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opencc-zeroMay 2020View details →

Data from: Fire and grazing controlling a tropical tree line: Effects of long‐term grazing exclusion in Bale Mountains, Ethiopia

Aims: Tropical tree lines are often associated with abrupt shifts in vegetation, soils and disturbance regimes, but the underlying mechanisms are poorly understood. We analysed the role of grazing, fuels and fire in maintaining a sharp tree line with flammable heathland above non-flammable forest. Location: Bale Mountains, Ethiopia. Methods: Grazing exclosures, repeated vegetation sampling, soil analyses and burning and sowing experiments along an altitudinal gradient with Hagenia abyssinica forest, Erica trimera forest and Erica heathland; all heavily grazed, the latter burnt on short rotation. Results: Contrary to expectation, livestock exclusion did not increase forest fuel flammability, but instead resulted in a dense carpet of non-flammable herbs. In the heathland, livestock exclusion led to somewhat faster post-fire fuel recovery, but no major vegetation change. Seeding of tree species resulted in some seedling establishment, but notably Hagenia grew poorly in the heathland, even when protected from livestock. A bioassay, as well as observations of outpost trees on atypical soil above the treeline, suggest that this poor growth is caused by the acidic soils, rather than harsh climate. Despite frequent fires, heathland soils had lower pH and higher organic matter content than forest soils. Below the tree line, tree seedling establishment was successful only in forest gaps, and if livestock was excluded. In both forest and heathland rapid vegetative regeneration in the ground flora after disturbance restricted major species shifts. Conclusions: These results suggest that the contrasting fire potential between heathland and forest, and thus the sharp tree line would be maintained, or possibly even accentuated, in the absence of livestock grazing, and that Hagenia colonisation upwards into the heathland is restricted not only by fire and grazing, but also the acidic soils, a legacy of centuries of Erica dominance.

opencc-zeroDec 2018View details →

Data from: Differences in carbon stocks along an elevational gradient in tropical mountain forests of Colombia

Tropical mountain forests provide an exceptional opportunity to evaluate the patterns of variation of carbon stocks along elevational gradients that correspond to well-defined temperature gradients. We predicted that carbon stored in live aboveground biomass, aboveground necromass, and soil components of forests on the eastern flank of the Colombian Andes would change with elevation along this gradient extending from 750 to 2800 m above sea level. The rationale was that the corresponding change in temperature (14°C to 26°C) would influence tree growth and decomposition of organic matter. To address this hypothesis, we examined the carbon stored in these three components using data from 20 0.25-ha plots located along this elevational gradient. The mean total carbon stock found in the study region was 241.3±37.5 Mg C/ha. Aboveground carbon stocks decreased with elevation (p =0.001), as did necromass carbon stocks (p =0.016). Although soil organic carbon stocks did not differ significantly along the gradient (p =0.153), they contributed proportionately more at higher than at lower elevations, counterbalancing the opposite trends in aboveground carbon and necromass carbon stocks. As such, total carbon stocks did not vary significantly along the elevational gradient (p =0.576).

opencc-zeroNov 2020View details →

Data from: Elevation and leaf litter interact in determining the structure of ant communities on a tropical mountain

Tropical mountains encompass a wide range of environmental conditions and are useful models for studying drivers of community structure. Invertebrate species richness and abundance show various elevational patterns. However, the drivers of these differences are not well understood, although microhabitat complexity is potentially important. We studied ground-dwelling ants using pitfall trapping and hand collection on Mt. Wilhelm (Papua New Guinea) from 169 to 3,795 m a.s.l. We tested for the effects of elevation and leaf litter depth (as a measure of microhabitat complexity) on ant abundance, species richness and composition. We sampled 118 species, with ants present up to 2,331 m a.s.l. Species richness peaked at mid-elevation (~700 m), but the elevational pattern for abundance varied depending on sampling scale. Leaf litter depth negatively affected abundance once elevation had been accounted for, while elevation and litter depth had an interactive effect on species richness. Species richness was positively related to litter depth at lower elevations, but negatively above ~700 m. Species composition varied with elevation and less strongly with leaf litter depth. We speculate that in the lowlands, litter depth rather than temperature limits ant communities. At high elevations, the deeper litter decreases temperature of the litter layer, and temperature becomes limiting. At mid elevations, temperature is not yet too low, and litter is still relatively deep, hence generating a mid-elevation peak in ant richness. Our results may explain differing richness-elevation patterns of litter arthropods around the world, and provide testable predictions for future studies on this topic.

opencc-zeroDec 2020View details →

Data from: Changes in seed predation along a 2300-m elevational gradient on a tropical mountain in Myanmar: a standardized test with 32 non-native plant species

