Reduction In Natural Populations Research Articles

Gene-flow investigation between garden and wild roses planted in close distance.

Rose is a major ornamental plant, and a lot of cultivars with attractive morphology, color and scent have been generated by classical breeding. Recent progress of genetic modification produces a novel cultivar with attractive features. In both cases, a major problem is the gene-flow from cultivated or genetically modified (GM) plants to wild species, causing reduction of natural population. To investigate whether gene-flow occurs in wild species, molecular analysis with DNA markers with higher efficient technique is useful. Here we investigated the gene-flow from cultivated roses (Rosa×hybrida) to wild rose species planted in close distance in the field. The overlapping flowering periods and visiting insects suggest that pollens were transported by insects between wild and cultivated roses. We examined the germination ratio of seeds from wild species, and extracted DNA and checked with KSN and APETALA2 (AP2) DNA markers to detect transposon insertions. Using two markers, we successfully detected the outcross between wild and cultivated roses. For higher efficiency, we established a bulking method, where DNA, leaves or embryos were pooled, enabling us to that check the outcross of many plants. Our results suggest that wild species and garden cultivars can cross in close distance, so that they should be planted in distance, and checked the outcross with multiple DNA markers.

Amphipterygium adstringens (Schltdl.) Schiede ex Standl (Anacardiaceae): An Endemic Plant with Relevant Pharmacological Properties.

Diseases, such as cancer, peptic ulcers, and diabetes, as well as those caused by drug-resistant infectious agents are examples of some of the world’s major public health problems. Amphipterygium adstringens (Schltdl.) Schiede ex Standl is an endemic tree to Mexico. Its stem bark has been used medicinally since pre-Hispanic times, but in recent decades it has been scientifically proven that it has properties that help counteract some diseases; extracts with organic solvents of the plant are outstanding for their anticancer, gastroprotective, and antimicrobial properties; terpenes and long-chain phenols have been identified as the main active compounds. Currently, overharvesting is causing a sharp reduction in natural populations due to an increase in demand for the stem bark by people seeking to improve their health and by national and transnational companies seeking to market it. Because of the growing interest of the world population and the scientific community, we reviewed recent studies on the bioactive properties of A. adstringens. Through the orderly and critical compendium of the current knowledge of A. adstringens, we provide a reference for future studies aimed at the rational use and protection of this valuable endemic natural resource.

Computational characterization of double reduction in autotetraploid natural populations.

Population genetic theory has been well developed for diploid species, but its extension to study genetic diversity, variation and evolution in autopolyploids, a class of polyploids derived from the genome doubling of a single ancestral species, requires the incorporation of multisomic inheritance. Double reduction, which is characteristic of autopolyploidy, has long been believed to shape the evolutionary consequence of organisms in changing environments. Here, we develop a computational model for testing and estimating double reduction and its genomic distribution in autotetraploids. The model is implemented with the expectation-maximization (EM) algorithm to dissect unobservable allelic recombinations among multiple chromosomes, enabling the simultaneous estimation of allele frequencies and double reduction in natural populations. The framework fills an important gap in the population genetic theory of autopolyploids.

Is lower intensity aquaculture a valuable means of producing food? An evaluation of its effects on near‐shore and inland waters

AbstractThe effects of aquaculture on the environment have been the subject of much examination, but most of the focus has been on shrimp and salmon. These are not the most common species grown in aquaculture, nor the most common systems used. About 60% of production today uses lower intensity culture to produce organisms in natural systems such as ponds. This paper is an overview of the positive and negative environmental impacts of lower intensity aquaculture. The ranked positive impacts of lower intensity aquaculture include: conservation aquaculture that supplements reproduction in natural populations; improving the quality of natural waters through filtering or consuming wastes by cultured organisms; reducing pressure on wild stocks by providing alternative sources in the market; and replacing damaging employment with more sustainable aquaculture jobs. Negative impacts include: escapement of alien species that become invasive; eutrophication of receiving waters from pond effluents; release of parasites and diseases into natural communities; escapement of unique genotypes resulting in genetic alteration of native stocks; land degradation due to pond construction; release of antibiotics or other drugs into receiving waters; depletion of natural resources such as water; loss of benthic biodiversity from settling of sediments; and reductions in natural populations by collection of larval or juvenile fish. Some impacts, especially the use of fishmeal and the transmission of disease, are much less common in lower intensity aquaculture systems. Aquaculture has an important role in current and future food production, and in many cases lower intensity aquaculture provides a sustainable solution to increased aquaculture production.

