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Charmouh AP, Reid JM, Bilde T, Bocedi G. Eco-evolutionary extinction and recolonization dynamics reduce genetic load and increase time to extinction in highly inbred populations. Evolution 2022; 76:2482-2497. [PMID: 36117269 PMCID: PMC9828521 DOI: 10.1111/evo.14620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 06/01/2022] [Accepted: 07/11/2022] [Indexed: 01/22/2023]
Abstract
Understanding how genetic and ecological effects can interact to shape genetic loads within and across local populations is key to understanding ongoing persistence of systems that should otherwise be susceptible to extinction through mutational meltdown. Classic theory predicts short persistence times for metapopulations comprising small local populations with low connectivity, due to accumulation of deleterious mutations. Yet, some such systems have persisted over evolutionary time, implying the existence of mechanisms that allow metapopulations to avoid mutational meltdown. We first hypothesize a mechanism by which the combination of stochasticity in the numbers and types of mutations arising locally (genetic stochasticity), resulting local extinction, and recolonization through evolving dispersal facilitates metapopulation persistence. We then test this mechanism using a spatially and genetically explicit individual-based model. We show that genetic stochasticity in highly structured metapopulations can result in local extinctions, which can favor increased dispersal, thus allowing recolonization of empty habitat patches. This causes fluctuations in metapopulation size and transient gene flow, which reduces genetic load and increases metapopulation persistence over evolutionary time. Our suggested mechanism and simulation results provide an explanation for the conundrum presented by the continued persistence of highly structured populations with inbreeding mating systems that occur in diverse taxa.
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Affiliation(s)
- Anders P. Charmouh
- School of Biological SciencesUniversity of AberdeenAberdeenAB24 2TZUnited Kingdom
| | - Jane M. Reid
- School of Biological SciencesUniversity of AberdeenAberdeenAB24 2TZUnited Kingdom,Centre for Biodiversity DynamicsInstitutt for Biologi, NTNUTrondheim7491Norway
| | - Trine Bilde
- Department of BiologyAarhus UniversityAarhus C8000Denmark
| | - Greta Bocedi
- School of Biological SciencesUniversity of AberdeenAberdeenAB24 2TZUnited Kingdom
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Yannic G, Helfer V, Sermier R, Schmidt BR, Fumagalli L. Fine scale genetic structure in fire salamanders (Salamandra salamandra) along a rural-to-urban gradient. CONSERV GENET 2021. [DOI: 10.1007/s10592-021-01335-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Demography, genetics, and decline of a spatially structured population of lekking bird. Oecologia 2021; 195:117-129. [PMID: 33392789 DOI: 10.1007/s00442-020-04808-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 11/16/2020] [Indexed: 10/22/2022]
Abstract
Understanding the mechanisms underlying population decline is a critical challenge for conservation biologists. Both deterministic (e.g. habitat loss, fragmentation, and Allee effect) and stochastic (i.e. demographic and environmental stochasticity) demographic processes are involved in population decline. Simultaneously, a decrease of population size has far-reaching consequences for genetics of populations by increasing the risk of inbreeding and the strength of genetic drift, which together inevitably results in a loss of genetic diversity and a reduced effective population size ([Formula: see text]). These genetic factors may retroactively affect vital rates (a phenomenon coined 'inbreeding depression'), reduce population growth, and accelerate demographic decline. To date, most studies that have examined the demographic and genetic processes driving the decline of wild populations have neglected their spatial structure. In this study, we examined demographic and genetic factors involved in the decline of a spatially structured population of a lekking bird, the western capercaillie (Tetrao urogallus). To address this issue, we collected capture-recapture and genetic data over a 6-years period in the Vosges Mountains (France). Our study showed that the population of T. urogallus experienced a severe decline between 2010 and 2015. We did not detect any Allee effect on survival and recruitment. By contrast, individuals of both sexes dispersed to avoid small subpopulations, thus suggesting a potential behavioral response to a mate finding Allee effect. In parallel to this demographic decline, the population showed low levels of genetic diversity, high inbreeding and low effective population sizes at both subpopulation and population levels. Despite this, we did not detect evidence of inbreeding depression: neither adult survival nor recruitment were affected by individual inbreeding level. Our study underlines the benefit from combining demographic and genetic approaches to investigate processes that are involved in population decline.
