Highland Species Research Articles

Lowland panmixia versus highland disjunction: genetic and bioacoustic differentiation in two species of East African White-eye birds

East-African mountain forest species often occur in small and isolated populations, whereas species inhabiting the dry lowland savannahs exist in large and interconnected population networks. Taxa with closely related highland and lowland species, such as the East- African White-eye birds, allow testing for the potential effects of the two contrasting distribution patterns, moun- tain disjunction versus lowland panmixia. In this study, we compare the population genetic and bioacoustic differen- tiation of two representatives of the genus Zosterops: Zo- sterops poliogaster is exclusively found in forests at higher elevations; in comparison, Zosterops abyssinicus, only occurs in the dry and warm lowland savannahs. Both species were analysed across a similar geographical scale. Population genetic differentiation was inferred using the same set of 15 polymorphic microsatellite loci for both species. In addition, we quantitatively analyzed bioacoustic traits. Both data sets indicate a strong population differ- entiation among populations of the highland species, but an absence of differentiation in the lowland species. In addi- tion, the lowland Z. abyssinicus was characterised by a twofold higher genetic diversity than detected for the highland Z. poliogaster. These two contrasting intraspecific population structures may reflect the opposite ecology and distribution of these species: the strong population isolation of Z. poliogaster resulting from long-term restriction to the cool and moist mountain forests at higher elevations has led to strong differentiation among local populations and resulted in a comparatively low level of intraspecific var- iability. In contrast, population panmixia in the lowland Z. abyssinicus provides a high level of gene flow allowing the maintenance of high genetic diversity and avoiding strong population structuring. These findings need to be consid- ered when planning conservation actions.

A New Species ofLeptobrachiumfrom the Kelabit Highland, Northwestern Borneo (Anura, Megophryidae)

Four species of endemic Leptobrachium are known from Borneo, two lowland species L. kanowitense and L. abbotti, a montane species L. montanum, and a highland species L. gunungense. Of these, both L. montanum and L. abotti were found to contain several cryptic species by recent molecular studies. The population from Bario, Kelabit Highland of Sarawak, is one such cryptic species and was once called Lineage 2 of L. abbotti. Our morphological survey on this population proved that it has characteristics distinct from all other congeners, and therefore, we describe the Bario population as a new species, Leptobrachium kantonishikawai sp. nov. The new species is distinguished from putative topotypes of L. montanum and L. abbotti, as well as from L. gunungense by having a grayish brown abdomen, usually vermiculated, although sometimes spotted or blotched with white, and some unique morphometric characteristics.

Pattern of ant diversity in Korea: An empirical test of Rapoport's altitudinal rule

Two diversity patterns (hump-shaped and monotonic decrease) frequently occur along altitude or latitude gradients. We examined whether patterns of ant species richness along altitudes in South Korea can be described by these patterns and whether ranges of ant species follow Rapoport's altitudinal rule. Ants on 12 high mountains (>1100m) throughout South Korea (from 33° N to 38° N) were surveyed using pitfall traps at intervals of 200–300m altitude. The temperatures at the sampling sites were determined from digital climate maps. Ant species richness decreased monotonically along the altitudinal gradient and increased along the temperature gradient. However, species richness of cold-adapted species (highland species) showed a hump-shaped pattern along altitude and temperature gradients. The altitude and temperature ranges of ant species followed Rapoport's rule. Sampling site temperature ranges were significantly correlated with coldness. Therefore, Rapoport's rule can be explained by high cold-tolerance of species inhabiting high altitudes or latitudes.

Variation in growth traits and survival of landraces of Eucalyptus globulus Labill. in the Ethiopian highlands

