Dark bands on pyritic internal moulds of the Early Jurassic ammonites Oxynoticeras and Cheltonia from Gloucestershire,England: interpretation and significance to ammonite growth analysis

Abstract: Thin, radiating, darker bands occur on pyritic internal moulds of the Early Jurassic ammonites Oxynoticeras and Cheltonia from Bishop’s Cleeve, Gloucestershire. They closely resemble true colour patterns preserved in Early Jurassic Calliphylloceras from Kutch, India, and false colour patterns reported in Carboniferous and Triassic ammonoids. Up to five dark bands occur within the body chamber, suggesting that they do not represent serially repeated anatomical structures, but the same feature repeatedly formed during growth. Dark bands are interpreted as traces of black bands deposited on the inside of the shell at the aperture during pauses in growth. The angles between dark bands and between septa correlate strongly in Cheltonia, suggesting that pauses in growth coincided with septal secretion during the chamber formation cycle. There are, however, no other indications that growth was episodic in either genus.     

Faecal case architecture in the gibbosus species group of Neochlamisus Karren, 1972 (Coleoptera: Chrysomelidae: Cryptocephalinae: Chlamisini)

Constructions composed of faeces are rare in insects, but occur in certain leaf-beetle clades. Members of the subfamily Cryptocephalinae share a complex behavioural and morphological synapomorphy, involving portable faecal cases that house the immature stages. A maternally initiated egg case is expanded and enlarged through four larval stadia, then sealed to provide a pupal chamber from which adults eventually emerge. We analyse and compare faecal-case architecture in ten taxa of the cryptocephaline genus Neochlamisus , and assess structural variation within a life cycle, between different 'host forms' of Neochlamisus bebbianae , and among species. These cases proved to be comprised primarily of faeces, with plant trichomes representing the only common secondary component. General architectural trends reflected variation in shape, faecal texture, and the incorporation and density of trichomes. Deviations of the Neochlamisus case from a simple geometrical gnomon reflect the changing body size of the animal, differential application of faeces, and shifts in the orientation of the carriage of the case. Neochlamisus cases are presumably energetically costly to produce, carry, and maintain, and some adaptive hypotheses of case evolution are proposed. Additionally, literature on case morphology in other camptosomates is reviewed.  © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 152 , 315–351.     

Tradeoffs and thresholds in the effects of nitrogen addition on biodiversity and ecosystem functioning: evidence from inner Mongolia Grasslands

Nitrogen (N) deposition is widely considered an environmental problem that leads to biodiversity loss and reduced ecosystem resilience; but, N fertilization has also been used as a management tool for enhancing primary production and ground cover, thereby promoting the restoration of degraded lands. However, empirical evaluation of these contrasting impacts is lacking. We tested the dual effects of N enrichment on biodiversity and ecosystem functioning at different organizational levels (i.e., plant species, functional groups, and community) by adding N at 0, 1.75, 5.25, 10.5, 17.5, and 28.0 g N m^?2 yr^?1 for four years in two contrasting field sites in Inner Mongolia: an undisturbed mature grassland and a nearby degraded grassland of the same type. N addition had both quantitatively and qualitatively different effects on the two communities. In the mature community, N addition led to a large reduction in species richness, accompanied by increased dominance of early successional annuals and loss of perennial grasses and forbs at all N input rates. In the degraded community, however, N addition increased the productivity and dominance of perennial rhizomatous grasses, with only a slight reduction in species richness and no significant change in annual abundance. The mature grassland was much more sensitive to N‐induced changes in community structure, likely as a result of higher soil moisture accentuating limitation by N alone. Our findings suggest that the critical threshold for N‐induced species loss to mature Eurasian grasslands is below 1.75 g N m^?2 yr^?1, and that changes in aboveground biomass, species richness, and plant functional group composition to both mature and degraded ecosystems saturate at N addition rates of approximately 10.5 g N m^?2 yr^?1. This work highlights the tradeoffs that exist in assessing the total impact of N deposition on ecosystem function.     

