Tropical Terrestrial Ecosystems Research Articles

Mercury bioaccumulation in bats in Madre de Dios, Peru: implications for Hg bioindicators for tropical ecosystems impacted by artisanal and small-scale gold mining.

Mercury (Hg) endangers human and wildlife health globally, primarily due to its release from artisanal small-scale gold mining (ASGM). During gold extraction, Hg is emitted into the environment and converted to highly toxic methylmercury by microorganisms. In Madre de Dios (MDD), Peru, ASGM dominates the economy and has transformed rainforests into expansive deforested areas punctuated by abandoned mining ponds. The aim of this study was to evaluate the use of bats as bioindicators for mercury pollution intensity in tropical terrestrial ecosystems impacted by ASGM. We collected 290 bat fur samples from three post-ASGM sites and one control site in Madre de Dios. Our results showed a wide Hg distribution in bats (0.001 to 117.71 mg/kg) strongly influenced by feeding habits. Insectivorous and piscivorous bats from ASGM sites presented elevated levels of Hg surpassing the mercury small mammal threshold for small mammals (10 mg/kg). We observed the highest reported fur mercury concentrations for insectivorous Neotropical bats reported to date (Rhynchonycteris naso, 117 mg/kg). Our findings further confirm that Hg emissions from ASGM are entering local food webs and exposing wildlife species at several trophic levels to higher levels of Hg than in areas not impacted by mining. We also found that three bat genera consistently showed increased Hg levels in ASGM sites relative to controls indicating potential usefulness as bioindicators of mercury loading in terrestrial ecosystems impacted by artisanal and small-scale gold mining.

Evolution of Linoleic Acid Biosynthesis Paved the Way for Ecological Success of Termites.

Termites are dominant animals of tropical terrestrial ecosystems. Their success is due to their eusocial organization as well as their ability to digest dead plant tissues. While being extremely abundant, the termite diet is poor in crucial nutrients, such as fatty acids. Linoleic acid (LA) is a precursor for many vital biomolecules, and most animals depend on its dietary supply. Termites count among the exceptions known to produce LA de novo, presumably via the action of an unknown Δ12 fatty acyl desaturase (FAD) introducing the second double bond into monounsaturated oleic acid. Here, we search for the evolutionary origin of LA biosynthesis in termites. To this end, we compile the repertoire of FAD homologs from 57 species of termites and their closest relatives, the cockroaches, analyze FAD phylogeny, and identify a potential Δ12 FAD branch, which arose through duplication of a likely Δ9 FAD. We functionally characterize both paralogs and identify the Δ9 activity in the ancestral FAD-A1a and the Δ12 activity responsible for LA biosynthesis in FAD-A1b. Through the combination of homology modeling and site-directed mutagenesis, we pinpoint structural features possibly contributing to the distinct functions, regiospecificities, and substrate preferences of the two enzymes. We confirm the presence of both paralogs in all 36 studied species of the Blattoidea lineage (Blattidae, Lamproblattidae, Cryptocercidae, and termites) and conclude that we identified an evolutionary event important for the ecological success of termites, which took place in their cockroach ancestors roughly 160 My and remained conserved throughout termite diversification into 3,000 extant species.

What evidence exists on the links between natural climate solutions and climate change mitigation outcomes in subtropical and tropical terrestrial regions? A systematic map protocol

BackgroundNatural climate solutions (NCS)—actions to conserve, restore, and modify natural and modified ecosystems to increase carbon storage or avoid greenhouse gas (GHG) emissions—are increasingly regarded as important pathways for climate change mitigation, while contributing to our global conservation efforts, overall planetary resilience, and sustainable development goals. Recently, projections posit that terrestrial-based NCS can potentially capture or avoid the emission of at least 11 Gt (gigatons) of carbon dioxide equivalent a year, or roughly encompassing one third of the emissions reductions needed to meet the Paris Climate Agreement goals by 2030. NCS interventions also purport to provide co-benefits such as improved productivity and livelihoods from sustainable natural resource management, protection of locally and culturally important natural areas, and downstream climate adaptation benefits. Attention on implementing NCS to address climate change across global and national agendas has grown—however, clear understanding of which types of NCS interventions have undergone substantial study versus those that require additional evidence is still lacking. This study aims to conduct a systematic map to collate and describe the current state, distribution, and methods used for evidence on the links between NCS interventions and climate change mitigation outcomes within tropical and sub-tropical terrestrial ecosystems. Results of this study can be used to inform program and policy design and highlight critical knowledge gaps where future evaluation, research, and syntheses are needed.MethodsTo develop this systematic map, we will search two bibliographic databases (including 11 indices) and 67 organization websites, backward citation chase from 39 existing evidence syntheses, and solicit information from key informants. All searches will be conducted in English and encompass subtropical and tropical terrestrial ecosystems (forests, grasslands, mangroves, agricultural areas). Search results will be screened at title and abstract, and full text levels, recording both the number of excluded articles and reasons for exclusion. Key meta-data from included articles will be coded and reported in a narrative review that will summarize trends in the evidence base, assess gaps in knowledge, and provide insights for policy, practice, and research. The data from this systematic map will be made open access.

