Low-altitude Populations Research Articles

Shorter telomeres precede population extinction in wild lizards

Identifying the early warning signals of catastrophic extinctions has recently become a central focus for ecologists, but species’ functional responses to environmental changes remain an untapped source for the sharpening of such warning signals. Telomere length (TL) analysis represents a promising molecular tool with which to raise the alarm regarding early population decline, since telomere attrition is associated with aging processes and accelerates after a recurrent exposure to environmental stressors. In the southern margin of their range, populations of the common lizard (Zootoca vivipara) recently became extinct at lowest elevations due to changes in climate conditions. However, the proximal signals involved in these demographic declines are still unknown. Here, we sampled 100 yearling lizards from 10 natural populations (n = 10 per population) along an extinction risk gradient. Relative lizard abundance dramatically dropped over 12 years in low-altitude populations characterized by warmer ambient temperatures and higher body growth of lizards early in life. A non-linear relationship was found between TL and population extinction risk, with shorter telomeres in populations facing high risk of extinction when compared to non-threatened ones. Our results identify TL as a promising biomarker and imply that population extinctions might be preceded by a loop of physiological aging.

Plasticity of thermoregulatory behaviour in response to the thermal environment by widespread and alpine reptile species

Phenotypic plasticity plays a central role in determining how organisms respond to environmental change over short timescales. Despite this, we know little about how phenotypic plasticity varies between populations or species. We tested the extent of plasticity in basking behaviour in low- and high-altitude populations of two widespread lowland and two highland species of a cool-climate lizard genus: Niveoscincus. We found evidence of divergence in basking behaviour between populations and species, with highland species and high-altitude populations of all species basking more than the widespread lowland species and low-altitude populations. Furthermore, we found differences in the extent of behavioural plasticity between species. Widespread lowland species altered their basking behaviour depending on basking opportunity whereas the highland species maintained high levels of basking independent of basking opportunity. These differences in basking behaviour were concordant with the differences in body temperature across all populations, species and treatments. Combined, this suggests that divergence in thermoregulatory behaviour and thermophysiology between populations and species may have been facilitated by adaptive behavioural plasticity within populations. We discuss this and the implications of our findings for the ability of these animals to cope with ongoing climate change.

Reproductive investment of Pinus pseudostrobus along an altitudinal gradient in Western Mexico: implications of climate change

Climate varies along altitudinal gradients and species performance may be affected in response to these variations. Climate change can modify these gradients and, at the lower limit of species distributions, individuals may become stressed and their general health and reproductive performance may decrease. Study and prediction of the effects of climate change on the distribution of species along these gradients is therefore necessary. Our model study species, Pinus pseudostrobus, is a widely distributed pine in Mexico, ranging from 1600 to 3200 masl in altitude. In order to explore changes in health condition and reproductive investment along an altitudinal gradient, ten reproductive trees were selected in each of four populations (at 2300, 2400, 2700 and 2900 masl). As a proxy of individual health, we conducted a rapid visual assessment for each tree, based on crown defoliation, dead branches and foliage discoloration. This stress condition index (SCI) ranges from zero to fifteen, and lower values indicate low stress and therefore better health conditions. We also evaluated reproductive (cone weight, number/weight of seeds) and progeny (germination/seedling growth) traits. In addition, the relationships between SCI and the reproductive/progeny traits were assessed. The lowest altitude population presented poor health, with higher values of SCI (mean ± SE = 6.3 ± 0.9) that reduced up to 4.8-fold in higher-altitude populations. Cone weight also differed among altitudes, with lighter cones in the lower population (mean ± SE = 38.2 ± 4.3 g), and 1.5-fold heavier cones found in the higher populations. In general, all of the reproductive/progeny traits differed among altitudes. The population of intermediate altitude (2700 masl) presented the highest values for all traits evaluated, indicating higher performance at this altitude. Finally, a negative relationship was found between stress condition and cone weight. Based on our results and climate change models and their predictions, an increase in physiological stress can be expected in individuals of low altitude populations. Furthermore, possible increases in pests and pathogens are likely to contribute to the decline of this population. It is therefore necessary to maintain efforts of stress condition assessment and population dynamics, as well as to permanently monitor the climate along altitudinal gradients.

