scholarly journals Introgression between ecologically distinct species following increased salinity in the Colorado Delta- Worldwide implications for impacted estuary diversity

2017 ◽  
Author(s):  
Clive L.F. Lau ◽  
David K. Jacobs
Keyword(s):  
At Risk ◽  
Gulf Of California ◽  
Extinction Risk ◽  
Habitat Destruction ◽  
Sister Species ◽  
Past Century ◽  
Salinity Regime ◽  
Salinity Gradients ◽  
Evolutionary Response ◽  
Species Pairs

We investigate hybridization and introgression between ecologically distinct sister species of silverside fish in the Gulf of California through combined analysis of morphological, sequence, and genotypic data. Water diversions in the past century turned the Colorado River Delta from a normal estuary to a hypersaline inverse estuary, raising concerns for the local fauna, much of which is endangered. Salinity differences are known to generate ecological species pairs and we anticipated that loss of the fresher-water historic salinity regime could alter the adaptive factors maintaining distinction between the broadly distributed Gulf-endemic Colpichthys regis and the narrowly restricted Delta-endemic Colpichthis hubbsi, the species that experienced dramatic environmental change. In this altered environmental context, these long-isolated species (as revealed by Cytochrome b sequences) show genotypic (RAG1, microsatellites) evidence of active hybridization where the species ranges abut, as well as directional introgression from C. regis into the range center of C. hubbsi. Bayesian group assignment (STRUCTURE) on six microsatellite loci and multivariate analyses (DAPC) on both microsatellites and phenotypic data further support substantial recent admixture between the sister species. Although we find no evidence for recent population decline in C. hubbsi based on mitochondrial sequence, introgression may be placing an ancient ecological species at risk of extinction. Such introgressive extinction risk should also pertain to a number of other ecological species historically sustained by the now changing Delta environment. More broadly, salinity gradient associated ecological speciation is evident in silverside species pairs in many estuarine systems around the world. Ecological species pairs among other taxa in such systems are likely poorly understood or cryptic. As water extraction accelerates in river systems worldwide, salinity gradients will necessarily be altered, impacting many more estuary and delta systems. Such alteration of habitats will place biodiversity at risk not only from direct effects of habitat destruction, but also from the potential for the breakdown of ecological species. Thus, evolutionary response to the anthropogenic alteration of salinity gradients in estuaries merits investigation as the number of impacted systems increases around the globe, permitting parallel study of multiple systems, while also permitting a conservation management response to help preserve this little championed component of biodiversity.

scholarly journals Introgression between ecologically distinct species following increased salinity in the Colorado Delta- Worldwide implications for impacted estuary diversity

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e4056 ◽  
Author(s):  
Clive L.F. Lau ◽  
David K. Jacobs
Keyword(s):  
At Risk ◽  
Gulf Of California ◽  
Extinction Risk ◽  
Habitat Destruction ◽  
Sister Species ◽  
Past Century ◽  
Salinity Regime ◽  
Salinity Gradients ◽  
Evolutionary Response ◽  
Species Pairs

We investigate hybridization and introgression between ecologically distinct sister species of silverside fish in the Gulf of California through combined analysis of morphological, sequence, and genotypic data. Water diversions in the past century turned the Colorado River Delta from a normal estuary to a hypersaline inverse estuary, raising concerns for the local fauna, much of which is endangered. Salinity differences are known to generate ecological species pairs and we anticipated that loss of the fresher-water historic salinity regime could alter the adaptive factors maintaining distinction between the broadly distributed Gulf-endemicColpichthys regisand the narrowly restricted Delta-endemicColpichthys hubbsi, the species that experienced dramatic environmental change. In this altered environmental context, these long-isolated species (as revealed by Cytochromebsequences) show genotypic (RAG1, microsatellites) evidence of active hybridization where the species ranges abut, as well as directional introgression fromC. regisinto the range center ofC. hubbsi. Bayesian group assignment (STRUCTURE) on six microsatellite loci and multivariate analyses (DAPC) on both microsatellites and phenotypic data further support substantial recent admixture between the sister species. Although we find no evidence for recent population decline inC. hubbsibased on mitochondrial sequence, introgression may be placing an ancient ecological species at risk of extinction. Such introgressive extinction risk should also pertain to other ecological species historically sustained by the now changing Delta environment. More broadly, salinity gradient associated ecological speciation is evident in silverside species pairs in many estuarine systems around the world. Ecological species pairs among other taxa in such systems are likely poorly understood or cryptic. As water extraction accelerates in river systems worldwide, salinity gradients will necessarily be altered, impacting many more estuary and delta systems. Such alteration of habitats will place biodiversity at risk not only from direct effects of habitat destruction, but also from the potential for the breakdown of ecological species. Thus, evolutionary response to the anthropogenic alteration of salinity gradients in estuaries merits investigation as the number of impacted systems increases around the globe, permitting parallel study of multiple systems, while also permitting a conservation management response to help preserve this little championed component of biodiversity.

