Bees, like microbes, live everywhere and interact as parasites, commensals and mutualists. They are not boxes of insects — they are 30,000 species living primarily in the temperate zone, without honey, queen, or castes, solitarily, and do amazing things, including making possible the reproduction of roughly half of all plants. Bees have deep relations with bacteria, fungi and archaea. They are much more likely to be social or make honey, or be present at flowers, in the tropics, where their total species richness is nonetheless much lower than in many warm temperate areas.

Insect colonies — big ones — need to store fuel, materials, and protein to continue. Their dispersion matters. Their defenses from enemies must be well coordinated. Their need for making the most of stored protein, carbohydrates, etc. involves managing their microbial communities and propagating them through generations. People believe that bee food, including larvae, honey and pollen or ‘bee bread’ and propolis (a resinous mixture of building material) have medicinal value. The chemical, microbiological and botanical components are ripe for further investigation, especially in the tropics. Honey from native vegetation is usually from about 50 plant species, making honey the most biodiverse natural product.

Animal populations never are stable. Surveys of living organisms, like bees or other pollinators, are few and far between, and often do not consider biologically important ‘recent’ events — e.g. periodic El Niño-Southern Oscillation droughts which are highly positively correlated with flowering peaks and bee populations, or heavy rainfall, or human impact. Bee nests are in the soil, in dead branches, in living trees, in tilled land, in urban areas, or in forest. Not all bees are the same, their parasite and predator pressures differ, their reproductive seasons are diverse, in the case of bee colonies, whole-colony reproduction does not occur with a high predictably. We need to make more efforts to fill our knowledge gaps, by making comparative studies.

Competition theory never explained much about pollinators. Their interactions are properly defined in networks, in which they are facilitators, competitors or flat-out mutualists, simultaneously. It is a question for integral calculus, not short- or medium-term field experiments (which is the best that I or others can do, for a number of reasons), or based on a simple matrix or network. The Africanized honeybee studied for 17 years pre- and post-invasion in Yucatán gave us a reference point. They caused resource partitioning, and then evidently an expanded resource base, which their competitors benefit from. This is not Lotka-Volterra anymore.

The development of agricultural societies made possible by plant and animal domestication was one of the most transformative events in human and ecological history. Independent beginnings of agriculture occurred between 12,000 and 10,000 years ago in a number of world regions, including the American tropics, southwest Asia, and China. Plant domestication was at its core an evolutionary process involving both natural and human selection for traits favorable for harvesting and consumption. Ever-improving analytic methods for retrieving empirical data from archaeological sites, together with advances in genetic, genomic, and experimental research on living crops and their wild ancestors are providing new understandings of, and mechanisms for domestication and early agriculture (see discussion under Research Focus). Scholars have long debated why hunters and gatherers became farmers, a question that will also see increasing understanding.

Prominent scholars once believed that the Neotropical forest vegetation and landscape were little altered by pre-Columbian cultures. It is now known that significant, sometimes profound, human environmental modification of many types (fire, vegetation clearing; depression of preferred prey through over-exploitation; construction of earthworks and roads) has a deep history in the American tropics. However, some regions remain understudied. Still not understood, for example, is when and how a human presence may have modified landscapes across the vast terra firme (interfluvial) forest zone of the Amazon Basin. Multi-proxy analyses of lake sediments and terrestrial soils (e.g., pollen, phytoliths, charcoal) are at once improving our resolution of both natural- and human-cased environmental change in Amazonia and elsewhere, and expanding the types of locations such evidence can be found in.

Plant microfossils such as phytoliths, starch grains, and pollen can be used to effectively study prehistoric plant exploitation and agriculture. In the Neotropics, many important crops such as maize, squashes, manioc, and yams can be identified. Archaeological materials offering robust contexts for microfossil study now include stone tools, ceramics, sediments, and human teeth. Future research should expand the number of identifiable taxa and refine current identifications, discover more about the types of plant preparation and consumption the microfossils can reveal (e.g., chicha-making?), and add to understanding of their roles in documenting prehistoric plant usage in the Neotropics and elsewhere.