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Inbreeding reduces long-term growth of Alpine ibex populations. Nat Ecol Evol 2019; 3:1359-1364. [PMID: 31477848 DOI: 10.1038/s41559-019-0968-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Accepted: 07/26/2019] [Indexed: 11/08/2022]
Abstract
Many studies document negative inbreeding effects on individuals, and conservation efforts to preserve rare species routinely employ strategies to reduce inbreeding. Despite this, there are few clear examples in nature of inbreeding decreasing the growth rates of populations, and the extent of population-level effects of inbreeding in the wild remains controversial. Here, we take advantage of a long-term dataset of 26 reintroduced Alpine ibex (Capra ibex ibex) populations spanning nearly 100 years to show that inbreeding substantially reduced per capita population growth rates, particularly for populations in harsher environments. Populations with high average inbreeding (F ≈ 0.2) had population growth rates reduced by 71% compared with populations with no inbreeding. Our results show that inbreeding can have long-term demographic consequences even when environmental variation is large and deleterious alleles may have been purged during bottlenecks. Thus, efforts to guard against inbreeding effects in populations of endangered species have not been misplaced.
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Phylogeography and genetic effects of habitat fragmentation on endemic Urophysa (Ranunculaceae) in Yungui Plateau and adjacent regions. PLoS One 2017; 12:e0186378. [PMID: 29053749 PMCID: PMC5650156 DOI: 10.1371/journal.pone.0186378] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2017] [Accepted: 09/30/2017] [Indexed: 11/19/2022] Open
Abstract
Urophysa is a Chinese endemic genus with only two species (U. rockii and U. henryi) distributed in Yungui Plateau (Guizhou Province) and adjacent regions (i.e., Provinces of Hunan, Hubei, Chongqing and Sichuan). The aim of this study was to determine the genetic diversity and population differentiation within Urophysa and investigate the effect of the Yungui Plateau uplift and climate oscillations on evolution of Urophysa. In this study, micro-morphological characteristics, nine microsatellite loci (SSR), two nuclear loci (ITS and ETS) and two chloroplast fragments (psbA-trnH and trnL-trnF) were used to analyze the phylogenetic relationships and assess genetic and phylogeographical structure of Urophysa. Isolation by distance (IBD) was performed to research the effects of geographical isolation. We detected high genetic diversity at the species level but low genetic diversity within populations. Striking genetic differentiation (AMOVA) among populations and a significant phylogeographical structure (NST > GST, p < 0.01) were detected among U. henryi populations, along with significant effects of isolation by distance (IBD). Molecular clock estimation using calibration strategy and cpDNA substitution rate indicated that the divergence of U. henryi occurred during late Miocene to early Quaternary, when the orogeny of Yungui Plateau was violent. U. rockii originated at the early Quaternary and further differentiated at early Pleistocene. Our results suggested that habitat fragmentation played an important role in the genetic diversity and population differentiation of U. rockii and U. henryi. Heterogenous geomorphological configuration and complicated environment resulted from rapid uplift of the Yungui Plateau were inferred as important incentives for the modern phylogeograhpical pattern and species divergence of Urophysa. The geographical isolation, limited gene flow, specialized morphologies and the Pleistocene climatic oscillation greatly contributed to the allopatric divergence of U. rockii. Significant genetic drift and inbreeding were detected in these two species, in situ measures should be implemented to protect them.
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Natesh M, Atla G, Nigam P, Jhala YV, Zachariah A, Borthakur U, Ramakrishnan U. Conservation priorities for endangered Indian tigers through a genomic lens. Sci Rep 2017; 7:9614. [PMID: 28851952 PMCID: PMC5575265 DOI: 10.1038/s41598-017-09748-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 07/31/2017] [Indexed: 11/21/2022] Open
Abstract
Tigers have lost 93% of their historical range worldwide. India plays a vital role in the conservation of tigers since nearly 60% of all wild tigers are currently found here. However, as protected areas are small (<300 km2 on average), with only a few individuals in each, many of them may not be independently viable. It is thus important to identify and conserve genetically connected populations, as well as to maintain connectivity within them. We collected samples from wild tigers (Panthera tigris tigris) across India and used genome-wide SNPs to infer genetic connectivity. We genotyped 10,184 SNPs from 38 individuals across 17 protected areas and identified three genetically distinct clusters (corresponding to northwest, southern and central India). The northwest cluster was isolated with low variation and high relatedness. The geographically large central cluster included tigers from central, northeastern and northern India, and had the highest variation. Most genetic diversity (62%) was shared among clusters, while unique variation was highest in the central cluster (8.5%) and lowest in the northwestern one (2%). We did not detect signatures of differential selection or local adaptation. We highlight that the northwest population requires conservation attention to ensure persistence of these tigers.
