The impact of selective logging on forest structure and tenrec populations in western Madagascar

Summary This paper reports on possible effects of selective logging on vegetation structure and its consequences for two tenrec species in a dry forest in western Madagascar. On a small scale semi-mechanized logging of less than 10 m³ per ha alters forest structure significantly. However on a large scale most of these changes are smaller than the variation of forest structure due to natural causes. The most profound ecological effect of logging is a reduction in the number of woody species in the regenerating cohort of trees. Potential longterm consequences of this feature are discussed. Microhabitat variables influencing the habitat utilization of two tenrec species,Echinops telfairi andTenrec ecaudatus, were identified in an area of unlogged forest. The conclusions derived from this analysis were then tested in other parts of the forest which had been modified by selective logging. Logging of the extent described above slightly impairs habitats forE. telfairi but has no effect onT. ecaudatus. Though the latter species is hunted extensively in the logged areas, loggingper se does not threaten the survival of either species.

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Résumé Cette étude met en évidence quelques effets de l'exploitation séléctive de la forêt sur la structure de la végétation et les conséquences pour deux espèces de tenrecs dans une forêt sèche à l'ouest de Madagascar. Dans un domaine limité, l'exploitation de bois de moins de 10 m³ par ha change considérablement la structure de la forêt. Mais si on considère une échelle plus grande, ces effets sont inférieurs à la variabilité naturelle. L'effet le plus grave de l'exploitation forestière sélective est la reduction du nombre d'espèces végétales ligneuses dans le processus de regénération naturelle de la forêt. Quelques conséquences possibles de cette réduction pour les animaux sont discutées. Quelques caractères distinctifs de la végétation qui influencent l'utilisation de l'habitat par deux espèces de tenrec,Echinops telfairi etTenrec ecaudatus, ont été identifiés dans une partie de la forêt qui n'a pas encore été exploitée. Les conclusions de cette analyse sont vérifiées dans une autre partie de la forêt qui a été modifiée par l'exploitation du bois. L'exploitation forestière sélective du bois détériore légèrement l'habitat pourE. telfairi, mais elle n'a pas d'effets remarquables surT. ecaudatus. L'exploitation sélective du bois favorise la chasse par l'ouverture de chemins d'accès. La chasse deT. ecaudatus est particulièrement intense, mais cependant ni l'une ni l'autre des espèces de tenrec considérées ne sont en danger d'extinction par cette form d'exploitationper se.

     

Detection of mRNAs correlated with proliferation of cells in suspension cultures of Catharanthus roseus

Gene expression correlated with proliferation was investigated in Catharanthus roseus (L.) G. Don. cells. Polyadenylated RNAs were isolated from cells in proliferative states or in nonproliferative states and the variations in the population and levels of mRNA were analyzed by in vitro translation followed by separation of the corresponding polypeptides by two-dimensional gel electrophoresis. Levels of two mRNAs increased in the actively cycling cells, while they were hardly detected in cells in stationary phase or in cells arrested by starvation of phosphate, sucrose or nitrogen. The molecular masses of the translated products of these two mRNAs were 53 and 60 kDa. No mRNAs were specifically synthesized in common among the various cultures of cells whose growth was arrested by nutrient starvation.     

Ecophysiological studies in Kalanchoë porphyrocalyx (Baker) and K. miniata (Hils et Bojer), two species performing highly flexible CAM

Preceding results, based on the determination of stable carbon isotope composition (₁₃C) of leaf tissues from various Kalanchoë species, suggested a close coincidence between the photosynthetic flexibility of the species and their habitat, life form and taxonomic position within the genus. The ability to shift from C₃-to Crassulacean Acid Metabolism (CAM)-type of photosynthesis seemed to concern in particular the more ancestral species in the genus and to be linked to epiphytism and changing climatic situations. For deeper insights into these interrelationships, physiological studies in controlled conditions were carried out on K. miniata and K. porphyrocalyx. These two species differ by their habitat preference and life form. Measurements were conducted on CO₂ exchange patterns, day/night fluctuation of malate content in the leaves and capacity of phosphoenolpyruvate carboxylase (PEPC). The results show that the 2 species can be considered as facultative CAM plants, with very high flexibility in their photosynthetic behaviour. The decrease in water availability seems to be a major factor triggering the shift from C₃ to the CAM mode. In K. miniata, 21 days of drought depressed CO₂ uptake to the level of CAM idling whereas in K. porphyrocalyx, CO₂ exchange was considerably more resistant. At least for K. miniata, short-day treatment was found to be a further CAM-inducing factor. The results are discussed in terms of their ecophysiological significance under the environmental conditions of the sites where the investigated species naturally grow.     

