Ecological distinctions between sympatric species of Saguinus and Sciurus

Tamarins are small New World monkeys that have been described as "squirrellike." Squirrels, along with bats and birds, are the taxa most likely to utilize resources similar to those used by primates in the tropical forest canopy. In this paper we compare differences in ecology, diet, locomotion, and habitat utilization between sympatric populations of tamarins (Saguinus oedipus) and tree squirrels (Sciurus granatensis) in Panama. Data presented indicate that although there is some degree of resource overlap, patterns of habitat utilization differ significantly. Rather than being "squirrellike," the Panamanian tamarin exhibits a pattern of locomotor and feeding behavior consistent with that found in other arboreal primates.     

Alternative dental measurements: proposals and relationships with other measurements

Most archaeological and fossil teeth are heavily worn, and this greatly limits the usefulness of tooth crown diameter measurements, as they are usually defined at the widest points of the crown. There are alternatives, particularly measurements at the cervix of the tooth, where the crown joints the root, and measurements along a diagonal axis in molars, that are much less affected by wear. These would allow a wider range of specimens to be included, e.g., in the study of dental reduction in Upper Palaeolithic and Mesolithic Homo sapiens. In addition, they would allow the little-worn teeth of children to be compared directly with well-worn teeth in adults. These alternatives, however, have been little used, and as yet there have not been any studies of the repeatability with which they can be measured, or of the extent to which they are related to the more usual crown diameters. The present study is based on a group of unworn teeth, where direct comparisons could be made between the alternative measurements, which are not much affected by wear, with the usual crown diameters, which are very much affected. In an interobserver-error study of this material, cervical and diagonal measurements could be recorded as reliably as the usual crown diameters. The buccolingual cervical measurement was strongly correlated with the normal bucclingual crown diameter in all teeth, whereas the mesiodistal cervical measurement was highly correlated with the normal mesiodistal crown diameter in incisors and canines, but less so in premolars and molars. The molar diagonal measurements showed high correlations with all other measurements. Crown areas (robustness index) calculated from the usual diameters were strongly correlated with crown areas calculated from cervical measurements, and crown areas calculated from molar diagonals were strongly correlated with both other areas. Despite the long usage of the more usual maximum crown diameters, the alternative dental measurements could be measured just as reliably, could record similar information about tooth crown size, and would be better measures for the worn dentitions seen in archaeological and fossil material.     

Genetic variability in Lycopersicon species and their genetic relationships

Summary Genetic diversity has to be described and measured in order to establish breeding strategies and manage genetic resources. It is also fundamental to develop a comparative intraspecific study before attempting to discuss and conclude any phylogenetic relationship. The genetic variability of Lycopersicon species was studied using starch gel electrophoresis of 11 enzymatic systems in a hierarchical fashion. The species with the greatest genetic variability are L. chilense, L. peruvianum and L. pennellii, mainly due to the within-line component. L. chmielewskii, L. parviflorum and L. pimpinellifolium show an intermediate total variability and their between-component clearly predominates over the within-component. The least variable species are L. cheesmanii and L. esculentum. Cluster analysis resulted in three main groups: one formed by the cultigen, L. pimpinellifolium, L. cheesmanii and L. peruvianum;another by two species with self-incompatibility systems, L. pennelli and L. chilense; and another by two autogamous species L. chmielewskii and L. parviflorum. With respect to L. esculentum the farthest related species is Solanum rickii and the closest, L. pimpinellifolium.     

Studies in Festuca. II. Fertility relationships between species of sections bovinae and scariosae,and their affinities with Lolium

Crossability anf F₁ hybrid fertility were studied using chromosome races (species or infra-specific taxa) representative of broad-leaved fescues in sections bovinae and scariosae. Hybrids were also obtained with Lolium multiflorum. The hybridization results, when considered in relation to morphology, cytology, and geographical distribution, support the idea that the Moroccan fescues studied here are more closely related amongst themselves, than to taxa from outside this region. These findings are discussed in relation to the evolution of the polyploids.     