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Affiliation(s)
- Meghana Natesh
- National Center for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, 560065, India. .,Shanmugha Arts, Science, Technology and Research Academy (SASTRA) University, Tirumalaisamudram, Thanjavur, 613401, Tamil Nadu, India.
| | - Goutham Atla
- National Center for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, 560065, India
| | - Parag Nigam
- Wildlife Institute of India, Chandrabani, Dehradun, 248001, India
| | | | - Arun Zachariah
- Kerala Veterinary and Animal Sciences University, Lakkidi Post, Pookode, Kerala, 673576, India
| | - Udayan Borthakur
- Aaranyak, 12 Kanaklata Path in Lachit Path, Ajanta Path, Survey, Beltola, Guwahati, 781028, Assam, India
| | - Uma Ramakrishnan
- National Center for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, 560065, India.
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Spigler RB, Theodorou K, Chang S. Inbreeding depression and drift load in small populations at demographic disequilibrium. Evolution 2016; 71:81-94. [DOI: 10.1111/evo.13103] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 10/11/2016] [Accepted: 10/13/2016] [Indexed: 11/27/2022]
Affiliation(s)
- Rachel B. Spigler
- Department of Biology Temple University 1900 N. 12th Street Philadelphia Pennsylvania 19122
| | - Konstantinos Theodorou
- Biodiversity Conservation Laboratory, Department of Environment, University of the Aegean University Hill 81100 Mytilene Greece
| | - Shu‐Mei Chang
- Department of Plant Biology University of Georgia 2502 Miller Plant Sciences Athens Georgia 30602–7271
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Henry RC, Coulon A, Travis JMJ. Dispersal asymmetries and deleterious mutations influence metapopulation persistence and range dynamics. Evol Ecol 2015. [DOI: 10.1007/s10682-015-9777-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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Méndez M, Vögeli M, Tella JL, Godoy JA. Joint effects of population size and isolation on genetic erosion in fragmented populations: finding fragmentation thresholds for management. Evol Appl 2014; 7:506-18. [PMID: 24822084 PMCID: PMC4001448 DOI: 10.1111/eva.12154] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 02/15/2014] [Indexed: 12/01/2022] Open
Abstract
Size and isolation of local populations are main parameters of interest when assessing the genetic consequences of habitat fragmentation. However, their relative influence on the genetic erosion of local populations remains unclear. In this study, we first analysed how size and isolation of habitat patches influence the genetic variation of local populations of the Dupont's lark (Chersophilus duponti), an endangered songbird. An information-theoretic approach to model selection allowed us to address the importance of interactions between habitat variables, an aspect seldom considered in fragmentation studies, but which explained up to 65% of the variance in genetic parameters. Genetic diversity and inbreeding were influenced by the size of local populations depending on their degree of isolation, and genetic differentiation was positively related to isolation. We then identified a minimum local population of 19 male territories and a maximum distance of 30 km to the nearest population as thresholds from which genetic erosion becomes apparent. Our results alert on possibly misleading conclusions and suboptimal management recommendations when only additive effects are taken into account and encourage the use of most explanatory but easy-to-measure variables for the evaluation of genetic risks in conservation programmes.
