Attenuation of seizure in P77PMC rats with an HSV-vector expressing IL-1ra in brain

Ｅｐｉｌｅｐｓｙｉｓｏｎｅｏｆｔｈｅｃｏｍｍｏｎｄｉｓｅａｓｅｓｄｕｒｉｎｇｃｈｉｌｄｈｏｏｄｉｎｃｌｉｎｉｃａｌｐｒａｃｔｉｃｅ.Ｂｅｃａｕｓｅｏｆｃｏｍｐｌｅｘｅｔｉｏｌｏｇｙ,ｍｏｌｅｃｕｌａｒｍｅｃｈａｎｉｓｍｓｏｆｅｐｉｌｅｐｔｏｇｅｎｅｓｉｓａｒｅｎｏｔｆｕｌｌｙｃｌｅａｒ.Ａｓｗｅｋｎｏｗｅｐｉｌｅｐｓｙｉｓｃａｕｓｅｄｂｙｉｍｂａｌａｎｃｅｂｅｔｗｅｅｎｅｘｃｉｔａｔｉｏｎａｎｄｓｕｐｐｒｅｓｓｉｏｎｏｆｔｈｅｂｒａｉｎ.Ｉｔｈａｓｂｅｅｎｓｈｏｗｎｉｎｈｕｍａｎａｎｄａｎｉｍａｌｍ…     

Isolation and characterization of five rice telomere-associated sequences

Ｔｅｌｏｍｅｒｅｉｓｔｈｅｅｓｓｅｎｔｉａｌｇｅｎｅｔｉｃｌｏｃｕｓａｔｔｈｅｅｎｄｓｏｆａｌｌｅｕｋａｒｙｏｔｉｃｃｈｒｏｍｏｓｏｍｅｓ.ＴｈｅｙｗｅｒｅｐｒｏｐｏｓｅｄｔｏｃａｐｃｈｒｏｍｏｓｏｍｅｓｐｒｅｖｅｎｔｉｎｇｔｈｅｅｎｄｔｏｅｎｄｆｕｓｉｏｎｓｂｅｔｗｅｅｎｂｒｏｋｅｎｅｎｄｓａｎｄｃｏｎｔｉｎｕａｌｔｅｒｍｉｎａｌＤＮＡｌｏｓｓｄｕｒｉｎｇｒｅｐｌｉｃａｔｉｏｎ.Ｔｈｅｙａｌｓｏｈａｖｅｉｎｆｌｕｅｎｃｅｓｏｎｍｅｍｂｒａｎｅｃｈｒｏｍｏｓｏｍｅｉｎｔｅｒａｃｔｉｏｎａｎｄｔｈｅ…     

生态学的精神价值

生态学的精神价值陈清硕（江苏农学院扬州２２５００１）ＳｐｉｒｉｔｕａｌＶａｌｕｅｏｆＥｃｏｌｏｇｙ￥．ＣｈｅｎＱｉｎｇｓｈｕｏ（ＪｉａｎｇｓｕＡｇｒｉｃｕｌｔｕｒａｌＣｏｌｌｅｇｅ,Ｙａｎｇｚｈｏｕ２２５００１）：ＣｈｉｎｅｓｅＪｏｕｒｎａｌｏｆＥｃｏｌｏｇｙ,１９９３,１２（３）：６８－７２．Ｔｈｉｓｐａｐｅｒｄｅｓｃｒｉｂｅｓｔｈｅｆｕｎｃｔｉｏｎｓｏｆｅｃｏｌｏｇｙｉｎｔｈｅｐｒｏｇｒｅｓｓｏｆｓｏｃｉａｌｉｄｅｏｌｏｇｙａｎｄｃｉｖｉｌｉｚａｔｉｏｎ．Ｅｃｏｌｏｇｙｈｅｌｐｓｂｒｉｎｇｉｎｔｏｂｅｉｎｇｔｈｅｃｏｎｓｔｒｕｃｔｉｏｎｏｆａｓｃｉｅｎｔｉｆｉｃｗｏｒｌｄｏｕｔｌｏｏｋａｎｄｉｎｃｒｅａｓｅｔｈｅｅｃｏｌｏｇｉｃａｌｃｏｎｓｃｉｏｕｓ－ｎｅｓｓｏｆｍａｎｋｉｎｄ．Ｉｔａｌｓｏｓｕｐｐｌｉｅｓａｔｏｔａｌｄｅｖｅｌｏｐｍｅｎｔａｌｐｏｉｎｔｏｆｖｉｅｗｆｏｒｔｈｅｓｏｃｉｅｔｙａｎｄｐｒｏｖｉｄｅｓａｇｒｅａｔａｅｓｔｈｅｔｉｃｖａｌｕｅ．Ｔｈｅｓｐｉｒｉｔｕａｌｖａｌｕｅｏｆｅｃｏｌｏｇｙｓｈｏｕｌｄｎｅｖｅｒｂｅｎｅｇｌｅｃｔｅｄ．Ｋｅｙｗｏｒｄｓ：ｓｏｃｉａｌｅｃｏｌｏｇｙ,ｅｃｏｌ     

