Underground Storage Organs Research Articles

Rhizome Fragmentation by Vertical Disks Reduces Elymus repens Growth and Benefits Italian Ryegrass-White Clover Crops.

Tillage controls perennial weeds, such as Elymus repens, partly because it fragments their underground storage organs. However, tillage is difficult to combine with a growing crop, which limits its application. The aim of this study was to evaluate how soil vertical cutting with minimum soil disturbance and mowing affect the growth and competitive ability of E. repens in a grass–clover crop. A tractor-drawn prototype with vertical disks was used to fragment E. repens rhizomes with minimal soil and crop disturbance. In experiments performed in 2014 and 2015 at a field site close to Uppsala, Sweden, the rhizomes were fragmented before crop sowing (ERF), during crop growth (LRF), or both (ERF+LRF). Fragmentation was combined with repeated mowing (yes/no) and four companion crop treatments (none, Italian ryegrass, white clover, and grass/clover mixture). The results showed that in the grass–clover crop, rhizome fragmentation reduced E. repens rhizome biomass production and increased Italian ryegrass shoot biomass. ERF and LRF both reduced E. repens rhizome biomass by about 38% compared with the control, while ERF+LRF reduced it by 63%. Italian ryegrass shoot biomass was increased by 78% by ERF, 170% by LRF and 200% by ERF+LRF. Repeated mowing throughout the experiment reduced E. repens rhizome biomass by about 75%. Combining repeated mowing with rhizome fragmentation did not significantly increase the control effect compared to mowing alone. We concluded that rhizome fragmentation using vertical disks can be used both before sowing and during crop growth to enhance the controlling effect of grass–clover crops on E. repens.

Diet reconstructed from an analysis of plant microfossils in human dental calculus from the Bronze Age site of Shilinggang, southwestern China

The extracted microfossils from the dental calculus of ancient teeth are a new form of archaeological evidence which can provide direct information on the plant diet of a population. Here, we present the results of analyses of starch grains and phytoliths trapped in the dental calculus of humans who occupied the Bronze Age site of Shilinggang (∼2500 cal yr BP) in Yunnan Province, southwestern China. The results demonstrate that the inhabitants consumed a wide range of plants, including rice, millet, and palms, together with other food plants which have not previously been detected in Yunnan. The discovery of various underground storage organs (USOs; tubers, roots, bulbs, and rhizomes) and acorns complements the application of conventional macrofossil and isotope studies to understand the diet of the Bronze Age human population of Yunnan. The wide variety of plant foods consumed suggests that the inhabitants adopted a broad-spectrum strategy of gathering food and cultivating crops in northwest Yunnan Province in the late Bronze Age at a time when agricultural societies were developed in the central plains of China.

Starch contamination landscapes in field archaeology: Olduvai Gorge, Tanzania

No agreement on what constitutes a safe and reproducible anticontamination protocol exists for ancient starch research. Protocols applied to laboratory work may represent ‘symptomatic treatment’ only, as contamination of archaeological materials in the field may be more extensive than realized. This paper is the first systematic study on the impact that modern starches from surface and buried soils, windborne dispersal, human motion, excavation techniques and toolkits, and field attire has on archaeological sample quality. The study area is Olduvai Gorge, Tanzania. We identify seven starch types (discrete granules, n = 788) that embody the starch contamination landscape for the region. This study also demonstrates the various diagenetic changes that buried starch granules undergo in a short time, such as cavitation, fissuring, disruption and gelatinization. There are significant differences in morphotype class representation between the topsoil starches and those collected deeper below ground at excavated sites. Diagenetically transformed granules from underground storage organs dominate in soils, while native starches from cereal endosperm (Panicoideae and Triticeae) abound above ground in airborne samples. Furthermore, we illustrate how lithic samples excavated under standard field conditions can be contaminated, and that when a sample is compromised during excavation, it may be impossible to distinguish between target and introduced starches, especially when granules are identical or morphologically similar. The paper provides field recommendations to control false positives.

