Tribulus Cistoides Research Articles

Assessment of conservation status of riparian vascular plant species in a dry season exposed flood plain area of the Incalaue river catchment, Niassa Special Reserve, Northern Mozambique

Riparian vegetation usually gets less focus in biodiversity assessments and yet species diversity is important knowledge when applying patch specific conservation value in the Niassa Special Reserve (NSR). This study assessed the composition and conservation status of riparian species in an exposed river basin downstream location. Purposive sampling was used in the selection of sites and respondents to maximize data collection. The study found 19 species belonging to 15 families with 52.63% of them having a frequency of ⩾50% in sampling plots. There were 10 species that are endemic to the sub-Sharan Africa Region. Fabaceae was the dominant family with 5 species. The species with the highest population was Flacourtia indica (Burm. f.) Merr. Species richness ranged from 0.35 to 0.98 with a mean of 0.66 ± 0.22. The IVI ranged from 34.70 (F. indica (Burm. f.) Merr) to 4.43 (Tribulus cistoides L.) with a mean of 15.79 ± 7.79. Threats of species loss and ecosystem disturbance were agriculture, infrastructure development and plant harvests. There was a reported decline in species availability over the previous 10 years by 18.7% of the respondents. The results added to existing studies and records of vegetation species of conservation value in areas exposed to loss in the NSR. This study advances research on vegetation range dynamics in the NSR and presents a need to mitigate human land use impacts on riparian vegetation species composition.

Phenotypic divergence of traits that mediate antagonistic and mutualistic interactions between island and continental populations of the tropical plant, Tribulus cistoides (Zygophyllaceae).

Island systems have long served as a model for evolutionary processes due to their unique species interactions. Many studies of the evolution of species interactions on islands have focused on endemic taxa. Fewer studies have focused on how antagonistic and mutualistic interactions shape the phenotypic divergence of widespread nonendemic species living on islands. We used the widespread plant Tribulus cistoides (Zygophyllaceae) to study phenotypic divergence in traits that mediate antagonistic interactions with vertebrate granivores (birds) and mutualistic interactions with pollinators, including how this is explained by bioclimatic variables. We used both herbarium specimens and field-collected samples to compare phenotypic divergence between continental and island populations. Fruits from island populations were larger than on continents, but the presence of lower spines on mericarps was less frequent on islands. The presence of spines was largely explained by environmental variation among islands. Petal length was on average 9% smaller on island than continental populations, an effect that was especially accentuated on the Galápagos Islands. Our results show that Tribulus cistoides exhibits phenotypic divergence between island and continental habitats for antagonistic traits (seed defense) and mutualistic traits (floral traits). Furthermore, the evolution of phenotypic traits that mediate antagonistic and mutualistic interactions partially depended on the abiotic characteristics of specific islands. This study shows the potential of using a combination of herbarium and field samples for comparative studies on a globally distributed species to study phenotypic divergence on island habitats.

Urbanization alters interactions between Darwin's finches and Tribulus cistoides on the Galápagos Islands.

Emerging evidence suggests that humans shape the ecology and evolution of species interactions. Islands are particularly susceptible to anthropogenic disturbance due to the fragility of their ecosystems; however, we know little about the susceptibility of species interactions to urbanization on islands. To address this gap, we studied how the earliest stages of urban development affect interactions between Darwin's finches and its key food resource, Tribulus cistoides, in three towns on the Galápagos Islands. We measured variation in mericarp predation rates, mericarp morphology, and finch community composition using population surveys, experimental manipulations, and finch observations conducted in habitats within and outside of each town. We found that both seed and mericarp removal rates were higher in towns than natural habitats. We also found that selection on mericarp size and defense differed between habitats in the survey and experimental populations and that towns supported smaller and less diverse finch communities than natural habitats. Together, our results suggest that even moderate levels of urbanization can alter ecological interactions between Darwin's finches and T. cistoides, leading to modified natural selection on T. cistoides populations. Our study demonstrates that trophic interactions on islands may be susceptible to the anthropogenic disturbance associated with urbanization. Despite containing the highest diversity in the world, studies of urbanization are lacking from the tropics. Our study identified signatures of urbanization on species interactions in a tropical island ecosystem and suggests that changes to the ecology of species interactions has the potential to alter evolution in urban environments.

The role of spines in anthropogenic seed dispersal on the Galápagos Islands.

