An integrative approach to species delineation incorporating different species concepts: a case study of Limnadopsis (Branchiopoda: Spinicaudata)

The unambiguous delineation and identification of species remain central problems in systematic and taxonomic studies. Species delineation depends on the data utilized and the species concept applied. In recent years, morphology‐based species delineation has been complemented by DNA sequence data, leading to an integrative taxonomy. Such integrative approaches, however, are hampered by the partial incongruence of the various data types with certain species concepts. In this study, we delineated Australian Limnadopsis species employing one mitochondrial (cytochrome c oxidase subunit I, COI) and one nuclear (elongation factor 1α, EF1α) marker and a morphological character apparently part of the specific mate recognition complex, and therefore potentially indicative of reproductive isolation. By integrating the data over various species concepts (e.g. the ‘biological’, ‘Hennigian’, ‘recognition’, ‘phylogenetic’ and ‘evolutionary’ species concepts), the delineation of most species becomes straightforward and unambiguous. Conflicts are particularly interesting as they reveal different aspects of speciation considering the various species concepts. Our study emphasizes the benefits of a truly integrative approach to taxonomy. By combining molecular data with morphological characters indicative of reproductive isolation, it is possible to delineate species integrating not only different data types, but also different underlying species concepts. Overall, 11 Limnadopsis species could be delineated, including all eight currently recognized species, and three so far undescribed species. Most species were congruently delineated under all species concepts. A strict application of the evolutionary species concept, however, would have further split L. parvispinus into two species on the basis of the COI data. In addition, Limnadopsis tatei is consistently split into two sympatrically occurring species under all applied species concepts. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 575–599.     

From Storage Compartment to Lytic Organelle: The Metamorphosis of the Aleurone Protein Storage Vacuole

Protein storage vacuoles are found in a variety of tissues butare especially abundant in the storage organs of fruits andseeds. In this review, we focus on the protein storage vacuolesof cereal aleurone. In the mature grain, these organelles arerepositories for reserve nitrogen, carbon and minerals. Followingimbibition, protein storage vacuoles of cereal aleurone changefrom storage compartments to lytic organelles. Changes in proteinstorage vacuole structure and enzymatic activity during thistransition are discussed. It is emphasized that protein storagevacuoles are poised for reserve mobilization, and that gibberellinperception by the aleurone cell initiates a signalling cascadethat promotes acidification of the vacuole lumen and activationof enzymes and transporters.Copyright 1998 Annals of BotanyCompany Protein storage vacuole, cereal aleurone, gibberellin, abscisic acid, protein body, endosperm reserves.     

ON THE NEED FOR IMPROVED PROTECTIONS OF INCAPACITATED AND NON‐BENEFITING RESEARCH SUBJECTS

In this article, it is claimed that the protective provisions for adults with impaired decision‐making capacity are misguided, insofar as they do not conclusively state whether research on this group should be permitted only as an exception, and as they arbitrarily allow for some groups to benefit from such research while others will not. Moreover, the presumed or former will of the subject is given insufficient weight, and the minimal risk standard does not make sense in this context. Because of these problems, the present guidelines allow for the possibility of vulnerable people being exploited, something that is hidden behind a guise of solidarity. Instead we need to address the real issues at stake by rewriting the present statutes. It is suggested that new guidelines should be in some continuity with earlier efforts. However, in order to protect these subjects there is additional need for appointed representatives who monitor research and for legal obligations to compensate for any injuries suffered. Without these or similar measures we won't have an adequate system in place for the protection of non‐benefiting persons who are unable to consent to research.     

Mycorrhiza modulates aboveground tri‐trophic interactions to the fitness benefit of its host plant

1. Arbuscular mycorrhiza (AM), the association of AM fungi and plant roots, may alter morphological and physiological attributes of aboveground plant parts and thereby influence plant‐associated organisms such as herbivores and their natural enemies, predators and parasitoids. 2. The interactions between AM and the players of aboveground tri‐trophic systems have mainly been considered in isolation from each other. The effects of AM on aboveground herbivore–carnivore population dynamics and the consequences to plant fitness are unknown. 3. We explored AM‐induced compensatory mechanisms for AM‐promoted proliferation of the herbivorous spider mite, Tetranychus urticae Koch, on whole bean plants, Phaseolus vulgaris L. Vegetative and reproductive plant growth, AM fungal colonisation levels, and mite densities were assessed on spider mite‐infested plants colonised or not by the AM fungus Glomus mosseae Nicol. & Gerd, and harbouring the natural enemy of the spider mites, the predatory mite Phytoseiulus persimilis Anthias‐Henriot or not. 4. AM symbiosis modulated the aboveground tri‐trophic system to the fitness benefit of the plant. AM‐increased plant productivity outweighed the fitness decrease due to AM‐promoted herbivory: at similar vegetative growth, mycorrhizal plants produced more seeds than non‐mycorrhizal plants. 5. AM‐increased spider mite population levels were compensated for by enhanced population growth of the predators and increased plant tolerance to herbivory. 6. AM‐enhanced predator performance looped back to the AM fungus and stabilised its root colonisation levels, providing the first experimental evidence of a mutually beneficial interaction between AM and an aboveground third trophic level natural enemy.     