Feeding habits of the crested porcupine Hystrix cristata L. 1758 (Mammalia, Rodentia) in a Mediterranean area of Central Italy

Old World porcupines are widely recorded as being agricultural pests throughout their distribution range. Despite being legally protected in Italy, the crested porcupine Hystrix cristata is extensively poached for its meat as well as for complained crop damages. In this work, we analysed the diet of crested porcupines in a Mediterranean coastal area surrounded by agricultural patches. Feeding habits of this species were assessed throughout the year through faecal analysis. Underground vegetal organs were the staple of the diet of this large rodent in both cold and warm months. Fruits were consumed mainly in cold months (hard epicarp species, e.g. acorns and pine nuts). In warm months, agricultural products, e.g. sunflowers, cereals and watermelons, were mostly consumed. Patterns of food consumption are consistent with a study on habitat selection by crested porcupine within the same study area. According to this previous study, the Mediterranean “macchia” represents a poor habitat in terms of food resources and it is selected only in cold months, when porcupines mainly feed on underground storage organs of woodland plants. During the summer, porcupines are forced to travel long distances to search for other food categories, e.g. cultivated species.

Elymus repens biomass allocation and acquisition as affected by light and nutrient supply and companion crop competition.

Competitive crops are a central component of resource-efficient weed control, especially for problematic perennial weeds such as Elymus repens Competition not only reduces total weed biomass, but denial of resources can also change the allocation pattern - potentially away from the underground storage organs that make perennial weeds difficult to control. Thus, the competition mode of crops may be an important component in the design of resource-efficient cropping systems. Our aim was to determine how competition from companion crops with different modes of competition affect E. repens biomass acquisition and allocation and discuss that in relation to how E. repens responds to different levels of light and nutrient supply. Greenhouse experiments were conducted with E. repens growing in interspecific competition with increasing density of perennial ryegrass or red clover, or growing at three levels of both light and nutrient supply. Elymus repens total biomass decreased with increasing biomass of the companion crop and the rate of decrease was higher with red clover than with perennial ryegrass, particularly for E. repens rhizome biomass. A reduced nutrient supply shifted E. repens allocation towards below-ground biomass while a reduced light supply shifted it towards shoot biomass. Red clover caused no change in E. repens allocation pattern, while ryegrass mostly shifted the allocation towards below-ground biomass, but the change was not correlated with ryegrass biomass. The companion crop mode of competition influences both the suppression rate of E. repens biomass acquisition and the likelihood of shifts in E. repens biomass allocation.

Suburban ecology of the crested porcupine in a heavily poached area: a global approach

Urban areas not only provide wildlife with new ecological niches, in terms of food availability, human protection and den sites but also they increase the possibility of conflict with man. Despite being a protected species in Italy, the crested porcupine is considered as an agricultural pest, with a tasty meat, thus widely poached. We studied food selection and other ecological factors shaping the ranging behaviour of crested porcupines in a suburban area, where a high poaching pressure could be expected. We monitored radio-tagged adult, paired crested porcupines throughout 1 year. Over 70% of individually marked porcupines were poached. Despite the local absence of predators, but in presence of poaching pressure, porcupines avoided clear moonlight nights and daylight activity, establishing dens in thorny thickets. Deciduous woodlands and shrubwood were positively selected for feeding throughout the year, while farmlands and fallows were underused. Although the crested porcupine has been confirmed as a “generalist” species in terms of food selection, with adaptations to dig underground storage organs, a strong preference for fruits and epigeal parts of plants was detected in our study. Porcupines evolved in Asia and Africa with a number of competing grazing herbivores, as well as in presence of a heavy predation risk leading to development of quills. This might have confined them to exploit roots and rhizomes as food, as well as scrub habitats for protection. Our results suggest that porcupines can revert to the use of optimal food resources, when local selective forces allow it.

