Lowland Counterparts Research Articles

Metabolic recovery from submaximal exercise in hypoxia acclimated high altitude deer mice (Peromyscus maniculatus)

Animals living at high-altitude are faced with unremitting low oxygen availability. This can make it difficult to perform daily tasks that require increases in aerobic metabolism. An activity important for survival is aerobic locomotion, and the rapid recovery of muscle metabolism post exercise. Past work shows that hypoxia acclimated high-altitude mice (Peromyscus maniculatus) have a greater reliance on carbohydrates to power exercise than low altitude mice. However, it is unclear how quickly after aerobic exercise these mice can recovery and replenish muscle glycogen stores. The gastrocnemius muscle of high-altitude deer mice has a more aerobic phenotype and a greater capacity to oxidize lipids than low altitude deer mice. This suggests that high altitude mice may recover more rapidly from exercise than their lowland counterparts due to a greater capacity to support glycogen replenishment using intramuscular triglycerides (IMTG). To explore this possibility, we used low- and high-altitude native deer mice born and raised in common lab conditions and acclimated to chronic hypoxia. We determined changes in oxygen consumption following 15 min of aerobic exercise in 12% O2 and sampled skeletal muscles and liver at various time points during recovery to examine changes in key metabolites, including glycogen and IMTG. We found depletion in glycogen stores during exercise only in lowlanders, which returned to resting levels following 90 min of recovery. In contrast, IMTG did not change significantly with exercise or during recovery in either population. These data suggest that exercise recovery is influenced by altitude ancestry in deer mice.

Food security drive and adoption of improved rice varieties on the production efficiencies of upland and lowland rice farmers in north-central Nigeria

To attain the food security target of the country, fostering farmers’ adoption of improved rice varieties will go a long way toward closing the lingering production deficit gap in Nigeria, and meeting up with the ever-increasing demand for rice consumption in the country. This study investigated the effect of the adoption of improved rice varieties on the production efficiencies of rice farmers in the north-central Nigeria. A multistage sampling technique was uses to select 387 rice farmers, which includes 201 upland and 186 lowland rice farmers in the study area. A stochastic frontier analytical model (SFA) was employed to estimate production efficiencies (technical, economic and allocative) for the rice farmers. Further, a multivariate regression analysis (MVA) was applied to determine the effect of adoption on the efficiency levels of the rice farmers. The exploratory analysis of the data revealed that the rice varieties available for adoption by the rice farmers in the study area is 10, but both upland and lowland rice farmers adopted more of two rice varieties (Faro-46 and Faro-52). From the SFA results, most of the rice farmers have mean technical, economic and allocative efficiencies of 0.7, 0.54 and 0.76 respectively. The SFA estimates also indicated that seed, herbicide, fertilizer, farm size and capital assets significantly affect the efficiency of upland rice farmers, while the efficiency of their lowland counterparts is influenced by seed, farm size capital and herbicide, amongst others. The MVA estimates also showed that the adoption rate of improved rice varieties, years of formal education, and farm-level factors made significant contributions to the efficiency levels of the rice farmers. Importantly, the levels of adoption of all rice varieties by farmers indeed influenced their technical and economic efficiency, while having no impact on their allocative efficiency. The study recommended that the government, research institutes and developmental agencies should promote easy access to improved rice varieties by farmers, as this can further drive sustained adoption. This can evidently help to achieve desirable yield and enhance the efficiency level of the rice farmers and boost food availability and achieve the zero-hunger target in the study area and Nigeria at large.

