Journal of Heredity

Population Genetic Structure of Aldabra Giant Tortoises.

Publication Date: 2010 Aug 30 PMID: 20805288
Authors: Balmer, O. - Ciofi, C. - Galbraith, D. A. - Swingland, I. R. - Zug, G. R. - Caccone, A.
Journal: J Hered

Evolution of population structure on islands is the result of physical processes linked to volcanism, orogenic events, changes in sea level, as well as habitat variation. We assessed patterns of genetic structure in the giant tortoise of the Aldabra atoll, where previous ecological studies suggested population subdivisions as a result of landscape discontinuity due to unsuitable habitat and island separation. Analysis of mitochondrial DNA (mtDNA) control region sequences and allelic variation at 8 microsatellite loci were conducted on tortoises sampled in 3 locations on the 2 major islands of Aldabra. We found no variation in mtDNA sequences. This pattern corroborated earlier work supporting the occurrence of a founding event during the last interglacial period and a further reduction in genetic variability during historical time. On the other hand, significant population structure recorded at nuclear loci suggested allopatric divergence possibly due to geographical barriers among islands and ecological partitions hindering tortoise movements within islands. This is the first attempt to study the population genetics of Aldabra tortoises, which are now at carrying capacity in an isolated terrestrial ecosystem where ecological factors appear to have a strong influence on population dynamics.

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Strong Population Genetic Structure in a Broadcast-Spawning Antarctic Marine Invertebrate.

Publication Date: 2010 Aug 18 PMID: 20720149
Authors: Hoffman, J. I. - Peck, L. S. - Linse, K. - Clarke, A.
Journal: J Hered

Although studies of population genetic structure are commonplace, a strong bias exists toward species from low latitudes and with relatively poor dispersal capabilities. Consequently, we used 280 amplified fragment length polymorphism bands to explore patterns of genetic differentiation among 8 populations of a high latitude broadcast-spawning marine mollusc, the Antarctic limpet Nacella concinna. Over 300 individuals were sampled along a latitudinal gradient spanning the Antarctic Peninsula from Adelaide Island to King George Island (67 degrees -62 degrees S), then to Signy Island (60 degrees S) and South Georgia (54 degrees S). Populations from the Antarctic Peninsula exhibited little genetic structure but were themselves strongly differentiated from both Signy and South Georgia. This finding was analytically highly robust and implies the presence of significant oceanographic barriers to gene flow in a species long regarded as a classic example of a widely dispersing broadcast spawner.

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The Zea mays Sexual Compatibility Gene ga2: Naturally Occurring Alleles, Their Distribution, and Role in Reproductive Isolation.

Publication Date: 2010 Aug 8 PMID: 20696670
Authors: Kermicle, J. L. - Evans, M. M.
Journal: J Hered

Major genes govern the fertilization of teosinte ovules by maize pollen. A pollen-pistil compatibility system different from the previously described systems, Ga1-s and Tcb1-s, was identified among maize lines introgressed with chromosome segments from 2 teosinte populations. The pistil barrier is dominant, and pollen competence is determined by genotype of the individual pollen grain. A major gene governing this incompatibility behaves as a strong allele of ga2, a locus identified previously among maize genetic stocks on the basis of transmission ratio distortion. Additionally, pollen simultaneously carrying both ga2 and Ga2 was functional on Ga2 silks, which have the pistil barrier, indicating that Ga2 conditions acceptance of the pollen grain rather than ga2 conditioning rejection of the pollen grain by Ga2 silks. The strong allele (Ga2-s), a weaker one such as reported among maize genetic stocks (Ga2-w), and an allele having only pollen competence (Ga2-m), or some combination of these, was found in all 13 of the teosinte populations sampled. Sympatric and parapatric maize landraces carried Ga2-m or the presumed null allele ga2, but Ga2-s or Ga2-w was not found. The combination of exclusively Ga2-s teosinte with ga2 maize, which could provide strong reproductive isolation, was not characteristic of the 5, paired populations tested.