Aim of study: Eucalyptus globulus Labill. is the most planted tree species in the Ethiopian highlands due to its potential to satisfy the increasing wood demand of the population. The objectives of this study are to assess the variation in growth traits and survival among E. globulus landraces and clones and to evaluate correlations between growth traits on saplings established in the field.Area of study: The study was performed in the central highlands of Ethiopia.Material and Methods: A landrace trial with Ethiopian seedlings and Spanish cuttings (Sancho and Tinto clones) of E. globulus was carried out. Root collar diameter, height and survival were evaluated on saplings one year after outplanted in the field.Main results: The Spanish landrace showed an improved field performance with 35% higher root collar diameter, 35% taller saplings and 27% higher survival rates as compared to the Ethiopian plants. Sancho clone attained 10% higher root collar diameter than Tinto clone. Strong positive correlation between root collar diameter and height for all saplings was observed (r=0.8785).Research highlights: The present study can be considered as a starting point to implement a breeding program for E. globulus, which is nowadays of great importance in Ethiopia. The introduction of a new Spanish landrace may contribute to broadening the genetic base of this species in Ethiopia. Further tree breeding efforts with E. globulus should be undertaken to raise such genetic base and to increase the productivity of eucalypt plantations in the Ethiopian highlands.Keywords: clone; rural development; tree breeding.

A new species of Brush-Finch (Arremon; Emberizidae) from western Mexico

A new highland species of chestnut-capped Arremon brush-finch is described from the Sierra Madre del Sur of central Guerrero. This form, although indistinguishable in external phenotype from adjacent populations to the east in Oaxaca, is dramatically differentiated in mitochondrial DNA sequence characters, and quite unexpectedly is the sister lineage to the very distinct (phenotype and genotype), central-Mexican-endemic A. virenticeps. Nuclear sequence differentiation in the new lineage is more subtle than in mitochondrial DNA, but is on par with that in the well-marked A. virenticeps. The new species is thus distinct from its sister lineage in genotype and phenotype, and clearly distinct from all other forms in genotype; however, it has retained an ancestral external phenotype similar to other members of the broader A. brunneinucha complex.

Ecological and functional leaf morphology of species of the genus Aquilegia L.

The functional leaf morphology of 13 species and one subspecies of the genus Aquilegia L. was studied in the steppe zone of Ukraine: A. oxysepala Trautv. & C. A. Mey. var. kansuensis Brune, A. buergeriana Sieb. et Zucc., A. flabellata Sieb.et Zucc., A. aurea Janka, A. nigricans Baumg., A. pyrenaica DC., A. canadensis L., A. skinneri Hook., A. chaplinii Standley ex Paysch., A. alpina L., A. einseleana F.W. Schultz, A. sibirica Lam., A. olympica Boiss. There are some common features in all investigated species of this genus introduced in the steppe of Ukraine: 1) a higher leaf indentation (Iz) and correlation of fresh weight to leaf area (m/S) related to increase in the total solar radiation in June, annual precipitation (Is), the sum of temperatures above 10 °C and the duration of period with temperature above 5 °C; 2) higher correlation of fresh and dry weight (m2/m) in the species from dry habitats; 3) higher correlation of fresh leaf weight to petiole length (m/Lp) in the species from warmer habitats; 4) higher correlation of leaf area to petiole length (S/Lp) related to decrease in the total solar radiation in June; 5) higher correlation of leaf petiole length to its diameter (Lp/dp) related to the increase of annual precipitation variation and duration of the period with temperature above 15 °C in their natural habitats. The correlation of dry leaf weight to its area (m2/S) is characterized by the same correspondences as m/S, except for solar radiation. There are significant differences in some parameters in North-American alpine forest species as the steppe climate of Ukraine is much more dry and cold than that of their natural habitats. This causes the adaptive morphologic modification of the leaf. We observe a higher leaf indentation, correlation of fresh weight (m/S) and dry weight (m2/S) to leaf area, correlation of fresh leaf weight to petiole length (m/Lp) in North-American alpine forest species in comparison to highland sub-alpine and lowland forest species of Eurasian origin. The correlation of the leaf area to petiole length (S/Lp) and correlation of fresh and dry weight (m2/m) is higher in the group of subalpine species. The correlation of leaf area to petiole length (S/Lp) is higher in alpine forest species. Highland and lowland forest species are characterized by increase of leaf blade indentation (Iz), a smaller leaf area (S) related to increase in the total solar radiation in June in their natural habitats. They are also characterized by increase in a length of petiole (Lp) and a lower m2/m, related to increase of the difference in annual precipitation and evaporation. Sub-alpine and alpine forest species are characterized in a region of introduction by increase of leaf blade indentation (Iz) and the correlation of fresh weight to leaf area (m/S) related to increased annual precipitation evaporation. Such parameters as Iz, m/S and m2/S are higher in subalpine and alpine forest species from warmer habitats. We have identified the following morphological leaf features which provide its normal functioning in the changing growth conditions: indented edge of the leaf blade, a sufficient accumulation of plastic substances (m2/S) – it is higher in the species from warmer regions with high evaporation. Leaves of the species from warmer regions accumulate more water. The species from warmer regions and warm regions with high evaporation are the most adapted to steppe conditions of Ukraine.