Dispersal has important ecological and evolutionary consequences for populations, but understanding the role of specific traits in dispersal can be difficult and requires careful experimentation. Moreover, understanding how humans alter dispersal is an important question, especially on oceanic islands where anthropogenic disturbance through species introductions can dramatically alter native ecosystems.In this study, we investigated the functional role of spines in seed dispersal of the plant caltrop (Tribulus cistoides L., Zygophyllaceae) by anthropogenic dispersal agents. We also tested whether humans or wildlife are more important seed dispersers of T. cistoides on the Galápagos. Tribulus cistoides is found on tropical mainland and oceanic island habitats. The dispersal structure of T. cistoides is called a mericarp, and they are typically protected by one pair of upper spines and a second pair of lower spines, but the presence and size of spines varies within and between populations. On the Galápagos, the upper and lower spines protect mericarps from seed predation by Darwin's finches. We tested whether spines play a dual role in dispersal by factorially manipulating the presence/absence of the upper and lower spines to simulate natural variation in mericarp morphology.The upper spines greatly facilitated seed dispersal, whereas the lower spines had no discernible effect on dispersal. The presence of upper spines increased dispersal rate on shoes by pedestrians 23‐fold, on fabrics (e.g., towels) and cars by nearly twofold, and the presence of upper spines increased dispersal distance by cars sixfold. When comparing dispersal rates in habitats with high (roads and foot paths) versus low (arid forest) anthropogenic activity, dispersal rates were demonstrably higher in the habitats with more human activity.These results have important implications for understanding the ecology and evolution of plant dispersal in the Anthropocene. Spines on the fruits of T. cistoides play important functional roles in anthropogenic dispersal, whereas native and introduced wildlife plays a minor role in dispersal on inhabited islands of the Galápagos. Our results imply that seed predators and humans are jointly shaping the ecology and evolution of contemporary populations of T. cistoides on the Galápagos.

Climate and Vegetation Changes at Coringa-Herald National Nature Reserve, Coral Sea Islands, Australia

Climatic changes at Coringa-Herald National Nature Reserve (CHNNR) in the last 82 yr include a 0.7°C rise in mean minimum winter temperatures and increases in drought duration and frequency. Between 1991 and 2002, a plague of the scale insects Pulvinaria urbicola (Cockerell), together with attendant ants destroyed Pisonia grandis R.Br, rain forest at South-West Coringa Islet. Scale insect damage of P. grandis has also been recorded at North-East Herald Cay. This study explored the reasons for vegetation dieback during current climate. Woody species such as Argusia argentea (L.) Heine, Cordia subcordata Lam., and the grasses Lepturus repens (G. Forst.) R.Br. and Stenotaphrum micranthum (Desv.) C. E. Hubb. have also declined at CHNNR. Ximenia americana L. and Digitaria ctenantha (F. Muell.) Hughes were found to be locally extinct. Dieback of forests results in reduction of canopy-breeding seabirds and burrowing shearwaters (Puffinus pacifiais [Gmelin)]. Dieback species were replaced by the shrub Abutilon albescens Miq. and/or fleshy herbaceous plants such as Achyranthes aspera L., Boerhavia albiflora Fosberg, Ipomoea micrantha Roem. & Schult, Portulaca oleracea L., and Tribulus cistoides L. Increasing duration of droughts and increased temperatures, together with damage caused by exotic insect pests, appear to be the key drivers of the current vegetation changes.

Composition and Seasonality of Diet in Wild Hamadryas Baboons: Preliminary Findings from Filoha

Here we report the first year-round quantitative data on dietary composition and seasonality in wild hamadryas baboons. Study subjects were adult male members of band 3 at the Filoha field site in central lowland Ethiopia. Data collection consisted of 10-min focal samples during all-day follows 4–6 days per month over the course of 1 year. The two largest contributors to the diet were Hyphaene thebaica and Acacia senegal, and these were the only plant species found in the diet during every month of the year. Other relatively major contributors to the diet, such as Cyperus grandibulbosus, Seddera bagshawei, Tribulus cistoides and Typhalatifolia, showed a seasonal pattern. Fewer plant species were consumed during the dry months of the year compared to the wet months. During the hottest and driest months of the year, study subjects subsisted almost exclusively on H. thebaica, A. senegal, C. grandibulbosus and T.latifolia. Overall, these patterns suggest that this population of hamadryas baboons spends less time feeding and is able to subsist on a narrower array of plant foods compared to other baboons. This pattern may be driven by the presence at Filoha of the doum palm (H. thebaica), a high-quality food resource that is consumed year-round.

New cardioactive steroid saponins and other glycosides from Mexican Tribulus cistoides.

The genus Tribulus of the Zygophyllaceae comprises about 20 species which grow as shrubs or herbs in subtropical areas around the world1,2. Among the Tribulus species, only T. terrestris has been investigated phytochemically3–6. This plant is known in South Africa and the USA to be toxic for sheep and causes major economic damage2,7. On the other hand, T. terrestris is used in Ayurvedic medicine against various diseases8 and its extract constitutes the active component of a medicine traded in Bulgaria9,10.

Cardioactive steroid saponins and other constituents from the aerial parts of tribulus cistoides

From the petrol extract of the aerial parts of Tribulus cistoides three steroid sapogenins and two N-acyltyramines were isolated, whereas the methanolic extract gave nine steroid saponins, among them the cardioac- tive cistocardin, saponin-3, saponin-4 and saponin-7. Furthermore, a furostanol diglycoside was isolated besides 5′-(hydroxysulphonyloxy) jasmonic acid, d-(+)-pinitol and sucrose. The structures were established by spectroscopic investigations of the isolated compounds and their hydrolysis products. 5′-(Hydroxysulphonyloxy) jasmonic acid has been prepared by partial synthesis.

