Levels Of Inbreeding Depression Research Articles

Inbreeding Depression and Genetic Diversity of S1 Lines Corn Plants Under Drought Stress Conditionson Dry Land

Selfing was carried out on the F2 population of corn plants and the S1 line was produced. Selfing is carried out to form pure lines in order to create hybrids. The aim of the research was to determine the magnitude of inbreeding depression, genetic diversity and heritability of leaf angle trait, yield and harvest age of the S1 line of corn plants under drought stress conditions in dry land. The experiment was carried out from March to June 2023 in Gumantar village, North Lombok district. The design used was a randomized block design, two replications. The number of treatments was 31, namely 30 S1 lines and an F2 population. Plantings are given heavy stress. Observed variables include flowering, growth, harvest age, yield components and yield. The level of inbreeding depression is based on the F2 population and is expressed as a percent. Genetic diversity is calculated based on the results of analysis of variance at a significance level of 5 percent. The results showed that inbreeding depression in leaf angle and harvest age of the S1 lines were relatively low; while the yield is classified as high. Broad categories of genetic diversity were obtained in the yield; while the leaf angle and harvest age are relatively narrow. Broad sense heritability was relatively high in the yield; while the leaf angle is classified as medium and the harvest age is relatively low. The selection of S1 lines should be based on yield, namely lines that have the same yield as the F2 population.

Reproductive traits in Pura Raza Española mares manifest inbreeding depression from low levels of homozygosity.

Inbreeding depression is a genetic phenomenon associated with the loss of fitness and mean phenotypic performance due to mating between relatives. Historically, inbreeding coefficients have been estimated from pedigree information. However, the onset of genomic selection programs provides large datasets of individuals genotyped using SNP arrays, enabling more precise assessment of an individual's genomic-level inbreeding using genomic data. One of the traits most sensitive to issues stemming from increased inbreeding is reproduction. This is particularly important in equine, in which fertility is only moderate compared to other livestock species. To explore this further, we evaluated the effect of inbreeding on five reproductive traits (age at first foaling (AFF), average interval between foalings (AIF), total number of foalings (NF), productive life (PL) and reproductive efficiency (RE)) in Pura Raza Español mares using genomic data. Residual predicted phenotypes were obtained by purging these traits through the REML (wgResidual ) and ssGREML (gResidual ) approaches in reproductive data of 29,847 PRE mares using the BLUPF90+ program. Next, we used pedigree-based (Fped ) and ROH-based genomic (FROH ) inbreeding coefficients derived from 1018 animals genotyped with 61,271 SNPs to estimate the inbreeding depression (linear regression). Our results indicated significant levels of inbreeding depression for all reproductive traits, with the exception of the AIF trait when Fped was used. However, all traits were negatively affected by the increase in genomic inbreeding, and FROH was found to capture more inbreeding depression than Fped . Likewise, REML models (ssGREML) using genomic data for estimated predicted residual phenotypes resulted in higher variance explained by the model compared with the models not using genomics (REML). Finally, a segmented regression analysis was conducted to evaluate the effect of inbreeding depression, revealing that the levels of genealogical and genomic homozygosity do not manifest uniformly in reproductive traits. In contrast, the levels of inbreeding depression ranged from low to high as homozygosity increased. This analysis also showed that reproductive traits are very sensitive to inbreeding depression, even with relatively low levels of homozygosity.

Inbreeding depression in a sexually selected weapon and the homologue in females.

Theory predicts that traits with heightened condition dependence, such as sexually selected traits, should be affected by inbreeding to a greater degree than other traits. The presence of environmental stress may compound the negative consequences of inbreeding depression. In this study, we examined inbreeding depression across multiple traits and whether it increased with a known form of environmental stress. We conducted our experiment using both sexes of the sexually dimorphic leaf-footed cactus bug, Narnia femorata (Hemiptera: Coreidae). Adult male cactus bugs have enlarged hind legs used as weapons in male-male contests; these traits, and their homologue in females, have been previously found to exhibit high condition dependence. In this study, we employed a small developmental group size as an environmental stress challenge. Nymph N. femorata aggregate throughout their juvenile stages, and previous work has shown the negative effects of small group size on survivorship and body size. We found evidence of inbreeding depression for survival and seven of the eight morphological traits measured in both sexes. Inbreeding depression was higher for the size of the male weapon and the female homolog. Additionally, small developmental group size negatively affected survival to adulthood. However, small group size did not magnify the effects of inbreeding on morphological traits. These findings support the hypothesis that traits with heightened condition dependence exhibit higher levels of inbreeding depression.

