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Sustainability of the South China tiger: Implications of inbreeding depression and introgression
Abstract
The South China tiger (Panther tigris amoyensis) is critically endangered with 73 remaining individuals living in captivity, all derived from six wild founders since 1963.
The population shows a low level of juvenile survivorship and reproductive difficulties, and faces a huge conservation challenge.
In this study, inbreeding depression and genetic diversity decline were examined by using pedigree data and 17 microsatellites.
The constant B, which is related to the number of lethal equivalents, was estimated to be 0 for the offspring of noninbred parents, but
was >0 for the offspring of inbred parents and for all offspring. Percentage of successfully breeding tigers inversely correlated
with inbreeding level (r=−0.626, α=0.05). Taken together, these findings suggest the population is suffering from inbreeding depression in juvenile survivorship
and fecundity. No significant correlation was detectable for the mean litter size with f of either dams (r=−0.305, α=0.46) or kittens (r=0.105, α=0.71), indicating litter size was not strongly subject to inbreeding depression. The average number of alleles per locus
was 4.24±1.03 (SE), but effective number of alleles was only 2.53±0.91. Twenty-one alleles carried by early breeders at
13 loci were absent in the present breeders and potential breeders. Multilocus heterozygosity was inversely correlated with
inbreeding levels (r=−0.601, α=0.004). These findings suggest rapid allelic diversity loss is occurring in this small captive population and that heterozygosity
is being lost as it becomes more inbred. Our phylogenetic analysis supports past work indicating introgression from northern
Indochinese tigers in the population. As no wild representatives of the South China tiger can be added to the captive population,
we may consider the alternate scenario of further introgression in the interest of countering inbreeding depression and declining
genetic diversity.
... Inbreeding, low genetic diversity, minimal populations, and endangerment currently block South China tiger populations from recovery. Appropriate artificial interference may preserve the population, although low genetic diversity makes it difficult to restore the minimal populations and release them into the wild [8]. ...
... [13]. Although the population of captive South China tigers has increased [13,14], inbreeding is inevitable due to the small initial population [8,15]. The dangers of inbreeding are apparent, especially for the South China tiger, which is extinct in the wild [16]. ...
... About 66 years ago, the effective population of the South China tiger was lost [15]. Inbreeding has taken place since captivity in 1963; continuous inbreeding has also led to some problems that are not conducive to population reproduction [8,15,62]. However, the inbreeding of Amur tigers in captivity is low [63]. ...
Panthera tigris is a top predator that maintains the integrity of forest ecosystems and is an integral part of biodiversity. No more than 400 Amur tigers (P. t. altaica) are left in the wild, whereas the South China tiger (P. t. amoyensis) is thought to be extinct in the wild, and molecular biology has been widely used in conservation and management. In this study, the genetic information of Amur tigers and South China tigers was studied by whole-genome sequencing (WGS). A total of 647 Gb of high-quality clean data was obtained. There were 6.3 million high-quality single-nucleotide polymorphisms (SNPs), among which most (66.3%) were located in intergenic regions, with an average of 31.72% located in coding sequences. There were 1.73 million insertion-deletions (InDels), among which there were 2438 InDels (0.10%) in the coding region, and 270 thousand copy number variations (CNVs). Significant genetic differences were found between the Amur tiger and the South China tiger based on a principal component analysis and phylogenetic tree. The linkage disequilibrium analysis showed that the linkage disequilibrium attenuation distance of the South China tiger and the Amur tiger was almost the same, whereas the r2 of the South China tiger was 0.6, and the r2 of the Amur tiger was 0.4. We identified functional genes and regulatory pathways related to reproduction, disease, predation, and metabolism and characterized functional genes related to survival in the wild, such as smell, vision, muscle, and predatory ability. The data also provide new evidence for the adaptation of Amur tigers to cold environments. PRKG1 is involved in temperature regulation in a cold climate. FOXO1 and TPM4 regulate body temperature to keep it constant. Our results can provide genetic support for precise interspecies conservation and management planning in the future.
... Superficially, the current population number, age structure and sex ratio (Fig. S1) are supportive of its sustainability. However, due to the small number of founders and unequal founders' contributions, inbreeding is unavoidable (Xu et al., 2007). This resulted in inbreeding depression that progressively degraded the reproductive capacity of adults and the survival of juveniles despite substantial improvements in captive rearing technology and expertise (Xu et al., 2007;Yuan et al., 2021). ...
... However, due to the small number of founders and unequal founders' contributions, inbreeding is unavoidable (Xu et al., 2007). This resulted in inbreeding depression that progressively degraded the reproductive capacity of adults and the survival of juveniles despite substantial improvements in captive rearing technology and expertise (Xu et al., 2007;Yuan et al., 2021). In addition, pedigree-based estimation showed that the present population represents 65.23% of the six ancestor's genetic diversity (Yuan et al., 2020), meaning 34.77% are lost. ...
... We noticed that a few affected genes specific to the SCT were related to reproduction, growth and development, and disease, etc (Table S21), and some LOF mutations tend to impair sperm genesis, maturation and activity, fetal growth, and survival, as well as normality of tissue and organ development. This expectation is consistent with the observed low reproductive rate and high cub mortality in the captive SCT population (Xu et al., 2007;Yuan et al., 2021). ...
The South China tiger (Panthera tigris amoyensis, SCT) is the most critically endangered subspecies of tigers due to functional extinction in the wild. Inbreeding depression is observed among the captive population descended from six wild ancestors, resulting in high juvenile mortality and low reproduction. We assembled and characterized the first SCT genome and an improved Amur tiger (P. t. altaica, AT) genome named AmyTig1.0 and PanTig2.0. The two genomes are the most continuous and comprehensive among any tiger genomes yet reported at the chromosomal level. By using the two genomes and re‐sequencing data of 15 SCT and 13 AT individuals, we investigated the genomic signature of inbreeding depression of the SCT. Results indicated that the effective population size of SCT experienced three phases of decline, ~5.0 kya to 1.0 kya, recent 100 years ago, and since captive breeding in 1963. We found 43 long runs of homozygosity (ROH) fragments that were shared by all individuals in the SCT population and covered a total length of 20.63% in the SCT genome. We also detected a large proportion of identical‐by‐descent (IBD) segments across the genome in the SCT population, especially on ChrB4. Deleterious nonsynonymous single nucleotide polymorphic sites (nsSNP) and loss‐of‐function (LOF) mutations were found across genomes with extensive potential influences, despite that a portion of these loads had been purged by inbreeding depression. Our research provides an invaluable resource for the formulation of genetic management policies for the South China tiger such as developing genome‐based breeding and genetic rescue strategy.
... Genetic diversity can be measured as quantitative trait variations, allelic diversity, and heterozygosity [75,76]. Quantitative trait variations are related to overall fitness (e.g., survival probability and reproductive success rate) of individuals involving many loci rather than one [75]. ...
... Allelic diversity refers to the number of different alleles at any given locus, whereas heterozygosity is the percentage of loci that are heterozygous in a population or individual [72,75]. Inbred individuals have a low level of heterozygosity at genome-wide loci [76]. The consequence of inbreeding in a population with 1000 or fewer individuals is due to recessive lethal alleles [72]. ...
