Animal Migrations: Endangered Phenomena

Current conservation research focuses on diminishing speciesdiversity, minimal viable populations, and on the successivedemise of habitats and populations that leads species to extinction.In this paper we utilize the monarch butterfly's remarkablemigration and overwintering biology as a paradigm of a new conservationtheme: endangered phenomenon. An endangered phenomenon is aspectacular aspect of the life history of an animal or plantspecies involving a large number of individuals that is threatenedwith impoverishment or demise; the species per se need not bein peril, rather, the phenomenon it exhibits is at stake. Weenvision the near future with increasing numbers of speciesreduced in range and so constrained in numbers that they canno longer exhibit these characteristic spectacles.     

On partial local smoothing rules for curve estimation

We compare the performances of local and global rules for smoothingparameter choice, in terms of asymptotic mean squared errorsof the resulting estimators. In some instances there is surprisinglylittle to choose between local and global approaches; our analysisidentifies contexts where the differences are small or large.This work motivates development of smoothing rules that forma ‘half-way house’ between local and global smoothing.There, interpolation provides a basis for partial local smoothing.A key result shows that interpolation on even a coarse gridcan produce a very good approximation to full local smoothing.Our theoretical and numerical results lead us to suggest linearinterpolation of a bandwidth obtained by integral approximationson discrete intervals.     

Long-term Population Trends in White-Footed Mice and the Impact of Supplemental Food and Shelter

Central to most models of population regulation is the ideathat the degree of intraspecific competition is in some wayproportional to the availability of limiting resources. Althoughlaboratory research has demonstrated a number of proximate mechanismsby which behavior might affect population growth, little isknown about the resources that are actually limiting populationdensity in the field or about how animals might compete forthem. Long-term field studies reveal that the white-footed mouse,Peromyscus leucopus, exhibits two types of pronounced changesin density: intra-annual (seasonal) and inter-annual. The formerseem to be due ultimately to climate and the lack of winterbreeding, but populations often decline sharply in late summerin the midst of plentiful food; fall recruitment of new animalsis density-dependent and usually poor. Differences in peak densitiesfrom one year to the next as high as 13-fold have been recorded. Weather, shelter, and food are possible ultimate limiting resources.Food has received themost attention, but supplemental feedingexperiments have yielded mixed results. A review of the socialbehavior of this polygnous species suggests that each sex islimited by different combinations of factors. Females may defenda food source and nest sites; males may search actively forfemales at low adult densities, covering large areas, and defendaccess to females at high adult densities. Additional long-term field studies are needed, both to providedirection to laboratory research on proximate mechanisms andto provide the data base for understanding the role of weather,food, and shelter as ultimate limiting factors. Enough short-termstudies have been published to permit comparisons across habitatsand through time which will give a better perspective on climateand habitat variables. Field experiments are necessary to demonstratethe operation of proximate behavioral, physiological, and geneticmechanisms of population regulation in natural populations.     

Localization of ATPase Activity on the Plasmalemma of Scutellar Epithelial Cells of Germinating Barley (Hordeum vulgare L.)

Chaffey, N. J. and Harris, N. 1985. Localization of ATPase activityon the plasmalemma of scutellar epithelial cells of germinatingbarley (Hordeum vulgare L.).—J. exp. Bot 36: 1612–1619. ATPase activity has been localized at an ultrastructural levelin the absorptive region of the scutella of germinating barley(Hordeum vulgare L.). The enzyme is localized on the plasmalemmaof the epithelial cells. Using the Gomori reaction the depositionof reaction product on the plasmalemma, which is dependent uponthe presence of supplied ATP, was precluded or reduced by theinhibitors orthovanadate, mercuric chloride and DCCD, whilstß-glycerophosphate would not act as an alternativesubstrate. The mitochondria demonstrated phosphatase activitywith both ATP and ß-glycerophosphate as substrate.The results are discussed in relation to the active uptake ofmetabolites by the scutellum during germination and the structuralmodification of the plasmalemma of the epithelial cells to formplasmatubules. Key words: ATPase, Hordeum vulgare L., localization (ultrastructural)     

Adventitious Root Formation in Veronica Spp.

Species of the genus Veronica differ in habitat preferences,growth form and in adventitious root production. The annualspecies rarely or never produce adventitious roots in intactplants in the field but some, for example V. persica and V.arvensis will root vigorously from single node stem segmentsin culture. Others, such as V. agrestis require the presenceof IAA for substantial levels of root formation to occur incultured stem segments. Veronica hederifolia cuttings rarelyproduce roots. Stem cuttings of the perennial species, in general,rooted more vigorously than those of annual plants. Both V.fihiformis and V. serpyllifolia root very strongly. The position of root production from the stem cuttings differedfrom species to species. Roots arose either from the node, theregion of the base or at some intermediate point. Veronica arvensis,V. chamaedrys and V. persica rooted mainly from the basal regionwhereas V. filiformis rooted mainly from the node. Veronicaserpyllifolia cuttings rooted at both of these locations. Veronica filiformis, a perennial species that is infertile inBritain, produces root primordia in intact plants at nodes whichare close to the shoot apex. Thus, even very young stem segmentshave ‘preformed’ root primordia. For this reason,detached stem segments of V. filiformis root very rapidly andthis probably has been of great significance in its successfulinvasion and spread in lawns and short turf areas. Veronica spp., adventitious roots, indol-3-ylacetic acid, root primordia, vegetative reproduction     

How do elevated CO2 and O3 affect the interception and utilization of radiation by a soybean canopy?