The plant component of an Acheulian diet at Gesher Benot Ya‘aqov, Israel

Diet is central for understanding hominin evolution, adaptation, and environmental exploitation, but Paleolithic plant remains are scarce. A unique macrobotanical assemblage of 55 food plant taxa from the Acheulian site of Gesher Benot Ya'aqov, Israel includes seeds, fruits, nuts, vegetables, and plants producing underground storage organs. The food plant remains were part of a diet that also included aquatic and terrestrial fauna. This diverse assemblage, 780,000 y old, reflects a varied plant diet, staple plant foods, environmental knowledge, seasonality, and the use of fire in food processing. It provides insight into the wide spectrum of the diet of mid-Pleistocene hominins, enhancing our understanding of their adaptation from the perspective of subsistence. Our results shed light on hominin abilities to adjust to new environments, facilitating population diffusion and colonization beyond Africa. We reconstruct the major vegetal foodstuffs, while considering the possibility of some detoxification by fire. The site, located in the Levantine Corridor through which several hominin waves dispersed out of Africa, provides a unique opportunity to study mid-Pleistocene vegetal diet and is crucial for understanding subsistence aspects of hominin dispersal and the transition from an African-based to a Eurasian diet.

Foraging potential of underground storage organ plants in the southern Cape, South Africa

Underground storage organs (USOs) serve as a staple source of carbohydrates for many hunter-gatherer societies and they feature prominently in discussions of diets of early modern humans. While the way of life of hunter-gatherers in South Africa's Cape no longer exists, there is extensive ethnographic, historical, and archaeological evidence of hunter-gatherers' use of USOs. This is to be expected, given that the Cape supports the largest concentration of plant species with USOs globally. The southern Cape is the location of several Middle Stone Age sites that are highly significant to research on the origins of behaviourally modern humans, and this provided the context for our research. Here, we evaluate the foraging potential of USOs by identifying how abundant edible biomass is in the southern Cape, how easily it is gathered, and how nutritious it is. One hundred 5 × 5 m plots were assessed in terms of USO species and abundance. Nearly all of the sites sampled (83%) contained edible USOs and some had high concentrations of edible biomass. Extrapolating from these sites suggests that the edible USO biomass falls within the range of biomass observed in areas supporting extant hunter-gatherer communities. The nutritional content for six USO species was assessed; these contained between 40 and 228 calories/100 g. Furthermore, foraging events were staged to provide an indication of the potential return rates for the same six USOs. The target species grow near the soil surface, mostly in sandy soils, and were gathered with minimal effort. Some 50% of the foraging events conducted yielded enough calories to meet the daily requirements of a hunter-gatherer within two hours. In conclusion, we demonstrate that USOs are a readily available source of carbohydrates in the southern Cape landscape and, therefore, there is a strong possibility that USOs played a critical role in providing food for early humans.

Reforestation or conservation? The attributes of old growth grasslands in South Africa.

Deforestation as a result of burning and land conversion in the tropics and subtropics has been widely studied and active restoration of forests has been widely promoted. Besides other benefits, reforestation can sequester carbon thereby reducing CO2 emissions to the atmosphere. However, before grasslands are targeted for 'reforestation', it is necessary to distinguish whether they are ancient natural grasslands or secondary vegetation colonizing deforested areas. Here we report the results of a study comparing primary grasslands in South Africa with 4-40 year old secondary grasslands recovering from afforestation with Pinus species. Primary grasslands had significantly higher plant species richness overall, especially of forb species. Ground cover of primary grasslands was more evenly distributed among species than secondary grasslands which tended to mono-dominance. Forbs with underground storage organs (USOs) were common in primary grasslands but conspicuously absent in the recovering systems. Comparison of secondary grasslands of different ages (up to 40 years) showed negligible recovery of the original species composition. Three key features distinguish old growth primary from secondary grasslands: total and forb species numbers, evenness of species contributions to cover and the presence of USOs. Old growth grasslands also differed in their fire response, showing significant post-burn resprouting and fire-stimulated flowering in contrast to secondary grasslands. Though similar contrasting attributes of ancient and secondary grasslands have been reported in South America, more studies are needed to explore their generality in other geographical regions.This article is part of the themed issue 'Tropical grassy biomes: linking ecology, human use and conservation'.