... The consequence of inbreeding in a population with 1000 or fewer individuals is due to recessive lethal alleles [72]. This happens through the process called genetic drift, when both allelic diversity and heterozygosity are lost in small populations [75,76]. A study of orangutans estimated that small populations of fewer than 300 individuals tend to lose 10% of their genetic diversity, thus are at a high risk of extinction after 1000 years due inbreeding [72]. ...
... This population dropped below its 100-year genetic goal set in 2005 after only 10 years [3]. Molecular DnA analysis confirms an extremely low level of genetic diversity within this population [9,10]. ...
... Beginning in 1977, the number of females remained essentially constant for 25 years, while the number of males almost doubled, leading to a male-biased sex ratio and limiting reproductive potential. Many of the limited number of breeding pairs failed to reproduce due to a myriad of difficulties, from health issues to behavioral incompatibility, such as overly aggressive males and unreceptive females [3,4,10]. Demographic instability in age and sex structure of the population led to lower reproduction, further decline, and increased inbreeding [6]. ...
... Inbreeding itself may be a contributing culprit [3,10]. Analysis of studbook data representing 356 births from 130 litters found no evidence of skewed sex ratio or smaller litter size in inbred cubs [3]. ...
The South China tiger holds a place of honor in China-as a cultural icon in art, literature, and philosophy, as a symbol of wilderness to promote a new conservation ethic amid an expanding human population, and as a source of national pride as the only uniquely Chinese tiger subspecies. Early in its history, the captive South China tiger population flourished. By 1990, the pedigree represented several generations in captivity, gene diversity begin to decline, and inbreeding levels averaged over 20%. Tiger experts became increasingly alarmed about the critical status of this subspecies both in the wild and captivity. In the face of a plummeting wild population, the need for effective captive management drew national and international attention. The greatest challenges to the viability of the captive population are low reproductive success and low level of genetic variation. Population growth is paramount to slow genetic loss and stabilize the population. The South China tiger has yet to cross over the threshold of viability in captivity. A healthy, self-sustaining captive population is critical to the preservation of what remains of this subspecific genetic line; this milestone must be achieved before this population has the ability to provide tigers to repopulate the mountains and forests of south-central China.
... Research showed that tigers are one of the most inbred animals in captivity (Begany & Criscuolo, 2009). The captive South China tiger population was found to be suffering from inbreeding depression and a decline in genetic diversity (Xu, Fang & Li, 2007). High levels of inbreeding brought stillbirths and high infant mortality and very low genetic diversity within the captive population of Asian lions (Atkinson et al., 2018). ...
... Accurate and complete pedigree information is essential for effective pedigree analysis (Ferrie et al., 2013). However, the recorded data in the studbook may be missing or incorrect and the information in the studbook should be supported by genetic analysis (Ferrie et al., 2013;Xu, Fang & Li, 2007). ...
As one of the most endangered species, tiger ( Panthera tigris ) inbreeding has become an urgent issue to address. Using a microsatellite (short tandem repeat, STR) identification system, paternity testing may be helpful to avoid inbreeding in captive breeding programs. In this study, we developed a genome-based identification system named tiger pedigree identification multiplex system (TPI-plex). By analyzing the entire tiger genome, 139,967 STR loci were identified and 12.76% of these displayed three to six alleles among three re-sequenced individual tiger genomes. A total of 204 candidate STRs were identified and screened with a reference population containing 31 unrelated captive tigers. Of these, 15 loci were chosen for inclusion in the multiplex panel. The mean allele number and mean expected heterozygosity (He) were 7.3333 and 0.7789, respectively. The cumulative probability of exclusion (CPE) and total probability of discrimination power (TDP) reached 0.999999472 and 0.999999999999995, respectively. The results showed that the TPI-plex system can be applied in routine pedigree identification for captive tigers. We also added a sex identification marker named TAMEL into the TPI-plex for sex determination.
... 长期 以来, 这一种群一直采用基于谱系的单配制管理. 研究 表明, 所有的个体都有血缘关系, 遗传多样性下降速 度较快, 同时伴随着明显的近交衰退, 如成年虎繁殖 率和幼虎存活率持续低靡[39] . 本研究预示着华南虎参考文献 1 Wilcken J, Lees C. Managing Zoo Populations: Compiling and Analysing Studbook Data. ...
... In fact, a total of 18 tigers were captured from the wild in southern China and housed in captivity from 1955 to 1970, but only 6 of them ever produced progeny ( Figure 1; Table 1). As most individuals are derived from a small number of founders, the current captive South China tigers might suffer from low levels of genetic diversity and high levels of inbreeding (Wei et al. 2005;Xu et al. 2007;Yin 2016). Furthermore, because large numbers of breeding and pedigree records went missing for the period between the 1960s and 1980s, it is suspected that some individuals in the captive program might be of uncertain ancestry due to accidental introgression of tigers from other sources rather than the South China tiger. ...
The South China tiger (Panthera tigris amoyensis) is endemic to China and also the most critically endangered subspecies of living tigers. It is considered extinct in the wild and only about 150 individuals survive in captivity to date, whose genetic heritage, however, is ambiguous and controversial. Here, we conducted an explicit genetic assessment of 92 studbook-registered South China tigers from 14 captive facilities using a subspecies-diagnostic system in the context of comparison with other voucher specimens to evaluate the genetic ancestry and level of distinctiveness of the last surviving P. t. amoyensis. Three mtDNA haplotypes were identified from South China tigers sampled in this study, including a unique P. t. amoyensis AMO1 haplotype not found in other subspecies, a COR1 haplotype that is widespread in Indochinese tigers (P. t. corbetti), and an ALT haplotype that is characteristic of Amur tigers (P. t. altaica). Bayesian STRUCTURE analysis and parentage verification confirmed the Verified Subspecies Ancestry (VSA) as the South China tiger in 74 individuals. Genetic introgression from other tigers was detected in 18 tigers, and subsequent exclusion of these and their offspring from the breeding program is recommended. Both STRUCTURE clustering and microsatellite-based phylogenetic analyses demonstrated a close genetic association of the VSA South China tigers to Indochinese tigers, an issue that could only be elucidated by analysis of historical South China tiger specimens with wild origin. Our results also indicated a moderate level of genetic diversity in the captive South China tiger population, suggesting a potential for genetic restoration.
... High homozygosity levels may indicate when a population is genetically unhealthy and at risk of inbreeding depression. Inbreeding and resulting inbreeding depression can lead to the decline and/or extinction of the species or population [37][38][39][40][41][42][43]. Domestic dogs, specifically purebred domestic breeds, typically have elevated levels of inbreeding due to the effect of human artificial selection, population bottlenecks and line breeding [104]. ...
