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opencc-zeroDec 2018View details →

Data from: Increasing dependence of lowland populations on mountain water resources

Mountain areas provide disproportionally high runoff in many parts of the world, and here we quantify for the first time their importance for water resources and food production from the viewpoint of the lowland areas downstream. The dataset maps the degree to which lowland areas potentially depend on runoff contributions from mountain areas (39% of land mass) between the 1960s and the 2040s.

opencc-zeroAug 2020View details →

Data from: Mechanisms for the development of microform patterns in peatlands of the Hudson Bay Lowland

Spatial surface patterns of hummocks, hollows, ridges, and pools (microtopography) are common features of many northern peatlands and are particularly distinct within the vast peatlands of the Hudson Bay Lowland (HBL), Canada. Hypotheses and models describe how small-scale feedbacks among vegetation, hydrology, and nutrients cause spatial differences in peat accumulation that enable microforms and surface patterns to develop over time. Empirical tests of the predictions from theoretical models of these proposed feedback mechanisms are limited, particularly in large peatland complexes such as the HBL. We investigate feedbacks controlling peatland structure and function in an ombrogenous bog and a minerogenous fen in the HBL. Our sites represent surface patterns found in many northern peatlands, specifically spatially irregular hummocks and hollows, and parallel ridges and pools that are perpendicular to slope. We found the occurrence of different spatial patterns depends on position within a peat landform, with these differences attributed to the ecohydrological setting. In turn, the ecohydrological setting, with different water table depths, nutrient availability, and species composition, influences the strength and direction of feedback mechanisms at the microform scale. Our data support the prediction of a positive feedback between plant productivity and acrotelm thickness for peat accumulation and hummock growth, and that this may be enhanced by water ponding on slopes to form ridge-pool tracks. We did not find evidence to support the proposed feedback among evapotranspiration (ET)-driven transport of water and nutrients for the development of hummocks. Our results suggest a combination of mechanisms operating at various temporal and spatial scales are associated with the development of surface patterns in northern peatlands.

opencc-zeroAug 2020View details →

Data from: Seasonal dynamics of flock interaction networks across a human-modified landscape in lowland Amazonian rainforest

Although lowland tropical rainforests were once widely believed to be the archetype of stability, seasonal variation exists. In these environments, seasonality is defined by rainfall, leading to a predictable pattern of biotic and abiotic changes. Only the full annual cycle reveals niche breadth, yet most studies of tropical organisms ignore seasonality, thereby underestimating realized conditions. If human-modified habitats display more seasonal stress than intact habitats, then ignoring seasonality will have particularly important repercussions for conservation. We examined the seasonal dynamics of Amazonian mixed-species flocks—an important species interaction network—across three habitats with increasing human disturbance. We quantified seasonal space use, species richness and attendance, and four ecological network metrics for flocks in primary forest, small forest fragments, and regenerating secondary forest in central Amazonia. Our results indicate that, even in intact, lowland rainforest, mixed-species flocks exhibit seasonal differences. During the dry season, flocks included more species, generally ranged over larger areas, and displayed network structures that were less complex and less cohesive. We speculate that because most flocking species nest during the dry season—a time of reduced arthropod abundance—flocks are simultaneously constrained by these two competing pressures. Moreover, these seasonal differences were most pronounced in forest fragments and secondary forest, habitats that are less buffered from the changing seasons. Our results suggest that seasonality influences the conservation value of human-modified habitats, raising important questions about how rainforest organisms will cope with an increasingly unstable climate.

opencc-zeroOct 2020View details →

Patterns of speciation are similar across mountainous and lowland regions for a Neotropical plant radiation (Costaceae: Costus)

High species richness and endemism in tropical mountains are recognized as major contributors to the latitudinal diversity gradient. The processes underlying mountain speciation, however, are largely untested. The prevalence of steep ecogeographic gradients and the geographic isolation of populations by topographic features are predicted to promote speciation in mountains. We evaluate these processes in a species-rich Neotropical genus of understory herbs that range from the lowlands to montane forests and have higher species richness in topographically complex regions. We ask whether climatic niche divergence, geographic isolation, and pollination shifts differ between mountain-influenced and lowland Amazonian sister pairs inferred from a 756-gene phylogeny. Neotropical Costus ancestors diverged in Central America during a period of mountain formation in the last 3 My with later colonization of Amazonia. Although climatic divergence, geographic isolation, and pollination shifts are prevalent in general, these factors don't differ between mountain-influenced and Amazonian sister pairs. Despite higher climatic niche and species diversity in the mountains, speciation modes in Costus appear similar across regions. Thus, greater species richness in tropical mountains may reflect differences in colonization history, diversification rates, or the prevalence of rapidly evolving plant life forms, rather than differences in speciation mode.

opencc-zeroDec 2020View details →

Data from: The biotic interactions hypothesis partially explains bird species turnover along a lowland Neotropical precipitation gradient

