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1.
Hybridization, natural or artificial, is considered disadvantageous for species biodiversity when it threatens the population integrity of endangered species. Frequently, studies investigating whether hybridization poses a legitimate risk to rare species are based on genetic data obtained in molecular biology laboratories. In this study, we used field research to approach the problem that hybridization could cause for the viability of a population of a rare species and to be able to propose the most appropriate initial conservation strategy. Specifically, using the model genus Antirrhinum, the reproductive barriers between the rare A. pulverulentum and its common congener A. litigiosum have been analysed under the reproductive isolation index (RI). A. pulverulentum had a high value of total RI, indicating that there are barriers to gene flow from A. litigiosum towards this species, and also had a high value for the intrinsic RI, reflecting a low inherent capacity for production of hybrid plants; in addition, the possibility of successful backcrosses between this species with hybrids produced from A. litigiosum ovules were low, given the high intrinsic RI of A. litigiosum. These data indicate the current existence of strong and permanent barriers to hybridization between the two species, suggesting that hybridization does not seem to be a serious problem for the conservation of A. pulverulentum in the studied population, nor for the near future. This study shows how the RI index can provide useful information for conservation purposes and proposes different management recommendations. 相似文献
2.
We determined the incidence of curculionid beetles of the genus Lonchophorus on aborted and not aborted flower buds and developing fruits of the tree Ceiba pentandra in southeastern Costa Rica. Beetle larvae were found in reproductive parts of all trees sampled trees. The frequency of beetle
larvae was greater in aborted buds and immature fruits. A positive correlation between larvae development and flower bud development
indicates that female oviposition occurred in an early flower developmental stage and time until bud abortion is variable.
Weevil herbivory could be considered as one of the main factors that cause flower bud and fruit abortion in C. pentandra.
Resumen Determinamos la incidencia de curculiónidos del género Lonchophorus en botones florales y frutos inmaduros tanto abortados como no abortados en el árbol Ceiba pentandra en el SE de Costa Rica. Las larvas de curculiónidos fueron encontradas en todos los árboles muestreados. La frecuencia de larvas fue mayor en botones y frutos abortados. Una correlación positiva entre el desarrollo larval y el desarrollo del botón indica que la oviposición ocurre en una fase temprana de este y que el tiempo hasta el aborto es variable. La herbivoría por larvas de curculiónidos puede ser uno de los factores más importantes en el aborto de botones y frutos inmaduros en C. pentandra.相似文献
3.
Brian F. Bietz 《Environmental Biology of Fishes》1981,6(2):193-200
Synopsis Two forces, limited availability of preferred habitat and social attraction between conspecifics were hypothesized to explain nest aggregation in male longear sunfish. In the laboratory, males cluster their nests within a small segment of a much larger uniform area of nesting habitat. In the field, large areas of unused habitat suitable for nesting were found, suggesting that nesting aggregations are not formed as a result of limited preferred habitat. Males appear to be socially attracted during breeding, and social nesting presumably is a successful reproductive strategy for at least a portion of the population. 相似文献
4.
F J Stevens F A Westholm N Panagiotopoulos M Schiffer R A Popp A Solomon 《Journal of molecular biology》1981,147(1):185-193
A “naturally occurring” human κI VL dimer, designated Wat, has been isolated and crystallized. Protein Wat consists of two non-covalently bound monomers, each having a molecular weight of ~ 11,500. The monomer subunit is composed of an entire variable region light chain (VL) domain closely homologous to that of the κI Bence Jones protein Roy (Hilschmann &; Craig, 1965) as evidenced from amino acid composition, tryptic peptide map, and sequence analysis. Immunochemical studies substantiated that protein Wat is of the κ chain subgroup κI and lacks the isotypic and allotypic antigenic determinants associated with the κ constant region light chain domain. Two types of crystals of VL dimer Wat were obtained from ammonium sulfate or polyethylene glycol solutions. The type I crystals have unit cell dimensions of , and the space group is hexagonal P62 or P64. The asymmetric unit consists of one VL dimer; the fractional volume of unit cell occupied by solvent is 0.51. The unit cell dimensions of the type II crystals are ; the space group is hexagonal P6122 or P6522. Three variable domains constitute the asymmetric unit of the type II crystals; the fractional value of the solvent (0.52) is compatible with the value obtained for the type I crystals. 相似文献
5.