Mechanistic, physiologically based models can explain much of the variation in forest productivity with climate and soils, but little of the variation in mortality fluxes and biomass stocks. As lead scientist of the Forest Carbon Research Initiative for the Center for Tropical Forest Science-Forest Global Earth Observatory (CTFS-ForestGEO), I strive to implement standardized measurements of forest carbon stocks and fluxes across this network of forest plots, assist network collaborators with associated analyses and manuscripts, and contribute to related syntheses. My lab is also quantifying landscape-scale variation in forest canopy structure and dynamics in Panama using camera-carrying unmanned aerial vehicles and photogrammetry.

Lianas (woody climbing plants) and vines (nonwoody climbing plants) vary widely in abundance within and among tropical forests, with important implications for forest carbon budgets. Lianas and vines reduce tree growth, increase tree mortality rates, and alter forest structure and composition. Past studies have established that climbing plants are more abundant in drier forests, younger forests, and on edges – but scientists currently lack a mechanistic understanding for what determines their abundance in any forest, much less its variation across forests. We are pursuing a variety of empirical and theoretical studies to identify the factors that control the abundances of these structural parasites.

Individual tropical forests commonly contain >100 woody plant species in an area the size of a football field, and can contain >1,000 species in a square kilometer. Ecologists have long debated what mechanisms prevent one or a few species from outcompeting and excluding the others. Tradeoffs in performance among spatially varying habitats and temporally varying climate conditions clearly play a role, as do interactions with specialized natural enemies that tend to disproportionately plague and disadvantage any given species in areas where it is locally more common. We work to evaluate the strength of different mechanism and quantify their roles through a combination of theory and empirical analyses.

Co-occurring plant species differ tremendously in their life history strategies and in related functional traits. A classic example is seed mass, which commonly varies more than 1-million-fold among tree species within any given tropical forest. The persistence of this variation clearly indicates that one or more underlying tradeoffs prevents any one strategy from being everywhere superior. But what exactly are these underlying tradeoffs? Using mutually informed theoretical development and empirical analyses, we seek to identify the underlying tradeoffs and capture them mechanistically in sufficient detail to quantitatively explain observed patterns of variation.

Earth system models (ESMs) simulate the earth’s climate system and its interaction with vegetation, and are used to predict the influences of policy scenarios on future atmospheric composition and climates. Among other things, these models simulate the feedbacks between tropical forests and the climate system. However, these models are currently unable to correctly capture observed spatial and temporal variation in tropical forest carbon budgets, and diverge wildly in their predictions of future responses. We are collaborating with two ESM development teams to improve the representation of tropical forests in these models by building more accurate representations of key processes and improving parameter estimates. Visit the pages NGEE-Tropics and GFLD LM3 for more details.

The amount of leaf area deployed and the age distribution of leaves varies seasonally and interannually in tropical forests in relation to climate, and is critical to determining temporal variation in ecosystem carbon, water, and energy fluxes. We hypothesize that interspecific variation in phenology is a key determinant of which species thrive in drier vs. wetter forests, in sunnier vs. cloudier years, and in rich vs. poor soils. We are quantifying the phenology of thousands of trees using camera-carrying unmanned aerial vehicles; analyzing how individual tree and liana phenology relates to temporal climate variation, spatial environmental variation, and species traits; and evaluating the implications of phenology for ecosystem fluxes by integrating these data with models.

There is uncertainty about the fate of tropical forests in the face of contemporary atmospheric and climate change. My colleagues and I use naturally lit geodesic glass domes and other controlled-environment facilities to simulate future tropical environmental scenarios. We expose plants representing different life forms and functional types to elevated CO₂ concentrations and temperatures. Soil nutrients and soil water availability are additional variables. We measure growth, photosynthesis, respiration, water use, chemical composition and reproduction. These experiments are expected to provide answers to several key questions: (1) Will there be winners and losers among species? (2) Can tropical plants acclimatize? (3) When does climate change reach a tipping point for tropical plants? 

On clear sunny days, especially during the dry season, the tropical forest canopy is a desert environment. When exposed to full sunlight, outer-canopy leaves transiently close their stomatal pores to minimize water loss through transpiration, CO₂ assimilation falls to zero, and leaves heat up. STRI’s two canopy cranes allow us into the forest canopy and to study a wide range of tree and liana species. We use sophisticated portable photosynthesis equipment and chlorophyll fluorescence probes to monitor the physiology of leaves, determine key biochemical processes underlying photosynthesis, and examine how the carbon budgets of leaves are affected under these extreme conditions. Our studies help to unravel the mechanisms of heat tolerance, photoprotection and protection against hydraulic failure in canopy species. 

