Phytogeography of the bryophyte floras of oak forests and páramo of the Cordillera de Talamanca, Costa Rica

Aim Central America is a biogeographically interesting area because of its location between the rich and very different biota of North and South America. We aim to assess phytogeographical patterns in the bryophyte floras of oak forests and páramo of the Cordillera de Talamanca, Costa Rica. Location Tropical America, in particular the montane area of Cordillera de Talamanca, Costa Rica. Methods The analysis is based on a new critical inventory of the montane bryophyte flora of Cordillera de Talamanca. All species were assigned to phytogeographical elements on the basis of their currently known distribution. Absolute and percentage similarities were employed to evaluate floristic affinities. Results A total of 401 species [191 hepatics (liverworts), one hornwort, 209 mosses] are recorded; of these, 251 species (128 hepatics, one hornwort, 122 mosses) occur in oak forests. Ninety‐three per cent of all oak forest species are tropical in distribution, the remaining 7% are temperate (4%) and cosmopolitan (3%) species. The neotropical element includes almost 74% of the species, the wide tropical element (pantropical, amphi‐atlantic, amphi‐pacific) only 19%. A significant part of the neotropical species from oak forests are species with tropical Andean‐centred ranges (27%). As compared with bryophyte species, vascular plant genera in the study region are represented by fewer neotropical, more temperate and more amphi‐pacific taxa. Bryophyte floras of different microhabitats within the oak forest and epiphytic bryophyte floras on Quercus copeyensis in primary, early secondary and late secondary oak forest show a similar phytogeographical make‐up to the total oak forest bryophyte flora. Comparison of oak forest and páramo reveals a greater affinity of the páramo bryophyte flora to temperate regions and the great importance of the páramo element in páramo. Surprisingly, oak forests have more Central American endemics than páramo. Main conclusions (1) Providing first insights into the phytogeographical patterns of the bryophyte flora of oak forests and páramo, we are able to confirm general phytogeographical trends recorded from vascular plant genera of the study area although the latter were more rich in temperate taxa. (2) Andean‐centred species are a conspicuous element in the bryophyte flora of Cordillera de Talamanca, reflecting the close historical connection between the montane bryophyte floras of Costa Rica and South America. (3) High percentages of Central American endemics in the bryophyte flora of the oak forests suggest the importance of climatic changes associated with Pleistocene glaciations for allopatric speciation.     

Abdominal pigmentation in Drosophila melanogaster females from natural Indian populations

Females of Drosophila melanogaster collected from five geographically distant populations in India were analysed for the intensity of pigmentation in the 5th, 6th and 7th segments of the abdomen. In all three segments, this intensity was found to vary among individuals of any given population, and, furthermore, different populations differ with respect to this phenotypic trait. Statistical analysis revealed significant intra- and interpopulational variation. A clinical pattern was detected: females from populations closer to the equator tended to have lighter cuticle, in which case differences between the three segments could not be detected and all three segments responded both independently and jointly to latitudinal variation, as indicated by a statistically significant positive correlation between latitude and pigmentation score. This is the first report on abdominal pigmentation analysis in natural populations of D. melanogaster that provides evidence that phenotypic flexibility reflects temperature differences, as a result of which abdominal pigmentation shows geographic differentiation.     

Using 137Cs technique to quantify soil conservation capacities of different ecosystems in Wolong Natural Reserve, southwestern China

Reliable information about soil conservation capacities of different natural ecosystems is an important reference for the design of targeted erosion and sediment control strategies. The objective of this paper is to quantify the soil conservation capacities of different natural ecosystems that can represent different climatic zones. The 137Cs technique has been used to estimate soil redistribution rates in different natural ecosystems over the past 40 years in Wolong Nature Reserve. The reserve, transiting from the Chengdu plain to the Qinghai-Tibet plateau, maintains rich ecosystems from subtropical to frigid.The net soil erosion rates of 5 selected ecosystems that represent a warm coniferous-broadleaf-mixed forest, a cold-resistant deciduous taiga forest, a cold-resistant shrub, an evergreen cold-resistant taiga servation capacities are reversed in order. The reference inventories for 137Cs in different ecosystems velop effective erosion and sediment strategies in areas with similar climates should consider natural ecosystem types.     