It has been hypothesized that biotic interactions are stronger towards lower latitudes and elevations. However, results vary among interaction systems and experimental protocols. Our goal was to examine the validity of this prediction by using a standardized method to investigate seed–animal interaction. We assessed removal by animals for 40960 seeds belonging to 32 non-native tree species along an elevation gradient from 600 m to 2910 m on Mount Victoria (Nat Ma Taung), western Myanmar. We analyzed the elevational trends of seed removal at both individual seed level (probability of depot encounter, proportion of seeds removed after encounter and total proportion of seeds removed) and community level (Shannon diversity and species evenness indices). The dry and wet seasons had opposite relationships between seed removal and elevation, i.e. hump-shaped in the dry season and U-shaped in the wet season. Individual plant species displayed almost all possible patterns: U-shaped and hump-shaped, monotonic decrease and increase, and elevation-independent patterns. As a consequence of the hump-shaped seed removal pattern with elevation in the dry season, the diversity and evenness of surviving seeds showed U-shaped patterns. Our study shows that elevational trends in seed–animal interactions do not follow a constant rule, but differ between seasons and among species, suggesting that a one-off survey with few species might give misleading information on overall macroecological patterns. Future studies of trends in biotic interactions along gradients should bear this in mind.

opencc-zeroDec 2016View details →

Data from: Tropical tree species diversity in a mountain system in southern Mexico: local and regional patterns and determinant factors

Mechanisms explaining patterns of biodiversity along elevation gradients in tropical mountain systems remain controversial. We use a set of climatic, topographic and soil variables encompassing regional, landscape and local-level spatial scales to explain the spatial variation of tree species diversity in the Sierra Madre of Chiapas, Mexico. We sampled 128 circular plots (0.1-ha each) in four elevational bands along four elevation gradients or transects encompassing 100-2200 m. A total of 12,533 trees belonging to 444 species were recorded. Diversity patterns along the elevation gradient and the explanatory power of independent variables were dependent on spatial scale (regional vs transect) and functional group (total vs late-successional or pioneer species). Diversity of all species and late-successional species (1 - proportion of pioneer species) showed a constant pattern at the regional and transect scales, with low predictive power of climatic variables and/or elevation. A linear decrease of either number or proportion of pioneer species diversity was observed with increasing elevation, which was correlated with temperature, rainfall, and human disturbance trends. Total species diversity showed an increase with rainfall of the warmest quarter, indicating a regional-level limiting effect of seasonality (drought duration). Yet the explanatory power of climatic and topographic variables was higher at the individual transect level than at the regional scale, suggesting the parallel but differential influence of evolutionary and geological history factors on diversification not so far studied to explain elevation patterns of species diversity in tropical mountain systems.

opencc-zeroDec 2018View details →

Data from: Traits that allow bats of tropical lowland origin to conquer mountains: bat assemblages along elevational gradients in the South American Atlantic Forest

Aim: This study aims to contribute to the identification of ecological determinants of tropical moist forest montane biodiversity, analyzing changes in the structure of bat assemblages along an elevational gradient and testing the role of species traits shaping those assemblages. Location: Mountain ranges in the Brazilian Atlantic Forest. Methods: We compiled a dataset with the composition of phyllostomid bat assemblages at 32 forested sites, ranging from 60m to 1960m a.s.l. We quantified how abundance and diversity changed along this elevational gradient, and assessed the capacity of each species to be present and abundant at each elevation, identifying traits that may influence that capacity. Results: Abundance and species diversity declined markedly with increasing elevation. Tolerance to low temperatures, low habitat specialization, and cave roosting facilitated success at higher elevations. Owing to trait filtering, and to changes in resource availability with elevation, assemblages were progressively dominated by a smaller number of mostly generalist species as elevation increased. Higher elevations harbor only a subset of the species that are present in the lowland forest, with no mountain specialized species. Main conclusions: High mountains harbor phyllostomid assemblages that are impoverished subsets of those at lower elevations. Phyllostomids have a tropical origin and may thus have a low potential to adapt to montane forest environments, which possibly explains the observed climatic trait filtering. Habitat filtering is also important, keeping forest specialists mostly at lowest elevations. Protected areas in the Atlantic Forest are mostly limited to mountains. While these areas are clearly important to protect biodiversity, including phyllostomid assemblages, it is now critical to protect and restore the few remnants of lower elevation Atlantic Forest where higher productivity and resource levels, increased complexity of vertical structure, and fewer climatic constraints favor the success of a wider range of phyllostomid bat species of tropical origin.