Eliab Estrada-Corts Hctor R. Vera-Avila Jorge Urrutia-Morales Eugenio Villagmez-Amezcua Hctor Jimnez-Severiano Csar A. Mejía-Guadarrama M. Teresa Rivera-Lozano Hctor G. Gmez-Vzquez 《Animal reproduction science》2009,116(3-4):282-290
The objective was to determine the effect of body energy stores, evaluated by a body mass index (BMI), and food intake (FI), on the length of the anovulatory period and ovarian activity during the seasonal reproductive transitions in Creole goats. Non-pregnant, non-lactating Creole goats (n = 28) were fed to induce two different BMI conditions: Greater (GBMI; n = 15), and Lesser (LBMI; n = 13). Each BMI group was divided into two sub-groups, which were either feed restricted (FR) or non-feed restricted (NFR). Goats in the NFR groups received a diet containing 100% of the daily maintenance requirements (basal diet), while restricted goats were subjected to alternated periods, receiving 100% (11 d) and 60% (10 d) of the basal diet, during the entire experimental period. The experiment started after does were treated to synchronize time of estrus. Serum progesterone was determined in samples obtained twice a week, and used as a criterion for determining ovulations. During the transition to the anovulatory period three transrectal ovarian ultrasonographic scans were performed in a sub-group of 12 goats (n = 3 for each treatment combination). The diameter of the largest follicle (LFD) and the total number of antral follicles ≥2 mm (TAF) were recorded. Ultrasonographic ovarian scans were performed at 21, 42 and 63 days after the beginning of the experiment, concurrently with the end of each feed restriction period. The variables of response associated with ovulation were not influenced by BMI or BMI × FI interaction. However, FI influenced length of anovulatory season, as the anovulatory period was 30 d longer (P < 0.05) in the FR group as compared with the NFR group. Independently of treatments, TAF and LFD decreased from the first to the third ultrasonographic ovarian scan (13.2, 10.8 and 4.4 follicles; 3.7, 2.7 and 2.3 mm). Nevertheless, in PER 1 the number of TAF was greater (P < 0.05) in the FR as compared with NFR group and the GBMI group had a larger LFD (P < 0.05) as compared to the LBMI group. It is concluded, that temporal restriction in feed intake could affect the time of cessation and initiation of ovulations during the periods of transition to seasonal anestrus and return to estrous activity, and increase the length of the anovulatory period. In addition, ovarian follicular development during transition into the anovulatory period is differentially influenced by food intake and the status of body energy stores. 相似文献
6.
The debate about the biological species concept - a review 总被引:1,自引:0,他引:1
C. L. HÄUSER 《Journal of Zoological Systematics and Evolutionary Research》1987,25(4):241-257
The importance of the species concept in biology has led to a continuing debate about the definition of species. This paper summarizes the recent literature in relation to the ‘biological species concept’ (MAYR 1942). Among the general attributes demanded, possible limitations of the universality and applicability of a species definition are discussed. Three different areas of criticism of the biological species concept are considered: 1. The impracticability of the criterion of reproductive isolation. The demand for more practical criteria is rejected, because reproductive isolation is seen as the factor that produces and maintains species as discrete entities in nature. 2. The inapplicability to non-bisexual organisms. A brief survey of modes of uniparental reproduction and their relative importance suggests that obligatory apomicts are of little evolutionary significance. 3. The inapplicability to multidimensional situations. Despite practical difficulties, the biological species concept is held to apply to organisms separated in space. The impossibility to delimit species in time by reproductive isolation is recognized. Out of two ways to divide continuous evolutionary lineages in time, the phylogenetic approach, which considers only speciation events (cladogenesis), is preferred as it is more objective. A list of recently published alternative definitions of species, none of which is found acceptable, is given. It is concluded that the biological species concept needs not be changed or dismissed on the basis of the discussed criticisms. 相似文献
7.