Factors Related to Altitudinal Body Size Variation in the Earthworm-Eating Ground Beetle Carabus japonicus

To understand geographic body size variation in an insect species, various factors including habitat temperature, correlation between life history traits, and food availability must be examined. Carabus (Ohomopterus) japonicus is univoltine, feeds exclusively on earthworms during its larval stage, and shows a clinal body size variation along the habitat temperature gradient in northern Kyushu, Japan. Carabus japonicus occurs at both high and low altitudes; at high altitudes it coexists with a larger species, C. (O.) dehaanii. At low altitudes, C. japonicus shows larger body sizes. We sought to determine whether this increase in body size is only an adaptation to high habitat temperatures in the absence of C. dehaanii, and examined the life history of C. japonicus and seasonal trends in prey earthworms at six sites between altitudes of 30 and 980 m. While high-altitude populations used the entire warm season for reproduction and larval development, low-altitude populations showed shorter periods of reproductive activity and larval incidence coincided with seasonal trends in earthworm abundance. Thus, C. japonicus attained larger body sizes at lower altitudes without a notable extension of their juvenile period. At lower altitudes, earthworms grew faster and reached sizes, which may be too large for predation by small carabid larvae. Large females had higher fecundity, and laid larger eggs, from which larger first instar larvae hatch. The large body size of C. japonicus in warm habitats may thus be an adaptation not only for high fecundity, but also for producing large first instar larvae to more efficiently prey on large earthworms.

Global correlates of extinction risk in freshwater crayfish

AbstractGlobal trait‐based analyses can shed light on the factors predisposing species to high extinction risk, and can help bridge knowledge gaps in speciose and poorly known taxa. In this paper, I conduct the first global comparative study of crayfish extinction risk. I collated data on intrinsic (biology and ecology) and extrinsic (environment and threats) factors for 450 crayfish species assessed on the IUCN Red List. Phylogenetic multiple regression models were used to identify correlates of risk in all species; in centres of diversity (American cambarids and Australian parastacids); and among threat types (agriculture, water management, pollution). I assessed the relative ability of threat maps quantifying specific threats (e.g. river fragmentation, mercury deposition) or a generic threat (human population density) to predict crayfish extinction risk. I also quantified the effects of range size on extinction risk with variation partitioning and multiplicative bivariate regressions. Crayfish with small range size, small body size, habitat dependency on caves, and with ranges in areas of low precipitation, high altitude and high human population density were at higher risk of extinction. Correlates of risk varied between American cambarids and Australian parastacids, suggesting that centres of diversity shape patterns of extinction risk in crayfish. The explanatory power of models ranged between 31 and 65%, with low explanatory power for models based on threat types. Few specific threat measures were significantly related to extinction risk, suggesting that large‐scale threat mapping may not be informative for freshwater invertebrates. In the absence of population data for most freshwater invertebrates, trait‐based models are powerful and cost‐effective tools for understanding and mitigating drivers of extinction risk.

Pollen limitation, plasticity in floral traits, and mixed mating system in an alpine plant Pedicularis siphonantha (Orobanchaceae) from different altitudes

AbstractPlant mating systems rapidly respond to pollen limitation in changing environments. However, whether and how floral traits are involved in a mating system shift requires further investigation. A widely distributed and bumblebee‐pollinated lousewort, Pedicularis siphonantha D. Don was studied. We investigated pollination systems, reproductive success, and floral traits in four large populations growing from 3200 m to 4300 m. Pollinator activity in low altitude populations was lower and these populations had a decreased fruit set and seed number per capsule compared to populations at high altitudes. Supplemental hand pollination with outcross pollen significantly increased seed production per capsule for plants from high altitudes but not for those from lower altitudes. We also found that bumblebees visited more flowers within an inflorescence in a single foraging bout in high altitudes compared with low altitudes, which caused a high possibility of geitonogamous mating. These differences may be pollination‐dependent rather than inheritance‐based because hand pollination on bagged flowers did not cause a difference in seed production across populations. Compared to plants from low altitudes, high‐altitude plants had increased flower longevity, larger floral displays, higher pollen production per flower, and shorter corolla tubes, which were found to be well in accordance with changes in both pollination environment and mating system. Plasticity in floral traits might help plants to adjust their resource allocation strategies in response to their habitat, which might be linked with pollination environment. The variability among these populations might be beneficial for this widely distributed species to cope with environmental changes.

Population structure and spatial pattern of Quercus variabilis among different geographical areas, China.

