Microhabitat selection and niche partitioning in two syntopic geckos

Syntopic species often exhibit evolutionary mechanisms that reduce competition. A common mechanism facilitating coexistence is niche separation, which may manifest through spatial, temporal or trophic dimensions. Species that are morphologically similar, such as congeners, are likely to compete directly and thus separate their niche spatially. The microhabitat selection and partitioning of two endemic geckos of the Soutpansberg Mountains, Lygodactylus incognitus (Jacobsen, 1992; Squamata: Gekkonidae) and L. soutpansbergensis (Jacobsen, 1994; Squamata: Gekkonidae), was investigated by recording fine‐ and broad‐scale habitat variables. Results reveal that L. incognitus is restricted to high elevations above 1100 m a.s.l. and is associated with moist microclimates. Although primarily saxicolous, they also utilise tree trunks, branches and stems. Lygodactylus soutpansbergensis occurs above 800 m a.s.l and is restricted to rocky outcrops, open woodlands and rocky grasslands, often found on loose rocks. Perch height for L. soutpansbergensis is close to ground level, and they are limited to drier microclimates. Microhabitat partitioning does not appear to be due to interspecific exclusion as the smaller L. soutpansbergensis occupies the same niche dimensions in areas where L. incognitus is not present. Sites where L. incognitus occurs in the absence of L. soutpansbergensis are forested with high canopy cover, likely preventing the colonisation of L. soutpansbergensis. This suggests that morphological and physiological constraints define microhabitat limits, although this still requires testing. Anthropogenic activities are likely to threaten the persistence of L. incognitus and L. soutpansbergensis on the Soutpansberg in the future. The results from this study may aid the interpretation and understanding on the syntopy of morphologically similar species that inhabit the same macrohabitats in other areas.     

Limiting similarity and species assemblages in the short-tailed fruit bats

We analyzed the morphometrics of seven taxa of short-tailed fruit bats Chiroptera : Phyllostomidae : Carollia , ( Carollia benkeithi , Carollia brevicauda , Carollia castanea , Carollia perspicillata azteca , Carollia perspicillata perspicillata , Carollia sowelli and Carollia subrufa ) to assess within-taxon variation and to address the possibility that morphological distinctions facilitate sympatry within this genus of ecologically similar bats. Whereas morphological similarities were found among species in certain combinations of allopatric taxa, members of sympatric assemblages differ significantly, indicating that there is a consistent representation of morphotypes within various assemblages of Carollia despite changes in species composition across the range of the genus. Furthermore, the differences in the skull size and shape among taxa correspond to potential differences in food-handling abilities and point to dietary differentiation among species as a factor in the facilitation of coexistence.     

The specialization and structure of antagonistic and mutualistic networks of beetles on rainforest canopy trees

Different kinds of species interactions can lead to different structures within ecological networks. Antagonistic interactions (such as between herbivores and host plants) often promote increasing host specificity within a compartmentalized network structure, whereas mutualistic networks (such as pollination networks) are associated with higher levels of generalization and form nested network structures. However, we recently showed that the host specificity of flower‐visiting beetles from three different feeding guilds (herbivores, fungivores, and predators) in an Australian rainforest canopy was equal to that of herbivores on leaves, suggesting that antagonistic herbivores on leaves are no more specialized than flower‐visitors. We therefore set out to test whether similarities in the host specificity of these different assemblages reflect similarities in underlying network structures. As shown before at the species level, mutualistic communities on flowers showed levels of specialization at the network scale similar to those of the antagonistic herbivore community on leaves. However, the network structure differed, with flower‐visiting assemblages displaying a significantly more nested structure than folivores, and folivores displaying a significantly more compartmentalized structure than flower‐visitors. These results, which need further testing in other forest systems, demonstrate that both antagonistic and mutualistic interactions can result in equally high levels of host specialization among beetle assemblages in tropical rainforests. If this is a widespread phenomenon, it may alter our current perceptions of food web dynamics, species diversity patterns, and co‐evolution in tropical rainforests. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 287–295.     