scholarly journals Introgression between ecologically distinct species following increased salinity in the Colorado Delta- Worldwide implications for impacted estuary diversity

2017 ◽  
Author(s):  
Clive L.F. Lau ◽  
David K. Jacobs
Keyword(s):  
At Risk ◽  
Gulf Of California ◽  
Extinction Risk ◽  
Habitat Destruction ◽  
Sister Species ◽  
Past Century ◽  
Salinity Regime ◽  
Salinity Gradients ◽  
Evolutionary Response ◽  
Species Pairs

We investigate hybridization and introgression between ecologically distinct sister species of silverside fish in the Gulf of California through combined analysis of morphological, sequence, and genotypic data. Water diversions in the past century turned the Colorado River Delta from a normal estuary to a hypersaline inverse estuary, raising concerns for the local fauna, much of which is endangered. Salinity differences are known to generate ecological species pairs and we anticipated that loss of the fresher-water historic salinity regime could alter the adaptive factors maintaining distinction between the broadly distributed Gulf-endemic Colpichthys regis and the narrowly restricted Delta-endemic Colpichthis hubbsi, the species that experienced dramatic environmental change. In this altered environmental context, these long-isolated species (as revealed by Cytochrome b sequences) show genotypic (RAG1, microsatellites) evidence of active hybridization where the species ranges abut, as well as directional introgression from C. regis into the range center of C. hubbsi. Bayesian group assignment (STRUCTURE) on six microsatellite loci and multivariate analyses (DAPC) on both microsatellites and phenotypic data further support substantial recent admixture between the sister species. Although we find no evidence for recent population decline in C. hubbsi based on mitochondrial sequence, introgression may be placing an ancient ecological species at risk of extinction. Such introgressive extinction risk should also pertain to a number of other ecological species historically sustained by the now changing Delta environment. More broadly, salinity gradient associated ecological speciation is evident in silverside species pairs in many estuarine systems around the world. Ecological species pairs among other taxa in such systems are likely poorly understood or cryptic. As water extraction accelerates in river systems worldwide, salinity gradients will necessarily be altered, impacting many more estuary and delta systems. Such alteration of habitats will place biodiversity at risk not only from direct effects of habitat destruction, but also from the potential for the breakdown of ecological species. Thus, evolutionary response to the anthropogenic alteration of salinity gradients in estuaries merits investigation as the number of impacted systems increases around the globe, permitting parallel study of multiple systems, while also permitting a conservation management response to help preserve this little championed component of biodiversity.

scholarly journals Prevalence of disruptive selection predicts extent of species differentiation in Lake Victoria cichlids

2018 ◽  
Vol 285 (1871) ◽  
pp. 20172630 ◽  
Author(s):  
Jacco C. van Rijssel ◽  
Florian N. Moser ◽  
David Frei ◽  
Ole Seehausen
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
Genetic Differentiation ◽  
Lake Victoria ◽  
Sister Species ◽  
Disruptive Selection ◽  
Nuptial Coloration ◽  
Ecological Selection ◽  
Evolutionary Response ◽  
Species Pairs

