Feral Populations (feral + population)

Distribution by Scientific Domains


Selected Abstracts


THE AFRICANIZATION OF HONEYBEES (APIS MELLIFERA L.) OF THE YUCATAN: A STUDY OF A MASSIVE HYBRIDIZATION EVENT ACROSS TIME

EVOLUTION, Issue 7 2002
Kylea E. Clarke
Abstract Until recently, African and European subspecies of the honeybee (Apis mellifera L.) had been geographically separated for around 10,000 years. However, human-assisted introductions have caused the mixing of large populations of African and European subspecies in South and Central America, permitting an unprecedented opportunity to study a large-scale hybridization event using molecular analyses. We obtained reference populations from Europe, Africa, and South America and used these to provide baseline information for a microsatellite and mitochondrial analysis of the process of Africanization of the bees of the Yucatan Peninsula, Mexico. The genetic structure of the Yucatecan population has changed dramatically over time. The pre-Africanized Yucatecan population (1985) comprised bees that were most similar to samples from southeastern Europe and northern and western Europe. Three years after the arrival of Africanized bees (1989), substantial paternal gene flow had occurred from feral Africanized drones into the resident European population, but maternal gene flow from the invading Africanized population into the local population was negligible. However by 1998, there was a radical shift with both African nuclear alleles (65%) and African-derived mitochondria (61%) dominating the genomes of domestic colonies. We suggest that although European mitochondria may eventually be driven to extinction in the feral population, stable introgression of European nuclear alleles has occurred. [source]


Development of the herbivore Pieris rapae and its endoparasitoid Cotesia rubecula on crucifers of field edges

JOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2006
J. A. Harvey
Abstract:, Several studies have reported that flowering herbs, which grow naturally or are sown adjacent to agricultural fields, may be an important source of nutrients for natural enemies. Many parasitoids readily feed on plant exudates such as floral nectar, which contain different types of sugars that enable the insects to optimize their longevity, mobility and reproductive success. However, leaf tissues of plants grown in the margins of agricultural fields may also provide food for immature stages of insect herbivores, such as caterpillars, that are in turn attacked by parasitoids. Herbivores and their parasitoids may later disperse into the crop, so the nutritional quality of surrounding plants, as this affects herbivore and parasitoid fitness, may also influence the success of biological control programmes, especially later in the season. Here, we compare the suitability of three species of cruciferous plants (Brassicaceae) on the development of Pieris rapae L. (Lep., Pieridae) and its solitary endoparasitoid, Cotesia rubecula Marshall (Hym., Bracondiae). Insects were reared on a feral population of cabbage, Brassica oleracea, on radish Raphanus sativus, which is widely sown in agricultural margins, and on hedge mustard, Sisymbrium officinale, a wild crucifer which often grows in medium to large stands along road verges and field edges. Development time in both the herbivore and parasitoid were extended on R. sativus, compared with the other two species, whereas C. rubecula completed its development most rapidly on B. oleracea. Moreover, adult butterflies and parasitoids were significantly smaller when reared on R. sativus plants. Our results reveal that differences in the quality of plants growing adjacent to agricultural fields can affect the development of key herbivores and their parasitoids. This should be borne in mind when establishing criteria for the selection of floral biodiversity. [source]


Growth and ageing of feral Xenopus laevis (Daudin) in South Wales, U.K.

JOURNAL OF ZOOLOGY, Issue 4 2001
G. J. Measey
Abstract A feral population of African clawed frogs Xenopus laevis from a small pond in South Wales was sampled continuously for 2 years to assess morphometric growth. Toe-clips taken at intervals over a 4-year period were found to contain lines of arrested growth (LAG) which corresponded to each consecutive winter. The first toe-clips revealed a population structure within the pond consisting of a dominant cohort of frogs with one LAG that metamorphosed in 1993, and a few older individuals. Subsequent toe-clips in 1996 and 1998 gave two and four more LAG, respectively. Morphometric growth was found to be restricted to a short growing season, significant differences in the growth rates of males and females being first detected in their third growth season. Reproductively active frogs were still within their initial period of growth, suggesting that Xenopus laevis does not conform to the standard energy resource allocation mechanisms of typical ectotherms. [source]


Where do the feral oilseed rape populations come from?

