Valley Population Research Articles

La séquence loessique de Kurtak (Bassin de l'Iéniséi, Sibérie) : un enregistrement de référence pour le stade de Karga (SIM 3)

The loess-palaeosol succession of Kurtak, along the western slope of the Yenisei Valley, is one of the best documented Late Pleistocene sequences in southern Central Siberia. The present paper deals with the Kurtak Pedocomplex and with the Chani Bay Complex preserved on the plateau and in a lateral depression respectively, which correspond to the Karga Stage (MIS 3). For this sequence we obtained a detailed palaeoclimatic succession based on pedological and palynological data recording 14 short interstadial periods. The chronology of this record is well established by ca 100 radiocarbon dates on charcoal and wood remains, ranging from 42,520 to 25,710 BP. Botanical analysis shows a steppe-like vegetation with small tree populations (spruce, pine, birch) in lateral valleys during the colder periods. During the interstadial episodes spruce populations grew denser in the valleys, while scattered spruce, larch and pine trees expanded on the plateau. Therefore, the Kurtak Pedocomplex and Chani Bay Complex provide a unique climatic record for MIS 3, similar to the middle pleniglacial succession of the Dinkel Valley in the Netherlands and to loess-palaeosol records of Eastern and Central Europe. This means that the Siberian record shows a climatic sequence of global significance, and that the environmental conditions during MIS 3 were highly unstable at the Eurasian continent.

A karyological study of swamp and dry valley populations of Siberian fir (Abies sibirica Ledeb.)

The karyological data on populations of Siberian fir (Abies sibirica Ledeb.) growing in lowland swamp and dry valleys are given. The diploid set of both populations included 24 chromosomes (2n = 24). Polykaryogram analysis revealed seven pairs of metacentric and five pairs of submetacentric chromosomes. The revealed differences between the populations included the absolute length of chromosomes, number of nucleolar organizer regions, and number of nucleoli. Changed chromosome numbers (mixoploidy and aneuploidy) as well as chromosomal aberrations were recorded. For the first time, mitosis was studied in this species and anaphase/telophase aberrations were revealed. The population of Siberian fir growing under extreme conditions of lowland swamp featured the widest range of mutations.

Exogenous vasotocin alters aggression during agonistic exchanges in male Amargosa River pupfish ( Cyprinodon nevadensis amargosae)

Pupfishes in the Death Valley region have rapidly differentiated in social behaviors since their isolation in a series of desert streams, springs, and marshes less than 20,000 years ago. These habitats can show dramatic fluctuations in ecological conditions, and pupfish must cope with the changes by plastic physiological and behavioral responses. Recently, we showed differences among some Death Valley populations in brain expression of arginine vasotocin (AVT). As AVT regulates both hydromineral balance and social behaviors in other taxa, these population differences may indicate adaptive changes in osmoregulatory and/or behavioral processes. To test whether AVT is relevant for behavioral shifts in these fish, here we examined how manipulations to the AVT system affect agonistic and reproductive behaviors in Amargosa River pupfish ( Cyprinodon nevadensis amargosae). We administered exogenous AVT (0.1, 1, and 10 μg/g body weight) and an AVP V 1 receptor antagonist (Manning compound, 2.5 μg/g body weight) intraperitoneally to males in mixed-sex groups in the laboratory. We found that AVT reduced the initiation of aggressive social interactions with other pupfish but had no effect on courtship. The effects of AVT were confirmed in males in the wild where AVT (1 μg/g body weight) reduced the aggressive initiation of social interactions and decreased aggressive responses to the behavior of other males. Combined, these results show that AVT can modulate agonistic behaviors in male pupfish and support the idea that variation in AVT activity may underlie differences in aggression among Death Valley populations.