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Affiliation(s)
- María Méndez
- Estación Biológica de Doñana (EBD-CSIC) Sevilla, Spain
| | - Matthias Vögeli
- Estación Biológica de Doñana (EBD-CSIC) Sevilla, Spain ; Department of Biology, University of Saskatchewan Saskatoon, SK, Canada ; Schulstrasse 47, 5423, Freienwil, Switzerland
| | - José L Tella
- Estación Biológica de Doñana (EBD-CSIC) Sevilla, Spain
| | - José A Godoy
- Estación Biológica de Doñana (EBD-CSIC) Sevilla, Spain
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Wootton JT, Pfister CA. Experimental separation of genetic and demographic factors on extinction risk in wild populations. Ecology 2013; 94:2117-23. [PMID: 24358695 DOI: 10.1890/12-1828.1] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2024]
Abstract
When populations reach small size, an extinction risk vortex may arise from genetic (inbreeding depression, genetic drift) and ecological (demographic stochasticity, Allee effects, environmental fluctuation) processes. The relative contribution of these processes to extinction in wild populations is unknown, but important for conserving endangered species. In experimental field populations of a harvested kelp (Postelsia palmaeformis), in which we independently varied initial genetic diversity (completely inbred, control, outbred) and population size, ecological processes dominated the risk of extinction, whereas the contribution of genetic diversity was slight. Our results match theoretical predictions that demographic processes will generally doom small populations to extinction before genetic effects act strongly, prioritize detailed ecological analysis over descriptions of genetic structure in assessing conservation of at-risk species, and highlight the need for field experiments manipulating both demographics and genetic structure on long-term extinction risk.
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Affiliation(s)
- J Timothy Wootton
- Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago, IL 60637, USA.
| | - Catherine A Pfister
- Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago, IL 60637, USA
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Causes and evolutionary consequences of population subdivision of an Iberian mountain lizard, Iberolacerta monticola. PLoS One 2013; 8:e66034. [PMID: 23762459 PMCID: PMC3676366 DOI: 10.1371/journal.pone.0066034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Accepted: 05/06/2013] [Indexed: 11/30/2022] Open
Abstract
Aim The study of the factors that influence population connectivity and spatial distribution of genetic variation is crucial for understanding speciation and for predicting the effects of landscape modification and habitat fragmentation, which are considered severe threats to global biodiversity. This dual perspective is obtained from analyses of subalpine mountain species, whose present distribution may have been shaped both by cyclical climate changes over ice ages and anthropogenic perturbations of their habitats. Here, we examine the phylogeography, population structure and genetic diversity of the lacertid lizard Iberolacerta monticola, an endemism considered to be facing a high risk of extinction in several populations. Location Northwestern quadrant of the Iberian Peninsula. Methods We analyzed the mtDNA variation at the control region (454 bp) and the cytochrome b (598 bp) loci, as well as at 10 nuclear microsatellite loci from 17 populations throughout the distribution range of the species. Results According to nuclear markers, most sampling sites are defined as distinct, genetically differentiated populations, and many of them show traces of recent bottlenecks. Mitochondrial data identify a relatively old, geographically restricted lineage, and four to six younger geographically vicariant sister clades, whose origin may be traced back to the mid-Pleistocene revolution, with several subclades possibly associated to the mid-Bruhnes transition. Geographic range fragmentation of one of these clades, which includes lowland sites, is very recent, and most likely due to the accelerated loss of Atlantic forests by human intervention. Main Conclusions Altogether, the data fit a “refugia within refugia” model, some lack of pattern uniformity notwithstanding, and suggest that these mountains might be the cradles of new species of Iberolacerta. However, the changes operated during the Holocene severely compromise the long-term survival of those genetic lineages more exposed to the anthropogenic perturbations of their habitats.
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Within- and among-population impact of genetic erosion on adult fitness-related traits in the European tree frog Hyla arborea. Heredity (Edinb) 2012; 110:347-54. [PMID: 23250010 DOI: 10.1038/hdy.2012.110] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Assessing in wild populations how fitness is impacted by inbreeding and genetic drift is a major goal for conservation biology. An approach to measure the detrimental effects of inbreeding on fitness is to estimate correlations between molecular variation and phenotypic performances within and among populations. Our study investigated the effect of individual multilocus heterozygosity on body size, body condition and reproductive investment of males (that is, chorus attendance) and females (that is, clutch mass and egg size) in both small fragmented and large non-fragmented populations of European tree frog (Hyla arborea). Because adult size and/or condition and reproductive investment are usually related, genetic erosion may have detrimental effects directly on reproductive investment, and also on individual body size and condition that in turn may affect reproductive investment. We confirmed that the reproductive investment was highly size-dependent for both sexes. Larger females invested more in offspring production, and larger males attended the chorus in the pond more often. Our results did not provide evidence for a decline in body size, condition and reproductive effort with decreased multilocus heterozygosity both within and among populations. We showed that the lack of heterozygosity-fitness correlations within populations probably resulted from low inbreeding levels (inferior to ca. 20% full-sib mating rate), even in the small fragmented populations. The detrimental effects of fixation load were either low in adults or hidden by environmental variation among populations. These findings will be useful to design specific management actions to improve population persistence.
