Masticatory function and post-pleistocene evolution in Nubia

The present research focuses on craniofacial variation in Nubia over approximately 10,000 years. Samples were grouped according to their temporal location and subsistence pattern, and represent a transition from a hunting-gathering adaptation (Mesolithic) to a transitional hunting-gathering-agricultural adaptation (A-C Group) and finally to a fully agricultural adaptation (Meroitic/X-Group/Christian). The purposes were: (1) to compare the Mesolithic sample with the later Nubian populations; and (2) to evaluate further the hypothesis that change in Nubian craniofacial morphology was due to changing functional demands associated with the progressive change in subsistence adaptation and associated behavior. The results tend to support recent views that the Nubian Mesolithic population is probably ancestral to later Nubian groups, and that the masticatory-functional hypothesis can best account for craniofacial change among the Nubians since 12,000 B.P. According to this hypothesis systematic reduction in functional demand placed on the masticatory complex from the Mesolithic led, secondarily, to an alteration of the growth of the maxillomandibular complex such that the face became progressively less robust and more inferoposteriorly located relative to the cranial vault. Both the increase in the height of the vault relative to its length, producing a more “globular” appearance, and the reduction in dental size were tertiary, compensatory responses to altered facial size and position.     

Dental morphology and ancestry in Albuquerque, New Mexico Hispanics

The term “Hispanic” groups people from Central and South America and the Caribbean, combining disparate cultures, languages, and ancestry, and masking biological differences. Historical and current admixture patterns within these populations and with indigenous and European-, African-, and/or Asian- derived populations complicate the biological picture. Although “Hispanic” has little biological meaning, it is used widely in epidemiology, disease management, and forensics as a biologically significant group. An interdisciplinary approach combining historical, cultural, and biological data can characterize regional and temporal differences between Hispanic populations.We examined biological distances with a population of central New Mexico Hispanics, as a case study of the local specificity of population history. We collected dental morphological trait frequencies from samples of recent Albuquerque-area Hispanic Americans and several ancestral and contemporary groups. To explore regional admixture patterns we calculated biological distances using the modified Mahalanobis D² statistic. Our results indicate that Albuquerque Hispanics are more similar to their European and African ancestral groups than to Native Americans in New Mexico. Additionally, their affinity to Native Americans is greater with prehistoric rather than contemporary samples. We argue that these results reflect a local rather than pan-Hispanic admixture pattern; they underscore that populations are better understood at the local and regional levels. It is undesirable to make sweeping biological generalizations for groups known to be geographically and genetically disparate. This research is part of a growing trend in biological research concerning Hispanics and other groups—an emphasis on local samples, informed by historical, cultural, and biological factors.     

An examination of Nubian and Egyptian biological distances: Support for biological diffusion or in situ development?

Many authors have speculated on Nubian biological evolution. Because of the contact Nubians had with other peoples, migration and/or invasion (biological diffusion) were originally thought to be the biological mechanism for skeletal changes in Nubians. Later, a new hypothesis was put forth, the in situ hypothesis. The new hypothesis postulated that Nubians evolved in situ, without much genetic influence from foreign populations. This study examined 12 Egyptian and Nubian groups in an effort to explore the relationship between the two populations and to test the in situ hypothesis. Data from nine cranial nonmetric traits were assessed for an estimate of biological distance, using Mahalanobis D² with a tetrachoric matrix. The distance scores were then input into principal coordinates analysis (PCO) to depict the relationships between the two populations. PCO detected 60% of the variation in the first two principal coordinates. A plot of the distance scores revealed only one cluster; the Nubian and Egyptian groups clustered together. The grouping of the Nubians and Egyptians indicates there may have been some sort of gene flow between these groups of Nubians and Egyptians. However, common adaptation to similar environments may also be responsible for this pattern. Although the predominant results in this study appear to support the biological diffusion hypothesis, the in situ hypothesis was not completely negated.     

