Biomedical subjects

Lisa Crozier

Publications and source records attributed to Lisa Crozier.

3 recordsLinked to original sources

PubMed2006

Combining population-dynamic and ecophysiological models to predict climate-induced insect range shifts.

Hundreds of species are shifting their ranges in response to recent climate warming. To predict how continued climate warming will affect the potential, or “bioclimatic range,” of a skipper butterfly, we present a population‐dynamic model of range shift in which population growth is a function of temperature. We estimate the parameters of this model using previously published data for Atalopedes campestris. Summer and winter temperatures affect population growth rate independently in this species and therefore interact as potential range‐limiting factors. Our model predicts a two‐phase response to climate change; one range‐limiting factor gradually becomes dominant, even if warming occurs steadily along a thermally linear landscape. Whether the range shift accelerates or decelerates and whether the number of generations per year at the range edge increases or decreases depend on whether summer or winter warms faster. To estimate the uncertainty in our predictions of range shift, we use a parametric bootstrap of biological parameter values. Our results show that even modest amounts of data yield predictions with reasonably small confidence intervals, indicating that ecophysiological models can be useful in predicting range changes. Nevertheless, the confidence intervals are sensitive to regional differences in the underlying thermal landscape and the warming scenario.

Animals↗

PubMed2006

Climate impacts at multiple scales: evidence for differential population responses in juvenile Chinook salmon.

1. We explored differential population responses to climate in 18 populations of threatened spring-summer Chinook salmon Onchorynchus tshawytscha in the Salmon River basin, Idaho. 2. Using data from a long-term mark-release-recapture study of juvenile survival, we found that fall stream flow is the best predictor of average survival across all populations. 3. To determine whether all populations responded similarly to climate, we used a cluster analysis to group populations that had similar annual fluctuations in survival. The populations grouped into four clusters, and different environmental factors were important for different clusters. 4. Survival in two of the clusters was negatively correlated with summer temperature, and survival in the other two clusters was positively correlated with minimum fall stream flow, which in turn depends on snow pack from the previous winter. 5. Using classification and regression tree analysis, we identified stream width and stream temperature as key habitat factors that shape the responses of individual populations to climate. 6. Climate change will likely have different impacts on different populations within this metapopulation, and recognizing this diversity is important for accurately assessing risks.

Animals↗

PubMed2003

Winter warming facilitates range expansion: cold tolerance of the butterfly Atalopedes campestris.

Our ability to predict ecological and evolutionary responses to climate change requires an understanding of the mechanistic links between climate and range limits. The warming trend over the past half-century has generated numerous opportunities to develop much-needed case studies of these links. Species that are only limited by climatic factors are likely to shift range quickly during periods of warming. Such species directly impact recipient communities and indicate trends that will become more widespread. Because minimum temperature (T (min)) is rising at twice the rate of maximum temperature, species with this range-limiting factor may be especially responsive to global warming. In this study, I test the hypothesis that rising T (min) has directly affected the range of a skipper butterfly. Atalopedes campestris has moved northward rapidly this century, recently colonizing eastern Washington where January T (min) has risen 3 degrees C in 50 years. The results show that: 1. A. campestris' range lies completely within the -4 degrees C January average minimum isotherm, and that recently colonized areas were below this threshold earlier this century. 2. In acute cold stress experiments, -4 to -7 degrees C proved to be a critical thermal limit: median supercooling point was -6.3 degrees C, and minimum lethal temperature (LT50 with 12-h exposure) was -5.7 degrees C. 3. In chronic cold stress experiments, survivorship declined sharply in diurnally fluctuating thermal regimes typical of the current range edge. High mortality occurred under constant 0 degrees C conditions as well as in fluctuating regimes, implying that thermal insulation from snow would not protect A. campestris. 4. There was no evidence of evolution in cold tolerance at the range margin, despite strong selection. Thus, winter warming was apparently a prerequisite for the range expansion. Characteristics of this species that seem to be associated with its rapid response are that it is an opportunistic species, it is not habitat or dispersal limited, and it is constrained by T (min).

Acclimatization↗