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"Tropical Biology"
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Widespread Biases in Ecological and Evolutionary Studies
by
LANGE, ELIZABETH C.
,
TRAVIS, JOSEPH
,
HOOKS, ALEXANDRA P.
in
Bias
,
Ecological effects
,
Ecology
2019
There has been widespread discussion of biases in the sciences. The extent of most forms of bias has scarcely been confronted with rigorous data. In the present article, we evaluated the potential for geographic, taxonomic, and citation biases in publications between temperate and tropical systems for nine broad topics in ecology and evolutionary biology. Across 1,800 papers sampled from 60,000 peer-reviewed, empirical studies, we found consistent patterns of bias in the form of increased numbers of studies in temperate systems. Tropical studies were nearly absent from some topics. Furthermore, there were strong taxonomic biases across topics and geographic regions, as well as evidence for citation biases in many topics. Our results indicate a strong geographic imbalance in publishing patterns and among different taxonomic groups across a wide range of topics. The task ahead is to address what these biases mean and how they influence the state of our knowledge in ecology and evolution.
Journal Article
Long-term declines in bird populations in tropical agricultural countryside
by
Ehrlich, Paul R.
,
Horns, Joshua J.
,
Daily, Gretchen C.
in
Agricultural land
,
Agriculture
,
Animal populations
2019
Tropical agriculture is a major driver of biodiversity loss, yet it can provide conservation opportunities, especially where protected areas are inadequate. To investigate the long-term biodiversity capacity of agricultural countryside, we quantified bird population trends in Costa Rica by mist netting 57,255 birds of 265 species between 1999 and 2010 in sun coffee plantations, riparian corridors, secondary forests, forest fragments, and primary forest reserves. More bird populations (69) were declining than were stable (39) or increasing (4). Declines were common in resident, insectivorous, and more specialized species. There was no relationship between the species richness of a habitat and its conservation value. High-value forest bird communities were characterized by their distinct species composition and habitat and dietary functional signatures. While 49% of bird species preferred forest to coffee, 39% preferred coffee to forest and 12% used both habitats, indicating that coffee plantations have some conservation value. Coffee plantations, although lacking most of the forest specialists, hosted 185 bird species, had the highest capture rates, and supported increasing numbers of some forest species. Coffee plantations with higher tree cover (7% vs. 13%) had more species with increasing capture rates, twice as many forest specialists, and half as many nonforest species. Costa Rican countryside habitats, especially those with greater tree cover, host many bird species and are critical for connecting bird populations in forest remnants. Diversified agricultural landscapes can enhance the biodiversity capacity of tropical countryside, but, for the long-term persistence of all forest bird species, large (>1,000 ha) protected areas are essential.
Journal Article
Generalist Species Have a Central Role In a Highly Diverse Plant–Frugivore Network
by
Kattan, Gustavo H.
,
Palacio, Rubén Darío
,
Valderrama-Ardila, Carlos
in
Andean forests
,
Andes region
,
birds
2016
Analysis of plant–frugivore interactions provides a quantitative framework for integrating community structure and ecosystem function in terms of how the roles and attributes of individual species contribute to network structure and resilience. In this study, we used centrality metrics to rank and detect the most important species in a mutualistic network of fruit‐eating birds and plants in a cloud forest in the Colombian Andes. We identified a central core of ten bird and seven plant species in a network of 135 species that perform dual roles as local hubs and connectors. The birds were mostly large forest frugivores, such as cracids, cotingas, and toucans, which consume fruits of all sizes. The plants were species of intermediate successional stages with small‐ to medium‐sized seeds that persist in mature forest or forest borders (e.g., Miconia, Cecropia, Ficus). We found the resilience of our network depends on super‐generalist species, because their elimination makes the network more prone to disassemble than random extinctions, potentially disrupting seed‐dispersal processes. At our study site, extirpation of large frugivores has already been documented, and if this continues, the network might collapse despite its high diversity. Our results suggest that generalist species play critical roles in ecosystem function and should be incorporated into conservation and monitoring programs.
Journal Article
Morphological and Spatio‐Temporal Mismatches Shape a Neotropical Savanna Plant‐Hummingbird Network
by
Oliveira, Paulo E.
