Branching out: a remarkable new branching syllid (Annelida) living in a Petrosia sponge (Porifera: Demospongiae)

We describe the morphology and biology of a previously unknown form of branching annelid, Ramisyllis multicaudata gen. et sp. nov. , an endosymbiont of shallow‐water marine sponges (Petrosia sp., Demospongiae) in northern Australia. It belongs to the polychaete family Syllidae, as does Syllis ramosa McIntosh, 1879, the only other named branching annelid, which was collected from deep‐water hexactinellid sponges during the 1875 Challenger expedition. It differs from S. ramosa in parapodial and chaetal morphology. Ramisyllis multicaudata gen. et sp. nov. has segments of several types, including specialized posterior segments on the emergent portions of the worm, and simplified elongate segments that bridge larger cavities in the sponge interior. Aside from the obvious branching form, the new annelid is similar to Parahaplosyllis, differing from it in lacking pharyngeal armature and in the details of the parapodial chaetae and dorsal cirri. Molecular evidence from 16S and 18S rDNA supports a sister‐group relationship with Parahaplosyllis, with both being sister to Trypanosyllis and Eurysyllis. The phylogenetic position of R. multicaudata gen. et sp. nov. indicates that branching has evolved independently in Ramisyllis gen. nov. and Syllis. This is supported by differences in the branching process between the two taxa: in S. ramosa branching is initiated by segment addition at the parapodium, whereas in R. multicaudata gen. et sp. nov. segments are added from a region between parapodia. A model for branching in R. multicaudata gen. et sp. nov. is proposed and possible developmental processes underlying branching in Annelida, and body symmetry comparisons with other invertebrates, are also discussed. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164 , 481–497.     

Do exotic pine plantations favour the spread of invasive herbivorous mammals in Patagonia?

Changes in land use patterns and vegetation can trigger ecological change in occupancy and community composition. Among the potential ecological consequences of land use change is altered susceptibility to occupancy by invasive species. We investigated the responses of three introduced mammals (red deer, Cervus elaphus; wild boar, Sus scrofa; and European hare, Lepus europaeus) to replacement of native vegetation by exotic pine plantations in the Patagonian forest‐steppe ecotone using camera‐trap surveys (8633 trap‐days). We used logistic regression models to relate species presence with habitat variables at stand and landscape scales. Red deer and wild boar used pine plantations significantly more frequently than native vegetation. In contrast, occurrence of European hares did not differ between pine plantations and native vegetation, although hares were recorded more frequently in firebreaks than in plantations or native vegetation. Presence of red deer and wild boar was positively associated with cover of pine plantations at the landscape scale, and negatively associated with mid‐storey cover and diversity at the stand scale. European hares preferred sites with low arboreal and mid‐storey cover. Our results suggest that pine plantations promote increased abundances of invasive species whose original distributions are associated with woodlands (red deer and wild boar), and could act as source or pathways for invasive species to new areas.     

The major diversity centre for Neotropical Turneraceae

The Neotropical country where the Turneraceae are best represented is Brazil; 82% of the American species are native, and 73% of them are endemic to this country. The most diverse states are Bahia, Minas Gerais and Goiás. Within this area the diversity – in terms of number of species – was analysed at a level of one degree square, taking into account the phytogeographic domains (biomes) recognized in Brazil. The distribution of endemic and rare species was also explored. The major centre of diversity is located in the Chapada Diamantina, Bahia, inside the biome ‘Caatinga’, but there are hotspots in Minas Gerais and Goiás, within the biome ‘Cerrado’. The biome with highest number of endemic species is the ‘Cerrado’, followed by the ‘Caatinga’.     

Combining traditional morphometrics and molecular markers in cryptic taxa: towards an updated integrative taxonomic treatment for Veronica subgenus Pentasepalae (Plantaginaceae sensu APG II) in the western Mediterranean

The aim of this study was to quantify the phenotypic differences amongst the taxa included in Veronica subgenus Pentasepalae, represented in the western Mediterranean area. In combination with previously obtained data on genotypic differences, this enabled the recognition of eight taxonomic units. The delimitation of the boundaries among species and subspecies was mainly based on molecular data, whereas the best characters to discriminate taxa were selected after an accurate study of herbarium material and living populations. Such a selection was also supported by a detailed morphometric study of 30 quantitative leaf traits in 88 populations. Several morphological characters, including the length of the trichomes, length of the petiole and leaf division, were found to be robust, and could be useful in the identification of the taxa involved. As a conclusion, a key to the taxa is proposed, as well as a complete nomenclatural treatment for the group, which includes the typification of several names. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 68–87.     