Conservation genetics of endangered Trillium govanianum Wall. ex D. Don – A pharmaceutically prized medicinal plant from the Himalaya and implications for species recovery

Understanding the genetic diversity and population structure of pharmaceutically important endangered plant species is crucial for their conservation and sustainable use. Despite the continuous population decline in Trillium govanianum Wall. ex D. Don, a highly prized medicinal plant endemic to the Himalaya, information regarding its conservation genetics has been lacking. Here, we employed a conservation genetics approach to investigate how drastically declining populations in natural habitats impact population genetic diversity and structure of this endangered species across the Kashmir Himalaya. We used Start codon targeted (SCoT) and Simple sequence repeat (SSR) markers to assess the intra- and inter-population genetic variation in seven sites across the study region. Based on these markers, we found a very low genetic diversity in T. govanianum populations. Very low levels of observed heterozygosity (Ho = 0.000) and that expected (He = 0.064) in the populations indicate high heterozygote deficiency and high levels of inbreeding depression (FIS = 1.000). A high genetic differentiation was observed among the populations for both SCoT (Gst = 0.719) and SSR (Fst = 0.707) markers. Both the markers showed low gene flow, SCoT (Nm = 0.195) and SSR (Nm = 0.119), depicting high among-population variation than within-population variation. Analysis of molecular variance also indicated a higher genetic variation between the populations than within populations. We also observed a significant positive correlation between genetic divergence and geographical distance, indicating that genetic differentiation in T. govanianum follows a pattern of isolation by distance. Bayesian structure and cluster analysis grouped the populations according to their geographical proximity. Further, redundancy analysis (RDA) revealed the presence of one polymorphic locus for each marker with high discriminatory power. Overall, our findings reveal a very low genetic diversity, high levels of inbreeding, and high genetic differentiation among the populations; likely resulting from habitat fragmentation, population isolation, bottleneck effect, low gene flow, and predominantly asexual reproduction currently operative in the species. Finally, based on the insights gained, we discuss the potential implications of our findings in guiding species recovery and habitat rehabilitation of T. govanianum in the Himalaya with conservation lessons for elsewhere in the world.

Contributions of distemper control and habitat expansion to the Amur leopard viability

The Amur leopard (Panthera pardus orientalis) is a critically endangered top predator that struggles on the brink of extinction due to threats such as canine distemper virus (CDV), habitat loss, and inbreeding depression. Here we develop a viability analysis metamodel that combines a traditional individual-based demographic model with an epidemiological model to assess the benefits of alternative population management actions in response to multiple distinct threats. Our results showed an extinction risk of 10.3%-99.9% if no management actions were taken over 100 years under different levels of inbreeding depression. Reducing the risk of CDV infection in Amur leopards through the low-coverage vaccination of leopards and the management of sympatric domestic dogs could effectively improve the survival probability of the leopard population, and with habitat expansion added to these management measures, the population expanded further. Our findings highlight that protecting the Amur leopard necessitates a multifaceted synergistic effort, and controlling multiple threats together may significantly escalate overall viability of a species, especially for small-isolated threatened population. More broadly, our modeling framework could offer critical perspectives and scientific support for conservation planning, as well as specific adaptive management actions for endangered species around the world.

The genetic basis of selfing rate evolution.

