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981.
The third species of the Neotropical genus Leinendera Carrera, 1945, Leinendera
achaeta
sp. n., is described from Rio Grande do Sul state, Brazil. The habitus, wing and male terminalia are described and illustrated, and a key to the three Brazilian species is provided. 相似文献
982.
Small sweat bees (Hymenoptera: Halictidae) as potential major pollinators of melon (Cucumis melo) in the Mediterranean
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Sara Rodrigo Gómez Concepción Ornosa Jesús Selfa Miguel Guara Carlo Polidori 《Entomological Science》2016,19(1):55-66
In the current scenario of a general decline of the honeybee worldwide, studies on the potential of alternative bee species in pollinating cultivated plants are important. Although melon, Cucumis melo, is a crop with great commercial importance, there is very little information on its pollinating fauna in Europe, and none from the southern Mediterranean area. In a locality in central Spain, using both pan‐traps and net collections, we found that melon flowers are visited by 31 species of bees spanning four families, though only four were both dominant and constant. These four species belonged to the family Halictidae (sweat bees) and mostly (three species) to the genus Lasioglossum. Five other species could be defined as accessory: honeybee, Apis mellifera, and four other halictids. Individuals of the dominant species were smaller, on average, than those from all the other species. Observations on the frequency of pollen and nectar foraging and on flower visit duration further suggested L. malachurum as the potential key pollinator. Females of this species started to forage on melon early in the flowering season and exhibited two activity peaks in summer, thus covering the whole season. Although in other sites across continents melon seems to be more heavily pollinated by honeybees, this seems to be not the case in the Mediterranean, where sweat bees seem to be the major pollinators of this crop. 相似文献
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Nora H. Oleas Alan W. Meerow Javier Francisco‐Ortega 《Botanical journal of the Linnean Society. Linnean Society of London》2016,182(1):169-179
Phaedranassa schizantha (Amaryllidaceae) is an endangered species endemic to Ecuador and two varieties have been described: P. schizantha var. schizantha and P. schizantha var. ignea. We assessed population genetic structure and demographic patterns in 11 populations across the range of the species using 13 microsatellite loci. Our data show that genetic diversity was generally lower in the southern part of the range and was especially low in populations closest to cities. We found significant population differentiation (FST = 0.14, DEST = 0.34) and evidence of a genetic bottleneck. Genetic variation did not show isolation by distance. Instead, results suggest genetic barriers around two main cities. Bayesian analysis identified two genetic groups, neither of which represents either of the two varieties previously recognized. Coalescent analysis indicates a relatively recent colonization pattern between the two genetic groups (< 3000 generations). Conservation efforts need to be taken to facilitate genetic exchange between the groups, especially between locations that seem to be genetically isolated. 相似文献
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Rodrigo A. Grandy Troy W. Whitfield Hai Wu Mark P. Fitzgerald Jennifer J. VanOudenhove Sayyed K. Zaidi Martin A. Montecino Jane B. Lian André J. van Wijnen Janet L. Stein Gary S. Stein 《Molecular and cellular biology》2016,36(4):615-627
Stem cell phenotypes are reflected by posttranslational histone modifications, and this chromatin-related memory must be mitotically inherited to maintain cell identity through proliferative expansion. In human embryonic stem cells (hESCs), bivalent genes with both activating (H3K4me3) and repressive (H3K27me3) histone modifications are essential to sustain pluripotency. Yet, the molecular mechanisms by which this epigenetic landscape is transferred to progeny cells remain to be established. By mapping genomic enrichment of H3K4me3/H3K27me3 in pure populations of hESCs in G2, mitotic, and G1 phases of the cell cycle, we found striking variations in the levels of H3K4me3 through the G2-M-G1 transition. Analysis of a representative set of bivalent genes revealed that chromatin modifiers involved in H3K4 methylation/demethylation are recruited to bivalent gene promoters in a cell cycle-dependent fashion. Interestingly, bivalent genes enriched with H3K4me3 exclusively during mitosis undergo the strongest upregulation after induction of differentiation. Furthermore, the histone modification signature of genes that remain bivalent in differentiated cells resolves into a cell cycle-independent pattern after lineage commitment. These results establish a new dimension of chromatin regulation important in the maintenance of pluripotency. 相似文献
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