring throughout much of its known distribution may warrant its inclusion on red lists beyond just the state of Sao Paulo. The primary objective of this study is to evaluate the conservation status of Chestnut-Capped Foliage-Gleaner according to those criteria adopted by the IUCN. Results of censuses conducted in the Serra do Cipó National Park were used to estimate the entire population size of the Chestnut-Capped Foliage-Gleaner and refine our understanding of its actual geographic distribution. Census results indicate that the species has a population density of 3.8 pairs/100 ha and occupies only a quarter of its preferred habitat in the study area, which is well below the carrying capacity. The total population size estimate, accounting for its entire extent of known occurrence, is just over 54,000 pairs. The geographic distribution and total population size estimated in this study do not indicate that the Chestnut-Capped Foliage-Gleaner should be considered a threatened species according to IUCN criteria. However, it was not possible to evaluate this species’ conservation status based on information concerning population fluctuations over time, another of the IUCN criteria. Nonetheless, the rate of habitat destruction in the Cerrado during the last century has certainly resulted in a population decline of greater than 10%, a factor sufficient enough to warrant its inclusion in the IUCN category of vulnerable.

Drastic decline in the endemic brown shrike subspecies Lanius cristatus superciliosus in Japan

2020 ◽  
pp. 1-9
Author(s):  
MUNEHIRO KITAZAWA ◽  
MASAYUKI SENZAKI ◽  
HIROAKI MATSUMIYA ◽  
SEIICHI HARA ◽  
HARUKA MIZUMURA
Keyword(s):  
Population Size ◽  
Total Population ◽  
Population Decline ◽  
Nationwide Survey ◽  
Conservation Strategies ◽  
Past Century ◽  
Breeding Range ◽  
Breeding Habitats ◽  
The Status ◽  
Effective Conservation

Summary The Brown Shrike Lanius cristatus breeds across a large portion of eastern Asia. One subspecies, L. c. superciliosus, is primarily endemic to Japan and was historically abundant throughout its breeding range. However, both local- and broad-scale studies documented a drastic population decline between the 1970s and 1990s, and the status of the taxon is currently unavailable in Japan. We conducted a nationwide survey to estimate the current population size and breeding range of this subspecies within Japan. We further compared our findings to the historical breeding ranges through a literature review. The total population size was estimated at 149 breeding pairs, and the current breeding range was estimated at 6,800 km2, indicating a 90.9% range contraction over the past century. Our study highlights the urgency of protecting remaining breeding habitats and establishing effective conservation strategies for L. c. superciliosus.

scholarly journals Population estimates and habitat use by the Critically Endangered Taita Apalis Apalis fuscigularis in south-eastern Kenya

2010 ◽  
Vol 20 (4) ◽  
pp. 440-455 ◽  
Author(s):  
LUCA BORGHESIO ◽  
DAINA SAMBA ◽  
MWANGI GITHIRU ◽  
LEON BENNUN ◽  
KEN NORRIS
Keyword(s):  
Habitat Use ◽  
Population Size ◽  
Habitat Structure ◽  
Predictive Power ◽  
Total Population ◽  
Distance Sampling ◽  
Critically Endangered ◽  
South Eastern ◽  
Forest Sites ◽  
Global Population

SummaryThe Taita Apalis Apalis fuscigularis (IUCN category: Critically Endangered) is a species endemic to south-eastern Kenya. We assessed population size and habitat use in the three forest sites in which it is known to occur (Ngangao, Chawia and Vuria, totalling 257 ha). The estimate of total population size, derived from distance sampling at 412 sample points, ranged from 310 to 654 individuals, with the northern section of Ngangao fragment having 10-fold higher densities than Chawia (2.47–4.93 versus 0.22–0.41 birds ha−1). Ngangao north alone hosted 50% of the global population of the species. The highly degraded Vuria fragment also had moderately high densities (1.63–3.72 birds ha−1) suggesting that the species tolerates some human disturbance. Taita Apalis prefers vegetation with abundant climbers, but the predictive power of habitat use models was low, suggesting that habitat structure is not a primary cause for the low density of the species in Chawia. Protecting the subpopulation in the northern section of Ngangao is a priority, as is identifying factors responsible of the low abundance in Chawia, because ameliorating conditions in this large fragment could substantially increase the population of Taita Apalis.

scholarly journals Cost-efficient factors in local public spending: Detecting relationships between local environments, population size and urban area category

2021 ◽  
pp. 239980832110038
Author(s):  
Hiroki Baba ◽  
Yasushi Asami
Keyword(s):  
Population Size ◽  
Urban Area ◽  
Urban Areas ◽  
Local Governments ◽  
Statistical Significance ◽  
Population Decline ◽  
Public Spending ◽  
Local Environment ◽  
Environment Factors ◽  
Major Factors

