Phylogenetic diversity,structure and diversification patterns of endemic plants along the elevational gradient in the Eastern Himalaya

ABSTRACT

Background: Several studies have documented the variation in species diversity patterns along elevational gradients in the Himalaya, but few have reported the evolutionary and biogeographic processes behind these patterns.

Aims: To understand whether evolutionary history and phylogeny have any role in structuring plant species communities along an elevational gradient in the Sikkim Himalaya.

Methods: We used data on endemic plant species occurrence from primary and secondary sources to construct family-level phylogenetic supertrees for different growth forms with the help of Phylomatic tool of Phylocom. These phylogenetic supertrees were used as a base for testing phylogenetic diversity (PD), niche conservatism, diversification time patterns and phylogenetic structure of various plant growth forms along an elevational gradient.

Results: PD was the highest at mid-elevations for all growth forms and PD had a significant positive correlation with endemic species richness. Species at mid-elevations were dominated by the ancestral/primitive taxa. There was phylogenetic clustering at higher elevations and phylogenetic overdispersion at lower and mid-elevations for the majority of the growth forms.

Conclusions: Time-for-speciation effect and niche conservatism along elevation (retention of niche-related ancestral elevational distribution over evolutionary time scale by species) together determine plant species diversity patterns in the Himalaya.     

结构植物学在中国的五十年发展

结构植物学由植物解剖学发展而来 ,是植物学的一个重要分支学科。本文根据其近代的发展 ,分别就植物发育解剖学向植物发育生物学的发展、植物比较解剖学向植物系统发育生物学的发展 ,以及环境生态结构植物学三个主要部分简要介绍了 5 0年来在我国的发展 ,并对它们的发展趋势进行了预测     

结构植物学在中国的五十年发展

结构植物学由植物解剖学发展而来,是植物学的一个重要分支学科.本文根据其近代的发展,分别就植物发育解剖学向植物发育生物学的发展、植物比较解剖学向植物系统发育生物学的发展,以及环境生态结构植物学三个主要部分简要介绍了50年来在我国的发展,并对它们的发展趋势进行了预测.     

C4 photosynthetic modifications in the evolutionary transition from land to water in aquatic grasses

Cladistic analysis supports the conclusion that the Orcuttieae tribe of C₄ grasses reflect evolution from a terrestrial ancestry into seasonal pools. All nine species in the tribe exhibit adaptations to the aquatic environment, evident in the structural characteristics of the juvenile foliage, which persist submerged for 1–3 months prior to metamorphosis to the terrestrial foliage. Aquatic leaves of the least derived or basal genus Neostapfia have few morphological and anatomical characteristics specialized to the aquatic environment and have retained full expression of the C₄ pathway, including Kranz anatomy. Orcuttia species have many derived characteristics and are more specialized to the aquatic environment. These latter species germinate earlier in the season and persist in the submerged stage longer than Neostapfia and evidence from the literature indicates length of submergence is positively correlated with fitness components. Aquatic leaves of Orcuttia species lack Kranz or PCR bundle sheath anatomy, yet ¹⁴C-pulse chase studies indicate >95% malate + aspartate as the initial products of photosynthesis and these products turn over rapidly to phosphorylated sugars, indicating a tight coupling of the C₄ and C₃ cycles. Presence of the C₄ pathway is further supported by enzymological data. Contemporary dogma that Kranz anatomy is a sine qua non for operation of the C₄ pathway is contradicted by the patterns in Orcuttia; however, it is unknown whether the pathway acts as a CO₂ concentrating mechanism in these aquatic plants. Received: 12 June 1997 / Accepted: 10 February 1997     

A comment on the earliest spalacinae (rodentia,Muroidea)

According to F. M. Catzefliset al. (Trends Ecol. Evol. 7, 122–126, 1992), comparative dating of the oldest dichotomy in the muroid group (Spalacinae-other Muridae) by molecular and paleontological time scales produces conflicting results. For the earliest Spalacinae they refer to a date of 25–37 Ma; however, it has been demonstrated thatRhizospalax is not a muroid rodent, and a review of the record of fossil Spalacinae suggests that paleontological and molecular dating produces a comparable age (±19 Ma).     

植物比较解剖学在中国50年的进展和展望

系统与进化植物学是当今植物科学中的主流学科之一,植物比较解剖学是该学科的重要组成部分。根据近50年国内主要期刊统计,我国植物学者重点在种子植物的维管组织结构、叶及其表皮结构、花的结构和发育、种子及种皮特征、分泌组织以及一些原始种子植物等方面开展了比较解剖研究,为一些植物科、属的系统分类提供了解剖学依据。但在研究的植物种类、内容和方法尚存在不足,发表的论文相对较少。根据我国植物种质资源丰富,研究基础较好等特点,认为我国植物比较解剖学发展前景宽广,并对进一步发展提出一些建议。     

Wood anatomical correlates with theoretical conductivity and wood density across China: evolutionary evidence of the functional differentiation of axial and radial parenchyma

Background and Aims

In recent years considerable effort has focused on linking wood anatomy and key ecological traits. Studies analysing large databases have described how these ecological traits vary as a function of wood anatomical traits related to conduction and support, but have not considered how these functions interact with cells involved in storage of water and carbohydrates (i.e. parenchyma cells).

