Sandhill Crane Abundance and Nesting Ecology at Grays Lake,Idaho

Abstract: We examined population size and factors influencing nest survival of greater sandhill cranes (Grus canadensis tabida) at Grays Lake National Wildlife Refuge, Idaho, USA, during 1997–2000. Average local population of cranes from late April to early May, 1998–2000, was 735 cranes, 34% higher than that reported for May 1970–1971. We estimated 228 (SE = 30) nests in the basin core (excluding renests), 14% higher than a 1971 estimate. Apparent nest success in our study (x̄ = 60%, n = 519 nests) was lower than reported for Grays Lake 30–50 years earlier. Daily survival rates (DSRs) of all nests averaged 0.9707 (41.2%). The best model explaining nest survival included year and water depth and their interaction. Nest survival was highest (DSR = 0.9827) in 1998 compared with other years (0.9698-0.9707). Nest survival changed little relative to water depth in 1998, when flooding was extensive and alternative prey (microtines) irrupted, but declined markedly with lower water levels in 2000, the driest year studied. Hypotheses relating nest survival to vegetation height, land use (idle, summer grazing, fall grazing), and date were not supported. In a before-after-control-impact design using 12 experimental fields, nest survival differed among years but not among management treatments (idle, fall graze, fall burn, and summer—graze—idle rotation), nor was there an interaction between year and treatments. However, DSRs in fall-burn fields declined from 0.9781 in 1997–1998 to 0.9503 in 1999–2000 (posttreatment). Changes in the predator community have likely contributed to declines in nest success since the 1950s and 1970s. Our results did not support earlier concerns about effects of habitat management practices on crane productivity. Nest survival could best be enhanced by managing spring water levels. Managers should continue censuses during late April to evaluate long-term relationships to habitat conditions and management.     

Niche segregation and genetic structure of Campylobacter jejuni populations from wild and agricultural host species

Bacterial populations can display high levels of genetic structuring but the forces that influence this are incompletely understood. Here, by combining modelling approaches with multilocus sequence data for the zoonotic pathogen Campylobacter, we investigated how ecological factors such as niche (host) separation relate to population structure. We analysed seven housekeeping genes from published C. jejuni and C. coli isolate collections from a range of food and wild animal sources as well as abiotic environments. By reconstructing genetic structure and the patterns of ancestry, we quantified C. jejuni host association, inferred ancestral populations, investigated genetic admixture in different hosts and determined the host origin of recombinant C. jejuni alleles found in hybrid C. coli lineages. Phylogenetically distinct C. jejuni lineages were associated with phylogenetically distinct wild birds. However, in the farm environment, phylogenetically distant host animals shared several C. jejuni lineages that could not be segregated according to host origin using these analyses. Furthermore, of the introgressed C. jejuni alleles found in C. coli lineages, 73% were attributed to genotypes associated with food animals. Our results are consistent with an evolutionary scenario where distinct Campylobacter lineages are associated with different host species but the ecological factors that maintain this are different in domestic animals such that phylogenetically distant animals can harbour closely related strains.     

Contamination on sandflats and the decoupling of linked ecological functions

Benthic macrofauna can influence inputs and transformations of energy and matter in estuaries, affecting both the stocks of vital materials (e.g. carbon, oxygen) and the rates of key processes (e.g. organic matter decomposition, nutrient uptake). Although a number of studies have identified shifts in functional groups or biological traits in relation to anthropogenic stressors, there have been few field‐based assessments of changes in functioning associated with stress gradients. We used a comparative experimental approach to investigate functioning on two sandflats with differing exposures to urban contaminants. Apart from significant differences in sediment contaminant concentrations (43.2 ± 1.8 mg kg^?1 Zn and 15.6 ± 0.9 mg kg^?1 Pb at the Pollen site; 17.7 ± 0.7 mg kg^?1 Zn and 7.9 ± 0.9 mg kg^?1 Pb at the Waiheke site), the two sandflats were readily comparable: both had similar sediment grain size distributions and were dominated by the same macrofaunal species; and both were in non‐eutrophic New Zealand marine reserves with low ambient sediment organic matter content. To better understand the effects of contaminants on biologically mediated transformations of organic matter into inorganic nutrients, we manipulated sediment organic matter content and macrofaunal abundance in standardized treatments at each site. Fluxes of oxygen and ammonium, which are linked to key sandflat processes such as organic matter decomposition and benthic photosynthesis, were measured as response variables 1 week after the experimental manipulations. We predicted more efficient organic matter processing on the uncontaminated flat and thus expected to see elevated ammonium efflux in response to organic enrichment treatments at this site. Higher rates of benthic photosynthesis were predicted for plots with higher ammonium efflux, as ammonium is a readily utilizable form of limiting inorganic nitrogen. We documented significant positive relationships between ammonium uptake and benthic primary production on the uncontaminated flat, but weaker/insignificant relationships at the contaminated site. Our data were consistent with theories of increased variability and a decoupling of system processes with increasing amounts of stress.     

