Dynamics of allozyme heterozygosity in Siberian dwarf pine Pinus pumila (Pall.) Regel populations of the Russian Far East: comparison of embryos and maternal plants

Siberian dwarf pine, or Japanese stone pine, Pinus pumila (Pall.) Regel is widespread in eastern Siberia and the Russian Far East; the species is bird-dispersed and has a unique spreading or shrub living form. A mixed mating system (predominant outcrossing with self-pollination and matings of close relatives) leads to the formation of partly inbred progenies in P. pumila, as in the majority of other conifers. The question arises as to whether inbred individuals persist in the reproductive part of a population, which can have negative genetic consequences. The ADH, FDH, FEST, GDH, GOT, IDH, LAP, MNR, MDH, PEPCA, 6-PGD, PGI, PGM, SKDH, and SOD isozyme systems were analyzed to study the dynamics of heterozygosity in four P. pumila natural populations from the Pacific region, optimal for the species. Samples were collected in northern Koryakia, southern Kamchatka (two samples), and the Kunashir Island (Kurils). Wright's fixation index was used to estimate the level of inbreeding in embryos from dormant seeds resulting from free pollination and in maternal plants. A substantial level of inbreeding (F(IS) = 0.124-0.342) was observed in the embryo samples but not in three out of the four adult samples. The inbreeding level at the reproductive age was high only in the sample from Koryakia, which was explained by a relatively young age of plants in the population frequently affected by fires. A general increase in heterozygosity, characteristic of other conifers as well, was attributed to elimination of inbred progenies and by balancing selection for heterozygotes, which is a key factor maintaining allozyme polymorphism in populations.     

Heterosis at Allozyme Loci under Inbreeding and Crossbreeding in PINUS ATTENUATA

The dependence of heterosis at isozyme loci on inbreeding and crossbreeding was studied in 10-yr-old trees of knobcone pine (Pinus attenuata Lemm.). Heterozygosity was determined at 24 polymorphic isozyme loci and related to the rate of vegetative growth and cone production. The inbreds, created by selfpollination, had 46% of the heterozygosity of their mothers; the crossbreds, created by interpopulation crossing, had 155% of the heterozygosity of their mothers. Within the crossbreds, heterozygosity was positively correlated with trunk growth, but negatively correlated with cone production. Results in the crossbreds, however, were strongly influenced by a few individuals that showed unusually slow growth, high reproduction and low heterozygosity. Without those individuals, there was no relationship of heterozygosity to either growth or reproduction.—Within the inbreds, heterozygosity was positively correlated with both trunk growth and cone production. Each locus that was heterozygous in the mothers was calculated to mark about 3% of the genome for identity by descent in the inbred progeny; the total proportion of the genome marked was between 10 and 11%. Using these estimates to relate heterozygosity to the inbreeding coefficient (F) gave estimates of inbreeding depression per unit of F that fell within the range of published values for conifers. The strength of heterosis found among the inbreds suggests that single-locus or multilocus overdominance should be exceedingly difficult to detect in natural populations of predominantly outcrossing species.     

Variability of nuclear microsatellite loci in the populations of Siberian dwarf pine (<Emphasis Type="Italic">Pinus pumila</Emphasis> (Pallas) Regel) from the Russian part of the range

Variability of nuclear microsatellite loci was examined in Siberian dwarf pine. Six microsatellite loci (RPS2, RPS6, RPS12, RPS124, RPS127, Pc18) demonstrated different polymorphism levels in ten populations of Siberian dwarf pine. The average number of alleles per locus was 4.88, the average observed heterozygosity was 0.465, and the average expected heterozygosity was 0.510. About 13% of total genetic variability was explained by the genetic differences between the populations (F _ST = 0.129). Genetic distances between the examined populations of Pinus pumila inferred from the data on the SSR marker frequencies statistically significantly correlated with the geographical distances between the population samples. The level of genetic variability of the populations from Kamchatka Peninsula was lower than that demonstrated by continental and island populations. The genetic differentiation of the Kamchatka–Magadan and other populations of Siberian dwarf pine observed in our study can be explained in terms of their formation from different Pleistocene refugial centers.     

