1,284 research outputs found
Who are you? The genetic identity of some insular populations of Hierophis viridiflavus s.l. from the Tyrrhenian Sea
Full text linkThis work investigates the genetic identity of Hierophis viridiflavus s.l. specimens from insular populations, to determine which of the two previously identified species is present on each island. Here, the authors hypothesise about times and modes of colonization and discuss the faunistic value of the obtained results. This follows the recent proposal to consider the two clades as two different species. Specimens from the islands of Favignana, Lipari and Vulcano belong to H. carbonarius and probably all belong to putative Sicilian source populations. Conversely, all individuals from the Pontine Islands (Ponza, Palmarola, Ventotene) should be considered to belong to H. viridiflavus. Even if genetically identical to the specimens from the Tyrrhenian Italian coast, these individuals show a darker colouration, very similar to the one usually shown by H. carbonarius specimens. Considering that the Pontine H. viridiflavus populations probably have a very recent origin, the dark livery of these individuals could be the result of a rapid morphological adaptation to insular environments
Morphometric and genetic divergence in island and mainland populations of Anolis nebulosus (Squamata: Polychrotidae) from Jalisco (Mexico): an instance of insular gigantism
No full textThe clouded anole Anolis nebulosus (Squamata: Polychrotidae) is widespread on the Pacific coast of Mexico. The species also inhabits Don Panchito, a small islet located near the coast of the Chamela-Cuixmala Biosphere Reserve in the state of Jalisco. We studied the extent of intraspecific differences in morphology (absolute size and body proportions) and in mtDNA sequences (16S and NDH2) between the population living on the islet (N = 18 for morphometry; N = 12 for mtDNA) and the one on the facing mainland (N = 38 for morphometry; N = 16 for mtDNA). The individuals on the islet are larger than those on the mainland with little overlap in size for either males (islet: 52.79 +/- 1.82 mm; mainland: 40.96 +/- 2.99 mm) or females (islet: 46.18 +/- 3.24 mm; mainland 37.14 +/- 2.13 mm). The presence of insular gigantism, as here found in A. nebulosus, seems uncommon in the genus and could be explained as a combination of low predation pressure and higher intraspecific competition on the island. Moreover, we found that sexual dimorphism (SD) is higher in the island population than in the mainland one. The molecular analysis shows the absence of shared haplotypes between the island and mainland populations. Ten mtDNA haplotypes belonged to the mainland population and three to the island population. The shape of the minimum spanning network and of the mismatch distribution indicates a single colonization event. These molecular data indicate a certain degree of isolation of the island population notwithstanding its proximity to the coast. The morphological characteristics of the anoles on Don Panchito match with the expectation of the so-called " reversed island syndrome" theory, which predicts an increased body size and sexual dimorphism in lizards living on very small islands characterized by unpredictable environmental conditions
Comparative genetic research on Microtus mystacinus (de Filippi, 1865) distributed in Asia and Europe inferred from mitochondrial (CYTB and COXI) and nuclear (IRBP) gene regions
No full textThe East European vole Microtus mystacinus is the most widespread vole species in Anatolia. It is
also frequently seen in watery habitats in a large area of Eurasia. In this paper, an attempt was made
to ascertain the level of genetic differentiation between Anatolian (Asian part of Turkey) and Turkish
Thracian (European part of Turkey) populations together with additional data from other parts of Asia
and Europe by analysing two mitochondrial (cytochrome-b and cytochrome oxidase subunit I) and
one nuclear (interphotoreceptor retinoid binding protein) gene regions. Acquired Bayesian Inference
trees mostly separated the Asian and European populations of M. mystacinus and the fixation index
values implied a significant differentiation between these populations for mitochondrial DNA. On the
other hand, the median-joining networks did not show diverging populations, significantly, and the
mean genetic distance values among populations were found to be low for both mitochondrial and
nuclear DNA. Evolutionary divergence times of Asian and European populations were also calculated
and dated back to approximately 0.316–0.111 million years ago, coinciding with the ice ages of the
Pleistocene epoch. According to the obtained results, M. mystacinus populations have not diverged
enough to form different species; however, there is a separation between Asian and European populations
which might result in speciation
Insights into Genetic Diversity, Runs of Homozygosity and Heterozygosity-Rich Regions in Maremmana Semi-Feral Cattle Using Pedigree and Genomic Data
Full text linkSemi-feral local livestock populations, like Maremmana cattle, are the object of renewed interest for the conservation of biological diversity and the preservation and exploitation of unique and potentially relevant genetic material. The aim of this study was to estimate genetic diversity parameters in semi-feral Maremmana cattle using both pedigree- and genomic-based approaches (FIS and FROH), and to detect regions of homozygosity (ROH) and heterozygosity (ROHet) in the genome. The average heterozygosity estimates were in the range reported for other cattle breeds (HE=0.261, HO=0.274). Pedigree-based average inbreeding (F) was estimated at 4.9%. The correlation was low between F and genomic-based approaches (r=0.03 with FIS, r=0.21 with FROH), while it was higher between FIS and FROH (r=0.78). The low correlation between F and FROH coefficients may be the result of the limited pedigree depth available for the animals involved in this study. The ROH islands identified in Maremmana cattle included candidate genes associated with climate adaptation, carcass traits or the regulation of body weight, fat and energy metabolism. The ROHet islands contained candidate genes associated with nematode resistance and reproduction traits in livestock. The results of this study confirm that genome-based measures like FROH may be useful estimators of individual autozygosity, and may provide insights on pedigree-based inbreeding estimates in cases when animals’ pedigree data are unavailable, thus providing a more detailed picture of the genetic diversity
