Characterization of microsatellite markers for rough fescue species (Festuca spp.)

One major challenge in genetic diversity analysis of minor grass species is the lack of informative molecular markers. A set of 210 simple sequence repeat (SSR) markers developed from wheat and barley were evaluated for their transferability to three rough fescue species [Festuca altaica Trinius, F. campestris (Rydb.) and F. hallii (Vassey) Piper]. Twelve SSR primer pairs displayed scorable polymorphism among and within the species. The number of alleles per primer pair ranged from three to 17 with an average of 8.3 for all the species and greatly varied for each species. About 82% of SSR variation resided within the species. Festuca hallii was genetically most distinct among the three species.     

Quality indexes to assess the reliability of genotypes in studies using noninvasive sampling and multiple‐tube approach

In noninvasive studies, the intersample variance in DNA quality and quantity is large, and produces multilocus genotypes of highly variable quality. Here we propose a standardized method for testing the reliability of the genotyping procedure when using the multiple‐tube approach. The quality indexes generated will allow reliable comparisons among samples, loci, studies, and field and/or laboratory protocols. These indexes represent a powerful tool for the quality management of noninvasive studies.     

THE MORPHOLOGY, ULTRASTRUCTURE AND FUNCTION OF THE FEEDING APPARATUS OF SAYELLA FUSCA (C.B. ADAMS, 1839) (GASTROPODA: PYRAMIDELLIDAE)

Scanning and transmission electron microscopy in conjunctionwith histology and dissection were employed to investigate theforegut anatomy of Sayella fusca (C.B. Adams, 1839), a commonNew England pyramidellid snail. Certain aspects of the feedingapparatus of S. fusca, including the buccal pump and proboscisanatomy, depart from the characteristic pyramidellid plan. Somedifferences such as the position of the introvert/proboscisaperture and the common oral and stylet canal are shared withthe genera Turbonilla, Eulimella, and Pyramidella. Three characteristicsof the feeding apparatus are unique to S. fusca: (1) the buccalpump is not divided into two pouches but exists as a singlemuscular bulb; (2) the entire lumen of the buccal pump, notsimply a portion of it, possesses a cuticular lining; and (3)the salivary ducts never enter the muscular walls of the buccalpump. Histological studies of the salivary gland indicate thatthree types of secretory cells are intermittently distributedthroughout the entire gland rather than characterizing distinctregions as described for other members of the family Pyra-midellidae.In contrast to previous findings, the gland cells of S. fuscaexhibit a merocrine secretion. The taxonomic value of the buccalpump and proboscis morphology are discussed. ^*Present address: Dauphin Island Sea Lab, 101 Bienville Boulevard,Post Office Box 369–370, Dauphin Island, Alabama 36528USA. (Received 9 November 1993; accepted 1 October 1997)     

适应辐射类群穇属的系统学研究进展

综合花序拓扑学、比较形态学、分子系统发育、细胞遗传学等资料,对适应辐射类群穆属(Eleusine Gaertn.)的系统学研究进展进行了述评.穆属系统位置--Eleusiinae亚族成员得到分子系统发育证据的支持.该属具有3种花序类型、7个基因组类型、多倍体均由二倍体杂交起源、C4植物高度适应半湿润-半干旱镶嵌气候等特征.据可靠化石记载和现代地理分布推断,穆属很可能起源于东非,时间是晚中新世,而适应辐射则发生在上新世-中新世间隔.总的来说,分子系统发育、细胞遗传学、古地质、古气候数据的整合研究能够为穆属多倍体起源和谱系多样化历史提供令人信服的证据.     