Age structures and spatial distribution patterns of Quercus variabilis populations were analyzed across geographical gradients (latitude, longitude and altitude) by using the size-grading method and the ratio of variance to mean. The results showed as following: Over the horizontal gradient, the northern, middle, southern and western populations of Q. variabilis exhibited an inverse-J shape, but the eastern populations declined. The spatial patterns of adult individuals were all clumped except the northern populations which were randomly distributed. Juveniles were clumped in the northern, middle and western populations, but were randomly distributed in the southern and eastern populations. The aggregation intensity of juveniles across latitude decreased with the order as the central, northern and southern populations, but as the central, southern and northern populations for adult individuals. The aggregation intensity of both juveniles and adults across longitude followed a decreased order as the central, western and eastern populations. Along the altitudinal gra-dient, the inverse-J type occurred only in the low- and middle-altitude populations, but populations in the high altitude declined. The juveniles in populations among altitude gradient all were clumped, but the adults were all clumped except the low-altitude populations which were randomly distributed. The aggregation intensities of both juveniles and adults were higher in the middle than the other altitudinal populations. Compared with adults, juveniles generally had higher aggregation intensities across various geographical gradients. Our results revealed that the age structure and spatial distribution pattern of Q. variabilis were mainly determined by environment variation across geographical gradients and the species' biological property, which supported the central-marginal hypothesis.

Testing for local adaptation and evolutionary potential along altitudinal gradients in rainforest Drosophila: beyond laboratory estimates.

Predicting how species will respond to the rapid climatic changes predicted this century is an urgent task. Species distribution models (SDMs) use the current relationship between environmental variation and species' abundances to predict the effect of future environmental change on their distributions. However, two common assumptions of SDMs are likely to be violated in many cases: (i) that the relationship of environment with abundance or fitness is constant throughout a species' range and will remain so in future and (ii) that abiotic factors (e.g. temperature, humidity) determine species' distributions. We test these assumptions by relating field abundance of the rainforest fruit fly Drosophila birchii to ecological change across gradients that include its low and high altitudinal limits. We then test how such ecological variation affects the fitness of 35 D.birchii families transplanted in 591 cages to sites along two altitudinal gradients, to determine whether genetic variation in fitness responses could facilitate future adaptation to environmental change. Overall, field abundance was highest at cooler, high-altitude sites, and declined towards warmer, low-altitude sites. By contrast, cage fitness (productivity) increased towards warmer, lower-altitude sites, suggesting that biotic interactions (absent from cages) drive ecological limits at warmer margins. In addition, the relationship between environmental variation and abundance varied significantly among gradients, indicating divergence in ecological niche across the species' range. However, there was no evidence for local adaptation within gradients, despite greater productivity of high-altitude than low-altitude populations when families were reared under laboratory conditions. Families also responded similarly to transplantation along gradients, providing no evidence for fitness trade-offs that would favour local adaptation. These findings highlight the importance of (i) measuring genetic variation in key traits under ecologically relevant conditions, and (ii) considering the effect of biotic interactions when predicting species' responses to environmental change.

Circulatory mechanisms underlying adaptive increases in thermogenic capacity in high-altitude deer mice.

We examined the circulatory mechanisms underlying adaptive increases in thermogenic capacity in deer mice (Peromyscus maniculatus) native to the cold hypoxic environment at high altitudes. Deer mice from high- and low-altitude populations were born and raised in captivity to adulthood, and then acclimated to normoxia or hypobaric hypoxia (simulating hypoxia at ∼4300 m). Thermogenic capacity [maximal O2 consumption (V̇O2,max), during cold exposure] was measured in hypoxia, along with arterial O2 saturation (SaO2 ) and heart rate (fH). Hypoxia acclimation increased V̇O2,max by a greater magnitude in highlanders than in lowlanders. Highlanders also had higher SaO2 and extracted more O2 from the blood per heartbeat (O2 pulse=V̇O2,max/fH). Hypoxia acclimation increased fH, O2 pulse and capillary density in the left ventricle of the heart. Our results suggest that adaptive increases in thermogenic capacity involve integrated functional changes across the O2 cascade that augment O2 circulation and extraction from the blood.

