A critique of traditional approaches to seaweed distribution in light of the development of vicariance biogeography
An overview of the primary approaches to seaweed biogeography is provided in light of the development of vicariance biogeography. Each approach is discussed with particular regard to the extent to which the methods and objectives are compatible with vicariance. Ecological biogeography is considered an offshoot of ecology and physiology and is more appropriate in determining current distributions of organisms and aspects of physiological ecology rather than the speciation history of monophyletic groups. The R/P quotient of Feldmann and distribution of algal life-forms do not fall within the aegis of vicariance and are considered useful only in a descriptive sense. The examination of seaweed spans propounded by Pielou is considered flawed because of the lack of dependence on monophyletic groups. The floristic school of analysis of many seaweed biogeographers is analagous to the panbiogeography of Croizat, and provides the basis for the more concrete phylogenetic hypotheses that are the basis for vicariance analysis. The latter is considered the best methodology for studying the relationship between patterns of cladogenesis and the distribution of constituent taxa.
Temperature, light, and photoperiod responses of some Northeast American and West European endemic rhodophytes in relation to their geographic distribution
The relationship between distributional boundaries and temperature responses of some Northeast American and West European endemic and amphiatlantic rhodophytes was experimentally determined under varying regimes of temperature, light, and daylength. Potentially critical temperatures, derived from open ocean surface summer and winter isotherms, were inferred from distributional data for each of these algae. On the basis of the distributional data the algae fall within the limits of three phytogeographic groups: (1) the Northeast American tropical-to-temperate group; (2) the warm-temperate Mediterranean Atlantic group; and (3) the amphiatlantic tropical-to-warm temperate group. Experimental evidence suggests that the species belonging to the northeast American tropical-to-temperate group(Grinnellia americana, Lomentaria baileyana, andAgardhiella subulata) have their northern boundaries determined by a minimum summer temperature high enough for sufficient growth and/or reproduction. The possible restriction of 2 species (G. americana andL. baileyana) to the tropical margins may be caused by summer lethal temperatures (between 30 and 35 °C) or because the gradual disintegration of the upright thalli at high temperatures (>30 °C) promotes an ephemeral existence of these algae towards their southern boundaries. Each of the species have a rapid growth and reproductive potential between 15–30 °C with a broad optimum between 20–30 °C. The lower limit of survival of each species was at least 0 °C (tested in short days only). Growth and reproduction data imply that the restrictive distribution of these algae to the Americas may be due to the fact that for adequate growth and/or reproduction water temperatures must exceed 20 °C. At temperatures ≦15 °C reproduction and growth are limited, and the amphiatlantic distribution through Iceland would not be permitted. On the basis of experimental evidence, the species belonging to the warm-temperate Mediterranean Atlantic group(Halurus equisetifolius), Callophyllis laciniata, andHypoglossum woodwardii), have their northern boundaries determined by winter lethal temperatures. Growth ofH. equisetifolius proceeded from 10–25 °C, that ofC. laciniata andH. woodwardii from 5–25 °C, in each case with a narrow range for optimal growth at ca. 15 °C. Tetrasporelings ofH. woodwardii showed limited survival at 0 °C for up to 4 d. For all members of the group tetrasporangia occurred from 10–20 °C. The southern boundary ofH. equisetifolius andC. laciniata is a summer lethal temperature whereas that ofH. woodwardii possibly is a winter growth and reproduction limit. Since each member of this group has a rather narrow growth and survival potential at temperatures <5 °C and >20 °C, their occurrence in northeast America is unlikely. The (irregular) distribution ofSolieria tenera (amphiatlantic tropical-to-warm temperate) cannot be entirely explained by the experimental data (possibly as a result of taxonomic uncertainties).
Mutiny Echoes: India, Britons, and Charles Dickens's A Tale of Two Cities
This essay asks what, if any, import the Indian ““Mutiny”” of 1857 had on A Tale of Two Cities (1859), Charles Dickens�s fictionalized account of the French Revolution. Begun shortly after the Indian uprising started, Dickens�s historical novel appears studiously to avoid any mention of events on the Indian subcontinent, even though these events preoccupied and enraged the author. Few scholars have attended to the question of A Tale of Two Cities and the ““Mutiny,”” but when they have, scholars have looked for analogies between India and Dickens�s account of the French Revolution. In this essay, by contrast, I examine A Tale of Two Cities in a larger context——of Britons9 response to the Uprising, of Dickens9s short stories and essays in Household Words in the years before the ““Mutiny”” and immediately after, of Dickens9s disenchantment with aspects of British culture, and of his need to articulate a national identity grounded in action. I argue that the events in India were the match that ignited Dickens9s already established midcentury interests in national identity, nobility, and masculine heroism. I do not wish to suggest that A Tale of Two Cities is an Indian ““Mutiny”” novel, but rather that it is a novel about the ““Making of Britons,”” an important endeavor for an author who was intensely dissatisfied with the Britain that he saw around him.