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Jourdan-Pineau H, Folly J, Crochet PA, David P. TESTING THE INFLUENCE OF FAMILY STRUCTURE AND OUTBREEDING DEPRESSION ON HETEROZYGOSITY-FITNESS CORRELATIONS IN SMALL POPULATIONS. Evolution 2012; 66:3624-31. [DOI: 10.1111/j.1558-5646.2012.01705.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Grossen C, Neuenschwander S, Perrin N. The evolution of XY recombination: sexually antagonistic selection versus deleterious mutation load. Evolution 2012; 66:3155-66. [PMID: 23025605 DOI: 10.1111/j.1558-5646.2012.01661.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recombination arrest between X and Y chromosomes, driven by sexually antagonistic genes, is expected to induce their progressive differentiation. However, in contrast to birds and mammals (which display the predicted pattern), most cold-blooded vertebrates have homomorphic sex chromosomes. Two main hypotheses have been proposed to account for this, namely high turnover rates of sex-determining systems and occasional XY recombination. Using individual-based simulations, we formalize the evolution of XY recombination (here mediated by sex reversal; the "fountain-of-youth" model) under the contrasting forces of sexually antagonistic selection and deleterious mutations. The shift between the domains of elimination and accumulation occurs at much lower selection coefficients for the Y than for the X. In the absence of dosage compensation, mildly deleterious mutations accumulating on the Y depress male fitness, thereby providing incentives for XY recombination. Under our settings, this occurs via "demasculinization" of the Y, allowing recombination in XY (sex-reversed) females. As we also show, this generates a conflict with the X, which coevolves to oppose sex reversal. The resulting rare events of XY sex reversal are enough to purge the Y from its load of deleterious mutations. Our results support the "fountain of youth" as a plausible mechanism to account for the maintenance of sex-chromosome homomorphy.
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Affiliation(s)
- Christine Grossen
- Department of Ecology & Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland.
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15
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Dornier A, Cheptou PO. Determinants of extinction in fragmented plant populations: Crepis sancta (Asteraceae) in urban environments. Oecologia 2011; 169:703-12. [PMID: 22200853 DOI: 10.1007/s00442-011-2229-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Accepted: 12/05/2011] [Indexed: 10/14/2022]
Abstract
Local populations are subject to recurrent extinctions, and small populations are particularly prone to extinction. Both demographic (stochasticity and the Allee effect) and genetic factors (drift load and inbreeding depression) potentially affect extinction. In fragmented populations, regular dispersal may boost population sizes (demographic rescue effect) or/and reduce the local inbreeding level and genetic drift (genetic rescue effect), which can affect extinction risks. We studied extinction processes in highly fragmented populations of the common species Crepis sancta (Asteraceae) in urban habitats exhibiting a rapid turnover of patches. A four-year demographic monitoring survey and microsatellite genotyping of individuals allowed us to study the determinants of extinction. We documented a low genetic structure and an absence of inbreeding (estimated by multilocus heterozygosity), which suggest that genetic factors were not a major cause of patch extinction. On the contrary, local population size was the main factor in extinction, whereas connectivity was shown to decrease patch extinction, which we interpreted as a demographic rescue effect that was likely due to better pollination services for reproduction. This coupling of demographic and genetic tools highlighted the importance of dispersal in local patch extinctions of small fragmented populations connected by gene flow.
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Affiliation(s)
- Antoine Dornier
- UMR 5175 CEFE-CNRS, Centre d'Ecologie Fonctionnelle et Evolutive (CNRS), 1919, Route de Mende, 34293, Montpellier Cedex 05, France.
