scholarly journals Cone characteristics and insect predation levels vary across years in mast seeding white spruce

2021 ◽  
Author(s):  
Abigail C Leeper ◽  
Jalene M LaMontagne
Keyword(s):  
Seed Predation ◽  
Mixed Models ◽  
Linear Mixed Models ◽  
Population Level ◽  
White Spruce ◽  
Mast Seeding ◽  
Seed Predator ◽  
Cone Production ◽  
Insect Predation ◽  
Seed Crops

Populations of many tree species exhibit synchronous and highly temporally variable seed crops across years. This is called mast seeding, and there are two predominant hypotheses for this pattern of reproduction, pollination efficiency and seed-predator satiation. Mast seeding studies typically involve records of population-level reproduction, with less information on the characteristics of reproductive structures. Here, we use data across six years (2012-2017), spanning a range of population-level cone conditions, to characterize i) white spruce (Picea glauca) cone lengths and seeds per cone, and ii) levels of seed predation. We quantified population-level cone production and collected 1,399 cones from a total of 38 trees in the Huron Mountains, Michigan, USA. Linear mixed models showed that mean and minimum cone lengths varied significantly across years; both being longest during the greatest cone production year. Larger cones had more seeds and the slopes of the relationships as well as the intercepts varied significantly across years. Generalized linear mixed models and AIC model selection showed that cones with insect predation damage was greatest when population-level reproduction was the lowest, with a mean proportion of cones damaged 0.82 in that year. Our findings show that white spruce cone characteristics and losses to insect seed predation vary temporally, and follow expectations based on mast seeding hypotheses.

scholarly journals Seed masting causes fluctuations in optimum litter size and lag load in a seed predator

2018 ◽  
Author(s):  
Andrew McAdam ◽  
Stan Boutin ◽  
Ben Dantzer ◽  
Jeff Lane
Keyword(s):  
Litter Size ◽  
Picea Glauca ◽  
Life Histories ◽  
Local Density ◽  
White Spruce ◽  
Tamiasciurus Hudsonicus ◽  
Seed Predator ◽  
Red Squirrels ◽  
Seed Predators ◽  
Seed Crops

The episodic production of large seed crops by some perennial plants, is referred to as masting and is known to increase seed escape by alternately starving and swamping seed predators. These pulses of resources, however, might also act as an agent of selection on the life histories of seed predators, which could indirectly enhance seed escape by inducing an evolutionary load on seed predator populations. Lag loads in seed predators could result from mast-induced shifts in optimum phenotypes that exceed the capacity of seed predators to adaptively track optimum phenotypes through phenotypic plasticity. Alternatively, masting could generate mismatches in selection across generations, where adaptation to the parental environment leads to maladaptation in the offspring environment. Here we measured natural selection on female North American red squirrels (Tamiasciurus hudsonicus) across 28 years and five white spruce (Picea glauca) masting events. Red squirrel litter sizes were similar to optimum litter sizes during non-mast years, but were well below optimum litter sizes during resource-rich mast years. Mast events, therefore caused selection for larger litters (B = 0.25) and a lag load (L = 0.25) on red squirrels during mast years. Furthermore, we found that the annual fitness of spruce trees was negatively related to the local density of squirrels during mast years, indicating that the observed lag load on squirrels enhanced the number of spruce cones escaping squirrel predation. Although, the frequency of mast events and the demography of red squirrels were such that offspring and parents often experienced opposite environments with respect to the mast, we found no effect of environmental mismatches across generations on either offspring survival or population growth. Instead, squirrels plastically increased litter sizes in anticipation of mast events, which partially, although not completely, reduced the lag load resulting from this change in food availability. Variable selection on litter size caused by white spruce mast events, therefore, induced a lag load on the population of red squirrels that was not affected by whether individual squirrels were born during mast (matching) or non-mast (mismatching) conditions.

