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1.
Crataegus curvisepala Lindm., C. laevigata (Poiret) DC. and C. monogyna Jacq. (Rosaceae) form hybrid complexes in Denmark due to introgression. C. palmstruchii Lindm. seems to be variously introgressed individuals of C. laevigata. C. eremitagensis Raunk., C. raavadensis Raunk. and C. schumacheri Raunk. apparently belong to C. curvisepala x laevigata. The delimitation between C. curvisepala x laevigata and C. laevigata x monogyna is discussed.  相似文献   
2.
“Taxonomics” is proposed as a short name for the discipline of discovering, recognising, describing and classifying biological entities.  相似文献   
3.
Abstract — Based on published phylogenies for 73 groups of Holarctic non-marine animals, interrelationships between the four Holarctic infraregions (western and eastern Nearctic, western and eastern Palearctic) are examined. The study includes analysis of resolved area cladograms, ancestral areas and dispersal indicated by cladistic subordinateness. Area relationships reflecting present continental configurations (Nearctic vs. Palearctic) dominate the material to the extent that one might speak of a general Holarctic area pattern. Paleocontinental (western Nearctic+eastern Palearctic, western Palearctic+eastern Nearctic) and disjunct patterns are relatively more frequent among groups of higher taxonomic rank. The western Nearctic seems to have played a bigger role than the other infraregions as a center of origin. Two computer programs for constructing resolved area cladograms, viz., COMPONENT 1.5 and COMPONENT 2.0, are compared. The three standard assumptions for biogeographical analysis are compared and arguments are presented in favour of Assumption 0.  相似文献   
4.
The achievements of initiatives to strengthen biodiversity conservation in developing countries may be difficult to assess, since most countries have no system for monitoring biodiversity. This paper describes a simple and cost-effective, field-based biodiversity monitoring system developed specifically for areas where specialist staff is lacking. We discuss the preliminary lessons learned from protected areas in the Philippines. Whilst the monitoring system aims to identify trends in biodiversity and its uses so as to guide management action, it also promotes the participation of local people in the management, stimulates discussions about conservation amongst stakeholders and builds the capacity of park staff and communities in management skills. In addition, it seeks to provide people with direction regarding the aims of protected areas, and reinforces the consolidation of existing livelihoods through strengthening community-based resource management systems. The field methods are: (1) standardised recording of routine observations, (2) fixed point photographing, (3) line transect survey, and (4) focus group discussion. Both bio-physical and socio-economic data are used and given equal importance. The system can be sustained using locally available resources. The approach is useful in countries embarking on shared management of park resources with local communities, where rural people depend on use of natural ecosystems, and where the economic resources for park management are limited. We hope this paper will encourage other countries to develop their own biodiversity monitoring system, letting its development become a means for capacity building whilst at the same time supporting the creation of ownership.  相似文献   
5.
ZBARSKYIB 《Cell research》1998,8(2):99-103
The nonchromatin proteinous residue of the cell nucleus was revealed in our laboratory as early as in 1948 and then identified by light and electron microscopy as residual nucleoli,intranuclear network and nuclear envelope before 1960,This structure termed afterwards as “nuclear residue“,“nuclear skeleton“,“nuclear cage“,“nuclear carcass“etc.,was much later(in 1974) isolated,studied and entitled as “nuclear matrix“ by Berezney and Coffey,to whom the discovery of this residual structure is often wronly ascribed.The real history of nuclear matrix manifestation is reported in this paper.  相似文献   
6.
Urbanization, one of the most extreme land‐use alterations, is currently spreading, and the number of species confronting these changes is increasing. However, contradictory results of previous studies impede a clear interpretation of which selective pressure (nest predation or food limitation) is more important in urban habitats compared with natural situations, and whether birds can confront them by adjusting their life‐history strategies. We investigated life‐history syndromes of three common blackbird (Turdus merula) populations differing in their human influence (urban, rural, and woodland). We analysed daily nest predation and nestling starvation rates to assess the relative importance of these selection pressures in each habitat. Simultaneously, several life‐history traits were investigated to determine if T. merula seem adapted to their main source of selection. Food limitation was more important in the city, whereas nest predation was the most important selective force in the forest. The rural habitat was characterized by an intermediate influence of these two factors. Life‐history syndromes, as the covariation of a suite of traits, confirmed these results because T. merula seem well adapted to the main cause of selection in each habitat. Our results are consistent with urbanization imposing new challenges on birds, and that they adaptively respond to them. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 759–766.  相似文献   
7.
8.
Biodiversity monitoring is criticized for being insufficiently relevant to the needs of managers and ineffective in integrating information into decision-making. We examined conservation management interventions resulting from 2½ years of monitoring by 97 rangers and 350 community volunteers over 1 million hectares of Philippine protected areas. Before this monitoring scheme was established, there was little collaboration between local people and park authorities, and park monitoring was restricted to assessments of the quantity of extracted timber. As a result of the scheme, 156 interventions were undertaken in terrestrial, marine and freshwater ecosystems. In total 98% of these interventions were meaningful and justified, 47% targeted the three most serious threats to biodiversity at the site, and 90% were implemented without external support, suggesting that the interventions were relevant and could be sustained over time at the local level. The mean time from sampling to decision-making was only 97 days, probably because 82% of the interventions were initiated by the same people and institutions that had compiled the underlying data, bypassing potential government bureaucracy. Many of the interventions were jointly undertaken by community members and the management authorities or consisted of local bylaws in support of park management. As a result of the monitoring, indigenous resource use regulation schemes were re-established with government recognition in several parks. The monitoring led to more diversified and realistic management responses on the part of the authorities, including a more socially acceptable and effective approach to enforcement. Of the four field monitoring techniques used, the most participatory one generated more interventions aimed at ensuring a continued resource supply for local communities (χ23 = 69.1, p <0.01). Although this suggests that the interest of community members is associated with their possibilities to influence the flow of ecosystem goods and services, the 156 interventions targeted, directly or indirectly, all known globally threatened species of mammals, birds and butterflies in the parks.  相似文献   
9.