内蒙古羊草群落、功能群、物种变化及其与气候的关系

基于1981-1994年内蒙古羊草草原的群落学调查数据和同期气象资料,分析了羊草草原群落、功能群与主要物种变化及其生物量与气候的关系.结果表明,1981-1994年5月羊草群落多样性指数、优势度指数、丰富度指数、群落高度、群落生物量的年际变异显著高于其他月,其中羊草群落生物量的变异性自5-9月依次降低,生物量和多样性不存在显著相关性.羊草群落、功能群、物种的年际变异依次增大;不同功能群中一二年生草本和中生植物的年际波动最大,不同物种间的均衡效应降低了群落的变异性.羊草群落生物量具有气候累积效应,主要受上年10月至当年12月的均温、4-8月降水、上年10月至当年8月累积降水的影响,表明羊草群落生物量变化由不同时段的水热因子协同作用决定.     

Body weights in mixed species troops of Saguinus mystax mystax and Saguinus fuscicollis nigrifrons in Amazonian Peru

An investigation of body weights of members of mixed species troops of Saguinus mystax mystax and Saguinus fuscicollis nigrifrons was conducted at the Rio Blanco Research Station in northeastern Peru. A total of 107 adult and subadult tamarin monkeys were trapped, measured, and released. Data collected indicate that mean body weights for adult male and female moustached tamarins are 564 gm and 626 gm, respectively, whereas for adult saddle-back tamarins these values are 412 gm and 411 gm. Subadults weighed 11-27% less than adults. Body weights recorded in this study are significantly greater than those previously reported for tamarins of the same species and age living in other areas of Amazonian Peru. We hypothesize that, in the case of moustached and saddle-back tamarins, advantages associated with feeding and foraging in mixed species troops facilitate greater efficiency in resource monitoring and result in the maintenance of larger body weights.     

The genus Argemone. I. Cytogenetic relationships between diploid species

Cytogenetic investigations of 5 diploid Argemone species and their hybrids were undertaken. Correlative informations on the morphology, cytology, crossability and interfertility have been secured to understand the mechanism crossability and interfertility have been secured to understand the mechanism of speciation in the genus.All species studied possess 14 bivalents, normal meiosis and perfect pollen and seed fertility.Statistical comparisons regarding two meiotic metrics (frequency of ring bivalents; chiasma frequency) between some of the species revealed significant differences.Crosses were attempted in all species combinations, and hybrids were obtained in several. On the basis of pollen and seed fertility these were classified as fortile (mexicana × subfusiformis; subjusiformis × mexicana f. leiocarpa) and semifertile (mexicana × albiflora; subjusiformis × platyceras; mexicana f. leiocarpa × platyceras) hybrids. F₁'s are intermediate, qualitatively they exhibit heterosis.Meiosis was analysed in all hybrids (pachynema; M-I, A-I) and several metrics e.g. ring bivalent frequency, chiasma frequency were taken as indices of genome affinity.It is suggested that mexicana, mexicana f. leiocarpa and subfusiformis are taxonomically close and display only allelic differentiation: albiflora and platyceras are structurally distinct from each other. Several structural changes e.g. duplications, inversions, translocations etc. were involved in their differentiation.The role of isolation barriers in maintaining species differentiation is discussed.     

Craniometrical variations among eastern Brazilian marmosets and their systematic relationships

The craniometrical variations among marmosets on the eastern coast of Brazil or theCallithrix jacchus group (C. jacchus, C. penicillata, C. kuhli, C. geoffroyi, C. flaviceps, andC. aurita) were analyzed to test various hypotheses for the arrangement of the species and phylogenetic relationships ofC. kuhli andC. flaviceps. Q-mode correlation coefficients and principal component analysis were employed to extract important shape factors from the craniometrical data. On this basis, the shape distances among the eastern Brazilian marmosets were found to be larger than those between the marmosets which are recognized as distinct species. This evidence supports the hypothesis that the members of theC. jacchus group are distinct species.C. kuhli shows the strongest resemblance toC. geoffroyi within theC. jacchus group.C. flaviceps is the most similar toC. aurita in its cranial shape. These findings indicate thatC. kuhli is most closely related toC. geoffroyi, whileC. flaviceps is toC. aurita.     

