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Alpine herbivory on Mount Kenya / Truman P. Young

Public in Tropical alpine environments : plant form and function / Philip Rundel (1994) Titre : Alpine herbivory on Mount Kenya Type de document : texte imprimé Auteurs : Truman P. Young, Auteur ; Alan Smith, Auteur Importance : pp. 319-335 Langues : Anglais (eng) Résumé : "he savannas of East Africa, perhaps more than anywhere in the world, are known for dramatic plant–animal interactions. Although large herbivores are less common above timberline than below it in East Africa, herbivory is also a powerful force in Afroalpine plant ecology. Many vertebrates and invertebrate herbivore species occur above treeline on Mount Kenya (Moreau 1944; Coe 1967; Jabbal & Harmsen 1968; Coe & Foster 1972; Mulkey et al 1984; Young 1991; Young & Evans 1993). Herbivores influence the distribution of plant species, the size structure of populations, and the success of individual plants on Mount Kenya. Long-term studies of giant rosette Lobelia and Senecio species have brought to light a number of interesting patterns of herbivory that have major impacts on the biology of these species. Lobelia The two high alpine giant rosette lobelias on Mount Kenya are Lobelia telekii and L. keniensis. Mount Kenya lobelias are subject to herbivory from a variety of animal species (Table 18.1). None of the herbivores is host-specific, except perhaps the coleopteran larvae associated with L. telekii roots. Most of these herbivores have only minor effects. However, Lobelia populations near hyrax colonies have suffered severe predation. The leaves and stems of both Lobelia species are protected by a bitter latex containing anti-herbivore compounds (Mabberley 1975). Although this may limit the activity of their herbivores, it far from renders the plants invulnerable. Type de publication : article de livre Référence biblio : Young T., Smith A., 1994 - Alpine herbivory on Mount Kenya. In : 1994 - Tropical alpine environments : plant form and function. Cambridge University Press, 319-335. ID PMB : 7604 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=7604

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Population biology of Mount Kenya lobelias / Truman P. Young

Public in Tropical alpine environments : plant form and function / Philip Rundel (1994) Titre : Population biology of Mount Kenya lobelias Type de document : texte imprimé Auteurs : Truman P. Young, Auteur Importance : pp. 251-272 Langues : Anglais (eng) Catégories : [ZG] Kenya Résumé : "Tropical alpine environments impose unique selection pressures on plants, producing a number of special adaptations. Among these are caulescent and acaulescent rosettes, nyctinasty, semelparity, and resistance to nightly frost. For each of these adaptations there are a number of possible evolutionary explanations. To discriminate between among explanations, and to understand better tropical alpine environments in general, integrated long-term studies of particular species are necessary. Such studies include morphology, ecological physiology, demography and reproductive biology. Long-term population biology studies of tropical alpine plants are rare; most are presented in this volume. These studies are helping us to understand the nature of adaptation in tropical alpine environments. Giant rosette plants make ideal research subjects for a number of reasons. They are conspicuous and characteristic members of virtually all tropical alpine communities. Their morphologically discrete form makes their growth and individual dynamics easy to quantify. Lastly, they are relatively long-lived, enabling us to examine the effects of long-term changes in local environment. Since 1977, I have been studying two closely related giant rosette species on Mount Kenya, Lobelia telekii and L. keniensis. I present here a summary of the first 7 years of that study, concentrating on the comparative population biology of these two species. A number of factors make Mount Kenya lobelias particularly attractive as research subjects. (i) The alpine environment of Mount Kenya is one of the most intensively studied ecosystems in the tropics (Hedberg 1957, 1964; Coe 1967; Coe & Foster 1972; Young & Peacock 1985; Young 1990a)." (source : auteur) Type de publication : article de livre Référence biblio : Young T.-P., 1994 - Population biology of Mount Kenya lobelias. In : 1994 - Tropical alpine environments : plant form and function. Cambridge University Press, 251-272. ID PMB : 7607 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=7607

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Population biology of Senecio keniodendron (Asteraceae) - an afroalpine giant rosette plant / Alan Smith

Public in Tropical alpine environments : plant form and function / Philip Rundel (1994) Titre : Population biology of Senecio keniodendron (Asteraceae) - an afroalpine giant rosette plant Type de document : texte imprimé Auteurs : Alan Smith, Auteur ; Truman P. Young, Auteur Importance : pp. 273-293 Langues : Anglais (eng) Catégories : [Espèces (in biblio)] Senecio Résumé : "Senecio keniodendron (Asteraceae) is an abundant and widespread giant rosette species endemic to the alpine zone of Mount Kenya (lat 0°), Kenya. Along with Senecio brassica, it forms a dominant component of the alpine plant community, and shows a high degree of morphological convergence with giant rosette genera in other tropical alpine areas (Hedberg & Hedberg 1979; Smith & Young 1987; Smith, Chapter 1). Here we summarize studies of S. keniodendron population biology carried out between 1977 and 1985, and briefly compare these results with those both for S. brassica, and for the convergent Andean genus Espeletia (Asteraceae). Senecio keniodendron occurs most commonly on upper slopes and ridges from c. 3700–4600 m elevation. Adult densities generally range from 1 to 10 plants per 100 m2, with greatest densities on talus slopes between 4000 and 4200 m. The mean height of S.keniodendron plants is significantly positively correlated with slope angle (Figure 15.1; r = +0.60; p < 0.001). Senecio keniodendron is replaced by S. brassica on lower slopes and valley floors; S. brassica has a lower elevational range than S. keniodendron – c. 3400–4400 m. The upper limit of growth for S. keniodendron (4600 m) may be due to a combination of drought and freezing stress (see also Perez 1987, on Andean Espeletia). Figure 15.2 shows the surface response curves for the densities of S. keniodendron (p < 0.04) and S. brassica (p < 0.01) im the Teleki Valley, relative to elevation and slope." (source : auteurs) Type de publication : article de livre Référence biblio : Smith A., Young T., 1994 - Population biology of Senecio keniodendron (Asteraceae) - an afroalpine giant rosette plant. In : 1994 - Tropical alpine environments : plant form and function. Cambridge University Press, 273-293. ID PMB : 7606 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=7606

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