Rapid shoot‐to‐root signalling regulates root hydraulic conductance via aquaporins

We investigated how root hydraulic conductance (normalized to root dry weight, L_o) is regulated by the shoot. Shoot topping (about 30% reduction in leaf area) reduced L_o of grapevine (Vitis vinifera L.), soybean (Glycine max L.) and maize (Zea mays L.) by 50 to 60%. More detailed investigations with soybean and grapevine showed that the reduction in L_o was not correlated with the reduction in leaf area, and shading or cutting single leaves had a similar effect. Percentage reduction in L_o was largest when initial L_o was high in soybean. Inhibition of L_o by weak acid (low pH) was smaller after shoot damage or leaf shading. The half time of reduction in L_o was approximately 5 min after total shoot decapitation. These characteristics indicate involvement of aquaporins. We excluded phloem‐borne signals and auxin‐mediated signals. Xylem‐mediated hydraulic signals are possible since turgor rapidly decreased within root cortex cells after shoot topping. There was a significant reduction in the expression of several aquaporins in the plasma membrane intrinsic protein (PIP) family of both grapevine and soybean. In soybean, there was a five‐ to 10‐fold reduction in GmPIP1;6 expression over 0.5–1 h which was sustained over the period of reduced L_o.     

内蒙古上白垩统窃蛋龙科一新属种及其地层学意义(英文)

记述了一件发现于内蒙古临河巴彦满达呼上白垩统乌兰苏海组的窃蛋龙科新材料并建立了一新属新种——戈壁乌拉特龙(Wulatelong gobiensis gen. et sp. nov.)。新属种具有以下不同于其他窃蛋龙科成员的独特特征:外鼻孔大而细长,腹端低于前上颌骨中部;上颌骨的颧骨支呈带状,并向后延伸至眶前隔之后,叠覆于颧骨外侧面;外侧视,上隅骨的前背突基部收缩。戈壁乌拉特龙具有一些其他窃蛋龙科成员不具有的近祖特征,而与更原始的窃蛋龙类接近,说明戈壁乌拉特龙代表了窃蛋龙科中一个相对原始的属种。这些近祖特征包括:下颞颥孔的背缘较窄,泪骨的前突和后突相对较长,外翼骨和外下颌孔的位置都相对靠后,肩胛骨短而纤细,肠骨的耻骨茎较坐骨茎向腹侧延伸更长并前后向更宽,坐骨较短,以及第三跖骨近端侧扁等。因此戈壁乌拉特龙的系统发育位置可能居于原始窃蛋龙类和其他窃蛋龙科成员之间。对巴彦满达呼恐龙动物群的初步分析支持巴彦满达呼红层代表了蒙古高原戈壁地区上白垩统红层中的最早沉积层位的结论。     

Molecular genetic variation and population structure in morphologically differentiated cave and surface populations of the freshwater amphipod Gammarus minus

Gammarus minus is an important component of surface spring and cave ecosystems throughout Appalachia, and is a useful indicator of the hydrology and gene flow in freshwater communities. Gammarus minus populations occupying large cave passages (> 2 km) are usually troglomorphic, having reduced eyes, fewer ommatidia, larger body size, longer antennae, and reduced pigmentation relative to surface populations. We surveyed five cave stream and 10 surface spring populations for DNA sequence variation in the cytochrome c oxidase I (COI) and internal transcribed spacer 1 (ITS-1) genes with an aim towards characterizing phylogeographical structure and comparing the nature of genetic variation in cave vs. surface populations. Although standing variation at both loci was rather low within populations, a significant degree of divergence and spatial structuring of populations was observed. Levels of genetic variation within cave and spring populations differed substantially, with caves harbouring significantly less variation at the COI locus than surface springs. Codon usage bias was significantly lower in caves, indicating that cave streams harbour smaller and/or more recently colonized populations. Overall these data indicate limited gene flow among populations and suggest that the cave populations sampled in this study are prone to bottlenecks, possibly due to larger temperature fluctuations and more frequent incidence of drought conditions associated with these particular cave habitats.     

The Culture of Migration in Southern Mexico

The Culture of Migration in Southern Mexico . Jeffrey H. Cohen. Austin: University of Texas Press, 2004. 195 pp.     

Assessment of gene flow across a hybrid zone in red-tailed chipmunks (Tamias ruficaudus)

The role of hybridization in animal speciation is controversial and recent research has challenged the long-standing criterion of complete reproductive isolation to attain species status. The speciation-with-gene-flow model posits that the genome is semi-permeable and hybridization may be a phase in the process of divergence. Here, we apply these concepts to a previously identified zone of mtDNA introgression between the two strongly morphologically differentiated subspecies of red-tailed chipmunk ( Tamias ruficaudus ) in the US Inland Northwest. Using multilocus genotype data from the southern, older contact zone, we demonstrate that neutral gene flow is unusually low between the subspecies across the Lochsa River. This is geographically congruent with the discontinuity in bacular morphology, indicating that the cline of mitochondrial DNA (mtDNA) haplotypes is displaced. Furthermore, we elucidate the evolutionary forces responsible by testing hypotheses of lineage sorting and hybridization. We determined that introgressive hybridization is the cause of mtDNA/morphology incongruence because there are non-zero levels of migration and gene flow. Although our estimate of the age of the hybrid zone has wide credibility intervals, the hybridization events occurred in the Late Pleistocene and the divergence occurred in the Middle Pleistocene. Finally, we assessed substructure within and adjacent to the hybrid zone and found that the hybrid zone constitutes a set of populations that are genetically differentiated from parental sets of populations; therefore, hybridization in this system is not likely an evolutionary sink, but has generated novel combinations of genotypes.     

Monitoring exposure to avian influenza viruses in wild mammals

• 1 Avian influenza (AI) viruses primarily circulate in wild waterfowl populations and are occasionally transmitted to domestic poultry flocks. However, the possible roles of other wildlife species, such as wild mammals, in AI virus ecology have not been adequately addressed.
• 2 Due to their habitat and behaviour, many wild mammals may be capable of transmitting pathogens among wild and domestic populations. Exposure to AI viruses has been reported in an array of wild and domestic animals. The presence of wild mammals on farms has been identified as a risk factor for at least one poultry AI outbreak in North America. These reports suggest the need for seroprevalence studies examining the exposure of wild mammals to AI viruses.
• 3 Serological tests are routinely used to assess domestic poultry, domestic swine and human exposure to influenza A viruses, but these tests have not been validated for use in wild mammals. As such, some of these protocols may require adjustments or may be inappropriate for use in serology testing of wild mammals. Herein, we review these serological techniques and evaluate their potential usefulness in AI surveillance of wild mammals. We call for care to be taken when applying serological tests outside their original area of validation, and for continued assay verification for multiple species and virus strains.