Cost and returns analysis of upland and lowland rice production among farmers in North Central Nigeria

Sustainability of the rice production and farmers’ income in Nigeria raises a serious concern due to the rising costs of production inputs and other factors beyond farmers’ control. As a result, the study compared the cost and returns of rice production in North central, Nigeria. A multistage sampling technique was used to select 387 rice farmers in the study area. Descriptive statistics, gross margin analysis and seeming unrelated regression were used to analyze the dataset collected. The findings revealed that most of the rice farmers were male, averagely young and have at least 9 family members in their respectively households. Results from Kwara State showed that total cost is higher among the upland rice farmers compared to their lowland counterparts, but reverse was the case in term of net profit, as this favoured the lowland rice farmers. For Niger State and pooled data, the lowland rice farmers had higher net profit than the upland rice farmers. Seemingly unrelated regression estimates indicated that costs associated with fertilizer, herbicide, seed, pesticide and labour used were significant and influencing factors affecting the revenue of rice farmers in the study area. While inaccessibility to cheap farm inputs was the major constraint affecting the rice farmers, other challenges include lack of storage, inadequate rainfall and inadequate credit facilities. The study recommended seamless access to improved rice varieties by the farmers as this can scale up adoption of improved technologies, boost production and ultimately the net revenue of rice farmers. Farmers are also advised to join and/or form a registered occupational groups through which credit facilities can easily be accessed, to expand the farming operations because of the positive and complementary role of social group and access to credit.

Fundamental but underrepresented: root carbon stocks in African montane forests

African montane forests harbor some of the greatest biodiversity worldwide, with high levels of species endemism. However, the loss of these forests through fragmentation, deforestation and climate change has been rapidly increasing in recent years. Montane forests in Africa are more susceptible to changes in climate than their lowland counterparts, yet their ecological value is still underrepresented. These montane forests have recently been highlighted as a major aboveground carbon (C) stock. The estimated 149.4 Mg C ha−1 from aboveground live trees surpasses estimates from the Intergovernmental Panel on Climate Change for these endangered forests, and exceeds reported values for neotropical montane and lowland forests by up to 70%. Despite the tremendous implications of these findings, coordinated and available research on the C storage potential of the other share of African montane forest biomass, that is in tree roots, is largely missing. Broadly estimated from the allometry of aboveground C stocks and from root:shoot ratios in lowland forests, more than 60 Mg C ha−1 can be stored in African montane forest roots, about 40% more than previously determined. While this broad estimation points at the potential importance of root C stocks in African montane forests, it also unveils a far-reaching knowledge gap. Here, we advocate for a more quantitative representation of the root C stock from dominant forest tree species of African tropical montane forests and ultimately for a better grasp on tree C stocks from this endangered ecosystem.

Exploring the evidence of Middle Amazonian aquifer sedimentary outburst residues in a Martian chaotic terrain

The quest for past Martian life hinges on locating surface formations linked to ancient habitability. While Mars' surface is considered to have become cryogenic ~3.7 Ga, stable subsurface aquifers persisted long after this transition. Their extensive collapse triggered megafloods ~3.4 Ga, and the resulting outflow channel excavation generated voluminous sediment eroded from the highlands. These materials are considered to have extensively covered the northern lowlands. Here, we show evidence that a lacustrine sedimentary residue within Hydraotes Chaos formed due to regional aquifer upwelling and ponding into an interior basin. Unlike the northern lowland counterparts, its sedimentary makeup likely consists of aquifer-expelled materials, offering a potential window into the nature of Mars' subsurface habitability. Furthermore, the lake’s residue’s estimated age is ~1.1 Ga (~2.3 Ga post-peak aquifer drainage during the Late Hesperian), enhancing the prospects for organic matter preservation. This deposit’s inferred fine-grained composition, coupled with the presence of coexisting mud volcanoes and diapirs, suggest that its source aquifer existed within abundant subsurface mudstones, water ice, and evaporites, forming part of the region’s extremely ancient (~ 4 Ga) highland stratigraphy. Our numerical models suggest that magmatically induced phase segregation within these materials generated enormous water-filled chambers. The meltwater, originating from varying thermally affected mudstone depths, could have potentially harbored diverse biosignatures, which could have become concentrated within the lake’s sedimentary residue. Thus, we propose that Hydraotes Chaos merits priority consideration in future missions aiming to detect Martian biosignatures.

