The role of refugia and dispersal in primary succession on Mount St. Helens,Washington

Abstract. An intense lateral blast devastated Mount St. Helens in 1980, but forest understory species survived in some north‐slope ‘refugia’. We explored the effects of refugia on colonization of barren pumice in 1997 and 1998, 18 yr after the eruption. The seed rain of 23 colonizers came mostly from populations that had previously established in refugia. Parachutists had small, vagile seeds, parasailors had winged seeds, and tumblers were blown along the ground. The latter two groups are heavier and dispersed more slowly, but are more likely to survive. The proportion of the vegetation represented by wind‐dispersed species increased with distance from refugia. Parachutist's density declined with time and proximity to refugia. As vegetation adjacent to refugia developed, populations of parasailors and tumblers expanded, foreshadowing their dominance in more remote pumice. Refugia played a critical role in determining the rate and course of succession by providing fertile islands that permitted pioneers and dry meadow species to establish near barren pumice. Species that survived in refugia played a negligible role in colonization. This study showed that when refugia contrast sharply with new substrates, they accelerate recovery by facilitating the invasion of pioneer species.     

Some Morphological and Physiological Characteristics of Gram Negative Anaerobic Bacteria isolated from the Alimentary Tract of the Pig

S ummary . A collection of 100 strains of Gram negative anaerobic bacteria isolated from the alimentary tract of the pig has been divided into four groups on morphological and physiological grounds. The four groups resemble the genera Bacteroides, Sphaerophorus, Veillonella and Peptostreptococcus as described in Bergey's Manual (Breed, Murray & Smith, 1957).     

Evidence that serotonin neurons stimulate secretion of prolaction releasing factor.

The purpose of the present study was to determine if serotonin was stimulatory to prolactin release by inhibition of the dopaminergic system or by stimulating release of a prolactin releasing factor (PRF). We measured the amount of prolactin secreted after administration of 30 mg/kg of 5-hydroxytryptophan (5-HTP) to male rats pretreated with fluoxetine (10 mg/kg) and compared it with the amount of prolactin released in male rats treated with αmethyl-p-tyrosine methyl ester (αMT) or various dopamine receptor blocking agents. In every experiment the serotonergic stimulus provided by 5-HTP in fluoxetine-pretreated rats released considerably more prolactin than did treatment with αMT or dopaminergic blockers. We conclude that serotonin releases prolactin not by inhibiting dopaminergic neurons but rather by stimulating the release of PRF.     

Increased fertility in rhesus monkeys by breeding after the preovulatory LH surge.

Fertility in a rhesus monkey breeding colony was significantly increased by caging females with males immediately after detection of the preovulatory luteinizing hormone (LH) surge. LH was measured in daily serum samples by a rapid (24-hr) radioimmunoassay which used iodinated ovine LK as tracer and an antiserum to human LH.     

The Devonian nekton revolution

Klug, C., Kröger, B., Kiessling, W., Mullins, G.L., Servais, T., Frýda, J., Korn, D. & Turner, S. 2009: The Devonian nekton revolution. Lethaia, 10.1111/j.1502‐3931.2009.00206.x Traditional analyses of Early Phanerozoic marine diversity at the genus level show an explosive radiation of marine life until the Late Ordovician, followed by a phase of erratic decline continuing until the end of the Palaeozoic, whereas a more recent analysis extends the duration of this early radiation into the Devonian. This catch‐all approach hides an evolutionary and ecological key event long after the Ordovician radiation: the rapid occupation of the free water column by animals during the Devonian. Here, we explore the timing of the occupation of the water column in the Palaeozoic and test the hypothesis that ecological escalation led to fundamental evolutionary changes in the mid‐Palaeozoic marine water column. According to our analyses, demersal and nektonic modes of life were probably initially driven by competition in the diversity‐saturated benthic habitats together with the availability of abundant planktonic food. Escalatory feedback then promoted the rapid rise of nekton in the Devonian as suggested by the sequence and tempo of water‐column occupation. □Devonian, diversity, ecology, food webs, nekton, plankton, radiation.