Dental reduction in post-pleistocene Nubia

Tooth size changes among Nubian archaeological populations dating from the Mesolithic through the Christian era, a period of approximately 12,000 years, are analyzed. Standard length and breadth dimensions of all permanent teeth from several cultural horizons are combined to form three large samples: Mesolithic, 10000-70000 B.C.; Agriculturalist, 3300-1100 B.C. (A-group, C-group, Pharaonic); and Intensive Agriculturalist, A.D. 0-1400 (Meroitic, X-Group, Christian). Such information not only fills a void in the knowledge of Nubian skeletal biology, but also provides a much needed African reference point for the comparison of tooth size data among anatomically modern Homo sapiens from various regions of the world. Changes in mean tooth size and associated t-tests reveal strong and significant reduction in dental size between the Mesolithic and Agriculturalist samples, followed by a continued although diminished trend of reduction for only the molar teeth between the two Agriculturalist groups. These patterns are best observed by examining tooth breadths, which are considered as the most reliable indicator of tooth size. Previously published odontometrics of the Nubian Mesolithic are briefly compared to the findings of this diachronic analysis of Nubian dental change.     

Reconstructing the History of Mesoamerican Populations through the Study of the Mitochondrial DNA Control Region

The study of genetic information can reveal a reconstruction of human population’s history. We sequenced the entire mtDNA control region (positions 16.024 to 576 following Cambridge Reference Sequence, CRS) of 605 individuals from seven Mesoamerican indigenous groups and one Aridoamerican from the Greater Southwest previously defined, all of them in present Mexico. Samples were collected directly from the indigenous populations, the application of an individual survey made it possible to remove related or with other origins samples. Diversity indices and demographic estimates were calculated. Also AMOVAs were calculated according to different criteria. An MDS plot, based on FST distances, was also built. We carried out the construction of individual networks for the four Amerindian haplogroups detected. Finally, barrier software was applied to detect genetic boundaries among populations. The results suggest: a common origin of the indigenous groups; a small degree of European admixture; and inter-ethnic gene flow. The process of Mesoamerica’s human settlement took place quickly influenced by the region’s orography, which development of genetic and cultural differences facilitated. We find the existence of genetic structure is related to the region’s geography, rather than to cultural parameters, such as language. The human population gradually became fragmented, though they remained relatively isolated, and differentiated due to small population sizes and different survival strategies. Genetic differences were detected between Aridoamerica and Mesoamerica, which can be subdivided into “East”, “Center”, “West” and “Southeast”. The fragmentation process occurred mainly during the Mesoamerican Pre-Classic period, with the Otomí being one of the oldest groups. With an increased number of populations studied adding previously published data, there is no change in the conclusions, although significant genetic heterogeneity can be detected in Pima and Huichol groups. This result may be explained because populations historically assigned as belonging to the same group were, in fact, different indigenous populations.     

The influence of artificial cranial vault deformation on the expression of cranial nonmetric traits: its importance in the study of evolutionary relationships

Nonmetric cranial traits have been commonly used in evolutionary relationship studies. They develop during the growth and development of an individual, and for this reason its expression presents different sources of genetic and nongenetic variation. However, the use of these features in evolutionary relationship studies carries the implicit assumption that much of the nonmetric trait variation is essentially genetic. Among the nonheritable factors, cranial vault deformation has been the most studied in human populations. Because of the widespread distribution and elevated rate of artificial cranial vault deformation found in America, and the importance of nonmetric traits in evolutionary relationship studies in this area, the objectives of this paper are as follows: (a) to study the influence of artificial cranial vault deformation on the presence of nonmetric traits within samples of human craniofacial remains; and (b) to establish artificial cranial vault deformation influence on evolutionary relationships between local populations on a regional scale. Our results indicate that artificial cranial vault deformations alter the variation and covariation of metric and nonmetric traits in some samples. Wormian bones, placed in cranial vault sutures, are the most influenced by this factor. However, our results suggest that when all nonmetric traits were used the artificial cranial vault deformation did not influence the basic pattern of variation among samples. The exclusion or inclusion of wormians bones in evolutionary relationships analysis did not modify the results, but using only wormians bones lead to inconsistent results indicating that these traits have little value on these kind of studies.     