Genome‐wide association mapping and biochemical markers reveal that seed ageing and longevity are intricately affected by genetic background and developmental and environmental conditions in barley

Globally, over 7.4 million accessions of crop seeds are stored in gene banks, and conservation of genotypic variation is pivotal for breeding. We combined genetic and biochemical approaches to obtain a broad overview of factors that influence seed storability and ageing in barley (Hordeum vulgare). Seeds from a germplasm collection of 175 genotypes from four continents grown in field plots with different nutrient supply were subjected to two artificial ageing regimes. Genome‐wide association mapping revealed 107 marker trait associations, and hence, genotypic effects on seed ageing. Abiotic and biotic stresses were found to affect seed longevity. To address aspects of abiotic, including oxidative, stress, two major antioxidant groups were analysed. No correlation was found between seed deterioration and the lipid‐soluble tocochromanols, nor with oil, starch and protein contents. Conversely, the water‐soluble glutathione and related thiols were converted to disulphides, indicating a strong shift towards more oxidizing intracellular conditions, in seeds subjected to long‐term dry storage at two temperatures or to two artificial ageing treatments. The data suggest that intracellular pH and (bio)chemical processes leading to seed deterioration were influenced by the type of ageing or storage. Moreover, seed response to ageing or storage treatment appears to be significantly influenced by both maternal environment and genetic background.     

Bimodal transparency as an indicator for alternative states in South American lakes

1. The alternative state theory claims that shallow lakes may have either clear water, and be dominated by submerged macrophytes, or turbid water and be dominated by phytoplankton. Most evidence for this theory comes from studies in temperate or boreal regions of Europe. Because of differences in the strength of trophic interactions, such as in the pressure of zooplankton grazing on phytoplankton, this influential theory might not apply elsewhere. 2. Here, we test the theory for South American lakes, combining field data and Landsat satellite data. We studied the frequency distribution of primary producers and water transparency, looking for potential bimodality separating clear and turbid lakes. A bimodal distribution might be observed if there are indeed alternative states, although would not itself be sufficient evidence for the theory. Possible shifts between alternative states were analysed by comparing satellite data from 1987 to 2005. 3. In our field data, there was a bimodal pattern in phytoplankton abundance and possibly in the abundance of submerged macrophytes, but not in water transparency. Analyses of the larger satellite data set revealed bimodality in lake transparency in 2005, but less so in 1987. In 1987, the lakes were generally clearer, and the transition to higher turbidity was more gradual than in 2005. The stronger bimodality in the more recent data, and the overall lower transparency, could have been caused by an increase in fertiliser use and subsequent eutrophication but also by differences in hydrology. Further, 1987 was much wetter than 2005, which could have caused dilution of suspended particles, leading to clearer water. 4. While a bimodal distribution in the abundance of primary producers and water clarity is not decisive evidence for or against the theory of alternative states, our data clearly fail to refute it.     

Impact of grazing on species composition: Adding complexity to a generalized model

The impact of grazing widely differs among plant communities. A generalized model published in 1988 proposed that this variation could be accounted for by the interaction between primary productivity and the evolutionary history of grazing. As productivity increased, the model predicted larger changes of species composition. Evolutionary history of grazing interacted with productivity: the changes in low‐production systems were smaller if evolutionary history was long, whereas the changes in high‐production systems were independent of evolutionary history. In this paper, we focus on: (i) the difficulties of determining the evolutionary history of grazing of a community, and (ii) additional mechanisms, which, as a sequence of filters in the process of community assembly, could be operating across the gradient of primary production. Assigning a given evolutionary history of grazing to a site has been difficult due to the lack of information on the historical population and distribution of herbivores with an adequate spatial and temporal resolution, and the lack of agreement on the size of the relevant evolutionary time window. Regarding the variation through a gradient of primary production, we propose three additional mechanisms coherent with the prediction of the model. First, the regional pool of available species increases with primary production. Second, grazing intensity (consumption as a proportion of above‐ground production) also increases with primary production. Third, the strength of interspecific positive biotic interactions that protect plants from herbivores decreases with primary production. We highlight an additional potential mechanism, seed dispersal, whose variation across the gradient of productivity is not yet sufficiently understood. By connecting the logic of environmental filters to explain community assemblage with the original proposition of the generalized model, we suggest a series of research lines that can lead to a better understanding of why different communities respond differently to grazing.     

Ethanol production from two varieties of henequen (Agave fourcroydes Lem)

This work demonstrates the significant differences in ethanol production of two henequen (Agave fourcroydes Lem) varieties. Yaax ki, or green henequen, surpasses Sac ki, or white henequen, in weight, sugar accumulation capability and ethanol production. The study was carried out with the ‘piña’ (stem and basal part of the leaves that remain attached to it after harvesting the leaves) of 5‐ and 9‐year‐old plants, cultivated in two localities of Yucatán, México. At 5 years of age, Yaax ki piñas are 33% larger than those of Sac ki, and at 9 years this difference can increase to 59%. Juice from 5‐year‐old piñas of Yaax ki contains 15.6% more reducing sugars, whereas in the must it can exceed 67%. Values obtained in the 9‐year‐old plants indicate that the Yaax ki variety accumulates 30.6% more reducing sugars than the Sac ki, whereas in the must the difference is in favor of Yaax ki is 21.7%. To produce 1 L of ethanol at 40% concentration by volume from 5‐year‐old plants, 48 kg of Sac ki piñas and 29 kg of Yaax ki are required, whereas with the 9‐year‐old plants, only 23 and 19 kg are needed, respectively.