Dingoes play a strong role in Australia’s ecological framework as the apex predator but are under threat from hybridization and agricultural control programs. Government legislation lists the conservation of the dingo as an important aim, yet little is known about the biogeography of this enigmatic canine, making conservation difficult. Mitochondrial and Y chromosome DNA studies show evidence of population structure within the dingo. Here, we present the data from Illumina HD canine chip genotyping for 23 dingoes from five regional populations, and five New Guinea Singing Dogs to further explore patterns of biogeography using genome-wide data. Whole genome single nucleotide polymorphism (SNP) data supported the presence of three distinct dingo populations (or ESUs) subject to geographical subdivision: southeastern (SE), Fraser Island (FI) and northwestern (NW). These ESUs should be managed discretely. The FI dingoes are a known reservoir of pure, genetically distinct dingoes. Elevated inbreeding coefficients identified here suggest this population may be genetically compromised and in need of rescue; current lethal management strategies that do not consider genetic information should be suspended until further data can be gathered. D statistics identify evidence of historical admixture or ancestry sharing between southeastern dingoes and South East Asian village dogs. Conservation efforts on mainland Australia should focus on the SE dingo population that is under pressure from domestic dog hybridization and high levels of lethal control. Further data concerning the genetic health, demographics and prevalence of hybridization in the SE and FI dingo populations is urgently needed to develop evidence based conservation and management strategies.
... Dodejme, že o podobných introgresích víme u dalších ohrožených taxonů např. bizona (příměs skotu), levharta mandžuského (příměs levharta čínského -Uphyrkina a O´Brien 2003) nebo tygra čínského (příměs tygra indočínského - Xu et al. 2007). Ochranářsky jde o kompromisní řešení, neboť trvat na čistokrevnosti (a naopak) by mohlo u některých taxonů znamenat, že o ně zcela přijdememělo by se k němu tedy přistupovat velmi opatrně a jen v krajních případech. ...
Two specialized grazers extirpated by men, wild horse and aurochs, played an important role in shaping of the European landscape, as well as human civilization. Although these two species gave rise to the most important domestic animals, domestic horse and cattle, basic information on their appearance, ecology, evolutionary history and domestication remained unknown until recently. However, the advancement of ancient DNA genetic analyses from subfossil biological material, together with new archeological and paleontological evidence allowed researchers to reveal previously undetectable traits, such as the original coat colour of wild horses (bay to black). Importantly, the presence of wild horses from Iberia to Alaska has been confirmed, together with habitat preferences of aurochs prior to the advent of human civilization, which pushed them to suboptimal habitats in deep forests which became (as in European bison) their last refuge. With the extinction of wild horses and aurochs, Europe lost the entire guild of specialized large grazers. These, unlike cloven-hoofed animals, are able to halt the otherwise inevitable overgrowth of non-forest habitats on which much of European biodiversity depends, by woody vegetation. Currently, numerous projects are taking place throughout Europe, aiming to introduce natural grazing to restore lost ecological interactions using dedomesticated horses and cattle. As shown by numerous examples abroad, of the >400 horse and >400 cattle breeds worldwide, only a small fraction is suitable for the purposes of natural grazing. The information presented herein is essential for responsible and long-term sustainable setting of modern extensive perennial grazing management schemes in the Czech Republic and the Europe as a whole. Utilisation of animals which match their wild ancestors both morphologically and ecologically can significantly reduce costs of nature management, especially in the case of biologically important nonforest habitats.
... Heterozygosity is an important component of population genetic analyses, because it is often positively correlated with increased fitness, resistance to disease and long-term persistence of natural populations (Keller and Waller 2002, Jannikke et al. 2006, Xu et al. 2007, O'Grady et al. 2006. Positive correlations between heterozygosity and both fitness (FitzSimmons et al. 1995) and resistance to disease have also been documented in bighorn sheep (Coltman et al. 1999, Luikart et al. 2008a. ...
... the likelihood of identifying a substantial number of unique south China tigers from the population is thus presumably not possible. an explicit genetic assessment of the captive Chinese tigers using the diagnostic system set here in the context of comparison with other purebred subspecies should be immediately conducted to validate the uniqueness, or non-uniqueness, of south China tigers [59,60]. ...
The rapidly changing field of molecular genetics, particularly advances in genome sequence analyses, has provided new tools to reconstruct what defines a tiger and its origins. The evolutionary history framing the tiger into the exquisite predator has ancestral roots and history are depicted in its phylogeography, the genetic patterns of diversification among individuals and populations on both temporal and geographical scales. The subspecies concept provokes both scientific and political controversy because several subspecies are considered to be specific units of conservation, which are protected by international treaties and organizations concerned with the stewardship of wildlife on the species level. The recognition of subspecies has particular relevance because tiger conservation strategies are inextricably tied to subspecific taxonomic divisions. Debates persist over the role of captive tigers in conservation efforts, whether managed captive populations serve as adequate genetic reservoirs for the natural populations, and whether the presumptive "dgeneric" tigers have any conservation value. The most direct way to address the dilemma is through a thorough understanding of the genetic ancestry, the extent of genetic admixture, and the level of genetic diversity of captive tigers in relation to the wild populations.
... Captive breeding programs of endangered species typically start with a small number of founders. Cost and space constraints usually ensure captive populations remain small in successive generations , thus facing the negative effects associated with small population size (i.e., genetic diversity loss, inbreeding depression, accumulation of deleterious mutations; Bryant and Reed 1999; Lynch and O'Hely 2001; Charpentier et al. 2005; Xu et al. 2007; Tzika et al. 2009). Although shortterm survival may not be highly correlated with genetic diversity, long-term survival most certainly is because of the potential to adapt to changing environments over long time periods is directly related to levels of genetic diversity (Madsen et al. 1999; Reed and Frankham 2003; Markert et al. 2010). ...
AbstractA species of Galápagos tortoise endemic to Española Island was reduced to just 12 females and three males that have been bred in captivity since 1971 and have produced over 1700 offspring now repatriated to the island. Our molecular genetic analyses of juveniles repatriated to and surviving on the island indicate that none of the tortoises sampled in 1994 had hatched on the island versus 3% in 2004 and 24% in 2007, which demonstrates substantial and increasing reproduction in situ once again. This recovery occurred despite the parental population having an estimated effective population size Document Type: Research Article DOI: http://dx.doi.org/10.1111/eva.12014 Publication date: February 1, 2013 $(document).ready(function() { var shortdescription = $(".originaldescription").text().replace(/\\&/g, '&').replace(/\\, '<').replace(/\\>/g, '>').replace(/\\t/g, ' ').replace(/\\n/g, ''); if (shortdescription.length > 350){ shortdescription = "" + shortdescription.substring(0,250) + "... more"; } $(".descriptionitem").prepend(shortdescription); $(".shortdescription a").click(function() { $(".shortdescription").hide(); $(".originaldescription").slideDown(); return false; }); }); Related content In this: publication By this: publisher By this author: Milinkovitch, Michel C. ; Kanitz, Ricardo ; Tiedemann, Ralph ; Tapia, Washington ; Llerena, Fausto ; Caccone, Adalgisa ; Gibbs, James P. ; Powell, Jeffrey R. GA_googleFillSlot("Horizontal_banner_bottom");
... The population is managed using a single-mating system whereby one estrus female is paired with one male. Xu et al. [39] showed that all surviving south China tigers are related and display declining trends in individual heterozygosity simultaneous with severe inbreeding depression expressed as low reproductive rates and low kitten survival. Polyandry might be a useful measure to help overcome these problems if the reproductively capable but geographically isolated tigers were combined at one location in a single breeding population as the Siberian tigers were at Harbin. ...
