The Population Biology of Alpine Insects, Plants, and Their Interactions 

Spatial and Temporal Metapopulation Dynamics

Since 1995, we have been conducting mark-recapture work in a network of 22 populations of the butterfly Parnassius smintheus to understand factors that regulate and affect the dispersal, dynamics, population genetics, and persistence of these populations.

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Effects of Climate Change and Extreme Weather on Population Dynamics

Using the Pacific Decadal Oscillation (PDO) as an integrated metric of climate (temperature and precipitation), we have shown that previous population size (density-dependence) and the overwintering stage of the butterfly (November-March) have particularly strong effects on year to year changes in population size of this univoltine species. Importantly, population growth is negative during either extremely warm and dry or cold and wet winters. The frequency of these extreme winters has increased over the last 100 years, meaning more years where butterfly populations decrease in size. We have shown that extreme weather events associated with climate change, also have large effects on changes in population size. Our current research is attempting to incorporate the effects of

both of these components of climate change into predictive models and determine if there are better predictors.   

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Mechanisms of Dispersal

Why do organisms move to a new population? Identifying individuals that have moved between populations is difficult for most species.Luckily in our study system we can identify known dispersers and resident individuals based on mark-recapture and have sufficient numbers of disperses to compare morphological, physiological, and in collaboration with Josh Benoit and Nusha Keyghobadi genetic components related to dispersal.

 

Effects and Causes of Rising Treeline

The altitude of treeline is rising in many alpine throughout the world. Along Jumpingpound Ridge there has been considerable change in treeline over the last fifty years. In collaboration with Edward Johnson at the University of Calgary we are examining factors affecting treeline in the front ranges of the Rocky Mountains and how these changes may affect the persistence of alpine species.

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Similar to habitat fragmentation, rising treeline isolates and reduces the area of habitats above treeline, such as alpine meadows. Reduction in habitat area reduces the size of populations, making their extinction more likely. More isolated populations exchange fewer dispersers which may further increase extinction risk for populations dependent upon immigrants to maintain their abundance.

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While this research has direct conservation implications for species at our sites, it also address basic questions relating to how habitat change affects alpine populations and communities.

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Reproductive Asynchrony and Female Mating Success

Generally it is difficult to assess female mating success. In collaboration with Justin Calabrese, Leslie Ries, and Bill Fagan, we are using the distinctive character of the sphragis, attached to female Parnassius butterflies by males during mating, to assess female mating status. Our research has shown that a surprisingly large fraction of the female population does not mate (~10%). Mating success for females is influenced by protandry where males tend to emerge before females. Further work has shown that success may also be related to density and female age. Contrary to expectations, lower female mating success during low density years has little effect on population growth.