Altitudinal Limit Research Articles

Predictable convergence in hemoglobin function has unpredictable molecular underpinnings.

To investigate the predictability of genetic adaptation, we examined the molecular basis of convergence in hemoglobin function in comparisons involving 56 avian taxa that have contrasting altitudinal range limits. Convergent increases in hemoglobin-oxygen affinity were pervasive among high-altitude taxa, but few such changes were attributable to parallel amino acid substitutions at key residues. Thus, predictable changes in biochemical phenotype do not have a predictable molecular basis. Experiments involving resurrected ancestral proteins revealed that historical substitutions have context-dependent effects, indicating that possible adaptive solutions are contingent on prior history. Mutations that produce an adaptive change in one species may represent precluded possibilities in other species because of differences in genetic background.

Effective gene flow in a historically fragmented area at the southern edge of silver fir (Abies alba Mill.) distribution

Fragmented populations at the edges of a species’ distribution can be highly exposed to the loss of genetic variation, unless sufficient gene flow maintains their genetic connectivity. Gene movements leading to successful establishment of external gametes (i.e. effective gene flow) into fragmented populations can solely be assessed by investigating the origin of natural regeneration. This study is focused on studying gene flow patterns in two silver fir stands in Central Apennines, where the species has a highly fragmented distribution. By using nuclear and chloroplast microsatellite markers, we investigated genetic variation, fine-scale spatial genetic structure, effective gene flow rates and large-scale connectivity characterizing both stands. Similar levels of genetic variation and low genetic differentiation between stands (F ST = 0.005) and across generations were found, coupled with low inbreeding and weak to absent SGS in the adult cohort (Sp < 0.003). On the other hand, substantial differences between the two stands in terms of gene flow rates were observed. Irrespective of the parentage approach used, higher gene flow rates were found in the stand located at the upper silver fir altitudinal limit, especially for seed-mediated gene flow (0.79 in the upper stand vs. 0.48 in the lower stand). Conversely, the lower stand was characterized by a higher reproductive dominance of local adults. Our findings suggest that, despite similar levels of genetic variation and generally high gene flow rates, different processes may be acting on the two stands, reflecting varying ecological conditions.

Contrasting Population Dynamics in the Boreo-AlpineSilene acaulis(Caryophyllaceae) at Its Southern Distribution Limit

Classical theory predicts a high demographic vulnerability and diminished performance of peripheral plant populations, but recent studies highlight the fact that environmental factors may override that geographical pattern. In this study, we compare the density, population structure and population dynamics of the boreo-alpine Silene acaulis (Caryophyllaceae) in two locations at its southern European distribution limit, using matrix projection models. One population was close to the species' lower altitudinal limit, and thus exposed to more ecologically marginal conditions (higher intraspecific competition and temperature) than the population higher up. The low-altitude population was sparser and its members were older as a result of lower recruitment and survival of new individuals. Additionally, this population's growth rate was lower, mainly due to a shorter permanence of large plants. The contrasting demographic differences between two closely located, southern peripheral populations highlight the impo...

Plant maintenance and environmental stress. Summarising the effects of contrasting elevation, soil, and latitude on Quercus ilex respiration rates

Determining the increase in maintenance respiration in response to stress is critical for understanding the cost of adaptation, in terms of expenditure of assimilated carbon. Here, we ask how maintenance costs vary for populations native to contrasting habitats and whether maintenance cost remains constitutive or induced in response to stress. Two populations of Quercus ilex were selected in southern Iberian Peninsula, one growing close to the altitudinal limit and the other growing at mean elevations for the species. Maintenance respiration, growth, and structural variables were measured in leaves and fine roots. We modelled the results found here and those published for populations native to stressed (both soil and latitudinal) habitats. The maintenance respiration measured at 20 °C was higher in expanding (90 %) and in mature (35 %) leaves and in roots (78 %) of individuals growing at higher elevations. Furthermore, our meta-analysis supports that the cost of organ maintenance is higher in stressed habitats, irrespective of the stress factor. As regards the whole plant metabolic design, Q. ilex seems to combine high phenotypic plasticity according to current growth conditions, and high adaptive capacity for local differentiation in response to average stress conditions in the provenance habitat.