Background

The mismatch between dorsal and ventral trunk features along the millipede trunk was long a subject of controversy, largely resting on alternative interpretations of segmentation. Most models of arthropod segmentation presuppose a strict sequential antero-posterior specification of trunk segments, whereas alternative models involve the early delineation of a limited number of ‘primary segments’ followed by their sequential stereotypic subdivision into 2n definitive segments. The ‘primary segments’ should be intended as units identified by molecular markers, rather than as overt morphological entities. Two predictions were suggested to test the plausibility of multiple-duplication models of segmentation: first, a specific pattern of evolvability of segment number in those arthropod clades in which segment number is not fixed (e.g., epimorphic centipedes and millipedes); second, the occurrence of discrete multisegmental patterns due to early, initially contiguous positional markers.

Results

We describe a unique case of a homeotic millipede with 6 extra pairs of ectopic gonopods replacing walking legs on rings 8 (leg-pairs 10-11), 15 (leg-pairs 24-25) and 16 (leg-pairs 26-27); we discuss the segmental distribution of these appendages in the framework of alternative models of segmentation and present an interpretation of the origin of the distribution of the additional gonopods. The anterior set of contiguous gonopods (those normally occurring on ring 7 plus the first set of ectopic ones on ring 8) is reiterated by the posterior set (on rings 15-16) after exactly 16 leg positions along the AP body axis. This suggests that a body section including 16 leg pairs could be a module deriving from 4 cycles of regular binary splitting of an embryonic ‘primary segment’.

Conclusions

A very likely early determination of the sites of the future metamorphosis of walking legs into gonopods and a segmentation process according to the multiplicative model may provide a detailed explanation for the distribution of the extra gonopods in the homeotic specimen. The hypothesized steps of segmentation are similar in both a normal and the studied homeotic specimen. The difference between them would consist in the size of the embryonic trunk region endowed with a positional marker whose presence will later determine the replacement of walking legs by gonopods.  相似文献   
10.
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