Aim: We evaluated the influence of climate in determining bird communities along precipitation gradients. We argue that mechanisms responsible for community turnover along precipitation gradients are similar to mechanisms operating along temperature and latitudinal gradients. We test the hypothesis that environmental conditions affect community composition in dry forests, whereas biotic interactions affect community composition in wet forests. Location: Low-elevation forests along a precipitation gradient in Colombia where precipitation ranges from 700 – 4000 mm annually but elevation and temperature remain constant. Time period: Present day Major Taxa Studied: Tropical Forest Birds. Methods: We performed 291 bird counts in nine study areas across the ~3000 mm precipitation range. In each locality we obtained climatic characteristics, and a phylogenetic, morphological and physiological proxy data set to test predictions about the evolutionary relationships and distribution of traits. Results: Bird communities changed abruptly along the precipitation gradient and could be divided into dry and wet forest communities. Analyses of phylogenetic relationships, trait space, and observations at nests suggested that environmental filtering is more important in dry forest, especially for breeding. In contrast, we found little evidence that competition was more important in wet forest. Nest predation or competition for nest space, however, may be more critical in wetter forests. Conclusions: The two distinct bird communities we documented suggest that lowland precipitation gradients, where temperature is constant, can be as important as temperature gradients in generating high beta diversity. We conclude that the breeding process in bird communities might be crucial for determining community assembly along environmental gradients. Given that recent population declines in tropical birds have been attributed to changes in precipitation, by understanding the mechanisms underlying community assembly along precipitation gradients our study may improve our ability to understand those declines and predict the effects of climate change on neotropical avifauna.

opencc-zeroDec 2020View details →

Drought sensitivity of Empetrum nigrum shrub growth at the species' southern lowland distribution range margin

The ongoing warming of the Earth's atmosphere is projected to cause a northward shift of species' distributions, as they track their climatic optimum. In the rapidly warming Arctic, this has already led to an increase of shrubs in tundra ecosystems. While this northern expansion of woody biomass has been studied relatively extensively over the last decade, little research has been devoted to shrub growth responses at the southern margins of Northern Hemisphere shrubs. Here, we studied shoot length growth, its responses to climate over the period 2010-2017, and differences in leaf C and N content of the evergreen dwarf shrub Empetrum nigrum, as well as the vegetation composition and soil parameters at four sites located along a gradient of increasing dune age on the island Spiekeroog, northern Germany. The sites are located in the tri-national UNESCO world heritage site, the Wadden Sea. E. nigrum has a predominantly circum-arctic-boreal distribution and its southern distribution mbargin in European lowlands runs through northern Germany, where it is retreating northwards. We found a negative response to autumn (surface) temperatures and previous summer surface temperatures and/or a positive response to summer precipitation of E. nigrum growth, except at the oldest dune with the strongest E. nigrum dominance. Growth rates and plant species diversity declined with dune age. Our results suggest that E. nigrum growth is drought sensitive at its European southern range margin. We hypothesize that this sensitivity may form the basis for its northward retreat, which is supported by recent observations of E. nigrum dieback in Germany after the extreme drought in 2018 and model projections.

FIGURE 20 in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 20. Maximum likelihood phylogenetic trees (1,000 replicates) demonstrating the relationship of the novel taxa, Tico emmettcarri gen. et. sp. n. and Tico pseudosororius gen. et. sp. n. relative to other genera within the Cenchreini based on the; (A) 18S gene, (B) COI gene, and (C) consensus tree of combine 18S and COI data; scale bar = percent nucleotide difference.

FIGURE 19 in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 19. Female genitalia of Tico gen. n. pseudosororius sp. n.; A) pregenital plate ventral view and B) first gonapophysis of ovipositor.

FIGURE 18 in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 18. Illustration of aedeagus of adult male Tico gen. n. pseudosororius sp. n.; A) right lateral view, B) left lateral view, and C) dorsal view.

FIGURE 17 in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 17. Aedeagus of adult male Tico gen. n. pseudosororius sp. n.; A) right lateral view, B) left lateral view, and C) dorsal view.

FIGURE 16 in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 16. Gonostylus of Tico gen. n. pseudosororius sp. n.; A) lateral view demonstrating dorsal process and B) inner surface demonstrating sclerotized ridge with trifid process.

FIGURE 15. Male Tico gen. n in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 15. Male Tico gen. n. pseudosororius sp. n. terminalia; A) lateral view, B) ventral view, and C) dorsal view.

FIGURE 8 in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 8. Gonostylus of Tico gen. n. emmettcarri sp. n.; A) lateral view demonstrating ventral-angular projection and dorsal process and B) inner surface demonstrating sclerotized ridge with tubercles and spinose apex.

FIGURE 13. Adult Tico gen. n in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 13. Adult Tico gen. n. pseudosororius sp. n.; A) head and pronotum frontal view, B) head, pronotum, and mesonotum dorsal view, and C) head, pronotum, and mesonotum lateral view, scale = 1 mm.

FIGURE 4. Adult habitus Tico gen. n in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 4. Adult habitus Tico gen. n. emmettcarri sp. n.; A) female body lateral view, B) dorsal view, C) male body lateral view, and D) dorsal view, scale = 1 mm.

FIGURE 7. Male Tico gen. n in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 7. Male Tico gen. n. emmettcarri sp. n. terminalia; A) lateral view, B) ventral view, and C) dorsal view.

FIGURE 9 in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 9. Aedeagus of adult male Tico gen. n. emmettcarri sp. n.; A) right lateral view, B) left lateral view, and C) dorsal view.

FIGURE 5. Adult Tico gen. n in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 5. Adult Tico gen. n. emmettcarri sp. n.; A) head and pronotum frontal view, B) head, pronotum, and mesonotum dorsal view, and C) head, pronotum, and mesonotum lateral view, scale = 1 mm.

FIGURE 11 in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 11. Female genitalia of Tico gen. n. emmettcarri sp. n.; A) pregenital plate ventral view and B) first gonapophysis of ovipositor.

FIGURE 10 in A new genus and two new species of planthopper in the tribe Cenchreini (Hemiptera: Auchenorrhyncha: Derbidae) from lowland tropical rainforest in Costa Rica

FIGURE 10. Illustration of aedeagus of adult male Tico gen. n. emmettcarri sp. n.; A) right lateral view, B) left lateral view, and C) dorsal view.