Forty years of carabid beetle research in Europe - from taxonomy, biology, ecology and population studies to bioindication, habitat assessment and conservation

Volume: 100Start Page: 55End Page: 14

Data from: Population-level consequences of herbivory, changing climate and source-sink dynamics on a long-lived invasive shrub

Long-lived plant species are highly valued environmentally, economically, and socially, but can also cause substantial harm as invaders. Realistic demographic predictions can guide management decisions, and are particularly valuable for long-lived species where population response times can be long. Long-lived species are also challenging, given population dynamics can be affected by factors as diverse as herbivory, climate, and dispersal. We developed a matrix model to evaluate the effects of herbivory by a leaf-feeding biological control agent released in Australia against a long-lived invasive shrub (mesquite, Leguminoseae: Prosopis spp.). The stage-structured, density-dependent model used an annual time step and 10 climatically diverse years of field data. Mesquite population demography is sensitive to source–sink dynamics as most seeds are consumed and redistributed spatially by livestock. In addition, individual mesquite plants, because they are long lived, experience natural climate variation that cycles over decadal scales, as well as anthropogenic climate change. The model therefore explicitly considered the effects of both net dispersal and climate variation. Herbivory strongly regulated mesquite populations through reduced growth and fertility, but additional mortality of older plants will be required to reach management goals within a reasonable time frame. Growth and survival of seeds and seedlings were correlated with daily soil moisture. As a result, population dynamics were sensitive to rainfall scenario, but population response times were typically slow (20–800 years to reach equilibrium or extinction) due to adult longevity. Equilibrium population densities were expected to remain 5% higher, and be more dynamic, if historical multi-decadal climate patterns persist, the effect being dampened by herbivory suppressing seed production irrespective of preceding rainfall. Dense infestations were unlikely to form under a drier climate, and required net dispersal under the current climate. Seed input wasn't required to form dense infestations under a wetter climate. Each factor we considered (ongoing herbivory, changing climate, and source–sink dynamics) has a strong bearing on how this invasive species should be managed, highlighting the need for considering both ecological context (in this case, source–sink dynamics) and the effect of climate variability at relevant temporal scales (daily, multi-decadal, and anthropogenic) when deriving management recommendations for long-lived species

Understanding the limits to species‐wide demographic generalizations: the ecology and management of Parkinsonia aculeata

Abstract The search for generalizations in the face of complex species–environment interactions is particularly important for minimizing the cost of managing populations of species. We tested whether we could generalize, at various nested scales, the species‐level demography of the widely invasive plant species Parkinsonia aculeata (Fabaceae) and whether these generalizations were representative of the demography observed locally. Full demographic surveys at all life stages of the species were conducted in 23 Australian sites during seven years (from 2000 to 2007), across a 1000‐km climatic gradient. Sites were nested across four climate regions (arid, semi‐arid, semi‐wet/dry tropics, wet/dry tropics) and three habitat types (upland, wetland, and riparian). We estimated the vital rates (growth/retrogression, survival, fecundity) at all life stages and size classes and combined them to create 99 site–year demographic matrix population models. With these models, we then estimated site–year‐specific asymptotic population growth rates and their corresponding prospective elasticity values to perturbation of the vital rates. We then developed a nested retrospective elasticity analysis (nested LTRE) to test whether and how upscaling the results (i.e., from site to habitat, to climate region, and to the invaded range) produced averaging bias, which could lead to spurious interpretations of the relationships between the retrospective elasticity values. The prospective analysis highlighted that site–year variation in the matrix population models, population growth rates, and corresponding elasticities could not be well summarized by a single species‐level analysis and that the spread was as diverse as found in previously reported multispecies‐level demographic analyses. The nested LTRE analysis showed that upscaling demographic models introduced for most sites new sources of errors in the estimation (in terms of magnitude and sign of retrospective elasticities), which increased drastically as we progressively aggregate the demographic information between nested scales of observation. Our findings suggest that regardless of the scale, demographic generalizations at the species scale are not always useful for managing P. aculeata across sites in its invaded range, given its plasticity in demography

Field data used to parameterise the mesquite population model

An overview of what field data was used to estimate each parameter is provided in the first tab. Subsequent tabs contain the raw field data that was collected, including a text box providing a brief description of the data source. Notes on column headings provide information on data fields where it is not self-explanatory

Phenotypic Plasticity Influences the Size, Shape and Dynamics of the Geographic Distribution of an Invasive Plant