Review of Gobi bear research (Ursus arctos gobiensis, Sokolov and Orlov, 1992)

Gobi bear (Ursus arctos gobiensis, Sokolov, Orlov, 1992) is endangered and occurs only in isolated populations in the Southwestern part of Mongolia. It is listed in the Red book of Mongolia (1987, 1997, 2013) and is registered in Annex I of the Convention on international trade in endangered species (CITES, 1991). Hunting for the Gobi bear is prohibited by law in 1953, nowadays it is protected in the Great Gobi reserve. The article provides generalized information about habitat, behavior, diet, and mortality of Gobi bear. The research also touched upon the peculiarities of its historical distribution in Gobi (and the subsequent loss of habitat), movement, size, and taxonomic status. Previous analysis of mitochondrial DNA (Galbreath et al., 2007; McCarthy et al., 2009) showed that Gobi bear is similar to the subspecies Ursus arctos Preliminary analysis based on nuclear microsatellite markers indicates that Gobi bear is actually can be a separate subspecies of Ursus arctos gobiensis (Tumendemberel et al., 2015а). The analysis of 2835 places of encounters of five bears using GPS for the period from 2005 to 2009 has allowed estimating that within the Great Gobi reserve for the habitat of the Gobi bear suitable territory is about 23619.18 km2. The current habitat is likely reduced by 60% from historical range. Based on the telemetry data and the results of genetic analyses, the current distribution of bears in the Gobi desert was estimated. Adult females have moved around an area of about 514 km2 within 1009–1532 m above sea level around Shar Khuls oasis. Adult males moved through the area about 2465–2485 km2; altitudinal limits of 1122–1492 m. International Team Project on Gobi bear, together with researchers from the Gobi bear Fund, Institute of General and Experimental biology, Mongolian Academy of Sciences and the administration of the Great Gobi reserve in 2005 have used camera traps to estimate population size of Gobi bear. It is established that on the reserve territory at least 18 bears were including 7 males, 4 females, and 2 calves (Amgalan et al., 2005). Using genetic analyses (DNA microsatellites) from more than 1000 hair samples taken near 14 springs, it was calculated that during 2008–2009, these springs were visited by 22–31 individuals of Gobi bear, of which at least 14 males and 8 females (Tumendemberel et al., 2015).

Výškové maximá a pozoruhodnejšie vertikálne výskyty cievnatých rastlín z oblasti Demänovskej doliny v Nízkych Tatrách

Výškové maximá a pozoruhodnejšie vertikálne výskyty cievnatých rastlín z oblasti Demänovskej doliny v Nízkych Tatrách

A comparison between different treeline types shows contrasting responses to climate fluctuations

Treeline position is mainly determined by growth season temperature, but the response of treelines to climate warming is not uniform worldwide. We compared treeline structure, dynamics and thermal profile in nearby areas with different treeline type, species composition and bioclimatic conditions. We performed a detailed survey of different treeline types in three areas of Italian Alps and northern Apennines. Every tree individual was recorded along altitudinal transects from the closed forest to the species limit. Treeline structure and dynamics were described through altitudinal limits of tree height, density and age. Data were elaborated by principal components analysis. Temperature regime of the three sites was assessed from homogeneous historical climatic data. Treeline was different in the three areas for species composition, shape and dynamics. Both Alpine sites showed diffuse treeline, but only one showed advancing dynamics. Apennine treeline was abrupt and static, with higher temperature at the tree limit. Our study showed the variable dynamics of treelines within a relatively restricted area and the connection between treeline shape and dynamics. An important role is played by species composition, determined by bioclimatic and historical features. These factors should be taken into account when modelling future treeline dynamics at global scale.

Phenology and species determine growing-season albedo increase at the altitudinal limit of shrub growth in the sub-Arctic.