Net productivity of vegetation is determined by the product of the efficiencies with which it intercepts light (?_i) and converts that intercepted energy into biomass (?_c). Elevated carbon dioxide (CO₂) increases photosynthesis and leaf area index (LAI) of soybeans and thus may increase ?_i and ?_c; elevated O₃ may have the opposite effect. Knowing if elevated CO₂ and O₃ differentially affect physiological more than structural components of the ecosystem may reveal how these elements of global change will ultimately alter productivity. The effects of elevated CO₂ and O₃ on an intact soybean ecosystem were examined with Soybean Free Air Concentration Enrichment (SoyFACE) technology where large field plots (20‐m diameter) were exposed to elevated CO₂ (～550 μmol mol^?1) and elevated O₃ (1.2 × ambient) in a factorial design. Aboveground biomass, LAI and light interception were measured during the growing seasons of 2002, 2003 and 2004 to calculate ?_i and ?_c. A 15% increase in yield (averaged over 3 years) under elevated CO₂ was caused primarily by a 12% stimulation in ?_c , as ?_i increased by only 3%. Though accelerated canopy senescence under elevated O₃ caused a 3% decrease in ?_i, the primary effect of O₃ on biomass was through an 11% reduction in ?_c. When CO₂ and O₃ were elevated in combination, CO₂ partially reduced the negative effects of elevated O₃. Knowing that changes in productivity in elevated CO₂ and O₃ were influenced strongly by the efficiency of conversion of light energy into energy in plant biomass will aid in optimizing soybean yields in the future. Future modeling efforts that rely on ?_c for calculating regional and global plant productivity will need to accommodate the effects of global change on this important ecosystem attribute.     

Piecing together an integrative taxonomic puzzle: microsatellite,wing shape and aedeagus length analyses of Bactrocera dorsalis s.l. (Diptera: Tephritidae) find no evidence of multiple lineages in a proposed contact zone along the Thai/Malay Peninsula

Bactrocera dorsalis (Hendel) and B. papayae Drew & Hancock represent a closely related sibling species pair for which the biological species limits are unclear; i.e. it is uncertain if they are truely two biological species, or one biological species which has been incorrectly split taxonomically. The geographical ranges of the two taxa are thought to abut or overlap on or around the Isthmus of Kra, a recognised biogeographic barrier located on the narrowest portion of the Thai Peninsula. We collected fresh material of B. dorsalis s.l. (i.e. B. dorsalis s.s.+ B. papayae) in a north–south transect down the Thai Peninsula, from areas regarded as being exclusively B. dorsalis s.s., across the Kra Isthmus, and into regions regarded as exclusively B. papayae. We carried out microsatellite analyses and took measurements of male genitalia and wing shape, both used previously to separate the taxa. No significant population structuring was found in the microsatellite analysis, consistent with one, predominantly panmictic population. Both morphological datasets showed consistent, clinal variation along the transect, without disjunction. No evidence supported historical vicariance driven by the Isthmus of Kra, and no dataset supported the current taxonomy of two species. Rather, within and across the area of range overlap or abutment between the two species, only continuous morphological and genetic variation was recorded. Recognition that morphological traits previously used to separate these taxa are continuous, and that there is no genetic evidence for population segregation in the region of suspected species overlap, is consistent with a growing body of literature that reports no evidence of biological differentiation between these taxa.     

Harvest Refugia in Marine Invertebrate Fisheries: Models and Applications to the Red Sea Urchin, Strongylocentrotus franciscanus

Benthic marine invertebrates with planktonic larvae may exhibitAllee effects in reproduction or recruitment. Hydrodynamic considerationsand experimental evidence suggest that species broadcastinggametes suffer greatly reduced fertilization efficiencies asdensities decline. There is also evidence for some species,including the red sea urchin, that post-dispersal recruitmentsuccess declines at low densities of adults, if adults provideshelter from predators or other sources of mortality. Speciesdisplaying strong Allee effects may be susceptible to catastrophicpopulation collapses with slight increases in mortality dueto harvesting or natural causes. A simple two patch logisticmodel suggests that the establishment of a harvest refuge isnecessary to prevent collapses and maintain sustainable catchesat high levels of harvesting effort. A more detailed, age structuredmodel based on the biology of the red sea urchin, Strongylocentrotusfranciscanus produces similar results. Effects of harvestingstrategies are sensitive to Allee effects caused by both fertilizationefficiency and the disruption of adult spine canopies. Theoreticalrequirements for the size and spacing of marine reserves dependsupon the dispersal abilities of the target species. Multiplereserves, spaced more closely than the average larval dispersaldistance, appear to be an effective and conservative strategyfor maintaining healthy populations and sustainable levels ofharvest.     

Effects of density-dependence and weather on population changes of English passerines using a non-experimental paradigm

The Common Birds Census documents changes in the populations of the more abundant British land birds. Here we analyse the CBC data for various English passerines to discover the separate effects of weather and of density-dependent feedback on their annual population changes. Density dependence is generally apparent in the data from woodland plots, less so in those from farmland. There are clear effects of weather, particularly in farmland. Prolonged snowfall in winter reduces populations of most species; frost and low temperatures appear much less important. Rainfall in March and April increases numbers censused in the spring but this may be an artefact. We discuss ways in which analyses such as these should be taken forward.
We consider whether this work is respectable science, arguing that monitoring through the CBC goes much further than mere surveillance of numbers, that such monitoring is important in wildlife management, and that density dependence is not a bankrupt paradigm. Long-term data gathering is an essential part of ecological science, even in programmes not designed at the outset to test specific hypotheses.