Termite Fauna of Sungai Kangkawat, Imbak Canyon Conservation Area (ICCA), Sabah

Termites are important inhabitants of the tropical rain forest, and they are commonly found in tropical soils. They have great importance in tropical terrestrial ecosystems especially in the decomposition process, mediate ecosystem processes and facilitate to improve the structure and quality of the soil. This study was conducted to identify the termite fauna of Sungai Kangkawat, Imbak Canyon Conservation Area (ICCA). Termites were collected using a standardized 100mx2m line transect at South Rim Trail and also through casual collection around the study site. A total of 31 termite species were recorded in this study. The termite assemblage comprises two families namely, Rhinotermitidae and Termitidae. Family Termitidae dominated the termite assemblage with 87.1% (27 species). The collected termite species in this study comprises 30% of recorded termite species of Sabah. Seven subfamilies that are commonly recorded in the tropical forest were identified in this study. Subfamily Termitinae and Nasutitermitinae from family Termitidae dominated the termite assemblage of Sungai Kangkawat with 12 species and ten species respectively. The previous study conducted at ICCA recorded 29 species which have 43.9% similarity with the current study. A total of 12 species were identified as new records for ICCA through this study. Hence, the total number of termite species of ICCA is 41. This study has provided the checklist of termite fauna in Sungai Kangkawat and updated the termite checklist of ICCA.

Pantropical geography of lightning-caused disturbance and its implications for tropical forests.

Lightning is a major agent of disturbance, but its ecological effects in the tropics are unquantified. Here we used ground and satellite sensors to quantify the geography of lightning strikes in terrestrial tropical ecosystems, and to evaluate whether spatial variation in lightning frequency is associated with variation in tropical forest structure and dynamics. Between 2013 and 2018, tropical terrestrial ecosystems received an average of 100.4 million lightning strikes per year, and the frequency of strikes was spatially autocorrelated at local-to-continental scales. Lightning strikes were more frequent in forests, savannas, and urban areas than in grasslands, shrublands, and croplands. Higher lightning frequency was positively associated with woody biomass turnover and negatively associated with aboveground biomass and the density of large trees (trees/ha) in forests across Africa, Asia, and the Americas. Extrapolating from the only tropical forest study that comprehensively assessed tree damage and mortality from lightning strikes, we estimate that lightning directly damages c. 832 million trees in tropical forests annually, of which c. 194 million die. The similarly high lightning frequency in tropical savannas suggests that lightning also influences savanna tree mortality rates and ecosystem processes. These patterns indicate that lightning-caused disturbance plays a major and largely unappreciated role in pantropical ecosystem dynamics and global carbon cycling.

Invertebrates and the complexity of tropical ecosystems

AbstractIt has been estimated that there are seven million terrestrial arthropod species on Earth consisting of 6.1 million species of insects, 1.5 million of which are beetles. Tropical forests hold a majority of these species, yet few such places have been adequately sampled for alpha diversity, and there remains even more uncertainty about beta diversity. From an ecological point of view, it is the functional role of organisms within ecosystems that is the particular focus. It has been customary to classify invertebrates within ecosystems in terms of their trophic roles, but it is also useful to consider their roles in networks. In broad terms, we can classify these networks on the grounds of their basal resources. Those based directly on the photosynthetic products of plants are so‐called “green” food webs, and those based on dead and dying plant material are “brown” food webs. Here, we principally discuss the diversity and functional roles of the invertebrates in tropical terrestrial ecosystems. New sampling and analytical techniques, an expanded set of focal taxa, and an enhanced concern with interactions and processes hold the promise of a productive future for invertebrate studies in the tropics. These will not only add to general understanding of the dynamics of tropical ecosystems but will also provide powerful tools for monitoring and responding to environmental change.

