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The coat color of cats is normally governed by genes found on the X chromosome in both male chromosome XY and female chromosome XX. The meiosis failure in the process of gametogenesis leads to the birth of three-colored male cats caused by an excess of the X chromosome in the male chromosome type XY. The chromosome structure of three-color male cats, called male calico cats, appeared similar to the XXY Klinefelter’s syndrome in human. Mathematical modeling and investigation of the factors that influence the infrequency of male calico cats are our main objectives of this paper. In addition, we also discuss the possible contributions and strategies to overcome the scarcity of these cats. We construct a mathematical model based on a combination of genes in the chromosome that regulates the color of cat coat on the fertilization process. The mathematical model is given as a six-dimensional system of differential equations. Sensitivity analysis is used to investigate the important parameters in the existence of male calico cats. Our finding states that the probability of normal male cats meiosis is a crucial parameter in the maintenance of the existence of male calico cats. Furthermore, one of the strategies that we could recommend in maintaining the existence of male calico cats is minimizing the value of the successful meiosis probability of normal male cats.

This work is devoted to the study of an integro-differential system of equations modelling the genetic adaptation of a pathogen by taking into account both mutation and selection processes. Using the variance of the dispersion in the phenotype trait space as a small parameter we provide a complete picture of the dynamical behaviour of the solutions of the problem. We show that the dynamics exhibits two main and long regimes – those durations are estimated – before the solution finally reaches its long time configuration, the endemic equilibrium. The analysis provided in this work rigorously explains and justifies the complex behaviour observed through numerical simulations of the system. [ABSTRACT FROM AUTHOR]

Speciation is a central process in evolutionary biology and is responsible for the diversity of life on Earth. Although there has been much progress in evolutionary research over the past 150 years, understanding the many facets of speciation remains a challenge. In this synthesis, I focus on the use of an interdisciplinary approach to examine speciation and species delimitation in a group of closely related eucalypts called the green ashes (Eucalyptus subgenus Eucalyptus section Eucalyptus). The green ashes comprise tall trees on fertile soils (e.g. the tallest angiosperm in the world, E. regnans), as well as medium trees and mallees on low-nutrient soils. Previous phylogenetic and population-genetics analyses based on genome-wide scans showed that species boundaries in the green ashes are not always consistent with classifications based on morphology and there was evidence of gene flow across lineages. Genomic analyses also suggested that the green ashes were at varying stages of speciation, with some species being highly genetically differentiated, whereas others were at earlier stages on the speciation continuum. A previous common garden study showed that inter-specific differences in seedling traits were significant, with traits such as leaf width being highly plastic across resource treatments for most species. Overall, this synthesis demonstrated that an interdisciplinary approach incorporating phylogenomics, population genomics and a common garden experiment can provide insights into speciation and species delimitation in the green ash eucalypts. Such an approach may be useful in understanding the evolutionary history of other closely related species in Eucalyptus , as well as other groups of organisms. [ABSTRACT FROM AUTHOR]

There is a growing realisation that cytotype variation within species complexes plays an important role in plant evolution; however, there are relatively few investigations that describe the genetic diversity within and among related cytotypes. In the present study, we analysed patterns of genetic variation in 774 individuals from nine diploid, 14 tetraploid and five mixed ploidy populations of the Lepidosperma costale complex (Cyperaceae) from rocky outcrops in south-west Australia. Application of nuclear (nSSR) and chloroplast (cpSSR) microsatellites suggests that polyploids are of autopolyploid and allopolyploid origin and that polyploidisation is associated with a shift to facultative clonal reproduction, including apomictic reproduction. The newly-discovered putative allopolyploids were commonly associated with disturbed environments, an association commonly reported for allopolyploids. Diploid populations generally contained more genetic diversity than polyploid populations, and there was little genetic differentiation among diploid populations. In contrast, polyploids were characterised by higher heterozygosity and differentiation among populations, but possessed lower within-population diversity. The high differentiation among polyploid populations suggests that polyploids may have formed recurrently and are an important component of morphologically cryptic diversity within the species complex. Ploidy level is a critical factor affecting genetic diversity in this species complex, highlighting the potential contributions of polyploidy to genetic differentiation, and potentially speciation. Genome multiplication (polyploidy) is an important phenomenon in plant evolution. We studied genetic patterns in a group of rare sedges (the Lepidosperma costale species complex) that grow on rocky outcrops in south-west Western Australia. Diploid populations maintained higher genetic diversity than polyploid populations, which were more likely to contain hybrids and reproduce asexually. [ABSTRACT FROM AUTHOR]