Inbreeding in Pinus radiata. I. The effect of inbreeding on growth, survival and variance

 The effects of inbreeding on growth, survival and variance in a 12-year-old radiata pine trial were studied in five populations each inbred to one of five different levels: outcross (F=0), half-sib (F=0.125), full-sib (F=0.25), selfing (S₁, F=0.5), and two-generations of selfing (S₂, F=0.75). These five populations were derived from a founder population of eight clones. Inbreeding reduced diameter, growth, and survival but increased the variance for diameter. Inbreeding depression at F=0.125, 0.25, 0.5, and 0.75 was 5%, 6%, 15%, and 19% respectively for DBH; −3%, 1%, 7%, and 11% respectively, for survival. The standard deviation for diameter increased by 10%, 10%, 30%, and 25% respectively for F=0.125, 0.25, 0.5, and 0.75 and, similarly, the coefficient of variation increased by 17%, 16%, 53%, and 55% respectively. There were significant differences among the eight founder clones in their response to inbreeding. The best clone in the trial showed no inbreeding depression. Overall, inbreeding depression was found to be linearly related to the inbreeding coefficient F with no significant quadratic effects for any trait at any population level. However, two individual clones had a quadratic relationship with F for DBH and one clone had a similar relationship for survival. A significant correlation (r=0.96) between S₂ and the breeding values of founder clones was observed while the correlation (r=0.58) between S₁ and breeding values was insignificant. The low inbreeding depression in radiata pine relative to other conifers may indicate that historical purging of detrimental alleles through small geographic populations, a higher degree of population subdivision, and the relative high fecundity of inbred progenies has rendered radiata pine an ideal species to use inbreeding as a breeding tool. Received: 10 March 1998 / Accepted: 19 May 1998     

Inbreeding alters a plant-predispersal seed predator interaction

The effect of inbreeding on genetic diversity is expected to decrease plant defences or vigour-related traits that, in turn, can modify the pattern of attack by herbivores. The selective damage caused by herbivores can produce variable fitness costs between inbred and outcrossed progenies influencing the evolution of a species’ plant mating system. By exposing inbred and outcrossed plants to natural conditions of seed predation, we assessed whether inbreeding increases weevil incidence and infestation, and how weevil seed predation affects the fitness of inbred and outcrossed progeny. To test if inbreeding affected the host’s plant quality, we weighed the biomass of weevils developed in inbred and outcrossed progenies. An additional experiment was carried out to examine whether weevils preferentially attack vigorous plants regardless from the level of inbreeding. The average value of leaf size was 21% larger in outcrossed plants than in inbred plants. Likewise, weevil incidence and infestation were 13 and 40%, respectively, higher on outcrossed plants relative to their inbred counterparts. However, the relative impact of seed predation was significantly lower in outcrossed progeny than in inbred progeny. In contrast, inbreeding did not alter host plant quality and weevils developed in inbred and outcrossed plants had a similar biomass. Variations in fruit number were consistently associated with the infestation level in both experiments, whereas leaf size only predicted the number of weevils in one experiment, suggesting that fruit number is the most influential vigour-related characteristic of a weevil attack. These findings indicate that the costs of inbreeding of the interaction D. stramonium-T. soror were higher for inbred plants than for outcrossed plants. The interaction between seed predation and inbreeding depression could prevent the fixation of selfing as a unique reproductive strategy in D. stramonium.     

Genetic structure of Pallas pine (Pinus pallasiana D. Don) populations renewed under extreme conditions

The intensive reforestation of Pallas pine (Pinus pallasiana D. Don) in postfire sites in the native mountainous Crimean populations and at ore-mining dumps of the Krivoi Rog region around previously planted seed-producing trees has been demonstrated. Self-sown progeny that grows in the dump is characterized by better growth and arrives at the reproductive development phase earlier than that growing in a postfire forest. Allele variability at 20 allozyme loci is less in self-sown progeny than in native populations, whereas its level of heterozygosity is similar. The genetic distance (D_N) between self-sown progenies in postfire sites and ore-mining dumps is comparable to that of natural populations.     

Ecogeographic variability and differentiation of Japanese dwarf pine populations in Kamchatka Krai with respect to the characters of generative organs

The assessment of ecogeographic variability and differentiation of 22 cenopopulations of Japanese dwarf pine Pinus pumila (Pall.) Regel (Pinaceae) on the Kamchatka Peninsula and in Koryakia has been carried out in regard to morphological and phenotypic characters of mature seed cones. The viability of seeds in the cones of ten populations has been determined by a radiographic method. A latitudinal nature of phenotypic differentiation of cenopopulations in the region has been revealed. Lower seed viability related to a high percent of seeds without embryos or with underdeveloped embryos has been recorded in the northeastern populations. The average share of viable seeds in the region is 52% and in the northeastern populations it reaches only 6–24%.     