Genetic enhancement of oil content in potato tuber (Solanum tuberosum L.) through an integrated metabolic engineering strategy.

SummaryPotato tuber is a high yielding food crop known for its high levels of starch accumulation but only negligible levels of triacylglycerol (TAG). In this study, we evaluated the potential for lipid production in potato tubers by simultaneously introducing three transgenes, including WRINKLED 1 (WRI1), DIACYLGLYCEROL ACYLTRANSFERASE 1 (DGAT1) and OLEOSIN under the transcriptional control of tuber‐specific (patatin) and constitutive (CaMV‐35S) promoters. This coordinated metabolic engineering approach resulted in over a 100‐fold increase in TAG accumulation to levels up to 3.3% of tuber dry weight (DW). Phospholipids and galactolipids were also found to be significantly increased in the potato tuber. The increase of lipids in these transgenic tubers was accompanied by a significant reduction in starch content and an increase in soluble sugars. Microscopic examination revealed that starch granules in the transgenic tubers had more irregular shapes and surface indentations when compared with the relatively smooth surfaces of wild‐type starch granules. Ultrastructural examination of lipid droplets showed their close proximity to endoplasmic reticulum and mitochondria, which may indicate a dynamic interaction with these organelles during the processes of lipid biosynthesis and turnover. Increases in lipid levels were also observed in the transgenic potato leaves, likely due to the constitutive expression of DGAT1 and incomplete tuber specificity of the patatin promoter. This study represents an important proof‐of‐concept demonstration of oil increase in tubers and provides a model system to further study carbon reallocation during development of nonphotosynthetic underground storage organs.

A new approach for identifying starch granules of wild food plants from arid western North America

Taxonomic identification of starch granules is critical to understanding dietary patterns from archaeological contexts, but achieving high levels of confidence around such identifications has been problematic. This study highlights a statistical approach to morphometric and morphological characteristics that reduces uncertainties when making comparisons to reference material. Emphasizing starch granules with eccentric hila (those produced by underground storage organs), four taxa with ethnobotanical significance were examined from arid western North America. It was determined that the frequency distributions of granule size were bimodal or otherwise non-normal, thus, requiring log-transformation prior to making comparisons of means and measures of variance. Granule sizes in the upper 10 and 20% provided the most confident differentiation of starch granules among taxa. Significant and positive correlations of starch granule size to morphological characteristics (lamellae, aggregation, longitudinal fissure, shape) suggested that small granules are less likely to exhibit diagnostic features. Using this approach, the Four Corners potato (Solanum jamesii) could be readily distinguished from the three liliaceous taxa (Erythronium grandiflorum, Calochortus nuttallii, and Fritillaria pudica) by its large granule size and maximum fissure width. Identification of starch granules from archaeological contexts, therefore, requires improved recovery methods that increase yields (sample sizes) from artifacts and the probability of including larger granules that display diagnostic characteristics.

Starch granules identification and automatic classification based on an extended set of morphometric and optical measurements

Starch granules have been found to be preserved in association with archaeological remains and their identification may provide direct botanical evidences of the plants used by ancient humans. However, subtle morphological differences between starch granules make their taxonomic identifications difficult. In order to improve the identification of these plant remains, we used an image analysis program that measures up to 123 different optical and morphological characters. With Random Forest tests we analyzed ~5000 starch granules extracted from underground storage organs (USO), seeds, and fruits of 20 different East African edible plant species. Our results show that correct identification rates are up to 74% for some species (Echinochloa colona, Cyperus rodundus), ~80% for some suprageneric taxa (Poaceae, Fabaceae), and 80% for underground storage organs. However, on average, success rates are just ~53% for species (up to 70% with a dataset reduced to herbaceous species), 60% for families, and 72% for plant parts. Yet, this automated system is not perfect, but it is still more powerful than the human eye, for which the average success rate is just of 25% for species level identifications. We evaluated the performance of our system and found that accuracy rates of identifications of starch granules are highly sensitive to the number of groups (species) to identify (r2=0.83) and, to a lesser extent to the number of characters used by the identification system (r2=0.87). It is therefore crucial to narrow down as much as possible the number of target species, by analyzing additional proxies. We conclude that better results can be achieved if the candidate field is narrowed. If not, the automated identification of starch granules will remain unsatisfactory to provide acceptable interpretations in archaeological contexts.

