Centres of origin: do they exist, can we identify them, does it matter? (original) (raw)
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A mathematical model of geographical speciation starting from a centre of origin
In this paper we proposed to prove the compatibility between geographic speciation and the concept of "center of origin" or “center of dispersion”. For this, we mathematically modeled, process of geographic speciation with center of origin, i.e. the following scenario that iterates several times: in the relatively small area of one mother species (area called "center of origin") appear some natural barriers that produce evolution divergent and the new areas expands exclusively centrifugal. Then, the disappearance of barriers enables centripetal expanding of areas of the new species (these areas can overlap). Simulating several times, on the computer, the process of speciation, it was found that the agglomeration of the current species in "center of origin" occurs most often, but not necessarily. The study provides a counter argument of the Vicariance Biology school, which believes that mother species was widespread in the area of gender. See http://www....
Society of Systematic Biologists Centers of Origin and Related Concepts Author ( s )
2010
Croizat, L., G. Nelson, and D. E. Rosen (Department of Ichthyology, The American Museum of Natural History, New York, New York 10024) 1974. Centers of origin and related concepts. Syst. Zool. 23:265-287.-The concept of center of origin in the Darwinian sense is often accepted and used as if it were a conceptual model necessary and fundamental to historical zoogeographical analysis. But in certain respects it is inconsistent with the principles of common ancestry and vicariance2 (e.g., allopatric speciation), and its application to concrete examples of animal distribution generally yields ambiguous results. In the following pages we present a critique of the concept of center of origin, and outline an alternative conceptual model, involving generalized patterns of biotic distribution (generalized tracks). We assume that a given generalized track estimates an ancestral biota that, because of changing geography, has become subdivided into descendant biotas in localized areas. We assume...
Ecology and evolution, 2018
Identifying the factors that influence spatial genetic structure among populations can provide insights into the evolution of invasive plants. In this study, we used the common reed (), a grass native in Europe and invading North America, to examine the relative importance of geographic, environmental (represented by climate here), and human effects on population genetic structure and its changes during invasion. We collected samples offrom both the invaded North American and native European ranges and used molecular markers to investigate the population genetic structure within and between ranges. We used path analysis to identify the contributions of each of the three factors-geographic, environmental, and human-related-to the formation of spatial genetic patterns. Genetic differentiation was observed between the introduced and native populations, and their genetic structure in the native and introduced ranges was different. There were strong effects of geography and environment o...
Molecular Ecology, 2013
The abundant centre hypothesis (ACH) assumes that population abundance, population size, density and per-capita reproductive output should peak at the centre of a species' geographic range and decline towards the periphery. Increased isolation among and decreased reproductive output within edge populations should reduce within-population genetic diversity and increase genetic differentiation among edge relative to central populations. The ACH also predicts asymmetrical gene flow, with net movement of migrants from the centre to edges. We evaluated these ecological assumptions and population-genetic predictions in the endemic flowering plant Leavenworthia stylosa. Although populations were more spatially isolated near range edges, the geographic centre was surrounded by and not coincident with areas of peak population abundance, and plant density increased towards range edges. Per-capita seed number was not associated with distance to the range centre, but seed number/m 2 increased near range edges. In support of ACH predictions, allelic diversity at 12 microsatellite loci declined with distance from the range centre, and pairwise F ST values were higher between edge populations than between central populations. Coalescent analyses confirmed that gene flow was most infrequent between edge populations, but there was not an asymmetric pattern of gene flow predicted by the ACH. This study shows that among-population demographic variability largely did not support the ACH, while patterns of genetic diversity, differentiation and gene flow were generally consistent with its predictions. Such mixed support has frequently been observed in tests of the ACH and raises concerns regarding the generality of this hypothesis for species range limits.
PeerJ, 2021
BackgroundQuantifying variation of genetic traits over the geographical range of species is crucial for understanding the factors driving their range dynamics. The center-periphery hypothesis postulates, and many studies support, the idea that genetic diversity decreases and genetic differentiation increases toward the geographical periphery due to population isolation. The effects of environmental marginality on genetic variation has however received much less attention.MethodsWe tested the concordance between geographical and environmental gradients and the genetic predictions of center-periphery hypothesis for endemicLilium pomponiumin the southern Alps.ResultsWe found little evidence for concordance between genetic variation and both geographical and environmental gradients. Although the prediction of increased differentiation at range limits is met, genetic diversity does not decrease towards the geographical periphery. Increased differentiation among peripheral populations, th...
2013
When incompletely isolated taxa coexist in a patchy environment (e.g. mosaic hybrid zones, host-race complexes), patterns of variation may differ between selected traits/genes and neutral markers. While the genetic structure of selected traits/loci tends to coincide with habitat variables (producing Genetic-Environment Association or GEA), genetic differentiation at neutral loci unlinked to any selected locus rather depends on geographic connectivity at a large scale (e.g. Isolation-By-Distance or IBD), although these loci often display GEA at a small scale. This discrepancy has been repeatedly taken as evidence for parallel primary divergence driven by local adaptation. We argue that this interpretation needs to be addressed more thoroughly by considering the alternative hypothesis that speciation was initiated in allopatry and secondary introgression has subsequently erased the signal of past differentiation at neutral loci. We present a model of neutral introgression after secondary contact in a mosaic hybrid zone, which describes how GEAs dissipate with time and how neutral variation self-organizes according to the environmental and geographic structures. We show that although neutral loci can be affected by environmental selection, they are often more affected by history and connectivity: the neutral structure retains the initial geographic separation more than it correlates with the environment during the colonization and introgression phases, and then converges to a migration-drift balance, the most frequent outcome of which is GEA at a local scale but IBD at a large scale. This is the exact pattern usually attributed to parallel ecological speciation. Introgression is heterogeneous in space and depends on the landscape structure (e.g. it is faster in small patches, which are more impacted by immigration). Furthermore, there is no directionality in the association and it is possible to observe reversed GEAs between distant regions. We argue that the history of differentiation should ideally be reconstructed with selected loci or neutral loci linked to them, not neutral ones, and review some case studies for which the hypothesis of a long co-existence of co-adapted genetic backgrounds might have been refuted too hastily [Current Zoology 59 (1): 72-86, 2013].