TO AGE, TO DIE: PARITY, EVOLUTIONARY TRACKING AND COLE'S PARADOX

The existence of semelparity or "big bang" reproduction (reproducing only once in a lifetime) and iteroparity (reproducing more than once in a lifetime) has led to many questions investigating the evolution or persistence of these strategies. Here we investigate semelparity and iteroparity for their evolutionary importance. A mathematical model is used to illustrate how a population's ability to evolve depends on this life-history trait, and how this rate of evolution impacts the individual. We find that the ability of a trait to evolve is greater toward a semelparous strategy and this expresses a fitness advantage. This leads to an optimality between survival, population tracking ability, and lifetime fecundity.     

羊肚菌属两种新疆新记录及一新变种

<正> 羊肚菌属约有15个种,在我国发现了5—8个种。羊肚菌属的所有种均可食,它们是真菌中味道鲜美的一类菌。在考察新疆天池自然保护区时,发现小顶羊肚菌中一个新变种:小顶羊肚菌卵褐变种(Morchella angusticeps Peck var.ovoideo-brunnea Mou var.nov.)。二个在新疆未曾报道过的种:小顶羊肚菌(M.angusticeps Peck)和粗柄羊肚菌(M.crassipes(Vent.)Pers.]。     

THE ADAPTATION OF FUNGI TO FUNGICIDES: ADAPTATION TO THIRAM, ZIRAM, FERBAM, NABAM AND ZINEB

The concentrations of thiram preventing germination of spores of Botrytis cinerea in drops of a 1% solution of sucrose, and on the surface of a sucrose-nitrate agar have been determined. Thiram had much less effect on germination in the agar medium, even when a purified agar was used. There was no growth on sucrose-nitrate agar if the concentration of thiram exceeded 31 p.p.m. Attempts to obtain strains able to grow at higher concentrations were unsuccessful.
Similar results were obtained with ziram, nabam and zineb.
Ferbam also was more effective in preventing spore germination in spore drops than on agar media; this effect was obtained with ordinary and with purified agar.
On a sucrose-nitrate agar generally there was no growth if the concentration of ferbam exceeded 125 p.p.m., but in one of forty-eight plates containing 250 p.p.m. ferbam, five slowly growing colonies were produced, and from these colonies arose mycelium which grew and sporulated rapidly on 500 p.p.m. ferbam agar. Agar disk inocula were transferred from these cultures to agar containing higher concentrations of ferbam and in this way, and by repeating the process, a strain was obtained which grew slowly but continuously, and sporulated on agar containing 5000 p.p.m. ferbam. However, the poor solubility of this fungicide made it difficult to assess quantitatively the degree of adaptation.
A proportion of the spores from this strain germinated in drops containing about twice the concentration of ferbam which prevented germination of parent spores.
The resistance of the mycelium of the resistant strain was not lost after repeated subculture on fungicide-free agar. The resistant strain was as susceptible as the parent strain to thiram, ziram, nabam and zineb.
Attempts to obtain strains of Venturia inaequalis resistant to thiram, ferbam, ziram and zineb were unsuccessful.