Marine Borers in Calcareous Terrigenous Rocks of the Pacific Coast

Biological attack of carbonate-cemented sandstones and mudstones(Cretaceous and Eocene ages) and semi-consolidated calcareousmuds (Holocene age) were studied near La Jolla, southern California.Rocks were collected from the intertidal zone to a depth of40 m using SCUBA. The deeper samples came from Scripps and LaJolla submarine canyons. In order to learn of the borers and their preferred substrata,we studied the borers in situ as well as in aquaria, examinedtheir borings with x-ray radiography, and analyzed the boredrocks by petrographic techniques. In preferred substrata a sequence of boring activities resultedin over half of the initialrock volume being excavated to depthsof 10 cm. The major initial borers were bivalves (pholads, Lithophaga), which made straight smooth-walled holes up to 10 cm deep andat all angles to the rock surfaces. When abandoned, these holeswere modified by other borers, and interconnected by smoothor roughhewn sinuous passageways 1 to 15 mm in diameter. Thepassageways were concentrated along bedding planes and in selectedlayers of rock, meeting at common points to form galleries.Many crustaceans and worms occupied the passageways, and severalkinds of saapings and/or etchings characterized the walls. Speciesaccomplishing this have not yet been determined. A variety ofborings 1 to 5 mm in diameter have single or multiple openingsinto the larger passageways. Rates of biological erosion of the rock were obtained from thedepth of penetration of the borers and estimated length of lifespans in years. Yearly attrition is estimated to range from2to 10 mm in some localities. Physical and chemical submarine weathering of these rocks aloneseldom penetrates more thanone cm from the exposed surface.Because biological penetration is much greater, it is an importantfactor in shaping the seabed. Borers attack fine-grained rocksmore intensely than those that are coarse-grained, perhaps accountingfor the dearth of mudstones on the seabed near La Jolla, exceptfor the steep and more rapidly eroding walls of the submarinecanyons. Most rocks presently exposed on the relatively flatupper continental shelf (10 to 30 m) appear to be remnants ofhighly indurated sandstone strata, less susceptible to biologicalattack.     

A 250 year comparison of historical, macrofossil and pollen records of aquatic plants in a shallow lake

1. Sedimentary remains of aquatic plants, both vegetative (turions, leaves, spines) and reproductive (fruits, seeds, pollen), may provide a record of temporal changes in the submerged vegetation of lakes. An independent assessment of the degree to which these remains reflect past floristic change is, however, rarely possible. 2. By exploiting an extensive series of historical plant records for a small shallow lake we compare plant macrofossil (three cores) and pollen (one core) profiles with the documented sequence of submerged vegetation change since c. 1750 AD. The data set is based on 146 site visits with 658 observations including 42 taxa classified as aquatic, spanning 250 years. 3. Approximately 40% of the historically recorded aquatic taxa were represented by macro‐remains. In general macrofossils underestimated past species diversity, with pondweeds (three of eight historically recorded Potamogeton species were found) particularly poorly represented. Nonetheless, several taxa not reported from historical surveys (e.g. Myriophyllum alterniflorum and Characeae) were present in the sediment record. 4. The pollen record revealed taxa which left no macro‐remains (e.g. Littorella uniflora), and the macrofossil record provided improved taxonomic resolution for some taxa (e.g. Potamogeton) and a more reliable record of persistence, appearance and loss of others (e.g. Myriophyllum spp. and Nymphaeaceae). 5. Detrended correspondence analysis indicated that changes in the community composition evidenced by the palaeolimnological and historical records were synchronous and of a similar magnitude. Both records pointed to a major change at around 1800, with the historical record suggesting a more abrupt change than the sedimentary data. There was good agreement on a subsequent change c. 1930. 6. The palaeolimnological data did not provide a complete inventory of historically recorded species. Nevertheless, these results suggest that combined macrofossil and pollen records provide a reliable indication of temporal change in the dominant components of the submerged and floating‐leaved aquatic vegetation of shallow lakes. As such palaeolimnology may provide a useful tool for establishing community dynamics and successions of plants over decadal to centennial timescales.     

Above- and below-ground responses of C3–C4 species mixtures to elevated CO2 and soil water availability

We evaluated the influences of CO₂[Control, ～ 370 µ mol mol ^{? 1}; 200 µ mol mol ^{? 1} above ambient applied by free‐air CO₂ enrichment (FACE)] and soil water (Wet, Dry) on above‐ and below‐ground responses of C₃ (cotton, Gossypium hirsutum) and C₄ (sorghum, Sorghum bicolor) plants in monocultures and two density mixtures. In monocultures, CO₂ enrichment increased height, leaf area, above‐ground biomass and reproductive output of cotton, but not sorghum, and was independent of soil water treatment. In mixtures, cotton, but not sorghum, above‐ground biomass and height were generally reduced compared to monocultures, across both CO₂ and soil water treatments. Density did not affect individual plant responses of either cotton or sorghum across the other treatments. Total (cotton + sorghum) leaf area and above‐ground biomass in low‐density mixtures were similar between CO₂ treatments, but increased by 17–21% with FACE in high‐density mixtures, due to a 121% enhancement of cotton leaf area and a 276% increase in biomass under the FACE treatment. Total root biomass in the upper 1.2 m of the soil was not influenced by CO₂ or by soil water in monoculture or mixtures; however, under dry conditions we observed significantly more roots at lower soil depths ( > 45 cm). Sorghum roots comprised 81–85% of the total roots in the low‐density mixture and 58–73% in the high‐density mixture. CO₂‐enrichment partly offset negative effects of interspecific competition on cotton in both low‐ and high‐density mixtures by increasing above‐ground biomass, with a greater relative increase in the high‐density mixture. As a consequence, CO₂‐enrichment increased total above‐ground yield of the mixture at high density. Individual plant responses to CO₂ enrichment in global change models that evaluate mixed plant communities should be adjusted to incorporate feedbacks for interspecific competition. Future field studies in natural ecosystems should address the role that a CO₂‐mediated increase in C₃ growth may have on subsequent vegetation change.     