Craniometric data support a mosaic model of demic and cultural Neolithic diffusion to outlying regions of Europe

The extent to which the transition to agriculture in Europe was the result of biological (demic) diffusion from the Near East or the adoption of farming practices by indigenous hunter-gatherers is subject to continuing debate. Thus far, archaeological study and the analysis of modern and ancient European DNA have yielded inconclusive results regarding these hypotheses. Here we test these ideas using an extensive craniometric dataset representing 30 hunter-gatherer and farming populations. Pairwise population craniometric distance was compared with temporally controlled geographical models representing evolutionary hypotheses of biological and cultural transmission. The results show that, following the physical dispersal of Near Eastern/Anatolian farmers into central Europe, two biological lineages were established with limited gene flow between them. Farming communities spread across Europe, while hunter-gatherer communities located in outlying geographical regions adopted some cultural elements from the farmers. Therefore, the transition to farming in Europe did not involve the complete replacement of indigenous hunter-gatherer populations despite significant gene flow from the Southwest Asia. This study suggests that a mosaic process of dispersal of farmers and their ideas was operating in outlying regions of Europe, thereby reconciling previously conflicting results obtained from genetic and archaeological studies.     

Dietary,Cultural, and Pathogens-Related Selective Pressures Shaped Differential Adaptive Evolution among Native Mexican Populations

Native American genetic ancestry has been remarkably implicated with increased risk of diverse health issues in several Mexican populations, especially in relation to the dramatic changes in environmental, dietary, and cultural settings they have recently undergone. In particular, the effects of these ecological transitions and Westernization of lifestyles have been investigated so far predominantly on Mestizo individuals. Nevertheless, indigenous groups, rather than admixed Mexicans, have plausibly retained the highest proportions of genetic components shaped by natural selection in response to the ancient milieu experienced by Mexican ancestors during their pre-Columbian evolutionary history. These formerly adaptive variants have the potential to represent the genetic determinants of some biological traits that are peculiar to Mexican people, as well as a reservoir of loci with possible biomedical relevance. To test such a hypothesis, we used genome-wide genotype data to infer the unique adaptive evolution of Native Mexican groups selected as reasonable descendants of the main pre-Columbian Mexican civilizations. A combination of haplotype-based and gene-network analyses enabled us to detect genomic signatures ascribable to polygenic adaptive traits plausibly evolved by the main genetic clusters of Mexican indigenous populations to cope with local environmental and/or cultural conditions. Some of these adaptations were found to play a role in modulating the susceptibility/resistance of these groups to certain pathological conditions, thus providing new evidence that diverse selective pressures have contributed to shape the current biological and disease-risk patterns of present-day Native and Mestizo Mexican populations.     

People of India: Biological diversity and affinities

The Indian subcontinent comprises a vast collection of peoples with different morphological, genetic, cultural, and linguistic characteristics. While much of this variability is indigenous, a considerable fraction of it has been introduced through large-scale immigrations into India in historical times. From an evolutionary standpoint, it is of immense interest to quantify biological diversity in contemporary human populations, to study biological affinities and to relate observed patterns of affinities with cultural, linguistic and demographic histories of populations. Such efforts are intended to shed light on the peopling of India. The purpose of this paper is to present a broad overview of the physical (anthropometric) and genetic diversities and affinities of the peoples of India. I shall also attempt to examine how well biological, particularly genetic, diversities and affinities correlate with geographical, socio-cultural, and linguistic diversities and affinities. © 1998 Wiley-Liss, Inc.     

Altitudinal variation in the morphometric characteristics of Aedes vexans Meigen from northeastern Turkey

Body size is one of the most significant features of organisms and is correlated with a large number of ecological and physiological variables. Similar to size, biological shape is one of the most conspicuous aspects of an organism's phenotype and provides a link between the genotype and the environment. Body size may change with altitude and also habitat differences associated with altitude may affect the biological shape and some morphological characteristics. Four populations of Aedes vexans Meigen occurring in different ecological subregions at altitudes between 808–1,620 m in the Aras Valley from northeastern Turkey were compared using traditional and geometric morphometrics. When the wing shape differences of populations were analyzed by UPGM, the cluster analyses recognized two main groups of populations. Gödekli (808 m) comprised the first group while Zülfikar (848 m), Sürmeli (944 m), and Cilehane (1,620 m) populations comprised the second group. In the second group, Zülfikar and Cilehane populations showed a similar grouping pattern while Sürmeli appeared as a different group. Centroid sizes were used as measures of overall wing size differences among different regions. Aedes vexans from the Sürmeli region had relatively larger wings.     