Arctic warming is resulting in reduced snow cover and increased shrub growth, both of which have been associated with altered land surface-atmospheric feedback processes involving sensible heat flux, ground heat flux and biogeochemical cycling. Using field measurements, we show that two common Arctic shrub species (Betula glandulosa and Salix pulchra), which are largely responsible for shrub encroachment in tundra, differed markedly in albedo and that albedo of both species increased as growing season progressed when measured at their altitudinal limit. A moveable apparatus was used to repeatedly measure albedo at six precise spots during the summer of 2012, and resampled in 2013. Contrary to the generally accepted view of shrub-covered areas having low albedo in tundra, full-canopy prostrate B. glandulosa had almost the highest albedo of all surfaces measured during the peak of the growing season. The higher midsummer albedo is also evident in localized MODIS albedo aggregated from 2000 to 2013, which displays a similar increase in growing-season albedo. Using our field measurements, we show the ensemble summer increase in tundra albedo counteracts the generalized effect of earlier spring snow melt on surface energy balance by approximately 40%. This summer increase in albedo, when viewed in absolute values, is as large as the difference between the forest and tundra transition. These results indicate that near future (<50years) changes in growing-season albedo related to Arctic vegetation change are unlikely to be particularly large and might constitute a negative feedback to climate warming in certain circumstances. Future efforts to calculate energy budgets and a sensible heating feedback in the Arctic will require more detailed information about the relative abundance of different ground cover types, particularly shrub species and their respective growth forms and phenology.

Some Characteristics of Permafrost and Its Distribution in the Gaize Area on the Qinghai—Tibet Plateau, China

ABSTRACTAn investigation of permafrost in the Gaize area in the west Qinghai—Tibet Plateau in China was conducted in October and November of 2010 and 2011. It was found that mean annual ground temperature was >−1 °C with a permafrost thickness of <60 m in the widespread alpine steppe below an altitude of 5400 m a.s.l. The active layer thickness was usually deeper than 3 m with a maximum of about 5.7 m. Overall, the ice/water content of the top 15 m of frozen soil was usually <10%. The altitudinal limit of permafrost in the alpine steppe was about 5100, 5000, and 4950 m a.s.l. on south-, east-west-, and north-facing slopes, respectively. A permafrost map was constructed using the ARCGIS platform and topographic information from the TOPO 30 digital elevation model. Statistical analysis of the map revealed that permafrost is primarily distributed in the hilly/mountainous areas of Gaize, covering 51% of the study area. The area of permafrost in this map is considerably less than in the Permafrost Map of the Qinghai—Tibet Plateau drawn in 1996. Further analysis revealed that the large difference between the two maps could be attributed to both errors in the earlier mapping method and permafrost degradation.

Estimating Permafrost Distribution in the Maritime Southern Alps, New Zealand, Based on Climatic Conditions at Rock Glacier Sites

Alpine permafrost occurrence in maritime climates has received little attention, despite suggestions that permafrost may occur at lower elevations than in continental climates. To assess the spatial and altitudinal limits of permafrost in the maritime Southern Alps, we developed and tested a catchment-scale distributed permafrost estimate. We used logistic regression to identify the relationship between permafrost presence at 280 active and relict rock glacier sites and the independent variables a) mean annual air temperature and b) potential incoming solar radiation in snow free months. The statistical relationships were subsequently employed to calculate the spatially-distributed probability of permafrost occurrence, using a probability of ≥ 0.6 to delineate the potential permafrost extent. Our results suggest that topoclimatic conditions are favorable for permafrost occurrence in debris-mantled slopes above ~ 2000 m in the central Southern Alps and above ~ 2150 m in the more northern Kaikoura ranges. Considering the well-recognized latitudinal influence on global permafrost occurrences, these altitudinal limits are lower than the limits observed in other mountain regions. We argue that the Southern Alps’ lower distribution limits may exemplify an oceanic influence on global permafrost distribution. Reduced ice-loss due to moderate maritime summer temperature extremes may facilitate the existence of permafrost at lower altitudes than in continental regions at similar latitude. Empirical permafrost distribution models derived in continental climates may consequently be of limited applicability in maritime settings.