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Population Structures of the Red Fox (Vulpes vulpes) on the Hokkaido Island, Japan, Revealed by Microsatellite Analysis.

Publication Date: 2010 Aug 8 PMID: 20696669
Authors: Oishi, T. - Uraguchi, K. - Takahashi, K. - Masuda, R.
Journal: J Hered

In order to examine the population structures of the red fox (Vulpes vulpes) on the Hokkaido Island in Japan, we conducted analysis on 250 foxes from all over the island for 12 microsatellite loci. Assignment tests using the genotype data set showed that they were divided into 6 subpopulations. Of the 6, one was geographically isolated in the southern region and considered definitive subpopulation, whereas the other 5 were not. The slight differences among the latter 5 subpopulations were explained by the high adaptability and long dispersal of the red fox on the Hokkaido Island. Although there are few ecological data to explain the genetic differentiation of the southern population, we have proposed some hypotheses from the present ecological and geohistorical viewpoints. One convincing reason from the ecological viewpoint is the restriction of gene flow to southern Hokkaido from other areas due to geographical isolation resulting from the land shape. The other explanation is the geohistorical division of southern Hokkaido from other regions on the island during the last interglacial age, resulting in the isolation of the fox population.

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Genetic Architecture of Novel Traits in the Hopi Sunflower.

Publication Date: 2010 Aug 8 PMID: 20696668
Authors: Wills, D. M. - Abdel-Haleem, H. - Knapp, S. J. - Burke, J. M.
Journal: J Hered

Following domestication, crop lineages typically undergo diversification either to adapt to disparate habitats or to fill novel agricultural roles. This process has produced the numerous varieties found in modern-day crop germplasm collections. Here, we mapped quantitative trait loci (QTLs) underlying unique traits in the Hopi sunflower, a primitive, Native American domesticate. These traits included a variety of achene (i.e., single-seeded fruit) characters as well as the extremely late flowering time of the Hopi sunflower. Composite interval mapping identified 42 QTLs underlying the 12 traits of interest. Although these QTLs were found on 10 of the 17 sunflower linkage groups, strong genetic correlations were evidenced by the clustering of QTLs across traits in certain genomic regions. The number of QTLs per trait ranged from 2 to 6, and the average QTL explained 14.7% of the variance (range: 2.5-46.9%). The apparent contribution of epistasis was minor, as has previously been observed for domestication-related traits. Unlike typical domestication-related traits in sunflower, the traits under consideration here exhibited a relatively simple genetic basis, with 2 QTL clusters being largely responsible for the unique characteristics of the Hopi sunflower. Based on the rarity of these traits in domesticated sunflower, it would appear that they evolved within the Hopi lineage following domestication. The simple genetic architecture of these traits may be a by-product of genetic constraints imposed by the genetically complex nature of domestication-related traits in sunflower, with the large number of domestication-related QTLs limiting the fraction of the genome that is available for subsequent diversification.

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Recent Trends in Molecular Phylogenetic Analysis: Where to Next?

Publication Date: 2010 Aug 8 PMID: 20696667
Authors: Blair, C. - Murphy, R. W.
Journal: J Hered

The acquisition of large multilocus sequence data is providing researchers with an unprecedented amount of information to resolve difficult phylogenetic problems. With these large quantities of data comes the increasing challenge regarding the best methods of analysis. We review the current trends in molecular phylogenetic analysis, focusing specifically on the topics of multiple sequence alignment and methods of tree reconstruction. We suggest that traditional methods are inadequate for these highly heterogeneous data sets and that researchers employ newer more sophisticated search algorithms in their analyses. If we are to best extract the information present in these data sets, a sound understanding of basic phylogenetic principles combined with modern methodological techniques are necessary.

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Phylogeography of the Marine Otter (Lontra felina): Historical and Contemporary Factors Determining Its Distribution.