Three-dimensional Morphometric Analyses of Hominoid Lower Molars from Yuanmou in Yunnan Province,China

1　ＩｎｔｒｏｄｕｃｔｉｏｎＡｍｏｎｇｔｈｅｆｏｕｒＭｉｏｃｅｎｅｈｏｍｉｎｏｉｄｓｉｔｅｓｏｆＫａｉｙｕａｎ ,Ｌｕｆｅｎｇ ,ＹｕａｎｍｏｕａｎｄＢａｏｓｈａｎｉｎＹｕｎｎａｎＰｒｏｖｉｎｃｅｏｆＣｈｉｎａ ,ＬｕｆｅｎｇａｎｄＹｕａｎｍｏｕａｒｅｔｈｅｒｉｃｈｅｓｔｆｏｓｓｉｌｓｉｔｅｓ .Ｓｉｎｃｅｉｔｓｆｉｒｓｔｄｉｓｃｏｖｅｒｙｉｎ 1 975,ｍａｎｙｃｏｌｌｅａｇｕｅｓａｒｏｕｎｄｔｈｅｗｏｒｌｄｈａｖｅｂｅｅｎｉｎｖｏｌｖｅｄｉｎｔｈｅｓｔｕｄｙｏｆＬｕｆｅｎｇｐｉｔｈｅｃｕｓｆｏｓｓｉｌｓ .Ｈｏｗｅｖｅｒ,ｎｏａｇｒｅｅｍｅｎｔｈａｓｂｅｅｎｒｅａｃｈｅｄｏｎｔｈｅｒｅｌａｔｉｏｎｓｈｉｐｏｆＬｕｆｅｎｇｐｉｔｈｅｃｕｓｔｏｏｔｈｅｒＭｉｏｃｅｎｅｈｏｍｉｎｏｉｄｓｆｏｕｎｄａｒｏｕｎｄｔｈｅｗｏｒｌｄｏｒｏｎｉｔｓｐｈｙｌｏｇｅｎｙ .ＷｕＲｕｋａｎｇｂｅｌｉｅｖｅｓｔｈａｔｔｈｅｒｅａｒｅａｓｅｒｉｅｓｏｆｍｏｒｐｈｏｌｏｇｉｃａｌｄｉｆ ｆｅｒｅｎｃｅｓｂｅｔｗｅｅｎＬｕｆｅｎｇｐｉｔｈｅｃｕｓａｎｄｔｈｅＳｉｖａｐｉｔｈｅｃｕｓｓｐｅｃｉｍｅｎｓｆｏｕｎｄｉｎＴｕｒｋｅｙａｎｄＰ...     

