Assessment of the Global Variance Effective Size of Subdivided Populations, and Its Relation to Other Effective Sizes.

The variance effective population size ([Formula: see text]) is frequently used to quantify the expected rate at which a population's allele frequencies change over time. The purpose of this paper is to find expressions for the global [Formula: see text] of a spatially structured population that are of interest for conservation of species. Since [Formula: see text] depends on allele frequency change, we start by dividing the cause of allele frequency change into genetic drift within subpopulations (I) and a second component mainly due to migration between subpopulations (II). We investigate in detail how these two components depend on the way in which subpopulations are weighted as well as their dependence on parameters of the model such a migration rates, and local effective and census sizes. It is shown that under certain conditions the impact of II is eliminated, and [Formula: see text] of the metapopulation is maximized, when subpopulations are weighted proportionally to their long term reproductive contributions. This maximal [Formula: see text] is the sought for global effective size, since it approximates the gene diversity effective size [Formula: see text], a quantifier of the rate of loss of genetic diversity that is relevant for conservation of species and populations. We also propose two novel versions of [Formula: see text], one of which (the backward version of [Formula: see text]) is most stable, exists for most populations, and is closer to [Formula: see text] than the classical notion of [Formula: see text]. Expressions for the optimal length of the time interval for measuring genetic change are developed, that make it possible to estimate any version of [Formula: see text] with maximal accuracy.

Variance effective population size is affected by census size in sub-structured populations.

Measurement of allele frequency shifts between temporally spaced samples has long been used for assessment of effective population size (Ne ), and this 'temporal method' provides estimates of Ne referred to as variance effective size (NeV ). We show that NeV of a local population that belongs to a sub-structured population (a metapopulation) is determined not only by genetic drift and migration rate (m), but also by the census size (Nc ). The realized NeV of a local population can either increase or decrease with increasing m, depending on the relationship between Ne and Nc in isolation. This is shown by explicit mathematical expressions for the factors affecting NeV derived for an island model of migration. We verify analytical results using high-resolution computer simulations, and show that the phenomenon is not restricted to the island model migration pattern. The effect of Nc on the realized NeV of a local subpopulation is most pronounced at high migration rates. We show that Nc only affects local NeV , whereas NeV for the metapopulation as a whole, inbreeding (NeI ), and linkage disequilibrium (NeLD ) effective size are all independent of Nc . Our results provide a possible explanation to the large variation of Ne /Nc ratios reported in the literature, where Ne is frequently estimated by NeV . They are also important for the interpretation of empirical Ne estimates in genetic management where local NeV is often used as a substitute for inbreeding effective size, and we suggest an increased focus on metapopulation NeV as a proxy for NeI .

Entropically Driven Fabrication of Binary Superlattices Assembled from Polymer-Tethered Nanocubes and Nanospheres.

The spontaneous organization of two types of nanoparticles (NPs) with different shapes or properties into binary nanoparticle superlattices (BNSLs) with different configurations has recently attracted significant attention due to the coupling or synergistic effect of the two types of NPs, providing an efficient and general route for designing new functional materials and devices. Here, this work reports the co-assembly of polystyrene (PS) tethered anisotropic gold nanocubes (AuNCs@PS) and isotropic gold NPs (AuNPs@PS) via an emulsion-interface self-assembly strategy. The distributions and arrangements of the AuNCs and spherical AuNPs in the BNSLs can be precisely controlled by adjusting the effective size ratio (λeff ) of the effective diameter (deff ) of the embedded spherical AuNPs to the polymer gap size (L) between the neighboring AuNCs. λeff determines not only the change of the conformational entropy of the grafted polymer chains (∆Scon ) but also the mixing entropy (∆Smix ) of the two types of NPs. During the co-assembly process, ∆Smix tends to be as high as possible, and the -∆Scon tends to be as low as possible, leading to free energy minimization. As a result, well-defined BNSLs with controllable distributions of spherical and cubic NPs can be obtained by tuning λeff . This strategy can also be applied for other NPs with different shapes and atomic properties, thus largely enriching the BNSL library and enabling the fabrication of multifunctional BNSLs, which have potential applications in photothermal therapy, surface-enhanced Raman scattering, and catalysis.