Publication Date: 2010 Aug 5 PMID: 20688888
Authors: Vianna, J. A. - Ayerdi, P. - Medina-Vogel, G. - Mangel, J. C. - Zeballos, H. - Apaza, M. - Faugeron, S.
Journal: J Hered

The evolutionary history of a species can be revealed by phylogeographical analysis; nevertheless, not only historical but also contemporary processes can imprint on the distribution of genetic diversity. We report on the phylogeny of Lontra ssp. in South America, and the role of spatial heterogeneity in shaping the distribution and population structure of the endangered marine otter, Lontra felina. Analyzing a total of 2261 bp of mitochondrial DNA (mtDNA) revealed the recent divergence of L. felina from L. provocax. A strong population structure (Phi(st) = 0.83, P < 0.0001) and a significant pattern of isolation by distance were described for L. felina (n = 168) across a wide geographical distribution (13 degrees 53'S to 43 degrees 36'S). Lontra felina mtDNA phylogeny is composed of 2 main clades: a clade from Peru and another composed of Chilean haplotypes. Northern populations show different divergent lineages and higher genetic diversity when compared with more recently colonized southern populations. Furthermore, long sandy beaches seem to act as barriers to dispersal, creating 2 evolutionary significant units in agreement with subspecies previous description, and at least 5 different management units (MUs). At a fine spatial scale, the size of rocky seashore patches, the distance between patches and anthropogenic factors also play important roles in species gene flow.

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Clock genes localize to quantitative trait loci for stage-specific growth in juvenile coho salmon, Oncorhynchus kisutch.

Publication Date: 2010 Sep-Oct PMID: 20566470
Authors: O'Malley, K. G. - McClelland, E. K. - Naish, K. A.
Journal: J Hered

In most organisms, an internal circadian clock coordinates the expression of biological rhythms and enables individuals to anticipate and respond to the seasonally changing environment. There is remarkable conservation of function in the molecular machinery underlying this circadian clock across taxa with 4 canonical proteins interacting to form an autoregulatory feedback loop: CLOCK, CRYPTOCHROME, PERIOD, and BMAL. We mapped duplicated copies of Clock and Cryptochrome in coho salmon (Oncorhynchus kisutch) to determine if these genes localize to quantitative trait loci (QTL) for hatch timing, weight, length, and growth rate measured throughout the juvenile life-history stage. We found that Cryptochrome2b mapped to a QTL region for growth (measured at 304 days post-hatching) on linkage group OKI06. The percentage of variation (PEV) explained by this QTL was 15.2%. Cryptochrome2b was also associated with a marginally nonsignificant QTL for length (measured at 395 days post-hatching). OtsClock1b mapped to a QTL region for growth rate (PEV 10.1%) and length (PEV 10.5%) on linkage group OKI24 (measured at 479 days posthatching). Neither gene localized to QTL for hatch timing or weight. Our findings indicate that the growth rate and length QTL associated with OtsClock1b and Cryptochrome2b are development stage-specific and may result from temporally differentiated gene expression patterns.

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An insertion in the RSPO2 gene correlates with improper coat in the Portuguese water dog.

Publication Date: 2010 Sep-Oct PMID: 20562213
Authors: Parker, H. G. - Chase, K. - Cadieu, E. - Lark, K. G. - Ostrander, E. A.
Journal: J Hered

We recently showed that genes at 3 loci account for the majority of variation in canine fur. Allelic variation at genes controlling length of fur, texture, and curl is responsible for the striking phenotypic variety observed among purebred dogs in the United States today. In this paper, we investigate the phenomenon of "improper coat" (IC) or a coat that is not typical of the breed. IC is occasionally observed among specific breeds, such as the Portuguese Water Dog (PWD), and is characterized by short hair on the head, face, and lower legs, rather than a thick and even coat covering the whole body. The IC is reminiscent of that observed on the curly or flat-coated retriever, thus making such dogs unable to compete effectively in conformation events. We have found that the presence of the wild-type allele, rather than the expected variant allele at the R-spondin 2 (RSPO2) gene, accounts for this phenotype. The development of a genetic test that distinguishes these 2 allelic types would allow breeders to easily avoid producing PWD with ICs.