Size, shell–living and carcinization in geographic populations of a hermit crab, Pagurus hirsutiusculus

Carcinization, the evolution of a crab–like morphology, has occurred in many hermit crabs. Pagurus hirsutiusculus hermit crabs exhibit geographic variation in traits associated with carcinization. Measurements derived from image analysis of P. hirsutiusculus specimens from geographic locations along the Pacific coast of North America show that Alaskan specimens: (1) are larger, (2) exhibit reduced snail shell–living, and (3) have relatively broader anterior carapaces than southern Californian specimens. This geographic variation may provide general insight into carcinization and the evolution of shell loss in hermit crabs.     

Evidence for a substantial host‐use bottleneck following the invasion of an exotic,polyphagous weevil

1. The successful establishment of novel plant–insect interactions may depend on the availability of suitable hosts, which itself is influenced by the inherent flexibility of the herbivore for the native plants in its new range. The polyphagous beech leaf mining weevil, Orchestes fagi L., is a recent invader to eastern Canada, and while beech is a primary host, it remains unclear the extent to which it might also utilise co‐occurring secondary hosts, as has been observed in its native European range. 2. A combination of field and laboratory feeding trials were used to quantify weevil secondary host use. Based on its expansive native host range in Europe, it was predicted that American beech (Fagus grandifolia Ehrh.), as well as several additional plant species, would be susceptible to weevil damage. 3. Contrary to this prediction, weevil feeding was almost entirely exclusive to beech in both the field and laboratory feeding trials. This result is further supported by field observations that revealed an absence of weevils and eggs on species other than beech. In general, the lack of pre‐diapause feeding on any alternate host species represented an extreme departure from feeding habits observed within the native range. 4. Overall, this host‐use bottleneck suggests that the adoption of a novel primary host by O. fagi, in this case American beech, may remove the normal requirement for secondary hosts and suggests a significant departure from native feeding habits with possible consequences for related life‐history parameters such as overwintering survival and fecundity.     

Vegetation and flora associated with localized snow accumulation at Mount Field West,Tasmania

The vegetation associated with a snow patch at Mt Field in Tasmania is described and mapped. Seven distinct vegetation types were found to be related directly to topography and hence to the patterns of snow accumulation, snow melt and soil drainage. The fjaeldmark found where snow lies longest is unusual for Tasmania and may be the product of past climatic events and a peculiar parent material. At the generic level there exists a high similarity with the snow patch flora of the Australian Alps.     

Eimeria ochrogasteri n. sp. from the Prairie Vole Microtus ochrogaster*

SYNOPSIS. Eimeria ochrogasteri n. sp. (Coccidia, Eimeriidae) from a prairie vole Microtus ochrogaster (Rodentia, Cricetidae) is described. This is the first recorded coccidium in prairie voles. Sporulated oocysts spherical to ellipsoidal, mean 24.0 by 20.5 μ. Oocyst wall double, outer layer thick, yellow-brown, deeply pitted, inner layer clear. Oocyst residuum varies from many small globules to a coalesced group of large and/or small globules. Polar granule present. Micropyle absent. Sporocysts ovoid with “capped” Stieda body, mean 12.3 by 8.2 μ. Sporocyst residuum present. Sporozoites average 14.9 by 2.9 μ with spherical anterior and oblong posterior refractile globules. This species was found in 1 of 71 voles from Weld county, Colorado.     

The anatomy,taphonomy, taxonomy and systematic affinity of Markuelia: Early Cambrian to Early Ordovician scalidophorans

Abstract: Markuelia is a vermiform, annulated introvertan animal known as embryonic fossils from the Lower Cambrian to Lower Ordovician. Analysis of an expanded and revised dataset for Introverta shows that the precise position of Markuelia within this clade is dependent on the taxa included. As a result, Markuelia is assigned to the scalidophoran total group to reflect uncertainty as to whether it is a stem‐scalidophoran or a stem‐priapulid. The taxonomy of the genus is revised to provide an improved taxonomic framework for material assigned to Markuelia. Five species are recognized: M. secunda Val’kov, M. hunanensis Dong and Donoghue, M. lauriei Haug et al., M. spinulifera sp. nov. and M. waloszeki sp. nov. Finally, the preservation of Markuelia is evaluated in the light of both the taphonomy of the fossil embryos themselves and the experimental taphonomy of the priapulid Priapulus caudatus, which has been proposed as both a close relative and an anatomical analogue of Markuelia.