Natural regeneration of ponderosa pine: Pest management strategies for seed predators

2000 ◽  
Vol 76 (4) ◽  
pp. 623-626 ◽  
Author(s):  
Christopher R. Keyes
Keyword(s):  
Pest Management ◽  
Seed Predation ◽  
Ponderosa Pine ◽  
Natural Regeneration ◽  
Management Strategies ◽  
Seed Viability ◽  
Seed Predator ◽  
Management Planning ◽  
Ponderosa Pine Forests ◽  
Seed Crops

Reliance on natural regeneration for reforestation of ponderosa pine forests is increasing as operational budgets decline and public hostility against intensive silvicultural methods increases. Seed predation by small mammals, however, remains an important cause of natural regeneration failure. Direct measures for seed predator control have been tested but have enjoyed only limited success. The best apparent opportunity for avoiding seed predator losses is to schedule harvests during years of large seed crops, when seedfall exceeds consumption and seed viability rates are high. Integrated pest management planning for natural regeneration should emphasize reforestation goals rather than pest eradication. Key words: ponderosa pine, natural regeneration, reforestation, pest management, seed predation

scholarly journals New Applications of Statistical Tools in Plant Pathology

2004 ◽  
Vol 94 (9) ◽  
pp. 999-1003 ◽  
Author(s):  
K. A. Garrett ◽  
L. V. Madden ◽  
G. Hughes ◽  
W. F. Pfender
Keyword(s):  
Plant Pathology ◽  
Statistical Theory ◽  
Mixed Models ◽  
Ordinal Data ◽  
Linear Models ◽  
New Technologies ◽  
Linear Mixed Models ◽  
Population Level ◽  
Experimental Unit ◽  
Normally Distributed

The series of papers introduced by this one address a range of statistical applications in plant pathology, including survival analysis, nonparametric analysis of disease associations, multivariate analyses, neural networks, meta-analysis, and Bayesian statistics. Here we present an overview of additional applications of statistics in plant pathology. An analysis of variance based on the assumption of normally distributed responses with equal variances has been a standard approach in biology for decades. Advances in statistical theory and computation now make it convenient to appropriately deal with discrete responses using generalized linear models, with adjustments for overdispersion as needed. New nonparametric approaches are available for analysis of ordinal data such as disease ratings. Many experiments require the use of models with fixed and random effects for data analysis. New or expanded computing packages, such as SAS PROC MIXED, coupled with extensive advances in statistical theory, allow for appropriate analyses of normally distributed data using linear mixed models, and discrete data with generalized linear mixed models. Decision theory offers a framework in plant pathology for contexts such as the decision about whether to apply or withhold a treatment. Model selection can be performed using Akaike's information criterion. Plant pathologists studying pathogens at the population level have traditionally been the main consumers of statistical approaches in plant pathology, but new technologies such as microarrays supply estimates of gene expression for thousands of genes simultaneously and present challenges for statistical analysis. Applications to the study of the landscape of the field and of the genome share the risk of pseudoreplication, the problem of determining the appropriate scale of the experimental unit and of obtaining sufficient replication at that scale.

scholarly journals Palm harvesting affects seed predation of Euterpe edulis, a threatened palm of the Brazilian Atlantic Forest

2004 ◽  
Vol 64 (3b) ◽  
pp. 669-676 ◽  
Author(s):  
M. A. Pizo ◽  
E. M. Vieira
Keyword(s):  
Atlantic Forest ◽  
Seed Predation ◽  
Tree Species ◽  
Population Level ◽  
Palm Tree ◽  
Seedling Mortality ◽  
Individual Level ◽  
Euterpe Edulis ◽  
Se Brazil ◽  
Insect Predation

The palm tree Euterpe edulis is endemic to the Atlantic Forest, where it constitutes an economically important forest product. The often unplanned and illegal harvesting of palm hearts has led to drastic reductions in the populations of E. edulis in many areas where this palm used to be the dominant understorey tree species. We investigated the effects of harvesting on seed and seedling predation of E. edulis. We tested the predictions of the dominance-predation hypothesis according to which predator satiation leads to an inverse relationship between the amount of predation and the dominance of a tree species. During two consecutive years, seeds were set experimentally on an unharvested (> 250 adult palms/ha) and a neighboring harvested site (few, if any, adult palms) located in the Atlantic Forest of SE Brazil. Seedling mortality was studied at both sites for a six-month period in each of two consecutive years. Seed predation caused by rodents was higher at the harvested site, while insects caused more damage to seeds placed at the unharvested site. The proportion of seeds preyed upon by rodents varied annually, while insect predation did not. Seedling mortality did not differ between harvested and unharvested sites. The dominance-predation hypothesis was confirmed for generalist rodent seed predators, but not for specialist insect predators. This result shows that density-dependent mortality, not only at the individual level but also at the population-level scale, is a function of the class of predators and their types of foraging behavior.