Microhabitat use and preferences of the endangered Cottus gobio in the River Voer, Belgium

Microhabitat use and preferences of juvenile and adult bullhead Cottus gobio , from the River Voer, Flanders, were studied and compared across different seasons. Water depth, water velocity near the substratum, surface water velocity and substratum type used by C. gobio differed between seasons. These differences, however, were not attributable to differences in microhabitat availability. Adults appeared to prefer higher water velocities and coarser substrata than the average ones available in the basin. Although water depth appeared to have little influence on seasonal variation of microhabitat use in adult C. gobio , juveniles preferred deeper water and coarser substrata in winter, whereas in summer they appeared to use shallower water. There was a difference in microhabitat use between juvenile and adult bullhead only in summer.     

新疆野果林褐腐病菌的种类

褐腐病是核果和仁果类果树上的一种重要病害。本研究从采集自新疆野果林中的褐腐病样上共分离到75株褐腐菌。利用内转录间隔区（ITS）、β‐微管蛋白基因和延伸因子（EF1α）基因序列和形态学方法,对这些菌株进行了种类鉴定。结果显示：67株为Monilinia fructigena,8株为M. laxa。M. fructigena和M. laxa都分布在新疆北部的天然野果林中。M. fructigena主要来自野苹果、樱桃李、野杏和欧洲李。M. laxa主要来自樱桃李、野苹果和红樱桃。这是首次在新疆地区的野生果林中发现M. fructigena和M. laxa。研究结果不仅对了解当地栽培果园的侵染源有帮助,而且为研究褐腐菌的起源与演化提供了试验材料。     

RAPD技术在果树上的应用(综述)

本文综述RAPD技术的基本原理、特点及在果树品种鉴定、系谱分析、遗传作图、基因定位、育种等方面的应用,并对RAPD技术存在的问题进行讨论.     

果树中糖类代谢和调控研究

糖是生物体内主要的碳源,是光合作用的主要产物,可为生物体提供能量,在植物的生长发育过程中起重要作用。本文综述了近年来关于糖类与果树生长发育及品质形成方面的相关研究进展,重点介绍了糖类运输、积累与基因表达、糖信号传导和糖类调控网络等方面的研究进展,并对今后利用分子生物学手段进行果实品质改良等方面的研究方向进行了展望。     

Structure of ant assemblages on street trees in urban Busan,Korea

Street trees planted in urban areas are one of the smallest urban green habitats; however, their role as a valuable refuge for local biota is poorly understood. The aim of this study was to investigate urban street trees as habitat for ants. We found ants on 195 (92%) of 211 street trees studied. Seventeen ant species were collected from five tree species. The two most common ant species were Tetramorium tsushimae (on 112 trees) and Lasius japonicus (on 93 trees). The number of ant species found per tree ranged from 0 to 5, with a mean of 1.55 ± 0.92. The species composition differed significantly among tree species. Nine ant species (Camponotus vitiosus, Lasius alienus, L. japonicus, Nylanderia flavipes, Crematogaster matsumurai, Crematogaster vagula, Monomorium intrudens, T. tsushimae, and Brachyponera chinensis) nested on the trees, mostly in the root zone. Nests were found on 150 trees but were relatively rare on trees with diameter at breast height of less than 40 cm.     

Microhabitat effects on bryophyte species richness and community distribution on exposed rock outcrops in Portugal

Background: Rock outcrops have been shown to provide specific conditions for bryophyte communities, but no studies have focused on the importance of microhabitats on such communities.

Aim: To analyse the distribution pattern of bryophyte species from granite and schist outcrops in three microhabitats (rock surfaces, fissures and cavities) in Portugal.

Methods: Sample plots were established in fissures, cavities and on rock surfaces of rock outcrops in north and central Portugal. Micro-scale variables, such as exposure and slope were assessed for each microhabitat.

Results: The microhabitats most different in species composition were surfaces versus cavities and surfaces versus fissures, both on granite and schist. Short-lived shuttle species tended to be associated with surfaces, and perennial species were more frequent in cavities and fissures. Both on granite and schist, the number of species found in each microhabitat was highest in cavities, followed by fissures and rock surfaces. The most relevant predictors of bryophyte richness were microhabitat type, exposure and rock type.

Conclusions: This investigation confirmed that rock microhabitats play an important role in bryophyte diversity by promoting habitat heterogeneity. In addition, our results clearly suggest local explanations for variation in bryophyte species richness and communities.     

