Binocular vision and image location before Kepler

Archive for History of Exact Sciences - Kepler’s 1604 Optics (Ad Vitellionem Paralipomena) proposed among many other things a new way of locating the place of the image under reflection or...     

Effects of grass bug feeding and drought stress on selected lines of crested wheatgrass

The sequential effects of feeding by grass bugs ( Irbisia pacifica [Hemiptera: Miridae]) and of drought stress on the growth of 2 crested wheatgrasses (the hybrid Agropyron cristatum × desertorum and A. cristatum cv. 'Fairway') were investigated in a controlled greenhouse experiment. Growth rates of genotypes that were previously selected for resistance to grass bug feeding were not consistently greater than those of unselected genotypes when plants were exposed to bug feeding. Thus, the mechanism of resistance to bug feeding for the selected genotypes does not appear to be ""tolerance,"" i.e., rapid growth rates that allow the resistant genotypes to compensate for damage to green leaves caused by bug feeding. In addition, previous bug feeding did not exacerbate the effects of drought stress on plant growth rates; droughted plants generally had lower growth rates, independent of the presence or absence of prior bug feeding. Thus, we suspect that the selection process may have inadvertently favored green, robust plants rather than true resistance to bug feeding.     

Capture locations of two endangered rodents during a 1902 exploration of the Sacramento Mountains, New Mexico

We investigated localities from which Eutamias atristriatus Bailey, 1913 (= Tamias minimus atristriatus ) and Zapus luteus Miller, 1911 (= Zapus hudsonius luteus ) were collected during a 1902 survey in the Sacramento Mountains, New Mexico, by the United States Biological Survey. The locality from which the holotype of Eutamias atristriatus was collected is restricted to James Canyon rather than the Rio Pe?asco. Locality records indicate that the historical distribution of Zapus hudsonius luteus and its obligate wetland habitat were broader than currently realized.     

Simulation modeling of American marten ( Martes americana ) populations: vulnerability to extinction

American marten ( Martes Americana ) are medium-sized mammalian carnivores inhabiting forest communities across northern North America. Martens are susceptible to local extinction from habitat alterations, trapping, and other factors. We (RCL) developed a population model called VORTEX to estimate extinction probabilities for marten populations as a management tool. The model permits managers to simulate various levels of timber harvesting, commercial trapping, and other factors to estimate their effects on marten populations. This paper describes this model and illustrates its benefits by using marten data from the Greater Yellowstone Ecosystem of northwestern Wyoming. Results are preliminary. Populations of 50 and 100 martens were simulated. The most optimistic scenario with populations of 100 individuals, no trapping, no logging, and no migrants showed a probability (66%) of surviving 100 years. Extinction probabilities were sensitive to immigration and emigration rates. Numerous scenarios were simulated and showed a range of results. Results of population viability analysis can be translated into area requirements if densities are known or can be estimated. In turn, various habitat patches and interconnecting corridors can be examined for their ability to support viable marten populations. Population modeling is invaluable to ""adaptive management"" of martens as well as other species.     

Wildlife use of Douglas-fir dwarf mistletoe witches' brooms in the Southwest

We evaluated wildlife use of witches' brooms associated with infection by Douglas-fir dwarf mistletoe ( Arceuthobium douglasii ) in 6 mixed-conifer study areas in Arizona and 2 areas in New Mexico. We climbed 153 infected Douglas-firs ( Pseudotsuga menziesii ) and examined 706 witches' brooms for evidence of wildlife use. Even though we observed evidence of use by birds, most wildlife use was by small mammals, particularly red squirrels ( Tamiasciurus hudsonicus ). Red squirrels used witches' brooms for nesting, foraging, caching, and as latrines. Witches' brooms classified as Type II or III brooms, located close to the main bole with large platforms, and 5–10 m above the ground were the most frequently used by red squirrels.     