Studies on Earth’s biodiversity traditionally emphasize the quantitative cataloguing of species and the diversity of morphology. Modern biodiversity studies also address the astonishing functional diversity of organisms. Photosynthetic pathway diversity is a major research theme of the Winter lab, with emphasis on the functional importance and evolutionary origins of the water-conserving CAM (crassulacean acid metabolism) pathway. In contrast to most plants, which display C₃ photosynthesis and sequester atmospheric CO₂ during the daytime, CAM plants incorporate carbon dioxide primarily during the cool of the night when the risk of dehydration is reduced. Nocturnal uptake of CO₂ typically occurs in desert succulents such as cacti and agaves but, as our research has shown, is also a key innovation that has enabled many bromeliads and orchids to occupy periodically dry epiphytic microhabitats in the humid tropics. In the Winter lab, we focus on a hitherto still small, but expanding, number of species that exhibit CAM in an optional, facultative manner. They are C₃ plants when well-watered, switch to CAM when exposed to drought stress, and revert to the C₃ phenotype when re-watered. Species with this special physiology undoubtedly represent one of the best examples of metabolic flexibility in the plant kingdom. We study facultative CAM in tropical tree species of the genus Clusia and, quite surprisingly, have recently discovered facultative CAM in two species widely used as tropical vegetables. While hunting for more species with this remarkable phenotypic plasticity, our principal research addresses three major questions: 1) What is the adaptive significance of facultative CAM under natural tropical conditions? 2) Are facultative CAM species transitional intermediates along the evolutionary trajectory from C₃ to full CAM? 3) How is the physical stress signal translated into the biochemical response, i.e. the shift to CAM, and which genes are upregulated?  

I think we have the answer. Where a tropical tree species is abundant, its juveniles perform poorly. Where the same tree species is rare, its juveniles often thrive. This strong, pervasive, negative density dependence prevents any one species from dominating most tropical forests. The question now is why?

We believe the family Chrysomelidae (“leaf beetles”) is a veritable gold mine in this respect in that it is composed of taxa (subfamilies and tribes) with uneven levels of species diversity and wildly contrasting patterns of maternal investment and offspring feeding behavior. Ultimately, all Chrysomelidae are dependent upon plants, both gymnosperms and angiosperms, and within the latter, both monocots and dicots. We seek to integrate both botanical and entomological data to better understand the radiations of tropical leaf beetles, how their diversity has been affected by host plant traits and the role of innovations in larval trophic habits and defensive measures. Employing the comparative method to approach these questions requires assembling a robust phylogeny and gathering of life history information for a surprisingly large number of incompletely studied and described tropical beetle species.

Depending on which tribe of Cassidinae one is considering, trophic habits may be constrained or expansive. For example, those Cassidinae species which feed on exposed, second-growth vegetation tend to be associated with a small number (five to eight) of host plant families of dicotyledenous plants (morning glories, borages, asters, etc). The same is also approximately true for species feeding cryptically in semi-concealed habitats on undergrowth and forest vegetation including mainly monocotyledenous plants (gingers, palms, etc). Interesting and inexplicably, the diets of internally feeding, leaf-mining species differ in that they appear to have colonized a much broader sample of available host plant families, both Monocotylenonae and Dicotyledonae. We now ask whether these patterns are due to differences in the ages of the respective groups or are due to other factors governing the expansion of feeding habits.

Rice (Oryza sativa) was presumably introduced to Panama and other parts of the Americas from Africa and Asia centuries ago. Not until recently, however, have we taken note that this important exotic plant has become a favorite host of one species of cassidine beetle. Indigenous and other subsistence farmers growing rice in the eastern Province of Darien lose a considerable fraction of their crops to Oediopalpa guerini, a small, shiny blue-bodied beetle known to occur on other native and introduced grasses. Unlike the eggs of other Cassidinae in Panama, they are everywhere attacked by minute wasps in the family Trichogrammatidae, a group of parasitoids widely used across the world in biocontrol. In this particular case, however, our observations indicate the tendency of the ovipositing beetle to stack eggs one upon another limits the loss of eggs to a maximum of 40-50% and hence poses a limit on how successful biocontrol efforts might be. As a result, other means of naturally controlling this beetle in Panama must be investigated.