Bushmeat biogeochemistry: hunting tropical mammals alters ecosystem phosphorus budgets.

Wild meat (or 'bushmeat') hunting is nearly ubiquitous across the tropics and is very often unsustainable-driving declines and extirpation of numerous mammal populations. Loss of these animals can alter the transport of nutrients within and between ecosystems. But whether the physical removal of vertebrate carcasses and the nutrients that they store can reduce overall nutrient availability in ecosystems has been little explored. At 32 sites on three continents, we show that annual phosphorus (P) loss via mammal exploitation was low relative to the rate of atmospheric P deposition. But at four sites in Africa and Southeast Asia, removal of P in the skeletons of hunted mammals exceeded the atmospheric input of this nutrient by 10-fold or more. Because P is the growth-limiting nutrient for many tropical terrestrial ecosystems and certain large mammals, the imbalance created by the removal of mammal biomass under very high hunting scenarios could reduce ecosystem carrying capacity if no compensatory P additions occur in the system. This biogeochemical perspective on bushmeat exploitation raises further concerns about harvest sustainability and human food security in areas where hunting rates are high and ecosystem P inputs low.

Predictability of tropical vegetation greenness using sea surface temperatures**This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form

Much research has examined the sensitivity of tropical terrestrial ecosystems to various environmental drivers. The predictability of tropical vegetation greenness based on sea surface temperatures (SSTs), however, has not been well explored. This study employed fine spatial resolution remotely-sensed Enhanced Vegetation Index (EVI) and SST indices from tropical ocean basins to investigate the predictability of tropical vegetation greenness in response to SSTs and established empirical models with optimal parameters for hindcast predictions. Three evaluation metrics were used to assess the model performance, i.e., correlations between historical observed and predicted values, percentage of correctly predicted signs of EVI anomalies, and percentage of correct signs for extreme EVI anomalies. Our findings reveal that the pan-tropical EVI was tightly connected to the SSTs over tropical ocean basins. The strongest impacts of SSTs on EVI were identified mainly over the arid or semi-arid tropical regions. The spatially-averaged correlation between historical observed and predicted EVI time series was 0.30 with its maximum value reaching up to 0.84. Vegetated areas across South America (25.76%), Africa (33.13%), and Southeast Asia (39.94%) were diagnosed to be associated with significant SST-EVI correlations (p < 0.01). In general, statistical models correctly predicted the sign of EVI anomalies, with their predictability increasing from ∼60% to nearly 100% when EVI was abnormal (anomalies exceeding one standard deviation). These results provide a basis for the prediction of changes in greenness of tropical terrestrial ecosystems at seasonal to intra-seasonal scales. Moreover, the statistics-based observational relationships have the potential to facilitate the benchmarking of Earth System Models regarding their ability to capture the responses of tropical vegetation growth to long-term signals of oceanic forcings.

Linkage between tropical terrestrial carbon cycle and precipitation: The two anomalous years of 1979 and 1996

Tropical terrestrial ecosystems are the critical driver of the land carbon cycle and climate change. Previous studies have reported strong response in the tropical land carbon cycle to precipitation anomalies in post‐La Niña years. We show that among the post‐La Niña years, 1979 and 1996 stand out strikingly different from other years. 1979 has one of the largest atmospheric CO2 growth rate (CGR) while 1996 has one of the smallest CGR, despite that their annual tropical precipitation anomalies are small. We show that these 2 years correspond to opposite seasonal precipitation anomalies over tropical vegetated lands in the wet‐to‐dry transition seasons in which negative correlation between precipitation and CGR is the strongest. 1979 has large dry anomaly during the transition season, inhibiting land carbon uptake, while 1996 has large wet anomaly during the transition season, favoring more carbon uptake by the tropical ecosystem. Results here highlight the importance of seasonality of climate anomalies and their timing of occurrences with the rhythm of the carbon–climate coupling.