Phenotypic Flexibility in a Novel Thermal Environment: Phylogenetic Inertia in Thermogenic Capacity and Evolutionary Adaptation in Organ Size

The goal of our work was to understand the role of a novel thermal environment in shaping the phenotypic expression of thermogenic capacity and organ size. To examine this we compared two populations of the South American rodent Phyllotis darwini from different altitudes (Andean and valley populations), taking advantage of the fact that this genus originated at high altitude in the Andean plateau. DNA mitochondrial analysis showed that the two populations were separated and then experienced different thermal regimens for at least the last 450,000 yr. We expected the two populations of P. darwini to present more metabolic and organ size similarities if phylogenetic inertia had been an important factor. In this sense, phylogenetic inertia means that the valley population would retain evolutionary adaptations of high altitude: a greater phenotypic flexibility in both physiological and morphological traits. In general, our results indicate that the actual thermogenic capacities (magnitude and flexibility) of the valley population are a consequence of phylogenetic inertia. On the other hand, results for organ size (magnitude and flexibility) could suggest that this population would have adapted to the less seasonal central valley.

EL PERÍODO FORMATIVO EN LOS VALLES DEL NORTE DE CHILE Y SUR DE PERÚ: NUEVAS EVIDENCIAS Y COMENTARIOS

Thirteen years after our article Formativo en el Norte Grande de Chile (Munoz 1989), here we reanalyse the period, taking into consideration new evidence obtained in the far south of Peru and far north of Chile particularty during the last ten years. This information permits us to establish new hypotheses regarding reconstruction of society and culture during the Formative period, highlighting the importance of the local population, knowledge of the landscape, complexity of the process of sedentism in the local population and contacts with populations of other valleys and other regions of the Pacific watershed of the Andes.

HLA-A, -B, -DQA1, -DQB1 and -DRB1 alleles in a Pasiego (Pas Valley) population from Spain

HLA-A, -B, -DQA1, -DQB1 and -DRB1 alleles in a Pasiego (Pas Valley) population from Spain

SURVIVAL, MOVEMENTS, AND HARVEST OF EASTERN PRAIRIE POPULATION CANADA GEESE

SURVIVAL, MOVEMENTS, AND HARVEST OF EASTERN PRAIRIE POPULATION CANADA GEESE

Variation in vasotocin immunoreactivity in the brain of recently isolated populations of a death valley pupfish, Cyprinodon nevadensis

Pupfishes in the Death Valley region of California and Nevada comprise a monophyletic group of populations that became isolated in remote streams and springs over the past 20,000 years. These aquatic habitats show considerable ecological diversity, and allopatric populations have evolved differences in morphology and behavior. Here we investigated whether the divergence of pupfish populations in Death Valley might be associated with changes in arginine vasotocin (AVT). We used immunocytochemistry to compare the expression of AVT in the brain of Amargosa pupfish ( Cyprinodon nevadensis) from two Death Valley populations: (1) the Amargosa River—a highly variable desert stream containing the Cyprinodon nevadensis amargosae subspecies, and (2) Big Spring—a comparatively stable springhead and outflow inhabited by Cyprinodon nevadensis mionectes. These particular populations have been isolated from each other for only 400–4000 years. In both populations AVT-immunoreactive somata localized to parvocellular and magnocellular neurons in the preoptic area, with AVT-immunoreactive fibers extending ventrolaterally to innervate the pituitary. We found that both parvocellular and magnocellular AVT-immunoreactive neurons were significantly larger in males and females from the Amargosa River population than in same sex pupfish from Big Spring. Our findings suggest that the divergent ecological conditions of these two habitats have brought about changes in AVT pathways in the brain.

Arsenic drinking water exposure and urinary excretion among adults in the Yaqui Valley, Sonora, Mexico