Species diversity and habitat of grassland passerines during grazing of a prescribe-burned, mixed-grass prairie

No published data exist on responses of grassland passerines and their habitat to combined grazing and burning treatments in northern mixed-grass prairie. At Lostwood National Wildlife Refuge (LNWR) in northwestern North Dakota, we monitored breeding bird occurrence, abundance, and habitat during successive annual grazing treatments (1998-2000) on 5 prescribe-burned, mixed-grass prairie management units (range = 50-534 ha, each burned 3-6 times in the previous 10-20 years). All breeding passerine species characteristic of upland, northern mixed-grass prairie were common (> 10% occurrence) during at least 1 of 3 years on burned and grazed units, except Chestnut-collared Longspur ( Calcarius ornatus ), which was uncommon. Vegetation was generally shorter and sparser than that found on 4 nearby units treated by fire only (1999; density, visual obstruction, and height, all P Molothrus ater ) occurred 2.4 times more frequently on burned and grazed units studied. Our data suggest that species diversity of breeding grassland passerines changes little during initial years of rotation grazing at moderate stocking rates in fire-managed, northern mixed-grass prairie at LNWR.     

Effects of dwarf mistletoe on growth and mortality of Douglas-fir in the Southwest

The effects of dwarf mistletoe ( Arceuthobium douglasii ) on growth and mortality of Douglas-fir ( Pseudotsuga menziesii ) were studied on 387 plots in mixed-conifer stands in three national forests in New Mexico and two in Arizona. Analyses of 8,570 trees showed that low infection ratings (dwarf mistletoe classes 1 or 2) had no significant effect on tree growth, but that losses increased markedly as infection severity increased. Average volume growth losses for trees over 10 inches in diameter were: dwarf mistletoe class 3, 10%; class 4, 25%; class 5, 45%; and class 6, 65%. Mortality of Douglas-fir in stands severely infested with dwarf mistletoe was three to four times that of healthy stands. These high losses confirm the need for silvicultural control of Douglas-fir dwarf mistletoe in the Southwest.     

Effects of dwarf mistletoe on spruce in the White Mountains, Arizona

Mortality of spruce in mixed conifer stands moderately to heavily infested with western spruce dwarf mistletoe was two to five times greater than in healthy stands in the White Mountains, Arizona. Ten-year volume growth loss for heavily infected spruce trees ranged from 25% to 40%. Estimates of growth loss for spruce on a stand basis ranged from 10% to 20% in heavily infested stands. Because western spruce dwarf mistletoe is prevalent in the White Mountains and causes increased mortality and reduced growth, its control should be included in management of mixed conifer stands there.     

Douglas-fir dwarf mistletoe parasitizing Pacific silver fir in northern California

Douglas-fir dwarf mistletoe ( Arceuthobium douglasii ) was found parasitizing Pacific silver fir ( Abies amabilis ) in northern Siskiyou County, California. This is the first report of Douglas-fir dwarf mistletoe on this host. Approximately 40% of the Pacific silver firs near heavily infected Douglas-firs were infected. The low level of infection on Pacific silver fir, unusually large swellings at the points of infection, and poor shoot production on infected branches indicate some degree of host-parasite incompatibility.     

Parasites of the bowhead whale, Balaena mysticetus

Blood, tissue, and organ samples from five bowhead whales were examined for ecto- and endoparasites. Two species of protozoans, four genera of diatoms, one species of trematoda, two species of nematoda, and one species of amphipoda "louse" were found. No blood parasites were recovered. The larval anisakid nematode, found in the submucosa of the forestomach of one whale, generated a prominent inflammatory response. Protozoans found in contents of the colon included a flagellate and a sarcodinan. The sarcodinan, which was common in the colon contents of one whale, belongs to the genus Entamoeba and probably represents an undescribed species. Ogomogaster plicatus , a trematode, was also identified. The data from this study are compared with previous lists of parasites for the bowhead whale and two other species of baleen whales. From the results presented, the previous list of parasites for the bowhead whale has been expanded to include eight additional genera and species.