Search results for "POPULATION"
showing 10 items of 9945 documents
Population dynamic consequences of delayed life-history effects
2002
Evidence from wildlife and human populations indicates that conditions during early development can have marked effects on the subsequent performance of individuals and cohorts. Likewise, the effects of maternal and, more generally, parental environments can be transferred among individuals between generations. These delayed life-history effects are found consistently and suggestions have been made that they can be one source of both variability and of delayed density dependence in population dynamics. Assessments of several different time series indicate that population variability and delayed density dependence are common and that understanding the mechanisms giving rise to them is crucia…
Palaeopathological Evidence of Infectious Disease in a Skeletal Population from Late Medieval Riga, Latvia (15Th-17Th Centuries AD)
2017
Abstract The aim of this study was to evaluate the presence of infectious disease in the Dome Church (Riga Cathedral) Cemetery population, dating from the late medieval period (15th-17th centuries AD). A total of 274 individuals were macroscopically observed for evidence of infectious disease, and seven individuals with lesions possibly associated with a bacterial infection affecting the skeleton were selected for further analysis. Pathological changes on the outer table of the skull and in the long bones of legs characteristic of venereal syphilis were observed in four female and one male individual. Likewise, changes possibly related to late congenital syphilis were observed in a 14-15-ye…
Age structure in a newly established and increasing population: initially high proportion of young birds among nesting Great Grey Owls
2020
AbstractThe mechanisms behind expansions of the distribution of a bird species and the ensuing establishment of new populations are poorly known. The distribution of Great Grey Owl (Strix nebulosa) in the western Palearctic has generally expanded towards southwest during the past fifty years, and particularly so in Fennoscandia. In the past decade, the recorded breeding population in Norway, confined to Hedmark county bordering Sweden, increased from 1 pair in 2009 to > 100 pairs in 2017–2018, extending the southwestern border of the distribution > 100 km. We studied the age structure of this expanding population based on the molting pattern of the wing feathers of birds captured at t…
Morphology, Genetics and Biology of Pterochloroides persicae Cholodkovsky (Hemiptera: Lachninae) and Their Effect on Pauesia antennata Mukerji (Hymen…
2021
Pauesia antennata Mukerji is a specific parasitoid of the brown peach aphid Pterochloroides persicae Cholodkovsky which causes severe damage on almond and peach in Tunisia. To control this pest, P. antennata was collected from Iran, introduced to Tunisia in 2011 and some of their biological parameters were studied in laboratory conditions. Therefore, in orchard, aphid population and sites/zones of Tunisia and aphid behaviour impact on the parasitoid have not been studied. Morphometric measurements, molecular analysis of P. persicae specimens collected from two Tunisian sites [(Akouda-Sousse (Site 1), Sfax (Site 2)] were studied and compared and aphid behaviour versus P. antennata was follow…
Avian predation on a parasitic fly of cervids during winter: can host-related cues increase the predation risk?
2012
The deer ked (Lipoptena cervi) is an ectoparasitic fly on cervids that has expanded its distribution rapidly in Northern Europe. However, the regulating biotic factors such as predation remain unknown. The host-independent pupal stage of the fly lasts for several months. Blackish pupae are visible against snow, especially on the bedding sites of hosts, and are thus exposed to predators. To evaluate the role of predation on the invasion dynamics and evolution of L. cervi, we monitored pupal predation on artificial bedding sites in three geographical areas in Finland during winter. We explored: (1) possible predators; (2) magnitude of predation; and (3) whether predation risk is affected by h…
Is the impact of environmental noise visible in the dynamics of age-structured populations?
2001
Climate change has ignited lively research into its impact on various population–level processes. The research agenda in ecology says that some of the fluctuations in population size are accountable for by the external noise (e.g. weather) modulating the dynamics of populations. We obeyed the agenda by assuming population growth after a resource–limited Leslie matrix model in an age–structured population. The renewal process was disturbed by superimposing noise on the development of numbers in one or several age groups. We constructed models for iteroparous and semelparous breeders so that, for both categories, the population growth rate was matching. We analysed how the modulated populatio…
Can the problem of hybridization in threatened species be evaluated using a fieldwork research? A case study in snapdragons
2019
Abstract 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. litigi…
Unrelenting spread of the alien monk parakeetMyiopsitta monachusin Israel. Is it time to sound the alarm?
2016
BACKGROUND Monk parakeets, Myiopsitta monachus Boddaert, are native to South America but have established populations in North America, Europe, Africa and Asia. They are claimed to act as agricultural pests in their native range, and their communal stick nests may damage human infrastructure. Although several monk parakeet populations are present in the Mediterranean Basin and temperate Europe, little empirical data are available on their population size and growth, distribution and potential impact. We investigated the temporal and spatial dynamics of monk parakeets in Israel to assess their invasion success and potential impact on agriculture. RESULTS Monk parakeet populations are growing…
Environmental Fluctuations Drive Species' Competitive Success in Experimental Invasions
2020
Climate change is presumed to increase both the number and frequency of fluctuations in environmental conditions. Fluctuations can affect the ecological and evolutionary processes that make species more successful competitors. For example, fluctuating conditions can create selection pressures for traits that are profitable in adaptation to fast climate change. On an ecological timescale, environmental fluctuations can facilitate species competitive success by reducing other species’ population sizes. Climate change could then enhance species invasions into new areas if fluctuation-adapted invaders displace their native competitors in chancing environments. We tested experimentally whether f…
New national and regional bryophyte records, 35
2013
Department of Botany, University of Stellenbosch, SouthAfrica1. Brachythecium laetum(Brid.) Schimp.Contributors: S. Huttunen, M. S. Ignatov and T.Korvenpa¨a¨Finland: La¨nsi-Turunmaa, Houtskari, on east andsouth shore of island Na taholm, 60u15945.3060N21u19911.960W, in rich deciduous forest withCorylusavellanaL. understory and some calcareous soils, 13August 2008, leg. Turkka Korvenpa¨a¨, det.M.S.Ignatov in August 2012 (original det. Brachytheciumcampestre) (TUR116496).The specimen ofBrachythecium laetumwas notedby M. S. Ignatov in connection with studies onFinnish material of B. campestre(Mu¨ll.Hal.) Schimp.from the Turku University Herbarium (TUR).Additional collections were searched for …