The objective of this study was to determine arsenic exposure via drinking water and to characterize urinary arsenic excretion among adults in the Yaqui Valley, Sonora, Mexico. A cross-sectional study was conducted from July 2001 to May 2002. Study subjects were from the Yaqui Valley, Sonora, Mexico, residents of four towns with different arsenic concentrations in their drinking water. Arsenic exposure was estimated through water intake over 24 h. Arsenic excretion was assessed in the first morning void urine. Total arsenic concentrations and their species arsenate (As V), arsenite (As III), monomethyl arsenic (MMA), and dimethyl arsenic (DMA) were determined by HPLC/ICP-MS. The town of Esperanza with the highest arsenic concentration in water had the highest daily mean intake of arsenic through drinking water, the mean value was 65.5 μg/day. Positive correlation between total arsenic intake by drinking water/day and the total arsenic concentration in urine ( r=0.50, P<0.001) was found. Arsenic excreted in urine ranged from 18.9 to 93.8 μg/L. The people from Esperanza had the highest geometric mean value of arsenic in urine, 65.1 μg/L, and it was statistically significantly different from those of the other towns ( P<0.005). DMA was the major arsenic species in urine (47.7–67.1%), followed by inorganic arsenic (16.4–25.4%), and MMA (7.5–15%). In comparison with other reports the DMA and MMA distribution was low, 47.7–55.6% and 7.5–9.7%, respectively, in the urine from the Yaqui Valley population (except the town of Cocorit). The difference in the proportion of urinary arsenic metabolites in those towns may be due to genetic polymorphisms in the As methylating enzymes of these populations.

POPULATION DIFFERENCES IN SENSITIVITY TO UV-B RADIATION FOR LARVAL LONG-TOED SALAMANDERS

Ultraviolet-B radiation (UV-B; 280–320 nm) penetrates some aquatic habitats to biologically significant depths and can alter life histories of aquatic organisms, including algae, zooplankton, fish, and amphibians. Although major species differences have been documented for UV-B sensitivity, few studies have examined differences between populations of the same species. Previous work has suggested the hypothesis that larval long-toed salamanders (Ambystoma macrodactylum) from valley populations (∼100 m elevation) were more sensitive to UV-B exposure than larvae from mountain populations (above 500 m elevation). To test this hypothesis in the absence of possible other confounding environmental effects, we brought early-stage embryos into the laboratory from three valley populations and five mountain populations from Oregon and Washington and raised them under identical conditions without UV-B for two months after hatching. Larvae from each population were then placed under UV-B lighting, and we recorded thei...

Population Differences in Sensitivity to UV-B Radiation for Larval Long-Toed Salamanders

Ultraviolet-B radiation (UV-B; 280–320 nm) penetrates some aquatic habitats to biologically significant depths and can alter life histories of aquatic organisms, including algae, zooplankton, fish, and amphibians. Although major species differences have been documented for UV-B sensitivity, few studies have examined differences between populations of the same species. Previous work has suggested the hypothesis that larval long-toed salamanders (Ambystoma macrodactylum) from valley populations (∼100 m elevation) were more sensitive to UV-B exposure than larvae from mountain populations (above 500 m elevation). To test this hypothesis in the absence of possible other confounding environmental effects, we brought early-stage embryos into the laboratory from three valley populations and five mountain populations from Oregon and Washington and raised them under identical conditions without UV-B for two months after hatching. Larvae from each population were then placed under UV-B lighting, and we recorded their growth and survivorship for three weeks. Larvae from all populations had higher mortality when exposed to UV-B than when shielded from UV-B. However, individuals from low-elevation populations exposed to UV-B had significantly lower survivorship than did those from high-elevation populations, suggesting an elevational difference in UV-B sensitivity. In all populations, individuals exposed to UV-B were smaller than shielded individuals after one week. If UV-B is a factor in determining the long-term persistence of some amphibian species, an understanding of within-species variation is critical.

Population genetic structure and the conservation of isolated populations of Acacia raddiana in the Negev Desert