Evolution of selfing is common in plant populations, but the genetic basis of selfing rate evolution remains unclear. Although the effects of genetic properties on fixation for mating-unrelated alleles have been investigated, loci that modify the selfing rate (selfing modifiers) differ from mating-unrelated loci in several aspects. Using population genetic models, I investigate the genetic basis of selfing rate evolution. For mating-unrelated alleles, selfing promotes fixation only for recessive mutations, but for selfing modifiers, because the selection coefficient depends on the background selfing rate, selfing can promote fixation even for dominant modifiers. For mating-unrelated alleles, the fixation probability from standing variation is independent of dominance and decreases with an increased background selfing rate. However, for selfing modifiers, the fixation probability peaks at an intermediate selfing rate and when alleles are recessive, because a change of its selection coefficient necessarily involves a change of the inbreeding coefficient, because both depend on the level of inbreeding depression. Furthermore, evolution of selfing involving multiple modifier loci is more likely when selfing is controlled by few large-effect rather than many slight-effect modifiers. I discuss how these characteristics of selfing modifiers have implications for the unidirectional transition from outcrossing to selfing and other empirical patterns.

Long‐term progression of inbreeding depression in a Mediterranean ornithophilous shrub

AbstractThe ornithophilous species Anagyris foetida L. is a Mediterranean shrub with highly fragmented populations and a mixed mating system. In a previous study, we analyzed the first 3 years of the life cycle of two progenies (selfed and outcrossed) grown from seed obtained by hand pollination and planted in an experimental garden in 2005. In that study, we found that inbreeding depression (ID) was manifested both reproductively and vegetatively throughout the life cycle, with male reproductive function being the most affected trait. In the present study, our main aim was to check the progression of the two progenies 12 years after transplantation. For this we analyzed their survival and their vegetative and reproductive traits. According to our results, levels of ID were similar to those obtained in the previous study, with some factors decreased and thus varying with the age of the studied individuals. Vegetative parameters were found to have a greater influence than reproductive ones (δ = 0.56 vs. δ = 0.36) on overall ID. As indicated by the global ID (δ = 0.72) the populations have a mating system that is intermediate between outcrossing and a mixed system. Furthermore, the lower male reproductive capacity of the selfed individuals has been maintained over time. Our study also demonstrates the importance of studying the ID value throughout the life cycle of plants.

Population-level consequences of inheritable somatic mutations and the evolution of mutation rates in plants.

Inbreeding depression, that is the decrease in fitness of inbred relative to outbred individuals, was shown to increase strongly as life expectancy increases in plants. Because plants are thought to not have a separated germline, it was proposed that this pattern could be generated by somatic mutations accumulating during growth, since larger and more long-lived species have more opportunities for mutations to accumulate. A key determinant of the role of somatic mutations is the rate at which they occur, which probably differs between species because mutation rates may evolve differently in species with constrasting life histories. In this paper, I study the evolution of the mutation rates in plants, and consider the population-level consequences of inheritable somatic mutations given this evolution. I show that despite substantially lower somatic and meiotic mutation rates, more long-lived species still tend to accumulate larger amounts of deleterious mutations because of the increased number of opportunities they have to acquire mutations during growth, leading to higher levels of inbreeding depression in these species. However, the magnitude of this increase depends strongly on how mutagenic meiosis is relative to growth, to the point of being close to non-existent in some situations.

Self-Fertilization, Inbreeding, and Yield in Alfalfa Seed Production.

