Role of the aquatic pathway in the carbon and greenhouse gas budgets of a peatland catchment

Peatland streams have repeatedly been shown to be highly supersaturated in both CO₂ and CH₄ with respect to the atmosphere, and in combination with dissolved (DOC) and particulate organic carbon (POC) represent a potentially important pathway for catchment greenhouse gas (GHG) and carbon (C) losses. The aim of this study was to create a complete C and GHG (CO₂, CH₄, N₂O) budget for Auchencorth Moss, an ombrotrophic peatland in southern Scotland, by combining flux tower, static chamber and aquatic flux measurements from 2 consecutive years. The sink/source strength of the catchment in terms of both C and GHGs was compared to assess the relative importance of the aquatic pathway. During the study period (2007–2008) the catchment functioned as a net sink for GHGs (352 g CO₂‐Eq m^?2 yr^?1) and C (69.5 g C m^?2 yr^?1). The greatest flux in both the GHG and C budget was net ecosystem exchange (NEE). Terrestrial emissions of CH₄ and N₂O combined returned only 4% of CO₂ equivalents captured by NEE to the atmosphere, whereas evasion of GHGs from the stream surface returned 12%. DOC represented a loss of 24% of NEE C uptake, which if processed and evaded downstream, outside of the catchment, may lead to a significant underestimation of the actual catchment‐derived GHG losses. The budgets clearly show the importance of aquatic fluxes at Auchencorth Moss and highlight the need to consider both the C and GHG budgets simultaneously.     

Environmental controls on CH4 emission from polygonal tundra on the microsite scale in the Lena river delta,Siberia

The carbon budgets of the atmosphere and terrestrial ecosystems are closely coupled by vertical gas exchange fluxes. Uncertainties remain with respect to high latitude ecosystems and the processes driving their temporally and spatially highly variable methane (CH₄) exchange. Problems associated with scaling plot measurements to larger areas in heterogeneous environments are addressed based on intensive field studies on two nested spatial scales in Northern Siberia. CH₄ fluxes on the microsite scale (0.1–100 m²) were measured in the Lena River Delta from July through September 2006 by closed chambers and were compared with simultaneous ecosystem scale (10⁴–10⁶ m²) flux measurements by the eddy covariance (EC) method. Closed chamber measurements were conducted almost daily on 15 plots in four differently developed polygon centers and on a polygon rim. Controls on CH₄ emission were identified by stepwise multiple regression. In contrast to relatively low ecosystem‐scale fluxes controlled mainly by near‐surface turbulence, fluxes on the microsite scale were almost an order of magnitude higher at the wet polygon centers and near zero at the drier polygon rim and high‐center polygon. Microsite scale CH₄ fluxes varied strongly even within the same microsites. The only statistically significant control on chamber‐based fluxes was surface temperature calculated using the Stefan–Boltzmann equation in the wet polygon centers, whereas no significant control was found for the low emissions from the dry sites. The comparison with the EC measurements reveals differences in controls and the seasonal dynamics between the two measurement scales, which may have consequences for scaling and process‐based models. Despite those differences, closed chamber measurements from within the EC footprint could be scaled by an area‐weighting approach of landcover classes based on high‐resolution imagery to match the total ecosystem‐scale emission. Our nested sampling design allowed for checking scaling results against measurements and to identify potentially missed sources or sinks.     

Survival and Breeding Transitions for a Reintroduced Bison Population: a Multistate Approach

Abstract: The iconic plains bison (Bison bison) have been reintroduced to many places in their former range, but there are few scientific data evaluating the success of these reintroductions or guiding the continued management of these populations. Relying on mark-recapture data, we used a multistate model to estimate bison survival and breeding transition probabilities while controlling for the recapture process. We tested hypotheses in these demographic parameters associated with age, sex, reproductive state, and environmental variables. We also estimated biological process variation in survival and breeding transition probabilities by factoring out sampling variation. The recapture rate of females and calves was high (0.78 ± 0.15 [SE]) and much lower for males (0.41 ± 0.23), especially older males (0.17 ± 0.15). We found that overall bison survival was high (>0.8) and that males (0.80 ± 0.13) survived at lower rates than females (0.94 ± 0.04), but as females aged survival declined (0.89 ± 0.05 for F ≥15 yr old). Lactating and non-lactating females survived at similar rates. We found that females can conceive early (approx. 1.5 yr of age) and had a high probability (approx. 0.8) of breeding in consecutive years, until age 13.5 years, when females that were non-lactating tended to stay in that state. Our results suggest senescence in reproduction and survival for females. We found little support for the effect of climatic covariates on demographic rates, perhaps because the park's current population management goals were predicated from drought-year conditions. This reintroduction has been successful, but continued culling actions will need to be employed and an adaptive management approach is warranted. Our demographic approach can be applied to other heavily managed large-ungulate systems with few or no natural predators.     