陆生脊椎动物生态学研究的过去,现在和将来

陆生脊椎动物生态学研究的过去、现在和将来（前苏联科学院动物进化形态学与生态学研究所,莫斯科）Ｐａｓｔ,ＰｒｅｓｅｎｔａｎｄＦｕｔｕｒｅｏｆＥｃｏｌｏｇｉｃａｌＲｅｓｅａｒｃｈｏｎＴｅｒｒｃｓｔｒｉａｌＶｃｔｅｂｒａｔｃｓ￥．（ＩｎｓｔｉｔｕｔｅｏｆＡｎｉｍａｌＥｖｏｌｕｔｉｏｎａｒｙＭｏｒｐｈｏｌｏｇｙａｎｄＥｃｏｌｏｇｙ,ｔｈｅＦｏｒｍｅｒＡｃａｄｅｍｙｏｆＳｃｌｅｎｃｅｓｏｆＳｏｖｉｅｔＵｎｉｏｎ）．ＣｈｉｎｅｓｅＪｏｕｒｎａｌｏｆＥｃｏｌｏｇｙ,１９９３,１２（４）：６６－７１。Ｔｈｉｓｐａｐｅｒｄｅｓｃｒｉｂｅｓｔｈｅｍａｉｎｓｔａｇｅｓ,ｄｉｒｅｃｔｉｏｎｓａｎｄｉｔｅｍｓｏｆｅｃｏｌｏｇｉｃａｌｒｅｓｅａｒｃｈｉｎｔｈｅｆｏｒｍｅｒｓｏｖｉｅｔＵ－ｎｉｏｎ．ＥｃｏｌｏｇｉｃａｌｒｅｓｅａｒｃｈｉｎｔｈｅｃｏｕｎｔｒｙｗａｓｒｅｓｔｒｏｄｅｄｂｙｍａｎｙｓｕＵｅｃｔｉｖｅａｎｄｏＵｅｃｔｉｖｅｆａｃｔｏｒｓａｎｄｓｔｉｌｌｌａｇｓｂｅｈｉｎｄｔｈｅｗｏｒｌｄｌｅｖｅｌｉｎｍａｎｙａｓｐｅｃｔｓｓｕｃｈａｓｐｏｐｕｌａｔｉｏｎｄｙｎａｍｉｃｓｔｈｅｏｒｙ,ｃｏｍｍｕｎｉｔｙｒｅｓｅａｒｃｈ,ｅｃｏ－     

Production and characterization of a human single-chain Fv to collagenase IV

Ｉｎｖａｓｉｏｎａｎｄｍｅｔａｓｔａｓｉｓａｒｅｔｈｅｍｏｓｔｉｍｐｏｒｔａｎｔｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｍａｌｉｇｎａｎｔｔｕｍｏｒ.ＴｈｅｏｖｅｒｅｘｐｒｅｓｓｉｏｎａｎｄｉｎｃｒｅａｓｉｎｇａｃｔｉｖｉｔｙｏｆｃｏｌｌａｇｅｎａｓｅＩＶｉｎｔｕｍｏｒｔｉｓｓｕｅｓｈａｖｅｂｅｅｎｃｏｎｓｉｄｅｒｅｄａｓｏｎｅｏｆｔｈｅｍａｉｎｆａｃｔｏｒｓｉｎｖｏｌｖｅｄｉｎｔｕｍｏｒｍｅｔａｓｔａｓｉｓ[1].ＩｔｈａｓｂｅｅｎｔｈｏｕｇｈｔｔｈａｔｔｈｅｉｎｃｒｅａｓｉｎｇｃｏｌｌａｇｅｎａｓｅＩ…     

Expression and regulation of hFIX minigene and cDNA driven by β-casein gene in mouse mammary gland

Ｉｎｒｅｃｅｎｔｙｅａｒｓ,ｔｈｅｒｅｓｅａｒｃｈｏｆｕｓｉｎｇｍａｍｍａｒｙｇｌａｎｄｂｉｏｒｅａｃｔｏｒｓｔｏｐｒｏｄｕｃｅｌａｒｇｅａｍｏｕｎｔｓｏｆｈｕｍａｎｐｈａｒｍａｃｅｕｔｉｃａｌｐｒｏｔｅｉｎｓｄｒａｗｍｏｒｅａｎｄｍｏｒｅａｔｔｅｎｔｉｏｎｗｉｔｈｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｔｒａｎｓｇｅｎｉｃｔｅｃｈｎｉｑｕｅｓ.Ｔｒａｎｓｇｅｎｅｅｘｐｒｅｓｓｉｏｎｉｎｍｉｌｋｏｆｆｅｒｓｓｅｖｅｒａｌｐｏｔｅｎｔｉａｌａｄｖａｎｔａｇｅｓ:ｐｒｏｔｅｉｎｓｓｅｃｒｅｔｅｄｉｎｍｉｌｋ,ｗ…     

