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When considering cases in which territorial aggression occurs between species, we find that the relationship varies with the species' geographical and ecological distributions. If similarly sized species are narrowly sympatric or are widely sympatric but normally occupy different habitats, they both are interspecifically territorial and maintain mutually exclusive territories. If similarly sized species are widely sympatric and are common in the same habitats, one species is interspecifically aggressive and the other species flies away when chased. In this paper I present a model that explains these observations. I propose that interspecific territoriality can account not only for these differences in behavior and habitat but also for differences in foraging behavior and bill shape between sympatric species. The last three differences have usually been explained to be consequences of interspecific competition for food. The assumptions of the model proposed here are that (i) interspecific territoriality is misdirected intraspecific territoriality, (ii) territorial behavior prevents some individuals from breeding in optimal habitat, (iii) the individuals of one species are usually dominant over the other species in interspecific encounters, and (iv) of the habitats available to two interspecifically territorial species in their area of sympatry, one habitat is optimal for them both. This model is unusual in that a corollary of assumption (i) is that interspecific territoriality is not an adaptive characteristic, contrary to the assumptions of earlier writers. Nevertheless, the model is interesting and worth consideration because of the range of observable phenomena that are predicted.

A hypothetical population is considered in order to gain insight into the factors that may be responsible for the skewed distributions of dispersal distances that have been reported in vertebrates. In this population the most effective factor is the relative dominance of the indivduals in procuring breeding sites. If this is true of natural populations, dispersal permits each individual to maximize its chance to reproduce. Earlier explanations that selection for genotypes that are advantageous to the species but disadvantageous to individuals are not necessary to explain the skewed distributions of dispersal distances in vertebrate populations.

Methane clathrate is expected to be an important carbon-containing ice in the outer solar system. We investigate the effect of electron irradiation by coronal discharge on several simple hydrocarbons enclathrated in or mixed with H2O or H2O+NH3 in simulation of the effects of the solar wind, planetary magnetospheric particles, and cosmic rays on surfaces containing these ices in the outer solar system and interstellar space. H2O+CH4 clathrate, H2O+C2H6, H2O+CH4+NH3, H2O+C2H6+NH3, and H2O+C2H2 are all initially white ices, and all produce yellowish to brownish organic products upon charged particles irradiation. Significant coloration occurs with doses of 10(9) erg cm-2, corresponding to short interplanetary irradiation times. Uranian magnetospheric electrons penetrate to approximately 1 mm depth and deposit this dose in 8, 30, 65, 200, and 500 years into the surfaces of Miranda, Ariel, Umbriel, Titania, and Oberon, respectively. Further irradiation of the laboratory ice surface results in a progressive darkening and a more subdued color. For a conversion efficiency to solids G approximately equal to 1 molecule keV-1, the upper limit for the time for total destruction of CH4 and other simple hydrocarbons in the upper 1 mm is 5 x 10(4) years (Miranda) to 3 x 10(6) years (Oberon). Remote detection of CH4 is possible only when its replenishment rate exceeds the destruction rate at the depth probed by spectroscopy. Reflection spectroscopy or irradiated H2O+CH4 frost is compared with the spectra of several outer solar system objects and to other relevant organic and inorganic materials. Ultraviolet-visible and infrared transmission spectroscopy of the postirradiation residues is presented. Persistence of color and of CH4 ice bands on Triton and Pluto suggests ongoing surface activity and/or atmospheric haze. Over 4 x 10(9) year time scales, > or = 10 m of satellite and cometary surface material is processed by cosmic rays to a radiation-hardened ice-tholin mixture devoid of CH4. Preaccretional chemistry, exogenous materials, and endogenous organic chemistry all contribute to the spectral properties of icy satellites which accreted simple CH(O) molecules. Radiation darkening traces the deposition of mobilized or impact-exposed carbon-bearing volatiles on these satellites. More exhaustive experiments are necessary to work out the detailed relationships between initial composition, exposure age, and color/albedo.

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