Annual activity patterns of anurans in a seasonal neotropical environment

Summary At Panguana, a study in the upper Amazon basin, 7 different aquatic breeding sites of anurans were investigated from Nov. 1, 1981 to Oct. 31, 1982. Rainfall in this area is seasonal. Only 20% of the total annual precipitation was maesured during the dry period, which lasted from mid-March until mid-September 1982. The reproductive periods of the species were highly affected by the rainfall distribution. Calling males and/or gravid females of 46 species were found during the study period. 37.0% of the anuran species were exclusively, and 43.5% predominantly, active during the rainy season. Plots of 100 m² were established at 6 aquatic sites in primary rainforest. A total of 2126 frogs was counted; 93.2% of these were made during the rainy season. A maximum of 378 individuals were found during one check in the plot at the permanent pond. At this site high concentrations of individuals and large choruses were found at the beginning of the rainy season. As soon as favourable temporary aquatic sites were established, reproductive activities decreased at the permanent pond and increased at temporary breeding sites.     

Life cycle and seasonal development of post-embryonic Argas reflexus (Acari: Argasidae) at two thermally different locations in Central Europe

Seasonal development was investigated in the pigeon tick, Argas reflexus (F.) over a 5-year period. The ticks were kept in desiccators at two deposition sites with different temperature conditions: a warmer attic and a cooler outdoor aviary. The life cycle of A. reflexus consists of the egg, larva, a variable number of two to four nymphal instars and the adult stage. In the cooler aviary, the ticks passed, on average, fewer nymphal instars than in the attic. At both locations, ecdysis of the nymphs and adults occurred only during the summer months, with peak numbers of ticks finishing the moult in August. This consistent pattern was evident irrespective of the feeding date of the preceding developmental stage or the year of observation. The results strongly suggest that nymphs II, nymphs I and larvae fed later than in mid-July, August or September, respectively, entered a state of diapause and, thus, overwintered in the engorged state. Argas reflexus nymphs II from a laboratory stock that were deposited inside the attic showed a remarkably different seasonal pattern of development, even more than 1 year after their deposition. This suggests that a circannual rhythm may be involved in the ticks' seasonal timing. Mortality of the engorged ticks (from repletion to ecdysis of the following stage/instar) was below 1.5% in most cases, irrespective of the season and the location. Unfed larvae survived for a maximum of one year inside the attic, whereas the median survival period of unfed nymphs was at least 3 years at the same location. Based on the present results, the generation time from (F1) egg deposition to oviposition in the F2 generation might be 3-11 years in Central European A. reflexus, depending on the course of development (two or three nymphal instars) and the number of gonotrophic cycles (probably up to six) of the F1. The life span of a single tick might take approximately 7-11 years or even longer.     

Gender-based differences in substrate use during exercise at a self-selected pace

The aim of this study was to investigate gender-based differences in substrate use during exercise at a self-selected pace. Seventeen men and 17 women performed a maximal exercise test and a 20-minute bout of self-paced treadmill walking to determine carbohydrate and fat oxidation rates. Gas exchange measurements were performed throughout the tests, and stoichiometric equations were used to calculate substrate oxidation rates. For each individual, a best-fit polynomial curve was constructed using fat oxidation rate (g·min(-1)) vs. exercise intensity (percentage of maximal oxygen uptake, % VO(2)max). Each individual curve was used to obtain the following variables: maximal fat oxidation (MFO), the peak rate of fat oxidation measured over the entire range of exercise intensities; fat(max), the exercise intensity at which the MFO was observed; and fat(max) zone, range of exercise intensities with fat oxidation rates within 10% of fat oxidation rates at fat(max). Although the MFO was similar between genders, fat(max) was lower in men than in women. Similarly, the "low" and "high" borders of the fat(max) zone were lower in men than in women. During exercise at a self-selected pace, carbohydrate oxidation rates were greater in men than in women, despite no gender-based differences in fat oxidation rates. However, fat oxidation contribution to total energy expenditure (EE) was greater in women than in men, despite no gender-based differences in the exercise intensity. In conclusion, although both genders self-selected a similar exercise intensity, the contribution of fat oxidation to EE is greater in women than in men. Interestingly, both genders self-selected an exercise intensity that falls within the fat(max) zone.     

Annual and seasonal space use of different age classes of female wild boar Sus scrofa L.