Physiological and biochemical responses to elevated temperature in a threatened freshwater crayfish, Euastacus sulcatus (Decapoda: Parastacidae)

Projected elevations in environmental temperature are expected to have a detrimental effect on organisms with distributions that are already restricted to high-altitude refugia, especially where dispersal is compromised due to population isolation by unsuitable intervening habitats. The present study was carried out on such an organism, namely Euastacus sulcatus, to determine: (1) the temperature at which thermal stress occurs under laboratory conditions; and (2) whether thermal stress is already occurring naturally in contemporary field-acclimatised individuals. The laboratory data provided evidence that biochemical and physiological stress occurred in E. sulcatus at 22.5°C or higher. In the field, oxidative stress was characterised by an increase in the oxidised redox state of glutathione within a low-altitude population accompanied by significantly elevated protein carbonyls and lipid peroxidation. The data confirmed that potential thermal stress was present in E. sulcatus residing at the lower end of its altitudinal distribution, indicating that this threatened species is already challenged within localised populations in their natural environment. Together, these results reveal that future increases in environmental temperature are not only likely to result in increased baseline levels of stress in E. sulcatus, but also forecast further restriction in the altitudinal distribution of the species in a warming climate.

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...

Mitochondrial haplogroup M9a1a1c1b is associated with hypoxic adaptation in the Tibetans.

While hypoxic environment at high altitude remains a major challenge for travelers from low-altitude areas, Tibetans have adapted to the high-altitude environment. Mitochondria are the energy conversion and supplement centers in eukaryotic cells. In recent years, studies have found that the diversity of the mitochondrial genome may have a role in the adaptation to hypoxia in Tibetans. In this study, mitochondrial haplogroup classification and variant genotyping were performed in Tibetan and Han Chinese populations living at different altitudes. The frequencies of mitochondrial haplogroups B and M7 in the high-altitude population were significantly lower compared with those in the low-altitude population (P=0.003 and 0.029, respectively), whereas the frequencies of haplogroups G and M9a1a1c1b in the high-altitude group were significantly higher compared with those in the low-altitude group (P=0.01 and 0.002, respectively). The frequencies of T3394C and G7697A, which are the definition sites of haplogroup M9a1a1c1b, were significantly higher in the high-altitude group compared with that in the low-altitude group (P=0.012 and 0.02, respectively). Our results suggest that mitochondrial haplogroups B and M7 are associated with inadaptability to hypoxic environments, whereas haplogroups G and M9a1a1c1b may be associated with hypoxic adaptation. In particular, the T3394C and G7697A variants on haplogroup M9a1a1c1b may be the primary cause of adaptation to hypoxia.

Genomic and phenotypic differentiation of Arabidopsis thaliana along altitudinal gradients in the North Italian Alps.

Altitudinal gradients in mountain regions are short-range clines of different environmental parameters such as temperature or radiation. We investigated genomic and phenotypic signatures of adaptation to such gradients in five Arabidopsis thaliana populations from the North Italian Alps that originated from 580 to 2350m altitude by resequencing pools of 19-29 individuals from each population. The sample includes two pairs of low- and high-altitude populations from two different valleys. High-altitude populations showed a lower nucleotide diversity and negative Tajima's D values and were more closely related to each other than to low-altitude populations from the same valley. Despite their close geographic proximity, demographic analysis revealed that low- and high-altitude populations split between 260000 and 15000years before present. Single nucleotide polymorphisms whose allele frequencies were highly differentiated between low- and high-altitude populations identified genomic regions of up to 50kb length where patterns of genetic diversity are consistent with signatures of local selective sweeps. These regions harbour multiple genes involved in stress response. Variation among populations in two putative adaptive phenotypic traits, frost tolerance and response to light/UV stress was not correlated with altitude. Taken together, the spatial distribution of genetic diversity reflects a potentially adaptive differentiation between low- and high-altitude populations, whereas the phenotypic differentiation in the two traits investigated does not. It may resemble an interaction between adaptation to the local microhabitat and demographic history influenced by historical glaciation cycles, recent seed dispersal and genetic drift in local populations.

Does regenerative strategy vary between populations? A test using a narrowly distributed Atlantic Rainforest palm species

Germination rate and seed mass are important factors determining the proportion of seedlings that become established in a habitat, especially where resources are limited and under adverse environmental conditions. Variation in seed attributes can determine a species’ potential to adapt to new climates. This study aimed to investigate the germination behavior of Lytocaryum weddellianum along climatic gradients at two altitudes in the Serra dos Orgaos, Rio de Janeiro, Brazil. We conducted ex situ experiments on germination under two light conditions (light or dark) and three levels of water potential (Ψ = 0, −0.4 or −0.8 MPa) over 8 months. In addition, seeds of different sizes were sown and after 6 months seedlings were divided into shoot and root components. The following growth parameters were measured: root, shoot and total biomass, leaf area, specific leaf area and leaf area ratio. Our results showed that the high- and low-altitude populations had different germination rates, seed mass, and resource allocation in seedlings. The lower altitude population, with higher temperatures and humidity, higher germination rates, produced heavier seeds, and their seedlings invested more in root and total biomass. Meanwhile, seedlings from the higher altitude site, with less available light, had a greater investment in foliar parameters. These differences in the two populations’ seedling establishment strategies over an altitudinal gradient in the Serra dos Orgaos suggest that the species may have the potential to adapt to predicted climate change in this region.