Mechanism of selective stabilization of extrinsic polypeptides in PSII particles by glycinebetaine

Ｔｈｒｅｅｅｘｔｒｉｎｓｉｃｐｏｌｙｐｅｐｔｉｄｅｓ,ｗｈｉｃｈａｒｅｌｏｃａｔｅｄｏｎｔｈｅｉｎｎｅｒｓｕｒｆａｃｅｏｆｔｈｙｌａｋｏｉｄｍｅｍｂｒａｎｅ,ｐｌａｙｅｓｓｅｎｔｉａｌｒｏｌｅｓｉｎｍａｉｎｔａｉｎｉｎｇｔｈｅｐｈｏｔｏｓｙｎｔｈｅｔｉｃｅｖｏｌｕｔｉｏｎｏｆｏｘｙｇｅｎ.Ｔｈｅｙａｒｅｇｅｎｅｒａｌｌｙｒｅｃｏｇｎｉｚｅｄａｓｌｉａｂｌｅｃｏｍｐｏｎｅｎｔｓｏｆｔｈｅｐｈｏｔｏｓｙｎｔｈｅｔｉｃａｐｐａｒａｔｕｓ,ａｎｄｃａｎｂｅｒｅｌｅａｓｅｄｂｙａｖａｒｉｅｔｙｏｆｐｈｙｓｉｃ…     

Molecular evidence on maize specific DNA fragment transferred into wheat through sexual hybridization

Ｗｈｅａｔｈａｐｌｏｉｄｃａｎｂｅｐｒｏｄｕｃｅｄｂｙｅｍｂｒｙｏｒｅｓｃｕｅａｆｔｅｒｗｈｅａｔａｎｄｍａｉｚｅｃｒｏｓｓｓｉｎｃｅｔｈｅｍａｉｚｅｃｈｒｏｍｏｓｏｍｅｓａｒｅｒａｐｉｄｌｙｅｌｉｍｉｎａｔｅｄｆｒｏｍｔｈｅｅａｒｌｙｚｙｇｏｔｉｃｅｍｂｒｙｏｓ[1,2].Ｕｓｕａｌｌｙ2%—5%ｏｆｗｈｅａｔｄｏｕｂｌｅｄｈａｐｌｏｉｄｓｈｏｗｓａｇｒｏｎｏｍｉｃｖａｒｉａｔｉｏｎｓ,ｂｕｔｎｏｏｂｖｉｏｕｓｍｏｒｐｈｏｌｏｇｉｃａｌｔｒａｉｔｆｒｏｍｍａｉｚｅｉｓｏｂｓｅｒｖｅｄ.Ｔｈｅｙｗｅｒｅｃｏ…     

Cloning of α-amylase gene from Schwanniomyces occidentalis and expression in Saccharomyces cerevisiae

Ａｎｏｒｇａｎｉｓｍ,Ｓ.ｃｅｒｅｖｉｓｉａｅｗｉｄｅｌｙｕｓｅｄｉｎｂｒｅｗｉｎｇ,ｂａｋｉｎｇａｎｄｉｎｅｔｈａｎｏｌｐｒｏｄｕｃｔｉｏｎｐｒｏｃｅｓｓｅｓｉｓｎｏｔａｂｌｅｔｏｈｙｄｒｏｌｙｓｅｓｔａｒｃｈ.ＴｈｕｓｔｈｅｔｒａｄｉｔｉｏｎａｌｃｏｎｖｅｒｓｉｏｎｏｆｓｔａｒｃｈｉｎｔｏｅｔｈａｎｏｌａｎｄＣＯ2ｄｅｐｅｎｄｓｏｎｔｈｅａｄｄｉｔｉｏｎｏｆｔｈｅｅｎｚｙｍｅｓｐｒｉｏｒｔｏｆｅｒｍｅｎｔａｔｉｏｎ,ｗｈｉｃｈｌｅａｄｓｔｏｌｉｑｕｉｆｉｃａｔｉｏｎａｎｄｓａｃｃｈａｒｉｆｉｃａｔ…     

