Early development of the razorback sucker, Xyrauchen texanus (Abbott)

  Fertilized ova of razorback sucker, Xyrauchen texanus, were adhesive for 3 to 4 hours after fertilization. Cleavage was completed at 24 hours, gastrulation occurred at 34 hours, and blood circulation was established at 117 hours. Hatching occurred from 5.2 to 5.5 days after fertilization. Larvae were from 6.8 to 7.3 mm TL at hatching. Yolk was assimilated at 13 days (10 mm TL). All fins were formed and had ossified rays at 64 days (27 mm TL). The unique nuchal keel appeared about 200 days after fertilization.     

Richard Watson

The development of the circular dividing engine in England is traced from Henry Hindley and Jesse Ramsden through the improvements introduced by Ramsden's successors to the self-acting engine of William Simms. Particular emphasis is given to the invention, evolution and transmission of the methods used to achieve accuracy in: dividing the wheel; ratching the teeth and matching them to the endless screw; and mounting the cutter. The procedures adopted by Ramsden and Troughton for correcting initial dividing marks are also described.     

Tree size and understory phytomass production in a western juniper woodland

Understory phytomass production in a western juniper ( Juniperus occidentalis ) woodland was examined relative to tree size in central Oregon in 1983 and 1984. Vegetation was sampled in two zones, the canopy zone (beneath the canopy) and the intercanopy zone (the space between canopies), on two adjacent sites—a lower slope site with shallow soil and an upper slope site with deeper soil. Sampling was stratified into three tree size classes. Individual species production was significantly affected by tree size and location relative to tree canopy. Production of bottlebrush squirreltail, bluebunch wheatgrass, cheatgrass, miscellaneous annual grasses, perennial forbs, and annual forbs increased with increasing tree size. Sandberg bluegrass production was greater in the intercanopy than the canopy zone, while production of bottlebrush squirreltail, bluebunch wheatgrass, miscellaneous annual grasses, and both perennial and annual forbs was greater in the canopy zone. Production of cheatgrass was determined by the interaction of tree size and zone. Phytomass relationships were expressed to a greater degree on the upper slope site, where total production exceeded that of the lower slope site by approximately 50% the second year of the study. Individual trees appear to exert a great influence on associated vegetation as western juniper woodlands progress from the seedling (tree establishment) phase to closed stands of mature trees. Original community dominants appear to be spatially segregated beneath tree canopies and associated with large trees, while formerly less common species, such as cheatgrass, come to dominate the entire site.     

Range extension of Helianthus spp. (Asteraceae) in Arizona and Utah

Two populations of Helianthus niveus (Benth.) Brandegee ssp. canescens (A. Gray) Heiser were discovered in northern Arizona extending the range 300 miles north for this species. Helianthus deserticola Heiser range was extended 100 miles east in both Arizona and Utah.     

Sperm viability in the reproductive tract of females in a population of Sceloporus mucronatus exhibiting asynchronous reproduction

Asynchronous reproduction is a common phenomenon in high-elevation populations of lizards from Central México. Sperm storage in the reproductive tract of females is the mechanism for making oocyte fertilization possible. Our study addresses questions related to functional oviductal sperm storage of females mating on different dates throughout the reproductive season. A population of Sceloporus mucronatus with copulation in the summer and ovulation in the fall was chosen for this experiment. Eleven females that copulated in the field during June and 13 females that copulated in captivity during August were maintained in the laboratory until parturition. The number of pregnant females and the litter sizes produced in each experimental group were indicative of the viability of the stored sperm. Sperm stored in the reproductive tract of females were able to fertilize eggs after 4 months. No significant differences were found in the number of pregnant females between the 2 experimental groups nor in the litter sizes that they produced. We found that the amount of time sperm were held in the female reproductive tract (ca. 3 months) had no effect on the capacity of sperm to fertilize eggs. Histological examination of 8 oviducts collected before the mating season eliminated the possibility of sperm storage from one year to the next. In this system, sperm retention could have evolved as a response mechanism to deal with the asynchrony between sexes in the reproductive cycles. However, we cannot rule out alternative hypotheses.     