Y-chromosome variation in Altaian Kazakhs reveals a common paternal gene pool for Kazakhs and the influence of Mongolian expansions

Kazakh populations have traditionally lived as nomadic pastoralists that seasonally migrate across the steppe and surrounding mountain ranges in Kazakhstan and southern Siberia. To clarify their population history from a paternal perspective, we analyzed the non-recombining portion of the Y-chromosome from Kazakh populations living in southern Altai Republic, Russia, using a high-resolution analysis of 60 biallelic markers and 17 STRs. We noted distinct differences in the patterns of genetic variation between maternal and paternal genetic systems in the Altaian Kazakhs. While they possess a variety of East and West Eurasian mtDNA haplogroups, only three East Eurasian paternal haplogroups appear at significant frequencies (C3*, C3c and O3a3c*). In addition, the Y-STR data revealed low genetic diversity within these lineages. Analysis of the combined biallelic and STR data also demonstrated genetic differences among Kazakh populations from across Central Asia. The observed differences between Altaian Kazakhs and indigenous Kazakhs were not the result of admixture between Altaian Kazakhs and indigenous Altaians. Overall, the shared paternal ancestry of Kazakhs differentiates them from other Central Asian populations. In addition, all of them showed evidence of genetic influence by the 13(th) century CE Mongol Empire. Ultimately, the social and cultural traditions of the Kazakhs shaped their current pattern of genetic variation.     

Patterns of trait divergence between populations of the meadow grasshopper, Chorthippus parallelus

Abstract.— To understand the process of speciation, we need to identify the evolutionary phenomena associated with divergence between populations of the same species. A powerful approach is to compare patterns of trait differences between populations differing in their evolutionary histories. A recent study of genetic divergence between populations of the meadow grasshopper Chorthippus parallelus , from different locations around Europe has allowed us to use this species to investigate which aspects of evolutionary history are associated with divergence in morphology and mating signals. During the last glaciation C. parallelus was confined to a number of refugia in southern Europe and has subsequently recolonized the northern part of the continent. This process of isolation followed by range expansion has created populations differing markedly in their evolutionary pasts–some have been isolated from one another for thousands of years, others have undergone repeated founder events, and others now live in sympatry with a closely related species. Using laboratory-reared grasshoppers from 12 different populations with a range of evolutionary histories, we quantify differences in morphology, chemical signals, and male calling-song. The observed pattern of divergence between these populations is then compared with the pattern predicted by hypotheses about what drives divergence. This comparison reveals that long periods in allopatry and processes associated with repeated founder events are both strongly associated with divergence.     

Palatability to a generalist herbivore,defence and growth of invasive and native <Emphasis Type="Italic">Senecio</Emphasis> species: testing the evolution of increased competitive ability hypothesis

This paper tests the prediction that introduced plants may become successful invaders because they experience evolutionary changes in growth and defence in their new range [evolution of increased competitive ability hypothesis (EICA)]. Interspecific and intraspecific binary feeding choices were offered to the snail Helix aspersa. The choices were between: (1) plants of the invasive Senecio inaequidens and Senecio pterophorus derived from populations in the introduced range (Europe) and plants of three indigenous species (Senecio jacobea, Senecio vulgaris and Senecio malacitanus) from populations in Europe; (2) plants of the invasive S. inaequidens and S. pterophorus from populations in the introduced range (Europe) and from populations in the native range (South Africa). We did not find a clear pattern of preference for indigenous or alien species of Senecio. However, we found that European invasive populations of S. inaequidens and S. pterophorus were less palatable than South African native populations. Moreover, in contrast to the predictions of the EICA hypothesis, the invasive genotypes of both species also showed a higher total concentration of pyrrolizidine alkaloids, and in the case of S. inaequidens we also found higher growth than in native genotypes. Our results are discussed with respect to the refinement of the EICA hypothesis that takes into account the difference between specialist and generalist herbivores and between qualitative and quantitative defences. We conclude that invasive populations of S. inaequidens and S. pterophorus are less palatable than native populations, suggesting that genetic differentiation associated with founding may occur and contribute to the plants’ invasion success by selecting the best-defended genotypes in the introduced range.     