Phylogeny of the tribe Sciophilini (Diptera: Mycetophilidae: Sciophilinae)

The monophyly and phylogenetic relationships within the species rich Sciophilini (Diptera: Mycetophilidae) were analysed, based on 96 adult morphological characters. The cladistic analysis included 80 Sciophilini exemplar species (representing all but 1 of the 36 genera placed previously in the Sciophilini) and 11 outgroup taxa of other mycetophilid tribes. The monophyly of Sciophilini was supported in the parsimony analysis by four synapomorphies. The tribe now contains 34 genera: Acnemia Winnertz, Acomoptera Vockeroth, Adicroneura Vockeroth, Afrocnemia Matile, Allocotocera Mik, Anaclileia Meunier, Aneura Marshall, Austrosciophila Tonnoir, Azana Walker, Baeopterogyna Vockeroth, Cluzobra Edwards, Drepanocercus Vockeroth, Duretophragma Borkent gen.n. , Eudicrana Loew, Leptomorphus Curtis, Loicia Vockeroth, Megalopelma Enderlein, Monoclona Mik, Morganiella Tonnoir & Edwards, Neoallocotocera Tonnoir, Neoaphelomera Miller, Neotrizygia Tonnoir & Edwards, Neuratelia Rondani, Paramorganiella Tonnoir, Paratinia Mik, Paratrizygia Tonnoir, Parvicellula Marshall, Phthinia Winnertz, Polylepta Winnertz, Sciophila Meigen, Stenophragma Skuse, Tasmanina Tonnoir, Taxicnemis Tonnoir & Edwards, and Trizygia Skuse. Four genera placed previously in Sciophilini (Coelophthinia Edwards, Impleta Plassmann, Speolepta Edwards and Syntemna Winnertz) are transferred to the Gnoristini. Neoneurotelia Shinji and Neoparatinia Shinji are considered nomina dubia . Diagnoses are given for all genera in the tribe. Duretophragma gen.n. is described for the following species (all of which are comb.n. ): Duretophragma andina (Duret), Duretophragma argentina (Duret), Duretophragma glabanum (Johannsen), Duretophragma fusca (Edwards), Duretophragma humeralis (Edwards), Duretophragma intermedia (Edwards), Duretophragma longifurcata (Freeman) (type species), Duretophragma morigenea (Edwards), Duretophragma naumanni (Duret), Duretophragma nigricauda (Edwards), Duretophragma obscura (Duret), Duretophragma ochracea (Freeman), Duretophragma pleuralis (Edwards) and Duretophragma similis (Johannsen). Other new generic combinations include: Trizygia albidens (Oliveira & Amorim) comb.n. , Trizygia alvesi (Oliveira & Amorim) comb.n. , Trizygia balbi (Oliveira & Amorim) comb.n. , Trizygia camargoi (Oliveira & Amorim) comb.n. and Afrocnemia stellamicans (Chandler) comb.n .     

Modeling Distribution of Dispersal Distances in Male White-Tailed Deer

Abstract: Dispersal distances and their distribution pattern are important to understanding such phenomena as disease spread and gene flow, but oftentimes dispersal characteristics are modeled as a fixed trait for a given species. We found that dispersal distributions differ for spring and autumn dispersals of yearling male white-tailed deer (Odocoileus virginianus) but that combined data can be adequately modeled based on a log-normal distribution. We modeled distribution of dispersal distances from 3 distinct populations in Pennsylvania and Maryland, USA, based on the relationship between percent forest cover and mean dispersal distance and the relationship between mean and variance of dispersal distances. Our results suggest distributions of distances for dispersing yearling male white-tailed deer can be modeled by simply measuring a readily obtained landscape metric, percent forest cover, which could be used to create generalized spatially explicit disease or gene flow models.     

Effect of fragmentation on predation pressure of insect herbivores in a north temperate deciduous forest ecosystem

1. Forest fragmentation affects many ecosystem processes by spatially altering relationships among organisms. Herbivory by arthropods is an important ecosystem processes in forests that fragmentation alters by changing relationships among herbivores, their predators, and their hosts. The relative importance of these factors remains unclear. 2. It was tested whether the exclusion of vertebrate predators affected the arthropod abundance or amounts of herbivory in a fragmented, deciduous forest landscape in southern Quebec. Differences in the abundance of arthropod herbivores and amounts of herbivory in forest patches with different landscape characteristics (small isolated patches versus large connected ones), on sugar maple saplings with or without exclosures that restricted access by large vertebrate predators were measured. 3. Saplings protected from predators with exclosures had greater abundances of all arthropods (herbivores and invertebrate predators) than those without, indicating potential top‐down effects of vertebrate predators on arthropods. Analysis of effect sizes between exclosure treatments and controls suggests the magnitude of predation effects may be affected by fragmentation. 4. Strong top‐down effects of predators on arthropods, and weak effects of fragmentation on predation or amounts of herbivory were found. As a result, herbivory may be regulated by factors other than vertebrate predation in this system.     