Adaptation to low temperatures in the wild tomato species Solanum chilense.

Molecular adaptation to abiotic stresses in plants is a complex process based mainly on the modifications of gene transcriptional activity and the alteration of protein-protein interactions. We used a combination of population genetic, comparative transcriptomic and plant physiology approaches to investigate the mechanisms of adaptation to low temperatures in Solanum chilense populations distributed along Andean altitudinal gradients. We found that plants from all populations have high chilling tolerance, which does not correlate with temperatures in their native habitats. In contrast, tolerance to freezing shows a significant association with altitude and temperature variables. We also observed the differences in expression patterns of cold-response genes between plants from high- and low-altitude populations. These results suggest that genetic adaptations to low temperatures evolved in high-altitude populations of S.chilense. At the transcriptional level, these adaptations may include high levels of constitutive expression of the genes encoding ICE1, the key transcription factor of the cold signalling pathway, and chloroplast ω-3 fatty acid desaturase FAD7. At the sequence level, a signature of selection associated with the adaptation to high altitudes was detected at the C-terminal part of ICE1 encoding the ACT regulatory domain.

Transcriptomic plasticity in brown adipose tissue contributes to an enhanced capacity for nonshivering thermogenesis in deer mice.

For small mammals living at high altitude, aerobic heat generation (thermogenesis) is essential for survival during prolonged periods of cold, but is severely impaired under conditions of hypobaric hypoxia. Recent studies in deer mice (Peromyscus maniculatus) reveal adaptive enhancement of thermogenesis in high- compared to low-altitude populations under hypoxic cold stress, an enhancement that is attributable to modifications in the aerobic metabolism of muscles used in shivering. However, because small mammals rely heavily on nonshivering mechanisms for cold acclimatization, we tested for evidence of adaptive divergence in nonshivering thermogenesis (NST) under hypoxia. To do so, we measured NST and characterized transcriptional profiles of brown adipose tissue (BAT) in high- and low-altitude deer mice that were (i) wild-caught and acclimatized to their native altitude, and (ii) born and reared under common garden conditions at low elevation. We found that NST performance under hypoxia is enhanced in wild-caught, high-altitude deer mice, a difference that is associated with increased expression of coregulated genes that influence several physiological traits. These traits include vascularization and O2 supply to BAT, brown adipocyte proliferation and the uncoupling of oxidative phosphorylation from ATP synthesis in the generation of heat. Our results suggest that acclimatization to hypoxic cold stress is facilitated by enhancement of nonshivering heat production, which is driven by regulatory plasticity in a suite of genes that influence intersecting physiological pathways.

Facing the Heat: Thermoregulation and Behaviour of Lowland Species of a Cold-Dwelling Butterfly Genus, Erebia.

Understanding the potential of animals to immediately respond to changing temperatures is imperative for predicting the effects of climate change on biodiversity. Ectothermic animals, such as insects, use behavioural thermoregulation to keep their body temperature within suitable limits. It may be particularly important at warm margins of species occurrence, where populations are sensitive to increasing air temperatures. In the field, we studied thermal requirements and behavioural thermoregulation in low-altitude populations of the Satyrinae butterflies Erebia aethiops, E. euryale and E. medusa. We compared the relationship of individual body temperature with air and microhabitat temperatures for the low-altitude Erebia species to our data on seven mountain species, including a high-altitude population of E. euryale, studied in the Alps. We found that the grassland butterfly E. medusa was well adapted to the warm lowland climate and it was active under the highest air temperatures and kept the highest body temperature of all species. Contrarily, the woodland species, E. aethiops and a low-altitude population of E. euryale, kept lower body temperatures and did not search for warm microclimates as much as other species. Furthermore, temperature-dependence of daily activities also differed between the three low-altitude and the mountain species. Lastly, the different responses to ambient temperature between the low- and high-altitude populations of E. euryale suggest possible local adaptations to different climates. We highlight the importance of habitat heterogeneity for long-term species survival, because it is expected to buffer climate change consequences by providing a variety of microclimates, which can be actively explored by adults. Alpine species can take advantage of warm microclimates, while low-altitude grassland species may retreat to colder microhabitats to escape heat, if needed. However, we conclude that lowland populations of woodland species may be more severely threatened by climate warming because of the unavailability of relatively colder microclimates.

