Museum of Northern Arizona

About: Museum of Northern Arizona is a archive organization based out in Flagstaff, Arizona, United States. It is known for research contribution in the topics: Population & Canyon. The organization has 91 authors who have published 212 publications receiving 7551 citations.

Adaptive Nature of Insect Galls

Abstract: Major hypotheses on the adaptive significance of insect gall formation are reviewed: nonadaptive, plant protection, mutual benefit, nutrition, microenvironment, and enemy hypotheses. We evaluate the validity of each, and find the first three to be without merit because galls clearly have adaptive features for the insect, but few if any for the plant, and the galler has negative impact on the plant, making the relationship parasitic. Predictions are developed to enable testing of hypotheses, and tests are discussed. Nutrition and microenvironment hypotheses are supported, while the enemy hypothesis remains with several uncertain issues to be resolved. The evolution of the galling habit has followed two pathways, one via mining plant tissues and the other from sedentary external herbivores that then modify plant growth. In each route the sequence of selective factors was probably different, but improved protection from hygrothermal stress and improved nutrition are of primary importance, and protection from enemies probably reinforced the galling habit.

The Great American Biotic Interchange: Dispersals, Tectonics, Climate, Sea Level and Holding Pens

Abstract: The biotic and geologic dynamics of the Great American Biotic Interchange are reviewed and revised Information on the Marine Isotope Stage chronology, sea level changes as well as Pliocene and Pleistocene vegetation changes in Central and northern South America add to a discussion of the role of climate in facilitating trans-isthmian exchanges Trans-isthmian land mammal exchanges during the Pleistocene glacial intervals appear to have been promoted by the development of diverse non-tropical ecologies

Avian flocking in the presence of a predator

Abstract: Although there are several possible advantages of flocking1–3, many authors suggest that birds forage in groups to reduce the risk of predation (see citations in ref. 4). One version of the ‘many eyes’ hypothesis proposes that flocking allows individuals to spend less time scanning for predators and more time feeding5,6. However, flocking may also cause individuals to lose time and energy in fighting one another. The way a bird divides its time among these activities, its time budget, may depend on variables governing foraging requirements and the chance of predation7. As one such variable is the frequency of attacks by predators8, we flew a trained hawk over flocks of granivorous yellow-eyed juncos (Junco phaeonotus) to compare time budgets in the presence and absence of a predator. We found that time budgets changed after the predator was introduced and also that flock size increased in the presence of the predator.

Evolution by individuals, plant-herbivore interactions, and mosaics of genetic variability: The adaptive significance of somatic mutations in plants.

Abstract: Differences in the pattern of organization of organisms may lead to different patterns of evolution, genetics and ecology, Plants and animals differ in their fundamental patterns of organization. Plants consist of a series of repeating units that compete with one another, while animals consist of mutually interdependent systems that cannot compete. As a result, plants may be able to take advantage of somatic mutations in ways that are not available to animals. Somatic mutations arising in plants can be inherited by naturally occurring mechanisms of sexual and asexual reproduction. Long life span, large clone size, and the complete regeneration of buds each year may permit an indivdual plant or clone to evolve. Plants may even develop as mosaics of genetic variation. Evolution by individual plants and/or development as mosaics of genetic variation may prevent herbivores from breaking the defenses of their host plants. This evolution may also result in greater “fine tuning” to local environments leading to ecotypic variation.