Repository logo

Browsing by Author "Hämäläinen, Anni"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Conservation triage at the trailing edge of climate envelopes
    (2020) Gilbert, Sophie L.; Broadley, Kate; Doran-Myers, Darcy; Droghini, Amanda; Haines, Jessica A.; Hämäläinen, Anni; Lamb, Clayton T.; Neilson, Eric W.; Boutin, Stan
    Species protection via geographically fixed conservation actions is a primary tool for maintenance of biodiversity worldwide (Pimm et al. 2014). Yet, for many species, the assumption that currently suitable sites will remain so is undermined by climate change (Urban 2015; Wiens 2016). Climate-change-associated range shifts (Chen et al. 2011), a process driven by populations at the trailing edge of the climate envelope going extinct or moving and those at the leading edge becoming established, are becoming widespread around the world (Wiens 2016). We argue that conservation of populations of at-risk species should be prioritized across each species’ range based on future climatic suitability of an area with the goal of maintaining or increasing the number of viable populations range wide. Such range-wide prioritization could help conserve species in a changing climate when resources are limited; effort would be reallocated to viable populations (Oliver et al. 2012; Alagador & Cerdeira 2016). Promisingly, resistance to this approach (Oliver et al. 2016) may be waning. Many nongovernment organizations (e.g., International Panel on Climate Change, World Wildlife Fund) now use climate-informed range-wide approaches, as do some national and state agencies (e.g., Association of Fish & Wildlife Agencies 2018; Cornwall 2018). We aimed to advance discussion and implementation of climate-informed prioritization across species’ ranges and considered when populations behind the trailing edge of climate change should be deprioritized.
  • Thumbnail Image
    Item
    The ecological significance of secondary seed dispersal by carnivores
    (2017) Hämäläinen, Anni; Broadley, Kate; Droghini, Amanda; Haines, Jessica A.; Lamb, Clayton T.; Boutin, Stan; Gilbert, Sophie L.
    Animals play an important role in the seed dispersal of many plants. It is increasingly recognized, however, that the actions of a single disperser rarely determine a seed's fate and final location; rather, multiple abiotic or animal dispersal vectors are involved. Some carnivores act as secondary dispersers by preying on primary seed dispersers or seed predators, inadvertently consuming seeds contained in their prey's digestive tracts and later depositing viable seeds, a process known as diploendozoochory. Carnivores occupy an array of ecological niches and thus range broadly on the landscape. Consequently, secondary seed dispersal by carnivores could have important consequences for plant dispersal outcomes, with implications for ecosystem functioning under a changing climate and across disturbed landscapes where dispersal may be otherwise limited. For example, trophic downgrading through the loss of carnivores may reduce or eliminate diploendozoochory and thus compromise population connectivity for lower trophic levels. We review the literature on diploendozoochory and conclude that the ecological impact of a secondary vs. primary seed disperser depends on the relative dispersal distances, germination success, and the proportion of seeds exposed to secondary dispersal by carnivores. None of the studies up to present day have been able to rigorously assess the ecological significance of this process. We provide a framework of the components that determine the significance of diploendozoochory across systems and identify the components that must be addressed in future studies attempting to assess the ecological importance of diploendozoochory.
  • Thumbnail Image
    Item
    Fitness consequences of peak reproductive effort in a resource pulse system
    (2017) Hämäläinen, Anni; McAdam, Andrew G.; Dantzer, Ben; Lane, Jeffrey E.; Haines, Jessica A.; Humphries, Murray M.; Boutin, Stan
    The age trajectory of reproductive performance of many iteroparous species features an early - life increase in performance followed by a late - life senescent decline. The largest contribution of lifetime reproductive success is therefore gained at the age at which reproductive performance peaks. Using long term data on North American red squirrels we show that the environmental conditions individuals encountered could cause variation among individuals in the “height” and timing of this peak, contributing to life history variation and fitness in this population that experiences irregular resource pulses. As expected, high peak effort was positively associated with lifetime reproductive output up to a high level of annual effort. Furthermore, individuals that matched their peak reproductive effort to an anticipated resource pulse gained substantial fitness benefits through recruiting more offspring over their lifetime. Individual variation in peak reproductive effort thus has strong potential to shape life history evolution by facilitating adaptation to fluctuating environments.
  • Thumbnail Image
    Item
    Quantifying fear effects on prey demography in nature
    (2018) Peers, Michael J. L.; Majchrzak, Yasmine N.; Neilson, Eric W.; Lamb, Clayton T.; Hämäläinen, Anni; Haines, Jessica A.; Garland, Laura; Doran-Myers, Darcy; Broadley, Kate; Boonstra, Rudy; Boutin, Stan
    In recent years, it has been argued that the effect of predator fear exacts a greater demographic toll on prey populations than the direct killing of prey. However, efforts to quantify the effects of fear have primarily relied on experiments that replace predators with predator cues. Interpretation of these experiments must consider two important caveats: (1) the magnitude of experimenter-induced predator cues may not be realistically comparable to those of the prey’s natural sensory environment, and (2) given functional predators are removed from the treatments, the fear effect is measured in the absence of any consumptive effects, a situation which never occurs in nature. We contend that demographic consequences of fear in natural populations may have been overestimated because the intensity of predator cues applied by experimenters in the majority of studies has been unnaturally high, in some instances rarely occurring in nature without consumption. Furthermore, the removal of consumption from the treatments creates the potential situation that individual prey in poor condition (those most likely to contribute strongly to the observed fear effects via starvation or reduced reproductive output) may have been consumed by predators in nature prior to the expression of fear effects, thus confounding consumptive and fear effects. Here, we describe an alternative treatment design that does not utilize predator cues, and in so doing, better quantifies the demographic effect of fear on wild populations. This treatment substitutes the traditional cue experiment where consumptive effects are eliminated and fear is simulated with a design where fear is removed and consumptive effects are simulated through the experimental removal of prey. Comparison to a natural population would give a more robust estimate of the effect of fear in the presence of consumption on the demographic variable of interest. This approach represents a critical advance in quantifying the mechanistic pathways through which predation structures ecological communities. Discussing the merits of both treatments will motivate researchers to go beyond simply describing the existence of fear effects and focus on testing their true magnitude in wild populations and natural communities.