Gene dispersal (flow, or migration) within and between plant populations has been of continuous interest to plant breeders and seed producers for many decades. Economic considerations have stimulated studies of gene flow as a function of distance, breeding system, pollinating agent, and planting design in numerous domestic plants. Only during the past two decades have a large body of plant evolutionists become interested in information accruing from these studies, and in the rates of gene flow in wild populations. Their efforts have concentrated primarily on related problems such as adaptations for and mechanics of pollen and seed (or fruit) dispersal, plant-pollinator coevolution, adaptive radiation in pollination and seed dispersal mechanisms, and colonization and the alteration of species boundaries. Early in this century, anecdoctal evidence on the movement of pollen and seed vectors, dispersal of pollen by wind, and the range extensions of weed species led to the casual assumption that gene flow must be extensive, and that it must play a major role in the cohesion of populations and population systems. This view eroded as more information became available and was more critically interpreted (e.g., Grant, 1958, 1971; Ehrlich and Raven, 1969; Stebbins, 1970a; Bradshaw, 1972).

Gene Flow in Seed Plants

Forest fires are growing in size and frequency across the tropics. Continually eroding fragmented forest edges, they are unintended ecological disturbances that transcend deforestation to degrade vast regions of standing forest, diminishing ecosystem services and the economic potential of these natural resources. Affecting the health of millions, net forest fire emissions may have released carbon equivalent to 41% of worldwide fossil fuel use in 1997-98. Episodically more severe during El Nino events, pan-tropical forest fires will increase as more damaged, less fire-resistant, forests cover the landscape. Here I discuss the current state of tropical fire science and make recommendations for advancement.

Fire science for rainforests

Tropical blackwater rivers, animals, and mast fruiting by the Dipterocarpaceae

The incidence and importance of fire in the Amazon have increased substantially during the past decade, but the effects of this disturbance force are still poorly understood. The forest fire dynamics in two regions of the eastern Amazon were studied. Accidental fires have affected nearly 50 percent of the remaining forests and have caused more deforestation than has intentional clearing in recent years. Forest fires create positive feedbacks in future fire susceptibility, fuel loading, and fire intensity. Unless current land use and fire use practices are changed, fire has the potential to transform large areas of tropical forest into scrub or savanna.

Investigating positive feedbacks in the fire dynamic of closed canopy tropical forests.

https://science.sciencemag.org/content/sci/284/5421/1832.full.pdf

Positive feedbacks in the fire dynamic of closed canopy tropical forests

Tropical Forest Ecosystems in Africa and South America: A Comparative Review

T HE relationship of culture to environment is one of the oldest problems in the science of anthropology and has provided a leading source of controversy. Early students, impressed with the ways in which cultures were adjusted to the unique features of their local environments, developed the concept of environmental determinism. As more field work was done by trained observers, the variability in culture patterns became more evident and the idea of determinism was rejected. Then, as individual cultures were grouped into culture areas and recognized as specific manifestations of a general pattern, the role of environment once again compelled attention. Wissler (1926:214) expressed the correspondence that exists between culture areas and "natural" areas in the form of a law: " . . . when two sections of a continent differ in climate, florae and faunae, or in their ecological complexes, the culture of the tribal groups in one section will differ from that in the other." In the last two decades this situation has been examined in broad-scale analyses (Forde 1934; Kroeber 1939) and detailed field studies (Steward 1938) and the relationship between environment and culture has been clarified to such an extent that Coon (1948:614) could phrase it recently in more causal terms than Wissler could use two decades before: "Differences in environment . . . are the chief if not the only reason why historical changes have proceeded at different rates in different places, and why more complicated systems have not diffused more rapidly from centers of development." There are few anthropologists today who would disagree with the general statement that environment is an important conditioner of culture. However, efforts to establish the relationship more specifically seem to give negative results. The potentialities of a particular habitat can be seen reflected in the subsistence pattern, the material culture, and by extension, in the social and religious aspects of the culture that is exploiting it, but when cultures of similar subsistence patterns or general features are compared they are not found to occupy similar environments. Hunting tribes, for example, may live in semideserts, swamps, forests, grasslands, or mountains, and in the arctic, the tropics or the temperate zone. Conversely, areas that seem similar geographically may differ greatly culturally. This has led to the conclusion expressed by Forde (1934:464):

https://anthrosource.onlinelibrary.wiley.com/doi/pdf/10.1525/aa.1954.56.5.02a00060

Environmental Limitation on the Development of Culture1

Chapter 1 Preface to the Revised Edition Chapter 2 Preface to the Original Edition Chapter 3 Introduction Chapter 4 1. The Ecosystem Chapter 5 2. Aboriginal Adaptation to the Terra Firme Chapter 6 3. Adaptive Aspects of Terra Firme Culture Chapter 7 4. Aboriginal Adaptation to the Varzea Chapter 8 5. Amazonia in the Modern World Chapter 9 6. The Evolutionary Significance of Adaptation Chapter 10 Epilogue: Recent Developments Chapter 11 Selected References Chapter 12 Glossary Chapter 13 Index

Amazonia: Man and culture in a counterfeit paradise

The Peoples and Cultures of Ancient Peru

Recent recognition of teleconnections between El Nino and climatic anomalies elsewhere on the planet identify northern lowland South America as a region experiencing drought Extensive archeological survey along the major tributaries of the Amazon during the past 15 years has defined the temporal and spatial distributions of numerous ceramic phases and traditions An unexpected result has been identification of discontinuities in most local sequences Large numbers of carbon-14 dates establish their contemporaneity ca 1500, 1000, 700, and 400 BP These dates correlate closely with archeological evidence on the north coast of Peru for destructive mega-Nino events Observations of the impact of milder recent episodes on the flora and fauna imply catastrophic deterioration in local subsistence resources during prehistoric events, forcing the repeated human dispersals reflected in the linguistic and genetic heterogeneity of surviving indigenous lowland South American populations

Betty J. Meggers

Papers

Tropical Forest Ecosystems in Africa and South America: A Comparative Review

Environmental Limitation on the Development of Culture1

Amazonia: Man and culture in a counterfeit paradise

The Peoples and Cultures of Ancient Peru

Archeological evidence for the impact of mega-Niño events on Amazonia during the past two millennia