When the exception becomes the rule: The disappearance of limiting similarity in the Lotka-Volterra model

We investigate the transition between limiting similarity and coexistence of a continuum in the competitive Lotka-Volterra model. It is known that there exist exceptional cases in which, contrary to the limiting similarity expectation, all phenotypes coexist along a trait axis. Earlier studies established that the distance between surviving phenotypes is in the magnitude of the niche width 2σ provided that the carrying capacity curve differs from the exceptional one significantly enough. In this paper we studied the outcome of competition for small perturbations of the exceptional (Gaussian) carrying capacity. We found that the average distance between the surviving phenotypes goes to zero when the perturbation vanishes. The number of coexisting species in equilibrium is proportional to the negative logarithm of the perturbation. Nevertheless, the niche width provides a good order of magnitude for the distance between survivors if the perturbations are larger than 10%. Therefore, we conclude that limiting similarity is a good framework of biological thinking despite the lack of an absolute lower bound of similarity.     

Xylem heterochrony: an unappreciated key to angiosperm origin and diversifications

All angiosperms can be arranged along a spectrum from a preponderance of juvenile traits (cambial activity lost) to one of nearly all adult characters (cambium maximally active, mature patterns realized rapidly early in ontogeny). Angiosperms are unique among seed plants in the width of this spectrum. Xylem patterns are considered here to be indicative of contemporary function, not relictual. Nevertheless, most families of early‐divergent angiosperms exhibit paedomorphic xylem structure, a circumstance that is most plausibly explained by the concept that early angiosperms had sympodial growth forms featuring limited accumulation of secondary xylem. Sympodial habits have been retained in various ways not only in early‐divergent angiosperms, but also among eudicots in Ranunculales. The early angiosperm vessel, relatively marginal in conductive abilities, was improved in various ways, with concurrent redesign of parenchyma and fibre systems to enhance conductive, storage and mechanical capabilities. Flexibility in degree of cambial activity and kinds of juvenile/adult expressions has been basic to diversification in eudicots as a whole. Sympodial growth that lacks cambium, such as in monocots, provides advantages by various features, such as organographic compartmentalization of tracheid and vessel types. Woody monopodial eudicots were able to diversify as a result of production of new solutions to embolism prevention and conductive efficiency, particularly in vessel design, but also in parenchyma histology. Criteria for paedomorphosis in wood include slow decrease in length of fusiform cambial initials, predominance of procumbent ray cells and lesser degrees of cambial activity. Retention of ancestral features in primary xylem (the ‘refugium’ effect) is, in effect, a sort of inverse evidence of acceleration of adult patterns in later formed xylem. Xylem heterochrony is analysed not only for all key groups of angiosperms (including monocots), but also for different growth forms, such as lianas, annuals, various types of perennials, rosette trees and stem succulents. Xylary phenomena that potentially could be confused with heterochrony are discussed. Heterochronous xylem features seem at least as important as other often cited factors (pollination biology) because various degrees of paedomorphic xylem are found in so many growth forms that relate in xylary terms to ecological sites. Xylem heterochrony can probably be accessed during evolution by relatively simple gene changes in a wide range of angiosperms and thus represents a current as well as a past source of variation upon which diversification was based. Results discussed here are compatible with both current molecular‐based phylogenetic analyses and all recent physiological work on conduction in xylem and thus represent an integration of these fields. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161 , 26–65.     

Do tracheid microstructure and the presence of minute crystals link Nymphaeaceae,Cabombaceae and Hydatellaceae?

Original scanning electron microscopy (SEM) observations are presented for stems of Brasenia schreberi and Cabomba caroliniana of Cabombaceae and three species of Trithuria of Hydatellaceae. End walls of stem tracheids of Brasenia have the same peculiar microstructure that we have reported in Barclaya, Euryale, Nuphar, Nymphaea (including Ondinea) and Victoria of Nymphaeaceae. This feature unites Cabombaceae with Nymphaeaceae. The minute rhomboidal crystals on the surfaces of stellate parenchyma cells of Brasenia reported by Solereder (1906. Oxford: University Press), but not noticed since, are figured. They are like the minute crystals of the often‐mentioned astrosclereids of Nymphaeaceae. Neither of these two features has been observed in Hydatellaceae. If the absence of these two features can be confirmed, the reason may be more related to ecology, development, habit and anatomical organization than to degree of phylogenetic relationship as shown by molecular studies. Anatomical observations on the stem anatomy of Trithuria are offered on the basis of paraffin sections prepared for a paper by Cheadle & Kosakai (1975. American Journal of Botany 62: 1017–1026); that study is notable for a discrepancy between an illustration of a specialized vessel element on the one hand and tabular data indicating long scalariform perforation plates on the other. Long scalariform perforation plates are mostly found in scalariformly pitted vessels of monocots, whereas the tracheary elements of Trithuria mostly have helical or annular thickenings. We were unable to demonstrate the presence of vessels in Hydatellaceae. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 572–582.     

