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The role of fecundity and sexual selection in the evolution of size and sexual size dimorphism in New World and Old World voles (Rodentia: Arvicolinae) 下载免费PDF全文
Evolutionary ecologists dating back to Darwin (1871) have sought to understand why males are larger than females in some species, and why females are the larger sex in others. Although the former is widespread in mammals, rodents and other small mammals usually exhibit low levels of sexual size dimorphism (SSD). Here, we investigate patterns of sexual dimorphism in 34 vole species belonging to the subfamily Arvicolinae in a phylogenetic comparative framework. We address the potential role of sexual selection and fecundity selection in creating sex differences in body size. No support was found for hyperallometric scaling of male body size to female body size. We observed a marginally significant relationship between SSD and the ratio of male to female home range size, with the latter being positively related to the level of intrasexual competition for mates. This suggests that sexual selection favours larger males. Interestingly, we also found that habitat type, but not mating system, constitutes a strong predictor of SSD. Species inhabiting open habitats – where males have extensive home ranges in order to gain access to as many females as possible – exhibit a higher mean dimorphism than species inhabiting closed habitats, where females show strong territoriality and an uniform distribution preventing males to adopt a territorial strategy for gaining copulations. Nonetheless, variation in the strength of sexual selection is not the only selective force shaping SSD in voles; we also found a positive association between female size and litter size across lineages. Assuming this relationship also exists within lineages (i.e. fecundity selection on female size), this suggests an additional role for variation in the strength of fecundity selection shaping interspecific differences in female size, and indirectly in SSD. Therefore our results suggest that different selective processes act on the sizes of males and females, but because larger size is favoured in both sexes, SSD is on average relatively small. 相似文献
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The essential oil from the rhizomes of Aframomum sceptrum (Zingiberaceae) was analyzed by GC/MS, and its major constituents were found to be β‐pinene (12.7%), caryophyllene oxide (10.0%), and cyperene (6.0%). The oil was also evaluated for antimicrobial activities, in comparison with β‐pinene, caryophyllene oxide, and the leaf essential oil of Melaleuca alternifolia (Myrtaceae). The A. sceptrum essential oil exhibited bacteriostatic activity against the Gram‐positive bacteria Bacillus subtilis, Staphylococcus epidermidis, and S. aureus, but not against Gram‐negative bacteria. Moreover, it showed mild fungicidal activity against Candida albicans and Aspergillus fumigates, and remarkable antiprotozoal activity against Trypanosoma brucei brucei (MLC of 1.51 μl/ml) and Trichomonas vaginalis (IC50 of 0.12±0.02 and MLC of 1.72 μl/ml). 相似文献
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In the brain, synchronization among cells of an assembly is a common phenomenon, and thought to be functionally relevant. Here we used an in vitro experimental model of cell assemblies, cortical cultures, combined with numerical simulations of a spiking neural network (SNN) to investigate how and why spontaneous synchronization occurs. In order to deal with excitation only, we pharmacologically blocked GABAAergic transmission using bicuculline. Synchronous events in cortical cultures tend to involve almost every cell and to display relatively constant durations. We have thus named these “network spikes” (NS). The inter-NS-intervals (INSIs) proved to be a more interesting phenomenon. In most cortical cultures NSs typically come in series or bursts (“bursts of NSs”, BNS), with short (∼1 s) INSIs and separated by long silent intervals (tens of s), which leads to bimodal INSI distributions. This suggests that a facilitating mechanism is at work, presumably short-term synaptic facilitation, as well as two fatigue mechanisms: one with a short timescale, presumably short-term synaptic depression, and another one with a longer timescale, presumably cellular adaptation. We thus incorporated these three mechanisms into the SNN, which, indeed, produced realistic BNSs. Next, we systematically varied the recurrent excitation for various adaptation timescales. Strong excitability led to frequent, quasi-periodic BNSs (CV∼0), and weak excitability led to rare BNSs, approaching a Poisson process (CV∼1). Experimental cultures appear to operate within an intermediate weakly-synchronized regime (CV∼0.5), with an adaptation timescale in the 2–8 s range, and well described by a Poisson-with-refractory-period model. Taken together, our results demonstrate that the INSI statistics are indeed informative: they allowed us to infer the mechanisms at work, and many parameters that we cannot access experimentally. 相似文献