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A new mutation in MC1R explains a coat color phenotype in 2 "old" breeds: Saluki and Afghan hound.

Publication Date: 2010 Sep-Oct PMID: 20525767
Authors: Dreger, D. L. - Schmutz, S. M.
Journal: J Hered

Melanocortin 1 Receptor (MC1R) has been studied in a wide variety of domestic animals (Klungland et al. 1995; Marklund et al. 1996; Vage et al. 1997; Kijas et al. 1998; Newton et al. 2000; Vage et al. 2003), and also several wild animals (Robbins et al. 1993; Ritland et al. 2001; Eizirik et al. 2003; Nachman et al. 2003; McRobie et al. 2009) in relation to coat color variation. A variety of phenotypic changes have been reported including coat colors from pure black to pure red, as well as some phenotypes with hairs with red and black bands. One phenotype, called grizzle in Salukis and domino in Afghan Hounds, appears to be unique to these 2 old dog breeds. This pattern is characterized by a pale face with a widow's peak above the eyes. The body hairs on the dorsal surface of Salukis and Afghan Hounds have both phaeomelanin and eumelanin portions, even though they had an a(t)/a(t) genotype at ASIP. In addition, all had at least one copy of a newly identified mutation in MC1R, g.233G>T, resulting in p.Gly78Val. This new allele, that we suggest be designated as E(G), is dominant to the E and e (p.Arg306ter) alleles at MC1R but recessive to the E(M) (p.Met264Val) allele. The K(B) allele (p.Gly23del) at DEFB103 and the a(y) allele (p.Ala82Ser and p.Arg83His) of ASIP are epistatic to grizzle and domino.

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Sex determination: genetic models for oysters.

Publication Date: 2010 Sep-Oct PMID: 20525766
Authors: Hedrick, P. W. - Hedgecock, D.
Journal: J Hered

In oysters, sex is determined partly by environment, but previous studies employing controlled crosses suggest that genetic factors are also important. Sex ratios in both full- and half-sib families of the Pacific oyster show paternal control of sex ratio and suggest that a single major gene with 2 genotypes controls sex in the Pacific oyster, with FM oysters being male and FF oysters maturing as male or female. Here, we show that such a model does indeed produce a stable polymorphism for either single or multiple age-class populations, though under limited ranges of f, the probability that an FF individual matures as a female. However, this 2-genotype model cannot explain observed heterogeneity of sex ratios among progeny from different dams within half-sib families. We propose an alternative 3-genotype model that also produces a stable polymorphism, for either single or multiple age-class populations, but over all values of f between zero and one. This model accounts for sex ratio heterogeneity among male half-sib families because it features 2 types of females, a protandric FM and a fixed female FF. Furthermore, the 3-genotype model, accounts for the frequencies of mating types inferred from the observed sex ratios of families more closely than the 2-genotype model. Although the mechanism of sex determination may ultimately prove more complex, simple genetic mechanisms can account for the broad features of sexual maturation in oyster families and the stability of sex ratios in populations.

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Concordant phylogeographies of 2 malaria vectors attest to common spatial and demographic histories.

Publication Date: 2010 Sep-Oct PMID: 20511380
Authors: Pedro, P. M. - Uezu, A. - Sallum, M. A.
Journal: J Hered