Theory suggests that speciation with gene flow is most likely when both sexual and ecological selection are divergent or disruptive. Divergent sexual and natural selection on the visual system have been demonstrated before in sympatric, morphologically similar sister species of Lake Victoria cichlids, but this does not explain the subtle morphological differences between them. To investigate the significance of natural selection on morphology during speciation, we here ask whether the prevalence of disruptive ecological selection differs between sympatric sister species that are at different stages of speciation. Some of our species pairs do ( Pundamilia ) and others do not ( Neochromis ) differ distinctively in sexually selected male nuptial coloration. We find that (i) evidence for disruptive selection, and for evolutionary response to it, is prevalent in traits that are differentiated between sister species; (ii) prevalence of both predicts the extent of genetic differentiation; and (iii) genetic differentiation is weaker in species pairs with conserved male nuptial coloration. Our results speak to the existence of two different mechanisms of speciation with gene flow: speciation mainly by sexual selection tightly followed by ecological character displacement in some cases and speciation mainly by divergent ecological selection in others.

Using evidence of decline and extinction risk to identify priority regions, habitats and threats for plant conservation in Australia

2018 ◽  
Vol 66 (7) ◽  
pp. 541 ◽  
Author(s):  
J. L. Silcock ◽  
R. J. Fensham
Keyword(s):  
At Risk ◽  
Threatened Species ◽  
Extinction Risk ◽  
Plant Conservation ◽  
State Legislation ◽  
Risk Of Extinction ◽  
The Status ◽  
Species Lists ◽  
Key Issues ◽  
Efficient Recovery

Threatened species lists are used at global, national and regional scales to identify species at risk of extinction. Many species are listed due to restricted population size or geographic distribution, and decline is often inferred rather than quantified. Vascular plants comprise over 70% of nationally listed threatened species, but there is an incomplete picture of which species are most at risk of extinction, where these occur and the factors behind their declines. We compiled published information and the best available field knowledge including 125 expert interviews to identify declining and at risk species. The candidate list comprised 1135 taxa, which were mostly listed as Critically Endangered or Endangered under Federal and/or State legislation, but included 80 that are currently unlisted but considered to be highly threatened. In total, 418 taxa were assessed as having a documented, suspected or projected continuing decline. These were ranked based on extinction risk and magnitude of continuing decline, which suggest that 296 are at risk of extinction under current management regimes, including 55 at high risk of extinction. Declining and imperilled taxa are concentrated in a relatively small number of regions and habitats, and six threatening processes are driving the majority of declines. Field surveys and robust, repeatable monitoring are required to better inform population trends and extinction risk, as well as inform the status of almost 200 taxa that are potentially imperilled but poorly known. Identification of declining taxa can identify key issues for flora conservation across a continent, and allow for targeted and efficient recovery efforts.

scholarly journals Predicting how populations decline to extinction

2011 ◽  
Vol 366 (1577) ◽  
pp. 2577-2586 ◽  
Author(s):  
Ben Collen ◽  
Louise McRae ◽  
Stefanie Deinet ◽  
Adriana De Palma ◽  
Tharsila Carranza ◽  
...  
Keyword(s):  
At Risk ◽  
Extinction Risk ◽  
Mammalian Species ◽  
Local Population ◽  
Population Decline ◽  
Scale Up ◽  
Population Level ◽  
Biological Traits ◽  
Population Declines ◽  
Trend Data

Global species extinction typically represents the endpoint in a long sequence of population declines and local extinctions. In comparative studies of extinction risk of contemporary mammalian species, there appear to be some universal traits that may predispose taxa to an elevated risk of extinction. In local population-level studies, there are limited insights into the process of population decline and extinction. Moreover, there is still little appreciation of how local processes scale up to global patterns. Advancing the understanding of factors which predispose populations to rapid declines will benefit proactive conservation and may allow us to target at-risk populations as well as at-risk species. Here, we take mammalian population trend data from the largest repository of population abundance trends, and combine it with the PanTHERIA database on mammal traits to answer the question: what factors can be used to predict decline in mammalian abundance? We find in general that environmental variables are better determinants of cross-species population-level decline than intrinsic biological traits. For effective conservation, we must not only describe which species are at risk and why, but also prescribe ways to counteract this.

scholarly journals Integrating bioclimate with population models to improve forecasts of species extinctions under climate change