The cultural context of biological adaptation to high elevation Tibet

Permanent, year-round occupation of high elevation, low oxygen environments is next to impossible for human populations adapted to low elevation, high oxygen environments. Sustained human habitation of high elevation environments is therefore a comparatively late development in global human history. Though we are beginning to understand the biological differences between contemporary highland and lowland populations, we do not understand how, or when, these differences evolved. This paper presents a hypothesis for the historical context of human adaptation to the Tibetan Plateau. Archaeological data suggest that Neolithic agricultural groups living on the northeast margins of the Plateau expanded to the altitudinal limits of their farming systems by 5200cal BP, but also to the limits of human physiological capacity for high elevation (at ~2500m above sea level). With the introduction of novel, exotic domesticates (namely barley, wheat, and sheep), Neolithic agriculturalists started to push these limits, and in roughly 1600years (by 3600cal BP) small groups of people were living at higher elevations and deeper into the Tibetan Plateau. This required and encouraged novel cultural solutions to high elevation settings, but also imposed heavy selective pressure on the physiological capacity for low oxygen environments. These new cultural capacities enabled people to move into a stronger environment of selection (above 2500m above sea level) that favored the physiological capacities for life at high elevation, which in turn became more common across these populations. This hypothesis about bio-cultural evolution is testable with a combination of high-resolution archaeological evidence and high throughput sequencing of datable prehistoric human DNA.

The floristic changes of Scottish moorland dominated by heather (Calluna vulgaris, Ericaceae) but unburnt for 50 years and kept checked by moderate grazing

Vegetation and herbivore usage have been monitored since 1969/1970 at four moorland sites where heather (Calluna vulgaris) remained the main species under moderate levels of grazing. Much of the annual growth of the heather was regularly consumed by this grazing, but no burning occurred to remove heather biomass. Two sites were on acidic base-poor soils and had only minor cover of grasses and herbs, their vegetation having most affinity to H10 heath in the National Vegetation Classification of British plant communities. The other two sites were on more base-rich soils, and grasses and herbs had substantial cover; their vegetation showed most affinity to NVC CG11a grassland. One of the latter sites lies at 700 m and Calluna grew poorly being close to its altitudinal limit; the other three sites were at lower altitude and Calluna grew strongly creating dense swards. Over the 43–44 years of observation Calluna increased moderately in height but many subordinate higher plants declined in cover, as measured by...

The altitudinal limit of Leptohyphes Eaton, 1882 and Lachlania Hagen, 1868 (Ephemeroptera: Leptohyphidae, Oligoneuriidae) in Ecuadorian Andes streams: searching for mechanisms

ABSTRACTWe explored mechanisms determining the upper altitudinal limit of ephemeropterans from two different genera: Leptohyphes Eaton, 1882 (Leptohyphidae) and Lachlania Hagen, 1868 (Oligoneuriidae). For this, we (1) surveyed the two taxa in 165 stream sites along a wide altitudinal gradient; (2) sampled benthic fauna at short altitudinal intervals along a stream, from 2780 to 3150 m above sea level; (3) collected adults at the lowest and highest sites; and (4) transplanted nymphs from the lowest to the highest study site in our stream to determine survival over time. Densities of the two taxa declined gradually with altitude and both disappeared between 2950 and 3080 m a.s.l. The upper altitudinal limit in the stream seemed to be most closely related to mean oxygen saturation, temperature, and current velocity. Adults were collected where the nymphs were found, but not at the upstream site where the nymphs were absent, implying limited upstream dispersal of adults and some of the altitudinal constraint lying at the adult stage. Short-term survival of transplanted nymphs was lower than that of controls, suggesting that the distribution was limited at the juvenile stage, and that at least some of the altitudinal constraint is related to the abiotic stream environment.

Intensification of Southern Hemisphere westerly winds 2000–1000 years ago: evidence from the subantarctic Campbell and Auckland Islands (52–50°S)

ABSTRACTThe Southern Ocean plays a significant role in driving global climate–ocean–carbon dynamics. Unfortunately, a relative dearth of datasets across the region limits our ability to understand past and future mechanisms of change. Here we report a new dataset from the south‐west Pacific: radiocarbon‐dated subfossil tree stumps (Dracophyllum) eroding out from peat exposures on Campbell and Auckland Islands (52–50°S). Dracophyllum are the southernmost growing trees in the south‐west Pacific and their growth on exposed sites and at altitude is strongly controlled by the prevailing westerly airflow, providing a unique measure of past changes in zonal wind strength. Here we demonstrate a significant collapse in the altitudinal limit of growth between approximately 2000 and 1000 years ago (hereafter 2–1 ka), consistent with other records across the Southern Hemisphere that indicate westerly airflow was significantly enhanced. Importantly, this period in the late Holocene was one of marked change across the broader region, suggesting westerly airflow played a key role in driving Southern Ocean variability at this time.