Bioluminescence emissions of the firefly <Emphasis Type="Italic">Luciola praeusta</Emphasis> Kiesenwetter 1874 (Coleoptera: Lampyridae: Luciolinae)

We recorded the in vivo emission and time-resolved spectra of the firefly Luciola praeusta Kiesenwetter 1874 (Coleoptera: Lampyridae: Luciolinae). The emission spectrum shows that the full width at half maximum (FWHM) value for this particular species is 55 nm, which is significantly narrower than the in vivo half-widths reported till now. The time-resolved spectrum reveals that a flash of about 100 ms duration is, in fact, composed of a number of microsecond pulses. This suggests that the speed of the enzyme-catalysed chemiluminescence reaction in the firefly for the emission of light is much faster than was previously believed. A version of this article has already appeared in an archive Nature Precedings; see     

黄土丘陵区草地土壤微生物C、N及呼吸熵对植被恢复的响应

以野外样地调查和室内分析法研究了黄土丘陵区不同植被恢复年限下草地土壤微生物C、N及土壤呼吸熵的变化.结果表明,土壤微生物量碳明显地随着植被恢复年限的增加而增加.在恢复前23a, 土壤微生物量碳在0～20 cm土层年增加率为24.1%;20～40 cm为104.4%.植被恢复23a后,0～20 cm土层增长率为0.83%,20～40 cm为0.19%.土壤微生物量N表现为在植被恢复的初期略有下降,3a后,开始出现明显增加.0～20 cm土层年增长率为20.14%,20～40 cm为15.11%.在植被恢复23a后,0～20 cm土层的年增长率为0.14%,20～40 cm变化不大.土壤微生物呼吸强度随着恢复年限的增加逐渐加强;土壤呼吸熵随植被封育时间的增加而呈对数降低趋势.土壤呼吸熵(qCO2)在反映土壤的生物质量变化时,显得更加稳定,受植物生长状况影响较小.相关分析表明,土壤微生物量和土壤微生物活性与土壤有机质、碱解氮和粘粒含量显著正相关;与土壤粉粒含量明显负相关;表层土壤pH值对其也有明显影响.草地植被自然恢复过程可增加土壤微生物活性,有利于土壤质量的提高.     

Incipient forebrain boundaries traced by differential gene expression and fate mapping in the chick neural plate

We correlated available fate maps for the avian neural plate at stages HH4 and HH8 with the progress of local molecular specification, aiming to determine when the molecular specification maps of the primary longitudinal and transversal domains of the anterior forebrain agree with the fate mapped data. To this end, we examined selected gene expression patterns as they normally evolved in whole mounts and sections between HH4 and HH8 (or HH10/11 in some cases), performed novel fate-mapping experiments within the anterior forebrain at HH4 and examined the results at HH8, and correlated grafts with expression of selected gene markers. The data provided new details to the HH4 fate map, and disclosed some genes (e.g., Six3 and Ganf) whose expression domains initially are very extensive and subsequently retract rostralwards. Apart from anteroposterior dynamics, some genes soon became downregulated at the prospective forebrain floor plate, or allowed to identify an early roof plate domain (dorsoventral pattern). Peculiarities of the telencephalon (initial specification and differentiation of pallium versus subpallium) are contemplated. The basic anterior forebrain subdivisions seem to acquire correlated specification and fate mapping patterns around stage HH8.     

The apical/basal-polarity determinant Scribble cooperates with the PCP core factor Stbm/Vang and functions as one of its effectors

Most tissues display several features of cellular polarization. Besides the ubiquitous epithelial polarization in the Apical–Basal (A/B) axis, many epithelia (and associated organs) display a Planar Cell Polarization (PCP). Recently, a crosstalk between the PCP and A/B polarity determinants has been suggested, i.e. the activity or stability of the PCP factor Frizzled is regulated by the A/B determinants aPKC and Bazooka in the Drosophila eye. We have systematically investigated genetic and physical interactions between the Drosophila A/B factors and the core PCP component Strabismus (Stbm)/Van Gogh (Vang). The A/B determinant Scribble was found to interact both genetically and physically with Stbm/Vang. We demonstrate that Scribble binds Stbm/Vang through its PDZ domain 3 and that it cooperates with Stbm/Vang in PCP establishment. Our data indicate that Scribble, in addition to its role in A/B polarity, has a distinct requirement in PCP establishment in the Drosophila eye and wing. We define a scribble allele that is largely PCP specific. Our data show that Scribble is part of the Stbm/Vang PCP complex and further suggest that it might act as an effector of Stbm/Vang during PCP establishment.     