There is much concern over the high mortality of many populations of Acacia raddiana, a keystone tree species in the Negev desert of Israel. We used random amplified polymorphic DNA (RAPD) to assess patterns of genetic variation within and among 12 populations of A. raddiana from the Arava (Syrian–African Rift) valley and western Negev. A high level of genetic polymorphism was recorded within populations. An analysis of molecular variance (AMOVA) showed that about 59.4% of total genetic variance occurred among populations, which is considerably greater population differentiation than that recorded for other outbreeding species. Cluster and principal coordinates analyses and AMOVA indicate that the western Negev and Arava valley populations are highly differentiated. We suggest that there may have been two invasions of A. raddiana into Israel: one across the northern Sinai/Gaza Strip area into the western Negev, with some plants reaching the Dead Sea and a second invasion across the southern part of the Sinai peninsula, or even from Saudi Arabia, up to the Arava valley. From the conservation point of view, each population should be conserved separately because they are genetically highly differentiated and loss of any one population would lead to a dramatic loss of genetic variation. The mixing of genetically distinct populations may give rise to outbreeding depression (particularly because of GXE interactions). An obvious first step to the maintenance of this species' genetic diversity is the separate management of the western Negev and Arava valley populations because of their different evolutionary histories.

Overgrazing effects on vegetation cover and properties of volcanic ash soil in the páramo of Llangahua and La Esperanza (Tungurahua, Ecuador)

Abstract. The páramo is a high‐altitude ecosystem of the northern Andes. The vegetation is continuous, with grasses as the dominant groundcover. Because of their high water retention, páramos play a fundamental role in water availability for all the population of the inter‐Andean valleys. There are many studies of this specific ecosystem, but very few are focussed on overgrazing and its effect on vegetation and soil properties. Intensive grazing started less than 20 years ago and was studied in a representative area in the western Cordillera of central Ecuador covered by recent volcanic ash deposits. Intensive sheep grazing has led to a strong decline in the number of plant species, the replacement of the tussock grass vegetation by a short carpet grass vegetation, and an increase of bare land. In that area, the upper 50 cm of Andisols are deeply affected by a convergent decrease of Al and Fe oxalate and pyrophosphate in soil extracts, carbon contents decrease from 100 g kg–1 to less than 50 g kg–1 in the humid zone, from 70 to 40 g kg–1 in the dry zone and a reduction of water‐retention capacity at −33 kPa matrix potential from 800 g kg–1 to 200 g kg–1 in humid zones, from 350 to less than 100 g kg–1 in drier areas. They showed also a decrease in the macrostructure and the development of a highly water repellent microstructure. All these important transformations favour the development of aeolian erosion in dry areas, runoff on bare surfaces, and gully erosion on slopes. The role of the páramo in water‐regulation of this ecosystem seems to have been adversely affected for the future.

Prediction of plant species distribution in lowland river valleys in Belgium: Modelling species response to site conditions

In ecological modelling, limitations in data and their applicability for predictive modelling are more rule than exception. Often modelling has to be performed on sub-optimal data, as explicit and controlled collection of (more) appropriate data would not be feasible. An example of predictive ecological modelling is given with application of generalized additive and generalized linear models fitted to presence–absence records of plant species and site condition data from four nutrient-poor Flemish lowland valleys. Standard regression procedures are used for modelling, although explanatory and response data do not meet all the assumptions implicit in these procedures. Data were non-randomly collected and are spatially autocorrelated; model residuals retain part of that correlation. The scale of most site-condition records does not match the scale of the response variable (species distribution). Hence, interpolated and up-scaled explanatory variables are used. Data are aggregated from distinct phytogeographical regions to allow for generalized models, applicable to a wider population of river valleys in the same region. Nevertheless, ecologically sound models are obtained, which predict well the distribution of most plant species for the Flemish river valleys considered.

Rapid estimation of broad sense heritability of farmer-managed maize populations in the Central Valleys of Oaxaca, Mexico, and implications for improvement

A method for rapid estimation of broad senseheritability (H) was applied in farmers' maize fields in two communities inOaxaca, Mexico. Plant and ear traits were documented and H estimatescompared with narrow sense heritability (h2) from family analysis andpublished estimates. Absolute values of H estimates were larger thanh2 estimates from this study and the literature. Relative ranking bytrait was the same as in the literature, though not the same as rankings ofh2 estimates generated in this study. With an understanding of itslimitations, this rapid, economical estimation procedure could provideuseful initial information especially for collaborative crop improvement workbetween researchers and farmers or farming communities on-farm, a plantbreeding context for which little empirical information is available.