About twin primes and distribution of primes
Full text linkThis paper give us a demonstration of twin primes conjecture using approximation of function �(iupsilon) that we introduce in section 6. Section 1-5 give us introduction to terminology and a clarification on (iupsilon) terms. In particular section
5 is really important because of its Lemma. Section 7 reassume foregoing explanations and it give us two theorems and one corollary;the theorem 7.2 give us exact approximation of twin primes counting function
Italian local chicken breeds: a comparative analysis of biodiversity on a global scale
Full text linkBackground: Chickens, domesticated around 3500 years ago, are crucial in global agriculture, resulting in hundreds of breeds worldwide. In Europe, intensive breeding has led to the creation of numerous distinct commercial lines at the expense of local breeds. As a result, local breeds, which are not subject to rigorous selective practices, face higher risks of genetic problems due to a narrower genetic base. Modern genotyping and bioinformatic approaches allow detailed genetic analysis. This study offers a comprehensive genetic overview of Italian chicken biodiversity compared to global breeds, emphasizing the importance of preserving local genetic diversity. Results: Hundred and ninety-two chicken breeds from various countries were analyzed, with Italian breeds being highly represented. Genetic relationships showed that Italian breeds clustered with some European, African, and Asian breeds. The ADMIXTURE analysis identified 25 distinct populations and highlighted genetic similarities of certain Italian breeds with German, French, and Swiss ones. Genetic diversity was high in African and some Asian and European breeds, with Italian breeds exhibiting moderate diversity and variability. The TreeMix analysis revealed significant migration events and evolutionary clustering. The Italian breeds had close genetic ties and some highlighted evidence of genetic introgression from common ancestors. Conclusions: Italian chicken breeds have significant genetic relationships with European, Asian, and African breeds, reflecting historical trade and breeding exchanges. Southern Italian breeds form a distinct genetic group, highlighting regional uniqueness. Overall, the research points out the need for conservation strategies to preserve genetic diversity and account for historical and contemporary gene flows, ensuring the sustainability of Italian chicken biodiversity in the face of environmental and agricultural challenges
The Intriguing Biogeographic Pattern of the Italian Wall Lizard Podarcis siculus (Squamata: Lacertidae) in the Tuscan Archipelago Reveals the Existence of a New Ancient Insular Clade
Full text linkThe Tuscan Archipelago is one of the most ancient and ecologically heterogeneous island systems in the Mediterranean. The biodiversity of these islands was strongly shaped by the Pliocene and Pleistocene sea regressions and transgression, resulting in different waves of colonization and isolation of species coming from the mainland. The Italian wall lizard, Podarcis siculus, is present on the following islands of the Tuscan Archipelago: Elba, Giglio, Giannutri, Capraia, Montecristo and Cerboli. The species in the area displays a relatively high morphological variability that in the past led to the description of several subspecies. In this study, both the genetic and morphological diversity of P. siculus of the Tuscan Archipelago were investigated. Specifically, the meristic characters and the dorsal pattern were analyzed, while the genetic relationships among these populations were explored with mtDNA and microsatellite nuclear markers to reconstruct the colonization history of the Archipelago. Our results converge in the identification of at least two different waves of colonization in the Archipelago: Elba, and the populations of Cerboli and Montecristo probably originate from historical introductions from mainland Tuscany, while those of Giglio and Capraia are surviving populations of an ancient lineage which colonized the Tuscan Archipelago during the Pliocene and which shares a common ancestry with the P. siculus populations of south-eastern Italy. Giannutri perhaps represents an interesting case of hybridization between the populations from mainland Tuscany and the Giglio-Capraia clade. Based on the high phenotypic and molecular distinctiveness of this ancient clade, these populations should be treated as distinct units deserving conservation and management efforts as well as further investigation to assess their taxonomic status
A combination of long term fragmentation and glacial persistence drove the evolutionary history of the Italian wall lizard Podarcis siculus
Full text linkAbstract
Background
The current distribution of genetic diversity is the result of a vast array of microevolutionary processes, including short-term demographic and ecological mechanisms and long-term allopatric isolation in response to Quaternary climatic fluctuations. We investigated past processes that drove the population differentiation and spatial genetic distribution of the Italian wall lizard Podarcis siculus by means of sequences of mitochondrial cytb ( n \u2009=\u2009277 from 115 localities) and nuclear mc1r and \u3b2-fibint7 genes ( n \u2009=\u2009262 and n \u2009=\u200991, respectively) from all its distribution range. The pattern emerging from the genetic data was compared with current and past (last glacial maximum) species distribution modeling (SDM).