Diet Variation in a Population of Darwin's Finches

I studied the diets of a banded population of Darwin's Medium Ground Finches (Geospiza fortis) on Isla Daphne Major, Galapagos, between 1979 and 1981. I was able to show how an individual's diet was constrained to a subset of the foods that the population as a whole exploits, and considered how an individual selected from among the foods available to it. I examined both the evolutionary and short—term constraints on diet in the population. During times of food shortage there are essentially three food types on the island. These are small seeds, derived from several plant species, which are soft and easy for finches to handle, and two large seeds, derived from the cactus Opuntia echios and a semiannual plant Tribulus cistoides. The smallest finches are unable to crack the large seeds, while among those that crack large seeds, there are positive associations of seed handling ability and beak size. Generalization on all three seed types at the population level and some specialization of individuals on large or small seeds help to explain the high level of morphological variability observed in the population. Within the large—seed category some individuals specialized on Opuntia or Tribulus seeds, whereas others consumed both. Energy rewards from foraging on either seed appeared to be similar. Individuals did not behave in a manner suggesting that they were attempting to maximize energy returns when foraging on these seeds. Specialization on Opuntia or Tribulus is attributable to the patchy distribution of seeds on the island, and to a host of constraints on foraging, including microclimate and territorial behavior. If feeding abilities on each of the three seed types are considered as separate characters, then the joint evolution of the three feeding behaviors is tightly constrained through beak morphology, known to be highly heritable. This in turn implies high genetic correlations between the three feeding behaviors.

Vesicular-Arbuscular Mycorrhizal Associations of Vascular Plants on Heron Island, a Great Barrier Reef Coral Cay

Roots of 42 species of angiosperms collected from all vegetation zones on Heron Island were cleared, stained with chlorazol black E and assessed for vesicular-arbuscular mycorrhizae (VAM). Percentage of root length colonized was determined using the gridline intersect method, while stages in internal development of the mycorrhizal association were determined by mounting cleared root pieces on microscope slides and examining them with Nomarski differential interference contrast microscopy. Fifty-seven percent of the species had VAM and of these the percentage of root length colonized varied from 3 to 100%. There were no statistically significant differences among the four vegetation zones of the island in the number of species colonized. About the same proportion of trees and shrubs had VAM as did the herbs. Two species of Brassicaceae, Lepidium virginicum and Sisymbrium orientale, had VAM. All but three species with VAM had both arbuscules and vesicles; arbuscules were not found in Casuarina equisetifolia var. incana, Sisymbrium orientale and Tribulus cistoides.

The feeding of darwin's finches on Tribulus cistoides (L.) seeds

Food-handling skills of finches vary as a function of bill size. Geospiza magnirostris crush and shatter the woody mericarps of caltrop ( Tribulus cistoides) to reach the seeds, whereas G. fortis (a smaller species) bite and tear at them. G. magnirostris accept and crack most of the mericarps picked up; fortis reject most mericarps but often feed on fragments. Energy rewards are greater for magnirostris than for fortis. Intraspecific variation in handling skills parallels interspecific variation. G. fortis individuals with large bills spend more time on mericarps and extract more seeds than do those with small bills, and they reject mericarps with a lower frequency. Those observed feeding on seeds from Tribulus mericarps were larger, particularly in bill size, than those not observed feeding on them.

Annual variation in Finch numbers, foraging and food supply on Isla Daphne Major, Gal�pagos

(1) We report some effects of an annually variable and unpredictable rainfall upon Darwin's Finches on the Galápagos. Finch numbers, foraging and food supply were studied on I. Daphne Major in December of 1973 and 1977, and compared. 1973 was the second of two successive wet years and 1977 was a drought year. (2) Seed numbers and biomass were approximately one order of magnitude lower in the drought year than in the wet year. Small and soft seeds were absolutely and relatively rarer in the drought year than in the wet year. (3) Similarly finch numbers and biomass were approximately one order of magnitude lower in the drought year than in the wet year. Numbers of G. scandens declined less than did number of G. fortis. Both species exhibited unabalaced sex ratios, in favour of males, in the dry year in contrast to balanced sex ratios in the wet year. Male scandens were heavier on average in the wet year, but male fortis were heavier in the dry year. (4) The foraging of scandens, a cactus (Opuntia) specialist, was similar in the two years. The foraging of fortis in the dry year differed from foraging in the wet year in three important respects: fortis devoted a disproportionate amount of time to feeding on small seeds while tending to avoid seeds of Opuntia, they fed more on floral and extra-floral parts of Opuntia and they fed on Tribulus cistoides, a large and hard fruit which was absent from their diet in the wet year. As a consequence of feeding more on Opuntia, fortis foraging was more similar to scandens foraging in the dry year than in the wet year. (5) The results are discussed in relation to expectations from competition theory. The decline in numbers in relation to a decline in food supply was expected, but a convergence in diets was not. The convergence is attributed to the recent renewal of a single resource, Opuntia flowers, against a background of general resource scarcity. Diet overlap and limitation of numbers by food provide indirect evidence of interspecific competition; scandens, with an included niche, was competitively superior to fortis.