Response of Tropical Terrestrial Gross Primary Production to the Super El Niño Event in 2015

AbstractThe gross primary production (GPP) in tropical terrestrial ecosystems plays a critical role in the global carbon cycle and climate change. The strong 2015–2016 El Niño event offers a unique opportunity to investigate how GPP in the tropical terrestrial ecosystems responds to climatic forcing. This study uses two GPP products and concurrent climate data to investigate the GPP anomalies and their underlying causes. We find that both GPP products show an enhanced GPP in 2015 for the tropical terrestrial ecosystem as a whole relative to the multiyear mean of 2001–2015, and this enhancement is the net result of GPP increase in tropical forests and decrease in nonforests. We show that the increased GPP in tropical forests during the El Nino event is consistent with increased photosynthesis active radiation as a result of a reduction in clouds, while the decreased GPP in nonforests is consistent with increased water stress as a result of a reduction of precipitation and an increase of temperature. These results reveal the strong coupling of ecosystem and climate that is different in forest and nonforest ecosystems and provide a test case for carbon cycle parameterization and carbon‐climate feedback simulation in models.

The Permian (Kungurian, Cisuralian) palaeoenvironment and palaeoclimate of the Tregiovo Basin, Italy: Palaeobotanical, palynological and geochemical investigations

A transition from widespread humid to more drought tolerant floras characterized tropical terrestrial ecosystems during the Permian (Cisuralian). Tregiovo (Southern Alps, N-Italy) is one of the very few well dated Kungurian (late Cisuralian) plant localities in Euramerica. It was located in eastern palaeoequatorial Pangea. Two units bearing fossil plant assemblages occur in finely laminated sediments deposited in a playa-lake environment. In this paper, the sedimentology of the Tregiovo Basin is reviewed, and new palaeobotanical, palynological and stable isotopic data are presented, in order to reconstruct the palaeoclimatic and palaeoenvironmental conditions of the Kungurian in the Southern Alps. Both fossil plant assemblages are dominated by conifers (Hermitia, Feysia, Quadrocladus, Dolomitia), together with sphenophytes (Annularia), ginkgophytes (Sphenobaiera), pteridosperms (Peltaspermum), taeniopterids and sphenopterids. These taxa, which occur with different abundances in the two plant assemblages, both indicate semi-arid conditions. Associated palynoflora, dominated by bisaccate pollen, and extremely rare spore occurrences, is consistent with the xerophytic character of the macroflora, and suggests that the fossil plant record was not affected by collection or preservation bias. Stable isotopic analyses of two stratigraphic sections reveal an upward trend of increasingly negative δ13Corg (VPDB), which may correlate with roughly coeval records from marine and continental successions such as in North China and South Africa. This isotopic shift may be attributed to a global perturbation of atmospheric δ13C, although the influence of local environmental factors cannot be excluded.

Cerrado vegetation types determine how land use impacts ant biodiversity

The simplification of native habitats leads to biodiversity decline in tropical terrestrial ecosystems. We evaluated how conversion of three types of native Cerrado vegetation (open grassland, typical savanna, and woodland savanna) to two human-managed land uses (Eucalyptus plantations and pastures) affects ant richness and composition in arboreal, epigaeic, and hypogaeic ant communities. We also sampled vegetation and soil characteristics to determine which specific features could be driving differences in ant communities with land use conversion. In general, biodiversity was negatively affected by conversion to Eucalyptus plantations and pastures regardless of vegetation type. But these impacts do not act in the same way in each ant strata or vegetation type. Grass and herbaceous cover was the most important environmental variable correlated with diversity in open grassland and plant richness and litter diversity were the most important environmental variables for ant species in typical and woodland savannas. Our results indicate that expanding Eucalyptus plantations may have stronger negative impacts from conversion of open vegetation types while pasture implementation may have stronger negative effects if implemented in closed vegetation types. Thus, we show the need of protection of the diversity of all native vegetation found in the Brazilian Cerrado (from open to forested habitats).

Parasites dominate hyperdiverse soil protist communities in Neotropical rainforests.