Estimating inbreeding depression in natural plant populations using quantitative and molecular data

Inbreeding and inbreeding depression are important issues in the biology and conservation of natural plant and animal populations, primarily when subpopulation sizes are reduced due to habitat fragmentation. In this study, we propose a method for estimating inbreeding depression in progenies of natural plant populations, combining the estimation of the fixation index by codominant markers with the experimental evaluation of quantitative traits. Our technique estimates apparent inbreeding depression in structured natural populations using the linear regression of phenotypic means on the inbreeding coefficients estimated with codominant markers. This method was applied to data from 112 maternal progenies of 10 natural subpopulations of Eugenia dysenterica DC, a fruiting tree species from the Brazilian savanna (Cerrado). The results show that the proposed method was efficient at detecting the presence of inbreeding depression for seedling emergence and initial growth traits in the species. This corroborates the importance of maintaining high levels of heterozygosity for in situ conservation or genetic restoration of natural populations.     

Disease-mediated inbreeding depression in a large,open population of cooperative crows

Disease-mediated inbreeding depression is a potential cost of living in groups with kin, but its general magnitude in wild populations is unclear. We examined the relationships between inbreeding, survival and disease for 312 offspring, produced by 35 parental pairs, in a large, open population of cooperatively breeding American crows (Corvus brachyrhynchos). Genetic analyses of parentage, parental relatedness coefficients and pedigree information suggested that 23 per cent of parental dyads were first- or second-order kin. Heterozygosity–heterozygosity correlations suggested that a microsatellite-based index of individual heterozygosity predicted individual genome-wide heterozygosity in this population. After excluding birds that died traumatically, survival probability was lower for relatively inbred birds during the 2–50 months after banding: the hazard rate for the most inbred birds was 170 per cent higher than that for the least inbred birds across the range of inbreeding index values. Birds that died with disease symptoms had higher inbreeding indices than birds with other fates. Our results suggest that avoidance of close inbreeding and the absence of inbreeding depression in large, open populations should not be assumed in taxa with kin-based social systems, and that microsatellite-based indices of individual heterozygosity can be an appropriate tool for examining the inbreeding depression in populations where incest and close inbreeding occur.     

Inbreeding and inbreeding depression in a threatened endemic plant,the African violet (Saintpaulia ionantha ssp. grotei), of the East Usambara Mountains,Tanzania

Mating among closely‐related individuals in small and isolated plant populations may result in reduced vigour of the inbred offspring, i.e. inbreeding depression, especially in naturally outbreeding plants. Occurrence of inbreeding and inbreeding depression was studied in Saintpaulia ionantha ssp. grotei, a threatened endemic plant species with a narrow ecological amplitude from the East Usambara Mountains. The level of inbreeding (measured as the fixation index, F) was investigated in twelve populations by analyzing variation at one microsatellite marker locus. The effect of one generation of selfing and outcrossing on the progeny fitness was studied by controlled crosses in two small patches that differ in the level isolation. The fixation index (F) across the populations was on the average 0.21 and varied among the populations from substantial inbreeding (F = 0.58) to surplus heterozygosity (F = −0.29). High inbreeding depression (δ) was observed at early and late stages of the life‐cycle. The isolated patch exhibited lower inbreeding depression than did the non‐isolated patch. The results of this study suggest that inbreeding and subsequent inbreeding depression are potential threats to the survival of Saintpaulia populations.     