Male tigers (Panthera tigris altaica) in captivity copulate alternatively with an estrous female, suggesting a potential for heteropaternity as an effective reproductive strategy to maximize genetic diversity of offspring. We analyzed microsatellites to test and compare the genetic output of multiple male mating (simultaneous polyandry) and single male mating (monogamy) with a female in a captive population. Simultaneous polyandry resulted in heteropaternity in 66.7% observed litters. No significant differences between parental populations and between offspring populations were detected in the number of alleles (A), expected heterozygosity (H
e), number of effective alleles (N
e) per locus and standard individual heterozygosity (SH) (P>0.05 for all 4 indexes). Comparisons showed no significant reduction of A, H
o, H
e and SH from parental population to offspring population for the two mating modes (P>0.05) except for SH in polyandrous families (P=0.029). However, such reduction was equivalent to single mating families when the influence of relatedness was eliminated using effective SH (E
SH
) (P>0.05). These results highlight an alternative strategy for managing captive populations of tiger and other wild felids in which animals are combined at one location allowing for copulation by multiple males to encourage heteropaternity in favor of maintained genetic diversity among offspring.
... Captive breeding programs of endangered species typically start with a small number of founders. Cost and space constraints usually ensure captive populations remain small in successive generations , thus facing the negative effects associated with small population size (i.e., genetic diversity loss, inbreeding depression, accumulation of deleterious mutations; Bryant and Reed 1999; Lynch and O'Hely 2001; Charpentier et al. 2005; Xu et al. 2007; Tzika et al. 2009 ). Although shortterm survival may not be highly correlated with genetic diversity, long-term survival most certainly is because of © 2012 Blackwell Publishing Ltd. ...
A species of Galápagos tortoise endemic to Española Island was reduced to just 12 females and three males that have been bred in captivity since 1971 and have produced over 1700 offspring now repatriated to the island. Our molecular genetic analyses of juveniles repatriated to and surviving on the island indicate that none of the tortoises sampled in 1994 had hatched on the island versus 3% in 2004 and 24% in 2007, which demonstrates substantial and increasing reproduction once again. This recovery occurred despite the parental population having an estimated effective population size <8 due to a combination of unequal reproductive success of the breeders and nonrandom mating in captivity. These results provide guidelines for adapting breeding regimes in the parental captive population and decreasing inbreeding in the repatriated population. Using simple morphological data scored on the sampled animals, we also show that a strongly heterogeneous distribution of tortoise sizes on Española Island observed today is due to a large variance in the number of animals included in yearly repatriation events performed in the last 40 years. Our study reveals that, at least in the short run, some endangered species can recover dramatically despite a lack of genetic variation and irregular repatriation efforts.
... As species in captive breeding programs are frequently endangered they are often maintained in small numbers. Inherent to all small populations, both natural and captive, the most well-known sources of genetic change include loss of genetic diversity, inbreeding depression, and accumulation of new deleterious mutations (Bryant and Reed, 1999;Charpentier et al., 2005;Xu et al., 2007). ...
Captive breeding for species of conservation concern is the act of bringing rare or endangered animals into captivity with the hope of rearing sustained captive populations for eventual reintroduction into the wild. Within captivity, genetic changes can occur that may reduce a species’ ability to persist once a population is reintroduced back into its natural habitat. We sought to determine the efficacy of recommendations made to minimize genetic adaptation to captivity by addressing the following questions: (i) Are these recommendations already being carried out in captive programs? (ii) How practical is each recommendation? and (iii) Which recommendations call for future investigation? We performed an extensive search of the published literature for studies of non-domestic, non-model, captive animals in which the investigators used and reported a strategy that can minimize genetic adaptation to the captive environment. We found different forms of each recommendation already being executed in captive programs to varying degrees. In all, we reviewed 90 articles covering four broad categories of strategies. We conclude that the best approach to minimize genetic adaptation is to reduce the number of generations that a species spends in captivity. If this is not possible, then we suggest attempting to minimize generations first by delaying reproduction and then by cryopreservation of germplasm. Other strategies are effective to varying degrees depending on the species’ natural history. A large gap in the current literature is the interactive effects of multiple strategies being implemented simultaneously, future research should focus on this issue.
... Three of these putative subspecies are now extinct (P. t. virgata, P. t. sondaica, and P. t. balica) and P. t. amoyensis is no longer present in the wild and exists only in captivity [10], although it has been suggested recently that even these are subspecific hybrids with P. t. corbetti [11]. The remaining five extant tiger subspecies are critically endangered [5]; however there is a continuing discussion as to how many tiger subspecies can be recognized based on morphological, biochemical, and molecular genetic studies with different authors proposing diverse conclusions11121314. ...
The tiger (Panthera tigris) is currently listed on Appendix I of the Convention on the International Trade in Endangered Species of Wild Fauna and Flora; this affords it the highest level of international protection. To aid in the investigation of alleged illegal trade in tiger body parts and derivatives, molecular approaches have been developed to identify biological material as being of tiger in origin. Some countries also require knowledge of the exact tiger subspecies present in order to prosecute anyone alleged to be trading in tiger products. In this study we aimed to develop and validate a reliable single assay to identify tiger species and subspecies simultaneously; this test is based on identification of single nucleotide polymorphisms (SNPs) within the tiger mitochondrial genome. The mitochondrial DNA sequence from four of the five extant putative tiger subspecies that currently exist in the wild were obtained and combined with DNA sequence data from 492 tiger and 349 other mammalian species available on GenBank. From the sequence data a total of 11 SNP loci were identified as suitable for further analyses. Five SNPs were species-specific for tiger and six amplify one of the tiger subspecies-specific SNPs, three of which were specific to P. t. sumatrae and the other three were specific to P. t. tigris. The multiplex assay was able to reliably identify 15 voucher tiger samples. The sensitivity of the test was 15,000 mitochondrial DNA copies (approximately 0.26 pg), indicating that it will work on trace amounts of tissue, bone or hair samples. This simple test will add to the DNA-based methods currently being used to identify the presence of tiger within mixed samples.
... Nevertheless, the positive effect of inbreeding on survival does not support altering population management strategies (i.e., increasing the level of inbreeding to improve offspring survival) at the expense of reduced litter size or other potential negative effects. It is also important to consider that the level of inbreeding in the red wolf population is relatively low compared with other inbred carnivore populations that show increases in juvenile mortality [e.g., Canis lupus, Laikre and Ryman, 1991; Panthera tigris amoyensis, Xu et al., 2007]. The level of inbreeding affecting mortality in the red wolf may be higher than that required for evidence of inbreeding depression in other aspects of fitness. ...