Post-fire resprouting oaks (genus: Quercus) exhibit plasticity in xylem vulnerability to drought

Resprouting is a key functional trait for species in disturbance prone environments. In many semi-arid environments, woody plants face both fire and drought as recurring disturbances. Past work has demonstrated that oaks inhabiting sky-island forests of the northern Sierra Madre Oriental have differing microhabitat preferences and heavy stem dieback occured during the historic 2011 drought indicating potential xylem failure. These oak species, representing two sections within the genus, are all post-fire resprouters: they can resprout from underground storage organs when fire kills above ground tissue. Resprouts provide an opportunity to examine how functional traits may change as plastic responses to changing environmental conditions. Post-fire resprouts have increased root:shoot ratios relative to adults and therefore have access to more water relative to leaf demand. We expected that if resprouts exhibit plasticity in xylem function, they should favor water transport efficiency over safety: they should have higher maximum xylem conductivity, but greater susceptibility to drought-induced cavitation. We examined four oak species common in the Davis Mountains in west Texas and compared adult physiology with that of resprouts following wildfire. We found that species differed in degree of desiccation avoidance (isohydry) consistent with microhabitat preferences and that the species that were most desiccation tolerant as adults had resprouts significantly more susceptible to xylem cavitation. We found no evidence for a trade-off between efficiency and safety, however.

Impact of meat and Lower Palaeolithic food processing techniques on chewing in humans.

The origins of the genus Homo are murky, but by H. erectus, bigger brains and bodies had evolved that, along with larger foraging ranges, would have increased the daily energetic requirements of hominins. Yet H. erectus differs from earlier hominins in having relatively smaller teeth, reduced chewing muscles, weaker maximum bite force capabilities, and a relatively smaller gut. This paradoxical combination of increased energy demands along with decreased masticatory and digestive capacities is hypothesized to have been made possible by adding meat to the diet, by mechanically processing food using stone tools, or by cooking. Cooking, however, was apparently uncommon until 500,000 years ago, and the effects of carnivory and Palaeolithic processing techniques on mastication are unknown. Here we report experiments that tested how Lower Palaeolithic processing technologies affect chewing force production and efficacy in humans consuming meat and underground storage organs (USOs). We find that if meat comprised one-third of the diet, the number of chewing cycles per year would have declined by nearly 2 million (a 13% reduction) and total masticatory force required would have declined by 15%. Furthermore, by simply slicing meat and pounding USOs, hominins would have improved their ability to chew meat into smaller particles by 41%, reduced the number of chews per year by another 5%, and decreased masticatory force requirements by an additional 12%. Although cooking has important benefits, it appears that selection for smaller masticatory features in Homo would have been initially made possible by the combination of using stone tools and eating meat.

Seasonal availability of edible underground and aboveground carbohydrate resources to human foragers on the Cape south coast, South Africa.