Nesting and summer habitat use by translocated Sage Grouse ( Centrocercus Urophasianus ) in central Idaho

We translocated 196 Sage Grouse ( Centrocercus urophasianus into Sawtooth Valley, Idaho, during March-April 1986-87 to augment a small resident population. Forty-four grouse equipped with radio transmitters were monitored through spring and summer. Nest sites ( n = 6) had greater ( P = .032) horizontal cover than did independent random plots ( n = 7). During summer, grouse used sites ( n = 50) with taller live and dead shrub heights, greater shrub canopy cover, and more ground litter ( P n = 50) 50-300 m from use sites. Distance to edge and mountain sagebrush ( Artemisia tridentata vaseyana ) density best separated use sites from independent random plots in logistic regression analysis and correctly classified 64% of the use sites and 78% of the independent random plots. Sage Grouse used sties that had narrower frequency distributions for many variables than did independent plots ( P < .04), suggesting selection for uniform habitat.     

Grassland bird associations with introduced and native grass Conservation Reserve Program fields in the Southern High Plains

We examined relative abundances of grassland birds among Conservation Reserve Program (CRP) fields seeded with 2 monocultures of introduced grass species and 2 mixes of native grasses in the Southern High Plains of Texas. We assessed bird compositions among these 4 cover types and between the cover types pooled into categories of introduced and native fields. Breeding season bird diversity and total abundance did not differ among cover types or between introduced and native fields. Grasshopper Sparrows ( Ammodramus savannarum ), Cassin&rsquo;s Sparrows ( Aimophila cassinii ), and Western Meadowlarks ( Sturnella neglecta ) accounted for more than 90% of breeding season detections. Grasshopper Sparrows were the most abundant and found in all cover types. Cassin&rsquo;s Sparrows were 38% to 170% more abundant among the native seed mix without buffalograss ( Buchlo&euml; dactyloides ) compared to 3 other cover types. Although this association was statistically lost when cover types were pooled into introduced or native fields ( U = 93.5, P = 0.91), the species was still 50% more abundant among native CRP than introduced CRP fields. Meadowlarks occurred ubiquitously but at very low numbers during the breeding season. During winter, avian abundance was 44% greater among native CRP than introduced CRP fields. Meadowlarks, Horned Larks ( Eremophila alpestris ), and Savannah Sparrows ( Passerculus sandwichensis ) accounted for 94% of all winter detections. Meadowlarks occurred ubiquitously, but Horned Larks and Savannah Sparrows were 157% and 96% more abundant, respectively, among native CRP than introduced CRP fields. Our data suggest that monocultures of introduced grasses may benefit some bird species but also that native seed mixes may have a more positive influence through increased diversity and abundance of grassland birds. However, pooling cover types into the broader categories of introduced or native grasses may dampen or occlude biologically meaningful results. It may be prudent to avoid broad categorization of CRP fields based solely on native or introduced grass cover when assessing habitat associations of grassland birds.     

Life histories of stoneflies (Plecoptera) in the Rio Conejos of southern Colorado

Thirty-one stonefly species representing eight families were collected during the March 1987 to May 1990 study period. Genera represented by more than one species included Capnia, Utacapnia, Taenionema, Suwallia, Triznaka, Isogenoides, and Isoperla . Peak species richness was recorded on or near the summer solstice in 1988 and 1989. Climatic differences between years were reflected in nymphal development and emergence phenology of most species. New or important corroborative life history data are presented for 11 stonefly species of this assemblage. The hyporheic nymphal development of most cholroperlid species limited the number of early instars sampled and our capacity to interpret voltinism. Limited nymphal data suggested a univoltine-slow cycle for Plumiperla diversa (Frison). Adults of Suwallia pallidula (Banks) and S. wardi (Banks) were present for an extended summer period, but the bulk of their respective emergence times was temporally separated. Isogenoides zionensis Hanson, Pteronarcella badia (Hagen), and Pteronarcys californica Newport were all shown for the first time to have a 9-10 mo egg diapauses, and all three species have a semivoltine life cycle. Skwala Americana (Klápalek) and Isoperla fulva Claassen were further confirmed to have univoltine-slow cycles. Univoltine-fast and univoltine-slow life cycles are reported for the first time in I. phalerata and I. quinquepunctata , respectively. Regression analysis revealed that six of the eight abunduant species had extended emergence patterns (slopes of < 5%/d), while only two had synchronous patterns. Warmer spring and summer temperatures in 1989 increased the slopes for five of the eight species studied, but did not change their synchrony designation. Nine of 11 abundant species advanced their median emergence date in 1989 over 1988. This and the higher slope values are consistent with a hurried nymphal development and narrower emergence period due to the warmer thermal regime of 1989.     

Basidiomycetes that decay junipers in Arizona. II

Five additional species of wood rotting basidiomycetes on Arizona junipers are described and illustrated. &nbsp; All cause a white rot of dead, fallen trees. Leptosporomyces juniperinus is proposed as a new species. Vararia fibra is reported from the United States for the first time.