On the Occurrence of Natural Norway Spruce Woodland in the Pieniny Mts (Western Carpathians)

Abstract According to Kulczyński (1928), a natural Picea abies forest occurs in the mountain range of the Pieniny Mts on the slopes of the mountain Vysoke skalky. Later, various data on the altitudinal range of this stand (and thus on the locality itself) were published: (1) 890 (900) - 950 m, (2) 1000 - 1050 m or (3) around 1000 m. The aim of the field research was to verify published data on the occurrence of a woodland of Upper Mountain Norway spruce (association Polysticho-Piceetum) in the territory of Vysoke skalky. A field study in the area has revealed that most of published data on the occurrence of the Kulczyński’s Picea woodland are incorrect, as its real upper altitudinal limit reaches ± 940 m. The main result is the confirmation of the real existence of a Vaccinium myrtillus-Homogyne alpina-Picea abies phytocoenosis in the territory of Vysoke skalky. However, tree species other than Picea abies (e.g. Fagus sylvatica, Abies alba, Acer pseudoplatanus) could persist in the special habitat of Kulczyński’s ‘Picea woodland’. The natural vegetation of this place was formed by mixed forest stand.

Climatic marginality: a new metric for the susceptibility of tree species to warming exemplified by Fagus sylvatica (L.) and Ellenberg’s quotient

In the face of climate warming, maps of potential tree species distribution can support forest management planning at coarse scales. For evaluating future suitability, conditions at the rear edge, i.e. at the meridional and lower altitudinal limits of species distribution, are of particular importance. Therefore, we present the concept of climatic marginality (distance to the rear edge) as a metric for the susceptibility against climate warming. Using a statistic niche model fitted to observed and potential beech occurrence in ICP Forests Level I monitoring plots and WorldClim data, we evaluate the modelled xeric limit of European beech based on the Ellenberg’s climate quotient involving thresholds suggested by Ellenberg and other authors. The applicability of the marginality index was tested with independent study sites. Despite the limitations of niche modelling, estimated climatic thresholds of beech were well in accordance with textbook knowledge and recent research. The regional patterns of climatic marginality were plausible and more meaningful with respect to the rear edge compared to conventional niche model outputs. In terms of climatic marginality, most regions in Central Europe are far from the xeric limit of beech. Evaluation based on independently sampled sites indicated that inclusion of soil and topography (microclimate) may permit implications at the local scale, e.g. growth potential estimations.

Pollen–climate reconstruction from northern South Island, New Zealand (41°S), reveals varying high‐ and low‐latitude teleconnections over the last 16 000 years

ABSTRACTWe present a 16 000‐year vegetation and climate reconstruction from pollen and plant macrofossil records obtained at a small alpine lake in South Island, New Zealand (41°S). The expansion of lowland forest taxa suggests a lifting of the altitudinal forest limits because of a warming pulse between 13 and 10k cal a BP and between 7 and 6k cal a BP, while their decline relative to upland forest taxa indicates cooling phases between 10 and 7k cal a BP and over the last 3000 years. The modern treeline was first established locally by 9.7k cal a BP. Forest persisted at the site until 3k cal a BP then disappeared from the record. Close correspondence between the temperature trends inferred from the pollen and macrofossil records and proxies from Antarctica and the Southern Ocean suggests a strong teleconnection between New Zealand and the Southern Hemisphere high‐latitudes between 15 and 6k cal a BP. We note that the breakdown of this coupling, a cooling trend in Adelaide Tarn and the local disappearance of beech forest after 3k cal a BP occur during a period of increased frequency of El Niño events, suggesting an enhanced teleconnection with the low‐latitudes during the late Holocene.

