Maya Visions: The Quest for Autonomy in an Age of Globalization

Maya Visions: The Quest for Autonomy in an Age of Globalization. June C. Nash. New York: Routledge, 2001. 303 pp.     

Movement and Habitat Use of Canada Lynx During Denning in Minnesota

Abstract Establishing whether conditions are suitable for reproduction would help determine if immigration is necessary for Canada lynx (Lynx canadensis) to persist at the southern edge of the species range. We located den sites and monitored reproduction of radiocollared lynx in Minnesota from 2004 to 2006. Movement rates of denning females measured with Global Positioning System collars were similar to movement rates of lynx elsewhere. Female lynx with kittens used different habitat types in predenning, denning, and postdenning periods. Landscape composition at the scale of the foraging radius around a den site contained more lowland conifer, upland conifer, and regenerating forest than did home ranges or the area used by radiocollared lynx in Minnesota, USA. We used the spatial distribution of cover-type composition around known den sites to predict and map potential denning habitat in northeastern Minnesota. Techniques for identifying the spatial distribution of suitable denning habitat provide a biological basis for management actions that could enhance recovery of Canada lynx populations in the southern part of the species range.     

Sequential colonization by river periphyton analysed by microscopy and molecular fingerprinting

1. An artificial glass substratum was incubated in the River Danube for a period of 28 days in order to detect the sequential colonization of microorganisms.
2. Light and fluorescent microscopy showed that microalgae and the picoalgal fraction on the slides increased rapidly over the first 2 weeks of colonization. Diatoms were numerically the most abundant component of the periphyton and their species richness and diversity increased rapidly in the early phase of colonization whereas diversity subsequently increased moderately.
3. Evenness of the diatom community was initially high, lower in the intermediate phase and again higher later on. Succession involving early, intermediate and late colonizer species was observed. Community composition during the first 5 days of colonization was very different from later stages whereas there were only minor changes subsequently.
4. Molecular community analysis by means of terminal restriction fragment length polymorphism analysis of PCR amplified 16S rRNA and 18S rRNA genes pointed to even larger differences between the composition of samples obtained early and late in the period.
5. The number of 18S rRNA and 16S rRNA terminal restriction fragments (T-RF-s) was variable over the colonization period and the fragment patterns of both the bacterial and eukaryotic portion of the microbial community were variable, with most T-RF-s unique to a single sample, suggesting a wide diversity and dynamic properties of periphytic organisms.     

Laboratory experiments on factors affecting the activity of Gammarus pseudolimnaeus Bousfield

Factors such as current, light, food, substrate and time of year were found to influence the activity of specimens of Gammarus pseudolimnaeus maintained in stream tanks in the laboratory. Although there was seasonal variation, levels of diurnal and nocturnal activity were generally much higher when there was no current than when the water was running. Diurnal periodicity occurred but was not as pronounced as had been indicated in the field studies of previous workers. Although there was activity during the day, nocturnal levels were higher especially in specimens collected during the summer. When there was no current, and the lights were left on for 24 h, peak activity occurred at precisely the times when the lights normally would have been off. This strongly suggests that there is an endogenous component in the activity. The nocturnal activity showed a bigeminus pattern, and there was a seasonal change, with the general activity at its highest levels in summer. Activity was significantly greater during daylight both with and without current when there was no substrate present in the tanks. The behaviour of Gammarus appears to be complex and greatly influenced by combinations of the various factors.     

Effects of photoperiod and mating on sex pheromone production and release by oviparae of the aphid Schizaphis graminum

ABSTRACT. By extraction and bioassay procedures, it is shown that the sex pheromone released by oviparae of the greenbug, Schizaphis graminum (Rondani), during the daylight hours of a light: dark regime, is present in the tibia of the metathoracic legs only during daily photophases.
Shortly after mating, pheromone-emitting oviparae cease to produce as well as to release the pheromone. This mating-induced response requires that copulation be completed, and suggests the involvement of sperm or seminal substances transferred by the males to the oviparae during copulation.
Although multiple matings increase the number of eggs deposited by an ovipara, the mating-induced termination of pheromone production/ release would enhance the chances for mating of neighbouring oviparae. This would result in a further increase in egg production as well as in the number of genetically similar offspring, because neighbouring oviparae are most probably sisters. The phenomenon is discussed in terms of kin selection.     

Seasonal variation in growth of Mastomys natalensis (Rodentia: Muridae) in Morogoro, Tanzania

The paper describes seasonal growth variation in a free living population of Mastomys natalensis (Smith, 1834) from Morogoro, Tanzania. Growth patterns are associated with rainfall patterns. Young animals enter a growth stop at the end of the dry season (October-November) and growth is only resumed after the first heavy rains. Reproduction is more related to size than to age. If the heavy rains come early in the rainy season, animals start reproducing in the beginning of the year. The resulting young reach their maximal size without growth stop and start reproducing immediately. Possible causes for the growth stop are discussed. Growth phenomena are thought to explain at least partially the relation between rainfall and reproduction in Mastomys .

Résumé

Cet article décrit la variation de croissance saisonnière d'une population de Mastomys natalensis (Smith, 1834) vivant en libertéà Morogoro, en Tanzanie. Les graphiques de croissance sont associés à ceux des chutes de pluie. Les jeunes animaux connaissent un arrêt de la croissance à la fin de la saison sèche (octobre-novembre) et la croissance ne reprend qu'après les premières fortes pluies. La reproduction est plus liée à la taille qu'à l'âge. Si les fortes pluies surviennent tôt en saison des pluies, les animaux commencent à se reproduire au début de l'année. Les jeunes atteignent alors leur taille maximale sans avoir connu d'arrêt de croissance et commencent à se reproduire immédiatement. On pense que les phénomènes de croissance expliquent au moins partiellement la relation entre les chutes de pluie et la reproduction chez Mastomys .     

Interdecadal changes in at‐sea distribution and abundance of subantarctic seabirds along a latitudinal gradient in the Southern Indian Ocean

Long‐term demographic studies have recently shown that global climate change together with increasing direct impacts of human activities, such as fisheries, are affecting the population dynamics of marine top predators. However, the effects of these factors on species distribution and abundance at sea are still poorly understood, particularly in marine ecosystems of the southern hemisphere. Using a unique long‐term data set of at‐sea observations, we tested for interdecadal (1980s vs. 2000s) changes in summer abundance and distribution of 12 species of Albatrosses and Petrels along a 30° latitudinal gradient between tropical and Antarctic waters of the southern Indian Ocean. There were contrasting effects of climate change on subantarctic seabird distribution and abundance at sea. While subtropical waters showed the highest rate of warming, the species that visited this water mass showed the greatest changes in distribution and abundance. The abundance of Wandering Albatrosses (Diomedea exulans), White‐chinned Petrels (Procellaria aequinoctialis) and Giant Petrels (Macronectes sp.) declined markedly, whereas the other species showed contrasting trends or did not change. With the exception of the White‐chinned Petrel, these decreases were at least partly related to regional increase in sea surface temperature. The southward shift of Wandering Albatross and Prions (Pachyptila spp.) distributions could be ascribed to species redistribution or decrease in abundance due to warming of the subtropical waters. Surprisingly, White‐chinned Petrel distribution shifted northward, suggesting more complex mechanisms. This study is the first to document a shift in species range in the Southern Ocean related to climate change and contrasting abundance changes. It suggests that some species might experience more severe impacts from climate change depending on the water masses they visit. As climate changes are predicted to continue in the next decades, understanding species responses to climate change is crucial for conservation management, especially when their conservation status is critical or unknown.