MLNe: Simulating and estimating effective size and migration rate from temporal changes in allele frequencies.

In studies of molecular ecology, conservation biology, and evolutionary biology, the current or recent effective size (Ne) of a population is frequently estimated from the marker genotype data of two or more temporally spaced samples of individuals taken from the population. Despite the developments of numerous Bayesian, likelihood, and moment estimators, only a couple of them can use both temporally and spatially spaced samples of individuals to estimate jointly the effective size (Ne) of and the migration rate (m) into a population. In this note, I describe new implementations of these joint estimators of Ne and m in software MLNe which runs on multiple platforms (Windows, Mac, Linux) with or without a graphical user interface (GUI), and has an integrated simulation module to simulate genotype data for investigating the impacts of various factors (such as sample size and sampling interval) on estimation precision and accuracy, exploits both message passing interface (MPI) and openMP for parallel computations using multiple cores and nodes to speed up analysis. The program does not require data pre-processing and accepts multiple formats of a file of original genotype data and a file of parameters as input. The GUI facilitates data and parameter inputs and produces publication-quality output graphs, while the non-GUI version of software is convenient for batch analysis of multiple datasets as in simulations. MLNe will help advance the analysis of temporal genetic marker data for estimating Ne of and m between populations, which are important parameters that will help biologists for the conservation management of natural and managed populations. MLNe can be downloaded free from the website http://www.zsl.org/science/research/software/.

Demography Predicts Genetic Effective Size in a Desert Stream Fish Community.

AbstractPatterns of genetic diversity and effective size should be predicted by life history traits (intrinsic), landscape properties (extrinsic), and population dynamics. Theoretical models portray complicated relationships among population subdivision, rates of extirpation and recolonization, and metapopulation genetic effective size (metaNe) but make simplifying assumptions about effects of intrinsic and extrinsic factors. Using previously published data sets, we compared estimates of genetic effective size to demographic time-series data gathered for nine dominant species in a desert stream fish community. These species occupy a common desert stream network and experience the same disturbance regime but differ in abundance, distribution, and life history traits that should affect reproduction, dispersal, local persistence, and genetic diversity patterns. Measures of genetic effective size were positively related to network-wide abundance and mean adult density across species and were negatively related to extirpation probability. Comparative data supported the theoretical prediction that population subdivision decreases metapopulation genetic effective size relative to panmictic populations of the same size. Estimates of metaNe reflected differences in intrinsic traits and population dynamics across species measured over ecological timescales. This comparative study exemplifies why ecological differences are important considerations when seeking to preserve genetic diversity.

Individualized Medicine in Africa: Bringing the Practice Into the Realms of Population Heterogeneity.

The declared aim of "personalized", "stratified" or "precision" approaches is to place individual variation, as ascertained through genomic and various other biomarkers, at the heart of Scientific Medicine using it to predict risk of disease or response to therapy and to tailor interventions and target therapies so as to maximize benefit and minimize risk for individual patients and efficiency for the health care system overall. It is often contrasted to current practices for which the scientific base is rooted in concepts of a "universal biology" and a "typical" or "average patient" and in which variation is ignored. Yet both approaches equally overlook the hierarchical nature of human variation and the critical importance of differences between populations. Impact of genetic heterogeneity has to be seen within that context to be meaningful and subsequently useful. In Africa such complexity is compounded by the high effective size of its populations, their diverse histories and the diversity of the environmental terrains they occupy, rendering analysis of gene environment interactions including the establishment of phenotype genotype correlations even more cumbersome. Henceforth "Individualized" methods and approaches can only magnify the shortcomings of universal approaches if adopted without due regard to these complexities. In the current perspective we review examples of potential hurdles that may confront biomedical scientists and analysts in genomic medicine in clinical and public health genomics in Africa citing specific examples from the current SARS-COV2 pandemic and the challenges of establishing reference biobanks and pharmacogenomics reference values.

The role of environment, local adaptation, and past climate fluctuation on the amount and distribution of genetic diversity in two subspecies of Mexican wild Zea mays.