Mutualistic relationships between cohabiting tubificid species

Results from experiments with the three species constituting the dominant tubificid community of eutrophic lakes in Scandinavia, i.e. Tubifex tubifex, Limnodrilus hoffmeisteri and Potamothrix hammoniensis, suggested the involvement of mutualistic mechanisms. Previously Wavre & Brinkhurst, 1971; Brinkhurst, 1974 and McMurtry et al., 1983, described phenomena of this kind within a North American species complex involving T. tubifex and L. hoffmeisteri, as well.In mixed cultures, in comparison with monocultures of the respective species, I found that growth rate increased in the order of 50% and sexual maturity was reached earlier. Especially the three-species combinations rapidly increased in weight. Experiments with choice chambers, containing sediments enriched with the faecal pellets of each species alone or in species combinations, revealed specific reactions by the worms. As an average of three replicates, each starting with 45 recently hatched worms in equal proportions of the three species mentioned above, 14 chose the faeces of L. hoffmeisteri, 11 chose P. hammoniensis, 2 chose T. tubifex, 4 chose a combination of T. tubifex and L. hoffmeisteri and 4 chose blanks. Another 10 worms did not succeed in entering the choice chambers from the sandy substrate into which all worms were introduced and rapidly died off.The results seem to support the hypothesis that increased growth rate achieved in mixed cultures is due to each species selectively grazing concentrations of bacteria associated with the faeces of another species in the community. Earlier findings have shown that each species characteristically tends to cultivate only one species-specific bacterial strain at a time in its intestines (Wavre & Brinkhurst, 1971).Since the above species combination is by far the most frequently occurring oligochaete community in eutrophic lakes in Scandinavia and monocultures of any of the species involved are fairly uncommon under natural conditions, one may speculate that mixed cultures better utilize common available resources in accordance with experimental results.     

Functional relationships between dental attrition and the helicoidal plane

Several quantitative techniques were used to describe and analyze the development of the helicoidal curve of the dentition in a pre-contact sample of 326 native Indians from British Columbia. Results were compared with studies of occlusal patterns in other populations, and anatomical-functional features of the helicoidal pattern were abstracted and generalized. The features that define the helicoidal pattern were found to develop with attrition. The pattern itself, and the complex which produces it, probably have been selected for because they produce an occlusion with an efficient cutting edge and a total complex that provides maximum resistance to the masticatory forces. Studies focusing on the developmental nature of occlusal patterns in early hominid populations would be beneficial in developing a model of the evolution of the helicoidal pattern in modern man.     

Genetic relationships between some Tunisian Citrus species based on their leaf volatile oil constituents

Volatile oil constituents of Tunisian sweet orange (Citrus sinensis Osbeck) cv. Meski (MES), Valencia Late (VAL), Thomson Navel (THN) and Maltaise Blanc (MAB); mandarin (Citrus reticulata Blanco); sour orange (Citrus aurantium L. cv. Amara (AM)) and pummelo (Citrus grandis Osbeck) were obtained by hydrodistillation and analysed by gas chromatography (GC) combined with a flame ionisation detector (FID) and mass spectrometry (MS). A total of 41 components accounting for more than 95% of the total essential oils were identified, and oxygenated monoterpenes (69.5–99.9%) were found as the most prominent fraction in all oil samples. The main constituents were linalool (3.1–73%), isoborneol (0–55.8%) and tepinen-4-ol (1.1–19.2%). A high degree of inter-and intraspecific chemical variability between species and cultivars was found to be genetically determined, and a set of distinctive traits (chemical markers) in the essential oils profile was established. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) of all identified components grouped the oils into two main chemotypes (linalool/isoborneol and isoborneol/linalool).     

Grooming relationships between breeding females and adult group members in cooperatively breeding moustached tamarins (Saguinus mystax)

Grooming is the most common form of affiliative behavior in primates that apart from hygienic and hedonistic benefits offers important social benefits for the performing individuals. This study examined grooming behavior in a cooperatively breeding primate species, characterized by single female breeding per group, polyandrous matings, dizygotic twinning, delayed offspring dispersal, and intensive helping behavior. In this system, breeding females profit from the presence of helpers but also helpers profit from staying in a group and assisting in infant care due to the accumulation of direct and indirect fitness benefits. We examined grooming relationships of breeding females with three classes of partners (breeding males, potentially breeding males, (sub)adult non-breeding offspring) during three reproductive phases (post-partum ovarian inactivity, ovarian activity, pregnancy) in two groups of wild moustached tamarins (Saguinus mystax). We investigated whether grooming can be used to regulate group size by either "pay-for-help" or "pay-to-stay" mechanisms. Grooming of breeding females with breeding males and non-breeding offspring was more intense and more balanced than with potentially breeding males, and most grooming occurred during the breeding females' pregnancies. Grooming was skewed toward more investment by the breeding females with breeding males during the phases of ovarian activity, and with potentially breeding males during pregnancies. Our results suggest that grooming might be a mechanism used by female moustached tamarins to induce mate association with the breeding male, and to induce certain individuals to stay in the group and help with infant care.     

