Using Protistan Examples to Dispel the Myths of Intelligent Design

ABSTRACT. In recent years the teaching of the religiously based philosophy of intelligent design (ID) has been proposed as an alternative to modern evolutionary theory. Advocates of ID are largely motivated by their opposition to naturalistic explanations of biological diversity, in accordance with their goal of challenging the philosophy of scientific materialism. Intelligent design has been embraced by a wide variety of creationists who promote highly questionable claims that purport to show the inadequacy of evolutionary theory, which they consider to be a threat to a theistic worldview. We find that examples from protistan biology are well suited for providing evidence of many key evolutionary concepts, and have often been misrepresented or roundly ignored by ID advocates. These include examples of adaptations and radiations that are said to be statistically impossible, as well as examples of speciation both in the laboratory and as documented in the fossil record. Because many biologists may not be familiar with the richness of the protist evolution dataset or with ID‐based criticisms of evolution, we provide examples of current ID arguments and specific protistan counter‐examples.     

Phylogenetic structure of Brazilian savannas under different fire regimes

Questions: Fire is a strong filter in fire‐prone communities and is expected to assemble closely related species when functional traits are conserved in plant lineages. Do frequent fires assemble savannas with closely related species (phylogenetic clustering)? If so, what are the clades pruned by fire in the phylogenetic trees? Are species of semi‐deciduous seasonal forests, where fires are not frequent, less related than expected by chance (phylogenetic over‐dispersion)? Are life forms conserved in the phylogeny of the species? Location: Central and SE Brazilian savannas (Emas National Park, 18°18′S, 52°54′W; Brasília, 15°56′–15°57′S, 47°53′–47°56′W and Corumbataí‐Itirapina, 22°13′–22°15′S, 47°37′–47°39′W); and close semi‐deciduous seasonal forests (in Pirenópolis, 15°45′S, 49°04′W; Brasília, 15°33′S, 47°51′W; and São Carlos, 21°55′S, 47°48′W). Methods: We recorded woody species in savannas under different fire regimes and in semi‐deciduous seasonal forests. We obtained data from the literature and from field sampling. We compared mean phylogenetic distance of species of savanna and of nearby semi‐deciduous seasonal forest sites. We obtained significance by randomizing the species among the tips of phylogenetic trees. We also assessed whether life forms were evolutionary conserved across phylogeny of the studied plants (phylogenetic signal) with tests based on the variance of phylogenetic independent contrasts. Results: Some sites of savanna under high fire frequency were characterized by phylogenetic over‐dispersion of woody species whereas, in contrast, some sites of semi‐deciduous seasonal forest were characterized by phylogenetic clustering. We found phylogenetic signals in the traits across the phylogeny of the 801 species investigated. Conclusion: Fire may have different roles in assembling plant species in Brazilian savannas than in other fire‐prone communities. We postulate that the absence of phylogenetic clustering in the cerrado is mainly due to the persistence of long‐lived resprouting species from different plant lineages.     

Acute metal stress in Populus tremula×P. alba (717‐1B4 genotype): Leaf and cambial proteome changes induced by cadmium2+

The comprehension of metal homeostasis in plants requires the identification of molecular markers linked to stress tolerance. Proteomic changes in leaves and cambial zone of Populus tremula×P. alba (717‐1B4 genotype) were analyzed after 61 days of exposure to cadmium (Cd) 360 mg/kg soil dry weight in pot‐soil cultures. The treatment led to an acute Cd stress with a reduction of growth and photosynthesis. Cd stress induced changes in the display of 120 spots for leaf tissue and 153 spots for the cambial zone. It involved a reduced photosynthesis, resulting in a profound reorganisation of carbon and carbohydrate metabolisms in both tissues. Cambial cells underwent stress from the Cd actually present inside the tissue but also a deprivation of photosynthates caused by leaf stress. An important tissue specificity of the response was observed, according to the differences in cell structures and functions.     