Microsatellites are commonly used markers in population genetics and are increasingly being employed to determine population structure in phytoplankton populations. We have developed seven polymorphic microsatellite markers for the domoic-acid producing diatom Pseudo-nitzschia australis . Using these markers, thirty P. australis isolates were genotyped, 10 isolates were from Monterey Bay, California and 20 were from off the northern coast of Oregon. The number of alleles per locus ranged from two to eight and observed heterozygosities ranged from 0.11 to 0.70. All but two of the isolates were genetically distinct and initial population differentiation analysis indicated no significant differences between the Pacific Northwest isolates and the Monterey Bay isolates. Pseudo-nitzschia australis microsatellites appear to be species specific based on cross amplification tests with Pseudo-nitzschia fraudulenta (Cleve) Hasle, Pseudo-nitzschia seriata (Cleve) H.Peragallo, Pseudo-nitzschia pungens (Grunow ex Cleve) and Pseudo-nitzschia multiseries (Hasle) Hasle. [ABSTRACT FROM AUTHOR]

The article focuses on a research related to genetics of population of Cabo Verde using mitochondrial DNA (mtDNA) studies. Topics discussed include obtaining mtDNA variability of the population to complement with previous studies using short tandem repeat (STR) genetic markers, identification of haplotypes and polymorphic nucleotide positions, and characteristics of isolated populations due to high frequency of unique haplotypes.

* Premise of the study: Leucaena comprises 17 diploid species, five tetraploid species, and a complex series of hybrids whose evolutionary histories have been influenced by human seed translocation, cultivation, and subsequent spontaneous hybridization. Here we investigated patterns of evolutionary divergence among diploid Leucaena through comprehensively sampled multilocus phylogenetic and population genetic approaches to address species delimitation, interspecific relationships, hybridization, and the predominant mode of speciation among diploids. * Methods: Parsimony- and maximum-likelihood-based phylogenetic approaches were applied to 59 accessions sequenced for six SCAR-based nuclear loci, nrDNA ITS, and four cpDNA regions. Population genetic comparisons included 1215 AFLP loci representing 42 populations and 424 individuals. * Results: Phylogenetic results provided a well-resolved hypothesis of divergent species relationships, recovering previously recognized clades of diploids as well as newly resolved relationships. Phylogenetic and population genetic assessments identified two cryptic species that are consistent with geography and morphology. * Conclusions: Findings from this study highlight the importance and utility of multilocus data in the recovery of complex evolutionary histories. The results are consistent with allopatric divergence representing the predominant mode of speciation among diploid Leucaena. These findings contrast with the potential hybrid origin of several tetraploid species and highlight the importance of human translocation of seed to the origin of these tetraploids. The recognition of one previously unrecognized species (L. cruziana) and the elevation of another taxon (L. collinsii subsp. zacapana) to specific status (L. zacapana) is consistent with a growing number of newly diagnosed species from neotropical seasonally dry forests, suggesting these communities harbor greater species diversity than previously recognized. [ABSTRACT FROM AUTHOR]

