Search results for "fragmentation"
showing 10 items of 798 documents
Genetic diversity and local population structure in Ambrosina bassii (Araceae, Ambrosineae), a Mediterranean relict species
2009
The effects of habitat fragmentation on the genetic structure of Ambrosina bassii are analyzed. The species, whose reproductive biology is mostly unknown, is the only representative of its genus and tribe and it is endemic to the central Mediterranean area. The selected study area was the island of Sicily, in which wild populations show a wide morphological variability and ecological amplitude. Patterns of within- and among-population genetic diversity in eleven Sicilian populations, occurring in six disjunct areas, were examined by means of allozyme electrophoresis. High levels of genetic diversity were found as shown by the mean expected heterozygosity (He ¼ 0.263), the percentage of poly…
Population Genetics, Parasitism, and Long-Term Population Dynamics of Microcebus murinus in Littoral Forest Fragments of South-Eastern Madagascar
2012
Habitat fragmentation is a major threat for lemur conservation, as it reduces population sizes to levels that are nonviable in the long term. Alternatively, isolated populations may have great importance for conservation, as some are well protected and some lemurs do well even in small areas. Hence, knowing which characteristics indicate a population under threat is of paramount importance for conservation action. We studied Microcebus murinus populations confined to forest fragments of different sizes and states of degradation in south-eastern Madagascar to investigate relationships between population size, population dynamics, genetic diversity of coding and noncoding DNA, and infection r…
Heart-targeted overexpression of caspase3 in mice increases infarct size and depresses cardiac function
2001
Up-regulation of proapoptotic genes has been reported in heart failure and myocardial infarction. To determine whether caspase genes can affect cardiac function, a transgenic mouse was generated. Cardiac tissue-specific overexpression of the proapoptotic gene Caspase3 was induced by using the rat promoter of α-myosin heavy chain, a model that may represent a unique tool for investigating new molecules and antiapoptotic therapeutic strategies. Cardiac-specific Caspase3 expression induced transient depression of cardiac function and abnormal nuclear and myofibrillar ultrastructural damage. When subjected to myocardial ischemia–reperfusion injury, Caspase3 transgenic mice showed increased inf…
Cellular and Morphological Traits of Oocytes Retrieved from Aging Mice after Exogenous Ovarian Stimulation1
2001
The present study aims to shed light on the origin of abnormal oocytes ovulated by aged females. In order to reach this goal, cellular and morphological traits of ovulated oocytes from hybrid (C57Bl/6JIco female x CBA/JIco male) female mice retrieved after exogenous ovarian stimulation at the age of 12, 40-42, 50-52, or 57-62 wk were analyzed. Aging of female mice was associated with 1) decreased number of ovulated oocytes; 2) increased percentage of cumulus-free oocytes; 3) raised percentage of oocytes with intracellular mitochondrial aggregates; 4) reduced percentage of oocytes displaying a normal distribution of chromosomes in the metaphase-II plate; 5) increased percentage of normal ooc…
No inbreeding depression but increased sexual investment in highly inbred ant colonies.
2012
Inbreeding can lead to the expression of deleterious recessive alleles and to a subsequent fitness reduction. In Hymenoptera, deleterious alleles are purged in haploid males moderating inbreeding costs. However, in these haplodiploid species, inbreeding can result in the production of sterile diploid males. We investigated the effects of inbreeding on the individual and colony level in field colonies of the highly inbred ant Hypoponera opacior. In this species, outbreeding winged sexuals and nest-mating wingless sexuals mate during two separate reproductive periods. We show that regular sib-matings lead to high levels of homozygosity and the occasional production of diploid males, which spo…
Inbreeding rate modifies the dynamics of genetic load in small populations
2012
The negative fitness consequences of close inbreeding are widely recognized, but predicting the long-term effects of inbreeding and genetic drift due to limited population size is not straightforward. As the frequency and homozygosity of recessive deleterious alleles increase, selection can remove (purge) them from a population, reducing the genetic load. At the same time, small population size relaxes selection against mildly harmful mutations, which may lead to accumulation of genetic load. The efficiency of purging and the accumulation of mutations both depend on the rate of inbreeding (i.e., population size) and on the nature of mutations. We studied how increasing levels of inbreeding …
Inbreeding, energy use and condition
2009
In energetic terms, fitness may be seen to be dependent on successful allocation of energy between life-history traits. In addition, fitness will be constrained by the energy allocation ability, which has also been defined as condition. We suggest here that the allocation ability, estimated as the difference between total energy budget and maintenance metabolism, may be used as a measure of condition. We studied this possibility by measuring the resting metabolic rate and metabolism during forced exercise in Gryllodes sigillatus crickets. To verify that these metabolic traits are closely related to fitness, we experimentally manipulated the degree of inbreeding of individuals belonging to t…
Territorial fragmentation in post-communist Romania: the not so curious case of a de-amalgamation reform
2021
Abstract The efficiency-driven trend towards amalgamation characterising local government reforms in Europe seems to have escaped Romania, which displays a significant increase in the number of local governments post-1989. This is the result of rural first-tier local governments splitting into smaller units. The paper examines objective factors and subjective motivations that have shaped the behaviour of both national and local actors in dealing with territorial reform. First, it explores the rationale and rationality of a central government initiative to facilitate municipal splits against a set of criteria derived from the literature. Second, it examines the municipal splits occurring bet…
Predation on artificial ground nests in relation to forest fragmentation, agricultural land and habitat structure
1996
The impacts of forest fragmentation, agricultural land and habitat structure on depredation of artificial ground nests were studied in the cultivated area in central Finland and in the forest dominated area in Finnish Lapland. The overall predation rate did not differ between the regions. The overall predation rate was also independent of landscape characteristics forest patch size and the distance to patch edge. However, nest predation was clearly affected by the agricultural land since the robbing rate in forest edges was higher near farmlands than further away. This effect was caused by avian predators which proportional importance in predation was higher in the agricultural landscape th…
Induction of apoptosis in the blue mussel Mytilus galloprovincialis by tri-n-butyltin chloride
2001
Induction of apoptosis by tri-n-butyltin (TBT) in gill tissue of the mussel Mytilus galloprovincialis was investigated. The terminal dUTP nick-end labeling technique (TUNEL) was used to detect cells displaying DNA fragmentation within gill structures. Genomic DNA fragmentation was detected as characteristically ladder-like pattern of DNA fragments induced by single injection of different doses of TBT (1-5 microg/g) below the mantle, directly into the pallial fluid, after 24 h of incubation. DNA degradation of higher order DNA structure, as well as reduced G(0)/G(1) cell cycle region (the sub-G(1) region) was detectable after 1.5 h of TBT incubation. Presence of apoptotic cells in mussels' g…