opencc-zeroDec 2012View details →

Data from: Delimiting tropical mountain ecoregions for conservation

Ecological regions aggregate habitats with similar biophysical characteristics within well-defined boundaries, providing spatially consistent platforms for monitoring, managing and forecasting the health of interrelated ecosystems. A major obstacle to the implementation of this approach is imprecise and inconsistent boundary placement. For globally important mountain regions such as the Eastern Arc (Tanzania and Kenya), where qualitative definitions of biophysical affinity are well established, rule-based methods for landform classification provide a straightforward solution to ambiguities in region extent. The method presented in this paper encompasses the majority of both contemporary and estimated preclearance forest cover within strict topographical limits. Many of the species here tentatively considered 'near-endemic' could be reclassified as strictly endemic according to the derived boundaries. LandScan and census data show population density inside the ecoregion to be higher than in rural lowlands, and lowland settlement to be most probable within 30 km. This definition should help to align landscape scale conservation strategies in the Eastern Arc and promote new research in areas of predicted, but as yet undocumented, biological importance. Similar methods could work well in other regions where mountain extent is poorly resolved. Spatial data accompany the online version of this article.

opencc-zeroDec 2016View details →

Data from: Evolution of woody life form on tropical mountains in the tribe Spermacoceae (Rubiaceae)

Spermacoceae are mainly an herbaceous group in the Rubiaceae. However, a few lineages are woody, and are found in a diverse range of habitat types. Three of the largest woody lineages (Arcytophyllum, Hedyotis, and Kadua) are characterized by their distribution in the moist tropical mountains, and have disjunct distribution patterns with respect to their closest relatives. In this study, we explore the cases of derived woodiness in these three lineages and their diversification dynamics in the tropical mountains of Asia, the Pacific, and the Americas. By combining phylogenetic results with wood anatomical studies, we estimated timing of origin of the three woody groups, inferred their ancestral traits and ancestral distribution ranges, analyzed their associations with the tropical upland habitat, and elucidated their diversification across tropical mountains. The three woody clades originated and diversified from herbaceous ancestors in close association with the tropical upland habitat during the Miocene. The ancestral range for Asian-Pacific Hedyotis and Pacific Kadua is Africa/Madagascar and continental Asia respectively. The complex geological history of tropical Asia allowed Hedyotis to diversify faster and create narrow endemics near oceans in the highlands of Western Ghats (India), Sri Lanka, Southeast Asia including southeastern China, and New Guinea. The three major woody clades in Spermacoceae have gained their woodiness independently from one another, subsequent to colonization by their ancestors from a different geographic environment. The evolution and diversification along the tropical mountain orogeny is strongly linked with the formation of woody habit and many narrow endemic species.

FIGURE 10 in Archaeococcoid scale insects (Hemiptera: Coccoidea) from the tropical high mountains of the Andean Cordillera, South America

FIGURE 10. Adult female of Platycoelostoma rauppi Foldi n. sp. Where: A = apical segment of antenna; B = triangular multilocular pore with trilocular centre; C = flagellate seta; D = hair-like seta; E = broadly oval multilocular pore with bilocular centre; F = abdominal spiracles; G = anal tube; H = simple tubular pore; I = spinules; J = metathoracic leg; K = longest hair-like setae near coxae; L = thoracic spiracle; M = multilocular pore with quadrilocular centre; N = small multilocular pore with triangular shaped outer loculi.

FIGURE 7 in Archaeococcoid scale insects (Hemiptera: Coccoidea) from the tropical high mountains of the Andean Cordillera, South America

FIGURE 7. Third-instar female of Paramoandesia ecuadorensis Foldi n. sp. Where: A = antenna; B = dorsal hair; C = multilocular pore with oval centre; D = mosaic-like structure on intersegmantal membrane: E = stout hair-like seta; F = multilocular pore with quadrate centre; G = hair on abdomen; H = dorsal and perispiracular broadly oval multilocular pore; I = minute circular pore with irregular opening; J = anal tube; K = abdominal spiracle with pores H+I; L = flagellate seta; M = hair-like seta; N = multilocular pore with 5 central loculi; O = metathoracic leg with claw; P = multilocular pore with triangular centre; Q = thoracic spiracle with enlargement of pores H + I; R = spinules.

FIGURE 4 in Archaeococcoid scale insects (Hemiptera: Coccoidea) from the tropical high mountains of the Andean Cordillera, South America

FIGURE 4. Adult female of Paramoandesia colombiensis Foldi n. sp. Where: A = multilocular pore with oval centre; B + C = straight and curved dorsal and ventral hairs; D = hair-like seta; E = flagellate seta; F = dorsal and ventral multilocular pores with triangular centre; G = abdominal spiracle; H = short spiniform setae with strongly enlarged base; I = polygonal patch on intersegmental membrane; J = claw; K = thoracic spiracle; L = multilocular pore with quadrate centre, M = sensory organs on antennal intersegmental membrane. N = spinules.