Captive-breeding programs have been widely used in the conservation of imperiled species, but the effects of inbreeding, frequently expressed in traits related to fitness, are nearly unavoidable in small populations with few founders. Following its planned extirpation in the wild, the endangered red wolf (Canis rufus) was preserved in captivity with just 14 founders. In this study, we evaluated the captive red wolf population for relationships between inbreeding and reproductive performance and fitness. Over 30 years of managed breeding, the level of inbreeding in the captive population has increased, and litter size has declined. Inbreeding levels were lower in sire and dam wolves that reproduced than in those that did not reproduce. However, there was no difference in the inbreeding level of actual litters and predicted litters. Litter size was negatively affected by offspring and paternal levels of inbreeding, but the effect of inbreeding on offspring survival was restricted to a positive influence. There was no apparent relationship between inbreeding and method of rearing offspring. The observable effects of inbreeding in the captive red wolf population currently do not appear to be a limiting factor in the conservation of the red wolf population. Additional studies exploring the extent of the effects of inbreeding will be required as inbreeding levels increase in the captive population.
p>This thesis compares the population genetics of two bumblebee species ( B. muscorum and B. jonellus) in a model island system (Hebrides, UK). Both species show significant levels of population structuring ( B. muscorum, θ = 0.13 and B. jonellus, θ = 0.034) and isolation by distance. Pairwise comparisons between populations suggest that B. jonellus disperse > 50 km relatively frequently. By contrast, B. muscorum populations are spatially structured on a smaller scale, and are estimated to disperse > 8 km only infrequently. Populations of both species show signs of recent population bottlenecks under some microsatellite mutation models, and under all models bottlenecks were more frequent for B. muscorum . Diploid males were found at low frequency in B. muscorum but were not detected for B. jonellus . However, we find triphoid individuals in both species, indirectly confirming that diploid males were present in the previous generation. This is the first time that triphoids have been detected in any wild bee populations. For both species triploid frequencies were negatively correlated with population size, and those restricted to less than 13km<sup>2</sup> of suitable habitat were particularly at risk. Estimated total triploid frequencies peaked at 20% with respect to normal diploid workers, and were higher in B. muscorum than in B. jonellas , perhaps due to the greater dispersal range of the latter species. These results indicate that closely-related species exhibit cryptic but fundamental differences in aspects of their ecology which influence their susceptibility to habitat fragmentation. Observed differences may in part explain differential declines of mainland populations of bumblebees and will greatly inform future conservation strategies.</p
The South China tiger (SCT) is close to extinction in the wild and the captive population may be the only hope of saving this species. Based on the international studbook of the SCT from 1956 to 2019, the life history and population parameters were summarized, and lethal equivalents (B) were estimated. Population viability analysis (PVA) was carried out to simulate the population dynamics and the effects of key factors influencing population dynamics were assessed on the basis of sensitivity analysis, including lethal equivalent, sex ratio, percentage of females breeding and percentage of males breeding. The average B value for the captive SCT population was estimated to be 4.24 at the population level. The captive population of SCT is currently growing up, with a positive growth rate of 0.093 (SD = 0.088) and a probability of extinction of 1% within the next 100 years. The current SCT population is sensitive to lethal equivalents (S = 2.30) and the percentage of females breeding (S = 1.94). We suggest a feasible breeding plan that can practically reduce the effect of inbreeding, and better husbandry practices to improve the percentage of females breeding.
We monitored the reproductive parameters of South China Tigers (SCT) in captivity from 1983 to 2018. Tigers gave birth in all but 3 months of the year, with a peak in May, June, and July (goodness of fit test, χ2 = 49.928, p = 0.000, n = 270 litters from 65 mothers). The minimum age at 1st reproduction was 4.96 ± 2.43 (standard deviation, SD) years. The mean interval between litters was 410.2 ± 290.2 (SD) days (n = 38 pairs with consecutive reproduction). Mean litter size was 2.1 ± 0.9 (SD) (n = 270 litters from 65 tigers). The average survival rate of newborn cubs was 55.7% (SD = 17.7). There was significant maternal age variation among the litters studied. Reproduction mainly occurs in females in their prime (3–14 years old), with little in young and old females (one-way analysis of variance, ANOVA, F = 8.314, p = 0.005). Reproductive parameters of SCTs could be the basis of analysis on the population dynamics and management, and genetic considerations are necessary to plan future breeding programs and to assist in the selection of individuals for reintroduction to the wild.
Tiger conservation efforts are shifting from an exclusive focus on single reserves to include large heterogeneous landscapes.
Of what use is evolutionary science to society? Can evolutionary thinking provide us with the tools to better understand and even make positive changes to the world? Addressing key questions about the development of evolutionary thinking, this book explores the interaction between evolutionary theory and its practical applications. Featuring contributions from leading specialists, Pragmatic Evolution highlights the diverse and interdisciplinary applications of evolutionary thinking: their potential and limitations. The fields covered range from palaeontology, genetics, ecology, agriculture, fisheries, medicine, neurobiology, psychology and animal behaviour; to information technology, education, anthropology and philosophy. Detailed examples of useful and current evolutionary applications are provided throughout. An ideal source of information to promote a better understanding of contemporary evolutionary science and its applications, this book also encourages the continued development of new opportunities for constructive evolutionary applications across a range of fields.
The Convention on the International Trade in Endangered Species of Wild Fauna and Flora (CITES) monitors the international trade in endangered animal and plant species; a high profile example is the tiger, Panthera tigris. We report on the application of a SNaPshot multiplex technique to simultaneously identify tiger species and subspecies; this test is based on identification of SNPs within the tiger mitochondrial genome. Mitochondrial DNA sequences from four of the five extant putative tiger subspecies were obtained and combined with DNA sequence data from 492 tiger and 349 other mammalian species. A total of 11 SNP loci were identified: five specific for tiger; three specific to Panthera tigris sumatrae and; three specific to P. t. tigris. The multiplex assay was able to reliably identify 15 voucher tiger samples. The sensitivity of the test was 15,000 mitochondrial DNA copies, indicating that it will work on trace amounts of tissue, bone or hair.
Testicular volume, semen traits, and pituitary-gonadal hormones were measured in popu-lations of Felis concolor from Florida, Texas, Colorado, Latin America, and North American zoos. More Florida panthers (F. concolor coryi) were unilaterally cryptorchid (one testicle not descended into the scrotum) than other populations (43.8 versus 3.9%, respectively). Florida panthers also had lower testicular and semen volumes, poorer sperm progressive motility, and more morphologically abnormal sperm, including a higher incidence of ac-rosomal defects and abnormal mitochondrial sheaths. Transmission electron microscopy revealed discontinuities in the acrosome, extraneous acrosomal material under the plasma membrane, and remnants of the golgi complex under the acrosome. No differences were detected in mean-circulating follicle-stimulating hormone, luteinizing hormone, or testos-terone between Florida panthers and other populations of mountain lions. Seminal traits and concentrations of follicle-stimulating hormone, luteinizing hormone, and testosterone were similar between cryptorchid and noncryptorchid Florida panthers. Animals with F. concolor coryi ancestry were categorized on the basis of amount of genetic variation (low = type A; medium = type B; high = captive Piper stock). Compared to counterparts, type A Florida panthers had the lowest testicular volume and sperm-motility ratings and were the only animals exhibiting unilateral cryptorchidism. These results demonstrate the ex-istence of major morphological and physiological differences among populations of F. concolor, a finding potentially related to differences in genetic diversity.