The population genetic structure and historical demography of the flathead mullet Mugil cephalus were investigated using the mtDNA control region (CR) sequences (909–1015 bp) of 126 individuals collected from seven locations in the north-west Pacific between 2005 and 2007. Haplotype diversity ( h = 0·9333–1·000) and nucleotide diversity (π = 0·0046–0·1467) varied greatly among the sampling locations. Phylogenetic analysis of the CR sequences indicated that M. cephalus in the north-west Pacific belongs to two highly divergent lineages (lineages 1 and 2), with the inferred population structure being closely associated with the distribution of both lineages. Two populations were identified, one from the East China Sea and the other from the South China Sea. The former samples were obtained from Taiwan and Qingdao of north China and associated with lineage 1 haplotypes. The latter samples were collected from the Philippines, Pearl River of South China and two samples from Japan, all of which were associated with lineage 2. Japanese samples from Okinawa and Yokosuka had different degrees of mixing between lineages 1 and 2. Historical demographic variables in both populations indicated that Pleistocene glaciations had a strong impact on M. cephalus in the north-west Pacific, resulting in a recent demographic decline of the East China Sea population but in demographic equilibrium for the South China Sea population. Japan appears to be a contact zone between lineages 1 and 2, but it may also be indicative of coexistence between resident and migratory populations. Further global studies are required to clarify the taxonomic status of this cosmopolitan species. [ABSTRACT FROM AUTHOR]

Divergent natural selection, adaptive divergence and gene flow may interact in a number of ways. Recent studies have focused on the balance between selection and gene flow in natural populations, and empirical work has shown that gene flow can constrain adaptive divergence, and that divergent selection can constrain gene flow. A caveat is that phenotypic diversification may be under the direct influence of environmental factors (i.e. it may be due to phenotypic plasticity), in addition to partial genetic influence. In this case, phenotypic divergence may occur between populations despite high gene flow that imposes a constraint on genetic divergence. Plasticity may dampen the effects of natural selection by allowing individuals to rapidly adapt phenotypically to new conditions, thus slowing adaptive genetic divergence. On the other hand, plasticity may promote future adaptive divergence by allowing populations to persist in novel environments. Plasticity may promote gene flow between selective regimes by allowing dispersers to adapt to alternate conditions, or high gene flow may result in the selection for increased plasticity. Here I expand frameworks for understanding relationships among selection, adaptation and gene flow to include the effects of phenotypic plasticity in natural populations, and highlight its importance in evolutionary diversification. [ABSTRACT FROM AUTHOR]

To test whether the genetic diversity of diadromous and landlocked populations of the small puyenGalaxias maculatus(known as jollytail in Australia and inanga in New Zealand) follow the same structuring patterns observed for migratory and non-migratory species of the genusGalaxias. This work also aimed to test whether the genetic structuring of a group of populations could be predicted from differences in the geomorphologic history of the region they inhabit.Eight landlocked populations were sampled from cold-temperate lakes in north-western Patagonia. The study area could be split latitudinally into two sectors that differed in their geomorphology, each of them hosting four populations. The southern sector shows evidence of a higher degree of glacial coverage, and the lakes are probably remnants of a big proglacial palaeolake. Lakes in the northern sector, on the other hand, suggest no common origin.Significant genetic structuring was found among the studied populations (Θ = 0.188), being the highest value reported to date for the species. Significant correlation was found between genetic diversity and lake area and perimeter. Diversity also showed a slight latitudinal variation suggesting the presence of genetically distinct groups of populations. The comparison of populations from the two geographical sectors showed that those from the north had a higher diversity, more private alleles and strong structuring, while those from the south were less diverse and much more homogeneous.Non-migratory populations ofG. maculatusshow much higher values of genetic structuring than those reported for diadromous populations. This follows the pattern seen when comparing migratory and non-migratory species ofGalaxias. This agrees with population genetics theory which predicts that restricted gene flow would result in greater among-population divergence. Also, differences between northern and southern populations agreed with what was predicted by the geomorphologic history of the study area. During the Last Glacial Maximum ice cover in that region may have reduced the habitat ofG. maculatusto a refuge with an impoverished gene pool. When the ice receded, leaving a great proglacial lake, that former population expanded and became fragmented after water levels descended. This resulted in present day lakes harbouring homogeneous populations with reduced diversity. The northern sector, in contrast, was less affected by glaciers, resulting in more geomorphologically stable lakes holding genetically diverse populations. [ABSTRACT FROM AUTHOR]