The phylogeography of South American lineages is a topic of heated debate. Although a single process is unlikely to describe entire ecosystems, related species, which incur similar habitat limitations, can inform the history for a subsection of assemblages. We compared the phylogeographic patterns of the cytochrome oxidase I marker from Anopheles triannulatus (N = 72) and previous results for A. darlingi (N = 126) in a broad portion of their South American distributions. Both species share similar population subdivisions, with aggregations northeast of the Amazon River, in southern coastal Brazil and 2 regions in central Brazil. The average capital EF, Cyrillic(ST) between these groups was 0.39 for A. triannulatus. Populations northeast of the Amazon and in southeastern Brazil are generally reciprocally monophyletic to the remaining groups. Based on these initial analyses, we constructed the a priori hypothesis that the Amazon and regions of high declivity pose geographic barriers to dispersal in these taxa. Mantel tests confirmed that these areas block gene flow for more than 1000 km for both species. The efficacy of these impediments was tested using landscape genetics, which could not reject our a priori hypothesis but did reject simpler scenarios. Results form summary statistics and phylogenetics suggest that both lineages originated in central Amazonia (south of the Amazon River) during the late Pleistocene (579 000 years ago) and that they followed the same paths of expansion into their contemporary distributions. These results may have implications for other species sharing similar ecological limitations but probably are not applicable as a general paradigm of Neotropical biogeography.

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Phylogeography of 3 North Atlantic Wolffish species (Anarhichas spp.) with phylogenetic relationships within the family Anarhichadidae.

Publication Date: 2010 Sep-Oct PMID: 20511379
Authors: McCusker, M. R. - Bentzen, P.
Journal: J Hered

Phylogenetic analyses of all 4 wolffish species (Atlantic, Spotted, Northern, and Bering wolffishes) and the Wolfeel were assessed with both mitochondrial (D-loop and ND1) and nuclear (amplified fragment length polymorphism) DNA to resolve relationships within the family Anarhichadidae. Species-specific mitochondrial DNA (mtDNA) mutation rates were estimated based on 2 possible dates of divergence between the Pacific and Atlantic lineages. Phylogeographic patterns within each of the 3 North Atlantic wolffishes were investigated with Markov chain Monte Carlo simulations based on mtDNA to determine whether population size changes occurred following the last glaciation and where wolffishes likely survived glaciation. All 3 species of North Atlantic wolffishes showed evidence of postglacial expansion but did not show evidence of persistence in multiple refugia in both the eastern and western Atlantic Ocean. Rather, the data supported persistence in a single refuge, with postglacial expansion into the rest of the range. Nucleotide diversity, in particular, was low in wolffishes compared with other marine fishes, possibly related to reductions in population sizes during the last glaciation.

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Identification of y chromosome genetic variations in Chinese indigenous horse breeds.

Publication Date: 2010 Sep-Oct PMID: 20497969
Authors: Ling, Y. - Ma, Y. - Guan, W. - Cheng, Y. - Wang, Y. - Han, J. - Jin, D. - Mang, L. - Mahmut, H.
Journal: J Hered

Y chromosome acts as a single nonrecombining unit that is male specific and in effect haploid, thus ensuring the preservation of mutational events as a single haplotype via male lines. In this study, 6 Y chromosome-specific microsatellites (SSR) were tested for the patrilineal genetic variations of 573 male samples from Chinese domestic horse (30 breeds), Przewalski's horse, and donkey. All the 6 loci appeared as a haplotype block in Przewalski's horse and the domestic donkey. There were notable differences, however, at Y chromosome markers between horse and donkey. There were 2 haplotypes of Eca.YA16 in the domestic horse breeds, Haplotype A (Allele A: 156 bp) and Haplotype B (Allele B: 152 bp). Allele A was the common allele among 30 horse breeds, and Allele B was found in 11 horse breeds. This is the first description of a Y chromosome variant for horses. The 2 haplotypes of Y chromosome discovered in the domestic horse breeds in China could be helpful in unveiling their intricate genetic genealogy.

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Low satellite DNA variability in natural populations of Drosophila antonietae involved in different evolutionary events.

