Drivers Of Ecological Change Research Articles

The seaweedCaulerpa racemosaon Mediterranean rocky reefs: from passenger to driver of ecological change

The seaweed<i>Caulerpa racemosa</i>on Mediterranean rocky reefs: from passenger to driver of ecological change

Evolution in plant populations as a driver of ecological changes in arthropod communities

Heritable variation in traits can have wide-ranging impacts on species interactions, but the effects that ongoing evolution has on the temporal ecological dynamics of communities are not well understood. Here, we identify three conditions that, if experimentally satisfied, support the hypothesis that evolution by natural selection can drive ecological changes in communities. These conditions are: (i) a focal population exhibits genetic variation in a trait(s), (ii) there is measurable directional selection on the trait(s), and (iii) the trait(s) under selection affects variation in a community variable(s). When these conditions are met, we expect evolution by natural selection to cause ecological changes in the community. We tested these conditions in a field experiment examining the interactions between a native plant (Oenothera biennis) and its associated arthropod community (more than 90 spp.). Oenothera biennis exhibited genetic variation in several plant traits and there was directional selection on plant biomass, life-history strategy (annual versus biennial reproduction) and herbivore resistance. Genetically based variation in biomass and life-history strategy consistently affected the abundance of common arthropod species, total arthropod abundance and arthropod species richness. Using two modelling approaches, we show that evolution by natural selection in large O. biennis populations is predicted to cause changes in the abundance of individual arthropod species, increases in the total abundance of arthropods and a decline in the number of arthropod species. In small O. biennis populations, genetic drift is predicted to swamp out the effects of selection, making the evolution of plant populations unpredictable. In short, evolution by natural selection can play an important role in affecting the dynamics of communities, but these effects depend on several ecological factors. The framework presented here is general and can be applied to other systems to examine the community-level effects of ongoing evolution.

Food for thought: supplementary feeding as a driver of ecological change in avian populations

Every year, millions of households provide huge quantities of supplementary food to wild birds. While alteration of the natural dynamics of food supply represents a major intervention in avian ecology, we have a remarkably limited understanding of the impacts of this widespread pastime. Here, we examine the many and varied responses of birds to supplementary feeding at backyard feeders – in large‐scale management projects and in focused academic studies – and evaluate population responses to the bird‐feeding phenomenon. Our review encompasses a wide range of species, from songbirds to raptors, and compares provisioning with a variety of foods, at different times of year and in different locations. We consider positive impacts, such as aiding species conservation programs, and negative ones, such as increased risk of disease transmission. It seems highly likely that natural selection is being artificially perturbed, as feeding influences almost every aspect of bird ecology, including reproduction, behavior, demography, and distribution. As the effects of bird feeding cascade through ecosystems and interact with processes of environmental change, we suggest areas for future research and highlight the need for large‐scale experiments, with a particular focus on the backyards of an increasingly urban and generous, but sometimes fickle, human population.

Natural Recolonization of Cultivated Land by Native Prairie Plants and its Enhancement by Removal of Scots Pine, &lt;em&gt;Pinus sylvestris&lt;/em&gt;

A combination of native and introduced plants colonized abandoned cultivated land with adjacent relict prairie and savanna in the Rice Lake region of southern Ontario. After 71 years, the native colonizers included 86 species found in regional prairie relicts, but much of the area was also colonized by introduced Scots Pine, Pinus sylvestris, which apparently spread from an adjacent planting. The pines formed expanding patches of dense growth that excluded other species. Removal of the invasive Scots Pine from a 200 m2 plot within the abandoned land led to colonization 17 years later by 36 native species characteristic of the prairie, savanna and sand barrens of the region. Included in this group of native prairie colonizers were keystone species such as Andropogon gerardii, Carex siccata, Ceanothus americanus, Comptonia peregrina and Quercus velutina. Areas where patches of Scots Pine had been allowed to continue growing were either devoid of vegetation or had a sparse understory of introduced species and Poison Ivy (Rhus radicans). These observations support the concepts of (1) protecting islands of native dry ground flora which can serve as sources for recolonization and (2) protection of old field and particularly recently cultivated land adjacent to protected native grassland to allow natural restoration. The fact that keystone native species were able to colonize the area from which the introduced Scots Pines had been removed suggests that the pines are aggressive competitors that occupy space to the exclusion of the native species. Scots Pine is thus a driver of ecological change in degraded ecosystems. Management including removal of Scots Pine to support native plant biodiversity is strongly supported.

Mammalian responses to Pleistocene climate change in southeastern Australia

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Dams and geomorphology: Research progress and future directions

Dams impose changes of flow and sediment transfer that drive changes of channel form along the downstream regulated river. These changes have been described for more than 50 years but process-form relationships have only been advanced with the establishment of a conceptual framework during the 1970s, and then the extension of monitoring data and advancement of remote sensing technologies, particularly over the past 20 years. This paper reviews these developments and identifies three influential themes: (i) channel dynamics, (ii) the role of riparian vegetation, and (iii) channel change as the driver of ecological change. Changes can be rapid in semi-arid regions but elsewhere relaxation periods may extend to millenia. In these latter cases regime or steady-state models should be replaced by models of transient states applied to the reach scale in order to respond to the needs of river managers over decadal timescales.

Use of a conceptual model of societal drivers of ecological change in South Florida: Implications of an ecosystem management scenario

Human-dominated ecosystems such as in South Florida's Everglades region are greatly affected by societal actions and choices, and efforts to restore degraded ecosystems must take into account the societal drivers of ecosystem change. A conceptual model of societal-ecological interactions within the region illustrates connections between major societal drivers, such as water management and land use, and ecological stressors, such as loss of habitat and nutrient loading. Using the conceptual model as an initial guide for discussion, examination of a restoration scenario for the region shows that social and economic effects from activities proposed in a restoration scenario will likely affect most sectors of South Florida. Political effects from changing land and water management practices likely will be significant, as will the physical effects of changing water structures and management practices. Conceptual models such as this can aid in the initial stages of ecosystem restoration discussions and can assist in planning for subsequent social science evaluations of specific societal impacts of actual proposed governmental restoration alternatives. In crafting restoration scenarios, local, regional, and national decision makers can use conceptual models such as this to help broaden the early considerations of how possible future changes in societal drivers, including management choices, will change ecological stressors that affect ecosystem health.