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Significant Reproductive Isolation (significant + reproductive_isolation)
Selected AbstractsLaboratory environments are not conducive for allopatric speciationJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2002A.-B. Florin We review published records of laboratory experiments on peripatric and vicariance allopatric speciation to address the following three questions: (1) What was the true effect size of reproductive isolation? (2) Was the reproductive isolation persistent? (3) What influenced the development of isolation? Contrary to popular belief, laboratory evidence for allopatric speciation is quite weak. Assortative mating was only found among derived populations in vicariance experiments. Reproductive isolation against control populations was only intermittent, so there is reason to doubt if some cases showing significant reproductive isolation really should be attributed to speciation. The method of testing was at least as important as the speciation model. Experimental populations tested against each other were the most likely to demonstrate reproductive isolation. This study suggests that allopatric speciation experiments are more likely to yield conclusive results under divergent selection than under drift, and points to the benefits of large populations and many generations. [source] Effect of Seasonality on Distribution of Macroalgae in a Stream System (Xin'an Spring) in Shanxi Province, North ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 8 2006Bian-Fang Hu Abstract A survey of the seasonal distribution of macroalgae in a stream system in Shanxi Province, north China, was undertaken from July 2004 to April 2005. The relative abundance and percentage cover of macroalgae, and several environmental factors were monitored along a 20-m stretch at each of four sites, at intervals of approximately three months (one sampling per season). Several stream conditions were relatively constant over the sampling period (pH, maximum width and maximum depth), whereas others exhibited a distinct seasonal pattern (water temperature and specific conductance), and some fluctuated with no discernable seasonal pattern (current velocity and dissolved oxygen). Forty-two species of macroalgae were found, with a predominance of Chlorophyta (26 species, 61.9%). Rhodophyta and Charophyta represented the smallest proportion (1 species each, 2.38%). Six macroalgae species were the most widespread, occurring in all four sampling sites. Twelve species were found at only one site each. In terms of seasonality, eight species occurred throughout the year, whereas 16 species were found in only one season each. The macroalgal community at Xin'an Spring was species rich relative to other streams. Species richness per sampling site was negatively correlated with pH. Principal component analysis revealed that no single variable had much influence on the macroalgal seasonal dynamics. We calculated Sorensen similarity indices to compare our study with other continent-wide surveys of stream macroalgae, but the similarity indices were all very low. This study also shows that macroalgae in different locations have significant reproductive isolation. (Managing editor: Ya-Qin Han) [source] Reproductive isolating barriers between colour-differentiated populations of an African annual killifish, Nothobranchius korthausae (Cyprinodontiformes)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010MARTIN REICHARD Allopatric populations separated by vicariance events are expected to evolve reproductive isolating mechanisms as a result of disparate selection pressures and genetic drift. The appearance of reproductive isolating mechanisms may vary across taxa with differences in the opportunity for mate choice, and may be asymmetrical. In addition, premating barriers may be affected by individual mating experience. We used choice and no-choice experiments to investigate reproductive isolation between two allopatric (island and mainland) and colour-differentiated populations of an African annual fish, Nothobranchius korthausae. Assortative mating under experimental conditions was limited and asymmetrical. Preference for sympatric males was only expressed in nonvirgin females from one population. Virgin fish from both populations mated indiscriminately. No difference in the number of eggs laid, fertilization rate and hatching success was detected in no-choice experiments. All mating combinations produced viable offspring and no postmating barriers were detected in terms of the performance and fertility of F1 hybrids. Overall, we found little evidence for significant reproductive isolation, which is in contrast with the related killifish taxa in which assortative mating can be strong, even among allopatric populations with no colour differentiation. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 62,72. [source] Description, biology and conservation of a new species of Australian tree frog (Amphibia: Anura: Hylidae: Litoria) and an assessment of the remaining populations of Litoria genimaculata Horst, 1883: systematic and conservation implications of an unusual speciation eventBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2007CONRAD J. HOSKIN The Australian populations of the green-eyed tree frog Litoria genimaculata consist of a northern and southern genetic lineage that meet in a mosaic contact zone comprising two independent areas of contact: one where the main ranges of the lineages overlap, and the second where a population of the southern lineage is isolated within the range of the northern lineage. A recent study failed to find significant reproductive isolation between the main ranges of the two lineages, despite deep genetic divergence, partial postzygotic isolation, and call differences. The study did, however, demonstrate rapid phenotypic divergence and speciation of the isolated population of the southern lineage from both the parapatric northern lineage and from the allopatric, but genetically similar, main range of the southern lineage. Herein, the isolated population of the southern lineage is described as a distinct species, Litoria myola sp. nov., whereas the remainder of the southern lineage and the northern lineage are retained as a single, paraphyletic species, Litoria genimaculata. Resolving this unusual systematic situation demonstrates the value of using multiple lines of evidence in delimiting species. Litoria myola sp. nov. has a very small distribution and population size and warrants a Critically Endangered listing (B1, 2) under IUCN criteria. Threats and management recommendations are outlined, and the conservation of hybrid zones as areas of evolutionary novelty is discussed. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 549,563. [source] | ||||||||||