نتایج جستجو برای: geographic isolation
تعداد نتایج: 200986 فیلتر نتایج به سال:
Aim: To consider how geographic variation in species recognition over time affects the speciation process. Organisms: The gynogenetic livebearing fish Poecilia formosa (Amazon molly) is the hybrid offspring of two bisexual parent species, P. latipinna (sailfin molly) and P. mexicana (Atlantic molly). The Amazon molly is an all-female species that must mate with males of their parent species. Bu...
Examining how historical and contemporary geographic and environmental factors contribute to genetic divergence at different evolutionary scales is a central yet largely unexplored question in ecology and evolution. Here, we examine this key question by investigating how environmental and geographic factors across different epochs have driven genetic divergence at deeper (phylogeographic) and s...
In many species, spatial genetic variation displays patterns of "isolation-by-distance." Characterized by locally correlated allele frequencies, these patterns are known to create periodic shapes in geographic maps of principal components which confound signatures of specific migration events and influence interpretations of principal component analyses (PCA). In this study, we introduced model...
The dog was the first domesticated animal but it remains uncertain when the domestication process began and whether it occurred just once or multiple times across the Northern Hemisphere. To ascertain the value of modern genetic data to elucidate the origins of dog domestication, we analyzed 49,024 autosomal SNPs in 1,375 dogs (representing 35 breeds) and 19 wolves. After combining our data wit...
The island inhabitants of Sardinia have long been a focus for studies of complex human traits due to their unique ancestral background and population isolation reflecting geographic and cultural restriction. Population isolates share decreased genomic diversity, increased linkage disequilibrium, and increased inbreeding coefficients. In many regions, dogs and humans have been exposed to the sam...
Drosophila paulistorum Dobzhansky and Pavan is a superspecies which consists of at least five races or incipient species, living in tropical Central and South America (DOBZHANSKY and SPASSKY 1959; DOBZHANSKY, EHRMAN, PAVLOVSKY and SPASSKY 1964). An ethological (sexual) isolation and a sterility of hybrid males impede the gene exchange between the incipient species. Although the ethological isol...
BACKGROUND AND AIMS Among-population differentiation in phenotypic traits and allelic variation is expected as a consequence of isolation, drift, founder effects and local selection. Therefore, investigating molecular and quantitative genetic divergence is a pre-requisite for studies of local adaptation in response to selection under variable environmental conditions. METHODS Among- and withi...
Sympatric speciation remains controversial. 'Sympatry' originally meant "in the same geographical area". Recently, evolutionists have redefined 'sympatric speciation' non-spatially to require panmixia (m = 0.5) between a pair of demes before onset of reproductive isolation. Although panmixia is a suitable starting point in models of speciation, it is not a useful definition of sympatry in natur...
Understanding how natural processes affect population genetic structures is an important issue in evolutionary biology. One effective method is to assess the relative importance of environmental and geographical factors in the genetic structure of populations. In this study, we examined the spatial genetic variation of thirteen Myriophyllum spicatum populations from the Qinghai-Tibetan Plateau ...
The Donaciinae consist of approximately 165 species predominantly occurring in the northern hemisphere. We analysed mitochondrial and nuclear DNA (COI, EF-1alpha) of 46 species to investigate their phylogeny and to discuss general topics in the context of insect herbivory (generalists versus specialists, ecological speciation). Phylogenetic reconstructions from various methodical approaches yie...
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