Maternal heterozygosity and progeny fitness association in an inbred Scots pine population

Associations between heterozygosity and fitness traits have typically been investigated in populations characterized by low levels of inbreeding. We investigated the associations between standardized multilocus heterozygosity (stMLH) in mother trees (obtained from12 nuclear microsatellite markers) and five fitness traits measured in progenies from an inbred Scots pine population. The traits studied were proportion of sound seed, mean seed weight, germination rate, mean family height of one-year old seedlings under greenhouse conditions (GH) and mean family height of three-year old seedlings under field conditions (FH). The relatively high average inbreeding coefficient (F) in the population under study corresponds to a mixture of trees with different levels of co-ancestry, potentially resulting from a recent bottleneck. We used both frequentist and Bayesian methods of polynomial regression to investigate the presence of linear and non-linear relations between stMLH and each of the fitness traits. No significant associations were found for any of the traits except for GH, which displayed negative linear effect with stMLH. Negative HFC for GH could potentially be explained by the effect of heterosis caused by mating of two inbred mother trees (Lippman and Zamir 2006), or outbreeding depression at the most heterozygote trees and its negative impact on the fitness of the progeny, while their simultaneous action is also possible (Lynch. 1991). However,since this effect wasn’t detected for FH, we cannot either rule out that the greenhouse conditions introduce artificial effects that disappear under more realistic field conditions.     

Relationship between inbreeding depression and inbreeding coefficient in maritime pine (Pinus pinaster)

The relationship between inbreeding depression and inbreeding coefficient (F) for several important traits was investigated in an 11-year trial of maritime pine (Pinus pinaster). Five levels of inbreeding (F=0; 0.125; 0.25; 0.5; 0.75) were obtained in a mating design involving ten plus-trees, or their progenies, as parents (total of 51 families). For F=0.75, the mean inbreeding depressions were 27% for height, 37% for circumference at breast height (63% for bole volume), 23% for basal straightness (better straightness of the inbred trees), and 89% for female fertility (number of cones). Large differences were observed among inbred families for the same level of inbreeding. The evolution of depression with F was more or less linear, depending on the traits. Significant differences among F-levels appeared very early for height (from 5-years of age). Inbreeding depression was much more expressed during unfavorable years than during favorable years for yearly height growth. When compared with other Pinus species, maritime pine appears to be less affected by inbreeding, especially for the percentage of filled seeds and general vigor. A reduced genetic load in maritime pine may result from the evolutionary history of the species and its scattered distribution.     

Genic diversity, genetic structure, and biogeography of Pinus sabiniana Dougl.

Pinus sabiniana Dougl. (grey pine) forms savanna forests in the foothills surrounding California's Great Central Valley. However, its fossil record, which dates from the late Miocene through the Pliocene and Pleistocene, is found exclusively in southern California, south of the species’ present range. A total of twenty-nine isozyme loci, representing eighteen enzyme systems, was assayed to analyse the genetic structure in eight populations of grey pine and attempt to track its migration history from southern to northern California. Expected heterozygosity in the two southernmost samples was 0.128 and 0.150, and heterozygosity tended to decrease with increasing latitude, suggesting the loss of diversity as grey pine dispersed northward. However, genetic distances between populations were very small, even on opposite sides of the treeless Great Central Valley; and estimated time since divergence was 900 to 9000 years at a maximum. Wright's F_ST, the proportion of total genetic diversity among populations, was only 0.057, which is similar to values found in many conifers with continuous distributions. Nm, the number of migrants among populations per generation, was 4.1 to 6.7, depending on estimator, and indicates that gene flow is extensive, or was so in the recent past. In every population, observed heterozygosity was less than expected heterozygosity, and the fixation index, F_IS, for the progeny was 0.128, which indicates a fairly high rate of inbreeding. The genetic similarity of disjunct populations, in combination with paleogeographic and paleoclimatic evidence, suggests that grey pine formed a continuous population throughout the Great Central Valley, perhaps between 12,000 and 8000 yrs BP . Its range became fragmented during the Xerothermic, when it ascended into the foothills. Gaps in its range correlate with late Pleistocene–early Holocene lakes in adjacent basins and with the Sacramento–San Joaquin Delta.     

