Time filter

Source Type

Vairao, Portugal

Gracia E.,University Miguel Hernandez | Gimenez A.,University Miguel Hernandez | Anadon J.D.,University Miguel Hernandez | Harris D.J.,CIBIO | And 2 more authors.
Journal of Biogeography | Year: 2013

Aim: Recent biogeographical studies have postulated a North African, Late Pleistocene, origin for some species of the Iberian Peninsula. However, a robust assessment of such range expansions requires high-resolution molecular tools to resolve overlapping biogeographical and cultural processes. Here we aim to determine whether the spur-thighed tortoise, Testudo graeca, arrived in south-eastern Spain during historical or prehistoric times, and whether its dispersal to the Iberian Peninsula was human-mediated. Location: The western Mediterranean Basin (south-eastern Spain, northern Algeria and north-western Morocco). Methods: Using 428 samples from 19 sites in North Africa and 18 in south-eastern Spain, we obtained mitochondrial sequences from the cytochrome b gene and genotypes derived from seven microsatellite loci. These data were employed to obtain population genetics descriptors, haplotype networks, Bayesian cluster analyses and isolation-by-distance patterns. Moreover, we used a Bayesian demographic approach to delimit the dates involved in the range expansion. Results: We found lower levels of genetic variability and weak mitochondrial differentiation in the south-eastern Spanish tortoises compared with the North African ones. However, exclusive haplotypes occurred in the Iberian samples and microsatellite cluster analyses revealed moderate levels of admixture across both sides of the Mediterranean. A coastal area in the west of Algeria and the central-southern region in south-eastern Spain are suggested as the most probable founder and arrival places, respectively. Finally, we identified signatures of an ancient bottleneck event approximately 20,000-30,000 years ago. Main conclusions: The spur-thighed tortoise probably arrived in south-eastern Spain during Late Pleistocene sea-level low stands. The role that humans may have played as dispersers across the Mediterranean remains unclear. Our results are in accordance with other recent findings of trans-Mediterranean expansions during this period and highlight the importance of employing precise methodological approaches before a species can be considered as historically introduced. © 2012 Blackwell Publishing Ltd. Source

Gracia E.,University Miguel Hernandez | Botella F.,University Miguel Hernandez | Anadon J.D.,CSIC - Donana Biological Station | Anadon J.D.,Arizona State University | And 4 more authors.
Biology Letters | Year: 2013

Much of our current knowledge about the genetic dynamics in range expansions originates from models, simulations and microcosm experiments that need to be corroborated by field data. Here,we report a neutral genetic pattern that matches the predictions of the genetic surfing theory. Genetic surfing occurs when repeated founding events and genetic drift act on the wave of advance of an expanding population, promoting strong spatial structure. In the range expansion of the tortoise Testudo graeca from North Africa to southeastern Spain, we found several genetic signatures consistent with surfing: a decrease of genetic diversity with distance from the initial founder area, clinal patterns in allele frequencies, rare African alleles which have become common at distal sites in the Spanish range, and stronger spatial differentiation in the expanded range than in the original one. Our results provide support for the theory that genetic drift can be an important force in shaping the genetic structure of expanding populations. © 2013 The Author(s) Published by the Royal Society. Source

Segurado P.,CIBIO | Segurado P.,University of Lisbon | Kunin W.E.,University of Leeds | Filipe A.F.,University of Lisbon | And 3 more authors.
Basic and Applied Ecology | Year: 2012

Inferring biotic interactions from the examination of patterns of species occurrences has been a central tenet in community ecology, and it has recently gained interest in the context of single-species distribution modelling. However, understanding of how spatial extent and grain size affect such inferences remains elusive. For example, would inferences of biotic interactions from broad-scale patterns of coexistence provide a surrogate for patterns at finer spatial scales? In this paper we examine how the spatial and environmental association between two closely related species of freshwater turtles in the Iberian Peninsula is affected by the geographical extent and resolution of the analysis. Species coexistence was compared across spatial scales using five datasets at varying spatial extents and resolutions. Both similarities in the two species' use of space and in their responses to environmental variables were explored by means of regression analyses. We show that a positive association between the two species measured at broader scales can switch to a negative association at finer scales. We demonstrate that without examination of the effects of spatial scale when investigating biotic interactions using co-occurrence patterns observed at coarse resolutions, conclusions can be deeply misleading. © 2012 Gesellschaft für ökologie. Source

Visnevschi-Necrasov T.,CIBIO | Visnevschi-Necrasov T.,University of Porto | Harris D.J.,CIBIO | Faria M.A.,Laboratory of Food and Water Science | And 3 more authors.
Spanish Journal of Agricultural Research | Year: 2012

Genetic diversity within Iberian populations of Ornithopus pinnatus, O. compressus, O. sativus and Biserrula pelecinus were assessed using ITS1 and ITS2 DNA sequences from sixty four specimens, and a phylogeny between Ornithopus species was estimated. Generally within-species variation was low, particularly within Ornithopus. The Mediterranean species of Ornithopus form a sister clade relative to the South American O. micranthopus. The sometimes considered a full species, O. sativus isthmocarpus, was not distinct from O. sativus. Between some species there is limited genetic divergence using these markers, although the situation of O. perpusillus requires additional specimens to be examined before firm conclusions can be drawn. Source

Abbott R.,University of St. Andrews | Albach D.,Carl von Ossietzky University | Ansell S.,Natural History Museum in London | Arntzen J.W.,Netherlands Center for Biodiversity Naturalis | And 36 more authors.
Journal of Evolutionary Biology | Year: 2013

Hybridization has many and varied impacts on the process of speciation. Hybridization may slow or reverse differentiation by allowing gene flow and recombination. It may accelerate speciation via adaptive introgression or cause near-instantaneous speciation by allopolyploidization. It may have multiple effects at different stages and in different spatial contexts within a single speciation event. We offer a perspective on the context and evolutionary significance of hybridization during speciation, highlighting issues of current interest and debate. In secondary contact zones, it is uncertain if barriers to gene flow will be strengthened or broken down due to recombination and gene flow. Theory and empirical evidence suggest the latter is more likely, except within and around strongly selected genomic regions. Hybridization may contribute to speciation through the formation of new hybrid taxa, whereas introgression of a few loci may promote adaptive divergence and so facilitate speciation. Gene regulatory networks, epigenetic effects and the evolution of selfish genetic material in the genome suggest that the Dobzhansky-Muller model of hybrid incompatibilities requires a broader interpretation. Finally, although the incidence of reinforcement remains uncertain, this and other interactions in areas of sympatry may have knock-on effects on speciation both within and outside regions of hybridization. © 2013 European Society For Evolutionary Biology. Source

Discover hidden collaborations