Evolution of dentition in prehistoric Ohio Valley Native Americans III. Metrics of deciduous dentition

Deciduous tooth size in Native Americans of the Ohio Valley area is fairly stable from the terminal Late Archaic (3200 BP) through the Late Prehistoric (350 BP) periods. Some fluctuation in average size did occur during this time. These fluctuations most likely reflect random changes due to gene drift. However, no difference in the pattern of interactions among the sizes of teeth (covariance structures) can be demonstrated during this period. Principal components analysis of the buccolingual and mesiodistal dimensions in the total sample indicate that the major axis of deciduous tooth size in the Ohio Valley population shows an allometric relationship, with the dimensions of the anterior teeth increasing (or decreasing) as the 1.33 power of the dimension of m1(1) and as the 2.0 power of the dimension of m2(2). Comparison of the Ohio Valley samples with other samples from the Eastern Woodlands suggests that geography may have played a minor role in structuring deciduous tooth size variation. For the most part, however, widely separated Eastern Woodlands populations appear to have been evolving independently with respect to deciduous tooth size.

Atmospheric dispersion modeling for assessment of exposure to arsenic for epidemiological studies in the Nitra Valley, Slovakia

The short‐range atmospheric dispersion model UK‐ADMS has been applied to calculate ground‐level concentrations of arsenic within 20 km of the Nováky Power Plant, Nitra Valley, Slovakia, as a function of distance and direction from source and year of operation, for application to an assessment of local population exposure to arsenic, and hence to two epidemiological studies of the effect of arsenic exposure on skin, lung, and bladder cancer in an east European population. A simple approach, where the effect of complex terrain is included by using local observations for meteorological input to the model, is sufficient for initial screening to compare atmospheric dispersion with other exposure pathways. This shows that isopleths of ground‐level annual average arsenic concentration in air (excluding periods when there is no wind) are elongated aligned with the axis of the valley. The maxima of concentration occur about 2 km to the northeast and southwest of the source, and a factor of 30 reduction in concentration is found from there to a distance 10 km away. The value of this information for epidemiological studies is discussed. If atmospheric concentration is found to be an important determinant of arsenic exposure for the Nitra Valley population, it will be necessary to carry out further investigation of the dispersion of the plume in complex terrain when there is no wind in the valley, which is the case in 13% of the observations and is estimated could contribute more than 50% of the annual average arsenic concentration close to the source.

Physiological ecology of Mediterranean Blue Tits (Parus caeruleus) I. A test for inter-population differences in resting metabolic rate and thermal conductance as a response to hot climates

Blue Tits (Parus caeruleus) are widely distributed throughout Europe, reaching the southern limit of their range on islands in the Mediterranean and in northern Africa. On Corsica, one population located at Pirio in the Fango Valley breeds roughly one month later than populations in adjacent valleys or on the continent, thus exposing nestlings to high ambient temperatures (T(a)). We tested the hypothesis that nestlings and possibly adult Blue Tits at Pirio would exhibit a reduction in resting metabolic rate (MR) and an increase in thermal conductance as a physiological response to high T(a). We compared the thermoregulatory response and evaporative water loss for nestlings from Pirio in Corsica and one continental site (Vic-le-Fesq) and for adults from two Corsican (Pirio and Muro) and one continental site (La Rouvière). At 12-14 days of age, nestlings from Pirio showed two distinct thermoregulatory patterns. Nestlings under 8.0 g behaved as heterotherms, whereby MR was correlated only with body temperature. At body masses above 8.0 g nestlings progressively acquired the ability to regulate T(b) and at masses >9.0 g they behaved as homeotherms. When considering homeothermic nestlings and adults, population of origin did not affect either thermal conductance or resting MR. For homeothermic nestlings, mass-specific resting MR (mW x g-(1)) was 15.5 +/- 2.6 and 17.5 +/- 2.5 for nestlings from Vic-le-Fesq and Pirio, respectively. For adults, mass-specific resting MR (mW x g-(1)) was 17.5 +/- 2.0, 17.8 +/- 1.6, and 17.9 +/- 1.0 for birds from Pirio, Muro, and La Rouvière, respectively. Although there was a weak but positive effect of T(a) on evaporative water loss for homeothermic nestlings, no such trend was evident for adults over the range of T(a) tested in this study. We thus find no evidence to indicate that either nestlings or adults exhibit the exponential increase in evaporative water loss associated with the non-convective regulation of T(b) within the range of T(a) tested (roughly <or=35 degrees C). We conclude that there is no evidence for a specific physiological adaptation in the Pirio population. Measures of nestbox temperatures indicate that nestlings rarely experience temperatures in excess of 33 degrees C. We conclude that, although some years may be hot enough to impose a thermal stress, temperatures at Pirio are not high enough to consistently impose a selective pressure for physiological adaptations to heat.