Selection on embryonic haemoglobin in an elevational generalist songbird

Animals developing at high elevation experience a suite of environmental challenges, most notably the low partial pressure of oxygen (PO2) in ambient air. In low PO2, bird species with high-elevation ancestry consistently demonstrate higher hatching success than lowland counterparts, suggesting highland birds are adapted to restricted O2 (hypoxia) in early development. Haemoglobin (Hb), the critical oxygen-transport protein, is a likely target of PO2-related selection across ontogeny since Hb isoforms expressed at distinct developmental stages demonstrate different O2 affinities. To test if Hb function is under PO2-related selection at different ontogenetic stages, we sampled a songbird, the hooded siskin (Spinus magellanicus), across two approximately 4000 m elevational transects. We sequenced all of the loci that encode avian Hb isoforms, and tested for signatures of spatially varying selection by comparing divergence patterns in Hb loci to other loci sampled across the genome. We found strong signatures of diversifying selection at non-synonymous sites in loci that contribute to embryonic (απ, βH) and definitive (βA) Hb isoforms. This is the first evidence for selection on embryonic haemoglobin in high-elevation Neoaves. We conclude that selection on Hb function at brief, but critical stages of ontogeny may be a vital component to high elevation adaptation in birds.

The Wa of Myanmar and China's Quest for Global Dominance by Bertil Lintner

Reviewed by: The Wa of Myanmar and China's Quest for Global Dominance by Bertil Lintner Jane M. Ferguson Bertil Lintner. 2021. The Wa of Myanmar and China's Quest for Global Dominance. Chiang Mai: Silkworm. 272 pages. ISBN 9786162151705 This slim, but richly detailed, volume represents a recent installment in veteran journalist and prolific author Bertil Lintner's foundational contributions to our understanding of the complex dynamics of Myanmar's politics, and especially those of its peripheries. The areas brought to focus here are the bordering highlands of Northern Shan State and the Southwest of China's Yunnan province, territories long off-limits to other empire-building projects. These edgy zones set the context for the travails of the United Wa State Army (UWSA), the most sizable and best-equipped non-state military in Asia today. The UWSA boasts commanding around twenty to thirty thousand troops, and including weaponry has more firepower than the Communist Party of Burma ever had in the region. [End Page 138] Lintner draws upon extensive experience and direct contacts, including having visited and interviewed Wa soldiers when they were part of the Communist Party of Burma during the late 1980s, and spent months in Wa areas getting to know commanders and villagers who communicated with him in the Shan language. Lintner has returned to the area more recently, at the UWSA's northern capital of Pangkham, the headquarters and boomtown for the Wa state, now an autonomous region at the Shan State–Yunnan border. Lintner carefully traces how ongoing wars, battles for economic access, and political sovereignty have embroiled these areas of Shan State for over seven decades. The book looks outward to how this particular situation has implications for Myanmar–China relationships, past and present, but also how their development and expansion have been intertwined with the Chinese government's changing ideological and economic orientations toward its Southeast Asian neighbors. The book itself consists of six chapters detailing the social and political terrain of the Wa, from mythical histories, colonial noninterference, the Communist Party of Burma, the mutiny against the latter and subsequent foundation of the UWSA, the UWSA's relationship to narcotics and changing global economies, and finally their relationship with contemporary politics and the changing geostrategic agenda of China. One section at the back, "Dramatis Personae" is useful to refer to while reading the body chapters of the book; quite a bewildering number of players are involved. Lintner discusses the history of the Wa area as a zone off-limits to state incorporation until only very recently; part and parcel to this, the Wa were frequently described as wild, even savage. Their headhunting practices perpetuated this stereotype, though it has been argued that [End Page 139] this was more a ritual of war trophies, not making the Wa intrinsically—let alone by "nature"—more brutal or violent than their lowland counterparts who engaged in fatal warfare themselves. Lintner's examination of the historical relationship between Wa communities and Cold War geopolitics is essential background for the current situation; the Wa people themselves were not committed to the ideologies of the Communist Party of Burma (CPB). In reality, the CPB had done little for the ethnic Wa troops and communities who had hardly any interest in the Party's ostensible ideological goals nor its inadequately configured agricultural plans for the area, and lack of concrete efforts to develop the region. In a tinge of irony, or perhaps as evidence that CPB ideology should not frame economic expectations, the years of the Burmese Socialist Program Party in Burma saw an increasing ramping-up of the black market in the periphery and a thriving economy for free trade in these CPB controlled areas (p. 102). From the late 1980s, Lintner saw the writing on the wall that the Wa troops themselves saw little to gain by working with the CPB, and following their 1989 mutiny, sought the relative benefits of working with the Chinese as well as establishing an autonomous region through a cease-fire agreement with the (then) Rangoon government. Through the buildup of weaponry and territory (especially following the vacuum left behind by Khun Sa's surrender of the Möng Tai...