PREMISE: Past climate fluctuations during the Holocene and Pleistocene shaped the distribution of several plant species in temperate areas over the world. Wild maize, commonly known as teosinte, is a good system to evaluate the effects of historical climate fluctuations on genetic diversity due to its wide distribution in Mexico with contrasting environmental conditions. We explored the influence of contemporary factors and historical environmental shifts on genetic diversity, including present and three historical periods using neutral markers. METHODS: We used 22 nuclear microsatellite loci to examine the genetic diversity of 14 populations of Zea mays subsp. parviglumis and 15 populations of Zea mays subsp. mexicana (527 individuals total). We implemented genetic structure analyses to evaluate genetic differentiation between and within subspecies. We applied coalescent-based demographic analysis and species distribution modeling to evaluate the effects of historical environmental shifts. RESULTS: We found 355 alleles in total for the two subspecies and variable levels of diversity in each (Z. mays subsp. parviglumis expected heterozygosity HE = 0.3646-0.7699; Z. mays subsp. mexicana HE = 0.5885-0.7671). We detected significant genetic structure among populations (DEST = 0.4332) with significant heterozygote deficiency (FIS = 0.1796), and variable selfing rates (sg2 = 0.0-0.3090). The Bayesian assignment analysis differentiated four genetic groups. Demographic and species distribution modeling analysis suggested that environmental shifts were influential in the amount of genetic diversity. CONCLUSIONS: Our analyses suggest that the current genetic diversity in teosinte is shaped by factors such as local adaptation and genetic isolation, along with historical environmental fluctuations.

Influence of genetic drift on patterns of genetic variation: The footprint of aquaculture practices in Sparus aurata (Teleostei: Sparidae).

Aquaculture finfish production based on floating cage technology has raised increasing concerns regarding the genetic integrity of natural populations. Accidental mass escapes can induce the loss of genetic diversity in wild populations by increasing genetic drift and inbreeding. Farm escapes probably represent an important issue in the gilthead sea bream (Sparus aurata), which accounted for 76.4% of total escapees recorded in Europe during a 3-year survey. Here, we investigated patterns of genetic variation in farmed and wild populations of gilthead sea bream from the Western Mediterranean, a region of long gilthead sea bream farming. We focused on the role that genetic drift may play in shaping these patterns. Results based on microsatellite markers matched those observed in previous studies. Farmed populations showed lower levels of genetic diversity than wild populations and were genetically divergent from their wild counterparts. Overall, farmed populations showed the smallest effective population size and increased levels of relatedness compared to wild populations. The small broodstock size coupled with breeding practices that may favour the variance in individual reproductive success probably boosted genetic drift. This factor appeared to be a major driver of the genetic patterns observed in the gilthead sea bream populations analysed in the present study. These results further stress the importance of recommendations aimed at maintaining broodstock sizes as large as possible and equal sex-ratios among breeders, as well as avoiding unequal contributions among parents.

Do estimates of contemporary effective population size tell us what we want to know?

Estimation of effective population size (Ne ) from genetic marker data is a major focus for biodiversity conservation because it is essential to know at what rates inbreeding is increasing and additive genetic variation is lost. But are these the rates assessed when applying commonly used Ne estimation techniques? Here we use recently developed analytical tools and demonstrate that in the case of substructured populations the answer is no. This is because the following: Genetic change can be quantified in several ways reflecting different types of Ne such as inbreeding (NeI ), variance (NeV ), additive genetic variance (NeAV ), linkage disequilibrium equilibrium (NeLD ), eigenvalue (NeE ) and coalescence (NeCo ) effective size. They are all the same for an isolated population of constant size, but the realized values of these effective sizes can differ dramatically in populations under migration. Commonly applied Ne -estimators target NeV or NeLD of individual subpopulations. While such estimates are safe proxies for the rates of inbreeding and loss of additive genetic variation under isolation, we show that they are poor indicators of these rates in populations affected by migration. In fact, both the local and global inbreeding (NeI ) and additive genetic variance (NeAV ) effective sizes are consistently underestimated in a subdivided population. This is serious because these are the effective sizes that are relevant to the widely accepted 50/500 rule for short and long term genetic conservation.  The bias can be infinitely large and is due to inappropriate parameters being estimated when applying theory for isolated populations to subdivided ones.

Considerations for monitoring population trends of colonial waterbirds using the effective number of breeders and census estimates.