<div><p>Phenotypic plasticity has long been suspected to allow invasive species to expand their geographic range across large-scale environmental gradients. We tested this possibility in Australia using a continental scale survey of the invasive tree <em>Parkinsonia aculeata</em> (Fabaceae) in twenty-three sites distributed across four climate regions and three habitat types. Using tree-level responses, we detected a trade-off between seed mass and seed number across the moisture gradient. Individual trees plastically and reversibly produced many small seeds at dry sites or years, and few big seeds at wet sites and years. Bigger seeds were positively correlated with higher seed and seedling survival rates. The trade-off, the relation between seed mass, seed and seedling survival, and other fitness components of the plant life-cycle were integrated within a matrix population model. The model confirms that the plastic response resulted in average fitness benefits across the life-cycle. Plasticity resulted in average fitness being positively maintained at the wet and dry range margins where extinction risks would otherwise have been high (“<em>Jack-of-all-Trades</em>” strategy <em>JT</em>), and fitness being maximized at the species range centre where extinction risks were already low (“<em>Master-of-Some</em>” strategy <em>MS</em>). The resulting hybrid “<em>Jack-and-Master</em>” strategy (<em>JM</em>) broadened the geographic range and amplified average fitness in the range centre. Our study provides the first empirical evidence for a <em>JM</em> species. It also confirms mechanistically the importance of phenotypic plasticity in determining the size, the shape and the dynamic of a species distribution. The <em>JM</em> allows rapid and reversible phenotypic responses to new or changing moisture conditions at different scales, providing the species with definite advantages over genetic adaptation when invading diverse and variable environments. Furthermore, natural selection pressure acting on phenotypic plasticity is predicted to result in maintenance of the <em>JT</em> and strengthening of the <em>MS</em>, further enhancing the species invasiveness in its range centre.</p> </div

Benefits of plasticity on fitness components.

<p>A) on seed survival rate (<i>S_seed</i>), and B) on seedling survival rate (<i>S_sg</i>). A, SA, SWT, WT refer to the climate regions (see nomenclature in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032323#pone-0032323-g001" target="_blank">Fig. 1</a>). For SWT, the Ord site (SWT_Ord) and Auvergne site (SWT_Auv) were analysed separately to account for the difference in <i>S_sg</i>.</p

Appendix B. Summary of data sources used to parameterize each vital rate.

Summary of data sources used to parameterize each vital rate

Life-cycle and life-stages of <i>Parkinsonia aculeata</i>.

<p>Nodes represent the three main demographic stages: seed bank (<i>SB</i>), juvenile (<i>Juv</i>: non-reproductive) and adult (<i>Ad</i>). Nodes (continuous lines) represent stages that can be stratified at an annual time step. The adult stage (dashed line) was stratified into 7 sub-stages according to canopy volume: <i>Ad_1.5</i>, <i>Ad₅</i>, <i>Ad₂₀</i>, <i>Ad₅₀</i>, <i>Ad₁₀₀</i>, <i>Ad₂₀₀</i>, <i>Ad₃₀₀</i> m³: for instance in the volume class <i>A_1.5</i>, trees have a volume between ]1.5 m³–5 m³], and <i>Ad₃₀₀</i> have volume larger than 300 m². Arcs that link nodes represent the flow of individuals that transit from one stage to another. Self-loops represent the capacity for individuals to delay the transition to the next stage.</p

Selection pressure on the plastic trade-off across the annual rainfall gradient, calculated as the sensitivity of <i>average fitness</i> to potential change in the slope (<i>α</i>) and intercept (<i>β</i>) of the trade-off between seed mass and seed number.

<p>Error bars represent s.d. For the riparian habitat in the semi-arid hot and semi-wet tropical region, sensitivities are not stochastic and s.d. represents the variation between years at those sites.</p

Unravelling the annual cycle in a migratory animal: breeding-season habitat loss drives population declines of monarch butterflies

Threats to migratory animals can occur at multiple periods of the annual cycle that are separated by thousands of kilometres and span international borders. Populations of the iconic monarch butterfly (Danaus plexippus) of eastern North America have declined over the last 21 years. Three hypotheses have been posed to explain the decline: habitat loss on the overwintering grounds in Mexico, habitat loss on the breeding grounds in the United States and Canada, and extreme weather events. Our objectives were to assess population viability, determine which life stage, season and geographical region are contributing the most to population dynamics and test the three hypotheses that explain the observed population decline. We developed a spatially structured, stochastic and density-dependent periodic projection matrix model that integrates patterns of migratory connectivity and demographic vital rates across the annual cycle. We used perturbation analysis to determine the sensitivity of population abundance to changes in vital rate among life stages, seasons and geographical regions. Next, we compared the singular effects of each threat to the full model where all factors operate concurrently. Finally, we generated predictions to assess the risk of host plant loss as a result of genetically modified crops on current and future monarch butterfly population size and extinction probability. Our year-round population model predicted population declines of 14% and a quasi-extinction probability (5% within a century. Monarch abundance was more than four times more sensitive to perturbations of vital rates on the breeding grounds than on the wintering grounds. Simulations that considered only forest loss or climate change in Mexico predicted higher population sizes compared to milkweed declines on the breeding grounds. Our model predictions also suggest that mitigating the negative effects of genetically modified crops results in higher population size and lower extinction risk. Recent population declines stem from reduction in milkweed host plants in the United States that arise from increasing adoption of genetically modified crops and land-use change, not from climate change or degradation of forest habitats in Mexico. Therefore, reducing the negative effects of host plant loss on the breeding grounds is the top conservation priority to slow or halt future population declines of monarch butterflies in North America