Effect of calcium on synthesis of dipicolinic acid inPenicillium citreoviride and its feedback resistant mutant

Dipicolinic acid synthesis inPenicillium citreoviride strain 3114 was inhibited by Ca²⁺ ions, but not by Ba²⁺, Cu²⁺or Fe²⁺. Among the metals tested, only Zn²⁺ inhibited the synthesis of dipicolinic acid and promoted sporulation. None of these metals reversed the inhibition by Ca²⁺ or Zn²⁺. A mutant 27133-dpa-ca selected for resistance to feedback inhibition by dipicolinic acid: Ca²⁺ complex showed cross-resistance to inhibition by dipicolinic acid: Zn²⁺. Both 3114 and271 33-dpa-ca excreted a number of aliphatic and amino acids during secondary metabolism of dipicolinic acid. In the presence of 1000 ppm of Ca²⁺, accumulation of citric acid and α-aminoadipic acid was completely inhibited under conditions of inhibition of dipicolinic acid in parent strain 3114 but not in the mutant. Citric acid with or without Ca²⁺ did not inhibit thede novo synthesis of dipicolinic acid in the strain 3114. In fact, citric acid in the presence of Ca²⁺ improved significantly rate of dipicolinic acid synthesis. Apart from resistance to feed back inhibition by dipicolinic acid: Ca²⁺ complex, mutant differed from the parent in three other aspectsviz. (i) dipicolinic acid synthesis was not subject to catabolite repression by glucose, (ii) sporulation as well as dipicolinic acid synthesis was dependent on the presence of Ca²⁺ ions in the medium and (iii) Mg²⁺ requirement for the mutant increased three fold. Higher requirement of the Mg²⁺ could be partially relieved by Ca²⁺ during secondary metabolism. The results support the inference thatde novo synthesis of dipicolinic acid is regulated through feedback inhibition by dipicolinic acid: Ca²⁺complex.     

Can whisker spot patterns be used to identify individual polar bears?

Studies of population dynamics, movement patterns and animal behavior usually require identification of individuals. We evaluated the reliability of using whisker spot patterns to noninvasively identify individual polar bears Ursus maritimus . We obtained the locations of polar bear whisker spots from photographs taken in western Hudson Bay, tested the independence of spot locations, estimated the complexity of each spot pattern in terms of information and determined whether each whisker spot pattern was reliable from its information content. Of the 50 whisker spot patterns analyzed, 98% contained enough information to be reliable, and this result varied little among observers. Photographs taken <50 m from polar bears were most useful. Our results suggest that individual identification of polar bears in the field based on whisker spot pattern variations is reliable. Researchers studying polar bear behavior or estimating population parameters can benefit from this method if proximity to the bears is feasible.     

Potential effects of elevated carbon dioxide on leaf-feeding forest insects

The elevated concentration of atmospheric CO₂ may result in a decline of leaf nutritional quality (especially N) and an increase in some kinds of defensive secondary components (such as phenolics). The changes in the phytochemistry of trees, combined with the effect of elevated CO₂ per se, have a potential negative influence on insect herbivores. Here, we review the effect of elevated CO₂ on the performance of leaffeeding forest insects at individual-level and community-level. The elevated CO₂ per se have little influence on the metabolism of insects. Over half of the tree-insect experimental systems show that the performance of individual insect become poorer under high-CO₂ grown trees; but the others show that the insects have just little or no response to the treatments. The direction and magnitude of the changes in the performance of insects could be mediated by various factors. The effects of treatment are strongly species-dependent. The magnitude of changes in the phytochemistry, the sensitivity and adaptive capacity of insects to the poorer leaf quality, the differences in plant growth conditions and experimental methods, and the mediated effects of other environmental factors (such as soil nutrient availability, light, temperature, O₃) were all closely related to the final performance of insects. However, the larvae’s consumption usually increased under enriched CO₂ treatment, which was widely thought to be a compensatory response to poorer plant quality. The experiments on forest community-level found identically a reduction in herbivory, which was contrary to the results from small-scale experiments. The changes in insect population and the actual response of consumption by leaf-feeding forest insects under CO₂ enrichment remain unclear, and more field-based experiments need to be conducted. __________ Translated from Chinese Journal of Applied Ecology, 2006, 17(4): 720–726 [译自: 应用生态学报]