Detecting trends in population size fluctuations is a major focus in ecology, evolution, and conservation biology. Populations of colonial waterbirds have been monitored using demographic approaches to determine annual census size (Na). We propose the addition of genetic estimates of the effective number of breeders (Nb) as indirect measures of the risk of loss of genetic diversity to improve the evaluation of demographics and increase the accuracy of trend estimates in breeding colonies. Here, we investigated which methods of the estimation of Nb are more precise under conditions of moderate genetic diversity, limited sample sizes and few microsatellite loci, as often occurs with natural populations. We used the wood stork as a model species and we offered a workflow that researchers can follow for monitoring bird breeding colonies. Our approach started with simulations using five estimators of Nb and the theoretical results were validated with empirical data collected from breeding colonies settled in the Brazilian Pantanal wetland. In parallel, we estimated census size using a corrected method based on counting active nests. Both in simulations and in natural populations, the approximate Bayesian computation (ABC) and sibship assignment (SA) methods yielded more precise estimates than the linkage disequilibrium, heterozygosity excess, and molecular coancestry methods. In particular, the ABC method performed best with few loci and small sample sizes, while the other estimators required larger sample sizes and at least 13 loci to not underestimate Nb. Moreover, according to our Nb/Na estimates (values were often ≤0.1), the wood stork colonies evaluated could be facing the loss of genetic diversity. We demonstrate that the combination of genetic and census estimates is a useful approach for monitoring natural breeding bird populations. This methodology has been recommended for populations of rare species or with a known history of population decline to support conservation efforts.

Patterns of Genetic Coding Variation in a Native American Population before and after European Contact.

The effects of European colonization on the genomes of Native Americans may have produced excesses of potentially deleterious features, mainly due to the severe reductions in population size and corresponding losses of genetic diversity. This assumption, however, neither considers actual genomic patterns that existed before colonization nor does it adequately capture the effects of admixture. In this study, we analyze the whole-exome sequences of modern and ancient individuals from a Northwest Coast First Nation, with a demographic history similar to other indigenous populations from the Americas. We show that in approximately ten generations from initial European contact, the modern individuals exhibit reduced levels of novel and low-frequency variants, a lower proportion of potentially deleterious alleles, and decreased heterozygosity when compared to their ancestors. This pattern can be explained by a dramatic population decline, resulting in the loss of potentially damaging low-frequency variants, and subsequent admixture. We also find evidence that the indigenous population was on a steady decline in effective population size for several thousand years before contact, which emphasizes regional demography over the common conception of a uniform expansion after entry into the Americas. This study examines the genomic consequences of colonialism on an indigenous group and describes the continuing role of gene flow among modern populations.

Population genetic structure of Santa Inês sheep in Brazil.

This study aimed to describe the population genetic structure and evaluate the state of conservation of the genetic variability of Santa Inês sheep in Brazil. We used pedigree data of the Santa Inês breed available in electronic processing of the Brazilian Association of Sheep Breeders. A file with 20,206 records, which enabled the calculation of the genetic conservation index (GCI), individual inbreeding coefficient (F), change in inbreeding (ΔF), effective population size (Ne), effective number of founders (ƒe), effective number of ancestors (ƒÉ‘), generation interval (L), average relatedness coefficient of each individual (AR), and Wright's F-statistics (F IT, F IS, and F ST). For pedigree analysis and calculation of population parameters, the program ENDOG was used. The average inbreeding coefficient ([Formula: see text]) was 0.97% and the mean average relatedness ([Formula: see text]) 0.49%. The effective numbers of founders and ancestors were, respectively, 199 and 161. The average values of F and AR increased significantly over the years. The effective population size fluctuated over the years concurrently to oscillations in inbreeding rates, wherein N e reached just 68 in the year 2012. The mean average generation interval was 5.3 years. The Santa Inês breed in Brazil is under genetic drift process, with loss of genetic variation. It requires the implementation of a genetic management plan in the herd, for conservation and improvement of the breed.

gesp: A computer program for modelling genetic effective population size, inbreeding and divergence in substructured populations.