Morphometric variation in a hybrid zone of two subspecies of Gerris costae (Heteroptera: Gerridae) in the Maritime Alps

Two morphologically distinct subspecies of Gerris costae form a contact zone extending from the Maritime to the Western Alps. Within this area canonical trend surface analysis revealed a geographic pattern of morphometric variation consistent with topography. From North to South, and from high to low elevation there was a transition from G. c. costae-like phenotypes to phenotypes resembling pure G. c. fieberi. The same pattern was confirmed with canonical variate analysis not taking geographic location into account; it is therefore not an artifact of trend surface analysis. Comparisons of the pattern of morphometric variation of laboratory-reared offspring with the pattern of their parents sampled from natural populations show that geographic variation is mostly determined genetically. Intermediate individuals from field populations probably are natural hybrids between the two subspecies, because laboratory-reared hybrids were intermediate between the offspring of pure strains. We did not find increased morphometric variation within the contact zone. This suggests unimpeded introgression and is in contrast with an increase in size variability that is predicted to be associated with a transition between uni- and bivoltine forms.     

The invasive stink bug Halyomorpha halys affects the reproductive success and the experience-mediated behavioural responses of the egg parasitoid Trissolcus basalis

Invasive species, because of their lack of co-evolutionary history with recipient communities, can act as “evolutionary traps” causing disconnects between natural enemy behavioural responses and the suitability of the invasive species as a prey/host resource. Invasion of exotic species in non-native environments may have several ecological effects, including consequences for the experience-mediated behavioural responses of indigenous foragers. Experience is usually thought to help resident species to buffer against negative impacts of new invasive species, including escaping from evolutionary traps. Here we hypothesized that the impact of foraging experience depends on whether an indigenous egg parasitoid can correctly assess the resource suitability of a new invasive species for offspring development. We showed that the invasive stink bug Halyomorpha halys acts as an evolutionary trap for the indigenous egg parasitoid Trissolcus basalis leading to unsuccessful development of?~?95% of the eggs laid in this host species. In a mixed scenario in which the associated resident stink bug Nezara viridula co-occurs with the invasive H. halys, we showed that oviposition experience in the low quality invasive host induces in T. basalis similar responses to those of the associated host. These results suggest that foraging experience does not lead to avoidance of an evolutionary trap. We discuss parasitoid foraging experience and reproductive success in the light of the evolutionary trap framework with implication for biological control.

     

Phenotypic plasticity and selection in Drosophila life history evolution. 2. Diet,mates and the cost of reproduction

While it is commonplace for biologists to use the response to environmental manipulation as a guide to evolutionary responses to selection, the relationship between phenotypic plasticity and genetic change is not generally well-established. The life-histories of laboratory Drosophila populations are among the few experimental systems which simultaneously afford information on phenotypic plasticity and evolutionary trajectories. We employed a combination of two replicated selectively differentiated stocks (postponed aging stocks and their controls; 10 populations in total) and two different environmental manipulations (nutrition and mating) to explore the empirical relationship between phenotypic plasticity and evolutionary trajectories. While there are a number of parallels between the results obtained using these two approaches, there are important differences. In particular, as the detail of the biological characterization of either type of response increases, so their disparities multiply. Nonetheless, the combination of environmental manipulation with evolutionary divergence provides valuable information about the biological connections between life-history, caloric reserves, and reproductive physiology in Drososphila.     

Geographic structure in the searching behaviour of a specialist parasitoid: combining molecular and behavioural approaches

An increasing number of studies have shown that the traits important to species interactions may differ geographically among populations or groups of populations within a single interacting species. We examined geographic structure in the searching behaviour of a recently discovered parasitoid in the genus Agathis (Hymenoptera: Braconidae) by examining the pattern of population structure obtained from sequence data of mitochondrial DNA cytochrome oxidase I and the pattern of population differentiation in female searching behaviour. Analyses of population structure showed no isolation by distance and suggested long distance dispersal among populations. This pattern is consistent with recent post‐glacial expansion of Agathis n. sp. Observations of searching behaviour demonstrated that populations of Agathis n. sp. differed in a subset of the behavioural traits examined and also one morphological trait. These population differences appear to be driven in part by local host plant characteristics, and based on the population structure of Agathis n. sp., have arisen relatively quickly in evolutionary time. This study suggests that the interaction between parasitoids and their host insects may exhibit substantial geographic variation, and studies that focus at the level of single populations or the species‐level may be missing much of the evolutionary dynamics of parasitoid–host interactions.     