,
Vizentin-Bugoni, Jeferson
,
Oliveira, Genilda M.
in
algorithms
,
Brazil
,
Cerrado
2014
Complex networks of species interactions might be determined by species traits but also by simple chance meetings governed by species abundances. Although the idea that species traits structure mutualistic networks is appealing, most studies have found abundance to be a major structuring mechanism underlying interaction frequencies. With a well‐resolved plant–hummingbird interaction network from the Neotropical savanna in Brazil, we asked whether species morphology, phenology, nectar availability and habitat occupancy and/or abundance best predicted the frequency of interactions. For this, we constructed interaction probability matrices and compared them to the observed plant‐hummingbird matrix through a likelihood approach. Furthermore, a recently proposed modularity algorithm for weighted bipartite networks was employed to evaluate whether these factors also scale‐up to the formation of modules in the network. Interaction frequencies were best predicted by species morphology, phenology and habitat occupancy, while species abundances and nectar availability performed poorly. The plant–hummingbird network was modular, and modules were associated to morphological specialization and habitat occupancy. Our findings highlight the importance of traits as determinants of interaction frequencies and network structure, corroborating the results of a previous study on a plant–hummingbird network from the Brazilian Atlantic Forest. Thus, we propose that traits matter more in tropical plant–hummingbird networks than in less specialized systems. To test the generality of this hypothesis, future research could employ geographic or taxonomic cross‐system comparisons contrasting networks with known differences in level of specialization.
Journal Article
Rapid Recovery of Biomass, Species Richness, and Species Composition in a Forest Chronosequence in Northeastern Costa Rica
by
Letcher, Susan G.
,
Chazdon, Robin L.
in
aboveground biomass
,
Animal, plant and microbial ecology
,
Applied ecology
2009
Secondary forests are a vital part of the tropical landscape, and their worldwide extent and importance continues to increase. Here, we present the largest chronosequence data set on forest succession in the wet tropics that includes both secondary and old-growth sites. We performed 0.1 ha vegetation inventories in 30 sites in northeastern Costa Rica, including seven old-growth forests and 23 secondary forests on former pastures, ranging from 10 to 42 yr. The secondary forest sites were formerly pasture for intervals of <1-25 yr. Aboveground biomass in secondary forests recovered rapidly, with sites already exhibiting values comparable to old growth after 21-30 yr, and biomass accumulation was not impacted by the length of time that a site was in pasture. Species richness reached old-growth levels in as little as 30 yr, although sites that were in pasture for > 10 yr had significantly lower species richness. Forest cover near the sites at the time of forest establishment did not significantly impact biomass or species richness, and the species composition of older secondary forest sites (>30 yr) converged with that of old growth. These results emphasize the resilience of tropical ecosystems in this region and the high conservation value of secondary forests.
Journal Article
Temperate Assumptions
2016
Scientists have been observing the natural world for centuries and have long been intrigued by the high biodiversity and complexity of the tropics. They also usually had North American or European—in other words, outsider—perspectives and frequently concluded that the tropics were qualitatively different from the temperate regions in their ecology, evolution, and behavior. In particular, the tropics were seen as having a more benign abiotic environment, which in turn fostered more complex biotic relationships, with increased competition and other interactions. This may or may not be the case. Regardless, these ideas establish the temperate regions of the world as a kind of model system, a norm to which the tropics are compared and seen as different or unusual. The tropics are warmer or more diverse, rather than the temperate zone being cooler or less diverse. Such an attitude makes it difficult both to appreciate the scope of variation in nature and to develop accurate and general models for ecological and evolutionary processes.
Journal Article
Hyperdominance in fruit production in the Brazilian Atlantic rain forest
by
Staggemeier, Vanessa G.
,
Morellato, Leonor Patrícia Cerdeira
,
Cazetta, Eliana
in
animals
,
Arecaceae
,
biomass
2017
The availability of fruits is critical for tropical forests, where the majority of plant species rely upon animal vectors for seed dispersal. However, we do not know how fruit production is temporally distributed over species and families. Two plant families are particularly important in floristic inventories of Atlantic rain forests: Arecaceae, a few species of which are highly abundant; and Myrtaceae, which is abundant and displays outstanding species diversity. In this context, we asked whether hyperdominance occurs in fruit production in the Atlantic rain forest, and whether it occurs in the abundant species of Arecaceae and Myrtaceae. We investigated whether the temporal fruit production patterns differ between Myrtaceae, Arecaceae, and the plant community as a whole. We also applied a functional dispersion index to assess the temporal fruit diversity over a 2-yr period, with regard to morphological and phenological traits. We found that the phenomenon of hyperdominance occurs in fruit production: five species accounted for more than half of the pulp biomass. Arecaceae fruit biomass peaked at the end of wet season, overlapping with the community peak; whereas Myrtaceae species fruited throughout the year and were an important resource during periods of food scarcity. Myrtaceae filled more of the fruit morphospace over time because their fruits exhibit a large range of morphologies and phenological strategies. Our results demonstrated the importance of combining phenology and fruit morphology in the evaluation of resource availability, which revealed periods of high fruit diversity that could support a range of frugivore sizes and maintain overall ecosystem functionality.