INBREEDING EFFECTS IN CLARKIA TEMBLORIENSIS (ONAGRACEAE) POPULATIONS WITH DIFFERENT NATURAL OUTCROSSING RATES

Inbreeding depression is commonly observed in natural populations. The deleterious effects of forced inbreeding are often thought to be less pronounced in populations with self-pollinating mating systems than in primarily outcrossing populations. We tested this hypothesis by comparing the performance of plants produced by artificial self- and cross-pollination from three populations whose outcrossing rate estimates were 0.03, 0.26, and 0.58. Outcrossing rates and inbreeding coefficients were estimated using isozyme polymorphisms as genetic markers. Analysis of F statistics suggests that biparental inbreeding as well as self-fertilization contribute to the level of homozygosity in the seed crop. Biparental inbreeding will reduce the heterozygosity of progeny produced by outcrossing, relative to random outcrossing expectations, and hence will reduce the effects of outcrossing versus self-fertilization. Heterotic selection may increase the average heterozygosity during the life history. Selfed and outcrossed seeds from all three populations were equally likely to germinate and survive to reproduce. However, inbreeding depression was observed in fecundity traits of plants surviving to reproduction in all three populations. Even in the population whose natural self-fertilization rate was 97%, plants grown from seed produced by self-pollination produced fewer fruits and less total seed weight than plants grown from outcrossed seed. There was no detectable inbreeding depression in estimated lifetime fitness. Inbreeding effects for all reproductive yield characters were most severe in the accession from the most outcrossing population and least severe in the accession from the most self-fertilizing population.     

Estimation of in situ mating systems in wild sorghum (Sorghum bicolor (L.) Moench) in Ethiopia using SSR-based progeny array data: implications for the spread of crop genes into the wild

Because transgenic sorghum (Sorghum bicolor L.) is being developed for Africa, we investigated the potential for transgenes to spread to conspecific wild/weedy sorghum populations in Ethiopia, which is considered the centre of origin of cultivated sorghum. In the current study, the extent of outcrossing, and uniparental and biparental inbreeding were investigated in seven wild/weedy sorghum populations collected at elevations ranging from 631 to 1709 m. Based on allele frequency data of 1120 progenies and 140 maternal plants from five polymorphic microsatellite markers, outcrossing rates were estimated using standard procedures. The average multilocus outcrossing rate was 0.51, with a range of 0.31–0.65 among populations, and the family outcrossing rate was in the extreme range of 0 to 100%. The highest outcrossing (t _m?=?0.65) was recorded in a weedy population that was intermixed with an improved crop variety in Abuare (Wello region). It was also observed that the inbreeding coefficient of the progenies (F _p) tend to be more than the inbreeding coefficient of both their maternal parents (F _m) and the level of inbreeding expected at equilibrium (F _eq), which is a characteristic of predominantly outbreeding species. Biparental inbreeding was evident in all populations and averaged 0.24 (range = 0.10–0.33). The high outcrossing rates of wild/weedy sorghum populations in Ethiopia indicate a high potential for crop genes (including transgenes) to spread within the wild pool. Therefore, effective risk management strategies may be needed if the introgression of transgenes or other crop genes from improved cultivars into wild or weedy populations is deemed to be undesirable.     

Reduced heterozygosity impairs sperm quality in endangered mammals

Inbreeding causes increases in homozygosity and is commonly associated with reductions in fertility and embryogenesis. Although the mechanisms underlying such effects are unknown, recent work has suggested that inbred males may suffer impaired ejaculate quality, thus providing a functional explanation for reductions in reproductive function in inbred populations. However, the relationship between inbreeding and sperm quality remains controversial, particularly in wild populations where the level of inbreeding is typically estimated using neutral molecular markers. Such markers are thought to reflect genome-wide levels of heterozygosity only under restricted conditions, and rarely in outbred populations. Here we employ a comparative approach that takes account of these criticisms and evaluates the evidence linking inbreeding to reductions in sperm quality in 20 mammal species. We focus on sperm abnormalities and sperm motility, which are key determinants of male fertility in many species. We show that species with reduced mean heterozygosity have impaired ejaculated quality, although subsequent analyses revealed that these effects were confined to endangered populations. Our findings therefore support the notion that inbreeding can severely impair sperm quality while concomitantly addressing criticisms surrounding the use of heterozygosity estimates to estimate the level of inbreeding.     

Simultaneous inbreeding modifies inbreeding depression in a plant–herbivore interaction

Because inbreeding is common in natural populations of plants and their herbivores, herbivore‐induced selection on plants, and vice versa, may be significantly modified by inbreeding and inbreeding depression. In a feeding assay with inbred and outbred lines of both the perennial herb, Vincetoxicum hirundinaria, and its specialist herbivore, Abrostola asclepiadis, we discovered that plant inbreeding increased inbreeding depression in herbivore performance in some populations. The effect of inbreeding on plant resistance varied among plant and herbivore populations. The among‐population variation is likely to be driven by variation in plant secondary compounds across populations. In addition, inbreeding depression in plant resistance was substantial when herbivores were outbred, but diminished when herbivores were inbred. These findings demonstrate that in plant–herbivore interactions expression of inbreeding depression can depend on the level of inbreeding of the interacting species. Furthermore, our results suggest that when herbivores are inbred, herbivore‐induced selection against self‐fertilisation in plants may diminish.     