Cross-species amplification of 92 microsatellites of Medicago truncatula

Medicago species are important genetic sources for forage crops and nitrogen sources for various ecosystems. The ongoing genome sequencing of the model legume, Medicago truncatula, provides a wealth of genetic markers potentially useful for characterizing the population genetic structure and evolutionary history, and the potential of the wild Medicago species. Here we tested the PCR amplification of 92 microsatellites developed from M. truncatula in six other Medicago species, and found that the cross-species transferability, ranging from 53.26% to 61.96%, is comparable with those reported in other angiosperm genera. This article thus reports a number of microsatellites that are potentially useful for large-scale ecological and evolutionary genetic studies of wild Medicago species.     

Can common species provide valuable information for conservation?

To demonstrate the importance of genetic data for multispecies conservation approaches, we examined the distribution of genetic variation across the range of the mountain whitefish (Prosopium williamsoni) at microsatellite and allozyme loci. The mountain whitefish is a common species that is particularly well suited for accurately revealing historical patterns of genetic structure and differs markedly from previously studied species in habitat requirements and life history characteristics. As such, comparing the population genetic structure of other native fishes to similar data from mountain whitefish could inform management and conservation strategies. Genetic variation for mountain whitefish was hierarchically distributed for both allozymes and microsatellites. We found evidence for a total of five major genetically differentiated assemblages and we observed subdivision among populations within assemblages that generally corresponded to major river basins. We observed little genetic differentiation within major river basins. Geographic patterns of genetic differentiation for mountain whitefish were concordant with other native species in several circumstances, providing information for the designation of conservation units that reflect concordant genetic differentiation of multiple species. Differences in genetic patterns between mountain whitefish and other native fishes reflect either differences in evolutionary histories of the species considered or differences in aspects of their ecology and life history. In addition, mountain whitefish populations appear to exchange genes over a much larger geographic scale than co-occurring salmonids and are likely to be affected differently by disturbances such as habitat fragmentation.     

Low genetic diversity but local genetic differentiation in endemic Minasia (Asteraceae) species from Brazil

Espinhaço Range is a Brazilian chain of mountains, extremely rich in endemic species. Minasia has six species, all perennial herbs endemic to this range. Twenty-two populations were sampled from all Minasia species and assayed for allozyme variation. The species showed low genetic variation, compatible with the expectation for endemics. Genetic identities in Serra do Cipó and Diamantina were high, even between populations of different species. On the other hand M. cabralensis, from Serra do Cabral, was more differentiated from the other species. We also observed a marked genetic differentiation within M. cabralensis. Most strikingly, two close populations of this species showed very different allele frequencies. Our findings highlight the importance of local differentiation in campos rupestres. The observed genetic structure indicates that substantial portions of genetic diversity could be lost with the extinction of only one population, which is especially threatening considering the already low genetic diversity.     