Out of the Bassian province: historical biogeography of the Australasian platycercine parrots (Aves,Psittaciformes)

Schweizer, M., Güntert, M. & Hertwig, S. T. (2012). Out of the Bassian province: historical biogeography of the Australasian platycercine parrots (Aves, Psittaciformes). —Zoologica Scripta, 42, 13–27. Aridification from mid‐Miocene onwards led to a fragmentation of mesic biomes in Australia and an expansion of arid habitats. This influenced the diversification of terrestrial organisms, and the general direction of their radiations is supposed to have been from mesic into drier habitats. We tested this hypothesis in the platycercine parrots that occur in different habitats in Australia and also colonized Pacific islands. We inferred their temporal and spatial diversification patterns using a Bayesian relaxed molecular clock approach based on three nuclear and two mitochondrial genes and model‐based biogeographic reconstructions. The Bassian biota was found to be the centre of origin of platycercine parrots and diversification within two of their three clades coincided with the beginning of aridification of Australia. The associated habitat changes may have catalysed their radiation through adaptation to arid environments and vicariance because of the fragmentation of non‐arid habitats. The small oceanic islands of Melanesia contributed as stepping stones for the colonization of New Zealand from Australia.     

Influence of suburban edges on invasion of Pittosporum undulatum into the bushland of northern Sydney,Australia

Abstract Suburban edges are shown to exert a major influence on invasion of the native Pittosporum undulatum Vent, in dry sclerophyll bushland of northern Sydney. Transect data from fifteen urban bushland sites spanning approximately 90 years of development indicate significant increases of P. undulatum with time. Basal area, density and frequencies of plants in all size-classes increased significantly with age of adjoining development. Mean basal area at edges of old sites was 5700 times greater than in comparable bushland in larger reserve interiors. The effect of age was compounded by the greater impact of edge effects in narrower reserves of older suburbs. Basal areas and proportion of reproductive plants decreased significantly with distance into the reserve. Older sites contained larger but fewer individuals at the edge, compared with high densities of smaller plants further into the reserve, suggesting an advanced successional stage. The overall relationship of density with distance was not significant. The observed clumping of seedlings beneath canopies is consistent with previous work on seed dispersal by vectors, and enhanced seedling recruitment in safe sites. Pittosporum basal area and density reached no maximum levels with age, implying ongoing invasion. The study indicated some factors which appeared to promote the establishment of P. undulatum in the study area. Signs of fire were negatively correlated across all sites with basal area and density of P. undulatum. Human disturbance was positively correlated with the same variables. On the basis of findings in this study, some broad priorities for management of Pittosporum in urban bushland are suggested.     

Functional differences in epiphytic microbial communities in nutrient-rich freshwater ecosystems: an assay of denitrifying capacity

1. The denitrifying capacity of epiphyton was used to evaluate differences in the function of epiphytic microbial communities on submersed macrophytes in nutrient-rich freshwater ecosystems. The denitrifying capacity of epiphyton on Potamogeton perfoliatus shoots of different age and with different epiphytic abundances from a eutrophic lake was investigated in laboratory microcosms in the light and dark. Additionally, differences between epiphyton on shoots of Potamogeton pectinatus grown under different in situ nutrient and hydraulic conditions were investigated by examining their denitrifying capacity.
2. Denitrification was registered in well-developed epiphytic layers on both mature and senescent shoots in the dark, with activities 3- to 10-fold higher in the epiphytic communities of senescent shoots. No activity was detected on young shoots with sparse epiphyton or on shoots from which loosely attached epiphyton had been removed. Denitrification never occurred during illumination.
3. Even though the epiphytic abundance was similar in magnitude, the denitrifying capacity of epiphyton adapted to high nutrient loadings was about a hundred times higher than that of epiphyton adapted to lower nutrient levels. Additionally, epiphytic abundance and denitrifying capacity were higher at sites less exposed to wave turbulence or water currents, than at sites with more water turbulence.
4. The results illustrate how the hydraulic and nutrient conditions of the surrounding water affect both the quantity and function of epiphytic microbial communities in nutrient-rich freshwater ecosystems.