General relationships between species diversity and stability in competitive systems

Investigating the effect of biodiversity on the stability of ecological communities is complicated by the numerous ways in which models of community interactions can be formulated. This has led to differences in conclusions and interpretations of how the number of species in a community affects its stability. Here, we derive a simple, general relationship between the coefficient of variation (CV) of combined species densities and the environmentally driven variability in species' per capita population growth rates. For a given level of environmentally driven variability in per capita population growth rates, increasing the number of species in a community decreases the CV of combined species densities, provided that species do not respond to environmental fluctuations in a perfectly correlated way. Thus, a community with more species of competitors will be more stable (have lower CV in combined species densities for a given level of environmental variability) than a species-poor community, provided that the species in both communities show equal variability in per capita population growth rates and provided that species within each community do not show strongly correlated responses to environmental fluctuations. This conclusion also applies to "noninteractive" models in which there is no competition between species.     

香蕉上的镰孢菌种类及其系统发育关系(英文)

镰孢菌属真菌是香蕉上的重要病原菌,主要引起香蕉枯萎病以及香蕉冠腐病,在我国已明确引起香蕉枯萎病的病原为尖孢镰孢古巴专化型 Fusarium oxysporum f. sp. cubense(FOC)1号和4号生理小种,但是引起香蕉冠腐病的镰孢菌种类还未明确。为了解香蕉上镰孢菌在种间及种内水平上的多样性,2008–2011 年间作者从华南地区不同的水果市场及香蕉果园采集香蕉样品90份,分离得到143株镰孢菌。通过形态学观察及基于 EF-1α基因的系统进化分析鉴定出10种镰孢菌,即F. oxysporum、F. solani、F. camptoceras、F. pallidoroseum、F. stiloides、F. chlamydosporum、F.verticillioides、F. proliferatum、F. concentricum、F. sacchari,以及藤仓赤霉复合种(Gibberella fujikuroi species complex,GFC)中 3 个未定名的类群。轮纹镰孢 F. concentricum 及甘蔗镰孢 F.sacchari 是香蕉果实中最常见种,前菌为我国首次报道,后菌是首次报道与香蕉有关。对从香蕉上分离的藤仓赤霉复合种(GFC)及尖孢镰孢复合种(FOSC)的EF-1α序列进行了系统发育分析,其GFC中的27个菌株组成的单系群可分为7个不同的亚群,分别为 F.verticillioides、F. proliferatum、F. concentricum、F. sacchari 以及3个没有描述过的菌系 Fusarium sp. 1、Fusarium sp.2和 Fusarium sp.3;FOSC中的50个菌株形成2大分枝共12个谱系,分离自我国华南地区的21株尖孢镰孢形成7个谱系,其中 13株已知的香蕉枯萎病病原菌分布在3个谱系中,我国大陆的香蕉枯萎病病原菌菌株与来源于台湾地区及东南亚的菌株亲缘关系较近,FOC1号生理小种的遗传分化大于4号生理小种,FOC 1号生理小种与分离自香蕉果实上的尖孢镰孢菌的亲缘关系比与FOC 4号生理小种的亲缘关系更近。研究结果表明,我国香蕉上存在着丰富的镰孢菌种类,而且种内遗传多样性丰富。     

The ecology of seed dispersal in two species of callitrichid primates (Saguinus mystax and Saguinus fuscicollis)