Population genetics of the East African White-eye species complex

The Eastern Afromontane biodiversity hotspot consists of isolated mountain massifs embedded within the dry lowland savannas of East Africa and of which the peaks and ridges are covered by cloud forest remnants. These cloud forests are home to the Mountain White-eye (Zosterops poliogaster), while three congeneric species (Abyssinian White-eye, Zosterops abyssinicus; Yellow White-eye, Zosterops senegalensis; Pemba White-eye, Zosterops vaughani) inhabit the adjacent lowland savannas. We sampled individuals of all four species across Kenya to analyse interspecific genetic relationships as well as intraspecific differentiation among mountain populations of Z. poliogaster. While the level of genetic differentiation among the four species was rather low, genetic differentiation within Z. poliogaster was very high, even between geographically neighbouring populations. Overall, levels of genetic variation varied strongly across all four species, with much higher diversity detected within the three lowland ones. The highland species was characterised by numerous private alleles that were geographically restricted at populations from single mountains, some of which showed evidence of recent population bottlenecks. We conclude that Z. poliogaster populations are both of high conservation value and conservation concern, given the high proportion of endemic alleles and the genetic signatures of high genetic drift and low gene flow that are typical for small and isolated populations.

The small heart of the Ornate Tinamou is compatible with endothermy and flight but compromises aerobic metabolism and thermoregulation during recovery from exhaustive activity

Tinamous are an ancient family of neotropical flying birds. Scant data from a few species show that they have a small heart so our aim was to characterize relative heart size of two species of the genus Nothoprocta and assess the physiological limitations associated with a small heart size. Relative heart size (0.24% for the Ornate Tinamou OT, a highland species and 0.28% for the Chilean Tinamou CT, a lowland species) was significantly smaller than high and lowland chickens (0.54% and 0.42% respectively), without evidence of right ventricular hypertrophy. Resting aerobic metabolism was 31% lower in OT than in highland chickens. When subjected to exhaustive activity, OT had elevated glucose and lactate levels suggesting a severe oxygen debt when exhausted. This was further shown as a significant drop in body temperature after an exhaustive bout. Finally heart rate while running on a treadmill at 3 km h−1 was 5% lower in OT, indicating that tinamous cannot compensate for the reduction in heart size with a faster heart rate. Altogether, we provide evidence that heart size is a phylogenetically conserved trait among tinamous and that the Ornate Tinamou cannot compensate aerobically for its small heart. Instead, it relies on anaerobic metabolism incurring in a large oxygen debt while exhausted. Supported by FORMAS Centre of Excellence in Animal Welfare Science and career grant from Linköpings universitet to JA.

Distribution and variation of the giant alpha anoles (Squamata: Dactyloidae) of the genus Dactyloa in the highlands of western Panama, with the description of a new species formerly referred to as D. microtus.

Six species of giant alpha anoles of the genus Dactyloa are known to occur in western Panama: Dactyloa casildae, D. frenata, D. ibanezi, D. insignis, D. kunayalae, and D. microtus. Based on own material collected along the highlands in Bocas del Toro, Chiriquf, and Veraguas provinces and the Comarca Ngöbe-Buglé of western Panama, we review their variation in morphological characters and the 16S rRNA mitochondrial gene. Our results support all six nominal taxa, but reveal considerable genetic differentiation between populations of the two highland species, D. casildae and D. microtus, respectively, from different localities. Correlated morphological differences confirm the existence of a cryptic species among populations currently assigned to D. microtus, which we describe as Dactyloa ginaelisae sp. nov. We provide point distribution maps, morphology and color descriptions, photographs in life, conservation status assessments, and an identification key for all seven species.