Beetles in the family Orsodacnidae are potent herbivores on many species of cycads in the Americas. Adults emerge at the beginning of each rainy season and proceed to inflict high levels of leaf damage over a very short period of time. These beetles are particularly enigmatic in that they do not fit easily into existing leaf beetle families and hence are relegated to their own species-poor family with uncertain evolutionary relationships to other families. Beetle fossils taken from Jurassic sediments of Kazakhstan and China suggest to some that the family may date back largely unchanged to the early and mid Mesozoic, a time when early gymnosperms and cycads were abundant and diverse. The complete life cycle of Neotropical Orsodacnidae remains an enduring mystery. We study this group to know whether their relationship with cycads is more intricate than a brief but intense period of herbivory would indicate.

By observing the behavior and natural history of many types of group-living tropical wasps, looking especially at the interactions of individuals within groups, you can see what has likely been central to their diversification and specialization as social animals.

Social competition (social selection), whether for mates (Darwinian sexual selection) or for other resources (e.g. among female wasps) leads to the evolution of extreme signals of rank and to social hierarchy and stratification. I am studying evidence that this has affected access to food during human evolution, and helped to define certain aspects of human body shape and the obesity epidemic.

Starting with principles outlined in a book (West-Eberhard 2003) on Developmental Plasticity and Evolution, I am evaluating a recent hypothesis regarding the fetal effects of maternal nutrition on the adult phenotype, in relation to obesity and associated chronic diseases (e.g. type-2 diabetes and cardiovascular disease).

By studying hydrology and biogeochemistry of natural and human-altered landscapes in the Americas, Southeast Asia and Africa, I contribute to new concepts integrating atmospheric and terrestrial processes and the role of people as ecosystem shapers.

Any process that alters most of a landscape, from construction, to agriculture, to fire alter the way that landscape processes water from rain or snowmelt. These processes usually increase vulnerability to erosion, and a giant storm is able to generate more runoff and mobilize massive amounts of sediment, more than would have been mobilized under its former land cover. The very largest storms, however, can even break through the natural protections afforded by intact land cover, and great erosion can result. Volcanoes are another story. They make their own landscapes, by providing vast quantities of new, abiologic, loose material, by melting summit snow and glaciers to make raging torrents, and by creating their own weather. Rivers become debris flows and lahars; valleys and towns are buried. With the larger eruptions, former landscapes are gone and new cycles of land-cover development, weathering, and erosion must begin again; Krakatao is a famous example.

An experienced hydrologist or biogeochemist thinks with rules of thumb. How does a new watershed resemble ones that have been previously witnessed and measured in detail? Is this a flatland or a steepland? Is the water turbid? What do quick measurements such as pH and conductivity reveal about the weathering? Today, remote sensing is a fantastic tool, enabling the hydrologist or biogeochemist to develop a three dimensional view of the landscape and upstream land cover to better put a watershed into context. Complicated chemical measurement and hydrologic modeling can then be invoked to refine an analysis, but these are time consuming and expensive. The best field hydrologists and biogeochemists are often those who have studied the most landscapes in the field.

In today’s world, the least expensive data to access and use is often remote sensing – satellite images and digital elevation models. These can be used to put a landscape in context. Basic hydrologic monitoring (rainfall, stream discharge, and basic meteorological data) is essential, and water-quality monitoring (temperature, conductivity, pH, and suspended sediment) incrementally adds to an understanding of human impacts and mitigation work. An in-depth understanding (what, where, when, why, and who?), gained through chemical analyses of sediment, major constituents, nutrients, trace elements, and pesticides can range from relatively inexpensive – a few strategic samples, with sample collection guided by experience elsewhere – to expensive – comprehensive forensic studies.

Yes, and this has been a life’s interest for me. The Earth’s history is recorded in sedimentary rocks, rocks that have been deposited in the Earth’s surface environment, either under liquid water, air, or ice. There are three major flavors: clastic (deposited as particles), chemical (chemically or biologically precipitated out of material that was in solution), and organic (the accumulated soft parts of plants). Each of these classes of sediments records information about its history of erosion, transport (dispersal), and deposition. Fossils contained within these sediments provides considerable additional information. I am particularly interested in clastic sediments because the first step in their formation is erosion, and this is in turn controlled largely by bedrock composition, topographic relief (flat versus steep), temperature (cold, warm), moisture supply (limited, rain, snow, ice), and land cover. Sorting these controls is one of the enduring themes of my research.