Plasticity of metamorphic traits in a high-altitude toad: interactive effects of food level and temperature

In organisms with complex life cycles, such as amphibians, morphological variation itself is strongly influenced by environmental factors and maternal effects. Although temperature and food level exert a strong influence on larval growth and development, little is known about the interacting effects of these factors on age and size at metamorphosis. In this study, plasticity in growth rates, larval mass, larval period, and body size at metamorphosis were experimentally examined for a high-altitude toad (Bufo minshanicus) under different combinations of temperature and food level. Larval period and mass at metamorphosis were sensitive to food level, and varied with temperature. At high food level, tadpoles reared at 29.8°C had shorter larval period lengths and larger mass at metamorphosis than those reared at 25.8 and 22.6°C, but not between 25.8 and 22.6°C. Interestingly, tadpoles at 29.8°C that were offered with a higher level of food supply achieved a larger size than those with a lower level of food supply; however, food supply did not affect body mass at the two lower temperature settings. Thus, the effects of food level were dependent on water temperature. Although there was high mortality at 29.8°C, surviving tadpoles have been much stronger to achieve faster growth and reach a larger mass at metamorphosis, which were positively correlated with juvenile survival and adult fecundity. Thus, under varied environmental conditions, we could say that there is more plasticity in development and growth of larvae in high altitude populations than in the same species or other species from low altitude populations.

Mitochondrial physiology in the skeletal and cardiac muscles is altered in torrent ducks, Merganetta armata, from high altitudes in the Andes.

Torrent ducks inhabit fast-flowing rivers in the Andes from sea level to altitudes up to 4500 m. We examined the mitochondrial physiology that facilitates performance over this altitudinal cline by comparing the respiratory capacities of permeabilized fibers, the activities of 16 key metabolic enzymes and the myoglobin content in muscles between high- and low-altitude populations of this species. Mitochondrial respiratory capacities (assessed using substrates of mitochondrial complexes I, II and/or IV) were higher in highland ducks in the gastrocnemius muscle - the primary muscle used to support swimming and diving - but were similar between populations in the pectoralis muscle and the left ventricle. The heightened respiratory capacity in the gastrocnemius of highland ducks was associated with elevated activities of cytochrome oxidase, phosphofructokinase, pyruvate kinase and malate dehydrogenase (MDH). Although respiratory capacities were similar between populations in the other muscles, highland ducks had elevated activities of ATP synthase, lactate dehydrogenase, MDH, hydroxyacyl CoA dehydrogenase and creatine kinase in the left ventricle, and elevated MDH activity and myoglobin content in the pectoralis. Thus, although there was a significant increase in the oxidative capacity of the gastrocnemius in highland ducks, which correlates with improved performance at high altitudes, the variation in metabolic enzyme activities in other muscles not correlated to respiratory capacity, such as the consistent upregulation of MDH activity, may serve other functions that contribute to success at high altitudes.

Ecological niche modelling of three Mediterranean pine species in the south of Spain: a tool for afforestation/reforestation programs in the twenty-first century

Climate change models predict an increase in aridity in many parts of the world for the twenty-first century, which is likely to be more intense in the Mediterranean basin than in other regions. This study addresses the potential distribution of three Mediterranean pine species (Pinus pinea L., P. halepensis Mill. and P. pinaster Aiton) in southern Spain in response to the forecast increased aridity. Pines constitute a useful source of various types of raw materials, which has led to their increasing introduction around the world. The study was based on ecological niche modelling using multinomial logistic regression, over an area spanning about 8.7 million ha in the south of Spain. In total, 11 explanatory variables were included, drawing on measurements made at high resolution (200 m). Four different periods were studied: the reference period (1961–2000), early twenty-first century (2011–2040), middle twenty-first century (2041–2070) and late twenty-first century (2071–2100). Future time slices were analysed in three different scenarios: B1, A1b and A2 in the CNCM3 general circulation model. The results predict a wider distribution for stone pine, which could expand its potential area in southern Spain. In contrast, Aleppo pine, and especially cluster pine, would reduce their present distribution, with cluster pine occupying higher altitude sites while low altitude populations diminished. The validation model enables accurate maps to be produced, representing powerful tools for afforestation/reforestation programs in the future.