scholarly journals Proximate causes and possible adaptive functions of mast seeding and barren flower shows in spinifex grasses (Triodia spp.) in arid regions of Australia

2014 ◽  
Vol 36 (3) ◽  
pp. 297 ◽  
Author(s):  
Boyd R. Wright ◽  
Alain F. Zuur ◽  
Gary C. K. Chan
Keyword(s):  
Arid Regions ◽  
Seed Set ◽  
Heavy Rain ◽  
Mast Seeding ◽  
High Yield ◽  
Seed Predator ◽  
Related Form ◽  
Proximate Causes ◽  
High Precipitation ◽  
Seed Crops

Mast seeding, the intermittent production of large synchronised seed crops among plant populations, is a phenomenon that occurs at exceptionally long intervals in spinifex grasses (Triodia spp.) from arid regions of Australia. This is despite the reliance of these fire-sensitive plants on seeds for post-fire regeneration, and that spinifex grasslands rate among Australia’s most flammable ecosystems. The proximate causes and possible adaptive functions of masting in seven species of spinifex from arid regions within the 350-mm rainfall isohyet were investigated. Specifically, the seed set percentages of 79 specimens collected between 1947 and 2012 were related to the following environmental covariates: antecedent rainfall over 6, 12 and 36 months, relative humidity, and the number of days above 40°C and below 0°C during anthesis. Given the potential importance of seeding events for post-fire regeneration, it was also investigated whether masting in Triodia could represent a fire-related form of environmentally predictive masting, by testing whether high-yield years corresponded to years of increased fire occurrence. Examination of the dataset showed that 43% of specimens contained completely aborted inflorescences (0% seed fill), while seed set ranged from 2 to 69% in the remaining specimens. High levels of insect activity were also found, with 42% of specimens showing evidence of insect occupation. Statistical analyses showed that the main environmental driver of seed set was high precipitation over the previous 12 months, and that high-yield years were strongly related to years of increased fire likelihood. The number of days over 40°C was a weakly significant driver of yield, while the remaining covariates were not significant. It is hypothesised that intermittent reproduction by Triodia is a fire-related form of environmentally predictive masting, which maximises chances of post-fire regeneration by satiating seed predators during flammable periods (i.e. after heavy rain years). Furthermore, it is suggested that non-viable flower crops after initial low rainfalls may have an adaptive function, by diluting pre-dispersal seed predator densities with ‘decoy’ ovules that do not mature and lead to the starvation of developing larvae.

scholarly journals Heat, Hills and the High Season: A Model-Based Comparative Analysis of Spatio-Temporal Factors Affecting Shared Bicycle Use in Three Southern European Islands

2021 ◽  
Vol 13 (6) ◽  
pp. 3274
Author(s):  
Suzanne Maas ◽  
Paraskevas Nikolaou ◽  
Maria Attard ◽  
Loukas Dimitriou
Keyword(s):  
Correlation Analysis ◽  
Mixed Models ◽  
Linear Mixed Models ◽  
Positive Association ◽  
Sustainable Mobility ◽  
Weather Factors ◽  
Gran Canaria ◽  
Bivariate Correlation ◽  
Temporal Factors