Delimiting species without monophyletic gene trees

Genetic data are frequently used to delimit species, where species status is determined on the basis of an exclusivity criterium, such as reciprocal monophyly. Not only are there numerous empirical examples of incongruence between the boundaries inferred from such data compared to other sources like morphology -- especially with recently derived species, but population genetic theory also clearly shows that an inevitable bias in species status results because genetic thresholds do not explicitly take into account how the timing of speciation influences patterns of genetic differentiation. This study represents a fundamental shift in how genetic data might be used to delimit species. Rather than equating gene trees with a species tree or basing species status on some genetic threshold, the relationship between the gene trees and the species history is modeled probabilistically. Here we show that the same theory that is used to calculate the probability of reciprocal monophyly can also be used to delimit species despite widespread incomplete lineage sorting. The results from a preliminary simulation study suggest that very recently derived species can be accurately identified long before the requisite time for reciprocal monophyly to be achieved following speciation. The study also indicates the importance of sampling, both with regards to loci and individuals. Withstanding a thorough investigation into the conditions under which the coalescent-based approach will be effective, namely how the timing of divergence relative to the effective population size of species affects accurate species delimitation, the results are nevertheless consistent with other recent studies (aimed at inferring species relationships), showing that despite the lack of monophyletic gene trees, a signal of species divergence persists and can be extracted. Using an explicit model-based approach also avoids two primary problems with species delimitation that result when genetic thresholds are applied with genetic data -- the inherent biases in species detection arising from when and how speciation occurred, and failure to take into account the high stochastic variance of genetic processes. Both the utility and sensitivities of the coalescent-based approach outlined here are discussed; most notably, a model-based approach is essential for determining whether incompletely sorted gene lineages are (or are not) consistent with separate species lineages, and such inferences require accurate model parameterization (i.e., a range of realistic effective population sizes relative to potential times of divergence for the purported species). It is the goal (and motivation of this study) that genetic data might be used effectively as a source of complementation to other sources of data for diagnosing species, as opposed to the exclusion of other evidence for species delimitation, which will require an explicit consideration of the effects of the temporal dynamic of lineage splitting on genetic data.     

Very low additive genetic variance and evolutionary potential in multiple populations of two rainforest Drosophila species

Most quantitative traits are thought to exhibit high levels of genetic variance and evolutionary potential. However, this conclusion may be biased by a lack of studies on nonmodel organisms and may not generalize to restricted species. A recent study on a single, southern population of the rainforest-restricted Drosophila birchii failed to find significant additive genetic variance for the desiccation resistance trait; however, it is unclear whether this pattern extends to other D. birchii populations or to other rainforest species. Here we use an animal model design to show very low levels of additive genetic variance for desiccation resistance in multiple populations of two highly sensitive rainforest species of Drosophila from tropical northeastern Australia. In contrast, relatively high levels of genetic variance were found for morphological traits in all populations of the species tested. This indicates limited evolutionary potential for evolving increased desiccation resistance in these rainforest restricted species.     

Population genetic structure of two rare tree species (Colubrina oppositifolia and Alphitonia ponderosa,Rhamnaceae) from Hawaiian dry and mesic forests using random amplified polymorphic DNA markers

Hawaiian dry and mesic forests contain an increasingly rare assemblage of species due to habitat destruction, invasive alien weeds and exotic pests. Two rare Rhamnaceae species in these ecosystems, Colubrina oppositifolia and Alphitonia ponderosa, were examined using random amplified polymorphic DNA (RAPD) markers to determine the genetic structure of the populations and the amount of variation relative to other native Hawaiian species. Relative variation is lower than with other Hawaiian species, although this is probably not a consequence of genetic bottleneck. Larger populations of both species contain the highest levels of genetic diversity and smaller populations generally the least as determined by number of polymorphic loci, estimated heterozygosity, and Shannon's index of genetic diversity. Populations on separate islands were readily discernible for both species as were two populations of C. oppositifolia on Hawai'i island (North and South Kona populations). Substructure among Kaua'i subpopulations of A. ponderosa that were ecologically separated was also evident. Although population diversity is thought to have remained at predisturbance levels, population size continues to decline as recruitment is either absent or does not keep pace with senescence of mature plants. Recovery efforts must focus on control of alien species if these and other endemic dry and mesic forest species are to persist.     

Genetic continuity of brood-parasitic indigobird species

Speciation in brood-parasitic indigobirds (genus Vidua) is a consequence of behavioural imprinting in both males and females. Mimicry of host song by males and host fidelity in female egg laying result in reproductive isolation of indigobirds associated with a given host species. Colonization of new hosts and subsequent speciation require that females occasionally lay eggs in the nests of novel hosts but the same behaviour may lead to hybridization when females parasitize hosts already associated with other indigobird species. Thus, retained ancestral polymorphism and ongoing hybridization are two alternative explanations for the limited genetic differentiation among indigobird species. We tested for genetic continuity of indigobird species using mitochondrial sequences and nuclear microsatellite data. Within West Africa and southern Africa, allopatric populations of the same species are generally more similar to each other than to sympatric populations of different species. Likewise, a larger proportion of genetic variation is explained by differences between species than by differences between locations in alternative hierarchical AMOVAS, suggesting that the rate of hybridization is not high enough to homogenize sympatric populations of different species or prevent genetic differentiation between species. Broad sharing of genetic polymorphisms among species, however, suggests that some indigobird species trace to multiple host colonization events in space and time, each contributing to the formation of a single interbreeding population bound together by songs acquired from the host species.     