The structural mechanics and evolution of aquaflying birds

Mass‐specific bone strength was examined in the forelimb and hindlimb of 64 species of birds to determine if aquaflying birds (which utilize the wings for propulsion underwater) differ in their skeletal strength compared with other avian taxa. Long bone strengths were estimated from cross‐sectional measurements. Compared with the expectation from geometric similarity, humeral section modulus in volant birds scales nearly isometrically, while femoral strength scales with significant positive allometry. Penguin mass‐specific humeral strength is greatly elevated, but the average humeral strength in species that are propelled by the wings in both air and water do not differ from the values calculated in non‐diving taxa. However, amphibious flyers have gracile femora. Comparative analyses using independent contrasts were utilized to examine the impact of phylogenetic signal. The residual measured for the penguin–procellariiform humeral strength contrast was larger in magnitude (residual of 2.14) than at any other node in the phylogeny. The data strongly indicate that the transition from an amphibious flight condition to a fully aquatic condition involves greater changes in mechanical factors than the transition from purely aerial locomotion to amphibious wing use. There remains the possibility that a historical effect, such as ancestral body size, has impacted the mechanical scaling of penguins. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 687–698.     

Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia)

The Acochlidia are unique among opisthobranch gastropods in combining extremely high morphological and ecological diversity with modest species diversity. The phylogeny of acochlidians has never been addressed by cladistic means, as their evolution has remained unknown. This study gives a first overview on more than 150 biological and morphological characters that are potentially useful for phylogenetic analysis. Based on 107 characters, a parsimony analysis (PAUP) was performed for all 27 valid acochlidian species together with 11 (plus two) outgroup taxa. The resulting strict consensus tree shows a moderate overall resolution, with at least some bootstrap support for most resolved nodes. The Acochlidia are clearly monophyletic, and originate from an unresolved basal opisthobranch level. The Acochlidia split into the Hedylopsacea (Tantulum (Hedylopsis (Pseudunela (Strubellia (‘Acochlidium’, ‘Palliohedyle’))))) and Microhedylacea (Asperspina (Pontohedyle, ‘Parhedyle’, ‘Microhedyle’, (Ganitus, Paraganitus))). The formerly enigmatic Ganitidae, resembling sacoglossan opisthobranchs by having dagger‐like rachidian radular teeth, are likely to be highly derived microhedylids. The paraphyly of some of the traditionally recognized family level taxa induced a preliminary reclassification. From the phylogenetic hypothesis obtained, we conclude that the acochlidian ancestor was marine mesopsammic. The colonization of limnic systems occurred twice, independently: first in the Caribbean (with the development of the small interstitial Tantulum elegans), and second in the Indo‐Pacific, with a radiation of large‐sized benthic acochlidian species. The evolution of extraordinary reproductive features, such as hypodermic impregnation by a complex copulative aparatus in hedylopsaceans, cutaneous insemination via spermatophores in microhedylaceans, and gonochorism in Microhedylidae s.l. (including Ganitidae), is discussed. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 124–154.     

Parallel evolution of insular Olea europaea subspecies based on geographical structuring of plastid DNA variation and phenotypic similarity in leaf traits

Strong geographical isolation within the distribution of a species may result in differentiated lineages exhibiting conspicuous phenotypic differences. In the present paper, we investigate whether plastid and phenotypic variation is geographically structured within the Olea europaea complex in Macaronesia, which comprises three subspecies separated by oceanic barriers: maroccana (south‐west Morocco), guanchica (Canary Islands) and cerasiformis (Madeira archipelago). Plastid variation showed a significant pattern of geographical structure (N_ST > G_ST = 0.56), because of the lack of shared haplotypes among subspecies and the presence of a single and private haplotype in the eastern Canary Islands. Such a clear molecular structure, however, was not reflected in a congruent pattern of phenotypic differentiation among taxa in leaf morpho‐functional traits. Despite the substantial genetic differentiation observed between the subspecies from Madeira and the Canary Islands, they displayed both higher leaf size (leaf area) and specific leaf area (leaf surface area‐to‐mass ratio) than their continental counterparts, probably as a result of oceanic conditions in subtropical environments. Unlike most of the plant groups previously studied in the Macaronesian region, the lineages of Olea illustrate how low phenotypic differentiation can be also related to a clear molecular differentiation in oceanic island enclaves. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162 , 54–63.     