JOURNAL OF APPLIED ECOLOGY, Issue 2 2008
A large-scale study of their possible origin in a farmland area
Summary 1Many cultivated species can escape from fields and colonize seminatural habitats as feral populations. Of these, feral oilseed rape is a widespread feature of field margins and roadside verges. Although considered in several studies, the general processes leading to the escape and persistence of feral oilseed rape are still poorly known. Notably, it remains unclear whether these annuals form transient populations resulting mainly from seed immigration (either from neighbouring fields or during seed transport), or whether they show real ability to persist (either through self-recruitment or seed banks). 2We conducted a 4-year large-scale study of factors involved in the presence of feral oilseed rape populations in a typical open-field area of France. The results were subjected to statistical methods suitable for analysing large data sets, based on a regression approach. We subsequently addressed the relative contribution of the ecological processes identified as being involved in the presence of feral populations. 3Many feral oilseed rape populations resulted from seed immigration from neighbouring fields (about 35,40% of the observed feral populations). Immigration occurred at harvest time rather than at sowing. Around 15% of such populations were attributed to immigration through seed transport. 4The other half resulted from processes of persistence, mainly through persistent seed banks (35,40% of the observed feral populations). This was all the more unexpected because seed banks have not yet been documented on road verges (despite being frequent within fields). Local recruitment was rare, accounting for no more than 10% of the feral populations. 5Synthesis and applications. Understanding the dynamics of feral oilseed rape populations is crucial for evaluating gene flow over an agro-ecosystem. Our results show that, while many feral populations do come from annual seed dispersal, a significant number also result from seeds stored in the soil for several years. In the current context of coexistence and management of transgenic with non-transgenic crops, feral persistence and, especially, the seed bank contribution to the dynamics of feral populations need to be considered seriously. The latter, combined with self-recruitment, indicates a high potential for the persistence of transgenes and the possible emergence of gene-stacking. [source]


The impacts of non-native species on UK biodiversity and the effectiveness of control

JOURNAL OF APPLIED ECOLOGY, Issue 5 2000
Sarah J. Manchester
1.,The introduction of non-native species continues to cause ecological concern globally, but there have been no published reviews of their effects in the UK. Impacts in the UK are therefore reviewed, along with current legislation and guidelines relating to the introduction and control of such species. 2.,A large number of non-native species have been introduced to the UK, both deliberately and accidentally, but only a small number of introduced non-native species have established and caused detrimental ecological impacts. However, general declines in UK biodiversity, and the potential effects of future climate change, may increase the susceptibility of ecosystems to invasions. 3.,Detrimental impacts of non-native species on native biota have occurred through competition, predation, herbivory, habitat alteration, disease and genetic effects (i.e. hybridization). There are potential effects on genetic biodiversity as well as species biodiversity. 4.,Several high profile examples highlight the technical difficulties, and financial implications, of removing an introduced species once it is established. Few UK control or eradication programmes have been successful. 5.,Control might be more feasible if ,problem' species could be identified at an earlier stage of establishment. However, the poor success of attempts to characterize invasive species and predict which will have negative impacts highlight the individual and unpredictable nature of invasions. The difficulties of making general predictions suggest that every proposed species introduction should be subject to rigorous ecological characterization and risk assessment prior to introduction. 6.,The plethora of UK legislation and guidelines developed to reduce impacts of non-native species only go part of the way towards ameliorating impact. Many species already established in the wild might cause future problems. Illegal releases and escapes of non-native species may augment feral populations or establish new colonies. While regulation of imports and releases is important, further enforcement of existing legislation and action against unlicensed releases is necessary. [source]


Genetic quality of domesticated African tilapia populations

JOURNAL OF FISH BIOLOGY, Issue 2004
R. E. Brummett
Anecdotal and empirical evidence exists for substantial (up to 40%) declines in growth among Oreochromis populations domesticated in both large and small-scale fish farms in Africa. These declines are at least partly attributable to poor genetic management, including inadvertent selection, inbreeding, bottle-necks and founder effects. Due to restricted cash flow and investment capital, genetic management and selective breeding for the improvement of domesticate populations are difficult for small-scale farmers, but feasible on larger-scale farms. In managing domesticated gene pools, feral populations can serve as a broodstock reservoir, making the use of indigenous species advantageous. A development model of large-scale hatcheries producing selected lines of sex-reversed, indigenous tilapia for sale to smaller-scale farmers is proposed as a solution to the problems of poor genetic management in African aquaculture. [source]


Origin of honeybees (Apis mellifera L.) from the Yucatan peninsula inferred from mitochondrial DNA analysis