2009 ◽  
Vol 5 (6) ◽  
pp. 723-725 ◽  
Author(s):  
Barry W. Brook ◽  
H. Resit Akçakaya ◽  
David A. Keith ◽  
Georgina M. Mace ◽  
Richard G. Pearson ◽  
...  
Keyword(s):  
Climate Change ◽  
Case Studies ◽  
Population Change ◽  
Global Climate ◽  
Extinction Risk ◽  
International Workshop ◽  
Habitat Destruction ◽  
Species Specific ◽  
The Uk ◽  
The University

Climate change is already affecting species worldwide, yet existing methods of risk assessment have not considered interactions between demography and climate and their simultaneous effect on habitat distribution and population viability. To address this issue, an international workshop was held at the University of Adelaide in Australia, 25–29 May 2009, bringing leading species distribution and population modellers together with plant ecologists. Building on two previous workshops in the UK and Spain, the participants aimed to develop methodological standards and case studies for integrating bioclimatic and metapopulation models, to provide more realistic forecasts of population change, habitat fragmentation and extinction risk under climate change. The discussions and case studies focused on several challenges, including spatial and temporal scale contingencies, choice of predictive climate, land use, soil type and topographic variables, procedures for ensemble forecasting of both global climate and bioclimate models and developing demographic structures that are realistic and species-specific and yet allow generalizations of traits that make species vulnerable to climate change. The goal is to provide general guidelines for assessing the Red-List status of large numbers of species potentially at risk, owing to the interactions of climate change with other threats such as habitat destruction, overexploitation and invasive species.

scholarly journals Evaluating firefly extinction risk: Initial red list assessments for North America

PLoS ONE ◽  
2021 ◽  
Vol 16 (11) ◽  
pp. e0259379
Author(s):  
Candace E. Fallon ◽  
Anna C. Walker ◽  
Sara Lewis ◽  
Joseph Cicero ◽  
Lynn Faust ◽  
...  
Keyword(s):  
At Risk ◽  
North America ◽  
Extinction Risk ◽  
The United States ◽  
Iucn Red List ◽  
Red List ◽  
Future Research ◽  
Habitat Specificity ◽  
Data Deficient ◽  
Systematic Compilation

Fireflies are a family of charismatic beetles known for their bioluminescent signals. Recent anecdotal reports suggest that firefly populations in North America may be in decline. However, prior to this work, no studies have undertaken a systematic compilation of geographic distribution, habitat specificity, and threats facing North American fireflies. To better understand their extinction risks, we conducted baseline assessments according to the categories and criteria of the International Union for Conservation of Nature (IUCN) Red List for 132 species from the United States and Canada (approximately 79% of described species in the region). We found at least 18 species (14%) are threatened with extinction (e.g. categorized as Critically Endangered, Endangered, or Vulnerable) due to various pressures, including habitat loss, light pollution, and climate change (sea level rise and drought). In addition, more than half of the species (53%) could not be evaluated against the assessment criteria due to insufficient data, highlighting the need for further study. Future research and conservation efforts should prioritize monitoring and protecting populations of at-risk species, preserving and restoring habitat, gathering data on population trends, and filling critical information gaps for data deficient species suspected to be at risk.

scholarly journals A management plan for a declining population of the Souss valley tortoise in an arid steppe-land of west-central Morocco

2021 ◽  
Author(s):  
Hichami Nawal ◽  
MOHAMMED ZNARI
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Extinction Risk ◽  
Management Plan ◽  
Habitat Destruction ◽  
North West ◽  
West Central ◽  
Arid Steppe ◽  
The Impact