Publication Date: 2010 Sep-Oct PMID: 20497968
Authors: Franco, F. F. - Sene, F. M. - Manfrin, M. H.
Journal: J Hered

Drosophila antonietae is a cactophilic species that is found in the mesophilic forest of the Parana-Paraguay river basin and in the dunes of the South Atlantic coast of Brazil. Although the genetic structure of the Parana-Paraguay river basin populations has already been established, the relationship between these populations and those on the Atlantic coast is controversial. In this study, we compared 33 repetitive units of pBuM-2 satellite DNA isolated from individuals from 8 populations of D. antonietae in these geographic regions, including some populations found within a contact zone with the closely related D. serido. The pBuM-2 sequences showed low interpopulational variability. This result was interpreted as a consequence of both gene flow among the populations and unequal crossing over promoting homogenization of the tandem arrays. The results presented here, together with those of previous studies, highlight the use of pBuM-2 for solving taxonomic conflicts within the D. buzzatii species cluster.

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Genetic approaches refine ex situ lowland tapir (Tapirus terrestris) conservation.

Publication Date: 2010 Sep-Oct PMID: 20484384
Authors: Goncalves da Silva, A. - Lalonde, D. R. - Quse, V. - Shoemaker, A. - Russello, M. A.
Journal: J Hered

Ex situ conservation management remains an important tool in the face of continued habitat loss and global environmental change. Here, we use microsatellite marker variation to evaluate conventional assumptions of pedigree-based ex situ population management and directly inform a captive lowland tapir breeding program within a range country. We found relatively high levels of genetic variation (N(total) = 41; mean H(E) = 0.67 across 10 variable loci) and little evidence for relatedness among founder individuals (N(founders) = 10; mean relatedness = -0.05). Seven of 29 putative parent-offspring relationships were excluded by parentage analysis based on allele sharing, and we identified 2 individuals of high genetic value to the population (mk
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Low heterozygosity at microsatellite markers in Iberian red deer with small antlers.

Publication Date: 2010 Sep-Oct PMID: 20478822
Authors: Perez-Gonzalez, J. - Carranza, J. - Torres-Porras, J. - Fernandez-Garcia, J. L.
Journal: J Hered

Deer antlers are costly structures subjected to directional sexual selection that may be sensitive to heterozygosity. However, a relationship between heterozygosity and antler development has only been found for select protein-coding loci and MHC genes in one deer species (the white-tailed deer Odocoileus virginianus). Here, we study the relationship between multilocus heterozygosity at 11 microsatellite markers and antler size (AS) in a sample of 367 Iberian red deer males (Cervus elaphus hispanicus) from two study areas with different ecological and genetic conditions. We found that males with very small antlers (10% of the sampled individuals with the lowest values of AS) had lower levels of heterozygosity than those with bigger antlers (significant effect in an analysis of variance, P = 0.011). This relationship was noticeable mainly in situations of low genetic diversity, where the differences in heterozygosity between groups of males were greater. Finally, we conducted analyses to address the hypotheses proposed by the heterozygosity-fitness correlation, and we found the local effect as the most likely hypothesis. Our findings reveal an expected but not previously detected association between low heterozygosity and reduced AS, with implications for red deer evolution and management.

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Genetic analysis of capsule and its associated economic traits in opium poppy (Papaver somniferum L.).

Publication Date: 2010 Sep-Oct PMID: 20472706
Authors: Kumar, B. - Patra, N. K.
Journal: J Hered

Four single crosses (VG20 x SGE48, SGE48 x SG35II, VG26 x SG35II, and SG35II x VG20) in opium poppy (Papaver somniferum L.) were analyzed to study the gene actions involved in the inheritance of quantitative traits, namely plant height, branches/plant, capsules/plant, peduncle length, capsule index, stigmatic rays, straw yield/plant, and morphine content. Simple additive, dominance, and epistatic genetic components were found to be significant for inheritance pattern. Dominance effect (h) was higher than additive effect (d). Digenic interaction indicated the prevalence of dominance x dominance (l) followed by additive x dominance (j) type epistasis. The significance of dominance (h) and dominance x dominance (l) indicated duplicate epistasis for all the traits and crosses except SG35II x VG20 for stigmatic rays. Biparental mating followed by recurrent selection involving desired recombinants may be utilized to improve the component traits.

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Exploring the mechanisms underlying a heterozygosity-fitness correlation for canine size in the Antarctic fur seal Arctocephalus gazella.

