[CO2]- and density-dependent competition between grassland species

The predicted ongoing increase of atmospheric carbon dioxide levels is considered to be one of the main threats to biodiversity due to potential changes in biotic interactions. We tested whether effects of intra‐ and interspecific planting density of the calcareous grassland perennials Bromus erectus and Carex flacca change in response to elevated [CO₂] (600 ppm) by using factorial combinations of seven densities (0, 1, 2, 4, 8, 16, 24 tillers per 8 × 8 cm² cell) of both species in plots with and without CO₂ enrichment. Although aboveground biomass of C. flacca was increased by 54% under elevated [CO₂], the combined aboveground biomass of the whole stand was not significantly increased. C. flacca tended to produce more tillers under elevated [CO₂] while B. erectus produced less tillers. The positive effect of [CO₂] on the number of tillers of C. flacca was strongest at high intraspecific densities. On the other hand, the negative effect of [CO₂] on the number of tillers of B. erectus was not present at intermediate intraspecific planting densities. Seed production of C. flacca was more than doubled under elevated [CO₂], while seed production of B. erectus was not affected. Moreover, the mass per seed of C. flacca was increased by elevated [CO₂] at intermediate interspecific planting densities while the mass per seed of B. erectus was decreased by elevated [CO₂] at high interspecific planting densities. Our results show that the responses of C. flacca and B. erectus to elevated [CO₂] depend in a complex way on initial planting densities of both species. In other words, competition between these two model species is both [CO₂]‐ and density dependent. On average, however, the effects of [CO₂] on the individual species indicate that the composition of calcareous grasslands is likely to change under elevated [CO₂] in favor of C. flacca.     

Predicting adaptive evolution under elevated atmospheric CO2 in the perennial grass Bromus erectus

Increasing concentrations of CO₂ in the atmosphere are likely to affect the ecological dynamics of plant populations and communities worldwide, yet little is known about potential evolutionary consequences of high CO₂. We employed a quantitative genetic framework to examine how the expression of genetic variation and covariation in fitness‐related traits, and thus, the evolutionary potential of a species, is influenced by CO₂. In two field experiments, genotypes of the dominant grassland perennial Bromus erectus were grown for several years in plots maintained at present‐day or at elevated CO₂ levels. Under noncompetitive conditions (experiment 1), elevated CO₂ had little impact on plant survival, growth, and reproduction. Under competitive conditions in plots with diverse plant communities (experiment 2), performance of B. erectus was reduced by elevated CO₂. This suggests that the effect of CO₂ was largely indirect, intensifying competitive interactions. Elevated CO₂ had significant effects on the expression of genetic variation in both the competitive and noncompetitive environment, but the effects were in opposite direction. Heritability of plant size was generally higher at elevated than at ambient CO₂ in the noncompetitive environment, but lower in the competitive environment. Selection analysis revealed a positive genotypic selection differential for plant size at ambient CO₂, indicating selection favoring genotypes with high growth rate. At elevated CO₂, the corresponding selection differential was nonsignificant and slightly negative. This suggests that elevated CO₂ is unlikely to stimulate the evolution of high biomass productivity in this species.     

Evolutionary history of the burnet moth genus Zygaena Fabricius, 1775 (Lepidoptera: Zygaenidae) inferred from nuclear and mitochondrial sequence data: phylogeny, host–plant association, wing pattern evolution and historical biogeography

Burnet moths of the genus Zygaena are a striking group of primarily diurnal Lepidoptera displaying an exceptional phenotypic plasticity. Previous attempts to elucidate the phylogenetic history of the group had been confounded by a perplexing pattern of characters or insufficient taxon sampling. In the present study, we infer a phylogeny of the genus Zygaena by analysing 5.4 kb of their nuclear and mitochondrial DNA. Eighty‐four of the 98 currently recognized species in this genus are considered, including representatives of all described species groups. RNA coding sequences are aligned with reference to zygaenoid moth specific secondary structure models of corresponding molecules. We conduct phylogenetic analyses within a Bayesian framework applying partition specific substitution parameters; covariation of paired sites in RNA gene sequences is accommodated by using doublet substitution models. The molecular data reveal that a considerable number of currently recognized species groups in Zygaena are not monophyletic. The traditional subgeneric classification proves to be artificial as well; Agrumenia and Zygaena (sensu stricto) are polyphyletic. Only the subgenus Mesembrynus can be confirmed as a monophyletic species cluster. Optimization of larval host–plant associations and forewing patterns on sampled trees of the Bayesian analyses suggest convergent evolution of similar wing pattern types in distantly related species clusters and a shift from cyanogenic to acyanogenic host‐plants. The phylogenetic results challenge the classic assumption that early species diversification in Zygaena took place in the Irano–Turkestanian region. Rather, the molecular data point to the western Mediterranean area as the geographical origin of the group and imply a subsequent colonization of the Middle East and Central Asia. We discuss the apparently convergent evolution of similar wing patterns in context with the chemical defence system of burnet moths and suggest a species group concept for the genus Zygaena that accounts for the recent findings. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 92 , 501–520.     

Revision of the Helicellinae of Crete (Gastropoda: Hygromiidae)

This paper presents a comprehensive revision of the Helicellinae of Crete (Gastropoda: Hygromiidae) based on characters of the shell and the genitalia. The native fauna includes eleven Xerocrassa species, two Pseudoxerophila species, and perhaps one Xeromunda species. One additional Xerocrassa species and eight species of the genera Trochoidea, Xeropicta, Xerolenta, Xerotricha, Microxeromagna, and Cernuella were probably introduced by man to Crete. The distribution patterns of the endemic Xerocrassa and Pseudoxerophila species do not provide evidence for the hypothesis that these radiations were caused by the fragmentation of the region of present‐day Crete into several palaeoislands in the late Miocene and Pliocene.     