This paper describes results of a Sino-American field survey seeking evidence of South China tigers Panthera
tigris
amoyensis in the wild. In 2001 and 2002 field surveys were conducted in eight reserves in five provinces identified by government authorities as habitat most likely to contain tigers. The surveys evaluated and documented evidence for the presence of tigers, tiger prey and habitat disturbance. Approximately 290 km of mountain trails were evaluated. Infrared remote cameras set up in two reserves captured 400 trap days of data. Thirty formal and numerous informal interviews were conducted with villagers to document wildlife knowledge, livestock management practices, and local land and resource use. We found no evidence of wild South China tigers, few prey species, and no livestock depredation by tigers reported in the last 10 years. Forest areas designated as tiger reserves, averaging about 100 km2 in size, are too small to support even a few tigers because commercial tree farms and other habitat conversion is common, and people and their livestock dominate these fragments. While our survey may not have been exhaustive, and there may be a single tiger or a few isolated tigers still remaining at sites we missed, our results strongly indicate that no remaining viable populations of South China tigers occur within its historical range. We conclude that continued field efforts are needed to ascertain whether any wild tigers may yet persist, concurrent with the need to consider options for the eventual recovery and restoration of wild tiger populations from existing captive populations.
We examine the consequences of panthers introduced from Texas into south Florida, an area housing a small, isolated, inbred and distinct subspecies (Puma concolor coryi). Once part of a continuous, widespread population, panthers became isolated in south Florida more than a century ago. Numbers declined and the occurrence of genetic defects increased. Hoping to reverse the genetic damage, managers introduced eight female panthers from Texas into south Florida in the mid-1990s. This action was highly controversial and we explain the arguments for and against the intervention. We synthesized data systematically collected on the Florida panthers from before, during and after this management intervention. These data include information on movements, breeding, mortality, survivorship and range. There is no evidence that purebred Florida females produce fewer kittens at a later age or less often than do hybrid cats (i.e. those with a Texas ancestor). Hybrid kittens have about a three times higher chance of becoming adults as do purebred ones. Hybrid adult females survive better than purebred females; there is no obvious difference between the males. Males die younger than females, are more often killed by other males and are more likely to disperse longer distances into habitats that are dangerous to them. Hybrids are expanding the known range of habitats panthers occupy and use.
Examines the argument that the evolution of breeding systems of animals and plants has been significantly influenced by the occurrence of inbreeding depression. Contemporary genetic theory of inbreeding depression and heterosis is evaluated, as are the experimental data concerning the strength of inbreeding depression. Partial dominance and epistatic interactions are key causal elements. Mechanisms of inbreeding avoidance include (in plants) homomorphic incompatibility, heterostyly and dioecy; and (in animals) incest avoidance and dispersal. -P.J.Jarvis
Whether inbreeding affects the demography and persistence of natural populations has been questioned. However, new pedigree data from field populations and molecular and analytical tools for tracing patterns of relationship and inbreeding have now enhanced our ability to detect inbreeding depression within and among wild populations. This work reveals that levels of inbreeding depression vary across taxa, populations and environments, but are usually substantial enough to affect both individual and population performance. Data from bird and mammal populations suggest that inbreeding depression often significantly affects birth weight, survival, reproduction and resistance to disease, predation and environmental stress. Plant studies, based mostly on comparing populations that differ in size or levels of genetic variation, also reveal significant inbreeding effects on seed set, germination, survival and resistance to stress. Data from butterflies, birds and plants demonstrate that populations with reduced genetic diversity often experience reduced growth and increased extinction rates. Crosses between such populations often result in heterosis. Such a genetic rescue effect might reflect the masking of fixed deleterious mutations. Thus, it might be necessary to retain gene flow among increasingly fragmented habitat patches to sustain populations that are sensitive to inbreeding.
The fitness consequences of inbreeding and outbreeding are poorly understood in natural populations. We explore two microsatellite-based variables, individual heterozygosity (likely to correlate with recent inbreeding) and a new individual-specific internal distance measure, mean d2 (focusing on events deeper in the pedigree), in relation to two measures of fitness expressed early in life, birth weight and neonatal survival, in 670 red deer calves (Cervus elaphus) born on the Isle of Rum between 1982 and 1996. For comparison, we also analyse inbreeding coefficients derived from pedigrees in which paternity was inferred by molecular methods. Only 14 out of 231 calves (6.1%) had non-zero inbreeding coefficients, and neither inbreeding coefficient nor individual heterozygosity was consistently related to birth weight or neonatal survival. However, mean d2 was consistently related to both fitness measures. Low mean d2 was associated with low birth weight, especially following cold Aprils, in which foetal growth is reduced. Low mean d2 was also associated with low neonatal survival, but this effect was probably mediated by birth weight because fitting birth weight to the neonatal survival model displaced mean d2 as an explanatory variable. We conclude that in the deer population fitness measures expressed early in life do not show evidence of inbreeding depression, but they do show evidence of heterosis, possibly as a result of population mixing. We also demonstrate the practical problems of estimating inbreeding via pedigrees compared with a direct marker-based estimate of individual heterozygosity. We suggest that, together, individual heterozygosity and mean d2, estimated using microsatellites, are useful tools for exploring inbreeding and outbreeding in natural population.
Of the nonprimate mammalian species with developing comparative gene maps, the feline gene map (Felis catus, Order Carnivora, 2N = 38) displays the highest level of syntenic conservation with humans, with as few as 10 translocation exchanges discriminating the human and feline genome organization. To extend this model, a genetic linkage map of microsatellite loci in the feline genome has been constructed including 246 autosomal and 7 X-linked loci. Two hundred thirty-five dinucleotide (dC. dA)n. (dG. dT)n and 18 tetranucleotide repeat loci were identified and genotyped in a two-family, 108-member multigeneration interspecies backcross pedigree between the domestic cat (F. catus) and the Asian leopard cat (Prionailurus bengalensis). Two hundred twenty-nine loci were linked to at least one other marker with a lod score >/=3.0, identifying 34 linkage groups. Representative markers from each linkage group were assigned to specific cat chromosomes by somatic cell hybrid analysis, resulting in chromosomal assignments to 16 of the 19 feline chromosomes. Genome coverage spans approximately 2900 cM, and we estimate a genetic length for the sex-averaged map as 3300 cM. The map has an average intragroup intermarker spacing of 11 cM and provides a valuable resource for mapping phenotypic variation in the species and relating it to gene maps of other mammals, including human.
Separation of proteins by two-dimensional gel electrophoresis (2-DE) coupled with identification of proteins through peptide mass fingerprinting (PMF) by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is the widely used technique for proteomic analysis. This approach relies, however, on the presence of the proteins studied in public-accessible protein databases or the availability of annotated genome sequences of an organism. In this work, we investigated the reliability of using raw genome sequences for identifying proteins by PMF without the need of additional information such as amino acid sequences. The method is demonstrated for proteomic analysis of Klebsiella pneumoniae grown anaerobically on glycerol. For 197 spots excised from 2-DE gels and submitted for mass spectrometric analysis 164 spots were clearly identified as 122 individual proteins. 95% of the 164 spots can be successfully identified merely by using peptide mass fingerprints and a strain-specific protein database (ProtKpn) constructed from the raw genome sequences of K. pneumoniae. Cross-species protein searching in the public databases mainly resulted in the identification of 57% of the 66 high expressed protein spots in comparison to 97% by using the ProtKpn database. 10 dha regulon related proteins that are essential for the initial enzymatic steps of anaerobic glycerol metabolism were successfully identified using the ProtKpn database, whereas none of them could be identified by cross-species searching. In conclusion, the use of strain-specific protein database constructed from raw genome sequences makes it possible to reliably identify most of the proteins from 2-DE analysis simply through peptide mass fingerprinting.