Tentative de discrimination des femelles adultes de simulies (Diptera : Simuliidae) à Nuku-Hiva (Archipel des Marquises, Polynésie Française )

Simulium sechani Craig & Fossati, 1995 was recently found for the first time in a part of Nuku-Hiva Island. This species coexists with Simulim buissoni Roubaud 1906, the dominant species, and always regarded as the main biting fly on the island. The problem is that optimisation of control operations needs a good knowledge of targets. The unknown female of S. sechani is the reason of this study. This study used samples collected before the description of S. sechani to try to correlate its geographical extent with easy to use biometrical parameters, and then give a first look at the possibilities of determination of adult females. Parameters used are: the numbers of maxillary and mandibular teeth, the dimension of the third antenna article and the number of apical hairs, the width and depth of the ventral plate space, and the number of hairs on the radial vein of the wing. Analysis of frequency distributions in relation with sampling sites and trapping hosts did not allow us to find convenient diagnosis characters, but contributed to new questions about isolation of insect populations in valleys and hosts usually used.

Incidence of ryegrass endophyte (Neotyphodium lolii) and diversity of associated alkaloid concentrations among naturalised populations of perennial ryegrass (Lolium perenne L.)

The mutualistic association between perennial ryegrass (Lolium perenne L.) and the ryegrass endophyte Neotyphodium lolii (Latch, Christensen and Samuels) Glenn, Bacon and Hanlin, previously assigned to the genus Acremonium, is known to have a major impact on pasture and animal production. The perennial ryegrass ecotypes Victorian and Kangaroo Valley are the most widely sown varieties of grass in Australian pasture. The incidence of ryegrass endophyte (N. lolii) in these ecotypes, and the production of alkaloids associated with theryegrass endophyte, are largely unexplored. Fifty-six populations of Victorian and 45 of Kangaroo Valley were sampled from old pasture within the recognised zones of naturalisation of both ecotypes. All of the 101 populations examined were infected with ryegrass endophyte. The mean ryegrass endophyte (N. lolii) frequency for plants within the populations of the Victorian and Kangaroo Valley ecotypes was 88% and 93%, respectively. Alkaloid concentrations were determined from infected plants for 39 Kangaroo Valley populations and, in a separate study, for 24 Victorian populations. Ergovaline concentration was above the critical level of 0.4 mg/kg (above which clinical symptoms are observed) for 10% of the Kangaroo Valley populations and 17% of the Victorian populations. For lolitrem B, all Victorian populations were below the critical level of 1.8 mg/kg, but 28% of the Kangaroo Valley populations had mean concentrations above the critical level, 1.8 mg/kg. Concentrations for individual plants were &lt;5 mg/kg for ergovaline, &lt;6 mg/kg for lolitrem B, and &lt;48 mg/kg for peramine. Within each ecotype examined, significant variation (P &lt; 0.05) in the mean concentrations of ergovaline, lolitrem B, and peramine was found between the populations of naturalised perennial ryegrass. Mean concentrations for some of the various naturalised populations were higher than that observed in some of the control cultivars. Low ergovaline and lolitrem B concentrations observed for individual genotypes indicate scope for selecting grass endophyte combinations characterised by optimum production of alkaloids.