Daniel Pérusse 《Human nature (Hawthorne, N.Y.)》1994,5(3):255-278
Most research on mate choice in modern societies is based on data that may or may not reflect actual mating behavior (e.g.,
stated preferences, personal advertisements). In the present study, real-life matings were reported by a large representative
sample of men and women (N = 1,133). These data were used to test an evolutionary model in which mate choice is hypothesized to depend on resources
potentially contributed to reproduction by each sex. Consistent with the model, it was found that (a) men (but not women) of higher social status acquire more mating partners, suggesting that male status is an important criterion
in female choice; (b) women’s (but not men’s) number of partners decreases linearly with age, suggesting that female reproductive potential is
an important criterion in male choice; and (c) women (but not men) display a significant relationship between marital dissolution and promiscuity, suggesting that female
sexual exclusivity is an important criterion in male choice. These results are discussed in relation to understanding mate
choice mechanisms from behavioral data.
Daniel Pérusse is an assistant professor in the Department of Anthropology at the Université de Montréal. His research interests
include the evolutionary biology of human social and reproductive behavior, sexual selection theory, and biocultural evolution.
His current research bears on human socialization processes and psychosocial development from an evolutionary and behavior-genetic
perspective. Recent publications include “Cultural and Reproductive Success in Industrial Societies: Testing the Relationship
at the Proximate and Ultimate Levels” (Behavioral and Brain Sciences 16(2):267–322, 1993) and “Human Parental Behavior: Evidence for Genetic Influence and Potential Implications for Gene-Culture
Theory” with M. C. Neale, A. Heath, and L. J. Eaves (Behavior Genetics, in press). 相似文献
8.
The muscle phase of Trichinella spiralis and of Trichinella sp. isolated in the Arctic was compared in experimental and wild animals. Reproductive capacity indices (RCI) of the Trichinella sp. isolate were significantly lower in laboratory rodents but were similar to T. spiralis in wild rodents. Sprague-Dawley rats were the most refractory to the Trichinella sp. isolate of all laboratory rodents. Outbred strains of mice were more susceptible to both T. spiralis and the Trichinella sp. isolate than inbred strains of mice. T. spiralis muscle larvae survived longer in mice and the survival of both T. spiralis and the Trichinella sp. isolate larvae was higher in female mice. While single pair interbreeding experiments showed reproductive isolation between T. spiralis and the Trichinella sp. isolate, multiple pair and transplant breeding experiments showed reproductive compatibility. Male and female infective larvae of T. spiralis and the Trichinella sp. isolate differed morphometrically, but a convergence in size of worms was observed after prolonged passages of the parasites in mice. Passaging history of the isolate and host species was found to have a significant effect on Trichinella morphology. It is proposed that the Trichinella sp. isolate is a physiological variant of T. spiralis and not a distinct species. 相似文献
9.
O A Otubanjo 《Experimental parasitology》1981,52(2):161-170
Astiban produced structural damage in male Schistosoma mansoni (Puerto Rican strain) in mice. The degree of disorganization was directly related to the dosage administered, although initial changes in structure for the first three doses (3 × 30–40 mg/kg) varied between individual worms of the same infection. More consistent damage to the tegument, parenchyma, and reproductive organs occurred after 6 × 40 mg/kg of Astiban injections. Exposure of the subtegumentary musculature preceded appearance of an increased number of noncytoplasmic spaces in various tissues, probably a result of osmotic stress. Testicular disorganization was prominent initially in spermatozoa and spermatids, but became more generalized with drug accumulation. The sustentacular cells showed increased phagocytic activity with testicular damage. Continuous administration of drug resulted in a general distortion of the worm's morphology. However, partial recovery occurred within 22 days following cessation of drug administration. 相似文献
10.
Notes on compositional diversity 总被引:5,自引:4,他引:1
Pál Juhász-Nagy 《Hydrobiologia》1993,249(1-3):173-182
This paper tries to show some ways and means of simple (binary) modelling, whereby diversity can be interconnected with other attributes of a community. A new type of scaling (called characteristic scaling) is introduced for further use. 相似文献