The initiation of metamorphosis in marine invertebrates is strongly linked to the environment. Planktonic larvae typically are induced to settle and metamorphose by external cues such as coralline algae (Corallinaceae, Rhodophyta). Although coralline algae are globally abundant, invertebrate larvae of many taxa settle in response to a very limited suite of species. This specificity impacts population structure, as only locations with the appropriate coralline species can attract new recruits. Abalone (Gastropoda, Haliotidae) are among those taxa in which closely related species are known to respond to different coralline algae. Here we identify highly inductive natural cues of the tropical abalone Haliotis asinina. In contrast to reports for other abalone, the greatest proportion of H. asinina larvae are induced to settle and metamorphose (92.8% to 100% metamorphosis by 48 h postinduction) by articulated corallines of the genus Amphiroa. Comparison with field distribution data for different corallines suggests larvae are likely to be settling on the seaward side of the reef crest. We then compare the response of six different H. asinina larval families to five different coralline species to demonstrate that induction by the best inductive cue (Amphiroa spp.) effectively extinguishes substantial intraspecific variation in the timing of settlement.

Resprouting plants provide an interesting test to the generality of plant allometric relationships. The ability to rapidly resprout after disturbance also makes weeds more difficult to control. We performed a glasshouse experiment to investigate regrowth of an invasive plant (alligator weed, Alternanthera philoxeroides (Martius) Grisebach) after an experimental mowing treatment. Nutrient levels and biomass accumulation were measured weekly for five weeks, and carbohydrate levels were measured when regrowth was quickest. After five weeks, the biomass of treatment plants was similar to that expected from a growth curve fitted to undamaged control plants. Treatment plants, however, had a higher below-ground biomass, and a higher ratio of stem to leaf biomass than expected. The regrowing material also had a lower nutrient concentration. Both the rapid regrowth and the change in morphology make the mechanical control of alligator weed more difficult, and may, in part, be responsible for the invasiveness of this plant.

The frequency and intensity of disturbance on living coral reefs have been accelerating for the past few decades, resulting in a changed seascape. What is unclear but vital for management is whether this acceleration is natural or coincident only with recent human impact. We surveyed nine uplifted early to mid-Holocene (11,000-3700 calendar [cal] yr B.P.) fringing and barrier reefs along ϳ27 km at the Huon Peninsula, Papua New Guinea. We found evidence for several episodes of coral mass mortality, but frequency was Ͻ1 in 1500 yr. The most striking mortality event extends Ͼ16 km along the ancient coastline, occurred ca. 9100-9400 cal yr B.P., and is associated with a volcanic ash horizon. Recolonization of the reef surface and resumption of vertical reef accretion was rapid (Ͻ100 yr), but the post-disturbance reef communities contrasted with their pre-disturbance counterparts. Assessing the frequency, nature, and long-term ecological consequences of massmortality events in fossil coral reefs may provide important insights to guide management of modern reefs in this time of environmental degradation and change.

Disturbance is a key component of many successful plant invasions. However, interactions among natural and anthropogenic disturbances and effects of these interacting disturbances on invasive plants and desired vegetation are rarely examined. We investigated the effect of anthropogenic disturbance (herbicidal and mechanical) along a natural inundation gradient (20-282 days) on the biomass and resource allocation of the invasive wetland plant, alligator weed (Alternanthera philoxeroides), and two co-occurring competitor plants, the introduced grass, kikuyu (Pennisetum clandestinum), and the native grass, couch (Cynodon dactylon), over a 2-year period. In the absence of additional disturbance, kikuyu biomass was negatively affected, alligator weed biomass was positively affected, and couch biomass was not affected by inundation disturbance. In addition, kikuyu was not affected by the selective removal of alligator weed, while couch increased in wetter habitats where kikuyu was absent due to inundation stress. This suggests that kikuyu is a superior competitor in drier habitats and inundation facilitates the invasion of alligator weed, while couch is an inferior competitor to both kikuyu and alligator weed and is therefore suppressed across its entire niche by these two introduced species. Mowing alone had no effect on the biomass of the species, suggesting the plants are equally tolerant of shoot removal. Selective herbicide reduced alligator weed biomass by 97.5% and the combination of selective herbicide and mowing reduced the biomass of alligator weed significantly more than herbicide alone, by 98.6% compared with un-manipulated controls. To predict community change and prevent sequential exotic plant invasions after weed removal, it is necessary to consider the interacting effects of disturbance and the niche space of invasive species in the local propagule pool.

Understanding the mechanisms behind the successful colonization and establishment of introduced species is important for both preventing

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Dialysis-dependent patients with ischemic heart disease have poor survival despite intervention. Coronary artery bypass achieves fewer composite adverse events and better quality of life than stenting. Symptoms and coronary anatomy should dictate treatment decisions in dialysis-dependent patients.

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