New data on molluscs and their shell microstructures from the Middle Cambrian Gowers Formation, Australia

Abstract: Numerous new cases of preserved shell microstructure were discovered in molluscs from the Middle Cambrian Gowers Formation (Ptychagnostus atavus/Peronopsis opimus Zone, Floran Stage) in the Georgina Basin, Australia. The new data provide further evidence that, by the Middle Cambrian, molluscan shell microstructures were diverse, and many molluscs had a complex shell with multiple types of shell microstructure. In addition, many new occurrences of laminar microstructures are described herein. For many, the nature of these laminar microstructures is not known, but in three species the microstructure is foliated calcite, and in at least two the microstructure is more likely to have been calcitic semi‐nacre, a type of microstructure known in brachiopods and bryozoans but unknown in modern molluscs. This commonality among these three closely related lophotrochozoans underscores a similar mechanism of biomineralization. Moreover, these observations suggest a prevalence of calcite‐shelled lineages among molluscs from the Middle Cambrian, a time of calcite seas. In addition, the broad occurrence of laminar, nacre‐like microstructures in many of these fossils reveals how widespread these strong (fracture‐resistant) microstructures were in Middle Cambrian molluscs. Additionally, a few specimens of Yochelcionella preserve imprints of a bilaterally symmetrical pair of muscle scars. New taxa described here include Corystos thorntoniensis gen. et sp. nov., Yochelcionella snorkorum sp. nov., Yochelcionella saginata sp. nov., and Anhuiconus? agrenon sp. nov.     

A new coral‐associated decapod assemblage from the Upper Miocene (Messinian) Upper Coralline Limestone of Malta (Central Mediterranean)

Abstract: A rich coral‐associated decapod assemblage is recorded from the ‘Depiru Beds’ of the upper part of the Upper Coralline Limestone (Messinian, Upper Miocene), from the island of Malta. Nineteen species within 17 genera have been discovered, where 14 genera are new for Malta. Four new species are described, namely Micippa annamariae sp. nov., Pilumnus scaber sp. nov., Panopeus muelleri sp. nov. and Herbstia melitense sp. nov. Herbstia melitense sp. nov. constitutes the first record of the genus from the fossil record in the Mediterranean region. This discovery more than doubles the number of known fossil decapod species from Malta. The fossil bivalve Jouannetia (J.) semicaudata Des Moulins, 1830 and the extant decapod Maja goltziana D’Oliveira, 1888, are also recorded for the first time from Malta. Other Neogene coral‐associated decapod assemblages are investigated and correlated with the new assemblage from Malta. The migration of taxa between the Mediterranean region and the Paratethys, particularly during the Lower Badenian (Langhian), is evidenced by the strong affinity of the Maltese decapod assemblage with that of the Middle Miocene Badenian assemblages from Hungary, Poland and Ukraine. Upper Miocene, Messinian assemblages from Spain, Algeria and Morocco are also similar to that from Malta.     

Seeing red: the origin of grain pigmentation in US weedy rice

Weedy forms of crop species infest agricultural fields worldwide and are a leading cause of crop losses, yet little is known about how these weeds evolve. Red rice (Oryza sativa), a major weed of cultivated rice fields in the US, is recognized by the dark‐pigmented grain that gives it its common name. Studies using neutral molecular markers have indicated a close relationship between US red rice and domesticated rice, suggesting that the weed may have originated through reversion of domesticated rice to a feral form. We have tested this reversion hypothesis by examining molecular variation at Rc, the regulatory gene responsible for grain pigmentation differences between domesticated and wild rice. Loss‐of‐function mutations at Rc account for the absence of proanthocyanidin pigments in cultivated rice grains, and the major rc domestication allele has been shown to be capable of spontaneous reversion to a functional form through additional mutations at the Rc locus. Using a diverse sample of 156 weedy, domesticated and wild Oryzas, we analysed DNA sequence variation at Rc and its surrounding 4 Mb genomic region. We find that reversion of domestication alleles does not account for the pigmented grains of weed accessions; moreover, we find that haplotypes characterizing the weed are either absent or very rare in cultivated rice. Sequences from genomic regions flanking Rc are consistent with a genomic footprint of the rc selective sweep in cultivated rice, and they are compatible with a close relationship of red rice to Asian Oryzas that have never been cultivated in the US.     

Molecular identification of brood‐parasitic females reveals an opportunistic reproductive tactic in ruddy ducks

In many taxa, females lay eggs in the nests of other conspecifics. To determine the conditions under which conspecific brood parasitism develops, it is necessary to identify parasitic offspring and the females who produce them; however, for most systems parasitism can be difficult to observe and most genetic approaches have relatively low resolving power. In this study, we used protein fingerprinting from egg albumen and 10 microsatellite loci to genetically match parasitic ducklings to their mothers in a population of ruddy ducks (Oxyura jamaicensis). We found that 67% of nests contained parasitic offspring, and we successfully identified their mothers in 61% of the cases. Of the parasitic females identified, 77% also had nests of their own (i.e. a dual tactic, where females both nest and lay parasitically), and we found no evidence that parasitic females pursued a specialist (parasitism only) tactic. We also found that parasitic egg laying was not influenced by nest loss, predation or female condition. Thus, in contrast to most waterfowl studied to date, female ruddy ducks appear to lay parasitic eggs whenever the opportunity arises.