Clonal repeatability of in vitro pollen tube growth rates in Oenothera organensis (Onagraceae)

The concept that pollen selection is an important force driving angiosperm evolution has received a lot of attention in recent years. In order for pollen competition to have evolutionary significance, heritable variation for pollen tube growth rate must exist. In this study, I tested the clonal repeatability, a measure of broad-sense heritability, of in vitro pollen tube growth rate in Oenothera organensis. Although I found significant phenotypic differences in pollen tube growth rate, the calculated clonal repeatability value of 9.4% indicates that heritability of pollen tube growth rate in this species is quite low. In contrast, both flower identity and plant identity had highly significant effects on pollen tube growth rate, suggesting that the environment may be more important than genotype in determining pollen performance in this species.     

Intestinal Parasitic Infections in Homosexual Men at a San Francisco Health Fair

In a sample of homosexual men attending a San Francisco Bay Area health fair, there were strikingly higher prevalence rates of intestinal parasitic infections compared with rates in a control group of health plan members who had a routine multiphasic health examination. Physicians treating homosexual men must be aware of the likelihood of such infections, whether or not the patients are symptomatic.     

Increased transparency due to changes in the algal size spectrum during experimental acidification in mesocosms

Acidification in mesocosms resulted in a rapid shift from picoplanktonto net plankton. This resulted in increased transparency relativeto controls, despite greater algal biomass in the acidifiedmesocosms. We observed a significant positive relationship betweentransparency and percent net plankton in the algal community.     

Fish-induced sediment resuspension: effects on phytoplankton biomass and community structure in a shallow hypereutrophic lake

An in situ mesocosm experiment was performed at Old Woman CreekEstuary, OH, to assess the importance of fish-induced sedimentresuspension in regulating phytoplankton biomass and communitystructure Six polyethylene tubes (1 m diameter x 2 m long) wereplaced into the lake, enclosing portions of the water columnand sediments Three duplicated treatments were established:(i) control, no fish, (ii) fish, stocked with small fish fromthe lake; and (iii) fish/net, stocked with fish, but into tubeswith coarse nets suspended above the sediments to prevent resuspension.Total P concentrations and algal biomass in the fish tubes becamemarkedly higher than the fish/net and control tubes. Centricdiatoms and small cryptomonads were the initial dominants. Inthe lake and fish tubes, this community was replaced by nanochlorophytes.In the fish/ net and control tubes, a very different successionoccurred, where large cryptomonads became dominant These resultsindicate that sediment nutrient resuspensions by fish activitiescan maintain a phytoplankton community in an immature state,with small r-selected dominants. When sediment nutrient resuspensionwas prevented (in the fish/net and control tubes), larger algalspecies increased in relative biovolume, regardless of whetherfish were present.