In a radiotelemetric study, we analysed space use of 24 female specimens (14 family groups and 14 nonreproductive yearling females) out of 23 wild boar groups for periods between 3 and 39 months. Generally, wild boar used relatively small areas, showed high site fidelity but also a strong individual variation of home ranges, indicating a high flexibility in space use. Although age-specific differences were not statistically significant, female yearlings tended to have larger mean annual home ranges (1,185 ha MCP) than animals ranging in family groups (771 ha). Yearlings also showed a stronger shifting from spring to summer home ranges (2,345 m) and a tendency towards larger home range sizes in summer (791 ha MCP), compared to family groups (shift 1,766 m, MCP 461 ha). Yearlings displayed a dislocation of about 1 km of the annual centre in the first year after dividing from the mother. In contrast, in adults older than 2 years, the dislocation of the annual center was only 240 m.     

Environmental variability and acoustic signals: a multi-level approach in songbirds

Among songbirds, growing evidence suggests that acoustic adaptation of song traits occurs in response to habitat features. Despite extensive study, most research supporting acoustic adaptation has only considered acoustic traits averaged for species or populations, overlooking intraindividual variation of song traits, which may facilitate effective communication in heterogeneous and variable environments. Fewer studies have explicitly incorporated sexual selection, which, if strong, may favour variation across environments. Here, we evaluate the prevalence of acoustic adaptation among 44 species of songbirds by determining how environmental variability and sexual selection intensity are associated with song variability (intraindividual and intraspecific) and short-term song complexity. We show that variability in precipitation can explain short-term song complexity among taxonomically diverse songbirds, and that precipitation seasonality and the intensity of sexual selection are related to intraindividual song variation. Our results link song complexity to environmental variability, something previously found for mockingbirds (Family Mimidae). Perhaps more importantly, our results illustrate that individual variation in song traits may be shaped by both environmental variability and strength of sexual selection.     

Women at the Center: Life in a Modern Matriarchy

Women at the Center: Life in. Modern Matriarchy . Peggy Reeves Sanday. Ithaca, NY: Cornell University Press, 2002. xv + 270 pp.     

Subfamilies of CR1 non-LTR retrotransposons have different 5'UTR sequences but are otherwise conserved

CR1 elements and CR1-related (CR1-like) elements are a novel family of non-LTR retrotransposons that are found in all vertebrates (reptilia, amphibia, fish, and mammals), whereas more distantly related elements are found in several invertebrate species. CR1 elements have several features that distinguish them from other non-LTR retrotransposons. Most notably, their 3' termini lack a polyadenylic acid (poly A) tail and instead contain 2-4 copies of a unique 8 bp repeat. CR1 elements are present at approximately 100,000 copies in the chicken genome. The vast majority of these elements are severely 5' truncated and mutated; however, six subfamilies (CR1-A through CR1-F) are resolved by sequence comparisons. One of these subfamilies (i.e. CR1-B) previously was analyzed in detail. In the present study, we identified several full-length elements from the CR1-F subfamily. Although regions within the open reading frames and 3' untranslated regions of CR1-F and CR1-B elements are well conserved, their respective 5' untranslated regions are unrelated. Thus, our results suggest that new CR1 subfamilies form when elements with intact open reading frames acquire new 5' UTRs, which could, in principle, function as promoters.     

Anthoxanthum odoratum andA. alpinum: Life history parameters at two different altitudes

The closely related species, diploidAnthoxanthum alpinum Á. Löve etD. Löve and tetraploidAnthoxanthum odoratum L., have distinct distributions:A. alpinum is an arctic-alpine species, whileA. odoratum is a species of lower altitudes and more southerly latitudes. However, some authors suggest that both species are potentially able to maintain their populations in the distribution area of the other species. Reciprocal transplant experiments in two mountain localities (one withA. alpinum, the other withA. odoratum) were carried out to study the survival and vegetative and generative reproduction of tussocks of both species in the area of distribution of the other species. The mortality of tussocks ofA. alpinum was higher in the “alien” locality, the life span of tillers was greatly reduced and the size of tussocks decreased considerably during the experiment compared to its “native” locality. These results suggest that there was a lack of favourable microsites forA. alpinum in the “alien” locality probably caused by the presence of strong competitors.A. odoratum flowered far less in the “alien” locality (both on tussocks and tillers) compared to the “native” one. These results suggest that environmental conditions are not suitable for the flowering ofA. odoratum in the “alien” locality. We conclude thatA. alpinum could have been limited in extending its distribution into the area ofA. odoratum by the presence of strong competitors, whileA. odoratum could have been limited by its ability to reproduce by seed.     