Selfing (self-pollination) is the ultimate form of inbreeding, or mating among close relatives. Selfing can create yield loss when inbreeding depression, defined as a lower survival and reproduction of inbred relative to outbred progeny, is present. To determine the impact of selfing in alfalfa (Medicago sativa L.), we quantified the selfing rate of 32 alfalfa seed production fields located in three regions, namely, the Pacific Northwest (PNW), the Central Valley of California (CEV), and the Imperial Valley of California (IMP). Selfing rates (the proportion of selfed seeds) varied between 5.3 and 30% with an average of 12.2% over the 32 seed production fields. In both the parents and their progeny, we observed an excess of heterozygotes relative to Hardy–Weinberg expectations. We detected notable levels of inbreeding in parents (0.231 ± 0.007 parental inbreeding coefficient) and progeny (0.229 ± 0.005). There were a 15% decrease in the number of seeds per stem (seed set) and a 13% decline in the number of seeds per pod in selfed relative to outcrossed stems, but negligible inbreeding depression for pods per raceme and seed weight. The number of racemes on selfed stems increased significantly in fields with greater selfing rates, supporting the presence of geitonogamous or among flower selfing. Despite the significant level of inbreeding depression, seed set did not decrease in fields with higher selfing rates, where the greater number of racemes on the selfed stems increased the seed set. The effects of the field selfing rate on the seed yield metrics were mostly indirect with direct effects of the number of racemes per stem. Available data indicate that the majority of selfing in alfalfa is pollinator-mediated, and thus, eliminating selfing in alfalfa seed production would require the selection of self-incompatible varieties, which, by eliminating inbreeding depression, would provide a 15% potential increase in seed yield and an increase in future hay yield.

Genome-wide association study and inbreeding depression on body size traits in Qira black sheep (Ovis aries).

Qira black sheep is a famous indigenous sheep breed in China. The objectives of this study are to identify candidate genes related to body size, and to estimate the level of inbreeding depression on body size based on runs of homozygosity in Qira black sheep. Here, 188 adult Qira black sheep were genotyped with a high density (630K) SNP chip and genome-wide association study for body weight and body size traits (including withers height, body slanting length, tail length, chest girth, chest width, and chest depth) were performed using an additive linear model. In consequence, 12 genome- and chromosome-wide significant SNPs and, accordingly, six candidate genes involved in muscle differentiation, metabolism and cell processes were identified. Of them, ZNF704 (zinc finger protein 704) was identified for body weight; AK2 (adenylate kinase 2) and PARK2 (parkin RBR E3 ubiquitin protein ligase) for tail length; MOCOS (molybdenum cofactor sulfurase) and ELP2 (elongator acetyltransferase complex subunit 2) for chest width; and MFAP1 (microfibril associated protein 1) for chest girth. Additionally, inbreeding depressions on body size were observed in the current herd. These results will provide insightful understandings into the genetic mechanisms of adult body size, and into the conservation and utilization of Qira black sheep.

Spread of self-compatibility constrained by an intrapopulation crossing barrier.

Mating system transitions from self-incompatibility (SI) to self-compatibility (SC) are common in plants. In the absence of high levels of inbreeding depression, SC alleles are predicted to spread due to transmission advantage and reproductive assurance. We characterized mating system and pistil-expressed SI factors in 20 populations of the wild tomato species Solanum habrochaites from the southern half of the species range. We found that a single SI to SC transition is fixed in populations south of the Rio Chillon valley in central Peru. In these populations, SC correlated with the presence of the hab-6 S-haplotype that encodes a low activity S-RNase protein. We identified a single population segregating for SI/SC and hab-6. Intrapopulation crosses showed that hab-6 typically acts in the expected codominant fashion to confer SC. However, we found one specific S-haplotype (hab-10) that consistently rejects pollen of the hab-6 haplotype, and results in SI hab-6/hab-10 heterozygotes. We suggest that the hab-10 haplotype could act as a genetic mechanism to stabilize mixed mating in this population by presenting a disadvantage for the hab-6 haplotype. This barrier may represent a mechanism allowing for the persistence of SI when an SC haplotype appears in or invades a population.

On Deleterious Mutations in Perennials: Inbreeding Depression, Mutation Load, and Life-History Evolution.

AbstractIn angiosperms, perennials typically present much higher levels of inbreeding depression than annuals. One hypothesis to explain this pattern stems from the observation that inbreeding depression is expressed across multiple life stages in angiosperms. It posits that increased inbreeding depression in more long-lived species could be explained by differences in the way mutations affect fitness, through the life stages at which they are expressed. In this study, we investigate this hypothesis. We combine a physiological growth model and multilocus population genetics approaches to describe a full genotype-to-phenotype-to-fitness map. We study the behavior of mutations affecting growth or survival and explore their consequences in terms of inbreeding depression and mutation load. Although our results agree with empirical data only within a narrow range of conditions, we argue that they may point us toward the type of traits capable of generating high inbreeding depression in long-lived species-that is, traits under sufficiently strong selection, on which selection decreases sharply as life expectancy increases. Then we study the role deleterious mutations maintained at mutation-selection balance may play in the joint evolution of growth and survival strategies.