果树成花转变途径与调控研究进展

植物成花转变是营养生长向生殖生长转变的过程,木本果树过长的童期严重制约了育种的进程。相对于模式植物,目前对果树成花转变与调控的研究相对较少。因此,了解并掌握果树成花转变的途径及调控方法,对于缩短果树童期、调控开花,加速果树育种具有重要意义。基于近年来国内外相关研究,本文系统总结了果树的成花途径,阐述了果树栽培措施、植物生长调节剂等成花调控方法,以及果树中成花调控的相关基因及网络机制。最后,本文还对以修饰组学为主的多组学以及嫁接和植物生长调节剂在果树成花调控中的研究前景进行了展望。     

Ca~(2 )与果树抗逆性的关系(综述)

本文综述Ca2 与果树抗逆性的关系,包括细胞Ca2 的分布及Ca2 稳态的调控、Ca2 在果树“逆境刺激-偶联反应”中的信使作用及其对提高果树抗逆性的作用。     

Influence of niche similarity on hybridization between Myriophyllum sibiricum and M. spicatum

The impact of ecological factors on natural hybridization is of widespread interest. Here, we asked whether climate niche influences hybridization between the two closely related plant species Myriophyllum sibiricum and M. spicatum. Eight microsatellite loci and two chloroplast fragments were used to investigate the occurrence of hybridization between these two species in two co‐occurring regions: north‐east China (NEC) and the Qinghai‐Tibetan Plateau (QTP). The climate niches of the species were quantified by principal component analysis with bioclimatic data, and niche comparisons were performed between the two species in each region. Reciprocal hybridization was observed, and M. sibiricum was favoured as the maternal species. Furthermore, hybrids were rare in NEC but common in the QTP. Accordingly, in NEC, the two species were climatically distinct, and hybrids only occurred in the narrow geographical or ecological transition zone, whereas in the QTP, obvious niche overlaps were found for the two species, and hybrids occurred in multiple contact zones. This association between hybridization pattern and climate niche similarity suggests that the level of hybridization was promoted by niche overlap. Compared with the parental species, similar climate niches were found for the hybrid populations in the QTP, indicating that other environmental factors rather than climate were important for hybrid persistence. Our findings highlight the significance of climate niche with respect to hybridization patterns in plants.     

No effects of fire,large herbivores and their interaction on regrowth of harvested trees in two West African savannahs

Theory and empirical evidence for the impacts of fire and herbivory in savannahs is well established – they are top‐down disturbances that maintain savannahs in disequilibrium states away from potential tree cover. In African savannahs, the demand for fuelwood is extremely high, so tree harvest likely also has an impact, both directly and indirectly, on tree cover, density and biomass. Many savannah trees resprout vigorously from the base after harvest. However, harvested trees regenerate as saplings susceptible to fire and browsing, so harvest may have important demographic consequences. Here, we report the effects of tree harvest, and its interaction with fire and herbivory, on savannah dynamics by analysing woody regrowth following a harvest in arid Sahelian and mesic Guinean savannahs in Mali, West Africa. Tree harvest resulted in an overall reduction in wood production per tree compared to growth in nonharvested trees. Regrowth, either biomass or height, did not differ among fire and herbivory treatments. Our results suggest that the resprouting abilities that savannah trees have evolved to cope with frequent fire are essential for surviving tree harvest and subsequent disturbance. In these savannahs, regrowth is rapid enough in the first growing season to escape the impact of dry season fires.     

云南亚热带南部表土孢粉组合与植被间的定量关系

以云南亚热带南部沿温度带分布的35个表土孢粉样品和7个植被样方调查为基础,计算了代表性孢粉类型的百分比和孢粉浓度,及常见孢粉的R值,并分析了影响R值的因素;同时,研究了植物群落和样方内孢粉组合的相似度。结果表明,云南亚热带南部表土样品孢粉产量丰富,蕨类植物孢子产量较高,具有典型的亚热带特征,且山地垂直分异显著;木本、草本植物花粉基本代表了区域内乔木和草本植物特征,蕨类植物孢子则具有超代表性;表土孢粉组合与植物群落间的相似系数绝大部分都在70％以上,表土孢粉组合基本上可以反映植物群落面貌;表明云南亚热带地区表土孢粉与现代植被之间具有较好的对应关系,这对在该区利用化石孢粉资料定量恢复古植被和重建古气候有重要意义。     

Unexpected sequence similarity between nucleosidases and phosphoribosyltransferases of different specificity.

