John Tipton

• PhD
• Professor (Assistant) at University of Arkansas at Fayetteville

Given the importance of climate in shaping species’ geographic distributions, climate change poses an existential threat to biodiversity. Climate envelope modeling, the predominant approach used to quantify this threat, presumes that individuals in populations respond to climate variability and change according to species-level responses inferred f...

Aim Biogeographers have used three primary data types to examine shifts in tree ranges in response to past climate change: fossil pollen, genetic data and contemporary occurrences. Although recent efforts have explored formal integration of these types of data, we have limited understanding of how integration affects estimates of range shift rates...

In biomedical research, the outcome of longitudinal studies has been traditionally analyzed using the repeated measures analysis of variance (rm‐ANOVA) or more recently, linear mixed models (LMEMs). Although LMEMs are less restrictive than rm‐ANOVA as they can work with unbalanced data and non‐constant correlation between observations, both methodo...

Sedimentary deposits constitute the primary record of changing environmental conditions that have acted on Earth’s surface over geologic time. Clastic material is eroded from source locations (parents) in sediment routing systems and deposited at sink locations (children). Both parents and children have characteristics that vary across many differe...

In biomedical research, the outcome of longitudinal studies has been traditionally analyzed using the repeated measures analysis of variance (rm-ANOVA) or more recently, linear mixed models (LMEMs). Although LMEMs are less restrictive than rm-ANOVA in terms of correlation and missing observations, both methodologies share an assumption of linearity...

Fossil pollen records are well-established indicators of past vegetation changes. The prevalence of pollen across environmental settings including lakes, wetlands, and marine sediments, has made palynology one of the most ubiquitous and valuable tools for studying past environmental and climatic change globally for decades. A complementary research...

Predictions from ecological models necessarily include five different uncertainties: demographic stochasticity, initial conditions, external forcing (i.e., drivers/covariates), parameters, and model processes. However, most predictions from process-based ecological models only account for a subset of these uncertainties (e.g. only demographic stoch...

Proxies that use changes in the composition of ecological communities to reconstruct temporal changes in an environmental covariate are commonly used in paleoclimatology and paleolimnology. Existing methods, such as weighted averaging and modern analog technique, relate compositional data to the covariate in very simple ways, and different methods...

Multivariate compositional count data arise in many applications including ecology, microbiology, genetics, and paleoclimate. A frequent question in the analysis of multivariate compositional count data is what values of a covariate(s) give rise to the observed composition. Learning the relationship between covariates and the compositional count al...

Impacts of global climate change on terrestrial ecosystems are imperfectly constrained by ecosystem models and direct observations. Pervasive ecosystem transformations occurred in response to warming and associated climatic changes during the last glacial-to-interglacial transition, which was comparable in magnitude to warming projected for the nex...

Scientific records of temperature and precipitation have been kept for several hundred years, but for many areas, only a shorter record exists. To understand climate change, there is a need for rigorous statistical reconstructions of the paleoclimate using proxy data. Paleoclimate proxy data are often sparse, noisy, indirect measurements of the cli...

One crucial component of large fire response in the United States (US) is the sharing of wildland firefighting resources between regions: resources from regions experiencing low fire activity supplement resources in regions experiencing high fire activity. An important step towards improving the efficiency of resource sharing and related policies i...

Analyzing ecological data often requires modeling the autocorrelation created by spatial and temporal processes. Many seemingly disparate statistical methods used to account for autocorrelation can be expressed as regression models that include basis functions. Basis functions also enable ecologists to modify a wide range of existing ecological mod...

Analyzing ecological data often requires modeling the autocorrelation created by spatial and temporal processes. Many of the statistical methods used to account for autocorrelation can be viewed as regression models that include basis functions. Understanding the concept of basis functions enables ecologists to modify commonly used ecological model...

Analyzing ecological data often requires modeling the autocorrelation created by spatial and temporal processes. Many of the statistical methods used to account for autocorrelation can be viewed as regression models that include basis functions. Understanding the concept of basis functions enables ecologists to modify commonly used ecological model...

We compared catches of Mysis diluviana in 80 vertical tows with large (1.0 m diameter) and small (0.5 m diameter) plankton nets to determine if the small net could be used in long-term monitoring historically conducted with the large net. Both nets were constructed of 500-μm aperture mesh and were towed simultaneously at 0.4 m/s. Comparisons were m...

Reconstruction of pre-instrumental, late Holocene climate is important for understanding how climate has changed in the past and how climate might change in the future. Statistical prediction of paleoclimate from tree ring widths is challenging because tree ring widths are a one-dimensional summary of annual growth that represents a multi-dimension...

Post-stratification is commonly used to improve the precision of survey estimates. In traditional post-stratification methods, the stratification variable must be known at the population level. When suitable covariates are available at the population level, an alternative approach consists of fitting a model on the covariates, making predictions fo...

La variación geográfica en las vocalizaciones aprendidas frecuentemente se atribuye en parte a un aprendizaje imperfecto del canto, pero esto rara vez ha sido documentado. Además, se conoce poco en cuanto a cómo la estructura espacial de las poblaciones afecta la divergencia geográfica en los cantos. Usando cantos únicos fi-bi de Poecile atricapill...

Geographic variation in learned vocalizations is commonly attributed, in part, to imperfect song learning, but rarely has this been documented. Additionally, we know little about how spatial structure of populations affects geographic divergence in song. Using novel fee-bee song in Black-capped Chickadees (Poecile atricapillus) in Fort Collins, Col...