Methods

We analyzed, in a phylogenetic context, the functional relationship between cell types performing each of the three xylem functions (conduction, support and storage) and wood density and theoretical conductivity using a sample of approx. 800 tree species from China.

Key Results

Axial parenchyma and rays had distinct evolutionary correlation patterns. An evolutionary link was found between high conduction capacity and larger amounts of axial parenchyma that is probably related to water storage capacity and embolism repair, while larger amounts of ray tissue have evolved with increased mechanical support and reduced hydraulic capacity. In a phylogenetic principal component analysis this association of axial parenchyma with increased conduction capacity and rays with wood density represented orthogonal axes of variation. In multivariate space, however, the proportion of rays might be positively associated with conductance and negatively with wood density, indicating flexibility in these axes in species with wide rays.

Conclusions

The findings suggest that parenchyma types may differ in function. The functional axes represented by different cell types were conserved across lineages, suggesting a significant role in the ecological strategies of the angiosperms.     

The importance of the “Gegenbaur school” for German morphology

Summary The school Carl Gegenbaur cultivated at Heidelberg (1873–1901) was critical to the history of German morphology in multiple ways. During and after his lifetime, the school carried out detailed comparative anatomical and embryological investigations in an evolutionary framework, thereby contributing substantially to the project of vertebrate evolutionary morphology. Its members also defended their mentor when his ideas came under attack. After his death, they labored to perpetuate his program and his memory in the increasingly unwelcoming environment of medical education and research. While the senior members of the school did this largely through institutional means-seeking to place Gegenbaur sympathizers in academic and editorial positions-its junior members absorbed some of the criticisms of the school to develop a modified, more functional approach to evolutionary morphology. The school thus kept the Gegenbaur program alive and active in the German-speaking lands for over fifty years. This paper is drawn largely from Nyhart (1995), esp. chapter 7 (supported by NSF award no. 8910873). Information not otherwise documented derives from this book.     

Mobile larynx in Mongolian gazelle: Retraction of the larynx during rutting barks in male Mongolian gazelle (Procapra gutturosa Pallas, 1777)

This study provides the first evidence of pronounced temporary laryngeal descent in a bovid species. An elaborate acoustic display is prominent in male courtship behavior of polygynous Mongolian gazelle. During rut, rounding up of females is accompanied by continuous head‐up barking by dominant males. Throughout the rut their evolutionarily enlarged larynx descends to a low mid‐neck resting position. In the course of each bark the larynx is additionally retracted toward the sternum by 30% of the resting vocal tract length. A geometric model of active larynx movements was constructed by combining results of video documentation, dissection, skeletonization, and behavioral observation. The considerable distance between resting position and maximal laryngeal descent suggests a backward tilting of the hyoid apparatus and an extension of the thyrohyoid connection during the retraction phase. Return to the resting position is effected by strap muscles and by the elastic recoil of the pharynx and the thyrohyoid connection. An intrapharyngeal inflation of the peculiar palatinal pharyngeal pouch of adult males is inferred from a short‐time expansion of the ventral neck region rostral to the laryngeal prominence. The neck of adult dominant males is accentuated by long gray guard hairs during the rut. The passive swinging of the heavy larynx of adult males during locomotion gives the impression of a handicap imposed on rutting males. Apparently, this disadvantage becomes outweighed by the profits for reproductive success. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.     

不同生长年份移山参根的比较解剖学研究

采用石蜡制片法、显微观察生长8年、12年和16年的移山参主根中部的组织结构,并以4年生栽培参(二马牙)和西洋参为对照进行比较分析。结果表明,移山参主根结构由周皮和次生维管组织组成。不同生长年份的移山参主根结构具有一定差异:随生长年份的增长,木栓层细胞体积变小,排列趋于紧密;栓内层草酸钙结晶越来越少;分泌道均为3轮,但平均口径逐渐减小;韧皮部外侧和木质部靠近根中央处的薄壁组织的裂隙逐渐增大;韧皮部与木质部的面积比则不断下降;12年、16年生移山参主根次生木质部中导管数量和层数明显多于8年生。PAS 反应表明淀粉粒含量在生长12年以后趋于稳定。表明通过观察移山参木质部与韧皮部的面积比和次生维管组织中木质部导管的数量及层数,可以初步判断移山参的生长年份。     

昆虫比较线粒体基因组学研究进展

动物线粒体基因组因其基因组成稳定、基因排列相对保守、普遍为母系遗传、极少发生重组等而被广泛应用于进化与系统发育等研究。目前,昆虫中已有356个线粒体基因组序列被测定,代表了33个目中的28个目。大量比较基因组学研究使得我们对昆虫线粒体基因组的特征与进化方式有了较为清晰的认识。本文对昆虫线粒体基因组的测序进展、基因组的结构特征、碱基组成、控制区的特征、基因重排及其机理、进化速率及其在昆虫系统发育研究中的应用等方面的研究进展进行介绍。