Saltcedar (Tamarix pentandra Pall.) and Russian olive (Elaeagnus angustifolia L.) invade moist pastures and rangeland and cause serious forage-production and soil-water losses. Our objective was to develop criteria for classifying sites relative to the likelihood of infestation by saltcedar and Russian olive, based on comparisons of soil and vegetation characteristics of infested and adjacent uninfested sites. Discriminant analyses indicated that Russian olive occurs on soils with low to medium concentrations of soluble salts (100–3500 ppm), whereas saltcedar occurs on soils with much higher soluble salt concentrations (700–15000 ppm). Characteristics of the herbaceous vegetation on sites infested with saltcedar or Russian olive differed distinctly from each other and from adjacent, uninfested sites. Frequency of occurrence of certain herbaceous understory species provided the most accurate basis for discrimination of infested and uninfested areas. Discriminant analysis may be of value in the development of infestation-proneness indices.

The growth response of Paspalum vaginatum S.W. and P. orbiculare Forst to different environmental conditions and the interactions between the two species were deter-mined experimentally in order to find out some of those factors which may be responsible for the species distribution. There was no difference in response (as measured by growth) of P. vaginatum to any of the soils tested but this was not so for P. orbiculare. P. vaginatum grew signifi-cantly better in waterlogged soil than in either moist or dry soil, while the soil moisture condi-tions had no significant effect on the growth of P. orbiculare. Salinity in the range of 0-50% that of sea water had no significant effect on the growth of P. vaginatum, however higher salinity significantly suppressed the growth. In P. orbiculare, salinity above 10% caused a signi-ficant decrease in growth to the extent that the species did not survive at 100% sea water concentration. In competition, P. vaginatum was the stronger competitor in red earth, the soil from its natural habitat, under saline conditions and in waterlogged conditions. The results are discussed in relation to the natural habitats of the species and used to explain, in part, their distribution.

Over one million pairs of seabirds breed annually on the Houtman Abrolhos island group, off the mid-western coast of Australia, the largest seabird breeding station in the eastern Indian Ocean. Eight of the 13 species that breed annually on Pelsaert Island are terns. Dietary samples (regurgitates) were collected from the five most numerous tern species from 1993 to 1999. The prey items identified were related to observations of foraging seabirds around the island. The largest species studied, the crested tern Sterna bergii, foraged mainly for reef fish over shallow reef flats near the breeding islands, as well as for schooling clupeid fish over coastal shelf waters. The smallest species, the roseate tern S. dougallii, also foraged within sight of its colonies, but over deeper waters than crested terns. Three larval fish species characteristic of continental shelf waters (a gonorhynchid, a goatfish and a bellowfish) figured prominently in the diets of roseate terns and three other tern species studied. Of these, only the sooty tern S. fuscata also ate squid and lanternfishes, foraging farthest (480–600 km) from its breeding island, off the shelf edge. The lesser noddy Anous tenuirostris and brown noddy A. stolidus took very similar taxa of prey and also overlapped considerably in their foraging ranges, about 180 km from their colonies, between the islands and the continental shelf edge. However, the lesser noddy took smaller fish than did the larger brown noddy. Although these five abundant tropical tern species, that bred sympatrically, showed some segregation in their diets and, more clearly, in their foraging ranges, considerable overlap of both aspects remained.

Re-analysis of data from Salisbury (1974) shows no significant relationship between seed size and habitat conditions, a relationship for which this paper is frequently cited as support. The discrepancy between the results reported here and those found in the original paper is due to Salisbury's ‘evidence’ being a table of congeneric pairs collected specifically because they possessed the target relationship. This paper emphasizes particularly the need for an unbiased sampling of species pairs in comparisons attempting to define ecological relationships. The analysis presented here represents the fourth such instance in which previously assumed robust examples of the relationship between seed size and habitat type are shown not to be so when the appropriate methods are used to account for relatedness among species.