Publication Date: 2010 Sep-Oct PMID: 20457623
Authors: Hoffman, J. I. - Forcada, J. - Amos, W.
Journal: J Hered

Although heterozygosity-fitness correlations (HFCs) are widely reported in the literature, most studies use too few markers to allow the proximate mechanisms to be convincingly resolved. Two competing hypotheses have been proposed: the general effect hypothesis, in which marker heterozygosity correlates with genome-wide heterozygosity and hence the inbreeding coefficient f, and the local effect hypothesis, in which one or more of the markers by chance exhibit associative overdominance. To explore the relative contributions of general and local effects in a free-ranging marine mammal population, we revisited a strong HFC found using 9 microsatellite loci for canine tooth size in 84 male Antarctic fur seals Arctocephalus gazella (Hoffman JI, Hanson N, Forcada J, Trathan PN, Amos W. 2010. Getting long in the tooth: a strong positive correlation between canine size and heterozygosity in the Antarctic fur seal Arctocephalus gazella. J Hered.). Increasing the number of markers to 76, we find that heterozygosity is uncorrelated across loci, indicating that inbred individuals are rare or absent. Similarly, while the HFC based on overall heterozygosity is lost, stochastic simulations indicate that when an HFC is due to inbreeding depression, increasing marker number invariably strengthens the HFC. Together these observations argue strongly that the original HFC was not due to inbreeding depression. In contrast, a subset of markers show individually significant effects, and these are nonrandomly distributed across the marker panel, being preferentially associated with markers cloned from other species. Using basic alignment search tool searches, we were able to locate 94% of loci to unique locations in the dog genome, but the local genes are functionally diverse, and the majority cannot be linked directly to growth. Our results suggest that inbreeding depression contributes little if at all to the relationship between heterozygosity and tooth size but that instead the primary mechanism involves associative overdominance. These findings contribute to a growing body of evidence suggesting that general effects are likely to be uncommon in natural populations.

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Getting long in the tooth: a strong positive correlation between canine size and heterozygosity in Antarctic fur seals Arctocephalus gazella.

Publication Date: 2010 Sep-Oct PMID: 20457622
Authors: Hoffman, J. I. - Hanson, N. - Forcada, J. - Trathan, P. N. - Amos, W.
Journal: J Hered

Most studies of heterozygosity-fitness correlations (HFCs) in natural populations relate to fitness traits expressed early in life, whereas traits that are often more difficult to measure such as longevity and adult body size remain elusive. Teeth provide a window on an individual's life history, allowing the reliable estimation of both age and body size. Consequently, we collected paired upper canine teeth and tissue samples from 84 adult male Antarctic fur seals Arctocephalus gazella that died of natural causes at Bird Island, South Georgia. Tooth size is a good predictor of skull and body size both within and across taxa, and we similarly find a strong relationship with skull size in our species. In turn, tooth size is itself predicted strongly by genetic heterozygosity estimated using 9 microsatellites. With only 9 loci, the exact mechanisms involved remain unclear, although the observed pattern appears largely attributable to a small subset of loci, suggesting that associative overdominance rather than inbreeding depression provides the proximate mechanism. In addition, locating these markers in the dog genome reveals proximity to genes involved with fat metabolism and growth. Our study illustrates how canine teeth, and potentially other structures such as tympano-periotic bone, waxy inner earplugs, or otoliths, may be used to explore links between genetic variation and important life-history traits in free-ranging vertebrate populations.

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Quantitative genetics of pigmentation development in 2 populations of the common garter snake, Thamnophis sirtalis.

