Niche Dynamics

There are many ways of investigating the relationships that exist between species and environments. These fundamental relationships define what habitats a species can exist in, what limiting factors may be keeping species in certain areas, and what resources should be prioritized when planning conservation or reintroduction programs. These relationships define the core niche of an organism, which is just the set of environmental conditions that it needs to exist and reproduce on a landscape. Contemporary analytical tools including machine-learning techniques are able to model these complex species-environment relationships, which can be used to identify critical habitat for species or to understand precisely which habitat features are most important for species preservation. This process is known as niche modeling, and has been used for a variety of purposes ranging from describing ecological relationships to predicting species turnover in response to global climate change.

Wolves and coyotes have existed in North America for millennia, but have undergone a recent distributional turnover due to European colonization. Settlers largely eradicated wolves across North America which opened up significant theoretical habitat for a carnivorous predator. Over the past 100 years, coyotes (Canis latrans) have substantially increased their geographic range across North America, in some part due to human mediated activities, as coyotes are generalist species that can thrive in a multitude of environments. Coyotes and wolves have not been known to interbreed in the wild, but in eastern North America a mid-sized canid known as the eastern wolf (C. lycaon) is able to hybridize with both species. Consequently, the Great Lakes region has larger gray wolves in the west and north, eastern wolves in central and southern Ontario and Quebec, and coyotes in the south. This complex system has created numerous hybrids, and many difficulties for policy and management due to the ubiquity of coyotes and the shrinking range of eastern wolves.

I am investigating macro-scale signatures of species-environment relationships within this system using a variety of niche modeling approaches. Our goal is to characterize niche space for gray wolves, eastern wolves, coyotes, and their respective hybrids across the extent of hybridization to quantify suitable habitat and species-environment relationships for each group. These data will be used to test the idea that hybrids should show somewhat intermediate relationships to environmental variables than to their respective parental group, even at continent-wide scales.

I am also quantifying the importance of incorporating prey models into the niche modeling framework. Traditionally, niche modeling analyses only incorporate abiotic variables like climate (e.g. mean temperature, precipitation) when evaluating an organism’s niche. However, due to the general adaptability of wolves and coyotes and the massive historical distributional range of wolves, we conjecture that predator-prey relationships play a more substantial role in forming distributional patterns. Consequently, I am creating niche models for white-tailed deer, moose, and beaver across eastern North America and will use these models as variables in my wolf and coyote niche models. Due to the strong dependency of a wolf on its prey, we predict that these prey variables will have a disproportionately important effect on model creation. Furthermore, this hybrid system allows us to test this idea one step further. We predict that the strength of the predator-prey relationship exists in a gradient depending on predator size, with wolves having the strongest relationship with moose, and coyotes having the weakest.

The results from this research can be used to delineate critical habitat for eastern wolf conservation, and will provide a methodological basis for strengthening the niche modeling process for predator systems.

See a brief outline of my methods below, created as part of my WCS W. Garfield Weston Foundation Fellowship.