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Paolo Maiuri Emmanuel Terriac Perrine Paul-Gilloteaux Timothée Vignaud Krista McNally James Onuffer Kurt Thorn Phuong A. Nguyen Nefeli Georgoulia Daniel Soong Asier Jayo Nina Beil Jürgen Beneke Joleen Chooi Hong Lim Chloe Pei-Ying Sim Yeh-Shiu Chu Andrea Jiménez-Dalmaroni Manuel Théry 《Current biology : CB》2013,23(1):97
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A large‐scale phylogeny of the lycophyte genus Selaginella (Selaginellaceae: Lycopodiopsida) based on plastid and nuclear loci 下载免费PDF全文
Xin‐Mao Zhou Carl J. Rothfels Liang Zhang Zhao‐Rong He Timothée Le Péchon Hai He Ngan Thi Lu Ralf Knapp David Lorence Xing‐Jin He Xin‐Fen Gao Li‐Bing Zhang 《Cladistics : the international journal of the Willi Hennig Society》2016,32(4):360-389
The lycophyte genus Selaginella alone constitutes the family Selaginellaceae, the largest of the lycophyte families. The genus is estimated to contain 700–800 species distributed on all continents except Antarctica, with highest species diversity in tropical and subtropical regions. The monophyly of Selaginella in this broad sense has rarely been doubted, whereas its intrageneric classification has been notoriously contentious. Previous molecular studies were based on very sparse sampling of Selaginella (up to 62 species) and often used DNA sequence data from one genome. In the present study, DNA sequences of one plastid (rbcL) and one nuclear (ITS) locus from 394 accessions representing approximately 200 species of Selaginella worldwide were used to infer a phylogeny using maximum likelihood, Bayesian inference and maximum parsimony methods. The study identifies strongly supported major clades and well resolves relationships among them. Major results include: (i) six deep‐level clades are discovered representing the deep splits of Selaginella; and (ii) 20 major clades representing 20 major evolutionary lineages are identified, which differ from one another in molecular, macro‐morphological, ecological and spore features, and/or geographical distribution. 相似文献
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Timothée Poisot Benjamin Baiser Jennifer A. Dunne Sonia Kéfi François Massol Nicolas Mouquet Tamara N. Romanuk Daniel B. Stouffer Spencer A. Wood Dominique Gravel 《Ecography》2016,39(4):384-390
The study of ecological networks is severely limited by 1) the difficulty to access data, 2) the lack of a standardized way to link meta‐data with interactions, and 3) the disparity of formats in which ecological networks themselves are stored and represented. To overcome these limitations, we have designed a data specification for ecological networks. We implemented a database respecting this standard, and released an R package (rmangal) allowing users to programmatically access, curate, and deposit data on ecological interactions. In this article, we show how these tools, in conjunction with other frameworks for the programmatic manipulation of open ecological data, streamlines the analysis process and improves replicability and reproducibility of ecological network studies. 相似文献
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Jasper Lodder Timothé Dena?s Marie-No?le Chobert JingHong Wan Jamel El-Benna Jean-Michel Pawlotsky Sophie Lotersztajn Fatima Teixeira-Clerc 《Autophagy》2015,11(8):1280-1292
Autophagy is a lysosomal degradation pathway of cellular components that displays antiinflammatory properties in macrophages. Macrophages are critically involved in chronic liver injury by releasing mediators that promote hepatocyte apoptosis, contribute to inflammatory cell recruitment and activation of hepatic fibrogenic cells. Here, we investigated whether macrophage autophagy may protect against chronic liver injury. Experiments were performed in mice with mutations in the autophagy gene Atg5 in the myeloid lineage (Atg5fl/fl LysM-Cre mice, referred to as atg5−/−) and their wild-type (Atg5fl/fl, referred to as WT) littermates. Liver fibrosis was induced by repeated intraperitoneal injection of carbon tetrachloride. In vitro studies were performed in cultures or co-cultures of peritoneal macrophages with hepatic myofibroblasts. As compared to WT littermates, atg5−/− mice exposed to chronic carbon tetrachloride administration displayed higher hepatic levels of IL1A and IL1B and enhanced inflammatory cell recruitment associated with exacerbated liver injury. In addition, atg5−/− mice were more susceptible to liver fibrosis, as shown by enhanced matrix and fibrogenic cell accumulation. Macrophages from atg5−/− mice secreted higher levels of reactive oxygen species (ROS)-induced IL1A and IL1B. Moreover, hepatic myofibroblasts exposed to the conditioned medium of macrophages from atg5−/− mice showed increased profibrogenic gene expression; this effect was blunted when neutralizing IL1A and IL1B in the conditioned medium of atg5−/− macrophages. Finally, administration of recombinant IL1RN (interleukin 1 receptor antagonist) to carbon tetrachloride-exposed atg5−/− mice blunted liver injury and fibrosis, identifying IL1A/B as central mediators in the deleterious effects of macrophage autophagy invalidation. These results uncover macrophage autophagy as a novel antiinflammatory pathway regulating liver fibrosis. 相似文献
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A global plastid phylogeny of the brake fern genus Pteris (Pteridaceae) and related genera in the Pteridoideae 下载免费PDF全文