高血压基底节区脑出血患者血清CXCL1、CXCL10与神经损伤指标和微创穿刺引流术后预后的关系研究

摘要 目的：探讨高血压基底节区脑出血（HBGH）患者血清CXC趋化因子配体1（CXCL1）、CXC趋化因子配体10（CXCL10）与神经损伤指标和微创穿刺引流术后预后的关系。方法：选取2020年2月~2023年4月聊城市人民医院东院区收治的行微创穿刺引流术治疗的HBGH患者162例纳入研究组，选取体检健康的志愿者110例纳入对照组。检测对比两组血清CXCL1、CXCL10和神经损伤指标[神经元特异性烯醇化酶（NSE）、胶质纤维酸性蛋白（GFAP）、S100β蛋白]水平。采用Pearson检验分析血清CXCL1、CXCL10与神经损伤指标的相关性。所有患者均随访3个月，根据改良Rankin量表（mRS）评分分为预后良好组和预后不良组。采用多因素Logistic回归模型分析HBGH患者微创穿刺引流术后预后的影响因素。结果：研究组的血清CXCL1、CXCL10水平高于对照组（P<0.05）。研究组的血清NSE、GFAP、S100β蛋白水平高于对照组（P<0.05）。Pearson检验分析结果显示，血清CXCL1、CXCL10与NSE、GFAP、S100β蛋白均呈正相关（P<0.05）。单因素分析结果显示，预后不良与年龄、甘油三酯（TG）、低密度脂蛋白（LDL）、凝血酶原时间（PT）、C反应蛋白（CRP）、血肿破入脑室、血肿体积、术后24 h内血肿清除率、尿激酶冲管次数、术后颅内出血再发、CXCL1、CXCL10有关（P<0.05）。多因素Logistic回归分析结果显示，年龄偏大、LDL偏高、血肿体积偏大、术后24 h内血肿清除率偏低、尿激酶冲管次数偏多、CXCL1偏高、CXCL10偏高是HBGH患者微创穿刺引流术后预后不良的危险因素（P<0.05）。结论：HBGH患者血清CXCL1、CXCL10水平升高可能导致神经损伤和不良预后。年龄、LDL、血肿体积、术后24 h内血肿清除率、尿激酶冲管次数、CXCL1、CXCL10是HBGH患者术后预后不良的危险因素，值得引起重视。     

Architectural Tradeoffs between Adventitious and Basal Roots for Phosphorus Acquisition

Adventitious rooting contributes to efficient phosphorus acquisition by enhancing topsoil foraging. However, metabolic investment in adventitious roots may retard the development of other root classes such as basal roots, which are also important for phosphorus acquisition. In this study we quantitatively assessed the potential effects of adventitious rooting on basal root growth and whole plant phosphorus acquisition in young bean plants. The geometric simulation model SimRoot was used to dynamically model root systems with varying architecture and C availability growing for 21 days at 3 planting depths in 3 soil types with contrasting nutrient mobility. Simulated root architectures, tradeoffs between adventitious and basal root growth, and phosphorus acquisition were validated with empirical measurements. Phosphorus acquisition and phosphorus acquisition efficiency (defined as mol phosphorus acquired per mol C allocated to roots) were estimated for plants growing in soil in which phosphorus availability was uniform with depth or was greatest in the topsoil, as occurs in most natural soils. Phosphorus acquisition and acquisition efficiency increased with increasing allocation to adventitious roots in stratified soil, due to increased phosphorus depletion of surface soil. In uniform soil, increased adventitious rooting decreased phosphorus acquisition by reducing the growth of lateral roots arising from the tap root and basal roots. The benefit of adventitious roots for phosphorus acquisition was dependent on the specific respiration rate of adventitious roots as well as on whether overall C allocation to root growth was increased, as occurs in plants under phosphorus stress, or was lower, as observed in unstressed plants. In stratified soil, adventitious rooting reduced the growth of tap and basal lateral roots, yet phosphorus acquisition increased by up to 10% when total C allocation to roots was high and adventitious root respiration was similar to that in basal roots. With C allocation to roots decreased by 38%, adventitious roots still increased phosphorus acquisition by 5%. Allocation to adventitious roots enhanced phosphorus acquisition and efficiency as long as the specific respiration of adventitious roots was similar to that of basal roots and less than twice that of tap roots. When adventitious roots were assigned greater specific respiration rates, increased adventitious rooting reduced phosphorus acquisition and efficiency by diverting carbohydrate from other root types. Varying the phosphorus diffusion coefficient to reflect varying mobilities in different soil types had little effect on the value of adventitious rooting for phosphorus acquisition. Adventitious roots benefited plants regardless of basal root growth angle. Seed planting depth only affected phosphorus uptake and efficiency when seed was planted below the high phosphorus surface stratum. Our results confirm the importance of root respiration in nutrient foraging strategies, and demonstrate functional tradeoffs among distinct components of the root system. These results will be useful in developing ideotypes for more nutrient efficient crops.