Data collected during a 12-month field investigation of mixed species troops of Saguinus mystax and Saguinus fuscicollis in the Amazon Basin of north-eastern Peru indicate that callitrichid primates play an important role in tropical forest seed dispersal. Moustached and saddle-back tamarins were observed to ingest seeds from a variety of tree and liana species and pass them unharmed. These seeds tended to be large and heavy, and passed through the tamarin digestive tract in one to three hours. Experimental plantings of defecated seeds yielded a germination success rate of 70%. The specific gravity of these seeds (weight/volume) was inversely correlated with passage time and apparently had an indirect influence on the distance that seeds were dispersed from the parent tree. In the case of three preferred fruiting species, Leonia glycycarpa, Pourouma sp., and Hippocrateaceae #283, the present distribution of adult trees closely resembled the pattern of the seed shadow created by Saguinus. Moustached and saddle-back tamarins appeared to be reliable and high-quality dispersal agents for a number of tree and liana species. In this role, they are likely to exert an important influence on the composition, distribution, and regeneration patterns of Amazonian rain forest.     

Contrasting relationships between precipitation and species richness in space and time

Future changes in precipitation regimes are likely to impact species richness in water-limited plant communities. Regional, spatial relationships between precipitation and richness could offer information about how altered rainfall will impact local communities, assuming that processes driving the regional relationship are also dominant at fine spatial and short temporal scales. To test this assumption, we compared spatial and temporal relationships between precipitation and both species richness and species turnover in central North American grasslands. Across a broad geographic gradient, mean plant species richness in 1-m² plots increased significantly with mean annual precipitation. In contrast, over a 36-yr period at one mixed-grass prairie in the center of the regional gradient, single-year precipitation and richness were poorly correlated, and consecutive wet years had little effect on richness. Instead, richness increased most in wet years that followed dry years. Geographically dispersed sites receiving different levels of mean annual precipitation displayed strong differences in species composition, whereas temporal variation in precipitation at one site was not related to compositional dissimilarity, indicating that species turnover plays a key role in generating the regional relationship. Analyses of individual species' presence-absence suggest that the lagged temporal responses reflect environmental germination cues more than resource competition. These complex cues may dampen the initial impact of altered precipitation on diversity, but over the long term, turnover in species composition should lead to changes in richness, as in the regional, spatial relationship. How quickly this long-term response develops may depend on the colonization rates of species better adapted to the altered rainfall regime.     

Complex co-evolutionary relationships between cicadas and their symbionts

Previous evidence suggests that cicadas lacking Hodgkinia may harbour the yeast-like fungal symbionts (YLS). Here, we reinforce an earlier conclusion that the pathogenic ancestor of YLS independently infected different cicada lineages instead of the common ancestor of Cicadidae. Five independent replacement events in the loss of Hodgkinia/acquisition of YLS and seven other replacement events of YLS (from an Ophiocordyceps fungus to another Ophiocordyceps fungus) are hypothesised to have occurred within the sampled cicada taxa. The divergence time of YLS lineages was later than that of corresponding cicada lineages. The rapid shift of diversification rates of YLS and related cicada-parasitizing Ophiocordyceps began at approximately 32.94 Ma, and the diversification rate reached the highest value at approximately 24.82 Ma, which corresponds to the cooling climate changes at the Eocene–Oligocene boundary and the Oligocene–Miocene transition respectively. Combined with related acquisition/replacement events of YLS occurred during the cooling-climate periods, we hypothesise that the cooling-climate changes impacted the interactions between cicadas and related Ophiocordyceps, which coupled with the unusual life cycle and the differentiation of cicadas may finally led to the diversification of YLS in Cicadidae. Our results contribute to a better understanding of the evolutionary transition of YLS from entomopathogenic fungi in insects.     

Genetic relationships between Indians and their neighboring populations

Using gene frequency data for 18 protein and blood group loci, we studied the genetic relationships of four Indian subcontinent populations (peoples from Punjab, Gujarati, Andhra Pradesh, and Bangladesh) with their neighboring populations (Iranians, Afghans, Sinhalese in Sri Lanka, Nepalese, Bhutanese, Malays, Bataks in northern Sumatra, and Chinese). The results obtained indicate that the four Indian subcontinent populations and the Sinhalese are genetically closer to Iranians and Afghans (Caucasoid) than to the other neighboring Mongoloid populations. Genetic distance analysis shows a clear-cut dichotomy between the Caucasoid and Mongoloid populations.