Tibetan birds lay larger but fewer eggs in a clutch.

How do offspring size and number vary along elevational gradients? This is a striking but rarely addressed question in life-history evolution. Here we comparatively explore it using phylogenetically paired passerine birds of lowland China vs. the Tibetan plateau spanning an elevational range of 18-4500m. Toward the Tibetan plateau, egg size increased, clutch size decreased and total clutch volume (= clutch size × egg size) did not change, when accounting for major confounding factors. Larger eggs and smaller clutches can be a response to harsh abiotic conditions at higher elevations and the corresponding reduction in food resources required for raising young, respectively. There was a negative correlation between egg size and clutch size after controlling for elevation effect on either trait, suggesting that the trade-off contributed to the expression of these two traits across elevations, given the lack of an elevational trend in total clutch volume. Tibetan birds had a shorter breeding season, prolonged incubation and nestling period than their lowland counterparts. While fewer clutches over the short breeding season may facilitate the increase in egg size, the concentration of annual reproductive investment did not seem to act on clutch size; despite the smaller clutches, hard environments may impose greater costs of parental care on Tibetan birds. The current research provides insight into the evolution of avian life histories across elevations.

Scots pine bog woodlands in the Eastern Carpathians versus their northern, lowland counterparts: floristic dissimilarities and underlying ecological gradients

Scots pine bog woodlands in the Eastern Carpathians versus their northern, lowland counterparts: floristic dissimilarities and underlying ecological gradients

Genotyped indigenous Kiwcha adults at high altitude are lighter and shorter than their low altitude counterparts

BackgroundAnthropometric measures have been classically used to understand the impact of environmental factors on the living conditions of individuals and populations. Most reference studies on development and growth in which anthropometric measures were used were carried out in populations that are located at sea level, but there are few studies carried out in high altitude populations.ObjectiveThe objective of this study was to evaluate the anthropometric and body composition in autochthonous Kiwcha permanently living at low and high altitudes.MethodologyA cross-sectional study of anthropometric and body composition between genetically matched lowland Kiwcha from Limoncocha (n = 117), 230 m in the Amazonian basin, and high-altitude Kiwcha from Oyacachi (n = 95), 3800 m in Andean highlands. Student’s t-test was used to analyze the differences between continuous variables, and the chi-square test was performed to check the association or independence of categorical variables. Fisher’s exact test or Spearman’s test was used when the variable had evident asymmetries with histograms prior to the selection of the test.ResultsThis study shows that high altitude men are shorter than their counterparts who live at low altitude, with p = 0.019. About body muscle percentage, women at high altitudes have less body muscle percentage (− 24.8%). In comparison, men at high altitudes have significantly more muscle body mass percentage (+ 13.5%) than their lowland counterparts. Body fat percentage was lower among low altitude women (− 15.5%), and no differences were found among men.ConclusionsThis is the first study to be performed in two genotyped controlled matching populations located at different altitudes to our best knowledge. The anthropometric differences vary according to sex, demonstrating that high altitude populations are, in general, lighter and shorter than their low altitude controls. Men at high altitude have more muscled bodies compared to their lowland counterparts, but their body age was older than their actual age.