Variable inbreeding depression may explain associations between the mating system and herbicide resistance in the common morning glory.

Inbreeding depression is a central parameter underlying mating system variation in nature and one that can be altered by environmental stress. Although a variety of systems show that inbreeding depression tends to increase under stressful conditions, we have very little understanding across most organisms how the level of inbreeding depression may change as a result of adaptation to stressors. In this work we examined the potential that inbreeding depression varied among lineages of Ipomoea purpurea artificially evolved to exhibit divergent levels of herbicide resistance. We examined inbreeding depression in a variety of fitness-related traits in both the growth chamber and in the field, and paired this work with an examination of gene expression changes. We found that, while inbreeding depression was present across many of the traits, lineages artificially selected for increased herbicide resistance often showed no evidence of inbreeding depression in the presence of herbicide, and in fact, showed evidence of outbreeding depression in some traits compared to nonselected control lines and lineages selected for increased herbicide susceptibility. Further, at the transcriptome level, the resistant selection lines had differing patterns of gene expression according to breeding type (inbred vs. outcrossed) compared to the control and susceptible selection lines. Our data together indicate that inbreeding depression may be lessened in populations that are adapting to regimes of strong selection.

Albinism and inbreeding depression in seedlings of the tropical tree, Shorea laxa

ABSTRACT Investigating the level of inbreeding depression is essential to understanding population viability and extinction risk. Albino or chlorophyll-deficient mutants are one of the strongest manifestations of inbreeding depression in plant species, although it is rare to encounter them in a tropical forest. However, during January 2014, we observed a high frequency of albino seedlings in a natural population of Shorea laxa in Lambir Hills National Park in Sarawak, Malaysia. We investigated the fate and compared the cross types of these albino seedlings versus green-leaf seedlings by combining a field survey and genetic analysis using microsatellites. Overall, the albino seedlings survived at least a few months after germination, although they exhibited a 10-fold higher mortality rate than green-leaf seedlings within 19 weeks after germination. Microsatellite analysis confirmed that most albino seedlings (98.3%) were derived from self-pollination. The overall estimated selfing rate was high (61.3%), indicating that reproductive isolation occurred in the mother tree. The observed segregation rate of green:albino types was consistent with the complementation models, indicating that a combination of two dominant genes at two loci are responsible for the green-leaf phenotype in S. laxa. We also found that one albino seedling was derived from outcrossing, suggesting that at least one deleterious gene is maintained in the population. The inbreeding depression of selfed seedlings was exposed as lower initial height of seedlings, which resulted in lower seedling survival. These findings indicate that the population of S. laxa carries recessive deleterious genes and suffers inbreeding depression in selfed offspring.

Breakdown of gametophytic self-incompatibility in subdivided populations.

In many hermaphroditic flowering plants, self-fertilization is prevented by self-incompatibility (SI), often controlled by a single locus, the S-locus. In single isolated populations, the maintenance of SI depends chiefly on inbreeding depression and the number of SI alleles at the S-locus. In subdivided populations, however, population subdivision has complicated effects on both the number of SI alleles and the level of inbreeding depression, rendering the maintenance of SI difficult to predict. Here, we explore the conditions for the invasion of a self-compatible mutant in a structured population. We find that the maintenance of SI is strongly compromised when a population becomes subdivided. We show that this effect is mainly caused by the decrease in the local diversity of SI alleles rather than by a change in the dynamics of inbreeding depression. Strikingly, we also find that the diversity of SI alleles at the whole population level is a poor predictor of the maintenance of SI. We discuss the implications of our results for the interpretation of empirical data on the loss of SI in natural populations.