MOLECULAR ECOLOGY, Issue 6 2001
Kylea E. Clarke
Abstract Honeybees (Apis mellifera L.) sampled at sites in Europe, Africa and South Ámerica were analysed using a mitochondrial DNA restriction fragment length polymorphism (RFLP) marker. These samples were used to provide baseline information for a detailed analysis of the process of Africanization of bees from the neotropical Yucatan peninsula of Mexico. Radical changes in mitochondrial haplotype (mitotype) frequencies were found to have occurred in the 13-year period studied. Prior to the arrival of Africanized bees (1986) the original inhabitants of the Yucatan peninsula appear to have been essentially of southeastern European origin with a smaller proportion having northwestern European ancestry. Three years after the migration of Africanized bees into the area (1989), only very low levels of maternal gene flow from Africanized populations into the resident European populations had occurred. By 1998, however, there was a sizeable increase in the proportion of African mitotypes in domestic populations (61%) with feral populations having 87% of mitotypes classified as African derived. The results suggest that the early stages of Africanization did not involve a rapid replacement of European with African mitotypes and that earlier studies probably overestimated the prevalence of African mitotypes. [source]


Which traits promote persistence of feral GM crops?

OIKOS, Issue 1 2005
Part 1:implications of environmental stochasticity
Transgenes in plants affect life history traits including seed survival and germination. With stochastic matrix models we predict population-level consequences of transgene induced life history changes. We assess systematically which changes in life history traits, resulting from genetic modification, may increase the risk of invasion and persistence of feral crops or increase fitness in case of introgression from arable fields into conspecific, feral populations. We apply our method to feral populations of oilseed rape. Like many annual weeds, oilseed rape depends critically on disturbance; in undisturbed habitats it is generally outcompeted by perennials. The associated inherent variability and unpredictability render deterministic models inappropriate. With a stochastic matrix model we study population growth rate, elasticities and quasi-extinction times. Our results indicate that changes in survival in the seed bank impact population growth and persistence most. Less important are dormancy, fecundity and seedling survival. The predicted distribution of extinction times is highly skewed, with some patches persisting for decades. [source]


Which traits promote persistence of feral GM crops?

OIKOS, Issue 1 2005
Part 2: implications of metapopulation structure
Transgenes may spread from crops into the environment via the establishment of feral populations, often initiated by seed spill from transport lorries or farm machinery. Locally, such populations are often subject to large environmental variability and usually do not persist longer than a few years. Because secondary feral populations may arise from seed dispersal to adjacent sites, the dynamics of such populations should be studied in a metapopulation context. We study a structured metapopulation model with local dispersal, mimicking a string of roadside subpopulations of a feral crop. Population growth is assumed to be subject to local disturbances, introducing spatially random environmental stochasticity. Our aim is to understand the role of dispersal and environmental variability in the dynamics of such ephemeral populations. We determine the effect of dispersal on the extinction boundary and on the distribution of persistence times, and investigate the influence of spatially correlated disturbances as opposed to spatially random disturbances. We find that, given spatially random disturbances, dispersal slows down the decline of the metapopulation and results in the occurrence of long-lasting local populations which remain more or less static in space. We identify which life history traits, if changed by genetic modification, have the largest impact on the population growth rate and persistence times. For oilseed rape, these are seed bank survival and dormancy. Combining our findings with literature data on transgene-induced life history changes, we predict that persistence is promoted by transgenes for oil-modifications (high stearate or high laurate) and, possibly, for insect resistence (Bt). Transgenic tolerance to glufosinate herbicide is predicted to reduce persistence. [source]


Indigenous domestic breeds as reservoirs of genetic diversity: the Argentinean Creole cattle

ANIMAL GENETICS, Issue 5 2001
G. Giovambattista
Contrary to highly selected commercial breeds, indigenous domestic breeds are composed of semi-wild or feral populations subjected to reduced levels of artificial selection. As a consequence, many of these breeds have become locally adapted to a wide range of environments, showing high levels of phenotypic variability and increased fitness under natural conditions. Genetic analyses of three loci associated with milk production (,S1 -casein, , -casein and prolactin) and the locus BoLA-DRB3 of the major histocompatibility complex indicated that the Argentinean Creole cattle (ACC), an indigenous breed from South America, maintains high levels of genetic diversity and population structure. In contrast to the commercial Holstein breed, the ACC showed considerable variation in heterozygosity (He) and allelic diversity (A) across populations. As expected, bi-allelic markers showed extensive variation in He whereas the highly polymorphic BoLA-DRB3 showed substantial variation in A, with individual populations having 39,74% of the total number of alleles characterized for the breed. An analysis of molecular variance (AMOVA) of nine populations throughout the distribution range of the ACC revealed that 91.9,94.7% of the total observed variance was explained by differences within populations whereas 5.3,8.1% was the result of differences among populations. In addition, the ACC breed consistently showed higher levels of genetic differentiation among populations than Holstein. Results from this study emphasize the importance of population genetic structure within domestic breeds as an essential component of genetic diversity and suggest that indigenous breeds may be considered important reservoirs of genetic diversity for commercial domestic species. [source]