Padrão de expressão dos genes CRYAB e CTGF em duas raças de suínos em altitudes diferentes

ABSTRACT Tibetan pigs are characterized by significant phenotypic differences relative to lowland pigs. Our previous study demonstrated that the genes CRYAB and CTGF were differentially expressed in heart tissues between Tibetan (highland breed) and Yorkshire (lowland breed) pigs, indicating that they might participate in hypoxia adaptation. CRYAB (ɑB-crystallin) and CTGF (connective tissue growth factor) have also been reported to be associated with lung development. However, the expression patterns of CRYAB and CTGF in lung tissues at different altitudes and their genetic characterization are not well understood. In this study, qRT-PCR and western blot of lung tissue revealed higher CRYAB expression levels in highland and middle-highland Tibetan and Yorkshire pigs than in their lowland counterparts. With an increase in altitude, the expression level of CTGF increased in Tibetan pigs, whereas it decreased in Yorkshire pigs. Furthermore, two novel single-nucleotide polymorphism were identified in the 5′ flanking region of CRYAB (g.39644482C>T and g.39644132T>C) and CTGF (g.31671748A>G and g.31671773T>G). The polymorphism may partially contribute to the differences in expression levels between groups at the same altitude. These findings provide novel insights into the high-altitude hypoxia adaptations of Tibetan pigs.

Altitudinal seasonality as a potential driver of morphological diversification in rear-edge bird populations

Populations at the low latitude limits of a species range (rear-edge populations) are often considered more vulnerable to climate change. However, their ability to track different environmental settings at a regional scale has been widely overlooked, although this may be relevant to accurately assess their adaptive capacity to cope with ongoing changes. Here we tested whether the endemic African Chaffinch (Fringilla coelebs africana) tracks environmental changes (e.g. decreasing temperatures, snow cover) by rearranging their numbers between seasons (spring vs. winter) along the altitude gradients of its northwestern African range. We additionally tested whether these seasonal changes in abundance were paralleled by morphological variation, suggesting a process of population diversification. We assessed African Chaffinch abundance in tree covered farmland and woodland sites distributed along an altitude gradient in spring and winter. In addition, we captured and measured chaffinches within the study gradient to explore the patterns of morphological variation. Our results showed that chaffinches shifted to lowlands from snow covered highlands during winter. In addition, highland individuals showed longer and more concave wings than their lowland counterparts. These morphological traits are usually related to flight efficiency in migratory birds, which suggest the presence of altitudinal movements aimed to track the environmental seasonality caused by orography. These results suggest a potential role of altitudinal seasonality as a driver of regional diversification within the African Chaffinch populations, which could be occurring in other North African avian species given their relatively high endemicity in the region. The evolutionary and conservation implications of these displacements have been often overlooked despite they can shape the adaptive capacity of rear-edge bird populations to face the ongoing environmental changes in this peripheral area of the Palearctic.

Increased Reliance on Carbohydrates for Aerobic Exercise in Highland Andean Leaf-Eared Mice, but Not in Highland Lima Leaf-Eared Mice