Genetic characterization and phylogenetic study of Lakor goat from Southwest Maluku Regency based on mitochondrial COI gene.

Aim:This study is aimed at characterizing the genetic and phylogenetic structure of Lakor goats as indigenous livestock from the Southwest Maluku Regency based on mitochondrial COI gene sequences.Materials and Methods:The genomes of 103 follicle samples from Lakor goats, collected from Lakor Island, were analyzed. The polymerase chain reaction was used to amplify 1548 bp of the mitochondrial COI gene using two primer pairs (COIA and COIB). Following sequencing, genetic variation and phylogenetic relationship were established using MEGA version X software.Results:The results of multiple COI gene alignment of the total sequences identified four polymorphic nucleotides that function as genetic markers between individual animals within the Lakor goat population. These correspond to positions 228 (A-G), 519 (G-A), 900 (C-T), and 1266 (T-C). Phylogenetic signals based on the COI gene showed that Lakor goat breed is a monophyletic group or single clade with a bootstrap value of 100% by the neighbor-joining (NJ) and maximum likelihood (ML) evolutionary models. This data indicated that evolutionarily, the Lakor goat breed has a very close kinship with three goat breeds from China: The Meigu goat (KM 244714.1), Chinese Tibet (Capra hircus) (KJ 940969.1), and C. hircus (KP 677510.1). Phylogenetic information based on the cladistics system classified the Lakor goat as a single clade (monophyletic group). The low-genetic diversity within populations indicates that there has been an inbreeding depression occurring at a very high frequency.Conclusion:We conclude that the Lakor goat may be divided into a single clade or monophyletic group based on the COI gene sequence. Four nucleotides were identified that can be used as genetic markers among individual animals within the Lakor goat population, as well as C. hircus and others as derived from GenBank data. The Lakor goat population has a high level of inbreeding depression as a result of geographical isolation, which supports the formation of a monophyletic group with different genetic characteristics, and does not allow the introduction of males from other breeds. Phylogenetic signals indicated that Capra aegagrus (bezoar) is the ancestor of the native goats in Indonesia, including the Lakor goats.

STUDIES ON ECONOMIC TRAITS IN SUCCESSIVE GENERATIONS OF SELFING IN SUGARCANE (SACCHARUM SPP.)

Selfing is one of the classical methods with demonstrated merits to understand parental worthiness, achieving homozygosity and for removing the deleterious genes from the genome. The selfed progenies of S1, S2 and S3 generation of sugarcane clones viz., Co 775, Co 99008, Co 0304, Co 2000-10, Co 0112 and MS 68/47 and S6 and S7 progenies of Co 1148 were studied for homozygosity in successive generations of selfing, level of inbreeding depression and transgressive segregation for important economic traits. A narrow level of variation for HR Brix and wide variation for number of millable canes and moderate level of variation for cane thickness was observed in S1, S2 and S3 generations. The genotypes with least variation among the selfed progenies in preceding generation of selfing did not show the same response in succeeding generations of selfing indicating that the genotypes behave differently in successive generations of selfing during the process of attaining homozygosity. The inbreeding individuals of 1148-13-11-2-237 and 1148-S4-247 depicted the least variation for the traits studied in later generations of selfing. Some of the inbreeding individuals from early generation of selfing of Co 775, MS 68/47, and Co 0112 for number of millable canes, Co 99008, MS 68/47 and Co 0112 for HR Brix and MS 68/47, Co 0112 for cane thickness surpassed their respective parents in their performance. HR Brix was the only trait which was least affected by inbreeding depression and greater level of inbreeding depression was observed for cane thickness. Though inbreeding was observed in early generation of selfing for number of millable canes, no inbreeding depression was observed for the trait in succeeding generations of selfing. Inbreds with higher level of homozygosity in the later generation of selfings viz., S6-2-59 and S6-2-60, S6-2-63 and S6-2-73 and S6-2-66 and S6-2-69 of Co 1148 developed in this study may be utilized for hybrid seed production in sugarcane.

