The advent of geospatial environmental datasets has greatly enhanced the study of species distributions. Much research has aimed to estimate the bioclimatic envelope and assess the potential for rapid niche evolution in invasive species. The fundamental assumption of this approach is the range of each of the environmental variables defining a species’ native climate niche accurately represents constraints on the species’ distribution. In this study, we test for climate niche shifts in introduced populations of six species of cool-water fishes (Yellow Perch, Northern Pike, Walleye, Brook Trout, Rainbow Trout, and Lake Trout) in North America. Our results indicate significant niche differentiation has occurred in all species when comparing climate variables between native and introduced populations using univariate and multivariate analyses. In general, the trend is for introduced populations to occur in warmer, dryer climates with less seasonal variation in temperature compared to native ranges. Additional review of the data indicates a possible role of reservoirs in facilitating the niche shift as approximately half of all introduced populations are located in reservoirs. In conclusion, we suspect that shifts to climates with lower environmental selection pressures coupled with the hydrologic and thermal refugia offered by reservoirs are facilitating the establishment of populations outside of the native climate niche.
Dept of Biology, University of Rio Grande, Rio Grande, OH
P25 • David K. Cook, Jasmine N. Jordan, Alyssa A. Heisler, Charlene N. Miller, Junior Neal, Nicole M. Hughes
Effects of Regional Cloud Patterns on Microclimate and Shoot-Level Photosynthetic Gas Exchange in Picea engelmannii And Abies lasiocarpa At Treeline, Medicine Bow Mountains, Wyoming, USA
Summer atmospheric conditions in the Medicine Bow Mountains, USA are typified by clear mornings followed by convective, cumuliform cloud formation and thunderstorms in the afternoon. While cumuliform clouds generally reduce total incident sunlight via solar reflectance, it has recently been shown that partly-cloudy conditions can cause substantial increases in incident sunlight during cloud-gaps due to the summation of direct solar radiation with additional diffuse light scattered/reflected by cumulus clouds. Here we quantify the effects of cumulus solar-irradiance reflection (also described as the cloud-gap effect) on microclimate and photosynthetic gas exchange in saplings of two conifer species at treeline, Picea engelmannii and Abies lasiocarpa. Measurements were taken during both clear-sky and partly cloudy conditions (~10-70% of total sky covered by cumulus clouds) throughout the 2012 growing season within an alpine-treeline ecotone (3210 m elevation). Cumulus clouds generated dynamic fluctuations in photosynthetically active radiation (PAR), higher maximum PAR (>2500 µmol m-2 s-1), 2-3 fold increases in diffuse PAR, reduced mean and cumulative PAR, lower needle temperatures, and reduced leaf-to-air vapor pressure differences relative to clear-sky conditions. Cloud shade reduced total PAR by 24-94%, with corresponding declines in photosynthesis, needle temperatures, and transpiration occurring proportionally to cloud duration, frequency, and opacity. Despite increased diffuse light levels and greater maximum sunlight intensity during cloud-gaps, photosynthesis was never observed to be higher on partly cloudy days compared to clear days in either species, either during cloud-gaps or cloud-shade. Additional experiments tracking changes in photosynthetic gas exchange of individual shoots before, during, and after cumulus cloud-cover showed dramatic reductions in photosynthesis during cloud shade, followed by recovery to clear-sky rates during cloud-gaps. Reduced transpiration paired with high photosynthesis during cloud-gaps also resulted in increased, instantaneous water use efficiency relative to clear-sky measurements. Photoinhibition in response to these abrupt and dramatic changes in PAR levels were not apparent. When photosynthetic light-response curves were integrated into instantaneous PAR measurements on clear versus partly cloudy days each month, we estimated that cumulus cloud cover reduced daily carbon gain by 8-29% relative to clear-sky values. Significant reductions in transpiration under partly cloudy conditions resulted in significant alleviation of shoot water stress during most measurement months, relative to clear days, though the large variance between individual trees may have obscured results. We conclude that cumulus solar-irradiance reflection does not significantly increase carbon gain in this system during cloud-gaps. However, cumulus clouds may reduce daily and seasonal water stress by reducing needle temperatures and transpirational water loss during cloud-shade.
Dept of Biology, High Point University, High Point, NC
P26 • Alina Suedbeck, Tom J. Fink
How Lepidopteran Larval Spiracles are Really Made: The Lamellae
The external lamellae of larval spiracles are often easily noticed by eye or a stereo microscope. Despite their importance, the larval spiracle lamellar structure has been inadequately studied and described. Lamellae largely are considered to be fingerlike projections and in most cases lamellae are imaged with one or two surface Scanning Electron (SEM) micrographs. Larval lamellae in different species range from simple lamellae that can be described from two-dimensional micrographs, to in most cases lamellar carpets that must be imaged from three-dimensional anaglyphs or stereo pairs in order to correctly ascertain their structure and the differences between species. We find it necessary to image most larval spiracles with many stereo pairs taken from different angles of view. It is also necessary to make transverse cuts of the spiracles to see the true three-dimensional structure of the lamellae and to view the interior of the spiracles. In large species we also dissect the specimen so as to view the entire spiracle from the interior. Lamellar plates linked together to form lamellar carpets show an economy of structure so that air filtration tubercles, projections, or filaments are arranged only on the dorsum and laterally on the carpet that faces the other side. We will present images from over a dozen species, many through stereo anaglyphs, and some species will include first as well as mature and final instars. Many images are from live larvae imaged directly in a variable pressure SEM.