Indigenous Amazonians conceive all beings as having been human in mythical times. In their view, human and former human beings (animal and plants) are engaged in a predatory competition for scarce or ill-distributed life forces. They consider, however, that all beings have the right to live, and that all aggression can and will be responded to with a similar or greater hostility. This results in an ethic of self-regulation that ensures an overall balance in interspecific relations. The key to their success is, therefore, a healthy respect for all living forms.

Native Amazonian peoples conceive objects as living beings possessing different degrees of consciousness, agency, intentionality and communicational skills. Some objects are thought to be full subjects capable of acting upon the world; others are thought to depend on human action to express their subjectivity. Personal objects are believed to become imbued with the soul stuff of their owners and, thus, part of their owners’ bodies. In turn, some of the objects owned by the primordial people are thought to have become part of their bodies once they were transformed into animals. Thus, objects are believed to play an important role in the fabrication of all living beings.

If we take the notion of slavery to mean the condition originating in the violent capture and removal of people from their families and societies — a condition entailing their subjection to ritual processes of desocialization and depersonification, their compulsory inclusion into the society of their captors as people without rights, and their total subjection to the power and personal whims of their masters – then slavery was indeed present in tropical America in pre-Columbian times. Amerindian slavery differed greatly, however, from slavery as practiced in colonial America in that it was a temporal condition that ended once captive slaves – or their descendants – were incorporated into their masters’ society through marriage or adoption.

Native Amazonian modes of knowledge differ from our own not because Amerindians have different intellectual capabilities than non-indigenous people, but because they often consider that “true” knowledge of the world does not depend solely on empirical observation but must be obtained through dreams, visions, and revelations. Children learn to hunt or to garden from their parents and their personal experience, but such knowledge is considered to be incomplete if it is not complemented by the knowledge acquired from the spirit owners of animals and plants. Such knowledge requires establishing contact with these beings in a spiritual plane.

In contrast with Westerners, who view personhood and humanness as identical conditions, Amerindians regard these two conditions as independent states of being that may or may not manifest together. Whereas native Amazonians consider personhood as an attribute of all living beings insofar as all of them were people in mythical times, they regard humanness as a quality pertaining to only one kind of beings: present-day human beings who are thought to be the only “true people.” This dual conception not only allows for the existence of both “non-human persons” (e.g. animals, plants, objects) and “non-person humans” (e.g. witches or humans deprived of their souls), but also admits internal distinctions in terms of degrees of humanness and personhood.

The idea that all living beings were human in primordial times and that animals, plants and objects might lash back if they feel overexploited by humans, make native Amazonian worldviews much more respectful of non-humans than is the case in Western societies, where these beings are classified as being part of “nature” and are thus amenable to being exploited, transformed and dominated without regards for their reproduction and integrity. Taking example from indigenous worldviews we should become more aware of the fact that humanity is part of nature and that its survival is inextricably tied to that of the natural world. We would then have better chances of putting a stop to the destruction of our planet and preserve it for future generations.

Many genetic traits make it possible for non-native plants to invade new environments. Knowledge of where invasive genotypes originate, how they are distributed, and how genetic diversity helps or hinders invasive species will lead to better understanding and management of biological invasions.

Soil microbes play critically important roles in ecosystem processes and the maintenance of forest diversity. Ongoing projects focus on variability in community structure of bacteria, archaea, and fungi across space and habitats using metagenomic and rRNA surveys. We work in natural forests, plantations, and agricultural landscapes to assess how land use change influences soil microbial communities and how these communities influence forest successional processes.

Analysis of DNA provides genetic, geographic and sometimes historical answers to biological questions. We work with a variety of tissues and environmental samples to tell complex stories about the distribution of species, their spread, and evolutionary histories. Using a variety of genetic and genomic techniques we explore a wide range of topics, such as genetic diversity in endangered species, the geographic origins of invaders, the influence of climate on genetic diversity, and the evolution of disease spreading parasites.