FIGURE 2 in Archaeococcoid scale insects (Hemiptera: Coccoidea) from the tropical high mountains of the Andean Cordillera, South America

FIGURE 2. Adult female of Crypticerya abrahami (Newstead). Where: A = pore with 2 large central loculi and 4 small elongated outer loculi; B = antenna; C = small convex pores and minute setae at base of scape; D = multilocular pore with 4 large central loculi and 12 small outer loculi; E = hair-like setae; F = pore with 3 large central loculi and 6 small outer loculi; G = anal tube; H = cicatrix; I = abdominal spiracle; J = long collared seta on submargin; K = multilocular pore around anal area; L = broadly oval multilocular pore; M = metathoracic leg; N = campaniform sensillum on trochanter; O = thoracic spiracle with enlargement of perispiracular pore (pp); P = pore with Y-shaped opening and an irregular rim. R = multilocular pores with a central ductule around vulvar opening; S = flagellate seta; T = hair.

FIGURE 3 in Archaeococcoid scale insects (Hemiptera: Coccoidea) from the tropical high mountains of the Andean Cordillera, South America

FIGURE 3. First-intar nymph of Crypticerya abrahami (Newstead). Where: A = prothoracic leg; B = thoracic spiracle; C = dorsal hexagonal multilocular pore; D = anal tube; E + F = multilocular pores and polygonal wax pores at inner end of anal tube; G = multilocular pore on dorsum and venter; H = quadrilocular pore on venter; I = posteroventral circular cicatrix; J = 3 pairs of long caudal setae, median pair represent shorter collared setae; K = dorsal hair-like setae; L = collared setae on margin; M = antenna; N = eye; O = hair-like setae on margin.

FIGURE 6 in Archaeococcoid scale insects (Hemiptera: Coccoidea) from the tropical high mountains of the Andean Cordillera, South America

FIGURE 6. Adult female of Paramoandesia ecuadorensis Foldi n. sp. Where: A = antenna; B = multilocular pore with oval centre; C = dorsal hair; D = flagellate seta; E = dorsal multilocular pore with quadrate centre; F = multilocular pore with triangular centre; G = hair on abdomen; H = minute circular pore with irregular opening; I = marginal hair-like seta; J = abdominal spiracle with atrial pores; K = multilocular pore with quadrate centre surrounding vulvar opening; L = mosaic-like structure on intersegmantal membrane; M = metathoracic claw; N = thoracic spiracles with perispiracular pores.

FIGURE 1 in Archaeococcoid scale insects (Hemiptera: Coccoidea) from the tropical high mountains of the Andean Cordillera, South America

FIGURE 1. Adult female of Corandesia kozári Foldi n. sp. Where: A = apical antennal segment; B = straight and curved stout spiniform setae; C = multilocular pore with oval centre; D = dorsal hair; E = hair-like seta; F = multilocular pores with large triangular outer loculi; G = anal tube; H = long hair-like seta; I = cicatrices; J = multilocular pore with triangular centre; K = abdominal spiracle; L = sclerotised dermal plates; M = spinules; N = multilocular pore with triangular centre; O = flagellate seta; P = thoracic spiracle with atrial pores; R = multilocular pore with six elongated narrow outer loculi and trilocular centre.

FIGURE 9 in Archaeococcoid scale insects (Hemiptera: Coccoidea) from the tropical high mountains of the Andean Cordillera, South America

FIGURE 9. Preadult female of Mimosicerya williamsi Foldi n. sp. Where: A = raised pore; B = hair-like seta; C = stout conical spine; D = antenna; E = short spiniform seta; F = slender flagellate seta; G = hair; H = multilocular pore with quadrate centre; J = anal tube with polygonal wax pores (K) and multilocular pore with triangular centre (L); M = raised pore; O = abdominal spiracle with minute spiniform setae (N), plus cruciform pore (P) and multilocular pore (R); S = multilocular pore with triangular centre; T = spinules; U = tubular pore; V = cicatrix; W = tibia+ tarsus + claw of metathoracic leg; X = long hair with swollen apex on thorax; Y = stout conical spine; Z = thoracic spiracle with enlargement of simple pores and multilocular pores near peritreme.

FIGURE 8 in Archaeococcoid scale insects (Hemiptera: Coccoidea) from the tropical high mountains of the Andean Cordillera, South America

FIGURE 8. Adult female of Mimosicerya williamsi Foldi n. sp. Where: A = detail of sclerotised area; B = multilocular pore with triangular centre with 3 loculi and 10 triangular shaped outer loculi; C = multilocular pore with oval centre in the sclerotised area; D = spiniform setae from dorsum and venter; E = hair-like seta; F = flagellate seta; G = multilocular pores on dorsum and venter: H = slender hair-like seta; I = abdominal spiracle; J = anal tube; K = stout hair-like seta; L = hair; M = long hair-like setae medially; N = vestigial metathoracic leg; O = mesothoracic spiracle with perispiracular pores; P= antenna; R = conical spiniform seta.