Effects of inbreeding on life-history traits and sexual competency in decorated crickets

Although inbreeding depression in life-history traits has been well characterized, inbreeding effects on mating behaviour and sexually selected traits have been less well studied. Here, we assess levels of inbreeding depression in a number of fitness-related reproductive parameters of female decorated crickets, Gryllodes sigillatus. We predicted that due to direct negative effects of inbreeding and a potential trade-off between reproduction and current survival, as suggested by effects of inbreeding on immunity, inbred females would show significantly reduced reproductive output compared with outbred females. We also examined sex-specific effects of inbreeding on mating competency, focusing specifically on the female's decision to mount a male and the male's ability to transfer a spermatophore. We predicted that any inbreeding depression in sexual competency should be more evident in the success of spermatophore transfer than in female mounting propensity because of the tighter link between mating success and fitness in males than in females. Inbred females produced fewer offspring with longer development times compared with outbred females, results consistent with theory, as inbreeding depression is expected to be more severe for traits more tightly coupled with fitness. Inbreeding also had sex-specific effects on sexual competency. Inbred females were less likely to mount outbred males than were outbred females to mount inbred males. Inbred males were significantly less likely than outbred males to transfer a spermatophore regardless of female inbreeding status. These results reveal that inbreeding may have unexpected consequences for sexual competency and highlight the importance of considering mating behaviour when assessing effects of inbreeding within populations.

Little to no inbreeding depression in a tapeworm with mixed mating.

Meta-studies on hermaphrodites have found a negative relationship between primary selfing rates and levels of inbreeding depression (ID) and, thus, generally support purging in inbred systems. However, in plants, high among-taxa variance in ID results in no difference in the mean ID between outcrossing and mixed-mating taxa. Selective interference likely explains high ID among mixed-mating taxa, whereas low levels of ID among mixed-mating taxa are not as stressed. Among animal hermaphrodites, primarily molluscs, there are little data on mixed-mating systems. To fill a taxonomic and mating system gap, we tested for ID in a mixed-mating tapeworm, Oochoristica javaensis. We provide a direct estimate of ID across infection of an intermediate host by comparing selfing rates at two life history stages. We found little to no evidence for ID, and the level of ID falls in line with what is reported for highly selfing species even though O.javaensis has mixedmating. We discuss this result within the context of kin mating in O.javaensis. Our results emphasize that primary selfing rates alone may be insufficient to classify the inbreeding history in all species when testing for a relationship to ID. Mixed-mating taxa, and possibly some outcrossing taxa, may exhibit low levels of ID if biparental inbreeding is also driving purging. We advocate that ID studies report estimates of inbreeding history (e.g. FIS or identity disequilibrium) from nature-derived adult samples to provide context rather than relying on primary selfing rates alone.

Low levels of inbreeding depression and enhanced fitness in cleistogamous progeny in the annual plantTriodanis perfoliata

The maintenance of outcrossing in cleistogamous plants that produce both open, facultatively outcrossing chasmogamous (CH), and closed, obligate selfing cleistogamous (CL) flowers is puzzling because CL reproduction is thought to be more reliable and less costly. A possible explanation for the maintenance of CH flowers is the avoidance of inbreeding depression. However, inbreeding depression for cleistogamous species has rarely been quantified. In this study, we estimate levels of inbreeding depression in plants from three populations of Triodanis perfoliata (L.) Nieuwl., a dimorphic cleistogamous annual, under greenhouse conditions. Estimates of inbreeding depression at multiple life stages in all three populations were low and often not different from zero. Inbreeding depression at specific life stages varied, with two populations showing later-acting inbreeding depression, which is also found in other selfing species. In two of the study populations, selfed CL progeny outperformed selfed CH progeny, indicating a flower-type effect. The low levels of inbreeding depression and the superior fitness of CL compared with selfed CH flowers that we observed make the maintenance of CH flowers in this system surprising, and suggest that other advantages of outcrossing CH flowers are likely responsible for maintaining mixed mating in this species.