			Home About us Contact

Self-sustaining Populations (self-sustaining + population)

Distribution by Scientific Domains

Life Sciences	80%

Selected Abstracts

Population growth and mass mortality of an estuarine fish, Acanthopagrus butcheri, unlawfully introduced into an inland lake

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2009
Kimberley Smith
Abstract 1.In 2006, two periods of hypoxia resulted in the death of approximately 35 tonnes of black bream (Acanthopagrus butcheri) in Lake Indoon, a small inland lake in Western Australia. 2.Acanthopagrus butcheri was the first fish species to be recorded in this lake, along with the mosquitofish (Gambusia holbrooki) which was also observed during sampling in 2006. Acanthopagrus butcheri appears to have been introduced to Lake Indoon between 1998 and 2003 and formed a self-sustaining population. It is believed to have been deliberately introduced for the purpose of creating a recreational fishery, despite the existence of substantial penalties for illegal translocation of fish in Western Australia. 3.Recent human-induced environmental changes, including rising groundwater and salinization, have probably aided the establishment of both species in Lake Indoon. The importance of salinity to recruitment success by A. butcheri was indicated by the presence of only two age classes in 2006, with estimated recruitment dates coinciding with the years of highest recorded salinity in the lake. 4.The ,fish kills' provided an opportunity to examine aspects of A. butcheri biology in a relatively low salinity environment which is atypical for this estuarine species. In particular, the recruitment period in Lake Indoon was delayed until autumn/winter, rather than spring/summer as seen in other populations. Biological responses in Lake Indoon have implications for natural populations living in estuaries with modified salinity regimes. 5.The ecological, social and economic impacts potentially arising from the introduction of fish to Lake Indoon, which is an important migratory bird habitat and a recreational amenity for local residents and tourists, illustrate the complexities of fish translocation and the need for rigorous assessment before stocking to identify potential costs and benefits. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Seed supply for broadscale restoration: maximizing evolutionary potential

EVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 4 2008
Linda M. Broadhurst
Abstract Restoring degraded land to combat environmental degradation requires the collection of vast quantities of germplasm (seed). Sourcing this material raises questions related to provenance selection, seed quality and harvest sustainability. Restoration guidelines strongly recommend using local sources to maximize local adaptation and prevent outbreeding depression, but in highly modified landscapes this restricts collection to small remnants where limited, poor quality seed is available, and where harvesting impacts may be high. We review three principles guiding the sourcing of restoration germplasm: (i) the appropriateness of using ,local' seed, (ii) sample sizes and population characteristics required to capture sufficient genetic diversity to establish self-sustaining populations and (iii) the impact of over-harvesting source populations. We review these topics by examining current collection guidelines and the evidence supporting these, then we consider if the guidelines can be improved and the consequences of not doing so. We find that the emphasis on local seed sourcing will, in many cases, lead to poor restoration outcomes, particularly at broad geographic scales. We suggest that seed sourcing should concentrate less on local collection and more on capturing high quality and genetically diverse seed to maximize the adaptive potential of restoration efforts to current and future environmental change. [source]

Seasonal mortality and the effect of body size: a review and an empirical test using individual data on brown trout

FUNCTIONAL ECOLOGY, Issue 4 2008
Stephanie M. Carlson
Summary 1,For organisms inhabiting strongly seasonal environments, over-winter mortality is thought to be severe and size-dependent, with larger individuals presumed to survive at a higher rate than smaller conspecifics. Despite the intuitive appeal and prevalence of these ideas in the literature, few studies have formally tested these hypotheses. 2We here tested the support for these two hypotheses in stream-dwelling salmonids. In particular, we combined an empirical study in which we tracked the fate of individually-marked brown trout across multiple seasons and multiple years with a literature review in which we compiled the results of all previous pertinent research in stream-dwelling salmonids. 3We report that over-winter mortality does not consistently exceed mortality during other seasons. This result emerged from both our own research as well as our review of previous research focusing on whether winter survival is lower than survival during other seasons. 4We also report that bigger is not always better in terms of survival. Indeed, bigger is often worse. Again, this result emerged from both our own empirical work as well as the compilation of previous research focusing on the relationship between size and survival. 5We suggest that these results are not entirely unexpected because self-sustaining populations are presumably adapted to the predictable seasonal variation in environmental conditions that they experience. [source]

Spatial population structure of a specialist leaf-mining moth

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2008
Sofia Gripenberg
Summary 1The spatial structure of natural populations may profoundly influence their dynamics. Depending on the frequency of movements among local populations and the consequent balance between local and regional population processes, earlier work has attempted to classify metapopulations into clear-cut categories, ranging from patchy populations to sets of remnant populations. In an alternative, dichotomous scheme, local populations have been classified as self-sustaining populations generating a surplus of individuals (sources) and those depending on immigration for persistence (sinks). 2In this paper, we describe the spatial population structure of the leaf-mining moth Tischeria ekebladella, a specialist herbivore of the pedunculate oak Quercus robur. We relate moth dispersal to the distribution of oaks on Wattkast, a small island (5 km2) off the south-western coast of Finland. 3We build a spatially realistic metapopulation model derived from assumptions concerning the behaviour of individual moths, and show that the model is able to explain part of the variation in observed patterns of occurrence and colonization. 4While the species was always present on large trees, a considerable proportion of the local populations associated with small oaks showed extinction,recolonization dynamics. The vast majority of moth individuals occur on large trees. 5According to model predictions, the dominance of local vs. regional processes in tree-specific moth dynamics varies drastically across the landscape. Most local populations may be defined broadly as ,sinks', as model simulations suggest that in the absence of immigration, only the largest oaks will sustain viable moth populations. Large trees in areas of high oak density will contribute most to the overall persistence of the metapopulation by acting as sources of moths colonizing other trees. 6No single ,metapopulation type' will suffice to describe the oak,moth system. Instead, our study supports the notion that real populations are often a mix of earlier identified categories. The level to which local populations may persist after landscape modification will vary across the landscape, and sweeping classifications of metapopulations into single categories will contribute little to understanding how individual local populations contribute to the overall persistence of the system. [source]

Invasive ants in Australia: documented and potential ecological consequences

AUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2008
Lori Lach
Abstract A growing number of species are being transported and introduced by humans to new locations and are establishing self-sustaining populations outside their native ranges. Since ants play many ecological roles, introduction of an invasive ant species, and subsequent disruption of Australia's rich and abundant native ant fauna, has the potential for numerous adverse consequences. Over 6700 ants representing 105 species from 73 genera have been intercepted at Australian ports of entry in the last 20 years and all six of the world's most destructive invasive ants have become established in the country. Here we review the current and potential consequences of these ants on Australia's natural and agricultural environments. To date, several studies, most involving the big-headed ant, Pheidole megacephala, and the Argentine ant, Linepithema humile, have documented a decline in native ant species richness. The displacement of native ants by these invaders could have multiple consequences for the native flora and fauna. Since few of these have been investigated in Australia, we combine knowledge from invasions elsewhere, the ecology of the interactions, and data on current and predicted geographic ranges of introduced ants to hypothesise about likely indirect effects of invasive ants in Australia. Further investigations that are aimed at testing these predictions will also aid in justifying and prioritising national prevention and control efforts, and will contribute to some of the long-standing questions about ant invasions globally. [source]