The coastal environments of South Africa’s Cape Floristic Region (CFR) provide some of the earliest and most abundant evidence for the emergence of cognitively modern humans. In particular, the south coast of the CFR provided a uniquely diverse resource base for hunter-gatherers, which included marine shellfish, game, and carbohydrate-bearing plants, especially those with Underground Storage Organs (USOs). It has been hypothesized that these resources underpinned the continuity of human occupation in the region since the Middle Pleistocene. Very little research has been conducted on the foraging potential of carbohydrate resources in the CFR. This study focuses on the seasonal availability of plants with edible carbohydrates at six-weekly intervals over a two-year period in four vegetation types on South Africa’s Cape south coast. Different plant species were considered available to foragers if the edible carbohydrate was directly (i.e. above-ground edible portions) or indirectly (above-ground indications to below-ground edible portions) visible to an expert botanist familiar with this landscape. A total of 52 edible plant species were recorded across all vegetation types. Of these, 33 species were geophytes with edible USOs and 21 species had aboveground edible carbohydrates. Limestone Fynbos had the richest flora, followed by Strandveld, Renosterveld and lastly, Sand Fynbos. The availability of plant species differed across vegetation types and between survey years. The number of available USO species was highest for a six-month period from winter to early summer (Jul–Dec) across all vegetation types. Months of lowest species’ availability were in mid-summer to early autumn (Jan–Apr); the early winter (May–Jun) values were variable, being highest in Limestone Fynbos. However, even during the late summer carbohydrate “crunch,” 25 carbohydrate bearing species were visible across the four vegetation types. To establish a robust resource landscape will require additional spatial mapping of plant species abundances. Nonetheless, our results demonstrate that plant-based carbohydrate resources available to Stone Age foragers of the Cape south coast, especially USOs belonging to the Iridaceae family, are likely to have comprised a reliable and nutritious source of calories over most of the year.

Impact of Brief Roasting on Starch Gelatinization in Whole Foods and Implications for Plant Food Nutritional Ecology in Human Evolution

Cooking is an important technology for its capacity to increase food digestibility, particularly for plant foods, potentially playing a significant role in human evolution to increase nutritional acquisition. However, the contextual impetus for cooking is less well understood. One mode of cooking used by modern humans is to roast food directly in an open flame fire for very brief durations. This technique may be a behavioral analogue to that of early human ancestors. Here, we provide experimental data on starch gelatinization patterns in domesticated underground storage organs and starchy fruit as a result of brief fire roasting. We employed a count-based method using light-microscopy and a semi-quantitative photometric strategy to observe the kinetic process of gelatinization. We find that brief roasting over an open fire results in low levels of starch gelatinization. These findings suggest that brief roasting may not benefit a consumer through changes to starch structure alone.

Differences in Functional Trait Distribution between Inselberg and Adjacent Matrix Floras

Inselbergs and the adjacent matrix represent extremes of different environmental conditions and should shed light on the changing allocation of plant resources across strong and abrupt resource gradients. Here I use collated life history trait data from 840 taxa found within typical insular inselberg and adjacent matrix floras from the New England Batholith region of eastern Australia. These species were sorted into guilds of specificity to the inselberg environment. Scored traits include life form, plant height, leaf area, fruit size, seed size, mono- or polycarpy, underground storage organs, regenerative/clonality, and flowering phenology. With reduced water and nutrient resources, typical of inselbergs, allocation of plant resources to vegetative reproduction and storage organs is a disadvantage. Plants restricted to inselbergs were shorter, usually polycarpic shrubs, with smaller leaves, fruits, and seeds. Flowering time was found to be earlier and reduced in length; diaspores often have dormancy and are dispersed locally in comparison to the matrix. The results show that with limited resources the creation of underground storage organs or vegetative reproduction becomes unviable on habitats characterised by shallow soil. Inselberg taxa of the study region are likely to be under greater threat than the matrix due to anthropogenic climate change.

Wild boar rooting intensity determines shifts in understorey composition and functional traits

In recent decades, the European populations of wild boar have grown substantially, as has the impact of this species, owing above all to its rooting activity. Our aim was to investigate the relationships between vascular plant understorey and wild boar rooting intensity. The questions we addressed are: does rooting intensity influence understorey species composition and diversity? Which functional traits are associated with different levels of rooting? We performed a comparative analysis of plant communities in areas with contrasting levels of rooting intensity within a Mediterranean deciduous lowland forest in central Italy. Besides comparing species composition and diversity, we tested the association between species traits and rooting levels through fourth-corner analysis. We found that contrasting levels of rooting were associated to different understorey species composition and evenness, while we observed no significant difference in species richness. In contrast with our expectations, sites with lower rooting returned i) lower evenness values and ii) a higher proportion of species characterized by traits related to resistance or response to herbivory, i.e., spinescence, clonality, endozoochory, underground storage organs, and low height values. Our findings suggest that current vegetation patterns partly depend on the legacy effect of past rooting disturbance, since the areas currently subjected to low rooting intensity were likely to be intensely rooted in the past. These areas may have developed a marked dominance of clonal thorny species that, in turn, inhibited further feeding activities by wild boar.

