Isolation by distance across the Hawaiian Archipelago in the reef-building coral Porites lobata

There is an ongoing debate on the scale of pelagic larval dispersal in promoting connectivity among populations of shallow, benthic marine organisms. The linearly arranged Hawaiian Islands are uniquely suited to study scales of population connectivity and have been used extensively as a natural laboratory in terrestrial systems. Here, we focus on Hawaiian populations of the lobe coral Porites lobata, an ecosystem engineer of shallow reefs throughout the Pacific. Patterns of recent gene flow and population structure in P. lobata samples (n = 318) from two regions, the Hawaiian Islands (n = 10 sites) and from their nearest neighbour Johnston Atoll, were analysed with nine microsatellite loci. Despite its massive growth form, ～ 6% of the samples from both regions were the product of asexual reproduction via fragmentation. Cluster analysis and measures of genetic differentiation indicated that P. lobata from the Hawaiian Islands are strongly isolated from those on Johnston Atoll (F(ST) = 0.311; P < 0.001), with the descendants of recent migrants (n = 6) being clearly identifiable. Within the Hawaiian Islands, P. lobata conforms to a pattern of isolation by distance. Here, over 37% (P = 0.001) of the variation in genetic distance was explained by geographical distance. This pattern indicates that while the majority of ongoing gene flow in Hawaiian P. lobata occurs among geographically proximate reefs, inter-island distances are insufficient to generate strong population structure across the archipelago.     

Positive flow dependence in the initial colonization of a fouling community: results from in situ water current manipulations

During late winter/early spring (1992–1993), a series of 12 tapered channels were placed subtidally in a Long Island, New York (U.S.A) estuary to examine total fouling community development. Rather than relying upon flow-dependent correlations among spatially segregated sites, these channels directly accelerated or decelerated the existing tidal currents ± 50% (ambient flow speeds ranged from < 2 to > 50 cm/s). In response to experimentally manipulated water flows over five months, the arborescent hydroid Obelia longissima Pallas (1766) accumulated onto Tygon tubing in direct proportion to mean free-stream flow speed, whereas barnacle (Balanus eburneus Gould) initial settlement and cumulative recruitment along plywood ceilings increased three-fold and five-fold, respectively, with a long-term doubling of water speed. These positive flow-dependent results directly contrast those from previous experiments in the same channel apparatus which failed to document any flow enhancement on the growth of suspension-feeding bivalves.     

Population genetics of colonizing success of weedy rye in Northern California

Summary Genetic parameters of 11 weedy rye populations located in California's northern mountain area and the adjoining Oregon border were compared with those of the putative parents, wild species Secale montamim and cultivated rye S. cereale. All weedy populations exhibited high levels of genetic variation as determined by isozyme analysis. On average, 44% of the isozyme loci were polymorphic, total genetic diversity was 0.30; and number of alleles per locus was 1.65. High genetic identities, averaging 0.994 ± 0.005 between populations, indicated that little genetic differentiation has occurred among these weedy populations since the initial colonization. Lack of population differentiation could be attributed to a wind-pollinated, self-incompatible breeding system resulting in extensive gene flow among weedy populations, and between weedy populations and local cultivars of rye. Multilocus outcrossing rates of weedy populations ranged from 0.86 to 0.97. The estimated levels of gene flow using the private-alleles method were high among weedy populations, and between cv Merced and weedy populations, with estimated Nm values of 14.50 and 8.21, respectively. The colonizing success of weedy rye is discussed and a strategy for its conservation recommended.     

The influence of stream flow reduction on the energetics of endemic Hawaiian torrenticolous aquatic insects, <Emphasis Type="Italic">Telmatogeton</Emphasis> Schiner and <Emphasis Type="Italic">Procanace</Emphasis> Hendel

Tropical island stream ecosystems continue to be threatened by increasing anthropogenic demands for freshwater, with many streams dammed or diverted. Stream flow amendments can have substantial effects on aquatic insect populations of tropical archipelagoes. In Hawaiian streams, an endemic Diptera community of the following genera dominates cascades and other torrential habitats: Telmatogeton Schiner (Chironomidae), Procanace Hendel (Canacidae), Scatella Robineau-Desvoidy (Ephydridae). Larval densities, standing stock biomass (SSB, as ash-free dry mass [AFDM]), and monthly secondary production of Telmatogeton and Procanace were measured during two summers of significantly different stream discharge in Iao Valley, Maui, Hawaii. Very few Scatella larvae were collected (<20 larvae for both years combined), so they were omitted from subsequent analyses. Stream discharge decreased approximately 40% from 1994 to 1995, providing a ‘natural test’ of the effects of reduced stream flow on these torrenticolous populations between two years. Combined Telmatogeton and Procanace SSB (total torrential community SSB) was 3176 and 1683 mg AFDM m⁻² for 1994 and 1995, respectively, with Telmatogeton accounting for >95% in both years due to significantly larger body size and high density. The SSB of Telmatogeton significantly decreased from 3138 to 1622 mg AFDM m⁻² from 1994 to 1995 but increased for Procanace (37.6–60.9 mg AFDM m⁻², respectively). Total torrential community secondary production was 31% lower in 1994 (12,833 mg AFDM m⁻² mo⁻¹) compared to 1995 (8855 mg AFDM m⁻² mo⁻¹), reflecting the Telmatogeton proportion of total community production (99%); however, Procanace production increased by 40%. Monthly P/B ratios indicated that biomass turnover was generally high and increased for Telmatogeton from 1994 (3.8) to 1995 (5.1), whereas it remained lower and did not change between years for Procanace (1.7). A natural drought of the Iao Stream valley was associated with structural and functional changes in two endemic aquatic insects; these results are a conservative indication of permanent stream flow reductions from anthropogenic withdrawal (e.g., dams and diversions).     