Kingman's classical theory of the coalescent uncovered the basic pattern of genealogical trees of random samples of individuals in large but time-constant populations. Time is viewed as being discrete and is identified with non-overlapping generations. Reproduction can be very generally taken as exchangeable (meaning that the labelling of individuals in each generation carries no significance). Recent generalisations have dealt with population sizes exhibiting given deterministic or (minor) random fluctuations. We consider population sizes which constitute a stationary Markov chain, explicitly allowing large fluctuations in short times. Convergence of the genealogical tree, as population size tends to infinity, towards the (time-scaled) coalescent is proved under minimal conditions. As a result, we obtain a formula for effective population size, generalising the well-known harmonic mean expression for effective size. [ABSTRACT FROM AUTHOR]

Genetic structure of 120 wild populations of Lolium perenne and 50 populations of L. rigidum was studied using starch gel electrophoresis. Allelic frequencies were obtained from 12 polymorphic isozyme loci. Gene diversity indices (number of alleles (A), observed (Ho) and expected (He) heterozygosity) were significantly higher in L. rigidum (A=3.13; Ho=0.369; He=0.405) than in L. perenne (A=2.72; Ho=0.308; He=0.322). For both species, most of the diversity appeared to be within populations (GST=0.110 and 0.170 for L. perenne and L. rigidum, respectively). Despite this weak genetic differentiation, significant patterns of geographical variation for diversity indices and allele frequencies were observed in L. perenne populations; the three genetic indices (A, Ho, He) showed the same trend of variation, with the lowest values in the north-west part of the distribution area (United Kingdom, Ireland) and the highest ones in the south-east (Turkey, Lebanon, Cyprus, Iraq, Iran). In the same way, as indicated by logistic regression analyses between allelic frequencies and geographical data of L. perenne populations, the latitudinal gradient of allelic frequencies appeared to be more pronounced, although significant relationships also existed with longitude. In contrast, no spatial organization of the diversity was detected in L. rigidum. Hypotheses concerning the taxonomic relationships and the genetic and geographical origins of the two species are discussed. Lolium perenne could be derived from a small bottleneck of L. rigidum populations in the Middle East, and its present distribution area in Europe could be explained either by the extension of primitive agriculture from the fertile crescent, or as a consequence of postglacial recolonization from southern refugia. [ABSTRACT FROM AUTHOR]

Starch gel electrophoresis and morphological characters were used to analyse the geographical variation of 16 populations of Cottus gobio, the bullhead, across three Central European drainage systems. Twenty out of 31 screened allozyme loci were polymorphic. Genetic variability differed considerably among populations (He between 0.008 and 0.099). Populations of the Danube and Elbe were significantly less variable than the Rhine populations. This is interpreted as a consequence of the smaller population sizes of the bullhead within the parts of the Danube and Elbe investigated. An FST value of 0.73 showed that the bullhead is one of the most highly structured freshwater fish species. High genetic distances and morphological differences indicated the existence of two well-defined taxa, one within the Rhine system and one within the Danube and Elbe systems. Genetic distance between these two taxa is about 0.24 (Nei's unbiased distance). Time estimates showed that the two taxa were probably originally separated by palaeogeographical events at the Pliocene/Pleistocene change. [ABSTRACT FROM AUTHOR]

Genetic variation of Anopheles gambiae was analysed to assess interpopulation divergence over a 6000 km distance using short tandem repeat (microsatellite) loci and allozyme loci. Differentiation of populations from Kenya and Senegal measured by allele length variation at five microsatellite loci was compared with estimates calculated from published data on six allozyme loci (Miles, 1978). The average Wright's F[sub ST] of microsatellite loci (0.016) was lower than that of allozymes (0.036). Slatkin's R[sub ST] values for microsatellite loci were generally higher than their F[sub ST] values, but the average R[sub ST] value was virtually identical (0.036) to the average allozyme F[sub ST]. These low estimates of differentiation correspond to an effective migration index (Nm) larger than 3, suggesting that gene flow across the continent is only weakly restricted. Polymorphism of microsatellite loci was significantly higher than that of allozymes, probably because the former experience considerably higher mutation rates. That microsatellite loci did not measure greater interpopulation divergence than allozyme loci suggested constraints on microsatellite evolution. Alternatively, extensive mosquito dispersal, aided by human transportation during the last century, better explains the low differentiation and the similarity of estimates derived from both types of genetic markers. [ABSTRACT FROM AUTHOR]