Where's the glass? Biomarkers,molecular clocks,and microRNAs suggest a 200‐Myr missing Precambrian fossil record of siliceous sponge spicules

The earliest evidence for animal life comes from the fossil record of 24-isopropylcholestane, a sterane found in Cryogenian deposits, and whose precursors are found in modern demosponges, but not choanoflagellates, calcareans, hexactinellids, or eumetazoans. However, many modern demosponges are also characterized by the presence of siliceous spicules, and there are no convincing demosponge spicules in strata older than the Cambrian. This temporal disparity highlights a problem with our understanding of the Precambrian fossil record – either these supposed demosponge-specific biomarkers were derived from the sterols of some other organism and are simply retained in modern demosponges, or spicules do not primitively characterize crown-group demosponges. Resolving this issue requires resolving the phylogenetic placement of another group of sponges, the hexactinellids, which not only make a spicule thought to be homologous to the spicules of demosponges, but also make their first appearance near the Precambrian/Cambrian boundary. Using two independent analytical approaches and data sets – traditional molecular phylogenetic analyses and the presence or absence of specific microRNA genes – we show that demosponges are monophyletic, and that hexactinellids are their sister group (together forming the Silicea). Thus, spicules must have evolved before the last common ancestor of all living siliceans, suggesting the presence of a significant gap in the silicean spicule fossil record. Molecular divergence estimates date the origin of this last common ancestor well within the Cryogenian, consistent with the biomarker record, and strongly suggests that siliceous spicules were present during the Precambrian but were not preserved.     

Review of the ecology of Australian urban fauna: A focus on spatially explicit processes

Abstract Cities have a major impact on Australian landscapes, especially in coastal regions, to the detriment of native biodiversity. Areas suitable for urban development often coincide with those areas that support high levels of species diversity and endemism. However, there is a paucity of reliable information available to guide urban conservation planning and management, especially regarding the trade‐off between investing in protecting and restoring habitat at the landscape level, and investing in programmes to maintain the condition of remnant vegetation at the local (site) level. We review the literature on Australian urban ecology, focusing on urban terrestrial and aquatic vertebrate and invertebrate fauna. We identify four main factors limiting our knowledge of urban fauna: (i) a lack of studies focusing at multiple ecological levels; (ii) a lack of multispecies studies; (iii) an almost total absence of long‐term (temporal) studies; and (iv) a need for stronger integration of research outcomes into urban conservation planning and management. We present a set of key principles for the development of a spatially explicit, long‐term approach to urban fauna research. This requires an understanding of the importance of local‐level habitat quality and condition relative to the composition, configuration and connectivity of habitats within the larger urban landscape. These principles will ultimately strengthen urban fauna management and conservation planning by enabling us to prioritize and allocate limited financial resources to maximize the conservation return.     

Sequence and functional analyses of Haemophilus spp. genomic islands

Background

A major part of horizontal gene transfer that contributes to the diversification and adaptation of bacteria is facilitated by genomic islands. The evolution of these islands is poorly understood. Some progress was made with the identification of a set of phylogenetically related genomic islands among the Proteobacteria, recognized from the investigation of the evolutionary origins of a Haemophilus influenzae antibiotic resistance island, namely ICEHin1056. More clarity comes from this comparative analysis of seven complete sequences of the ICEHin1056 genomic island subfamily.

Results

These genomic islands have core and accessory genes in approximately equal proportion, with none demonstrating recent acquisition from other islands. The number of variable sites within core genes is similar to that found in the host bacteria. Furthermore, the GC content of the core genes is similar to that of the host bacteria (38% to 40%). Most of the core gene content is formed by the syntenic type IV secretion system dependent conjugative module and replicative module. GC content and lack of variable sites indicate that the antibiotic resistance genes were acquired relatively recently. An analysis of conjugation efficiency and antibiotic susceptibility demonstrates that phenotypic expression of genomic island-borne genes differs between different hosts.

Conclusion

Genomic islands of the ICEHin1056 subfamily have a longstanding relationship with H. influenzae and H. parainfluenzae and are co-evolving as semi-autonomous genomes within the 'supragenomes' of their host species. They have promoted bacterial diversity and adaptation through becoming efficient vectors of antibiotic resistance by the recent acquisition of antibiotic resistance transposons.     

Response of plant roots to elevated atmospheric carbon dioxide

Plant root response to atmospheric CO₂ enrichment can be great. Results from this controlled environment investigation demonstrate substantial effects on root system architecture, micromorphology and physiology. The most pronounced effects were an increase in root length (110%) and root dry weight (143%). Root diameter, stele diameter, cortex width, root/shoot and root weight ratios all increased; root numbers did not increase. The long-term implications for belowground processes could be enormous.