Exercise is an important performance trait in mammals and variation in aerobic capacity and/or substrate allocation during submaximal exercise may be important for survival at high altitude. Comparisons between lowland and highland populations is a fruitful approach to understanding the mechanisms for altitude differences in exercise performance. However, it has only been applied in very few highland species. The leaf-eared mice (LEM, genus Phyllotis) of South America are a promising taxon to uncover the pervasiveness of hypoxia tolerance mechanisms. Here we use lowland and highland populations of Andean and Lima LEM (P. andium and P. limatus), acclimated to common laboratory conditions, to determine exercise-induced maximal oxygen consumption (O2max), and submaximal exercise metabolism. Lowland and highland populations of both species showed no difference in O2max running in either normoxia or hypoxia. When run at 75% of O2max, highland Andean LEM had a greater reliance on carbohydrate oxidation to power exercise. In contrast, highland Lima LEM showed no difference in exercise fuel use compared to their lowland counterparts. The higher carbohydrate oxidation seen in highland Andean LEM was not explained by maximal activities of glycolytic enzymes in the gastrocnemius muscle, which were equivalent to lowlanders. This result is consistent with data on highland deer mouse populations and suggests changes in metabolic regulation may explain altitude differences in exercise performance.

Coping with extremes: lowered myocardial phosphofructokinase activities and glucose content but increased fatty acids content in highland Eurasian Tree Sparrows

BackgroundEfficient and selective utilization of metabolic substrates is one of the key strategies in high-altitude animals to cope with hypoxia and hypothermia. Previous findings have shown that the energy substrate utilization of highland animals varies with evolutionary history and phylogeny. The heart is a proxy for the cardiopulmonary system, and the metabolic substrate utilization in the myocardium is also under the strong selective pressure of chronically hypoxic and hypothermic environments. However, little information is available on the physiological adjustments in relation to metabolic substrate utilization in the myocardium for coping with high-altitude environments.MethodsWe compared the metabolic enzyme activities, including hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), citrate synthase (CS), carnitine palmitoyl transferase 1 (CPT-1), lactic dehydrogenase (LDH), and creatine kinase (CK), and metabolic substrate contents including glucose (Glu), triglyceride (TG), and free fatty acid (FFA) in the myocardium of a typical human commensal species, Eurasian Tree Sparrows (Passermontanus) between the Qinghai-Tibet Plateau (the QTP, 3230 m) and low altitude population (Shijiazhuang, 80 m), and between sexes.ResultsAmong the seven metabolic enzymes and three substrates investigated, we identified no significant differences in PK, CPT-1, HK, CS, LDH, and CK activities and TG content of the myocardium between high and low altitude populations. However, the QTP sparrows had significantly lower Glu content and PFK activities but higher FFA content relative to their lowland counterparts. In addition, male sparrows had higher myocardial HK and CS activities relative to females, independent of altitude.ConclusionsOur results showed that the QTP sparrows elevated fatty acid utilization rather than glucose preference in the myocardium relative to lowland counterpart, which contributes to uncovering both the physiological adjustments for adapting to the extreme conditions of the QTP, intraspecifically.

Coping with extremes: High-altitude sparrows enhance metabolic and thermogenic capacities in the pectoralis muscle and suppress in the liver relative to their lowland counterparts

Animals living at high altitudes are challenged by the extreme environmental conditions of cold temperature and hypobaric hypoxia. It is not well understood how high-altitude birds enhance the capacity of metabolic thermogenesis and allocate metabolic capacity in different organs to maximize survival in extreme conditions of a cold winter. The Qinghai-Tibet Plateau (QTP) is the largest and highest plateau globally, offering a natural laboratory for investigating coping mechanisms of organisms inhabiting extreme environments. To understand the adaptive strategies in the morphology and physiology of small songbirds on the QTP, we compared plasma triiodothyronine (T3), pectoralis muscle mitochondrial cytochrome c oxidase (COX) and state IV capacities, the expression of peroxisome proliferator-activated receptor γ coactivator α (PGC-1α), adenine nucleotide translocase (ANT), uncoupling protein (UCP), and adenosine monophosphate‐dependent kinase (AMPK) α1 mRNA in the pectoralis and liver of Eurasian tree sparrows (Passer montanus) from high-altitude (3,230 m), medium-altitude (1400 m), and low-altitude (80 m) regions. Our results showed that high-altitude sparrows had greater body masses, longer wings and tarsometatarsi, but comparable bill lengths relative to medium- and low-altitude individuals. High-altitude sparrows had higher plasma T3 levels and pectoralis muscle mitochondrial COX capacities than their lowland counterparts. They also upregulated the pectoralis muscle mRNA expression of UCP, PGC-1α, and ANT proteins relative to low-altitude sparrows. Unlike pectoralis, high-altitude sparrows significantly down-regulated hepatic AMPKα1 and ANT protein expression as compared with their lowland counterparts. Our results contribute to understanding the morphological, biochemical, and molecular adaptations in free-living birds to cope with the cold seasons in the extreme environment of the QTP.