Negative changes in the scientific publication process in ecology: potential causes and consequences

1. Increasingly viewed to have societal impact and value, science is affected by complex changes such as globalisation and the increasing dominance of commercial interest. As a result, technical advancements, financial concerns, institutional prestige and journal proliferation have created challenges for ecological and other scientific journals and affected the perception of both researchers and the public about the science that they publish. 2. Journals are now used for more than dissemination of scientific research. Institutions use journal rankings for a variety of purposes and often require a pre‐established number of articles in hiring and budgetary decisions. Consequently, journal impact factors have achieved greater importance, and the splitting of articles into smaller parcels of information (‘salami‐slicing’) to increase numbers of publications has become more frequent. 3. Journals may prescribe upper limits to article length, even though the average length of articles for several ecological journals examined has increased over time. There are clear signs, however, that journals without length limits for articles will become rarer. In contrast to ecological journals, taxonomic journals are not following this trend. 4. Two case histories demonstrate how splitting longer ecological articles into a series of shorter ones results in both redundancy of information and actually increases the journal space used overall. Furthermore, with current rejection rates of ecological journals (often ～80%), many thin salami‐sliced articles jam the peer‐review system much longer (through resubmission after rejection) than unsliced articles previously did (e.g. when rejection rates were ～50%). In our experience, the increased pressure to publish many articles in ‘high‐impact’ journals also may decrease the attractiveness of a future scientific career in ecology to young people. 5. ‘Gatekeeping’ of journal quality has shifted from editors to reviewers, and several recent trends are apparent including: bias about appropriate statistical methods; reviewers being more rigid overall; non‐native English writers being criticised for poor communications skills; and favourable reviews being signed more often than unfavourable ones. In terms of production, outsourcing of copy editing has increased the final error rate of published material. 6. We supplemented our perceptions with those of older colleagues (～100 experienced ecologists) that responded to an informal survey on this topic (response rate: 81%). In the opinion of almost 90% of our respondents, the overall review process has changed and for 20% among them the professional quality of reviews has declined. 7. We, and many older colleagues, are convinced there have been some negative changes in the scientific publication process. If younger colleagues share this concern, we can collectively counter this deteriorating situation, because we are the key to the publishing and evaluation process.     

Radial growth response of four dominant boreal tree species to climate along a latitudinal gradient in the eastern Canadian boreal forest

To address the central question of how climate change influences tree growth within the context of global warming, we used dendroclimatological analysis to understand the reactions of four major boreal tree species –Populus tremuloides, Betula papyrifera, Picea mariana, and Pinus banksiana– to climatic variations along a broad latitudinal gradient from 46 to 54°N in the eastern Canadian boreal forest. Tree‐ring chronologies from 34 forested stands distributed at a 1° interval were built, transformed into principal components (PCs), and analyzed through bootstrapped correlation analysis over the period 1950–2003 to identify climate factors limiting the radial growth and the detailed radial growth–climate association along the gradient. All species taken together, previous summer temperature (negative influences), and current January and March–April temperatures (positive influences) showed the most consistent relationships with radial growth across the gradient. Combined with the identified species/site‐specific climate factors, our study suggested that moisture conditions during the year before radial growth played a dominant role in positively regulating P. tremuloides growth, whereas January temperature and growing season moisture conditions positively impacted growth of B. papyrifera. Both P. mariana and P. banksiana were positively affected by the current‐year winter and spring or whole growing season temperatures over the entire range of our corridor. Owing to the impacts of different climate factors on growth, these boreal species showed inconsistent responsiveness to recent warming at the transition zone, where B. papyrifera, P. mariana, and P. banksiana would be the most responsive species, whereas P. tremuloides might be the least. Under continued warming, B. papyrifera stands located north of 49°N, P. tremuloides at northern latitudes, and P. mariana and P. banksiana stands located north of 47°N might benefit from warming winter and spring temperatures to enhance their radial growth in the coming decades, whereas other southern stands might be decreasing in radial growth.     

Pollen morphology of the Swertiinae (Gentianaceae): phylogenetic implications

Recent molecular surveys of the Swertiinae (Gentianaceae–Gentianeae) revealed unexpected phylogenetic relationships, including polyphyly of the genera Gentianella , Jaeschkea , Lomatogonium and Swertia . To find new non-molecular characters supporting the phylogeny, we examined the exine variation of 73 species of all major lineages of subtribe Swertiinae using environmental scanning electron miscroscopy supplementing older, mainly light microscopical, studies. In contrast to previous studies, we were able to pick out taxa from phylogenetic key positions with particular focus on Swertia . Many distantly related taxa such as parts of Frasera , Gentianopsis , Halenia , Gentianella , Megacodon and several lineages of Swertia share a striate–reticulate or reticulate exine pattern. This is interpreted as the plesiomorphic character state of Swertiinae. There is also considerable variation of derived patterns; for example, different types of microechinate or almost smooth pollen was repeatedly observed in distantly related groups. Another extreme was the ring-shaped reticulation found in a North American species of Gentianopsis . Unfortunately, major relationships as revealed by molecular analyses were rarely supported because of the abundance of the plesiomorphic type and homoplasy even on low taxonomic levels; for example, within Lomatogonium . Exine variation was particularly useful in characterizing independent lineages of Swertia . For example, according to pollen characters and in agreement with other data, the Asian Swertia cuneata is a sister group of a strongly diversified African lineage and Swertia yunnanensis , which is rather aberrant in flower morphology, seems close to parts of Lomatogonium .  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 323–341.