Amy Lauren. Angert

Publications (4)8.26 Total impact

• Source

  Available from: arizona.edu

  Article: Demography of central and marginal populations of monkeyflowers (Mimulus cardinalis and M. lewisii).

  Amy Lauren Angert
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  ABSTRACT: Every species occupies a limited geographic area, but how spatiotemporal environmental variation affects individual and population fitness to create range limits is not well understood. Because range boundaries arise where, on average, populations are more likely to go extinct than to persist, range limits are an inherently population-level problem for which a demographic framework is useful. In this study, I compare demographic parameters and population dynamics between central and marginal populations of monkeyflowers, Mimulus cardinalis and M. lewisii, along an elevation gradient spanning both species' ranges. Central and marginal populations of both species differed in survival and fecundity. For M. lewisii, these components of fitness were higher in central than in marginal populations, but for M. cardinalis the converse was true. To assess spatiotemporal variation in population dynamics, I used transition matrix models to estimate asymptotic population growth rates (lambda) and found that population growth rates of M. lewisii were highest at the range center and reduced at the range margin. Population growth rates of M. cardinalis were highest at the range margin and greatly reduced at the range center. Life table response analysis decomposed spatiotemporal variation in lambda into contributions from each transition between life stages, finding that transitions from large nonreproductive and reproductive plants to the seed class and stasis in the reproductive class made the largest contributions to spatial differences in lambda. These transitions had only low to moderate sensitivities, indicating that differences in projected population growth rates resulted mainly from observed differences in transition matrix parameters and their underlying vital rates.
  Ecology 09/2006; 87(8):2014-25. · 4.85 Impact Factor
• Source

  Available from: arizona.edu

  Article: Growth and leaf physiology of monkeyflowers with different altitude ranges.

  Amy Lauren Angert
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  ABSTRACT: Every species is limited both geographically and ecologically to a subset of available habitats, yet for many species the causes of distribution limits are unknown. Temperature is thought to be one of the primary determinants of species distributions along latitudinal and altitudinal gradients. This study examined leaf physiology and plant performance under contrasting temperature regimes of sister species of monkeyflower, Mimulus cardinalis and Mimulus lewisii (Phrymaceae), that differ in altitude distribution to test the hypothesis that temperature is the primary determinant of differences in fitness versus altitude. Each species attained greatest aboveground biomass, net photosynthetic rate, and effective quantum yield of photosystem II when grown under temperatures characteristic of the altitudinal range center. Although both species exhibited greater stem length, stomatal conductance, and intercellular CO2 concentration in hot than in cold temperatures, these traits showed much greater reductions under cold temperature for M. cardinalis than for M. lewisii. Survival of M. lewisii was also sensitive to temperature, showing a striking decrease in hot temperatures. Within each temperature regime, the species native to that temperature displayed greatest growth and leaf physiological capacity. Populations from the altitude range center and range margin of each species were used to examine population differentiation, but central and marginal populations did not differ in most growth or leaf physiological responses to temperature. This study provides evidence that M. cardinalis and M. lewisii differ in survival, growth, and leaf physiology under temperature regimes characterizing their contrasting low and high altitude range centers, and suggests that the species' altitude range limits may arise, in part, due to metabolic limitations on growth that ultimately decrease survival and limit reproduction.
  Oecologia 07/2006; 148(2):183-94. · 3.41 Impact Factor
• Article: The ecology and evolution of elevation range limits in monkeyflowers (mimulus cardinalis and M. Lewisii) /

  Amy Lauren. Angert
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  ABSTRACT: Thesis (Ph. D.)--Michigan State University. Dept. of Plant Biology Program in Ecology, Evolutionary Biology, and Behavior, 2005. Includes bibliographical references (leaves 150-168).
• Article: The ecology and evolution of elevation range limits in monkeyflowers (mimulus cardinalis and M. Lewisii) [microform] /

  Amy Lauren. Angert
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  ABSTRACT: Thesis (Ph. D.)--Michigan State University. Dept. of Plant Biology Program in Ecology, Evolutionary Biology, and Behavior, 2005. Includes bibliographical references (leaves 150-168). Microfiche. s