The genetically effective population size (Ne ) is of key importance for quantifying rates of inbreeding and genetic drift and is often used in conservation management to set targets for genetic viability. The concept was developed for single, isolated populations and the mathematical means for analysing the expected Ne in complex, subdivided populations have previously not been available. We recently developed such analytical theory and central parts of that work have now been incorporated into a freely available software tool presented here. gesp (Genetic Effective population size, inbreeding and divergence in Substructured Populations) is R-based and designed to model short- and long-term patterns of genetic differentiation and effective population size of subdivided populations. The algorithms performed by gesp allow exact computation of global and local inbreeding and eigenvalue effective population size, predictions of genetic divergence among populations (GST ) as well as departures from random mating (FIS , FIT ) while varying (i) subpopulation census and effective size, separately or including trend of the global population size, (ii) rate and direction of migration between all pairs of subpopulations, (iii) degree of relatedness and divergence among subpopulations, (iv) ploidy (haploid or diploid) and (v) degree of selfing. Here, we describe gesp and exemplify its use in conservation genetics modelling.

Trapped within the city: integrating demography, time since isolation and population-specific traits to assess the genetic effects of urbanization.

Urbanization is a severe form of habitat fragmentation that can cause many species to be locally extirpated and many others to become trapped and isolated within an urban matrix. The role of drift in reducing genetic diversity and increasing genetic differentiation is well recognized in urban populations. However, explicit incorporation and analysis of the demographic and temporal factors promoting drift in urban environments are poorly studied. Here, we genotyped 15 microsatellites in 320 fire salamanders from the historical city of Oviedo (Est. 8th century) to assess the effects of time since isolation, demographic history (historical effective population size; Ne ) and patch size on genetic diversity, population structure and contemporary Ne . Our results indicate that urban populations of fire salamanders are highly differentiated, most likely due to the recent Ne declines, as calculated in coalescence analyses, concomitant with the urban development of Oviedo. However, urbanization only caused a small loss of genetic diversity. Regression modelling showed that patch size was positively associated with contemporary Ne , while we found only moderate support for the effects of demographic history when excluding populations with unresolved history. This highlights the interplay between different factors in determining current genetic diversity and structure. Overall, the results of our study on urban populations of fire salamanders provide some of the very first insights into the mechanisms affecting changes in genetic diversity and population differentiation via drift in urban environments, a crucial subject in a world where increasing urbanization is forecasted.

A comparison of single-sample estimators of effective population sizes from genetic marker data.

In molecular ecology and conservation genetics studies, the important parameter of effective population size (Ne ) is increasingly estimated from a single sample of individuals taken at random from a population and genotyped at a number of marker loci. Several estimators are developed, based on the information of linkage disequilibrium (LD), heterozygote excess (HE), molecular coancestry (MC) and sibship frequency (SF) in marker data. The most popular is the LD estimator, because it is more accurate than HE and MC estimators and is simpler to calculate than SF estimator. However, little is known about the accuracy of LD estimator relative to that of SF and about the robustness of all single-sample estimators when some simplifying assumptions (e.g. random mating, no linkage, no genotyping errors) are violated. This study fills the gaps and uses extensive simulations to compare the biases and accuracies of the four estimators for different population properties (e.g. bottlenecks, nonrandom mating, haplodiploid), marker properties (e.g. linkage, polymorphisms) and sample properties (e.g. numbers of individuals and markers) and to compare the robustness of the four estimators when marker data are imperfect (with allelic dropouts). Extensive simulations show that SF estimator is more accurate, has a much wider application scope (e.g. suitable to nonrandom mating such as selfing, haplodiploid species, dominant markers) and is more robust (e.g. to the presence of linkage and genotyping errors of markers) than the other estimators. An empirical data set from a Yellowstone grizzly bear population was analysed to demonstrate the use of the SF estimator in practice.

Spatial genetic structure, genetic diversity and pollen dispersal in a harvested population of Astrocaryum aculeatum in the Brazilian Amazon.