Amino acid sequences of enzymes that catalyze hydrolysis or phosphorolysis of the N-glycosidic bond in nucleosides and nucleotides (nucleosidases and phosphoribosyltransferases) were explored using computer methods for database similarity search and multiple alignment. Two new families, each including bacterial and eukaryotic enzymes, were identified. Family I consists of Escherichia coli AMP hydrolase (Amn), uridine phosphorylase (Udp), purine phosphorylase (DeoD), uncharacterized proteins from E. coli and Bacteroides uniformis, and, unexpectedly, a group of plant stress-inducible proteins. It is hypothesized that these plant proteins have evolved from nucleosidases and may possess nucleosidase activity. The proteins in this new family contain 3 conserved motifs, one of which was found also in eukaryotic purine nucleosidases, where it corresponds to the nucleoside-binding site. Family II is comprised of bacterial and eukaryotic thymidine phosphorylases and anthranilate phosphoribosyltransferases, the relationship between which has not been suspected previously. Based on the known tertiary structure of E. coli thymidine phosphorylase, structural interpretation was given to the sequence conservation in this family. The highest conservation is observed in the N-terminal alpha-helical domain, whose exact function is not known. Parts of the conserved active site of thymidine phosphorylases and anthranilate phosphoribosyltransferases were delineated. A motif in the putative phosphate-binding site is conserved in family II and in other phosphoribosyltransferases. Our analysis suggests that certain enzymes of very similar specificity, e.g., uridine and thymidine phosphorylases, could have evolved independently. In contrast, enzymes catalyzing such different reactions as AMP hydrolysis and uridine phosphorolysis or thymidine phosphorolysis and phosphoribosyl anthranilate synthesis are likely to have evolved from common ancestors.     

Non-dominant trees significantly enhance species richness of epiphytic lichens in subtropical forests of southwest China

Host species has an important influence on the distribution of epiphytic lichens in forests. However, the importance of non-dominant trees in shaping lichen communities has been poorly studied owing to the relative rarity of individuals. The importance of dominant and non-dominant trees for distribution of epiphytic lichens was determined in eight subtropical forests in southwestern China. Dominant trees supported more abundant total and exclusive lichen species only in secondary forests. The occurrence of non-dominant trees promoted lichen diversity within forest types and influenced lichen communities on both tree groups. The effects of total tree species on lichen distribution largely resulted from the presence of non-dominant trees. Dominant and non-dominant trees supported distinct lichen assemblages within forest types, and ordination analyses showed a clear separation. Our study, therefore, reinforces the importance of non-dominant trees for conserving epiphytic lichens, and highlights that lichen assemblages are shaped by both dominant and non-dominant trees.     

Exploring the nature of ecological specialization in a coral reef fish community: morphology,diet and foraging microhabitat use

Patterns of ecological specialization offer invaluable information about ecosystems. Yet, specialization is rarely quantified across several ecological niche axes and variables beyond the link between morphological and dietary specialization have received little attention. Here, we provide a quantitative evaluation of ecological specialization in a coral reef fish assemblage (f. Acanthuridae) along one fundamental and two realized niche axes. Specifically, we examined ecological specialization in 10 surgeonfish species with regards to morphology and two realized niche axes associated with diet and foraging microhabitat utilization using a recently developed multidimensional framework. We then investigated the potential relationships between morphological and behavioural specialization. These relationships differed markedly from the traditional ecomorphological paradigm. While morphological specialization showed no relationship with dietary specialization, it exhibited a strong relationship with foraging microhabitat specialization. However, this relationship was inverted: species with specialized morphologies were microhabitat generalists, whereas generalized morphotypes were microhabitat specialists. Interestingly, this mirrors relationships found in plant–pollinator communities and may also be applicable to other ecosystems, highlighting the potential importance of including niche axes beyond dietary specialization into ecomorphological frameworks. On coral reefs, it appears that morphotypes commonly perceived as most generalized may, in fact, be specialized in exploiting flat and easily accessible microhabitats.     

Seasonal changes of microclimatic conditions in grasslands and its influence on orthopteran assemblages

We examined the microclimate of different grasslands and the relationships between the seasonal changes in the microclimatic conditions and the structural characteristics of orthopteran assemblages in the most typical grassland types of the plain, hilly and submontaneous territories of Central Europe in 2000–2005 years. According to our results: (i) The seasonal changes of humidity were characteristic of the vegetation units; (ii) The microclimate components of grasslands with similar habitat structure could be similar independently from their ecological circumstances; (iii) The microclimatic changes influenced the structure of the orthopteran assemblages.