A test of altitude-related variation in aerobic metabolism of Andean birds.

Endotherms at high altitude face the combined challenges of cold and hypoxia. Cold increases thermoregulatory costs, and hypoxia may limit both thermogenesis and aerobic exercise capacity. Consequently, in comparisons between closely related highland and lowland taxa, we might expect to observe consistent differences in basal metabolic rate (BMR), maximal metabolic rate (MMR) and aerobic scope. Broad-scale comparative studies of birds reveal no association between BMR and native elevation, and altitude effects on MMR have not been investigated. We tested for altitude-related variation in aerobic metabolism in 10 Andean passerines representing five pairs of closely related species with contrasting elevational ranges. Mass-corrected BMR and MMR were significantly higher in most highland species relative to their lowland counterparts, but there was no uniform elevational trend across all pairs of species. Our results suggest that there is no simple explanation regarding the ecological and physiological causes of elevational variation in aerobic metabolism.

The MIS 5a (~80 ka) Middle Stone Age lithic assemblages from Melikane Rockshelter, Lesotho: Highland adaptation and social fragmentation

Multidisciplinary research suggests that Marine Isotope Stage 5 (~130–74 ka) was an important evolutionary stage in African deep history. Population expansion and growth spurred changes in material culture as well as the exploration of previously unoccupied regions and ecosystems. The archaeological sequence at Melikane Rockshelter (1860 masl) in the Maloti-Drakensberg Mountains of highland Lesotho, southern Africa, stretches from the late Holocene back to sub-stage 5a, ~80 ka. The site's earliest strata represent one of the earliest known examples of a sustained human presence in high mountain systems worldwide. This paper deals with the lithic assemblages from those levels, which are currently the oldest radiometrically dated archaeology in Lesotho and one of the few stratified assemblages of Last Interglacial age in the southern African interior. The results of a typo-technological analysis of the assemblages are presented. They suggest that the afromontane foragers who resided at Melikane employed both blade-focussed and bipolar flaking systems, curated a maintainable toolkit suited to frequent residential moves, and used a hybrid provisioning system adapted to their immediate environment. Comparisons with other late Last Interglacial assemblages across the subcontinent suggest that highland populations at this time were largely disconnected from their lowland counterparts. This implies that as Last Interglacial populations in southern Africa expanded into new environments, they also fragmented, adapting to local conditions rather than adhering to a universal technological system.

Genetic consequences of being a dwarf: do evolutionary changes in life-history traits influence gene flow patterns in populations of the world's smallest goldenrod?

Contrasting life-history traits can evolve through generations of dwarf plant ecotypes, yet such phenotypic changes often involve decreased plant size and reproductive allocation, which can configure seed dispersal patterns and, subsequently, population demography. Therefore, evolutionary transitions to dwarfism can represent good study systems to test the roles of life-history traits in population demography by comparing genetic structure between related but phenotypically divergent ecotypes. In this study, we examined an ecotypic taxon pair of the world's smallest goldenrod (stem height 2.6 cm) in alpine habitats and its closely related lowland taxon (30-40 cm) found on Yakushima Island, Japan. Genetic variation in chloroplast DNA sequences, nuclear microsatellites and genome-wide single-nucleotide polymorphisms were used to investigate 197 samples from 16 populations, to infer the population genetic demography and compare local genetic structure of the ecotypes. We found a pronounced level of genetic differentiation among alpine dwarf populations, which were much less geographically isolated than their lowland counterparts. In particular, several neighbouring dwarf populations (located ~500 m apart) harboured completely different sets of chloroplast haplotypes and nuclear genetic clusters. Demographic modelling revealed that the dwarf populations have not exchanged genes at significant levels after population divergence. These lines of evidence suggest that substantial effects of genetic drift have operated on these dwarf populations. The low-growing stature and reduced fecundity (only 3.1 heads per plant) of the dwarf plants may have reduced gene flow and rare long-distance seed dispersal among habitat patches, although the effects of life-history traits require further evaluation using ecological approaches.