Slow pace of life in tropical sedentary birds: a common-garden experiment on four stonechat populations from different latitudes

It has been hypothesized that organisms living at different latitudes or in different environments adjust their metabolic activity to the prevailing conditions. However, do differences in energy turnover simply represent a phenotypic adaptation to the local environment, or are they genetically based? To test this, we obtained nestling stonechats (Saxicola torquata) from equatorial Kenya (0 degrees N), Ireland (51.5 degrees N), Austria (47.5 degrees N) and Kazakhstan (51.5 degrees N). Birds were hand-raised and kept in Andechs, Germany. We measured their resting metabolic rates (RMR) and locomotor activity at an age of ca. 14 months (July) and 20 months (January), when birds went through postnuptial moult (July), and neither moulted nor exhibited enlarged gonads or migratory activity (January). RMR was generally higher during moult, but differed among populations: RMR was lowest in the resident Kenyan birds, higher in mostly sedentary Irish birds, and highest in migratory Austrian and Kazakhstan birds. Thus our data demonstrate that even in birds kept from early life under common-garden conditions, the ''pace of life'', as indicated by metabolic turnover, is lower in sedentary tropical than in north-temperate migratory individuals of the same species. Such intrinsically low energy expenditure in sedentary tropical birds may have important implications for slow development, delayed senescence and high longevity in many tropical organisms.     

Annual and seasonal changes in fine root biomass of a Quercus ilex L. forest

The biomass, production and mortality of fine roots (roots with diameter <2.5 mm) were studied in a typical Mediterranean holm oak (Quercus ilex L.) forest in NE Spain using the minirhizotron methodology. A total of 1212 roots were monitored between June of 1994 and March of 1997. Mean annual fine root biomass in the holm oak forest of Prades was 71±8 g m^–2 yr^–1. Mean annual production for the period analysed was 260+11 g m^–2 yr^–1. Mortality was similar to production, with a mean value of 253±3 g m^–2 yr^–1. Seasonal fine root biomass presented a cyclic behaviour, with higher values in autumn and winter and lower in spring and summer. Production was highest in winter, and mortality in spring. In summer, production and mortality values were the lowest for the year. Production values in autumn and spring were very similar. The vertical distribution of fine root biomass decreased with increasing depth except for the top 10–20 cm, where values were lower than immediately below. Production and mortality values were similar between 10 and 50 cm depth. In the 0–10 cm and the 50–60 cm depth intervals, both production and mortality were lower.     

The chaperone-like properties of mammalian inhibitor-2 are conserved in a Drosophila homologue

Phosphatase inhibitor-2 (I-2) is a mammalian phosphoprotein that binds to the catalytic subunit of type 1 serine/threonine phosphoprotein phosphatase (PP1c) and inhibits its activity in vitro. Recombinant PP1c differs from native PP1c in several biochemical criteria, including the requirement for Mn(2+), sensitivity to vanadate, and p-nitrophenyl phosphate (pNPP) phosphatase activity. I-2 can convert recombinant PP1c into a native-like activity in vitro. It has therefore been suggested that I-2 may act as a molecular chaperone for PP1 in vivo. We have identified a Drosophila homologue (I-2Dm) in a two-hybrid screen for PP1c-binding proteins. The sequence of I-2Dm is 35% identical with that of I-2, whereas the catalytic subunits themselves are >85% identical in flies and humans; however, we show that many biochemical properties of I-2 are conserved. Like I-2, I-2Dm can convert recombinant PP1c to a native-like activity. This strongly suggests that this ability is an essential, conserved role of I-2 and I-2Dm.     

Mouse histocompatibility-related genes are not conserved in other mammals

In addition to the genes for classical H-2 antigens, the H-2 complex of the mouse contains numerous homologous genes belonging to several distinct families. It is not known whether they have any functions. To address this question, I have investigated whether these genes are separately conserved in evolution. Subcloned 5' gene segments, encoding the variable domains, were used as hybridisation probes on genomic DNA blots of various mammals. Only the largest gene family, which includes the classical H-2/HLA genes, is detectable in humans and other mammals. The other gene families, including Qa-2 and T1a, are not conserved even in rodents. Most or all of their coding sequences are therefore redundant.