Bicycle sharing systems (BSSs) have been implemented in cities worldwide in an attempt to promote cycling. Despite exhibiting characteristics considered to be barriers to cycling, such as hot summers, hilliness and car-oriented infrastructure, Southern European island cities and tourist destinations Limassol (Cyprus), Las Palmas de Gran Canaria (Canary Islands, Spain) and the Valletta conurbation (Malta) are all experiencing the implementation of BSSs and policies to promote cycling. In this study, a year of trip data and secondary datasets are used to analyze dock-based BSS usage in the three case-study cities. How land use, socio-economic, network and temporal factors influence BSS use at station locations, both as an origin and as a destination, was examined using bivariate correlation analysis and through the development of linear mixed models for each case study. Bivariate correlations showed significant positive associations with the number of cafes and restaurants, vicinity to the beach or promenade and the percentage of foreign population at the BSS station locations in all cities. A positive relation with cycling infrastructure was evident in Limassol and Las Palmas de Gran Canaria, but not in Malta, as no cycling infrastructure is present in the island’s conurbation, where the BSS is primarily operational. Elevation had a negative association with BSS use in all three cities. In Limassol and Malta, where seasonality in weather patterns is strongest, a negative effect of rainfall and a positive effect of higher temperature were observed. Although there was a positive association between BSS use and the number of visiting tourists in Limassol and Malta, this is predominantly explained through the multi-collinearity with weather factors rather than by intensive use of the BSS by tourists. The linear mixed models showed more fine-grained results and explained differences in BSS use at stations, including differences for station use as an origin and as a destination. The insights from the correlation analysis and linear mixed models can be used to inform policies promoting cycling and BSS use and support sustainable mobility policies in the case-study cities and cities with similar characteristics.

scholarly journals Confidence, prediction, and tolerance in linear mixed models

2019 ◽  
Vol 38 (30) ◽  
pp. 5603-5622 ◽  
Author(s):  
Bernard G. Francq ◽  
Dan Lin ◽  
Walter Hoyer
Keyword(s):  
Mixed Models ◽  
Linear Mixed Models

Power for balanced linear mixed models with complex missing data processes

2021 ◽  
pp. 1-19
Author(s):  
Kevin P. Josey ◽  
Brandy M. Ringham ◽  
Anna E. Barón ◽  
Margaret Schenkman ◽  
Katherine A. Sauder ◽  
...  
Keyword(s):  
Missing Data ◽  
Mixed Models ◽  
Linear Mixed Models

l2-Penalized temporal logit-mixed models for the estimation of regional obesity prevalence over time

2021 ◽  
pp. 096228022110175
Author(s):  
Jan P Burgard ◽  
Joscha Krause ◽  
Ralf Münnich ◽  
Domingo Morales
Keyword(s):  
Parameter Estimation ◽  
Medical Treatment ◽  
Mixed Models ◽  
Generalized Linear Mixed Models ◽  
Linear Mixed Models ◽  
Obesity Prevalence ◽  
Model Parameter ◽  
Model Parameter Estimation ◽  
Public Health Reporting ◽  
Over Time

Obesity is considered to be one of the primary health risks in modern industrialized societies. Estimating the evolution of its prevalence over time is an essential element of public health reporting. This requires the application of suitable statistical methods on epidemiologic data with substantial local detail. Generalized linear-mixed models with medical treatment records as covariates mark a powerful combination for this purpose. However, the task is methodologically challenging. Disease frequencies are subject to both regional and temporal heterogeneity. Medical treatment records often show strong internal correlation due to diagnosis-related grouping. This frequently causes excessive variance in model parameter estimation due to rank-deficiency problems. Further, generalized linear-mixed models are often estimated via approximate inference methods as their likelihood functions do not have closed forms. These problems combined lead to unacceptable uncertainty in prevalence estimates over time. We propose an l2-penalized temporal logit-mixed model to solve these issues. We derive empirical best predictors and present a parametric bootstrap to estimate their mean-squared errors. A novel penalized maximum approximate likelihood algorithm for model parameter estimation is stated. With this new methodology, the regional obesity prevalence in Germany from 2009 to 2012 is estimated. We find that the national prevalence ranges between 15 and 16%, with significant regional clustering in eastern Germany.

Estimation of variance components in normal linear mixed models with additivity

2015 ◽  
Author(s):  
Dário Ferreira ◽  
Sandra S. Ferreira ◽  
Célia Nunes ◽  
João T. Mexia
Keyword(s):  
Mixed Models ◽  
Variance Components ◽  
Linear Mixed Models ◽  
Estimation Of Variance
Sign in / Sign up

Export Citation Format

Share Document