High animal and plant richness in tropical rainforest communities has long intrigued naturalists. It is unknown if similar hyperdiversity patterns are reflected at the microbial scale with unicellular eukaryotes (protists). Here we show, using environmental metabarcoding of soil samples and a phylogeny-aware cleaning step, that protist communities in Neotropical rainforests are hyperdiverse and dominated by the parasitic Apicomplexa, which infect arthropods and other animals. These host-specific parasites potentially contribute to the high animal diversity in the forests by reducing population growth in a density-dependent manner. By contrast, too few operational taxonomic units (OTUs) of Oomycota were found to broadly drive high tropical tree diversity in a host-specific manner under the Janzen-Connell model. Extremely high OTU diversity and high heterogeneity between samples within the same forests suggest that protists, not arthropods, are the most diverse eukaryotes in tropical rainforests. Our data show that protists play a large role in tropical terrestrial ecosystems long viewed as being dominated by macroorganisms.

New Records of the Dorylinae Ant Genus Cheliomyrmex for the Brazilian Amazon Basin

The Dorylinae subfamily are dominant invertebrate predators in tropical and subtropical terrestrial ecosystems. The most cryptic army ant genus of the New World is Cheliomyrmex. The only specie recognized until now to the Amazon Brazilian Basin is C. andicola , with record in the state of Acre. We provided the first record of Cheliomyrmex megalonyx to Brazil in the Amazon Basin. This record strongly reinforces the idea that more efforts are needed to reveal the diversity, distribution and biology of such hypogaeic ants.

The roles of productivity and ecosystem size in determining food chain length in tropical terrestrial ecosystems

Many different drivers, including productivity, ecosystem size, and disturbance, have been considered to explain natural variation in the length of food chains. Much remains unknown about the role of these various drivers in determining food chain length, and particularly about the mechanisms by which they may operate in terrestrial ecosystems, which have quite different ecological constraints than aquatic environments, where most food chain length studies have been thus far conducted. In this study, we tested the relative importance of ecosystem size and productivity in influencing food chain length in a terrestrial setting. We determined that (1) there is no effect of ecosystem size or productive space on food chain length; (2) rather, food chain length increases strongly and linearly with productivity; and (3) the observed changes in food chain length are likely achieved through a combination of changes in predator size, predator behavior, and consumer diversity along gradients in productivity. These results lend new insight into the mechanisms by which productivity can drive changes in food chain length, point to potential for systematic differences in the drivers of food web structure between terrestrial and aquatic systems, and challenge us to consider how ecological context may control the drivers that shape food chain length.

Tropical terrestrial model ecosystems for evaluation of soil fauna and leaf litter quality effects on litter consumption, soil microbial biomass and plant growth

The aim of this work was to evaluate whether terrestrial model ecosystems (TMEs) are a useful tool for the study of the effects of litter quality, soil invertebrates and mineral fertilizer on litter decomposition and plant growth under controlled conditions in the tropics. Forty-eight intact soil cores (17.5-cm diameter, 30-cm length) were taken out from an abandoned rubber plantation on Ferralsol soil (Latossolo Amarelo) in Central Amazonia, Brazil, and kept at 28ºC in the laboratory during four months. Leaf litter of either Hevea pauciflora (rubber tree), Flemingia macrophylla (a shrubby legume) or Brachiaria decumbens (a pasture grass) was put on top of each TME. Five specimens of either Pontoscolex corethrurus or Eisenia fetida (earthworms), Porcellionides pruinosus or Circoniscus ornatus (woodlice), and Trigoniulus corallinus (millipedes) were then added to the TMEs. Leaf litter type significantly affected litter consumption, soil microbial biomass and nitrate concentration in the leachate of all TMEs, but had no measurable effect on the shoot biomass of rice seedlings planted in top soil taken from the TMEs. Feeding rates measured with bait lamina were significantly higher in TMEs with the earthworm P. corethrurus and the woodlouse C. ornatus. TMEs are an appropriate tool to assess trophic interactions in tropical soil ecossistems under controlled laboratory conditions.

Termite mounds as hot spots of nitrous oxide emissions in South‐Sudanian savanna of Burkina Faso (West Africa)

Despite a considerable knowledge of the significant role of termites in the global methane budget, very little is known about their contribution to the global nitrous oxide (N2O) budget. Release of N2O from termite (Cubitermes fungifaber) mounds was measured at a natural savanna site in the southwest of Burkina Faso from May to September 2006. Termite N2O emissions were around 20 μg N2O‐N m–2 h–1 at the end of the dry season, and up to two orders of magnitude higher than N2O emissions from the surrounding termite‐free soil after the onset of the rainy season. The average N2O emission rate from termite mounds during the observation period was 204 μg N2O‐N m–2 h–1, and termite mounds contributed 3.0% to total N2O emissions from this savanna ecosystem. However, in other tropical terrestrial ecosystems with other termite species and/or higher termite density this share might be significantly higher.