Resistance to shell breaking in two intertidal snails

The ability of shells to withstand shell breaking forces has been examined in two intertidal prosobranchs, Nucella lapillus and Littorina littorea , using four methods: measuring shell strength on a compressive testing machine, measuring the shell to body mass ratio, measuring the shell thickness and measuring the ability of crabs to break shells in aquarium experiments. Nucella lapillus consistently showed a relationship between shell vulnerability and environmental variables: the shells were easier to break at sites where rock and boulder movement was the least. Although some between-site differences were found in L. littorea shells, these were less than in N. lapillus and did not relate to environment variables: the shells were easier to break at sites where exposure to wave action was the least. Although some between-site differences were found in L. littorea shells , these were less than in N. lapillus and did not relate to environmental factors. However, both species appear to grow into a size refuge in which they are secure from predation by shore crabs at the sites where these crabs are commonest.     

“Ixoroid” secondary pollen presentation and pollination by small moths in the Malagasy treeletIxora platythyrsa (Rubiaceae)

The pollination biology ofIxora platythyrsa (Rubiaceae) was studied in NW. Madagascar. The plant displayed cream-yellow, nocturnally fragrant, nectariferous, tubular and strongly protandrous flowers. These had an ixoroid secondary pollen presentation mechanism: prior to anthesis, anthers exhausted their pollen onto unripe stylar heads. From this position pollen of male-stage flowers later adhered to primarily the probosces of small visiting nocturnal noctuid and geometrid moths. — Pollen was subsequently raked off moths' probosces by receptive, copiously papillose stigmas of female-stage flowers. Principal pollination adaptation was probably to the noctuid moth subfam.Sarrothripinae.     

African species of Chionanthus L.(Oleaceae) hitherto included in Linociera Swartz

Chionanthus L.(1753) and Linociera Swartz (1791) being considered congeneric.nine continental African species and three Madagascan species hitherto included in Linociera are transferred to Chionanthus .Synonymy, concise statements of distribution and a key are provided. Chionanthus richardsiae is a new species from Zambia; a biographical note on its collector, Mary Richards (1885–1977), is included.     

Transferrins,haptoglobins, and ceruloplasmins among tribal groups of Madagascar

Transferrin phenotypes of 403 Malagasy were determined by autoradiography after electrophoresis of plasma or serum. Three phenotypes, Tf C, Tf CD, and Tf D, were found. The frequency of Tf^D was 0.051 in the total sample, 0.041 in tribes of the Madagascar plateau, and 0.075 in tribes of the coastal and lowland regions. Haptoglobin phenotypes of 402 Malagasy were determined. The frequency of Hp¹ was 0.41 in the total sample, 0.38 in tribes of the plateau, and 0.49 in coastal-lowland tribes. There is a significant difference in the frequency of Hp¹ between the tribes of the plateau and those of the coastal and lowland regions. This confirms earlier observations of significant differences in frequencies of haptoglobins and hemoglobin S. Plasma or serum samples from 405 Malagasy were examined by electrophoresis to determine ceruloplasmin phenotypes. Seven distinct ceruloplasmin bands were observed. These were A, B, Galveston, Bridgeport, New Haven, Tananarive, and X, the last two described for the first time. Ten different phenotypes composed of one or two of the bands were observed. The frequency of the allele for ceruloplasmin B (CpB) was 0.78 in the total sample, 0.73 in tribes of the plateau, and 0.92 in coastal and lowland tribes. There is a significant difference in the frequency of this allele in the two major tribal groups, and this provides additional evidence of genetic differences between the peoples of the plateau and those of the coast and lowland regions of Madagascar.