Australasian sky islands act as a diversity pump facilitating peripheral speciation and complex reversal from narrow endemic to widespread ecological supertramp.

The Australasian archipelago is biologically extremely diverse as a result of a highly puzzling geological and biological evolution. Unveiling the underlying mechanisms has never been more attainable as molecular phylogenetic and geological methods improve, and has become a research priority considering increasing human-mediated loss of biodiversity. However, studies of finer scaled evolutionary patterns remain rare particularly for megadiverse Melanesian biota. While oceanic islands have received some attention in the region, likewise insular mountain blocks that serve as species pumps remain understudied, even though Australasia, for example, features some of the most spectacular tropical alpine habitats in the World. Here, we sequenced almost 2 kb of mitochondrial DNA from the widespread diving beetle Rhantus suturalis from across Australasia and the Indomalayan Archipelago, including remote New Guinean highlands. Based on expert taxonomy with a multigene phylogenetic backbone study, and combining molecular phylogenetics, phylogeography, divergence time estimation, and historical demography, we recover comparably low geographic signal, but complex phylogenetic relationships and population structure within R. suturalis. Four narrowly endemic New Guinea highland species are subordinated and two populations (New Guinea, New Zealand) seem to constitute cases of ongoing speciation. We reveal repeated colonization of remote mountain chains where haplotypes out of a core clade of very widespread haplotypes syntopically might occur with well-isolated ones. These results are corroborated by a Pleistocene origin approximately 2.4 Ma ago, followed by a sudden demographic expansion 600,000 years ago that may have been initiated through climatic adaptations. This study is a snapshot of the early stages of lineage diversification by peripatric speciation in Australasia, and supports New Guinea sky islands as cradles of evolution, in line with geological evidence suggesting very recent origin of high altitudes in the region.

Phylogenetic relationships of Trachylepis skink species from Madagascar and the Seychelles (Squamata: Scincidae)

Lizards of the genus Trachylepis are a species-rich group of skinks mainly inhabiting Africa, Madagascar, and several other islands in the western Indian Ocean. All except one probably introduced species of Madagascan Trachylepis are endemic. Two species groups have been distinguished on the basis of subocular scale shape but their phylogenetic relationships remained unclear. We inferred a multilocus phylogeny of the Madagascan Trachylepis species, based on a concatenated dataset of 3261bp from 3 mitochondrial and 4 nuclear genes with a dense Madagascan taxon sampling and find high support for the monophyly of the endemic Madagascan Trachylepis. The two species groups in Madagascar are highly supported as clades. The highland species T. boettgeri is nested in the T. aureopunctata species group of mainly arid-adapted species, suggesting a colonization of highland swamps by ancestors inhabiting dry western Madagascar. The Seychellois species were sister to the T. maculilabris/T. comorensis clade, suggesting their origin directly out of Africa as with Seychellois chameleons. In Madagascar, a high intraspecific molecular variation was confirmed for T. gravenhorstii, T. elegans, and T. vato, indicating a need for taxonomic revision.

Comparative germination ecology of two altitudinal vicariant Saxifraga species endemic to the north of Spain

Seeds of high-mountain species are thought to germinate rapidly, synchronously and at high percentages after a cold period, with limited dependence on the external environment; yet, empirical evidence only partially supports this behaviour. We performed a comparative study of the germination response of two closely related taxa along an altitude gradient in northern Spain. Seeds from several maternal families of six populations of Saxifraga trifurcata (lowland species) and S.canaliculata (highland species) were subjected to temperature and stratification treatments. Germination percentages and germination rates were analysed using generalised linear mixed modelling and accelerated failure-time modelling. We found that germination percentages and germination rates were high and dependent on incubation temperature in both species. Within species, seeds from higher altitudes had higher germination percentages under all conditions. Cold-wet stratification negatively affected germination success, particularly in the lowland species. Overall, the highland species was less responsive to the experimental treatments and showed more synchronous germination patterns. We conclude that seeds from these two Saxifraga species germinate as efficiently as species from other habitats, but have a narrower germination response, probably due to the stronger selective pressures in their harsh environments. Finally, a cold, wet stratification period is not a prerequisite for the germination of high-mountain S.canaliculata, and its strong negative effect on the germination of its lowland relative S.trifurcata may contribute to the altitudinal segregation of these two species.