Large‐scale population genetics of the mountain ant Proformica longiseta (Hymenoptera: Formicidae)

AbstractProformica longiseta Collingwood is an endemic ant found in southeastern Spain that inhabits high mountains and is widespread within an altitude range. We have studied the population genetics and biogeography of 14 populations of P. longiseta throughout its distribution using microsatellites and mitochondrial data. Populations are strongly structured for both markers and show isolation by distance, which together with the absence of intra‐population variation in mitochondrial DNA suggest strong female philopatry and limited male dispersal. In spite of this, no recent bottlenecks or inbreeding were detected. Finally, we report on a population currently located where it did not exist 14 years ago, above the usual altitudinal limit known for the species, which may be due to recent colonization enhanced by global warming.

A plant microfossil record of Late Quaternary environments and human activity from Rano Aroi and surroundings, Easter Island

To investigate past vegetation change and human activity at the highest elevations on Easter Island, this study examines pollen, phytoliths, diatoms, starch and arthropods preserved in sediment/soil profiles from Rano Aroi crater, and another, newly described wetland in the adjacent, much smaller Rano Aroi Iti depression. A Bayesian age–depth model for Rano Aroi provides adequate certainty for the Late Pleistocene and last ~1000 years, but is poorly constrained from 12,000 to 1000 cal BP. The occurrence of cf. Potamogeton and Lycopodium pollen types at this highland site (~425 m altitude), while absent or rare at lowland sites, could well be related to the cooler higher altitude conditions. Smaller quantities of Arecaceae (palm) pollen than at lowland sites indicate that this relatively high-altitude part of the island was near the altitudinal forest limit in the Late Pleistocene, with extensive Asteraceae-dominated shrubland. Arecaceae forest dominated the Holocene, for which there is evidence for a prolonged dry phase. The subsequent disappearance of charcoal and reappearance of diatoms, particularly Eunotia cf. pectinalis, suggest that the dry phase ended prior to human settlement. Polynesian activity is best constrained by abundant microscopic charcoal fragments beginning in a layer at 710 (2σ: 645–797) cal BP, and suggesting a period of forest clearance and burning, culminating at 339 (2σ: 177–428) cal BP. Thinner soils compared with lowland horticultural sites and 14C dates of macroscopic Sophora charcoal suggest that the site was occupied after 1670 CE. Newly described terraces, and pollen, phytoliths and starch of cf. Broussonetia papyrifera (paper mulberry), cf. Colocasia esculenta (taro) and Musa (banana) sp. identified in this study show the value of a combined microfossil approach and provide evidence for extension of cultivation of these Polynesian-introduced cultigens to this least accessible part of the island. Rano Aroi Iti yielded a Bayesian 14C age–depth chronology to a basal age of 1530–1314 cal BP, giving an unexpectedly old age for presumably introduced New World pollen of Sisyrinchium, which occurs throughout the core.

Altitudinal distribution limits of aquatic macroinvertebrates: an experimental test in a tropical alpine stream

1. Temperature and oxygen are recognised as the main drivers of altitudinal limits of species distributions. However, the two factors are linked, and both decrease with altitude, why their effects are difficult to disentangle.2. This was experimentally addressed using aquatic macroinvertebrates; larvae of Andesiops (Ephemeroptera), Claudioperla, (Plecoptera), Scirtes (Coleoptera) and Anomalocosmoecus (Trichoptera), and the amphipod Hyalella in an Ecuadorian glacier‐fed stream (4100–4500 m a.s.l.). The following were performed: (i) quantitative benthic sampling at three sites to determine altitudinal patterns in population densities, (ii) transplants of the five taxa upstream of their natural altitudinal limit to test the short‐term (14 days) effect on survival, and (iii) in situ experiments of locomotory activity as a proxy for animal response to relatively small differences in temperature (5 °C vs. 10 °C) and oxygen saturation (55% vs. 62%).3. The transplant experiment reduced survival to a varying degree among taxa, but Claudioperla survived well at a site where it did not naturally occur. In the in situ experiment, Scirtes and Hyalella decreased their activity at lower oxygen saturation, whereas Andesiops and Anomalocosmoecus did so at a low temperature. The decrease in activity from a high to a low temperature and oxygen for the five taxa was significantly correlated with their mortality in the transplant experiment.4. Together the present experiments indicate that even relatively small differences in temperature and oxygen may produce effects explaining ecological patterns, and depending on the taxon, either water temperature or oxygen saturation, without clear interacting effects, are important drivers of altitudinal limits.