Gary Paul Nabhan

Seed dispersal: Directed deterrence by capsaicin in chillies

The primary function of ripe, fleshy fruit is to facilitate seed dispersal by attracting consumers, yet many fruits contain unpleasant-tasting chemicals that deter consumption by vertebrates. Here we investigate this paradox in the chilli (Capsicum) and find that capsaicin, the chemical responsible for the fruits peppery heat, selectively discourages vertebrate predators without deterring more effective seed dispersers.

Trumpet Flowers of the Sonoran Desert: Floral Biology of Peniocereus Cacti and Sacred Datura

The floral biology of night‐blooming Peniocereus cacti and Datura plants was studied in North Americas Sonoran Desert. In populations of two rare cactus species (Peniocereus greggii and Peniocereus striatus), individual plants bloom synchronously on less than five nights per year and are self‐incompatible. In contrast, the abundant Datura discolor and Datura wrightii bloom nearly continuously from spring to autumn and are self‐compatible. Flowers of all species studied are visited by hawk moths at dusk and by honeybees and native bees the following morning. Hawk moths have the appropriate behavior and body dimensions to pollinate Peniocereus effectively, but visits are rare. Nonnative honeybees also visit P. greggii and may contribute incrementally to fruit set. Peniocereus and Datura flowers are highly reflective at all wavelengths above 400 nm but lack UV reflectance or contrast. All species studied secrete 10–80 μL of sucrose‐rich nectar within flared corollas so deep that moths must land within them, ensuring pollen carriage. These flowers provide rich energetic resources for hawk moths because the caloric content of a single flower would support from 3 to 20 min of hovering flight. Floral scents were more species specific than visual cues because D. discolor and D. wrightii emit complex blends of terpenoid, benzenoid, aliphatic, and nitrogenous scent compounds, whereas flowers of P. greggii produce only eight benzenoid compounds (all of which are present in Datura species) and Peniocereus striatus is scentless. Peniocereus cacti may benefit from sequential mutualism with the more abundant Datura species by way of pollinators nurtured as larvae by Datura foliage and as adults by Datura floral nectar.

The importance of Olneya tesota as a nurse plant in the Sonoran Desert

. The function of Olneya tesota (ironwood) as a nurse plant and habitat modifier species in the Sonoran Desert was evaluated at five study sites (using 75 250-m2 sample plots) from Bahia Kino, Sonora to Organ Pipe Cactus National Monument, Arizona. Beneath the canopy of O. tesota trees 75 perennial plant species were found. A principal component ordination of the plots created three groups: southern, perturbed and protected sites. A strong triple association of columnar cacti, big shrubs with berry type fruits and O. tesota was detected. The relationships of Lophocereus schottii and Peniocereus striatus with O. tesota were studied in more detail. Significant differences in soil surface temperatures and stem temperatures of P. striatus were detected beneath the shade of O. tesota trees compared with soils and plants in open spaces. Olneya tesota must be considered as a habitat modifier species with ecological and conservational importance to the plant communities in the Sonoran Desert.

Teparies in southwestern North America

Ethnohistorically, wild and domesticated teparies (Phaseolus acutifolius: Leguminosae) are significant native food crops in southwestern North America. Their value rests in adaptations to arid environments, and high protein content and productivity. Use of wild teparies appears to be discontinued, but certain domesticated varieties are still grown by local commercial and subsistence farmers. The recent subsidence of tepary cultivation is related to breakdown of traditional economies and land use, and to the introduction of energy-intensive irrigated agriculture. An earlier and unsuccessful attempt to introduce teparies into modern agriculture was poorly timed. Teparies have considerable potential for low maintenance agriculture in arid and semi-arid lands.

Multiple lines of evidence for the origin of domesticated chili pepper, Capsicum annuum, in Mexico.

Significance The novelty of the information of this manuscript resides in the addition of species distribution modeling and paleobiolinguistics data, combined with genetic and existing archaeobotanical data, to trace back the geographic origin of a crop, namely domesticated pepper, Capsicum annuum. Furthermore, the utilization of a geographic framework of reference for the four types of data has allowed us to combine these independent data types into a single hypothesis about the origin of this crop. Our results suggest that food crops in Mexico had a multiregional origin with chili pepper originating in central-east Mexico, maize in the Balsas River Basin and common bean in the Lerma–Santiago River Basin, resembling similar finds for the Fertile Crescent and China. The study of crop origins has traditionally involved identifying geographic areas of high morphological diversity, sampling populations of wild progenitor species, and the archaeological retrieval of macroremains. Recent investigations have added identification of plant microremains (phytoliths, pollen, and starch grains), biochemical and molecular genetic approaches, and dating through 14C accelerator mass spectrometry. We investigate the origin of domesticated chili pepper, Capsicum annuum, by combining two approaches, species distribution modeling and paleobiolinguistics, with microsatellite genetic data and archaeobotanical data. The combination of these four lines of evidence yields consensus models indicating that domestication of C. annuum could have occurred in one or both of two areas of Mexico: northeastern Mexico and central-east Mexico. Genetic evidence shows more support for the more northern location, but jointly all four lines of evidence support central-east Mexico, where preceramic macroremains of chili pepper have been recovered in the Valley of Tehuacán. Located just to the east of this valley is the center of phylogenetic diversity of Proto-Otomanguean, a language spoken in mid-Holocene times and the oldest protolanguage for which a word for chili pepper reconstructs based on historical linguistics. For many crops, especially those that do not have a strong archaeobotanical record or phylogeographic pattern, it is difficult to precisely identify the time and place of their origin. Our results for chili pepper show that expressing all data in similar distance terms allows for combining contrasting lines of evidence and locating the region(s) where cultivation and domestication of a crop began.