BACKGROUND: Astrocaryum aculeatum is a palm tree species native to the tropical regions of South America, exploited commercially by local farmers for the pulp extracted from its fruits. The objective of this research was to compare the genetic diversity between adult plants and seedlings from open-pollinated seeds, quantify the pollen flow and dispersal, the spatial genetic structure, and the effective size of a population that has been continuously harvested for its fruits. The study was carried out in a natural population of A. aculeatum distributed over approximately 8 ha in the State of Amazonas (Brazil), separated by 400 m from the closest neighboring population. In total, 112 potential pollen donors, 12 mother plants and 120 offspring were mapped and genotyped. RESULTS: Genetic diversity was high for parents and the offspring. The fixation indexes for adults (F = -0.035) and offspring (F = -0.060) were negative and not significant. A significant spatial genetic structure was detected for the adult plants (up to the distance of 45 m) indicating short-distance seed dispersal. Paternity analysis detected 9.2 % of pollen immigration and the average distance of pollination within the population was 81 m. The average effective pollination neighborhood area between plants was 1.51 ha. CONCLUSIONS: Our results indicate that substantial introduction of new alleles has occurred in the population through pollen immigration, contributing to the maintenance of genetic diversity. Conservation efforts aimed at maintaining the gene pool of the current population or establishing new populations should utilize offspring from mother plants selected to be spaced by at least 50 m to prevent collecting seeds from relatives.

Temporal trends in genetic data and effective population size support efficacy of management practices in critically endangered dusky gopher frogs (Lithobates sevosus).

Monitoring temporal changes in population genetic diversity and effective population size can provide vital information on future viability. The dusky gopher frog, Lithobates sevosus, is a critically endangered species found only in coastal Mississippi, with low genetic variability as a consequence of isolation and population size reduction. Conservation management practices have been implemented, but their efficacy has not been addressed. We genotyped individuals collected 1997-2014 to determine temporal trends in population genetic variation, structure, and effective size. Observed and expected heterozygosity and allelic richness revealed temporally stable, but low, levels of genetic variation. Positive levels of inbreeding were found in each year. There was weak genetic structure among years, which can be attributed to increased effects of genetic drift and inbreeding in small populations. L. sevosus exhibited an increase in effective population size, and currently has an estimated effective size of 33.0-58.6 individuals, which is approximately half the census size. This large ratio could possibly be explained by genetic compensation. We found that management practices have been effective at maintaining and improving effective size and genetic diversity, but that additional strategies need to be implemented to enhance viability of the species.

Inference of purifying and positive selection in three subspecies of chimpanzees (Pan troglodytes) from exome sequencing.

We study genome-wide nucleotide diversity in three subspecies of extant chimpanzees using exome capture. After strict filtering, Single Nucleotide Polymorphisms and indels were called and genotyped for greater than 50% of exons at a mean coverage of 35× per individual. Central chimpanzees (Pan troglodytes troglodytes) are the most polymorphic (nucleotide diversity, θw = 0.0023 per site) followed by Eastern (P. t. schweinfurthii) chimpanzees (θw = 0.0016) and Western (P. t. verus) chimpanzees (θw = 0.0008). A demographic scenario of divergence without gene flow fits the patterns of autosomal synonymous nucleotide diversity well except for a signal of recent gene flow from Western into Eastern chimpanzees. The striking contrast in X-linked versus autosomal polymorphism and divergence previously reported in Central chimpanzees is also found in Eastern and Western chimpanzees. We show that the direction of selection statistic exhibits a strong nonmonotonic relationship with the strength of purifying selection S, making it inappropriate for estimating S. We instead use counts in synonymous versus nonsynonymous frequency classes to infer the distribution of S coefficients acting on nonsynonymous mutations in each subspecies. The strength of purifying selection we infer is congruent with the differences in effective sizes of each subspecies: Central chimpanzees are undergoing the strongest purifying selection followed by Eastern and Western chimpanzees. Coding indels show stronger selection against indels changing the reading frame than observed in human populations.

