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101.
ALFRED C. LENZ 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1994,27(2):111-117
The late Homerian was a time of profound importance to graptolites. Following the complete extinction of Cyrtograptus and the near extinction of Monograptus (s.s.)at the end of the lundgrenitestis Zone(lower Homerian, upper Wenlock), the morphologically simple and long-ranging Pristiograptus dubius lineage underwent rapid (opportunistic) cladogenesis during the succeeding upper Homerian. Two clades, each with novel and sometimes complex sicular and thecal structures, appeared. One clade, the 'Pristiograptus' praedeubeli group, gave rise to similar but more complex species, such as ' P.' ludensis and 'P.' deubeli , which in turn gave rise to Ludlow taxa, including Saetograptus (s.l.) and Pseudomonclimacis. The other clade, the Lobograptus group, gave rise to Ludlow taxa Lobograptus, Neolobograptus, Bohemograptus , and Neocucullograptus some with very complex thecal structures. Ludlow and younger monograptid faunas therefore comprise at least three separate lineages: Monograptus (s.s.), the Lobograptus group (clade), and the 'Pristiograptus' praedeubeli group (clade). Cladogenesis, evolution, extinction, Homerian, PRISTIOGRAPTUS, LOBOGRAPTUS 相似文献
102.
C. EIZAGUIRRE† S. E. YEATES‡ T. L. LENZ M. KALBE M. MILINSKI 《Molecular ecology》2009,18(15):3316-3329
Polymorphic genes of the major histocompatibility complex (MHC) are regarded as essential genes for individual fitness under conditions of natural and sexual selection. To test this hypothesis, we investigated the ultimate individual fitness trait — that of reproductive success. We used three-spined sticklebacks ( Gasterosteus aculeatus ) in seminatural enclosures, located in natural breeding areas where the experimental fish had been caught. During their reproductive period, fish were exposed continuously to their natural sympatric parasites. By genotyping almost 4000 eggs with nine microsatellites, we determined parenthood and inferred female mating decision. We found that with reference to their own MHC profile, female sticklebacks preferred to mate with males sharing an intermediate MHC diversity. In addition, males with a specific MHC haplotype were bigger and better at fighting a common parasite ( Gyrodactylus sp.). This translated directly into Darwinian fitness since fish harbouring this specific MHC haplotype were more likely to be chosen and had a higher reproductive output. We conclude that females also based their mating decision on a specific MHC haplotype conferring resistance against a common parasite. This identifies and supports 'good genes'. We argue that such an interaction between host and parasite driving assortative mating is not only a prerequisite for negative frequency-dependent selection — a potential mechanism to explain the maintenance of MHC polymorphism, but also potentially speciation. 相似文献
103.
C. I. ULLRICH S. PIKE F. I. BELEID EL-MOSHATY S. LENZ P. POPHAM A. J. NOVACKY 《Plant, cell & environment》1991,14(4):383-390
Abstract. In leaves of three different cultivars of cowpeas ( Vigna unguiculata ), the fungal toxin fusi-coccin (FC) induced a plasmalemma depolarization from -175 to -100mV, a value slightly below the N2 -determined diffusion potential in the dark, and to a lesser extent in the light. The depolarization was preceded by the usual initial membrane hyperpolarization (up to 18mV). The membrane depolarization was accompanied by considerable K+ efflux and extracellular alkalinization. Primary and secondary leaves as well as stem tissue of plants, grown under long-day conditions or in the dark responded similarly. Dark O2 uptake in leaves and hypocotyls was stimulated by FC by up to 77 and 87%, respectively. In contrast, FC caused a typical Em hyperpolarization, K+ influx, extracellular acidification and smaller stimulation of respiration (50%) in leaves of other legumes such as mungbean ( Vigna radiata ), or soybean ( Glycine max ). Leaves of navy beans ( Phaseolus vulgaris ) revealed an intermediate response to FC. The unusual effect of FC in Vigna might be related to the production of toxic catabolites during degradation and fermentation of storage products necessary to meet the strong energy requirement of the pm-H+ ATPase. 相似文献
104.
105.
Marieke Biegstraaten Ivo N van Schaik Wouter Wieling Frits A Wijburg Carla EM Hollak 《BMC neurology》2010,10(1):38