Search results for "Reproductive Isolation"
showing 10 items of 72 documents
Niche filling slows the diversification of Himalayan songbirds.
2013
In Himalayan songbirds, the speciation rate is ultimately set by ecological competition, rather than by the rate of acquisition of reproductive isolation. The beginnings of adaptive radiation and speciation have been widely studied — in Darwin's finches, sticklebacks and cichlid fish, for example — but relatively little is known about what happens next. Specifically, what is the rate-limiting step for the establishment of new species? This seven-year study of the 358 songbird species found on the Himalayan slopes suggests that it is the rates at which new niches are created and occupied that limits diversification, not the rate at which new species form through reproductive isolation. Speci…
Surface glycoproteins in copepods: potential signals for mate recognition
1994
The mechanism male copepods use to recognize mates is not well understood. Both chemical and mechanical cues have been implicated, but the relative importance of these is not known. This lack of knowledge is despite the belief that mate recognition has a critical role in maintaining reproductive isolation of many species and influences the direction of evolution. Glycoproteins are used as mating signals by a number of aquatic organisms including rotifers, ciliates, and algae. We have developed techniques for selectively probing surface glycoproteins in zooplankton using fluorescently labeled lectins. We examined surface glycoproteins on the urosomes of several species of marine and freshwat…
Past climate changes facilitated homoploid speciation in three mountain spiny fescues (Festuca, Poaceae)
2016
Apart from the overwhelming cases of allopolyploidization, the impact of speciation through homoploid hybridization is becoming more relevant than previously thought. Much less is known, however, about the impact of climate changes as a driven factor of speciation. To investigate these issues, we selected Festuca picoeuropeana, an hypothetical natural hybrid between the diploid species F. eskia and F. gautieri that occurs in two different mountain ranges (Cantabrian Mountains and Pyrenees) separated by more than 400 km. To unravel the outcomes of this mode of speciation and the impact of climate during speciation we used a multidisciplinary approach combining genome size and chromosome coun…
Linguistic, geographic and genetic isolation: a collaborative study of Italian populations
2014
Summary - The animal and plant biodiversity of the Italian territory is known to be one of the richest in the Mediterranean basin and Europe as a whole, but does the genetic diversity of extant human populations show a comparable pattern? According to a number of studies, the genetic structure of Italian populations retains the signatures of complex peopling processes which took place from the Paleolithic to modern era. Although the observed patterns highlight a remarkable degree of genetic heterogeneity, they do not, however, take into account an important source of variation. In fact, Italy is home to numerous ethnolinguistic minorities which have yet to be studied systematically. Due to …
Recent speciation and secondary contact in endemic ants
2014
Gene flow is the main force opposing divergent selection, and its effects are greater in populations in close proximity. Thus, complete reproductive isolation between parapatric populations is not expected, particularly in the absence of ecological adaptation and sharp environmental differences. Here, we explore the biogeographical patterns of an endemic ant species, Cataglyphis floricola, for which two colour morphs (black and bicolour) coexist in parapatry throughout continuous sandy habitat in southern Spain. Discriminant analyses of six biometric measurements of male genitalia and 27 cuticular hydrocarbons reveal high differentiation between morphs. Furthermore, the low number of shared…
Behavioral reproductive isolation among sympatric strains of Brachionus plicatilis Müller 1786: insights into the status of this taxonomic species
1995
We present results on cross-mating experiments using Brachionus plicatilis strains collected in three ponds of a coastal marsh (Torreblanca Marsh, Castellon, Spain). These strains were known to differ widely both in morphology and allozyme patterns from a previous study, where they were grouped into three genetically different clonal groups. Although some of the strains co-occurred in the same pond and sexual periods overlapped, no gene flow was found among them. Our first objective was to determine whether behavioral reproductive isolation was responsible for the absence of interbreeding. A second objective was to explore the relationship between sexual isolation and genetic divergence. We…
Postzygotic isolation between the two European subspecies of the house mouse: estimates from fertility patterns in wild and laboratory-bred hybrids
2005
We assessed the fertility (reproductive success, litter size, testis weight, spermatocyte-to-spermatid ratio) of F 1 s and backcrosses between different wild-derived outbred and inbred strains of two mouse subspecies, Mus musculus domesticus and M. m. musculus. A significant proportion of the F 1 females between the outbred crosses did not reproduce, suggesting that female infertility was present. As the spermatocyte-to-spermatid ratio was correlated with testis weight, the latter was used to attribute a sterile vs. fertile phenotype to all males. Segregation proportions in the backcrosses of F 1 females yielded 11 (inbred) to 17% (outbred) sterile males, suggesting the contribution of two …
On the verge of extinction: genetics of the critically endangered Iberian plant species, Borderea chouardii (Dioscoreaceae) and implications for cons…
2005
Borderea chouardii is a relictual and dioecious, strictly sexually reproducing, long-living geophyte of the Dioscoreaceae family. Previous biological and demographic studies have indicated the existence of a uniformly distributed panmictic population of this taxon at the southernmost Spanish pre-Pyrenean mountain ranges where it occurs in rather inaccessible crevices of a single limestone cliff. However, individuals of B. chouardii are spatially subdivided into two subpopulations located, respectively, on the upper and lower parts of the cliff, and vertically separated 150 m. Because of its extreme rarity, B. chouardii was the first Iberian taxon to have a specific conservation plan and has…
Dissimilar molecular and morphological patterns in an introgressed peripheral population of a sand dune species ( Armeria pungens , Plumbaginaceae)
2019
Introgression is a poorly understood evolutionary outcome of hybridisation because it may remain largely undetected whenever it involves the transfer of small parts of the genome from one species to another. Aiming to understand the early stages of this process, a putative case from the southernmost border of the Armeria pungens range from its congener A. macrophylla is revisited following the discovery of a subpopulation that does not show phenotypic signs of introgression and resembles typical A. pungens. We analysed morphometrics, nuclear ribosomal DNA ITS and plastid DNA (trnL‐trnF) sequences, genome size, 45S and 5S rDNA loci‐FISH data and nrDNA IGS sequences. Within the study site, mo…
Strong reproductive barriers in a narrow hybrid zone of West-Mediterranean green toads (Bufo viridis subgroup) with Plio-Pleistocene divergence
2010
Abstract Background One key question in evolutionary biology deals with the mode and rate at which reproductive isolation accumulates during allopatric speciation. Little is known about secondary contacts of recently diverged anuran species. Here we conduct a multi-locus field study to investigate a contact zone between two lineages of green toads with an estimated divergence time of 2.7 My, and report results from preliminary experimental crosses. Results The Sicilian endemic Bufo siculus and the Italian mainland-origin B. balearicus form a narrow hybrid zone east of Mt. Etna. Despite bidirectional mtDNA introgression over a ca. 40 km North-South cline, no F1 hybrids could be found, and nu…