Diversidade e estrutura genética de populações de Varronia curassavica Jacq. em restingas da Ilha de Santa Catarina / Genetic diversity and structure of Varronia curassavica Jacq. populations in the restinga of Santa Catarina Island

RESUMO Varronia curassavica Jacq. (Boraginaceae) está presente na vegetação de restinga e apresenta relevantes propriedades medicinais. A espécie é explorada especialmente por comunidades locais e pela indústria farmacêutica, porém, carece de informações ecológicas e genéticas a seu respeito. Nesse contexto, o estudo foi conduzido com o objetivo de caracterizar a diversidade genética de três populações de V. curassavica em áreas de restinga na Ilha de Santa Catarina. Foram coletadas folhas de 50 indivíduos adultos em cada uma das três áreas de estudo e as frequências alélicas das populações foram obtidas a partir de 14 locos alozímicos. Foram encontrados 25 alelos distintos nas três populações, sendo dois alelos exclusivos. As populações apresentaram diversidade genética média de 0,111 e índice de fixação médio de -0,060 (-0,273 até 0,222). Os níveis de diversidade são intermediários, semelhantes aos exibidos por espécies da mesma família ou de características ecológicas semelhantes. Os índices de fixação foram todos significativos e discrepantes entre as populações, sendo que duas delas apresentaram excesso de heterozigotos. A divergência genética interpopulacional foi significativa e igual a 0,079, considerada moderada e sugerindo efeitos de subdivisão populacional. Os níveis de diversidade genética encontrados e a redução populacional causada pela redução e fragmentação dos habitats em que a espécie ocorre sugerem medidas de conservação ex situ e demandam maior rigor na proteção legal de áreas de proteção permanente.

ABSTRACT The Varronia curassavica Jacq. (Boraginaceae) is present in restinga vegetation and shows relevant medicinal properties. The species is exploited by local communities and by the pharmaceutical industry; however, it lacks ecological and genetic information. Thus, this study aimed to characterize the genetic diversity of three V. curassavica populations in restinga areas of Santa Catarina Island. Leaves of 50 adult individuals were sampled in each of the three study areas and the allelic frequencies were obtained from 14 allozyme loci. Twenty-five different alleles were found in the three populations, two of them being exclusive. The populations showed, on average, a genetic diversity of 0,111 and a fixation index of -0,060 (-0,273 to 0,222). The diversity levels are intermediary, similar to those ones owned by species of the same family or with similar ecological traits. The fixation indexes were all significant and discrepant among the populations, with two of them showing excess of heterozygotes. The genetic divergence among populations was significant and equal to 0,079, which is considered moderate and suggests effects of population subdivision. The levels of genetic diversity found and the population decrease caused by reduction and fragmentation of habitats in which the species are present implies in ex situ conservation measures and a higher enforcement of the legal preservation of permanent protected areas.

History of registered Gyr breed in Brazilian Northeast: population structure and genetic improvement of growth traits / Histórico da raça Gir registrada no Nordeste brasileiro: melhoramento genético em características de crescimento e estrutura populacional

This paper provides an evaluation of the population structure, phenotype and genetic trends of registered Gyr herd cattle in northeast Brazil. The study provides important baseline information for the management, conservation and potential population expansion of this economically and culturally important cattle breed. Pedigree data were analyzed for individuals born between 1964 and 2006. Body weight values were adjusted to 205 and 365 days of age for animals born between 1978 and 2006. Phenotypic change of zebu Gyr in northeast Brazil is solely due to environmental improvement. However, there is potential for artificial selection for weight gain in young cattle. Effective population size decreased during the 1990s and the average inbreeding coefficient increased during the studied period. An increase of the effective population size of Gyr in northeast Brazil is strongly recommended, along with an increase in the management of the mating process to prevent inbreeding and to maintain the genetic variability of the breed.

Com o intuito de fornecer subsídios para programas de conservação, seleção e expansão da raça Gir no Nordeste do Brasil, objetivou-se avaliar o histórico do rebanho Gir registrado no nordeste brasileiro, com base na sua estrutura populacional e no progresso genético e fenotípico de características de desenvolvimento ponderal. Foram utilizadas informações de pedigree de animais nascidos no período de 1964 a 2006 e dados dos pesos ajustados aos 205 e 365 dias de idade de bovinos nascidos de 1978 a 2006. O progresso genético para a raça no Nordeste foi ocasionado exclusivamente pelo melhoramento ambiental. O tamanho efetivo da população reduziu a partir da década de 90, e o coeficiente de endogamia médio aumentou durante o período estudado. É imprescindível que o tamanho efetivo da raça Gir do nordeste seja ampliado e que haja maior controle de acasalamentos entre indivíduos aparentados, para prevenção da endogamia e conservação da variabilidade genética e viabilidade da raça.