Eight traditional subspecies of tiger (Panthera tigris),of which three recently became extinct, are commonly recognized on the basis of geographic isolation and morphological characteristics. To investigate the species' evolutionary history and to establish objective methods for subspecies recognition, voucher specimens of blood, skin, hair, and/or skin biopsies from 134 tigers with verified geographic origins or heritage across the whole distribution range were examined for three molecular markers: (1) 4.0 kb of mitochondrial DNA (mtDNA) sequence; (2) allele variation in the nuclear major histocompatibility complex class II DRB gene; and (3) composite nuclear microsatellite genotypes based on 30 loci. Relatively low genetic variation with mtDNA,DRB,and microsatellite loci was found, but significant population subdivision was nonetheless apparent among five living subspecies. In addition, a distinct partition of the Indochinese subspecies P. t. corbetti in to northern Indochinese and Malayan Peninsula populations was discovered. Population genetic structure would suggest recognition of six taxonomic units or subspecies: (1) Amur tiger P. t. altaica; (2) northern Indochinese tiger P. t. corbetti; (3) South China tiger P. t. amoyensis; (4) Malayan tiger P. t. jacksoni, named for the tiger conservationist Peter Jackson; (5) Sumatran tiger P. t. sumatrae; and (6) Bengal tiger P. t. tigris. The proposed South China tiger lineage is tentative due to limited sampling. The age of the most recent common ancestor for tiger mtDNA was estimated to be 72,000-108,000 y, relatively younger than some other Panthera species. A combination of population expansions, reduced gene flow, and genetic drift following the last genetic diminution, and the recent anthropogenic range contraction, have led to the distinct genetic partitions. These results provide an explicit basis for subspecies recognition and will lead to the improved management and conservation of these recently isolated but distinct geographic populations of tigers.
In investigating criminal cases of poaching and smuggling involving tigers (Panthera tigris), the number of tiger individuals involved is critical for determining the penalty. Morphological methodologies do not often work because tiger parts do not possess the distinctive characteristics of the individual. Microsatellite DNAs have been proved a reliable marker for the individualization of animals. Seven microsatellite loci derived from domestic cat (Felis catus) were selected to individualize tigers, namely F41, F42, F146, Fca304, Fca391, Fca441 and Fca453. A reference population containing 37 unrelated tigers were used to investigate alleles, allelic frequencies, genotypes and genotype frequencies of each locus. Consequently, the data was used to assess the validity of the combination of seven loci for tiger individualization. All loci were polymorphic and easy to amplify. Three out of the seven loci were significantly departure from the Hardy-Weinberg Equilibrium (P < 0.05). Cumulative discrimination power (DP) calculated with observed genotype frequencies was 0.99999789. Match probability of an individual in the reference population with a random individual in seven loci ranged from 7.34 x 10(-9) to 2.77 x 10(-5). This suggests that combining the seven microsatellite loci provides desirable power to individualize tigers. The combination of seven loci was applied to a case of tiger bone smuggling. Genotypes of all samples were identical in all seven loci, and the P(M) of the evidence samples in the seven loci hit 5.63 x 10(-7), provided evidence that the bones belong to a single tiger.
The biological diversity of our planet is being depleted due to the direct and indirect consequences of human activity. As the size of animal and plant populations decrease, loss of genetic diversity reduces their ability to adapt to changes in the environment, with inbreeding depression an inevitable consequence for many species. This textbook provides a clear and comprehensive introduction to the importance of genetic studies in conservation. The text is presented in an easy-to-follow format with main points and terms clearly highlighted. Each chapter concludes with a concise summary, which, together with worked examples and problems and answers, emphasise the key principles covered. Text boxes containing interesting case studies and other additional information enrich the content throughout, and over 100 beautiful pen and ink portraits of endangered species help bring the material to life.
The number of tiger subspecies is a major conservation issue that is difficult to resolve owing to small fragmented extant populations and limited historical samples in museums, which compromise the rigour of both molecular and morphological taxonomic studies. Rather than considering a static taxonomic approach to geographical variation in the tiger, we consider the changing biogeographical range of the tiger through the last glacial-interglacial cycle, based on habitat associations of modern tiger specimen records, and environmental reconstructions from the Last Glacial Maximum (LGM; approximately 20000 years before present (B.P.)). We regard this cycle as representative of the numerous glacial cycles that span the evolutionary history of the tiger since its appearance in the fossil record about two million years ago, thereby giving a deep-time perspective. The key issue is to determine the extent to which ancestral populations of the tiger were geographically isolated. If no geographical isolation is likely, and gene flow between tiger populations could be maintained until modern times, then diagnosably distinct populations could not have evolved. Our reconstructions show that only two tiger populations were likely to have experienced significant geographical isolation from the main species distribution; these were to the west of Tibet (during the LGM) and on Japan (throughout the glacial cycle). In addition, the LGM is likely to have seen the partial separation of peninsular Malayan and Sunda Islands tigers from mainland populations. From a biogeographical perspective it seems probable that only three contemporary populations were sufficiently separated for the evolution of distinct populations, which can be regarded as subspecies or evolutionary significant units. Therefore, most variation in modern tiger populations is probably clinal, which has important implications for future conservation strategies both in the wild and in captivity.
Chinese tiger (Panthera tigris amoyensis Hilzheimer) was once distributed in the Zhejiang Province, China, but there have not been any tiger sightings in this province since 1985. Fortunately, within the boundaries of the Fengyangshan-baishanzu State Natural Reserve, gamekeepers have found ‘tiger footprints’ and ‘tiger faeces’ many times since 1998. However, these tracks may have been left by the leopard or clouded leopard, which leave similar tracks. The presence of the Chinese tiger in Zhejiang Province was demonstrated using DNA fingerprinting and faecal DNA. The study not only revealed a new habitat for Chinese tigers, Zhejiang Province, but also provided an effective scatology method to identify the distribution of tigers and other wild felines.
The costs of inbreeding in natural populations of mammals are unknown despite their theoretical importance in genetic and sociobiological models and practical applications in conservation biology. A major cost of inbreeding is the reduced survival of inbred young. We estimate this cost from the regression of juvenile survival on the inbreeding coefficient using pedigrees of 40 captive mammalian populations belonging to 38 species. The number of lethal equivalents ranged from –1.4 to 30.3, with a mean of 4.6 and a median of 3.1. There was no significant difference between populations founded with wild‐caught individuals, a mixture of wild‐caught and captive‐born individuals, and individuals of unknown origin. The average cost of a parent‐offspring or full sibling mating was 0.33, that is, mortality was 33% higher in offspring of such matings than in offspring of unrelated parents. This is likely to be an underestimate.