English

Lack of knowledge of genetic variation within cocoyam germplasm limits its effective utilization in developing ideotypes with desirable traits for various end-uses. An agro-phenotypic characterization study was therefore conducted at the Njala Agricultural Research Centre (NARC) experimental site, Sierra Leone. The aim of the study was to evaluate the level of diversity within cocoyam germplasm using factor, cluster and minimum spanning tree analyses. A total of 27 genotypes were grown in a randomized complete block design with three replications in 2013 and 2014. Forty-two agro-morphological traits measured from the genotypes were analyzed using factor analysis (FA), hierarchical cluster analysis (HCA) and minimum spanning tree (MST). Above ground, biotic stress, underground storage organ and quality traits were useful in discriminating within and between species studied. Factor analysis loaded six factors which explained 77.5% of the total agro-phenotypic variation in the dependence structure. Other factors (>6) explained the rest of the genetic variation and may not be important in cocoyam breeding programme. The dendrogram of the HCA, based on the agro-morphological traits, showed four major groups, which supports the MST and FA. This study demonstrated wide agro-phenotypic variation among cocoyam germplasm which implied their utilization in breeding program. Findings are also useful for conservation planning of cocoyam. However, further biochemical or molecular studies are needed to complement and confirm the current agro-morphological variation. Key words: Cocoyam, agro-phenotypic characterization, multivariate tools, utilization.

Indigenous edible plant use by contemporary Khoe-San descendants of South Africa's Cape South Coast

There is evidence that hunter-gatherer societies of both the Middle and the Later Stone Ages in the Cape Floristic Region (CFR) used many plant species, particularly those with underground storage organs (USOs), as sources of carbohydrate. In the CFR, USOs – mostly monocotoledon geophytes – are particularly diverse and abundant. However, little is known about which species were targeted by hunter-gatherers. Here we use, for the first time in the CFR, ethnobotanical methods to survey the use of indigenous edible plant species amongst contemporary people of Khoe-San descent, in an attempt to gain insight on hunter-gatherer resource use. Specifically we surveyed 18 participants living in rural areas around Still Bay. They identified 58 indigenous edible plant species (from a potential list of over 140). The identified species had 69 uses, almost half of which were for fruit and a quarter for vegetable foodstuffs. Plants bearing USOs comprised only 12% of uses. As a group, species that produced fruit had the highest popularity, followed by nectar producing species and lastly plants with USOs. The popularity of this last-mentioned group was largely underpinned by the strong preference for the tubers from two Cyphia species. Knowledge of edible geophytes belonging to the Iridaceae was low, despite that these species were widely documented as important carbohydrate sources in the ethnographic, historical and archaeological literature. Shrubs were the most frequent growth form 34% of edible plant species identified by the survey group. Geophytes and trees both comprised 21% of species identified. Species of Thicket Biome affinity dominated the sample (52%) followed by the Fynbos Biome (38%); wetlands contributed the remainder at 10%. The diverse array of different biomes, each with their own suite of edible plant resources, would have been important for sustaining hunter-gatherer communities on the Cape south coast. With the exception of the edible apical meristems of palmiet (Prionium serratum), which occurs rarely in the study area, the survey failed to identify species that could have formed a staple source of carbohydrate for the pre-colonial Khoe-San peoples of the Cape south coast. This is almost certainly due to the loss of hunter-gatherer lifestyles after colonisation in the 1700s and the concomitant introduction of cereal crops.