芦鹀种群中的文化、遗传和形态进化的同时比较

我们比较了芦 (Emberizaschoeniclus)两个亚种组 ,即北部的薄喙亚种组和南部的厚喙亚种组的 10个种群中的文化、遗传和形态变异。使用了四个不同的变异标记物 ,其中两个用来测量文化分化 ,一个用来测量遗传分化 ,即微卫星等位基因的频次 ,一个用来测量种群的形态分化 ,即喙的高度。将遗传分化作为进化时间的尺度 ,我们计算了亚种组间和组内分化指标与所估计的进化率之间的相关性 ,发现只有文化定量指标和遗传分化与种群的形态分化相关 ,而两个文化分化指标之间没有关系 ,文化分化与遗传分化之间也没有关系。使用文化 -定量分化指标 ,发现亚种组间的文化进化率高于亚种内的文化进化率 ,提示鸣唱在防止杂交方面只有微弱的、也许是次要的作用。鸣唱定量特征的变异与微卫星频次相同 ,实际上在自然界中更可能是遗传决定的 ,这可以解释由于分析两个文化变异指标所得出的结果的不一致性。鸣唱的声学特性可能由于栖息地的差异或形态上的限制而发生了演变 ,而文化传播单位 (Meme)的特性可能由于学习鸣唱和文化传播而受到了影响     

Bat Species Comparisons Based on External Morphology: A Test of Traditional versus Geometric Morphometric Approaches

External morphology is commonly used to identify bats as well as to investigate flight and foraging behavior, typically relying on simple length and area measures or ratios. However, geometric morphometrics is increasingly used in the biological sciences to analyse variation in shape and discriminate among species and populations. Here we compare the ability of traditional versus geometric morphometric methods in discriminating between closely related bat species – in this case European horseshoe bats (Rhinolophidae, Chiroptera) – based on morphology of the wing, body and tail. In addition to comparing morphometric methods, we used geometric morphometrics to detect interspecies differences as shape changes. Geometric morphometrics yielded improved species discrimination relative to traditional methods. The predicted shape for the variation along the between group principal components revealed that the largest differences between species lay in the extent to which the wing reaches in the direction of the head. This strong trend in interspecific shape variation is associated with size, which we interpret as an evolutionary allometry pattern.     

Genome‐wide analysis reveals artificial selection on coat colour and reproductive traits in Chinese domestic pigs

Pigs from Asia and Europe were independently domesticated from c. 9000 years ago. During this period, strong artificial selection has led to dramatic phenotypic changes in domestic pigs. However, the genetic basis underlying these morphological and behavioural adaptations is relatively unknown, particularly for indigenous Chinese pigs. Here, we performed a genome‐wide analysis to screen 196 regions with selective sweep signals in Tongcheng pigs, which are a typical indigenous Chinese breed. Genes located in these regions have been found to be involved in lipid metabolism, melanocyte differentiation, neural development and other biological processes, which coincide with the evolutionary phenotypic changes in this breed. A synonymous substitution, c.669T>C, in ESR1, which colocalizes with a major quantitative trait locus for litter size, shows extreme differences in allele frequency between Tongcheng pigs and wild boars. Notably, the variant C allele in this locus exhibits high allele frequency in most Chinese populations, suggesting a consequence of positive selection. Five genes (PRM1, PRM2, TNP2, GPR149 and JMJD1C) related to reproductive traits were found to have high haplotype similarity in Chinese breeds. Two selected genes, MITF and EDNRB, are implied to shape the two‐end black colour trait in Tongcheng pig. Subsequent SNP microarray studies of five Chinese white‐spotted breeds displayed a concordant signature at both loci, suggesting that these two genes are responsible for colour variations in Chinese breeds. Utilizing massively parallel sequencing, we characterized the candidate sites that adapt to artificial and environmental selections during the Chinese pig domestication. This study provides fundamental proof for further research on the evolutionary adaptation of Chinese pigs.