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Robert A. Find the weakest link. A comparison between demographic, genetic and demo-genetic metapopulation extinction times. BMC Evol Biol 2011; 11:260. [PMID: 21929788 PMCID: PMC3185286 DOI: 10.1186/1471-2148-11-260] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Accepted: 09/19/2011] [Indexed: 11/22/2022] Open
Abstract
Background While the ultimate causes of most species extinctions are environmental, environmental constraints have various secondary consequences on evolutionary and ecological processes. The roles of demographic, genetic mechanisms and their interactions in limiting the viabilities of species or populations have stirred much debate and remain difficult to evaluate in the absence of demography-genetics conceptual and technical framework. Here, I computed projected times to metapopulation extinction using (1) a model focusing on the effects of species properties, habitat quality, quantity and temporal variability on the time to demographic extinction; (2) a genetic model focusing on the dynamics of the drift and inbreeding loads under the same species and habitat constraints; (3) a demo-genetic model accounting for demographic-genetic processes and feedbacks. Results Results indicate that a given population may have a high demographic, but low genetic viability or vice versa; and whether genetic or demographic aspects will be the most limiting to overall viability depends on the constraints faced by the species (e.g., reduction of habitat quantity or quality). As a consequence, depending on metapopulation or species characteristics, incorporating genetic considerations to demographically-based viability assessments may either moderately or severely reduce the persistence time. On the other hand, purely genetically-based estimates of species viability may either underestimate (by neglecting demo-genetic interactions) or overestimate (by neglecting the demographic resilience) true viability. Conclusion Unbiased assessments of the viabilities of species may only be obtained by identifying and considering the most limiting processes (i.e., demography or genetics), or, preferentially, by integrating them.
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Affiliation(s)
- Alexandre Robert
- Muséum National d'Histoire Naturelle, Dept, EGB, UMR 7204 CNRS-MNHN-UPMC Conservation des Espèces, Restauration et suivi des Populations, 55 rue Buffon, 75005 Paris, France.
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Chloroplast phylogeography of Helianthemum songaricum (Cistaceae) from northwestern China: implications for preservation of genetic diversity. CONSERV GENET 2011. [DOI: 10.1007/s10592-011-0250-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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18
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Luquet E, David P, Lena JP, Joly P, Konecny L, Dufresnes C, Perrin N, Plenet S. Heterozygosity-fitness correlations among wild populations of European tree frog (Hyla arborea) detect fixation load. Mol Ecol 2011; 20:1877-87. [PMID: 21410805 DOI: 10.1111/j.1365-294x.2011.05061.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Quantifying the impacts of inbreeding and genetic drift on fitness traits in fragmented populations is becoming a major goal in conservation biology. Such impacts occur at different levels and involve different sets of loci. Genetic drift randomly fixes slightly deleterious alleles leading to different fixation load among populations. By contrast, inbreeding depression arises from highly deleterious alleles in segregation within a population and creates variation among individuals. A popular approach is to measure correlations between molecular variation and phenotypic performances. This approach has been mainly used at the individual level to detect inbreeding depression within populations and sometimes at the population level but without consideration about the genetic processes measured. For the first time, we used in this study a molecular approach considering both the interpopulation and intrapopulation level to discriminate the relative importance of inbreeding depression vs. fixation load in isolated and non-fragmented populations of European tree frog (Hyla arborea), complemented with interpopulational crosses. We demonstrated that the positive correlations observed between genetic heterozygosity and larval performances on merged data were mainly caused by co-variations in genetic diversity and fixation load among populations rather than by inbreeding depression and segregating deleterious alleles within populations. Such a method is highly relevant in a conservation perspective because, depending on how populations lose fitness (inbreeding vs. fixation load), specific management actions may be designed to improve the persistence of populations.
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Affiliation(s)
- E Luquet
- Université Lyon 1, CNRS UMR 5023 Ecologie des Hydrosystèmes Fluviaux, Université Claude Bernard Lyon 1, Université de Lyon, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France.
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Severns PM, Liston A, Wilson MV. Habitat fragmentation, genetic diversity, and inbreeding depression in a threatened grassland legume: is genetic rescue necessary? CONSERV GENET 2011. [DOI: 10.1007/s10592-011-0191-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Rousselle Y, Thomas M, Galic N, Bonnin I, Goldringer I. Inbreeding depression and low between-population heterosis in recently diverged experimental populations of a selfing species. Heredity (Edinb) 2011; 106:289-99. [PMID: 20531445 PMCID: PMC3183886 DOI: 10.1038/hdy.2010.72] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 04/23/2010] [Accepted: 05/05/2010] [Indexed: 11/08/2022] Open
Abstract
In fragmented populations, genetic drift and selection reduce genetic diversity, which in turn results in a loss of fitness or in a loss of evolvability. Genetic rescue, that is, controlled input of diversity from distant populations, may restore evolutionary potential, whereas outbreeding depression might counteract the positive effect of this strategy. We carried out self-pollination and crosses within and between populations in an experimental subdivided population of a selfing species, Triticum aestivum L., to estimate the magnitude of these two phenomena. Surprisingly, for a self-fertilizing species, we found significant inbreeding depression within each population for four of the six traits studied, indicating that mildly deleterious mutations were still segregating in these populations. The progeny of within- and between-population crosses was very similar, indicating low between-population heterosis and little outbreeding depression. We conclude that relatively large population effective sizes prevented fixation of a high genetic load and that local adaptation was limited in these recently diverged populations. The kinship coefficient estimated between the parents using 20 neutral markers was a poor predictor of the progeny phenotypic values, indicating that there was a weak link between neutral diversity and genes controlling fitness-related traits. These results show that when assessing the viability of natural populations and the need for genetic rescue, the use of neutral markers should be complemented with information about the presence of local adaptation in the subdivided population.