Reports on semen quality of the cheetah (Acinonyx jubatus) indicate that high percentages of abnormal morphs and sperm concentrations, 10 times lower than in domestic cats, are found in all populations. These characteristics are believed to result from unusual genetic homozygosity, hypothesized to have been caused by passage of the species through one or more population bottlenecks during its recent history. In a sample of 12 captive-living males, we found semen characteristics to be equal or inferior to those previously reported for males living in other captive facilities. Ten of these males (83.3%) nevertheless produced pregnancies. Seventeen of 19 pregnancies resulted from matings during a single estrus. This examination of the reproductive potential of males having comparatively inferior ejaculate quality supports the suggestion that husbandry programs may be more significant than physiological impairment in causing the low birth rates of captive cheetahs. These results also have implications for ascertaining fertility thresholds in mammalian populations undergoing increased levels of inbreeding as a consequence of habitat deterioration. © 1993 Wiley-Liss, Inc.
The South China tiger Panthera tigris amoyensis is the rarest of the five living tiger subspecies, the most critically threatened and the closest to extinction. No wild South China tigers have been seen by officials for 25 years and one was last brought into captivity 27 years ago. The 19 reserves listed by the Chinese Ministry of Forestry within the presumed range of the tiger are spatially fragmented and most are too small to support viable tiger populations. Over the last 40 years wild populations have declined from thousands to a scattered few. Despite its plight and occasional anecdotal reports of sightings by local people, no intensive field study has been conducted on this tiger subspecies and its habitat. The captive population of about 50 tigers, derived from six wild-caught founders, is genetically impoverished with low reproductive output. Given the size and fragmentation of potential tiger habitat, saving what remains of the captive population may be the only option left to prevent extinction of this tiger subspecies, and even this option is becoming increasingly less probable. This precarious dilemma demands that conservation priorities be re-evaluated and action taken immediately to decide if recovery of the wild population will be possible.
Fitness is expected to decrease with inbreeding in proportion to the amount of deleterious genetic variation present in a population. The effect of inbreeding on survivorship is usually modeled as a negative exponential relationship, and this model has been widely used to estimate the amount of deleterious genetic varia-tion in populations. Linear regression has traditionally been used to estimate the parameters of the model, including the number of lethal equivalents. This article describes an alternative method for estimating parameters and their confidence limits: the maximum likelihood approach. The accuracy of regression and maxi-mum likelihood estimates of the number of lethal equivalents is compared through simulation. The maximum likelihood approach is found to be both median unbi-ased and capable of estimating confidence limits with nearly the stated degree of accuracy, while the linear regression approach is found to be median biased. The significance of this on previous estimates of inbreeding depression is discussed.
Uncertainty currently exists regarding the extent to which mammalian carnivores suffer from inbreeding depression. In particular, it has been proposed that wolves and species with a similar social structure are adapted to close inbreeding. Empirical data, however, are scarce. This paper provides strong evidence against the contention that natural populations of wolves are resistant to inbreeding depression. We analyzed studbook data of a captive wolf population bred in Scandinavian zoos and found negative effects of inbreeding expressed as reductions in juvenile weight, reproduction, and longevity. The occurrence of an apparently bereditary form of blindness is also associated with inbreeding. Different effects of inbreeding can be attributed to genes originating from different founder pairs, thus indicating that alleles that are deleterious in the homozygous state are fairly common in natural wolf populations.
We estimated the extent of inbreeding depression for juvenile survival in 589 captive-born bighorn sheep, and, unlike an earlier report, found no evidence of significant inbreeding depression. There did not appear to be any overall effect of year of birth, place of birth, subspecies, sex or ancestral inbreeding upon the viability of inbred animals as compared to non-inbred animals. However, for the first few years of data, there was lower survival for inbred than non-inbred offspring. After this period, there was an increase in the viability of inbred offspring, probably reflecting a general improvement in husbandry conditions in the zoos. It should be emphasized that the lack of significant inbreeding depression does not necessarily imply that there may not be inbreeding depression for other traits or in a less benign or more natural environment for juvenile viability.
The Speke's gazelle (Gazella spekei) captive breeding program has been presented as one of the few examples of selection reducing the genetic load of a population and as a potential model for the captive breeding of endangered species founded from a small number of individuals. In this breeding program, three generations of mate selection apparently increased the viability of inbred individuals. We reanalyzed the Speke's gazelle studbook and examined potential causes for the reduction of inbreeding depression. Our analysis indicates that the decrease in inbreeding depression is not consistent with any model of genetic improvement in the herd. Instead, we found that the effect of inbreeding decreased from severe to moderate during the first generation of inbreeding, and that this change is responsible for almost all of the decline in inbreeding depression observed during the breeding program. This eliminates selection as a potential explanation for the decrease in inbreeding depression and suggests that inbreeding depression may be more sensitive to environmental influences than is usually thought.
Resumen: El programa de reproducción en cautiverio para la gacela de Speke (Gazella spekei) ha sido presentado como uno de los pocos ejemplos de selección que reducen la carga genética de una población y un modelo potencial para la reproducción en cautiverio de especies en peligro fundado a partir de un número pequeño de individuos. En este programa de reproducción, tres generaciones de selección de pareja incrementaron aparentemente la viabilidad de individuos con intracruza. Realizamos el registro genealógico de las gacelas de Speke y examinamos las causas potenciales de reducción de depresión por intracruza. Nuestro análisis indica que la disminución en la depresión no es consistente con ningún modelo de mejoramiento genético en el grupo. Sin embargo, encontramos que el efecto de intracruza disminuyó de severo a moderado durante la primera generación de intracruza, y que este cambio es responsable de casi todas las disminuciones de la depresión por intracruza observadas durante el programa de reproducción. Esto elimina a la selección como una explicación potencial de la disminución de la depresión, y sugiere que la depresión por intracruza puede ser más sensible a influencias ambientales de lo que actualmente se cree.
This note reports the occurrence of inbreeding depression in a captive brown bear Ursus arctos population. We analyzed studbook records of brown bears bred in Nordic zoos and found a significant reduction in litter size following an increase of inbreeding. In addition, albinism is associated with inbreeding in this population. The amount of depression is compared to that found in other species. Our results are in disagreement with the contention that mammalian carnivores are adapted to close inbreeding.
Mathematical formulae for the sampling variances of average heterozygosity and Nei's genetic distance are developed. These sampling variances are decomposed into their two components, i.e. the inter-locus and intra-locus variances. The relationship between the number of loci and the number of individuals per locus to be examined for estimating average heterozygosity and genetic distance is also discussed. The utility of the inter-locus variance of heterozygosity for studying the mechanism of maintenance of genetic variability in populations is indicated.
The Florida panther has recently suffered severe range and demographic contraction, leaving a remarkably low level of genetic diversity. This exerts a severe fitness cost, manifested by spermatozoal defects, cryptorchidism, cardiac abnormalities and infectious diseases that threaten the survival of the subspecies.
Inbreeding depression in brown bear
- L André
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L, André n R, Larsson H-O, Ryman N (1996) Inbreeding depression in brown bear. Biol Conserv 76:69–72
Tiger research. Shanghai Scientific and Technical Publishers A genetic linkage map of microsatellites in the domestic cat (Felis catus)
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Introduction to conservation genetics An improved method for estimating inbreeding depression in pedigrees
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