Native crop diversity in Aridoamerica: Conservation of regional gene pools

Scholars have seldom considered the native crop diversity in northwest Mexico and the U.S. Southwest as resources of the same cohesive ecological and cultural region. The term Aridoamerica is introduced to describe this overlooked center of plant domestication and diversification, which is distinct from centers of Mesoamerica and the Mississippi Valley. To understand why certain of its landraces are unique, the systematic relationships and gene-pool relations of crops found prehistorically and protohistorically in Aridoamerica are reviewed. Signifcant crop/ weed introgression continues where indigenous agriculture persists, but native fields are being rapidly abandoned or converted. In planning in situ and ex situ conservation efforts to maintain this diversity, both cultural factors and plant population genetics must be considered.

Living fencerows of the Rio San Miguel, Sonora, Mexico: Traditional technology for floodplain management

In southwestern North America, agriculture is limited by both arable land and available water supplies. In the upper Rio San Miguel, as well as in other narrow river valleys of eastern Sonora, Mexico, floodplain farming is dependent upon living fencerows for its environmental stability. Propagated fencerows of willow and cottonwood maintain, extend, and enhance floodplain fields. These ecological filters also protect fields from cattle, harbor agents of biological control of pests, and provide renewable supplies of wood. Traditional Sonoran farmers do not perceive cottonwoods and willows as phreatophytic pests, as their Anglo-American neighbors do. The stability of the upper San Miguelagroecosystem con-trasts with severely eroded conditions within the regions other arid watersheds.

Genetic diversity and similarity revealed via molecular analysis among and within an in situ population and ex situ accessions of chiltepín (Capsicum annuum var. glabriusculum)

Molecular analysis of genetic diversity amongand within phenotypically similar wild Capsicum annuum var. glabriusculum(chile) populations revealed geneticdifferences among accessions spread over abroad geographic range. These chiles areregionally known as chiltepíns and are a 50metric ton per year wild harvest for the spiceindustry, as well as a genetic resource forcrop improvement. Understanding geneticvariability in this species providesinformation related to conservation efforts. The objective of this research was to surveygenetic diversity among and within an insitu population and ex situ accessionsof chiltepíns. Random AmplifiedPolymorphic DNA (RAPD) molecular markers wereused to study the genetic structure of an in situ population found at the nothernmostrange of this species and ex situaccessions collected from Mexico and Guatemala. Novel genetic variation was found in both thein situ northern disjunct population, aswell as some ex situ accessions, thussupporting conservation of this species viaboth in situ and ex situ strategies The evidence presented here supports effortsto conserve outlier populations via insitu management practices.

The ecology of floodwater farming in arid southwestern North America

Abstract Floodwater farming is the management of sporadic flashfloods for crop production. It is an ancient technique in the arid southwestern region of North America that is currently being reevaluated and adapted. Floodwater-based agro-ecosystems function via (1) hydrostatic manipulations of the physical environment, and (2) synecological manipulations of the plant community. Agronomically productive hydrostatic conditions have been developed by geomorphological alteratiions of the floodplain, including canals, terraces, grids, spreaders, and weirs. These environmental modifications serve to (1) concentrate the runoff from a larger watershed into a strategically located field, and (2) break the erosive force of the incoming water. Traditional floodwater farming in arid America has depended upon ephemeral, drought-avoiding and heat-tolerant genotypes. In addition, native Americans manipulate the wild and weedy flora of floodwater fields by discouraging or protecting and harvesting selected species. As part of traditional subsistence, floodwater farming has undergone a demise in native communities. Techniques are, however, being modified for (1) forage production, and (2) supplemental human food production. As a high risk system, floodwater agriculture is not now competitive with conventional irrigation agriculture in arid lands, but may become so as groundwater pumping costs continue to affect crop production economics.

Agrobiodiversity Change in a Saharan Desert Oasis, 1919–2006: Historic Shifts in Tasiwit (Berber) and Bedouin Crop Inventories of Siwa, Egypt

This study of changes in agrobiodiversity documents the domesticated species and, to a limited degree, the landraces, cultivated in the Siwa oasis of Egypt in 1919, 1924, 1968–1969, and 2004–2006. Siwa is eco-geographically and culturally isolated by more than 300 kilometers (km) from other agrarian communities and, perhaps because of this, detailed observations were made there by a number of agricultural scientists and geographers in a way that provides time-series data lacking from many other agrarian landscapes. Although I have drawn upon Siwan names for crops first published in 1890, this report may be the first substantive record of Tasiwit (Eastern Berber) folk names for traditional crops that allows ethno-linguistic comparisons with Cairene Arabic and other Northern Berber (Tamazight) dialects in North Africa. The perennial crop inventory of Siwan Berbers has remained relatively stable through time and few traditionally cultivated annual species or landraces have been lost. However, additional crop species from other parts of Egypt have been adopted since a paved road was completed to Siwa in 1986 and more Awlad Ali Bedouins have settled and begun dooryard gardens. The reasons for the relative stability of Siwan agrobiodiversity are discussed, and may relate to both the need for crop ecotypes adapted to the challenging alkaline conditions found in Siwan agroecosystems and Siwan pride in and adherence to its traditional cuisine.