This study examines regional differences in local environment factors to better understand the sustainability of local governments indexed by per capita public spending. Under the condition of heterogeneous population size, we examine how factor characteristics differ depending on the spatial context represented by the urban area category. By employing a Cobb–Douglas cost function with congestion effects on public service provision, the estimated factors enable us to articulate major factors and differences in cost-efficiency between urban area categories. We found that statistical significance and even the signatures of local environment factors differ depending on the urban employment area category. Regarding factors such as the ratios of employees in secondary and tertiary industries, these did not tend to be statistically significant in small-sized urban areas, while small-sized cities in large-sized urban areas were likely to gain confidence intervals. Moreover, we did not observe any statistical significance for the ratio of elderly people due to the balance of spending between national and local governments. These findings could contribute to sustainable management of cities in the advent of population decline.

scholarly journals Microsatellite analysis reveals low genetic diversity in managed populations of the critically endangered gharial (Gavialis gangeticus) in India

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Surya Prasad Sharma ◽  
Mirza Ghazanfarullah Ghazi ◽  
Suyash Katdare ◽  
Niladri Dasgupta ◽  
Samrat Mondol ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Indian Subcontinent ◽  
Population Decline ◽  
Mitochondrial Control Region ◽  
Critically Endangered ◽  
Term Survival ◽  
Low Level ◽  
Genetic Status ◽  
In The Wild ◽  
Gavialis Gangeticus

AbstractThe gharial (Gavialis gangeticus) is a critically endangered crocodylian, endemic to the Indian subcontinent. The species has experienced severe population decline during the twentieth century owing to habitat loss, poaching, and mortalities in passive fishing. Its extant populations have largely recovered through translocation programmes initiated in 1975. Understanding the genetic status of these populations is crucial for evaluating the effectiveness of the ongoing conservation efforts. This study assessed the genetic diversity, population structure, and evidence of genetic bottlenecks of the two managed populations inhabiting the Chambal and Girwa Rivers, which hold nearly 80% of the global gharial populations. We used seven polymorphic nuclear microsatellite loci and a 520 bp partial fragment of the mitochondrial control region (CR). The overall mean allelic richness (Ar) was 2.80 ± 0.40, and the observed (Ho) and expected (He) heterozygosities were 0.40 ± 0.05 and 0.39 ± 0.05, respectively. We observed low levels of genetic differentiation between populations (FST = 0.039, P < 0.05; G’ST = 0.058, P < 0.05 Jost’s D = 0.016, P < 0.05). The bottleneck analysis using the M ratio (Chambal = 0.31 ± 0.06; Girwa = 0.41 ± 0.12) suggested the presence of a genetic bottleneck in both populations. The mitochondrial CR also showed a low level of variation, with two haplotypes observed in the Girwa population. This study highlights the low level of genetic diversity in the two largest managed gharial populations in the wild. Hence, it is recommended to assess the genetic status of extant wild and captive gharial populations for planning future translocation programmes to ensure long-term survival in the wild.

scholarly journals Social structure and demography of a remnant Asian elephant Elephas maximus population and the implications for survival

Oryx ◽  
2020 ◽  
pp. 1-6
Author(s):  
Lauren J. Hale ◽  
Kun Shi ◽  
Tania C. Gilbert ◽  
Kelvin S.-H. Peh ◽  
Philip Riordan
Keyword(s):  
Social Structure ◽  
Population Size ◽  
Total Population ◽  
Camera Traps ◽  
Asian Elephant ◽  
Elephas Maximus ◽  
Effective Density ◽  
Anthropogenic Pressures ◽  
Sex Ratio Bias ◽  
Elephant Population

Abstract The Asian elephant Elephas maximus is at risk of extinction as a result of anthropogenic pressures, and remaining populations are often small and fragmented remnants, occupying a fraction of the species' former range. Once widely distributed across China, only a maximum of 245 elephants are estimated to survive across seven small populations. We assessed the Asian elephant population in Nangunhe National Nature Reserve in Lincang Prefecture, China, using camera traps during May–July 2017, to estimate the population size and structure of this genetically important population. Although detection probability was low (0.31), we estimated a total population size of c. 20 individuals, and an effective density of 0.39 elephants per km2. Social structure indicated a strong sex ratio bias towards females, with only one adult male detected within the population. Most of the elephants associated as one herd but three adult females remained separate from the herd throughout the trapping period. These results highlight the fragility of remnant elephant populations such as Nangunhe and we suggest options such as a managed metapopulation approach for their continued survival in China and more widely.

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