Species-specific growth responses of favositid corals to soft-bottom substrates

Gibson, Michael A. & Broadhead, Thomas W. 1989 07 15: Species-specific growth responses of favositid corals to soft-bottom substrates. Lethaia , Vol. 22, pp. 287–299. Oslo. ISSN 0024–1164.
Species of favositid corals from the Upper Silurian and Lower Devonian of Tennessee, USA, exhibit structural modifications related to corallum geometry, interfacial skeletal material, and biotic associations that enabled them to survive in terrigenous mud rich environments. Favosites conicus Hall (Lower Devonian) had a flat, holotheca-covered base and a radial pattern of colony growth, but apparently had a short life span and may not have survived beyond the first reproductive cycle (monocarpous). It was adapted for living between major episodes of terrigenous mud influx. F. foerstei (Lower Devonian) had a convex, pseudoholotheca-covered base and a modified axial pattern of colony growth. Its large size, in comparison to that of F. conicus , suggests a longer lived colony (polycarpous), in which continued upward and outward growth enabled it to survive episodic sediment influx. F. forbesi (Upper Silurian) exhibited radial growth to form either (1) a globose corallum that was symbiotic with the stalks of living crinoids permitting the colony to live entirely above the substrate, or (2) a Gorallum with a steeply convex, holotheca-covered base that represents a bottom-dwelling colony in which the rate of growth probably only slightly exceeded the rate of sediment accumulation. * Functional morphology, astogeny, paleoecology, Tabulata .     

Some population consequences of variation in preference among individual predators

A number of foraging studies have demonstrated that populations of predators rarely consist of individuals with identical preferences for particular types of prey. Variation among predators can lead to frequency-dependent changes in population preference, because those predators mat prefer the rarer type of prey generally have the greatest influence on population preference. In this study we develop a series of theoretical models which demonstrate how anti-apostatic selection (i.e. selection against the rare form) can arise out of (a) bimodal and (b) normal variation in preference among individuals of the same species. We show that population level anti-apostatic selection can occur even when individual predators show pro-apostatic selection (i.e. selection against the common form). Furthermore, patterns of population prey selection that arise out of variation in preference can potentially be pro-apostatic over one range of relative densities and anti-apostatic over another range of relative densities. Finally, we examine a case study involving predation by female waterboatmen Notonecta glauca and show that the variation in preference in this species is large enough to generate higher anti-apostatic selection than would be expected from the diet selected by the average individual.     

Effects of earthworms, nematodes, cultivations and host plants on Verticillium wilt of peach and cherry

Verticillium dahliae but not V. albo-atrum Berth was isolated from eight out of twenty-one stone fruit orchards surveyed for Verticillium wilt disease in western New York. Wilt incidence was related to the cultivation of tomato or legumes as previous or inter-crop with stone fruit trees. A limited cross species inoculation using isolates of V. albo-atrum and V. dahliae from woody and herbaceous plants showed that peach and cherry were susceptible to both species. The effect of V. dahliae on growth of cherry seedlings in the presence of Tylenchorynchus claytoni, Pratylenchus penetrans and Meloidogyne hapla was compared. P. penetrans and M. hapla produced more severe growth reduction than T. claytoni. The adverse effect of Verticillium on the growth of cherry seedlings was greater acting together with any one of the three nematodes than acting alone. V. dahliae was shown to be capable of passage through earthworms without loss of infectivity.     

Comparative physiology of field-grown tomatoes during ripening on the plant or retarded ripening in controlled atmospheres

Tomato fruits of six cultivars were harvested at three different stages of maturity or were harvested when mature-green and then stored in a modified gas atmosphere (2·5-4% O₂; 4% CO₂) for 2 months. The fresh and stored fruits were analysed for their contents of sugars, organic acids and free amino acids, while proteins were separated by discontinuous electrophoresis on polyacrylamide gels. In general, the low molecular weight components decreased during storage. A comparison of mature-green fruits before and after storage showed that although total protein was not decreased, a different electrophoretic pattern was obtained following controlled atmosphere (CA) storage. Thus, although controlled atmosphere storage repressed the loss of chlorophyll and synthesis of lycopene, carotenoids and xanthophylls, the biochemical parameters measured showed a controlled change towards the conditions exemplified by ripe fruits. This was not so marked in some cultivars as it was in others.