Joan Edwards

Diet shifts in moose due to predator avoidance

SummaryOn Isle Royale, Michigan, moose cows which have calves show a different distribution and diet from solitary adults and yearling moose. Solitary adults and yearlings follow a feeding pattern predicted from the location of high nutrient plant growth. In the presence of wolves, they feed on the ridges of the main island, where they take advantage of plants that leaf early; only later in the season do they move to the small outlying islands where plant phenology is delayed by the cold water of Lake Superior. Cows with calves deviate sharply from this pattern. They remain on the wolf-free small islands throughout the growing season. While on the islands, cows with calves eat a poorer quality diet than other moose. They switch to eating high quality spring and summer foods later than other moose and they eat significantly fewer high preference shrubs and significantly more herbs and low preference shrubs than other moose.This study suggests that in order to avoid predators, cows with calves sacrifice the high quality diet available on the main island. These data also suggest that the wolves not only affect prey numbers by direct kills but may also indirectly influence prey numbers by altering the diet of their prey. In this case, the reproductive cows, those individuals that contribute most directly to growth of the population, avoid predators but frequent poor feeding areas.

Mechanics without Muscle: Biomechanical Inspiration from the Plant World

Plant and animal biomechanists have much in common. Although their frame of reference differs, they think about the natural world in similar ways. While researchers studying animals might explore airflow around flapping wings, the actuation of muscles in arms and legs, or the material properties of spider silk, researchers studying plants might explore the flow of water around fluttering seaweeds, the grasping ability of climbing vines, or the material properties of wood. Here we summarize recent studies of plant biomechanics highlighting several current research themes in the field: expulsion of high-speed reproductive projectiles, generation of slow movements by shrinking and swelling cell walls, effects of ontogenetic shifts in mechanical properties of stems, flexible reconfiguration and material properties of seaweeds under crashing waves, and the development of botanically-inspired commercial products. Our hope is that this synopsis will resonate with both plant and animal biologists, encourage cross-pollination across disciplines, and promote fruitful interdisciplinary collaborations in the future.

Sphagnum Moss Disperses Spores with Vortex Rings

Fluid dynamics similar to those known to drive smoke rings shoot moss spores far and wide. Sphagnum spores, which have low terminal velocities, are carried by turbulent wind currents to establish colonies many kilometers away. However, spores that are easily kept aloft are also rapidly decelerated in still air; thus, dispersal range depends strongly on release height. Vascular plants grow tall to lift spores into sufficient wind currents for dispersal, but nonvascular plants such as Sphagnum cannot grow sufficiently high. High-speed videos show that exploding capsules of Sphagnum generate vortex rings to efficiently carry spores high enough to be dispersed by turbulent air currents. Spores launched ballistically at similar speeds through still air would travel a few millimeters and not easily reach turbulent air. Vortex rings are used by animals; here, we report vortex rings generated by plants.

Rising atmospheric CO2 is reducing the protein concentration of a floral pollen source essential for North American bees

At present, there is substantive evidence that the nutritional content of agriculturally important food crops will decrease in response to rising levels of atmospheric carbon dioxide, Ca. However, whether Ca-induced declines in nutritional quality are also occurring for pollinator food sources is unknown. Flowering late in the season, goldenrod (Solidago spp.) pollen is a widely available autumnal food source commonly acknowledged by apiarists to be essential to native bee (e.g. Bombus spp.) and honeybee (Apis mellifera) health and winter survival. Using floral collections obtained from the Smithsonian Natural History Museum, we quantified Ca-induced temporal changes in pollen protein concentration of Canada goldenrod (Solidago canadensis), the most widespread Solidago taxon, from hundreds of samples collected throughout the USA and southern Canada over the period 1842–2014 (i.e. a Ca from approx. 280 to 398 ppm). In addition, we conducted a 2 year in situ trial of S. canadensis populations grown along a continuous Ca gradient from approximately 280 to 500 ppm. The historical data indicated a strong significant correlation between recent increases in Ca and reductions in pollen protein concentration (r2 = 0.81). Experimental data confirmed this decrease in pollen protein concentration, and indicated that it would be ongoing as Ca continues to rise in the near term, i.e. to 500 ppm (r2 = 0.88). While additional data are needed to quantify the subsequent effects of reduced protein concentration for Canada goldenrod on bee health and population stability, these results are the first to indicate that increasing Ca can reduce protein content of a floral pollen source widely used by North American bees.

Packera insulae-regalis (Asteraceae, Senecioneae), a new species endemic to Isle Royale, Michigan, U.S.A.

Packera insulae-regalis (Asteraceae, Senecioneae) is a new species that is only known from one population occurring near the summit of Mount Franklin on Isle Royale, Michigan, U.S.A. It resembles both P. paupercula and P. indecora but is hexaploid, whereas the former has diploid and tetraploid populations and the latter is octoploid around the western Great Lakes. Whereas most species of Packera are self-incompatible (as is P. paupercula) and a few are self-compatible (as is P. indecora), P. insulae-regalis is unique in the genus in being partially self-compatible, as far as is known. Its origin post-glacially by hybridization between these two species is hypothesized.

Coevolution: Puff Pollination in Tropical Flowers

A new study shows that birds plucking anthers of the Melastome, Axinaea, demonstrate a novel bird pollination mechanism. Each stamen of Axinaea offers a nutrient-rich, berry-like food body that, when bitten, releases a puff of pollen allowing transfer to stigmas by wind or the pollen-dusted bird.