Genetic diversity of Annona crassiflora (Annonaceae) in northern Minas Gerais State

Genetic diversity analyses of tropical tree species are relevant to landscape management, plant genetic resource inventory, and biological conservation of threatened species. Annona crassiflora is an endangered fruit tree native to the Cerrado biome that is threatened by reduction of natural populations and fruit extraction. We examined the intra- and interpopulational genetic diversity of this species in the northern region of Minas Gerais State. Seventy-two individuals from four natural populations were genotyped using RAPD markers. We found moderate genetic diversity among populations, with Shannon's I index varying between 0.31 and 0.44, and Nei's genetic diversity (H(E)) for the population set equal to 0.31. AMOVA indicated a greater genetic variation within (77.38%) rather than among populations (22.62%), tending towards isolation by distance (Mantel's r = 0.914; P = 0.089). Nei's genetic identity estimates among populations revealed a hierarchical pattern of genetic similarity of form [(CA1, CA2), MC], [(GM)], corroborating the high genetic differentiation between spatially isolated populations.

The influence of infaunal ( Nereis diversicolor) abundance on degradation of organic matter in sandy sediments

The influence of the infaunal polychaete Nereis diversicolor on the degradation of aged detritus ( Fucus sp.) deposited 3 cm below the sediment surface was investigated as a function of worm density (0, 600, 1200 and 2400 m − 2 ) in manipulated laboratory microcosms. Benthic metabolism in the microcosms was determined as sediment–water fluxes of dissolved carbon and microbial sulfate reduction. In addition, the vertical distribution of key sediment parameters, such as porewater solutes and bacterial abundance and community fingerprint (based on 16S rDNA) were determined at the end of the experimental period. Porewater concentrations of TCO 2, DOC, and NH 4 + were negatively related to worm density as a result of irrigation mediated excess transport. Conversely, sediment–water fluxes increased linearly with increasing macrofaunal abundance. Total benthic metabolism (TCO 2 and O 2 flux) was stimulated by up to 75% in unamended and 175% in detritus enriched treatments. The high faunal stimulation of benthic metabolism in the Fucus enriched sediment was primarily due to increased aerobic microbial metabolism resulting in a more efficient mineralisation of the released DOC and thus faster decay of the aged detritus. Sediment bacteria in the detritus amended treatment seemed to rapidly assimilate NH 4 + within the sediment when utilising the added nitrogen-deficient detritus. NH 4 + fluxes were similar in both amended and unamended treatments but increased with animal density, suggesting that animal excretion contributed significantly to the NH 4 + flux. Analysis of the bacterial community showed that the addition of detritus significantly changed both its abundance and composition compared to unamended treatments. These differences were gradually alleviated with increasing animal abundance. Our results show that N. diversicolor abundance is a significant factor that determines not only total benthic metabolism, but also organic matter degradation pathways and microbial community composition, and a possible reduction of natural populations would result to changes in sediment biogeochemistry.

Genetic and developmental basis of evolutionary pelvic reduction in threespine sticklebacks.

Hindlimb loss has evolved repeatedly in many different animals by means of molecular mechanisms that are still unknown. To determine the number and type of genetic changes underlying pelvic reduction in natural populations, we carried out genetic crosses between threespine stickleback fish with complete or missing pelvic structures. Genome-wide linkage mapping shows that pelvic reduction is controlled by one major and four minor chromosome regions. Pitx1 maps to the major chromosome region controlling most of the variation in pelvic size. Pelvic-reduced fish show the same left-right asymmetry seen in Pitx1 knockout mice, but do not show changes in Pitx1 protein sequence. Instead, pelvic-reduced sticklebacks show site-specific regulatory changes in Pitx1 expression, with reduced or absent expression in pelvic and caudal fin precursors. Regulatory mutations in major developmental control genes may provide a mechanism for generating rapid skeletal changes in natural populations, while preserving the essential roles of these genes in other processes.