High heat tolerance in plants from the Andean highlands: Implications for paramos in a warmer world.

Tropical plant species are expected to have high heat tolerance reflecting phenotypic adjustments to warm regions or their evolutionary adaptation history. However, tropical highland specialists adapted to the colder temperatures found in the highlands, where short and prostrated vegetation decouples plants from ambient conditions, could exhibit different upper thermal limits than those of their lowland counterparts. Here we evaluated leaf heat tolerance of 21 tropical alpine paramo species to determine: 1) whether species with restricted distribution (i.e., highland specialists) have lower heat tolerance and are more vulnerable to warming than species with widespread distribution; 2) whether different growth forms have different heat tolerance; and 3) whether species height (i.e., microhabitat) influences its heat tolerance. We quantified heat tolerance by evaluating T50, which is the temperature that causes a reduction in 50% of initial Fv/Fm values and reflects an irreversible damage to the photosynthetic apparatus. Additionally, we estimated the thermal safety margins as the difference between T50 and the maximum leaf temperature registered for the species. All species presented high T50 values ranging between 45.4°C and 53.9°C, similar to those found for tropical lowland species. Heat tolerance was not correlated with species distributions or plant height, but showed a strong relationship with growth form, with rosettes having the highest heat tolerance. Thermal safety margins ranged from 12.1 to 31.0°C. High heat tolerance and broad thermal safety margins suggest low vulnerability of paramo species to warming as long as plants are capable of regulating the leaf temperature within this threshold. Whether paramo plants would be able to regulate leaf temperature if drought episodes become more frequent and transpirational cooling is compromised is the next question that needs to be answered.

Secondary succession has surprisingly low impact on arboreal ant communities in tropical montane rainforest

AbstractUnderstanding forest regeneration processes is increasingly important as disturbed forests spread rapidly in tropical landscapes. While successional dynamics are relatively well‐understood for plants, they remain poorly known for tropical insects, particularly in montane rainforests and tree canopies. We studied the effect of montane forest succession on arboreal ant communities in New Guinea near their natural elevational limit (1800 m a.s.l.). We censused ant species and nests in replicated 0.1‐ha plots of primary, old and young secondary forests, destined to be felled for gardens by the local landowners. Overall, 1249 felled trees were dissected for all ant‐associated microhabitats. We used rarefaction‐based models manipulating vegetation structure and multivariate randomizations to assess the effects of tree density, tree size, and nesting microhabitats on the ant communities. We expected increased ant species diversity, microhabitat specialization, and species turnover among trees throughout the succession, with distinct community composition among the stages. In contrast to our expectations, ant species composition and diversity per plot did not change during succession, and species similarity among trees was significantly higher only in old secondary forest. The number of ant species per tree increased with forest age, but trees of similar size hosted only slightly more species in primary than secondary forests. Many ant species were associated with particular nesting microhabitats; however, the same microhabitat types occurred in all stages and thus did not generate successional trends in ant communities. Secondary succession had an unexpectedly low impact on tree‐dwelling ant communities in this montane ecosystem, in contrast with our previous findings from lowland rainforests. These results highlight the need to study successional processes along entire elevational gradients, as montane taxa may react differently to vegetation changes than their lowland counterparts.