巨大芽胞杆菌luxAB标记菌株的根际定殖研究

通过三亲本杂交方法成功地用发光酶基因luxAB标记巨大芽胞杆菌ATCC14581,所获得的标记菌株ATCC14581-L在不同的条件下能稳定发光.将该标记菌株制成微生物接种剂,并利用土壤微缩系统将其接种小麦进一步研究它在小麦根际的定殖动态和散布规律.结果发现,ATCC14581-L在灭菌土壤中的定殖水平高于不灭菌土壤,在垂直方向上主要的定殖在0～7cm根段间,且随深度增加而降低.ATCC14581-L在小麦种后第7d之前就已达到最高定殖水平,在初始接种量为3.40×107cfu/g根情况下,第7d时灭菌土壤处理的根际菌数为2.54×105cfu/g根,而不灭菌土壤的根际菌数为8.87×104cfu/g根;随着时间的增长,定殖数量明显降低.     

Fine-scale population genetic structure of a wildlife disease vector: the southern house mosquito on the island of Hawaii

The southern house mosquito, Culex quinquefasciatus, is a widespread tropical and subtropical disease vector. In the Hawaiian Islands, where it was introduced accidentally almost two centuries ago, it is considered the primary vector of avian malaria and pox. Avian malaria in particular has contributed to the extinction and endangerment of Hawaii's native avifauna, and has altered the altitudinal distribution of native bird populations. We examined the population genetic structure of Cx. quinquefasciatus on the island of Hawaii at a smaller spatial scale than has previously been attempted, with particular emphasis on the effects of elevation on population genetic structure. We found significant genetic differentiation among populations and patterns of isolation by distance within the island. Elevation per se did not have a limiting effect on gene flow; however, there was significantly lower genetic diversity among populations at mid elevations compared to those at low elevations. A recent sample taken from just above the predicted upper altitudinal distribution of Cx. quinquefasciatus on the island of Hawaii was confirmed as being a temporary summer population and appeared to consist of individuals from more than one source population. Our results indicate effects of elevation gradients on genetic structure that are consistent with known effects of elevation on population dynamics of this disease vector.     

THE MICRO AND MACRO IN BODY SIZE EVOLUTION

The diversity of body sizes of organisms has traditionally been explained in terms of microevolutionary processes: natural selection owing to differential fitness of individual organisms, or to macroevolutionary processes: species selection owing to the differential proliferation of phylogenetic lineages. Data for terrestrial mammals and birds indicate that even on a logarithmic scale frequency distributions of body mass among species are significantly skewed towards larger sizes. We used simulation models to evaluate the extent to which macro- and microevolutionary processes are sufficient to explain these distributions. Simulations of a purely cladogenetic process with no bias in extinction or speciation rates for different body sizes did not produce skewed log body mass distributions. Simulations that included size-biased extinction rates, especially those that incorporated anagenetic size change within species between speciation and extinction events, regularly produced skewed distributions. We conclude that although cladogenetic processes probably play a significant role in body size evolution, there must also be a significant anagenetic component. The regular variation in the form of mammalian body size distributions among different-sized islands and continents suggests that environmental conditions, operating through both macro- and microevolutionary processes, determine to a large extent the diversification of body sizes within faunas. Macroevolution is not decoupled from microevolution.     

A Bayesian Approach to Inferring the Phylogenetic Structure of Communities from Metagenomic Data

Metagenomics provides a powerful new tool set for investigating evolutionary interactions with the environment. However, an absence of model-based statistical methods means that researchers are often not able to make full use of this complex information. We present a Bayesian method for inferring the phylogenetic relationship among related organisms found within metagenomic samples. Our approach exploits variation in the frequency of taxa among samples to simultaneously infer each lineage haplotype, the phylogenetic tree connecting them, and their frequency within each sample. Applications of the algorithm to simulated data show that our method can recover a substantial fraction of the phylogenetic structure even in the presence of high rates of migration among sample sites. We provide examples of the method applied to data from green sulfur bacteria recovered from an Antarctic lake, plastids from mixed Plasmodium falciparum infections, and virulent Neisseria meningitidis samples.     