Fine-scale community and genetic structure are tightly linked in species-rich grasslands

Recent evidence indicates that grassland community structure and species diversity are influenced by genetic variation within species. We review what is known regarding the impact of intraspecific diversity on grassland community structure, using an ancient limestone pasture as a focal example. Two genotype-dependent effects appear to modify community structure in this system. First, the abundance of individual constituent species can depend upon the combined influence of direct genetic effects stemming from individuals within the population. Second, the outcome of localized interspecific interactions occurring within the community can depend on the genotypes of participating individuals (indicating indirect genetic effects). Only genotypic interactions are thought to be capable of allowing the long-term coexistence of both genotypes and species. We discuss the implications of these effects for the maintenance of diversity in grasslands. Next, we present new observations indicating that losses of genotypic diversity from each of two species can be predicted by the abundance of other coexisting species within experimental grassland communities. These results suggest genotype-specific responses to abundance in other coexisting species. We conclude that both direct and indirect genetic effects are likely to shape community structure and species coexistence in grasslands, implying tight linkage between fine-scale genetic and community structure.     

The population genetics of host specificity: genetic differentiation in dove lice (Insecta: Phthiraptera)

Some species of parasites occur on a wide range of hosts while others are restricted to one or a few host species. The host specificity of a parasite species is determined, in part, by its ability to disperse between host species. Dispersal limitations can be studied by exploring the genetic structure of parasite populations both within a single species of host and across multiple host species. In this study we examined the genetic structure in the mitochondrial cytochrome oxidase I (COI) gene of two genera of lice (Insecta: Phthiraptera) occurring on multiple sympatric species of doves in southern North and Central America. One genus, Columbicola, is generally less host-specific than the other, Physconelloides. For both genera we identified substantial genetic differentiation between populations of conspecific lice on different host species, generally 10-20% sequence divergence. This level of divergence is in the range of that often observed between species of these two genera. We used nested clade analysis to explore fine scale genetic structure within species of these feather lice. We found that species of Physconelloides exhibited more genetic structure, both among hosts and among geographical localities, than did species of Columbicola. In many cases, single haplotypes within species of Columbicola are distributed on multiple host species. Thus, the population genetic structure of species of Physconelloides reveals evidence of geographical differentiation on top of high host species specificity. Underlying differences in dispersal biology probably explain the differences in population genetic structure that we observed between Columbicola and Physconelloides.     

High gene flow in epiphytic ferns despite habitat loss and fragmentation

Tropical montane forests suffer from increasing fragmentation and replacement by other types of land-use such as coffee plantations. These processes are known to affect gene flow and genetic structure of plant populations. Epiphytes are particularly vulnerable because they depend on their supporting trees for their entire life-cycle. We compared population genetic structure and genetic diversity derived from AFLP markers of two epiphytic fern species differing in their ability to colonize secondary habitats. One species, Pleopeltis crassinervata, is a successful colonizer of shade trees and isolated trees whereas the other species, Polypodium rhodopleuron, is restricted to forests with anthropogenic separation leading to significant isolation between populations. By far most genetic variation was distributed within rather than among populations in both species, and a genetic admixture analysis did not reveal any clustering. Gene flow exceeded by far the benchmark of one migrant per generation to prevent genetic divergence between populations in both species. Though populations are threatened by habitat loss, long-distance dispersal is likely to support gene flow even between distant populations, which efficiently delays genetic isolation. Consequently, populations may rather be threatened by ecological consequences of habitat loss and fragmentation.