Search results for "Allopatric speciation"
showing 10 items of 61 documents
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…
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…
Speciation via Differential Host–Plant Use in the Tephritid Fly Tephritis conura
2010
The close association between phytophagous insects and host plants and the possibility for specialization on new plants make phytophagous insects prime candidates for sympatric speciation via host-race evolution. In this chapter, we summarize results addressing host-race evolution in the tephritid fly Tephritis conura (Tephritidae) infesting Cirsium heterophyllum and C. oleraceum (Asteraceae). Host plant distributions in allopatry, sympatry and parapatry, and different infestation patterns enabled us to test geographic speciation scenarios, investigate adaptations, and address the importance of plant population history for diversification of T. conura.
Diversity and taxonomy of the genus Unio Philipsson in Italy, with the designation of a neotype for Unio elongatulus C. Pfeiffer (Mollusca, Bivalvia,…
2019
Novel Unio spp. populations from Slovenia, the Italian peninsula, Sardinia and Sicily were genetically analysed in order to define the distribution and diversity of the genus Unio in Italy and neighbouring areas. The presence of two primarily allopatric autochtonous species, Unio elongatulus Pfeiffer, and Unio mancus Lamarck, is confirmed for the Italian peninsula, Corsica, Sardinia, and Sicily. Autochthonous populations of Unio elongatulus are present in the peri-Adriatic drainages of the Italian and Balkan peninsulas, south as far as the Ofanto River (Apulia, Italy) and Lake Skadar (Albania), while its presence in the Tyrrhenian rivers of Tuscany is likely due to anthropogenic introductio…
Phenotypic analysis of adults of Fasciola hepatica, Fasciola gigantica and intermediate forms from the endemic region of Gilan, Iran.
2006
Fascioliasis is an important human and animal disease caused by Fasciola hepatica and Fasciola gigantica. In Iran, the distribution of these two species overlaps in most areas, including the northern human endemic province of Gilan where both fasciolids are simultaneously found in individual cattle and buffaloes. A phenotypic study of fasciolid adult flukes from naturally infected bovines from Gilan was carried out by means of an exhaustive morphometric analysis using traditional microscopic measurements and an allometric model. The Iranian fasciolids were compared to F. hepatica and F. gigantica standard populations, i.e. from geographical areas where both species do not co-exist (Bolivia …
LOCAL ADAPTATION, RESISTANCE, AND VIRULENCE IN A HEMIPARASITIC PLANT-HOST PLANT INTERACTION
2000
Coevolution may lead to local adaptation of parasites to their sympatric hosts. Locally adapted parasites are, on average, more infectious to sympatric hosts than to allopatric hosts of the same species or their fitness on the sympatric hosts is superior to that on allopatric hosts. We tested local adaptation of a hemiparasitic plant, Rhinanthus serotinus (Scrophulariaceae), to its host plant, the grass Agrostis capillaris. Using a reciprocal cross-infection experiment, we exposed host plants from four sites to hemiparasites originating from the same four sites in a common environment. The parasites were equally able to establish haustorial connections to sympatric and allopatric hosts, and…
Mate recognition as a reproductive barrier in sexual and parthenogenetic Eucypris virens (Crustacea, Ostracoda)
2013
Mate selection is one of the motors of evolution and of particular importance in the case of organisms in which sexual and parthenogenetic populations coexist. Sexual populations of the ostracod species complex Eucypris virens are often mixed with parthenogenetic ones. A powerful mate selection mechanism must exist to avoid time, energy and sperm loss, for the maintenance and success of sexual reproduction in these mixed populations. There are four types of E. virens individuals: males (diploid), sexual females (diploid) and asexual females (parthenogenetic and either di- or triploid). From one parthenogenetic population and two populations with males of E. virens, we sampled early stage ju…
On the identity of Ischyropsalis dentipalpis Canestrini, 1872 and description of Ischyropsalis lithoclasica sp. n. (Opiliones: Ischyropsalididae)
2010
Ischyropsalis dentipalpis Canestrini, 1872 is re-defined, and a neotype from the type locality in the Aosta Valley, Italy, is assigned. I. helvetica Roewer, 1916 (sensu Martens 1978) is shown to be conspecific and therefore is synonymised with I. dentipalpis. A population from Bergamo Province, Italy, formerly assigned to I. dentipalpis (sensu Martens 1978), is here regarded as a different species and described under the name Ischyropsalis lithoclasica sp. n. Discrimination of males is possible by genital characters and by the shape of the cheliceral and pedipalpal apophyses. Females are distinguished by peculiarities of cheliceral spination. The distribution of I. lithoclasica n. sp. is al…