Phenotypic switching and its implications for the pathogenesis of Cryptococcus neoformans

Phenotypic switching has been described in several strains of Cryptococcus neoformans. It occurs in vivo during chronic infection and is associated with differential gene expression and changes in virulence. The switch involves changes in the polysaccharide capsule and cell wall that affect the yeast's ability to resist phagocytosis. In addition, the phenotypic switch variants elicit qualitatively different inflammatory responses in the host. The host's immune response ultimately affects selection of the switch variants in animal models of chronic cryptococcosis. The biological relevance of phenotypic switching is demonstrated in several murine infection models and further underlines the importance of phenotypic switching in the setting of human disease. This includes the association of switching and poor outcome in chronic infection, the ability of the mucoid variant of strain RC-2 (RC-2 MC) but not the smooth variant (RC-2 SM) to promote increased intracranial pressure in a rat model, and lastly the observation that antifungal interventions can promote the selection of more virulent switch variants during chronic murine infection.     

Microevolutionary dynamics of a community of Drosophilids

The microevolutionary dynamics of a community of Drosophilids has been analysed in a western-Mediterranean locality (Bordils, NE of Spain) by comparing the daily and seasonal activities of the nine most abundant Drosophila species: D. subobscura , D. melanogaster , D. simulans , D. immigrans , D. phalerata , D. testacea , D. cameraria , D. hydei and D. picta collected during two periods widely distant in time. The resemblance between samples obtained in different months (seasonal component) has been determined and a clear-cut clustering of the collections according to the season is observed. A possible relationship between the environmental variables temperature and humidity, and the frequencies of the most abundant species in each seasonal cluster has been analysed by a correspondence analysis. This study allows to characterize each species according to its activity in definite intervals of temperature and humidity. Finally, daily and monthly activity patterns of the different species have been compared and found to be equivalent in the first and second periods. The results obtained allow the characterization of the species according to the environmental variables.     

Colonización por Pneumocystis jirovecii en mujeres gestantes y recién nacidos en Lima,Perú

BackgroundPneumocystis jirovecii primary infection occurs asymptomatically before 6 months of age, suggesting that the infection is acquired very early in life. Furthermore, Pneumocystis pneumonia has been described in newborns, which emphasizes the importance of studying Pneumocystis colonization in mother-infant pairs.AimsTo evaluate the prevalence of Pneumocystis colonization among pregnant women and to determine the potential transplacental transmission.MethodsA cross-sectional study was carried out on HIV-negative women over 18 years-old, and 37 or more weeks of pregnancy attending Hospital Cayetano Heredia Maternity unit during 2016-2017. Clinical and demographical information was collected on them and their newborns. Oropharyngeal washes, nasal swabs, and placenta samples were collected from women, as well as a nasopharyngeal aspirate and nasal swab from newborns. All respiratory samples were analysed by nested-PCR for the detection of Pneumocystis. Placenta samples from women with a positive PCR result in their respiratory samples were also analysed by nested-PCR.ResultsOf the 92 pregnant women included, five of them (5.43%) were colonized by Pneumocystis. Pneumocystis DNA was not found in any of the 87 available newborn samples or in the placentas of the five women who had a positive result by PCR in their upper respiratory samples.ConclusionsIt was found that 5.43% of the pregnant women were colonized by Pneumocystis, there was no evidence of any role of this colonization in the transmission to their newborns, since none of them tested positive for Pneumocystis.     

Qualitative finger dermatoglyphics of Venezuelan Yukpa natives

This study deals with the incidence of finger pattern types in five subtribes of Yukpa natives from Sierra de Perijá (State of Zulia —Venezuela). The frequencies of several pattern types vary to a great extent between subtribes with statistically significant difference in most of the cases. The largest differences were found between Pariri and other subtribes in both male and female series, as it occurs when other dermatoglyphic features (quantitative) are considered (Diaz Ungria and Martin, 1984, in press). The internal breaking-up of the Yukpa subtribe due to the microevolutionary process supports the results presented here.     

微进化对阿萨希毛孢子菌与小鼠巨噬细胞RAW264.7相互作用的影响

目的研究微进化对阿萨希毛孢子菌(T.asahii)与巨噬细胞RAW264.7相互作用的影响。方法将微进化前后的T.asahii与RAW264.7细胞共培养,检测RAW264.7对两株菌的吞噬和杀伤能力以及两株菌对RAW264.7产生的细胞毒性的差异,同时分析RAW264.7自身细胞因子分泌情况的变化。结果巨噬细胞对原代菌株(TO)的吞噬能力以及杀伤率均明显高于微进化株(TEVO);TO菌株对巨噬细胞的细胞毒性要强于TEVO;当巨噬细胞与菌株按1∶3或1∶6共培养24 h时,与TO共培养的巨噬细胞TNF-α和IL-6的分泌量要高于TEVO组,而按1∶9共培养时TEVO组细胞因子的分泌量却高于TO组。结论微进化后的TEVO菌株与巨噬细胞的相互作用明显弱于原代株TO,这也为TEVO菌株在宿主体内长期共存提供了良好的基础。     

Japan and human evolutionary research

The trends in evolutionary research in Japan have largely changed through the introduction of new methodologies such as molecular genetics and multivariate statistics since the 1960’s. The development of ecology and primatology brought another new wave into fields of physical anthropology. This paper reviews briefly general trends in anthropological research now on-going in Japan. Microevolutionary studies of the Japanese and neighboring populations which have a long history in Japan will be reviewed in more detail.