The endangered Moorish tortoise Testudo graeca is the unique terrestrial chelonian species in North-west Africa. In west-central Morocco, the endemic subspecies, the Souss valley tortoise T. g. soussensis, occupies semi-arid to arid low-quality habitats, and is subject to serious threats. A long-term mark-recapture programme from 2001 to 2012 allowed estimating population size and structure, sex ratio, and survivorship in one of the well-known populations in a degraded and overgrazed arid steppe-land of west-central Morocco. Spring population size considerably decreased to more than half in less than 10 years, with a mean density lower than 3 ind.ha-1 in 2012 compared to its last known density estimat-ed in 2003. In spring 2012, the population structure exhibited an unbalanced male-biased sex ratio (61:39) and a scarcity of juveniles (<5%). We identified five major conservation problems in the study area: (i) habitat destruction and overgrazing; (ii) over-collecting of tortoises for pet trade , iii) direct dis-turbance; iv) tortoise handling mostly for field research, and v) increased extinction risk due to the small population size. We carried out a population viability analysis using the VORTEX software based on published and obtained data on population and life history parameters. With no management action, the population will go extinct during the forthcoming 40 years after the last estimate. The most efficient management option for a long-term persistence of the population would be reducing the nest and neo-nate mortality by 90%. To attenuate the impact of the threatening factors, we developed a management plan that includes population reinforcement and habitat restoration options. 

scholarly journals Data gaps and opportunities for comparative and conservation biology

2019 ◽  
Vol 116 (19) ◽  
pp. 9658-9664 ◽  
Author(s):  
Dalia A. Conde ◽  
Johanna Staerk ◽  
Fernando Colchero ◽  
Rita da Silva ◽  
Jonas Schöley ◽  
...  
Keyword(s):  
Life Histories ◽  
Extinction Risk ◽  
Average Rate ◽  
Demographic Data ◽  
Population Increase ◽  
Past Century ◽  
Population Declines ◽  
Background Rate ◽  
Death Rates ◽  
Data Gaps

Biodiversity loss is a major challenge. Over the past century, the average rate of vertebrate extinction has been about 100-fold higher than the estimated background rate and population declines continue to increase globally. Birth and death rates determine the pace of population increase or decline, thus driving the expansion or extinction of a species. Design of species conservation policies hence depends on demographic data (e.g., for extinction risk assessments or estimation of harvesting quotas). However, an overview of the accessible data, even for better known taxa, is lacking. Here, we present the Demographic Species Knowledge Index, which classifies the available information for 32,144 (97%) of extant described mammals, birds, reptiles, and amphibians. We show that only 1.3% of the tetrapod species have comprehensive information on birth and death rates. We found no demographic measures, not even crude ones such as maximum life span or typical litter/clutch size, for 65% of threatened tetrapods. More field studies are needed; however, some progress can be made by digitalizing existing knowledge, by imputing data from related species with similar life histories, and by using information from captive populations. We show that data from zoos and aquariums in the Species360 network can significantly improve knowledge for an almost eightfold gain. Assessing the landscape of limited demographic knowledge is essential to prioritize ways to fill data gaps. Such information is urgently needed to implement management strategies to conserve at-risk taxa and to discover new unifying concepts and evolutionary relationships across thousands of tetrapod species.

Review of the Nearctic Lonchopteridae (Diptera), including descriptions of three new species

2008 ◽  
Vol 140 (6) ◽  
pp. 649-673 ◽  
Author(s):  
John Klymko ◽  
S.A. Marshall
Keyword(s):  
British Columbia ◽  
New Species ◽  
Northwest Territories ◽  
New Hampshire ◽  
Phylogenetic Relationships ◽  
Junior Synonym ◽  
Sister Species ◽  
Distribution Maps ◽  
Species Pairs ◽  
Three New Species

AbstractThe Nearctic species of Lonchoptera Meigen are reviewed, including three new species: L. barberi Klymko sp. nov. from Manitoba, Newfoundland, Ontario, Quebec, Iowa, Michigan, Minnesota, and New Hampshire, L. megaloba Klymko sp. nov. from British Columbia and California, and L. longiphallus Klymko sp. nov. from British Columbia and the Northwest Territories. Lonchoptera borealis Curran is proposed as a new junior synonym of L. impicta Zetterstedt, and L. occidentalis Curran is proposed as a new junior synonym of L. uniseta Curran. Lonchoptera nigrociliata Duda, formerly known only from the Palaearctic Region, is recorded from the Yukon and Alaska. Descriptions, a key, and Nearctic distribution maps are presented. Phylogenetic relationships are briefly discussed and two sister species pairs are documented.

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