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Affiliation(s)
- Y Rousselle
- UMR Génétique Végétale, INRA-CNRS-Univ Paris-Sud-AgroParisTech, Ferme du Moulon, Gif sur Yvette, France.
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Abstract
The organization of neutral genetic variation has long been used as a diagnostic tool to infer demographic properties of populations, and recently it has been shown that this information can also be used to estimate the magnitude of genetic deterioration in small or fragmented populations. A further step of this research is to assess whether neutral genetic indicators can serve to predict and compare the viabilities of endangered species. I use modeling to explore how ecological metapopulation settings are related to neutral genetic indicators (such as the fixation index [F(ST)]), changes in genetic load, and metapopulation viability. The analysis indicates that genetic indicators are generally strongly and consistently correlated with the genetic load, population size and structure, and time of extinction but identifies two potential limitations for their use in viability assessments. First, the regime of environmental perturbations is not accurately reflected by neutral indicators, so that their predictive power may be reduced in variable environments. Second, many species are threatened by recent human-induced changes of their habitat configuration. In most cases, genetic indicators may not have reached their equilibrium value in the altered habitat, which limits their ability to compare species with heterogeneous histories and life-history traits.
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Affiliation(s)
- Alexandre Robert
- Muséum National d'Histoire Naturelle (MNHN), Département Ecologie et Gestion de la Biodiversité, Unité Mixte de Recherche 7204 Centre National de la Recherche Scientifique-MNHN-Université Pierre et Marie Curie Conservation des Espèces, Restauration et Suivi des Populations, 55 rue Buffon, 75005 Paris, France.
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Lopez S, Rousset F, Shaw FH, Shaw RG, Ronce O. Joint effects of inbreeding and local adaptation on the evolution of genetic load after fragmentation. CONSERVATION BIOLOGY : THE JOURNAL OF THE SOCIETY FOR CONSERVATION BIOLOGY 2009; 23:1618-1627. [PMID: 19775278 DOI: 10.1111/j.1523-1739.2009.01326.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Disruption of gene flow among demes after landscape fragmentation can facilitate local adaptation but increase the effect of genetic drift and inbreeding. The joint effects of these conflicting forces on the mean fitness of individuals in a population are unknown. Through simulations, we explored the effect of increased isolation on the evolution of genetic load over the short and long term when fitness depends in part on local adaptation. We ignored genetic effects on demography. We modeled complex genomes, where a subset of the loci were under divergent selection in different localities. When a fraction of the loci were under heterogeneous selection, isolation increased mean fitness in larger demes made up of hundreds of individuals because of improved local adaptation. In smaller demes of tens of individuals, increased isolation improved local adaptation very little and reduced overall fitness. Short-term improvement of mean fitness after fragmentation may not be indicative of the long-term evolution of fitness. Whatever the deme size and potential for local adaptation, migration of one or two individuals per generation minimized the genetic load in general. The slow dynamics of mean fitness following fragmentation suggests that conservation measures should be implemented before the consequences of isolation on the genetic load become of concern.
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Affiliation(s)
- Sébastien Lopez
- Université Montpellier 2, Montpellier, Hérault, CNRS, Institut des Sciences de l'Evolution, CC 65, Place Eugène Bataillon, 34 095 Montpellier Cedex 5, France
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Fine-scale spatial genetic structure and allozymic diversity in natural populations of Ocotea catharinensis Mez. (Lauraceae). CONSERV GENET 2009. [DOI: 10.1007/s10592-009-9939-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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