Increased inbreeding but not homozygosity in small populations of Sabatia angularis (Gentianaceae)

Understanding how the mating system varies with population size in plant populations is critical for understanding their genetic and demographic fates. We examined how the mating system, characterized by outcrossing rate, biparental inbreeding rate, and inbreeding coefficient, and genetic diversity varied with population size in natural populations of the biennial Sabatia angularis. We found a significant, positive relationship between outcrossing and population size. Selfing was as high as 40% in one small population but was only 7% in the largest population. Despite this pattern, observed heterozygosity did not vary with population size, and we suggest that selection against inbred individuals maintains observed heterozygosity in small populations. Consistent with this hypothesis, we found a trend of lower inbreeding coefficients in the maternal than progeny generation in all of the populations, and half of the populations exhibited significant excesses of adult heterozygosity. Moreover, genetic diversity was not related to population size and was similar across all populations examined. Our results suggest that the consequences of increased selfing for population fitness in S. angularis, a species that experiences significant inbreeding depression, will depend on the relative magnitude and consistency of inbreeding depression and the demographic cost of selection for outcrossed progeny in small populations.     

RELATIONSHIP BETWEEN SELF-FERTILITY,ALLOCATION OF GROWTH,AND INBREEDING DEPRESSION IN THREE CONIFEROUS SPECIES

Mortality and growth of self and outcross families of three wind-pollinated, mixed-mating, long-lived conifers, Douglas-fir (Pseudotsuga menziesii), ponderosa pine (Pinus ponderosa), and noble fir (Abies procera) were followed from outplanting to age 26 (25 for noble fir) in spaced plantings at a common test site. Response to inbreeding differed greatly among species over time and in all regards. Only Douglas-fir and noble fir will be contrasted here, because ponderosa pine usually was intermediate to the other two in its response to inbreeding. In earlier reports, compared to noble fir Douglas-fir had a higher rate of primary selfing and larger inbreeding depression in seed set. Douglas-fir continued to have higher inbreeding depression in nursery and early field survival. The species differed in time courses of inbreeding depression in height and in allocation of growth due to crowding. Between ages 6 and 12, the relative elongation rate (dm · dm^?1 · yr^?1) of Douglas-fir was significantly greater in the selfs than in the outcrosses. The response was not observed in noble fir. At final measurement, inbreeding depression in diameter relative to inbreeding depression in height was greater in Douglas-fir than in noble fir. At final measurement inbreeding depression in height was inversely related to inbreeding depression in survival. Cumulative inbreeding depressions from time of fertilization to final measurement were 0.98, 0.94, and 0.83 for Douglas-fir, ponderosa pine, and noble fir, respectively, which indicates that selfs will not contribute to the mature, reproductive populations.     

Inbreeding, heterozygosity and fitness in a reintroduced population of endangered African wild dogs (Lycaon pictus)

It is crucial to understand the genetic health and implications of inbreeding in wildlife populations, especially of vulnerable species. Using extensive demographic and genetic data, we investigated the relationships among pedigree inbreeding coefficients, metrics of molecular heterozygosity and fitness for a large population of endangered African wild dogs (Lycaon pictus) in South Africa. Molecular metrics based on 19 microsatellite loci were significantly, but modestly correlated to inbreeding coefficients in this population. Inbred wild dogs with inbreeding coefficients of ??0.25 and subordinate individuals had shorter lifespans than outbred and dominant contemporaries, suggesting some deleterious effects of inbreeding. However, this trend was confounded by pack-specific effects as many inbred individuals originated from a single large pack. Despite wild dogs being endangered and existing in small populations, findings within our sample population indicated that molecular metrics were not robust predictors in models of fitness based on breeding pack formation, dominance, reproductive success or lifespan of individuals. Nonetheless, our approach has generated a vital database for future comparative studies to examine these relationships over longer periods of time. Such detailed assessments are essential given knowledge that wild canids can be highly vulnerable to inbreeding effects over a few short generations.