Seven microsatellite markers identified by probing clones made from a honeybee population from Victoria, Australia with a GA oligonucleotide are polymorphic in collections of honeybees from Iberia. Five of the microsatellites are GA repeats (three perfect repeats, two imperfect repeats, and one interrupted perfect repeat) of two others found in (GA)n-containing clones, one is a perfect AT repeat and one a mononucleotide T repeat. A further perfect GA repeat is monomorphic in the Iberian bees. Primer sequences are given for each of these microsatellites, and for seven others either not amplifying or giving multiple bands under the conditions used, or which were not tested. In all, eighteen microsatellites were found in twelve clones. One clone contained a minisatellite repeat, not assayed for polymorphism. [ABSTRACT FROM AUTHOR]

The main reason for the asthma epidemic in industrialized countries is unknown. While childhood mortality from acute respiratory infection is still high in developing countries where asthma prevalence is low, there might be a suppressed natural selection in industrialized countries with a high asthma prevalence. Children with an inborn Th1 maturation defect might survive by better health care and antibiotic use at the cost of higher asthma and allergy rates. Another distinct group of children maybe represented by those having an environmental Th1 trigger deficit where the immune systems is not being sufficiently exposed in early life. Both, a Th1 maturation and a Th1 trigger defect may contribute to a dual Th1 allergy theory. [ABSTRACT FROM AUTHOR]

It has been established that Nei's measure of the average genetic diversity per locus, H S, and the measure of average differences between isolates with respect to simple mismatch dissimilarity, are identical measures of diversity within populations. The Müller index of diversity can be considered as the correction of Nei's measure for small samples. [ABSTRACT FROM AUTHOR]

A center-based study from the general hospital of Basque country has been performed to evaluate the importance of genetic hemochromatosis among French Basques. A sample of 37 patients from 34 families fulfilling the diagnosis criteria of hemochromatosis was obtained. Only four of them were of Basque origin: two homozygotes for C282Y, one homozygote for H63D, and one heterozygote for C282Y. These results suggest a significant lower prevalence of genetic hemochromatosis in Basques than in people from other French regions (P=0.001). They underline further the biological specificity of this population. [ABSTRACT FROM AUTHOR]

Knowledge of the levels and distribution of genetic diversity is important for designing conservation strategies for threatened and endangered species so as to guarantee sustainable survival of populations and to preserve their evolutionary potential. Picconia azorica is a valuable Azorean endemic species recently classified as endangered. To contribute with information useful for the establishment of conservation programmes, the genetic variability and differentiation among 230 samples from 11 populations collected in three Azorean islands was accessed with eight inter-simple sequence repeat markers. A total of 64 polymorphic loci were detected. The majority of genetic variability was found within populations and no genetic structure was detected between populations and between islands. Also the coefficient of genetic differentiation and the level of gene flow indicate that geographical distances do not act as barriers for gene flow. In order to ensure the survival of populations in situ and ex situ management practices should be considered, including artificial propagation through the use of plant tissue culture techniques, not only for the restoration of habitat but also for the sustainable use of its valuable wood., (Published by Oxford University Press on behalf of the Annals of Botany Company.)

Investigations of the legacy of natural selection in the human genome have proved particularly informative, pinpointing functionally important regions that have participated in our genetic adaptation to the environment. Furthermore, genetic dissection of the intensity and type of selection acting on human genes can be used to predict involvement in different forms and severities of human diseases. We review here the progress made in population genetics studies toward understanding the effects of selection, in its different forms and intensities, on human genome diversity. We discuss some outstanding, robust examples of genes and biological functions subject to strong dietary, climatic and pathogen selection pressures. We also explore the possible relationship between cancer and natural selection, a topic that has been largely neglected because cancer is generally seen as a late-onset disease. Finally, we discuss how the present-day incidence of some diseases of modern societies may represent a by-product of past adaptation to other selective forces and changes in lifestyle. This perspective thus illustrates the value of adopting a population genetics approach in delineating the biological mechanisms that have played a major evolutionary role in the way humans have genetically adapted to different environments and lifestyles over time.