Phenomorphology and ecomorphological characters of Maytenus senegalensis L. Shrublands in the Iberian Peninsula: A comparison with other Mediterranean plant communities

This work sets out to establish ecomorphological and phenomorphological patterns in the constituent flora of an Iberian Maytenus senegalensis plant community in order to relate it with or separate it from other types of Mediterranean vegetation. This plant community contains tall shrubs, scrubs, palms and vines of a variety of families. Typical ecomorphological adaptations to the Mediterranean climate were observed in the community studied: an abundance of thorny species or species with tomentose leaves and photosynthetic stems, small leaves and a high presence of species with organs capable of post-fire regeneration. However, the community also showed hybrid characteristics between scrubland (predominantly malacophyllous leaves lasting 9 months on average and low biomass) and tall shrubland communities (predominance of phanerophytes up to 3 m in height, predominantly smooth bark, periodical reposition of leaves, mean lifespan of plants 25 years and mainly fleshy fruit). The community also presents an outstanding quantity of amphiphytes (29%). From a phenological point of view, the formation of buds in winter, flowering in spring, summer–autumn seed dispersal and leaf shedding in summer are typical of other Mediterranean communities, while fructification and growth lasting three seasons, as in the case of Maytenus shrubland, is not. The RVA phenophasic index (balance between reproductive and vegetative phenophases) with values of 0.4–2 shows an intermediate value between typical shrubland (0.3–1) and forest community (1–2) values. The APC index (period of phenophasic activity of the community) differentiates it from others, since it remains at 100% for seven months, three of which are winter months. Phenophasic patterns (overlapping, or not, of flower bud formation, flowering and growth) show how similar M. senegalensis shrubland is to forests because of the absence of phenophase pattern type A (characteristic in open-scrublands); in addition, we have detected a new pattern (type G), still regarded as exclusive to M. senegalensis. As regards the existence of coenomorphs (group of species with similar morpho-functional strategies), the studied community showed much greater diversity than other communities studied to date, with an Strategies Richness index (SRi) of 0.79 (11 groups covering the 14 species existing), pointing to the co-existence of a great variety of eco-phenomorphological strategies, each with a successful response to the same ecological conditions. Finally, some of the species in the community, e.g. Asparagus horridus, Chamaerops humilis and M. senegalensis, stand out because of their unique ecomorphological and phenological characteristics.     

Influence of NaCl, Cd(NO3)2 and air humidity on transpiration of Tamarix aphylla

Transpiration rates of young Tamarix aphylla (L.) Karst, plants grown in hydroponics were measured under NaCl- and Cd(NO₃)₂-stress. Transpiration rates were negatively correlated with the relative humidity of the ambient air at all NaCl concentrations investigated. Low and intermediate concentrations of Cd²⁺ (45 and 90 μ M , respectively) in the medium caused an increase in transpiration rates. This was particularly pronounced at low levels of relative humidity. At 180 μ M Cd²⁺, transpiration rates dropped, probably as a result of root damage due to Cd²⁺ toxicity. Since the transpiration rates differed by a factor of ca 3 between day and night, it is concluded that the stomata did not lose their ability to regulate transpiration under the influence of NaCl or of Cd(NO₃)₂. The transpiration behaviour of T. aphylla indicates that the effect of water vapour pressure (presented as relative humidity) on the degree of stomatal opening is small. Under conditions of ample water supply transpiration follows the evaporative demand of the ambient air and is influenced by the water uptake capacity of the root system as well as by other environmental factors, e.g. light.     

Antioxidative defense and proline/phytochelatin accumulation in a newly discovered Cd-hyperaccumulator, Solanum nigrum L.

Changes in the activity of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and the contents of malondialdehyde (MDA), chlorophyll, free proline and phytochelatins (PCs) in Solanum nigrum, the newly discovered Cd-hyperaccumulator were examined and compared with a non-hyperaccumulator Solanum melongena. It was indicated that leaf SOD and POD activity of S. nigrum was significantly higher than that of S. melongena. The Cd treatments significantly increased root SOD activity, leaf POD activity, and CAT activity and free proline content in the leaves and roots of S. nigrum. On the contrary, the Cd treatments decreased SOD activity, and did not change CAT activity in the leaves and roots of S. melongena. Moreover, there were no significant differences in free proline levels in the roots of S. melongena. These results validated that S. nigrum had a greater capacity than S. melongena to adapt to oxidative stress caused by Cd and free proline accumulation might be responsible for the tolerance of S. nigrum to Cd. Treated with 10 μg Cd g⁻¹, growth of S. nigrum and its contents of chlorophyll and MDA were basically unaffected. In contrast, there were a decrease in the growth and chlorophyll content, and an increase in MDA in the roots of S. melongena. Although lipid peroxidation was promoted in both the hyperaccumulator and non-hyperaccumulator by high Cd stress, the greater increase took place in the tissues of S. melongena. The PCs level in roots of S. nigrum was significantly lower than that of S. melongena. On the contrary, the content of leaf PCs was much higher in S. nigrum than that in S. melongena. These results further suggested that antioxidative defense in the Cd-hyperaccumulator might play an important role in Cd tolerance, and PCs synthesis is not the primary reason for Cd tolerance although PCs in S. nigrum increased significantly by Cd.