Publication Date: 2010 Sep-Oct PMID: 20453034
Authors: Westphal, M. F. - Morgan, T. J.
Journal: J Hered

The evolutionary importance of ontogenetic change has been noted since Darwin. However, most analyses of phenotypic evolution focus on single landmark ages. Here, we present an inheritance study that quantifies genetic variation in pigmentation across early-age (i.e., birth to 180 days) development in 2 populations of the common garter snake, Thamnophis sirtalis. The populations are phenotypically distinct and geographically isolated (Manitoba, CA and Northern California, USA). There were highly significant differences between populations for the developmental trajectory of mean pigmentation, with the Manitoba population exhibiting a mean pigmentation level that increased across ontogeny, whereas the California population exhibited mean pigmentation that was invariant across ontogeny. Subsequent quantitative genetic analyses revealed heritable variation at all ages in Manitoba but low levels of phenotypic and genetic variation in California at all ages. A quantitative genetic decomposition of the longitudinal genetic variance-covariance matrix for the age-specific pigmentation phenotypes in the Manitoba population revealed 2 primary orthogonal axes that explained most ( approximately 100%) of the pigmentation variation across ontogeny. The primary axis, explaining 93% of the genetic variation, is an axis of genetic variation whose principal value loadings change from positive to negative across development, suggesting that the most rapid evolutionary response to selection on pigmentation variation will occur in the direction characterized by a tradeoff in early-age versus late-age pigmentation phenotypes. Pigmentation is known to be ecologically important and subject to rapid evolution under selection. Our study shows that significant differences exist between these 2 populations for their capacity to respond to selection on pigmentation which is not only influenced by the population of origin but also by the developmental process. We suggest that developmental timing may be a potential explanatory mechanism for the difference between the populations.

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Development of feline microsatellites and SNPs for evaluating primary cataract candidate genes as cause for cataract in Angolan lions (Panthera leo bleyenberghi).

Publication Date: 2010 Sep-Oct PMID: 20423916
Authors: Philipp, U. - Steinmetz, A. - Distl, O.
Journal: J Hered

Primary cataracts (CAT) are characterized as any form of opacities of the eye lenses and are not accompanied by other diseases. CAT may impair vision depending on their size, location, and their state of progression. In order to investigate the cause of congenital or juvenile CAT in inbred Angolan lions kept in German zoos, we analyzed the genomic sequences of 4 crystalline genes CRYAA, CRYAB, CRYBB2, and CRYBB1. In addition, 10 CAT candidate genes (GJA3, LIM2, CRYGA, CRYGB, CRYGC, CRYGD CRYGS, BFSP2, CRYBA4, and CRYBB1) were analyzed using adjacent microsatellites. We identified 10 single nucleotide polymorphisms in the Angolan lion crystalline genes and 9 segregating microsatellites. Nonparametric and parametric linkage analyses did not reveal any linkage between one of the analyzed markers and CAT. So, we concluded that these genes can be excluded as causative for the familial primary cataract phenotype in these Angolan lions.

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Phylogeography and population genetic structure of the great leaf-nosed bat (Hipposideros armiger) in China.

Publication Date: 2010 Sep-Oct PMID: 20418357
Authors: Xu, L. - He, C. - Shen, C. - Jiang, T. - Shi, L. - Sun, K. - Berquist, S. W. - Feng, J.
Journal: J Hered

The geographical patterns of the genetic structure of Hipposideros armiger in China were assessed by analyzing sequence variation in the mitochondrial DNA control region. Analysis of molecular variance revealed a very strong genetic structure among 5 regions in H. armiger. A neighbor-joining tree, haplotype network construction by TCS and multidimensional scaling plots all showed significant geographic differentiation among 5 regions. The high genetic structure detected in H. armiger could be a consequence of poor dispersal ability, local adaptation, or marked female philopatry. The lack of genetic structure among 3 regions separated by the Gaoligong Range and the Qiongzhou Strait could be due to incomplete lineage sorting. Our estimated times of divergence for H. armiger populations suggested a relatively recent split. The S Yunnan population with the highest genetic diversity and the Hainan population with the lowest genetic diversity should be equally given priority for conservation. Although H. armiger has been shown to carry viruses implicated in human disease, we find little evidence for population mixing. We thus suggest minimizing disturbance to bats' roosting caves for minimizing the potential risk of virus transmission.

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