Search results for " speciation"
showing 10 items of 272 documents
What do we need to know about speciation?
2011
Speciation has been a major focus of evolutionary biology research in recent years, with many important advances. However, some of the traditional organising principles of the subject area no longer provide a satisfactory framework, such as the classification of speciation mechanisms by geographical context into allopatric, parapatric and sympatry classes. Therefore, we have asked where speciation research should be directed in the coming years. Here, we present a distillation of questions about the mechanisms of speciation, the genetic basis of speciation and the relationship between speciation and diversity. Our list of topics is not exhaustive; rather we aim to promote discussion on rese…
Maintenance of male reaction to the congeneric song in the Hippolais warbler hybrid zone
1999
Both hybridization and competition may induce character shift on communication systems in hybrid zones, leading either to convergence or divergence. Melodious warblers Hippolais polyglotta and Icterine warblers H. icterina are interspecifically territorial and hybridize along a narrow contact zone. This spatial distribution is favoured by a reaction to the congeneric song. A character displacement, e.g. a decrease of the reaction, was expected within the hybrid zone because of reproduction costs lower than in allopatry. We investigated the pattern of variation of the interspecific reaction by comparing allopatric and sympatric populations. However, our data did not support the hypothesis ch…
Selection on size and secondary sexual characters of the damselfly Calopteryx splendens when sympatric with the congener Calopteryx virgo
2011
Male mating success is often determined by body size or secondary sexual characters because of female mate choice or competition for females. In addition to intraspecific interactions, interspecific interactions may interfere with intraspecific selection. In this study, we investigated sexual selection on size and sexual characters of male banded demoiselle ( Calopteryx splendens (Harris, 1780)) in wild populations sympatric with the beautiful demoiselle ( Calopteryx virgo (L., 1758)). As secondary sexual characters, male C. splendens have pigmented wing spots whose size appears to be under positive selection. Male C. virgo resemble male C. splendens that have the largest wing spots, leadi…
Evolution in the Arctic: a phylogeographic analysis of the circumarctic plant,Saxifraga oppositifolia(Purple saxifrage)
2003
Summary • A survey of chloroplast DNA variation in the circumarctic-alpine plant, Saxifraga oppositifolia, has resolved two highly divergent cpDNA lineages with geographically widespread and mainly allopatric distributions that are largely concordant with those of two subspecies, that is, subspp. oppositifolia and glandulisepala. These subspecies differ for a single morphological trait and hence level of morphological divergence does not equate to molecular divergence within the species. • The two cpDNA lineages were estimated to have diverged from their most recent common ancestor 5.37–3.76 Ma, that is, during the early to mid-Pliocene. • A nested clade analysis was conducted in an attempt…
Phylogeographic patterns of host-race evolution in Tephritis conura (Diptera: Tephritidae)
2006
Host-race evolution is a prime candidate for sympatric speciation because host shifts must take place in the presence of both hosts. However, the geographic context in which the shift takes place may have strong allopatric or peripatric components if the primary host within a localized area is scarce or even goes extinct. Inference of the relative importance of the geographic mode of speciation may be gained from phylogeographic imprints. Here, we investigate the phylogeography of host races of the tephritid fly Tephritis conura from sympatric, parapatric and allopatric populations of Cirsium heterophyllum and Cirsium oleraceum (Asteraceae) in Europe, for addressing the age and direction, a…
Morphological variation and the recent evolution of wing length in the icterine Warbler: A case of unidirectional introgression?
1999
Icterine Warbler Hippolais icterina and Melodious Warbler H. polyglotta are closely related species with parapatric breeding ranges. Their breeding ranges overlap only in a narrow zone in western Europe, where the Icterine Warbler population is presently declining and the Melodious Warbler population expanding. In eastern Burgundy (France), both species have bred in sympatry for at least forty years, but the Icterine Warbler started to decline in the mid-seventies. The two species differ in wing length and wing formula. Morphological variations of the wing were compared for the Icterine Warbler population in eastern Burgundy between 1965/76 and 1985/96. In the second period, wing length and…
Review paper: Ecological genetics of Brachionus sympatric sibling species
1998
In this paper we review previous studies on sympatric Brachionus populations in Torreblanca Marsh as a model of evolutionary and ecological relationships between closely related species. The marsh is a wetland on the Mediterranean coast of Spain with high spatial and temporal heterogeneity. Allozyme and morphometric analysis showed that Brachionus group plicatilis (formerly, Brachionus plicatilis and currently split into B. plicatilis and B. rotundiformis) was composed of three groups of genotypes with no evidence of gene flow between them (B. plicatilis, B. rotundiformis SM and B. rotundiformis SS). Correlations between seasonal and spatial distributions, on one hand, and temperature and s…
Crossed induction of sex in sympatric congeneric rotifer populations
2009
The transition from asexual to sexual reproduction in rotifers of the genus Brachionus (Monogononta) is triggered by a chemical signal produced and released by the rotifers themselves; the signal accumulates in the environment as population density increases. The response to this signal has been hypothesized to be speciesspecific. If not, the timing of sex and final diapausing egg production of a species might not be optimized. In this study, a set of experiments—based on individual and mass culture approaches—was carried out to investigate the differentiation in sex induction signals between sympatric and allopatric congeneric Brachionus populations by analyzing the capability of the mediu…
Molecular inference of a Late Pleistocene diversification shift inNigellas. lat. (Ranunculaceae) resulting from increased speciation in the Aegean ar…
2009
Aim To infer the temporal course and geographical mode of speciation in Mediterranean/Southwest Asian Nigella s. lat. Location Mediterranean Basin, Aegean archipelago. Methods Phylogenies for Nigella L. and Garidella L. (= Nigella s. lat.) were obtained from maximum-likelihood analyses of internal transcribed spacer (ITS) sequences. Diversification through time was analysed by log lineages-through-time (LTT) plots and survival analyses. Relative node age estimates were regressed against the degree of sympatry between sister clades to infer the predominant mode of geographical speciation in Nigella s. lat. Results The Late Pleistocene radiation of the Nigella arvensis complex in the Aegean r…
Allozymic variation and divergence in three species of Antirrhinum L. (Scrophulariaceae-Antirrhineae)
1999
Abstract An allozymic study of three wild species of Antirrhinum L.—A. lopesianum RothmA. mollissimum Rothm. and A. microphyllum Rothm.—is described. All are members of subsectionKickxiella Rothmand are narrow-range endemics of the Iberian Peninsula. The variability of the different loci, as well as the number and mobility of the alleles, differ among the three species, a demonstration of the usefulness of allozymes for the systematics of the genus. The finding of alleles unique to each species indicates high divergence among species suggesting ancient diversification, and supports the hypothesis of a geographical model of speciation. All three species show high levels of within-species var…