Stream Conductivity: Relationships to Land Use, Chloride, and Fishes in Maryland Streams

AbstractStream conductivity reflects both landscape and anthropogenic interactions, although increasing chloride inputs from road salt in eastern North America is also important. Employing a spatially extensive database derived from the Maryland Biological Stream Survey (MBSS), we examined relationships of stream conductivity to landscape attributes and determined relationships between stream MBSS fish metrics, abundance, and biomass as well as fish assemblages by means of conductivity (as a chloride surrogate) to estimate potential effects. Background stream conductivity for the MBSS strata and Maryland L3 ecoregions ranged from 51 to 150 μS/cm, with the Piedmont having the highest background conductivity (145–160 μS/cm). For MBSS sites there were strong relationships of stream conductivity and chloride with both impervious surface and road density, and 0.26% of the MBSS sites exceeded the U.S. Environmental Protection Agency's acute chloride criterion and 1.5% the chronic chloride criterion. For the Maryland Piedmont species assemblage, observed conductivity values between 230 and 540 μS/cm caused important alterations in the biotic community as measured by the series of fish metrics, and thus affected fish species assemblages associated with chloride concentrations between 33 and 108 mg/L. Maryland coastal, coldwater, and highland species assemblages displayed variable responses of conductivity to fish metrics, abundance, and biomass. If regional conductivity and chloride levels continue to increase or remain high from road deicing owing to an increase in urbanization in a watershed or climatic changes, differences in stream fish assemblages and therefore fish diversity may become more apparent. Because of the linkage between salt usage and impervious road surfaces resulting from urbanization, it is important to manage effectively the use of road salt to protect biotic resources.Received January 24, 2012; accepted June 5, 2012

The influence of riverine barriers on phylogeographic patterns of Malagasy reed frogs (Heterixalus)

We analyzed the influence of large rivers on the phylogeography of endemic widespread amphibians along Madagascar’s east coast, using as models various species and species complexes of Malagasy reed frogs (Heterixalus spp.) that are specialized to either highland or lowland habitats. We assembled a dense sampling across the full species ranges and used mitochondrial (cob) as well as nuclear (Rag-1) DNA sequences to assess their phylogeographies. A multigene mtDNA phylogeny of each species was constructed to establish the relationships among the main phylogroups, in order to understand the geographical regions of clade origins and possible directions of historical range expansions. Distinct intraspecific lineages as diagnosed by mitochondrial haplotype clades were found in highlands and lowlands. Most geographical boundaries among these phylogroups did not coincide with rivers, indicating that the influence of rivers on the primary divergence of phylogroups is probably minor in these frogs. Nevertheless, we found evidence for the influence of one riverine barrier in the lowland species complex, where the most important genetic discontinuity (the border between Heterixalus madagascariensis and H. alboguttatus) coincides with the geographical position of the Mangoro River on Madagascar’s central east coast. Analyses of the highland species H. betsileo revealed the existence of six deep haplotype lineages, separated in two major subpopulations which differ largely in altitudinal distribution and do not overlap with the geographical settings of rivers in the highlands. Furthermore, our analyses indicated that most of the major intraspecific lineages of reed frogs show signs of a rather recent population expansion.

ANCIENT TEPUI SUMMITS HARBOR YOUNG RATHER THAN OLD LINEAGES OF ENDEMIC FROGS

The flattop mountains (tepuis) of South America are ancient remnants of the Precambrian Guiana Shield plateau. The tepui summits, isolated by their surrounding cliffs that can be up to 1000 m tall, are thought of as "islands in the sky," harboring relict flora and fauna that underwent vicariant speciation due to plateau fragmentation. High endemicity atop tepui summits support the idea of an ancient "Lost World" biota. However, recent work suggests that dispersal between lowlands and summits has occurred long after tepui formation indicating that tepui summits may not be as isolated from the lowlands as researchers have long suggested. Neither view of the origin of the tepui biota (i.e., ancient vicariance vs. recent dispersal) has strong empirical support owing to a lack of studies. We test diversification hypotheses of the Guiana Shield highlands by estimating divergence times of an endemic group of treefrogs, Tepuihyla. We find that diversification of this group does not support an ancient origin for this taxon; instead, divergence times among the highland species are 2-5 Ma. Our data indicate that most highland speciation occurred during the Pliocene. Thus, this unparalleled landscape known as "The Lost World" is inhabited, in part, not by Early Tertiary relicts but neoendemics.