Results
We identified seven deeply divergent parapatric clades which presumably remained isolated in different refugia scattered mainly throughout the Tyrrhenian coast. Conversely, the Adriatic coast showed only two haplogroups with low genetic variability. These results appear to agree with the SDM prediction at the last glacial maximum (LGM) indicating a narrow area of habitat suitability along the Tyrrhenian coast and much lower suitability along the Adriatic one. However, the considerable land exposure of the Adriatic coastline favored a glacial colonization of the Balkan Peninsula.
Conclusions
Our population-level historical demography showed a common trend consistent with glacial expansions and regional persistence during the last glacial maximum. This complex genetic signature appears to be inconsistent with the expectation of the expansion-contraction model and post-LGM (re)colonizations from southern refugia. Hence it is one of an increasing number of cases in which these assumptions are not met, indicating that long-term fragmentation and pre-LGM events such as glacial persistence were more prominent in shaping genetic variation in this temperate species
A study in scarlet: incipient speciation, phenotypic differentiation and conservation implications of the Podarcis lizards of the western Pontine islands, Italy
No full textDuring the first decades of the last Century an enigmatic extinction was documented to have occurred on the small Mediterranean island of Santo Stefano and Sherlock Holmes was jokingly evoked to solve the mystery. Although islands are fascinating systems where to study microevolutionary processes, they may, on the other hand, host unstable communities that make their populations particularly vulnerable to anthropogenic effects and even to extinctions. Here, we investigated the variation of head morphology of 374 individuals of Podarcis siculus from mainland Italy, Sicily and the Pontine Archipelago, using the geometric morphometric approach. We also included in the analysis samples of the extinct population of Santo Stefano Island aiming to contribute to shed light on the “mystery” and to provide additional information on the historical biogeography of the Archipelago. We found strong relation between the morphological differences and the phylogeographic structure basing on previously published genetic data, indicating that the western Pontine populations seem to be a case of incipient speciation. In addition, the extinct population of Santo Stefano Island clustered in all analyses with the western Pontine populations. This result not only involves the evolutionary history of P. siculus, but also entails broader taxonomic considerations and conservation aspects
Evaluating the island effect on phenotypic evolution in the Italian wall lizard, Podarcis siculus (Reptilia: Lacertidae)
No full textIslands are compelling natural laboratories for studying evolutionary processes. Nevertheless, the existence of general rules underlying morphological evolution on islands remains an unresolved issue. In this study, we investigated the insular phenotypic variability of the Italian wall lizard (Podarcis siculus) on a large geographical scale, in order to assess the putative existence of an island effect on three morphological head traits: shape, size and degree of sexual dimorphism. A geometric morphometric analysis was performed on 30 island and 24 mainland populations, involving a total of 992 specimens, and we analysed differences in both mean trait values and variances (disparity). We found increased shape disparity in insular lizards with respect to mainland ones. On the other hand, both size disparity and mean head dimensions of males decreased on islands, leading to a reduction in sexual dimorphism. Our results provide evidence for a multidirectional morphological diversification on islands concerning head shape of both sexes, while directional and canalizing selection likely occurred for head size, but only in males. Our findings improve our knowledge on the effect of insularity in Podarcis siculus, and highlight the need for an exstensive sampling scheme and a multi-trait methodological approach
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