The implications of poaching for giant panda conservation

Poaching giant pandas (Ailuropoda melanoleuca) for their skins is a serious threat to the persistence of wild giant panda populations in China. An individual-based, age-structured stochastic simulation model was constructed to give a quantitative analysis of the effects of poaching. The model takes a total wild population of 1216 individuals divided among 16 ‘patches’. The model treats individual populations as being completely independent, with no dispersal, and density-dependence only enters into the model through local carrying capacity of patches. The model simulates three types of poaching: deterministic (constant) poaching, stochastic poaching with normal distribution and stochastic poaching with observed distribution. Results showed that, with a given initial population, poaching adult females produces lower average population size and higher average percentage extinction than poaching adult males or young. At the same poaching intensity, all three poaching simulations predicted a similar probability of extinction. However, they predicted different average population size and percentage extinction because of differences in the parameters in the three models. These results should therefore be treated with caution when constant poaching simulation or stochastic poaching with assumed normal distribution is used as a simplification of realistic poaching. Nevertheless, the results imply that giant pandas are threatened by any reduction in natural populations. Effective measures are essential to reduce poaching. It is also important to limit the capturing of wild animals for zoos or breeding facilities as this also has a serious effect on the total population.

Use of size‐dependent mortality models to estimate reductions in fish populations resulting from toxicant exposure

AbstractIn populations in which the rate of early mortality depends primarily on the size of individuals, growth and size become important determinants of population dynamics. Models based on size and developed for fish populations can provide a means of integrating acute and chronic toxicological observations to predict changes in population size. These models predict population reductions resulting from lethality to eggs and larvae, reduced growth rate, reduced length at hatch and any behavioral or physiological changes that increase either size‐dependent or size‐independent mortality rates. The dependence of mortality rate on size may arise from developmental changes, size‐selective predation, changing energy balances or a combination of these. The biological source of mortality may dictate its mathematical expression. Since the size‐dependent mortality modeled here may arise from several common sources, it may be widespread. As a result, reductions in natural populations caused by sublethal toxic exposures may not be unusual. These results suggest that measuring sublethal reductions in early growth that result from toxic conditions may be a meaningful way of estimating potential risks to natural populations.

Complex Y-linked translocations in Delia antiqua produced by irradiation of a fertile Y-linked translocation.

In the onion fly, Delia antiqua, a fertile, Y-linked translocation involving chromosomes Y and 2 was irradiated with fast neutrons to induce new complexes involving the Y-chromosome. This chromosome is male determining in the onion fly. Such complexes can be used for the development of genetic sexing systems and also for the introduction of sterility into field populations following release. Irradiation reduced egg fertility by 54 per cent and significantly reduced larval survival but it had no effect on the F1 sex ratio. By measuring the fertility of 807 F1 males following outcrossing, 112 semi-sterile progenies were isolated of which 11 were lost, 29 showed no inheritance of the semi-sterility, 59 were new autosomal translocations and 13 were new complex Y-linked translocations. This classification was accomplished by checking the fertilities of outcrossed F2 males and females. Following cytological observation it was revealed that one of these new complexes involved four chromosome pairs, the remainder involved three. There appeared to be no correlation between the fertility of the translocation and the complexity of the rearrangement. The utilization of these rearrangements in the development of the genetic sexing technique for the onion fly is discussed, together with an assessment of their use for fertility reduction in natural populations.

Efficiency and Effective Radius of Blacklight Traps Against Southern Potato Wireworm12

A reported technique for using water pans to determine efficiency of backlight (BL) traps was modified for studies of Conoderus falli Lane. In tests during 1969–71, the effective radius of a 15-watt BL lamp in a survey-type trap conforming to Entomological Society of America standards was estimated at 17–23 feet. The average efficiency of the trap in capturing insects within the effective radius was estimated at 28–62%. When isolated BL traps were operated 36 to 44 nights, no effect on the population could be attributed to distances beyond 35 to 53 feet from the light. It is estimated that at least 5 traps per acre would be required to cause a marked reduction in natural populations of southern potato wireworm.