Phylogeny of woodcreepers of the genusLepidocolaptes(Aves, Furnariidae), a widespread Neotropical taxon

Arbeláez‐Cortés, E., Navarro‐Sigüenza, A. G. & García‐Moreno J. (2012). Phylogeny of woodcreepers of the genusLepidocolaptes(Aves, Furnariidae), a widespread Neotropical taxon. —Zoologica Scripta,41, 363–373.Phylogeny of woodcreepers of the genusLepidocolaptes(Aves, Furnariidae), a widespread Neotropical taxon. The phylogeny of the genusLepidocolapteswas reconstructed based on three mitochondrial DNA regions and one nuclear DNA intron, using Bayesian analysis. A general pattern of diversification among the lowland species followed by the diversification of highland species, and a close relationship among montane species with the two Atlantic Forest endemics, seem to depict the history of this genus. Results also showed that the two Mesoamerican species are sister‐taxa with high support. Finally, our data also suggest the existence of previously unknown intraspecific genetic structure within some taxa, especially among populations ofLepidocolaptes souleyetii.

Evidence for a Trade-Off Strategy in Stone Oak (Lithocarpus) Seeds between Physical and Chemical Defense Highlights Fiber as an Important Antifeedant

Trees in the beech or oak family (Fagaceae) have a mutualistic relationship with scatter-hoarding rodents. Rodents obtain nutrients and energy by consuming seeds, while providing seed dispersal for the tree by allowing some cached seeds to germinate. Seed predation and caching behavior of rodents is primarily affected by seed size, mechanical protection, macronutrient content, and chemical antifeedants. To enhance seed dispersal, trees must optimize trade-offs in investment between macronutrients and antifeedants. Here, we examine this important chemical balance in the seeds of tropical stone oak species with two substantially different fruit morphologies. These two distinct fruit morphologies in Lithocarpus differ in the degree of mechanical protection of the seed. For ‘acorn’ fruit, a thin exocarp forms a shell around the seed while for ‘enclosed receptacle’ (ER) fruit, the seed is embedded in a woody receptacle. We compared the chemical composition of numerous macronutrient and antifeedant in seeds from several Lithocarpus species, focusing on two pairs of sympatric species with different fruit morphologies. We found that macronutrients, particularly total non-structural carbohydrate, was more concentrated in seeds of ER fruits while antifeedants, primarily fibers, were more concentrated in seeds of acorn fruits. The trade-off in these two major chemical components was more evident between the two sympatric lowland species than between two highland species. Surprisingly, no significant difference in overall tannin concentrations in the seeds was observed between the two fruit morphologies. Instead, the major trade-off between macronutrients and antifeedants involved indigestible fibers. Future studies of this complex mutualism should carefully consider the role of indigestible fibers in the foraging behavior of scatter-hoarding rodents.

Population genetic structure of a specialist leafhopper on Zea: likely anthropogenic and ecological determinants of gene flow