Parthenogenesis did not consistently evolve in insular populations of Ischnura hastata (Odonata,Coenagrionidae)

1. The evolutionary advantages that have driven the evolution of sex are still very much debated, and a number of benefits of parthenogenesis over sexual reproduction have been proposed. In particular, parthenogenetic individuals are thought to exhibit higher probabilities of establishment following arrival in new, isolated habitats such as islands. 2. One notable example of parthenogenesis occurring in islands is the damselfly Ischnura hastata, an American species that has colonised the Azores archipelago, where the populations consist only of females. This is the only known example of parthenogenesis within the insect order Odonata. 3. Here, two island populations of I. hastata were studied, one in the Galapagos and one in Cuba, to test whether island colonisation is consistently associated with parthenogenesis in this species. Field capture–mark–recapture studies and laboratory rearing of field‐collected eggs were undertaken in both areas. 4. Sex ratios in the field were found to be heavily female‐biased among mature individuals; however, fertility rates of field‐collected eggs were high, and the sex ratios in the laboratory did not differ from 1 : 1. Data from laboratory rearing showed that shorter larval development times and shorter adult life spans in males result in protandry, which might explain the skewed sex ratios in the field. 5. These findings are consistent with sex differences in key demographic parameters which could predispose I. hastata to parthenogenesis. However, the Azores population of I. hastata remains the only documented case of asexual reproduction in this insect group.     

MODELING REGIONAL WATERFOWL HARVEST RATES USING MARKOV CHAIN MONTE CARLO

Abstract: We developed models for simultaneous inference on movement and harvest rates, and of factors influencing harvest rates, using band-recovery data and Markov chain Monte Carlo (MCMC) modeling. We modeled variation in harvest rates for American black ducks (Anas rubripes) during 1971–1994 using recoveries of ducks banded in 3 breeding regions and recovered in 6 harvest regions in Canada and the United States. Models based on season length or bag limit together with season length, and incorporating a random year- and area-specific effect, were superior to other models as gauged by information criteria, fit statistics, and cross-validation. We used these models to generate posterior predictive distributions for harvest rates as a function of harvest regulations, for application to adaptive harvest management.     

Respiratory Adaptations in Intertidal Fish

SYNOPSIS: Intertidal rockpools provide a challenging environmentfor rockpool fish with rapid changes taking place in many environmentalparameters over a tidal cycle. Intertidal fish exhibit a numberof behavioural adaptations such as the avoidance of hypoxicsituations or remaining inactive during aerial "stranding."Other species are, however, well adapted to breathe air andexhibit morphological adaptations such as smaller gill areas,specialized buccopharyngeal epithelia and a proliferation ofcutaneous blood vessels in the skin. Oxygen consumption in rockpoolfish is comparable to non-intertidal fish and responds in asimilar manner to temperature changes. The ability to regulateoxygen consumption down to oxygen tensions below 40 Torr is,however, marked in rockpool species. Aerial and aquatic ratesof respiration are similar in those species which are able tobreathe air and the respiratory quotient normally remains between0.7 and 0.9. A number of intertidal fish are well adapted forcutaneous respiration, satisfying over half of their oxygenand carbon dioxide exchange through the skin. Ventilatory responsesto increased temperature, hyperoxia and hypoxia are similarto those of other fish but cardiac responses may differ in thatno change in heart rate is seen under hypoxia or hyperoxia.Ventilatory and cardiac responses to aerial respiration arewell adapted in some species maintaining ventilation and perfusionduring aerial exposure. A marked Bohr effect, low temperaturesensitivity and a temperature dependent Haldane effect havebeen measured in the haemoglobolin of some intertidal fish.These properties may assist oxygen transport and carbon dioxideexchange during cyclical changes in environmental parameterswithin an intertidal rockpool.     

The herbaceous lycophyte Haskinsia Grierson and Banks from the Devonian of western Venezuela, with observations on leaf morphology and fertile specimens

The Devonian herbaceous lycophyte genus Haskinsia Grierson and Banks is characterized by narrow dichotomizing stems and helically arranged petiolate leaves with a broad, approximately deltoid, lamina. New specimens are reported from four horizons in the Lower Member of the Campo Chico Formation, Sierra de Perijá, western Venezuela. H. sagittaka Edwards and Benedetto has sagittate leaves, and fertile specimens are reported for the first time; the ellipsoidal/obovoid adaxially-flattened sporangium is attached to unmodified leaves towards the top of the petiole in the adaxial position. H. sp. has sagittate leaves which are larger than any yet attributed to the genus but is represented by only three specimens. H. hastata sp. nov. has hastate leaves; the sporangia are more globose but positioned similarly to those of H. sagittata. The occurrence of the sporangia on unmodified microphylls indicates that Haskinsia is a member of Protolepidodendrales. The status of Haskinsiaceae is discussed. The Venezuelan specimens are compared with other records of Haskimi and Haskinsia -like plants from North America, Kazakhstan, North China, North Africa and Antarctica.