Giant boid snake from the Palaeocene neotropics reveals hotter past equatorial temperatures

The largest extant snakes live in the tropics of South America and southeast Asia where high temperatures facilitate the evolution of large body sizes among air-breathing animals whose body temperatures are dependant on ambient environmental temperatures (poikilothermy). Very little is known about ancient tropical terrestrial ecosystems, limiting our understanding of the evolution of giant snakes and their relationship to climate in the past. Here we describe a boid snake from the oldest known neotropical rainforest fauna from the Cerrejón Formation (58-60 Myr ago) in northeastern Colombia. We estimate a body length of 13 m and a mass of 1,135 kg, making it the largest known snake. The maximum size of poikilothermic animals at a given temperature is limited by metabolic rate, and a snake of this size would require a minimum mean annual temperature of 30-34 degrees C to survive. This estimate is consistent with hypotheses of hot Palaeocene neotropics with high concentrations of atmospheric CO(2) based on climate models. Comparison of palaeotemperature estimates from the equator to those from South American mid-latitudes indicates a relatively steep temperature gradient during the early Palaeogene greenhouse, similar to that of today. Depositional environments and faunal composition of the Cerrejón Formation indicate an anaconda-like ecology for the giant snake, and an earliest Cenozoic origin of neotropical vertebrate faunas.

Paleoecology Of Early-Middle Permian Marine Communities In Eastern Australia: Response To Global Climate Change In the Aftermath Of the Late Paleozoic Ice Age

Climate change has exerted a major influence on the biosphere in historical times, altering the geographic range of many species and elevating the extinction risk in both marine and terrestrial realms. This study investigates marine community change during the major early Permian climatic transition from the late Paleozoic ice age to a largely ice-free greenhouse climate. Quantitative counts of fossil abundance from 71 field assemblages and 15 collections from the literature, spanning the early and middle Permian (Sakmarian– Capitanian) of the Tasmania, Sydney, and Bowen basins of eastern Australia document substantial changes in the composition of marine communities during Sakmarian–Kungurian postglacial warming. During the last stages of glaciation (Sakmarian), communities were dominated by the brachiopod Trigonotreta and the bivalve Eurydesma, whereas communities from the later greenhouse climate (Kungurian–Guadalupian) contained abundant productide brachiopods such as Terrakea and Echinalosia. The shift was broadly synchronous at all paleolatitudes within eastern Australia but appears to have occurred first in offshore habitats. Artinskian communities may also have been much more variable than either earlier or later communities. This variability may have been triggered by rapid climate fluctuations, similar to the changes observed in Artinskian tropical terrestrial ecosystems, but it may also stem from sampling a greater number of depositional environments and habitat types. The ultimate fate of the dominant glacial genera differed after they lost dominance, with Eurydesma becoming extinct during climate warming but Trigonotreta persisting at low abundance levels for a much longer time. These results support the theory that climate change most often causes extinctions through indirect paleoecological effects and underscore the important consequences that even gradual, long-term climate change can have in marine ecosystems.

Effects of large‐scale climatic fluctuations on survival and production of young in a Neotropical migrant songbird, the yellow warblerDendroica petechia

Migrant songbirds are vulnerable to changes in climatic conditions on both the breeding and wintering grounds. For North American Neotropical migrants, the El Niño/Southern Oscillation (ENSO), via its effects on global precipitation and temperature, modulates the productivity of their temperate and tropical terrestrial ecosystems used during the course of their annual cycle. We evaluated how a densely nesting population of yellow warblersDendroica petechiain a riparian forest in southern Manitoba, Canada, responded to the El Niño/Southern Oscillation (ENSO) between 1992 and 2001. Standardized mist netting was used to estimate apparent annual survival of adults and production of young. Both adult survival and the production of young were positively correlated with the Southern Oscillation Index (SOI). More specifically, values of both these demographic parameters were lowest during El Niño years and highest during La Niña years. These findings demonstrate the influence of climate on populations of Neotropical migrants in North America. The more frequent El Niños predicted to result from future global climate change could negatively affect populations of yellow warblers and other Neotropical migrants breeding in this region.