AbstractCorn leafhopper, Dalbulus maidis DeLong & Wolcott (Hemiptera: Cicadellidae), is a specialist herbivore on the genus Zea (Poaceae). The genera Dalbulus and Zea evolved in central Mexico. We sought to determine whether population genetic structuring is prevalent in corn leafhoppers inhabiting three of its host plants: (1) the highland species perennial teosinte (Zea diploperennis Iltis, Doebley & Guzman), (2) the mid‐ to lowland‐species Balsas teosinte (Zea mays ssp. parviglumis Iltis & Doebley), and (3) the ubiquitous domesticated maize (Zea mays ssp. mays L.). We used amplified fragment length polymorphisms to detect population structuring and genetic differentiation among corn leafhoppers on the three host plants in western‐central and ‐northern Mexico. Our results showed that corn leafhopper in Mexico is composed of at least two genetically discrete populations: an ‘Itinerant’ population associated with the annual hosts maize and Balsas teosinte, which appears to be widely distributed in Mexico, and a ‘Las Joyas’ population restricted to perennial teosinte and confined to a small mountain range (Sierra de Manantlán) in western‐central Mexico. Our results further suggested that population structuring is not due to isolation by distance or landscape features: Las Joyas and Itinerant corn leafhopper populations are genetically distinct despite their geographic proximity (ca. 4 km), whereas Itinerant corn leafhoppers separated by hundreds of kilometers (>800 km), mountain ranges, and a maritime corridor (Sea of Cortez) are not genetically distinct. Based on our results and on published ethnohistorical and archaeological data, we propose pre‐Columbian and modern scenarios, including likely ecological and anthropogenic influences, in which the observed genetic population structuring of corn leafhopper could have originated and could be maintained. Also, we hypothesize that after evolving on the lowland Balsas teosinte, corn leafhopper expanded its host range to include maize and then the highland perennial teosinte, following the domestication and spread of maize within the last 9 000 years.

Padrões de distribuição geográfica das espécies de Chamaecrista sect. Chamaecrista ser. Coriaceae (Benth.) H. S. Irwin & Barneby, Leguminosae - Caesalpinioideae

An analysis of the geographic distribution of the 27 taxa belonging to 20 species of Chamaecrista sect. Chamaecrista ser. Coriaceae was carried out, based on maps depicting the known occurrences of the taxa. One species occurs in the Caribbean region, C. caribaea (Northr.) Britton, whereas the others are distributed in a main center of diversity, the Espinhaco Range, presenting two main patterns: 1) a continuous to disjunct occurrence through the Espinhaco Range and adjacent or disjunct areas, and 2) an endemic distribution in the southern region of that mountain range. Among the disjunctions, three species are noteworthy: one occurring in the Espinhaco and elevations of the Arco de Brasilia westwards Goias (C. cardiostegia H. S. Irwin & Barneby), other in the Espinhaco and in Espirito Santo State (C. mucronata (C. Sprengel) H. S. Irwin & Barneby), and a third one centered in the Espinhaco and in the Guyana Shield (C. roraimae (Benth.) Gleason). The distribution patterns are discussed, mainly as compared to data from other groups of angiosperms, and to a previous analysis of five species belonging to C. ser. Coriaceae. The results show a concentration of endemic species in highlands in the Cerrado Domain. They give additional support to the high degree of endemism already documented for other groups in the region. This analysis is an initial step allowing further studies to understand the processes responsible for the diversification of the group in the cerrado, specially in elevated areas.

Comments on Point:Counterpoint: High altitude is/is not for the birds!

TO THE EDITOR: The debate between Scott et al. (6) and Llanos et al. (4) highlights the remarkable ability of birds and mammals to adapt and survive at high altitudes and cope with reduced oxygen (O2) availability. Scott and colleagues (6) make a compelling argument that birds are far superior to mammals at adapting and thriving in hypoxic environments, both at rest and during exercise. While their argument is supported by comparisons between birds and terrestrial mammals, it ignores marine mammals. Marine mammals such as seals are routinely exposed to and tolerate long bouts of hypoxia during breath-hold diving. For example, elephant seals may dive to depths of nearly 1,600 m and occasionally remain submerged for 2 h (3). Moreover, marine mammals can be exposed to partial pressures of arterial oxygen (PaO2) as low as 12 mmHg during free dives (5), which is less than the 20 mmHg observed in the bar-headed goose (6). Interestingly, a PaO2 of 12 mmHg observed in elephant seals corresponds to arterial saturations and O2 content of only 8% and 2.7 ml O2/dl (5). Thus marine mammals such as the elephant seal demonstrate a remarkable hypoxia tolerance. The integration of several key physiological adaptations including 1) substantially greater myoglobin concentrations compared to other mammals, 2) reductions in metabolism, 3) a greater reliance on aerobic metabolism (i.e., less lactate production), 4) a host of dramatic acute cardiovascular adjustments; and 5) an increased intrinsic cerebral hypoxia tolerance allow marine mammals to thrive in hypoxic environments and enable long deep dives (1–3).