Journal Article
Tree Diversity, Forest Structure and Productivity along Altitudinal and Topographical Gradients in a Species-Rich Ecuadorian Montane Rain Forest
by
Günter, Sven
,
Leuschner, Christoph
,
Breckle, Siegmar-W.
in
Andes region
,
Animal, plant and microbial ecology
,
Applied ecology
2010
We studied the spatial heterogeneity of tree diversity, and of forest structure and productivity in a highly diverse tropical mountain area in southern Ecuador with the aim of understanding the causes of the large variation in these parameters. Two major environmental gradients, elevation and topography, representing a broad range of climatic and edaphic site conditions, were analyzed. We found the highest species richness of trees in valleys <2100 m. Valleys showed highest values of basal area, leaf area index and tree basal area increment as well. Tree diversity also increased from ridges to valleys, while canopy openness decreased. Significant relationships existed between tree diversity and soil parameters (pH, total contents of Mg, K, Ca, N and P), and between diversity and the spatial variability of pH and Ca and Mg contents suggesting a dependence of tree diversity on both absolute levels and on the small-scale heterogeneity of soil nutrient availability. Tree diversity and basal area increment were positively correlated, partly because both are similarly affected by soil conditions. We conclude that the extraordinarily high tree species richness in the area is primarily caused by three factors: (1) the existence of steep altitudinal and topographic gradients in a rather limited area creating a small-scale mosaic of edaphically different habitats; (2) the intermingling of Amazonian lowland plant species, that reach their upper distribution limits, and of montane forest species; and (3) the geographical position of the study area between the humid eastern Andean slope and the dry interandean forests of South Ecuador.
Journal Article
Extreme thermal heterogeneity in structurally complex tropical rain forests
by
Macdonald, Stewart L.
,
Andriamahohatra, Lydou R.
,
Edwards, David P.
in
air temperature
,
ambient temperature
,
Anolis
2017
Most terrestrial species on Earth are ectothermic and track temperature at small spatial scales, from sun flecks to cool shaded spots. Current assessments of thermal heterogeneity in complex environments are predominately characterized by ambient temperature. This omission of solar radiation may lead to inaccurate conclusions regarding thermoregulation and distribution of species. We use thermal cameras to gather data on temperature heterogeneity in structurally complex rain forest environments. Using thermographic photographs, we capture the multidimensionality of climate created by vegetation by collecting over 76,000 temperature samples within approximately 1 m² quadrats. The method was tested against three standard methods that record air temperature to determine possible omissions in capturing thermal heterogeneity in four geographic locations—Colombia, Borneo, Madagascar, and Australia. Across all locations, there was greater thermal heterogeneity in surface temperature than captured from ambient temperature technologies. Spatial variability in surface temperature on 1 d was greater than temporal variability of ambient temperature across the entire month, with extreme deviation from ambient temperatures. Importantly, when compared to the lower bounds for optimal performance for five tropical Anolis species, this technology captured thermal regimes that support the thermoregulatory needs of these species, whereas ambient air temperature methods suggested that these species would be in thermal debt. Sampling surface temperature at high resolutions across space in combination with intensive sampling of ambient temperature and informed spatial modeling should improve our understanding of the distribution of ectothermic species living within thermally heterogeneous environments.
Journal Article
Revisiting Patterns of Tree Species Composition and their Driving Forces in the Atlantic Forests of Southeastern Brazil
by
Eisenlohr, Pedro V.
,
de Oliveira-Filho, Ary Teixeira
in
Brazil
,
conservation areas
,
conservation issues
2015
The elucidation of phytogeographic patterns and their drivers in biodiversity hotspots is essential to the study of ecology and the conservation of these areas. In 2000, an important study by Oliveira‐Filho and Fontes led to changes in the paradigms that define our understanding of the Atlantic Forest (Brazil). Here, our aim was to revisit this study using a more comprehensive set of environmental predictors, an updated and much larger tree species dataset and checklist, and more refined data analyses. We performed exploratory and confirmatory analyses, including the modeling of the spatial components with Moran's Eigenvector Maps, using data from 483 sites in southeastern Brazil, which encompass a total of 3546 species and 33 geo‐climatic variables. We observed strong floristic similarities between rain‐ and seasonal forests and a species distribution continuum across the main gradients. The environmental and spatial variables were significantly correlated with floristic patterns, and we demonstrated that the tree flora of the seasonal forests should no longer be considered a simple subset of the rain forest flora. The findings of the original paper were not only confirmed but we also unveiled additional, important phytogeographic patterns. We also reinforced the main conclusion of the paper that the Atlantic Forest concept must encompass all of the forest types east of the dry corridor in South America, a designation of utmost importance for the conservation of this biodiversity hotspot.
Journal Article