A bioregional analysis of the distribution of rainforest cover,deforestation and degradation in Papua New Guinea

Papua New Guinea (PNG) is an extensively forested country. Recent research suggests that despite commencing a trajectory of deforestation and degradation later than many counties in the Asia–Pacific region, PNG is now undergoing comparable rates of forest change. Here we explore the bioregional distribution of changes in the forest estate over the period 1972–2002 and examine their implications for forest protection. This is undertaken through the development of a novel bioregional classification of the country based on biogeographic regions and climatic zones, and its application to existing forest cover and forest‐cover change data. We found that degradation and deforestation varied considerably across the 11 defined biogeographic regions. We report that the majority of deforestation and degradation has occurred within all the lowland forests, and that it is these forests that have the greatest potential for further losses in the near term. The largest percentage of total change occurred in the east of PNG, in the islands and lowlands of the Bismarck, D'Entrecasteaux, East Papuan Islands and in the South‐East Papua–Oro region. The only region with a significant highlands component to undergo deforestation at a comparable magnitude to the islands and lowland regions was the Huon Peninsula and Adelbert region. Significant changes have also occurred at higher elevations, especially at the interface of subalpine grasslands and upper montane forests. Lower montane forests have experienced proportionally less change, yet it is these forests that constitute the majority of forests enclosed within the protected area system. We find that protected areas are not convincingly protecting either representative areas of PNG's ecosystems, nor the forests within their borders. We conclude by suggesting a more expansive and integrated approach to managing the national forest estate.     

Genetic differentiation between Australian and North American populations of the monarch butterfly Danaus plexippus (L.) (Lepidoptera: Nymphalidae): an exploration using allozyme electrophoresis

Allozyme analysis was used to address the question of the source of the Australian populations of the monarch butterfly Danaus plexippus (L.). The study had three major aims: (1) To compare the levels of diversity of Australian and Hawaiian populations with potential source populations. (2) To determine whether eastern and western North American populations were sufficiently divergent for the Australian populations to be aligned to a source population. (3) To compare the differentiation among regions in Australia and North America to test the prediction of greater genetic structure in Australia, as a consequence of reduced migratory behaviour. The reverse was found, with F _ST values an order of magnitude lower in Australia than in North America. Predictably, Australian and Hawaiian populations had lower allelic diversity, but unexpected higher heterozygosity values than North American populations. It was not possible to assign the Australian populations to a definitive source, although the high levels of similarity of Australian populations to each other suggest a single colonization event. The possibility that the Australian populations have not been here long enough to reach equilibrium is discussed. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 437–452.     

Inbreeding coefficient and heterozygosity–fitness correlations in unhatched and hatched song sparrow nestmates

Heterozygosity–fitness correlations use molecular measures of heterozygosity as proxy estimates of individual inbreeding coefficients (f) to examine relationships between inbreeding and fitness traits. Heterozygosity–fitness correlations partly depend on the assumption that individual heterozygosity and f are strongly and negatively correlated. Although theory predicts that this relationship will be strongest when mean f and variance in f are high, few studies of heterozygosity–fitness correlations include estimates of f based on pedigrees, which allow for more thorough examinations of the relationship between f, heterozygosity and fitness in nature. We examined relationships between pedigree‐based estimates of f, multilocus heterozygosity (MLH) and the probability of survival to hatch in song sparrow nestmates. f and MLH were weakly, but significantly negatively correlated. Inbreeding coefficient predicted the probability of survival to hatch. In contrast, MLH did not predict the probability of survival to hatch nor did it account for residual variation in survival to hatch after statistically controlling for the effects of f. These results are consistent with the expectation that heterozygosity–f correlations will be weak when mean and variance in f are low. Our results also provide empirical support for recent simulation studies, which show that variation in MLH among siblings with equal f can be large and may obscure MLH–fitness relationships.     

Impacts of climate warming and habitat loss on extinctions at species' low-latitude range boundaries

Polewards expansions of species' distributions have been attributed to climate warming, but evidence for climate‐driven local extinctions at warm (low latitude/elevation) boundaries is equivocal. We surveyed the four species of butterflies that reach their southern limits in Britain. We visited 421 sites where the species had been recorded previously to determine whether recent extinctions were primarily due to climate or habitat changes. Coenonympha tullia had become extinct at 52% of study sites and all losses were associated with habitat degradation. Aricia artaxerxes was extinct from 50% of sites, with approximately one‐third to half of extinctions associated with climate‐related factors and the remainder with habitat loss. For Erebia aethiops (extinct from 24% of sites), approximately a quarter of the extinctions were associated with habitat and three‐quarters with climate. For Erebia epiphron, extinctions (37% of sites) were attributed mainly to climate with almost no habitat effects. For the three species affected by climate, range boundaries retracted 70–100 km northwards (A. artaxerxes, E. aethiops) and 130–150 m uphill (E. epiphron) in the sample of sites analysed. These shifts are consistent with estimated latitudinal and elevational temperature shifts of 88 km northwards and 98 m uphill over the 19‐year study period. These results suggest that the southern/warm range margins of some species are as sensitive to climate change as are northern/cool margins. Our data indicate that climate warming has been of comparable importance to habitat loss in driving local extinctions of northern species over the past few decades; future climate warming is likely to jeopardize the long‐term survival of many northern and mountain species.     

Estimation of Occupied and Unoccupied Black-Tailed Prairie Dog Colony Acreage in Colorado

Abstract: Black-tailed prairie dogs (Cynomys ludovicianus) are a species of concern and accurate estimates of occupied area are required to assess their status. We conducted aerial line-intercept surveys to estimate colony areas in Colorado, USA, 2006–2007. Optimal allocation based on results from a previous (2002) survey was used to distribute flight time to sample 28 counties. Uncorrected estimates of active and inactive colony areas from the aerial surveys were 329,529 (SE=16,841) ha and 18,292 (SE=2,366) ha, respectively. We attempted to ground-truth a randomly selected sample of 186 colony intercepts but gained complete access to only 150. Ground-truthing demonstrated that aerial surveys estimated only 96% of the true lengths of colony intercepts but overestimated the proportion of active colonies. Corrected estimates of active and inactive colony areas are 319,165 (SE = 20,105) ha and 42,422 (SE = 11,485) ha, respectively. Because ground-truthing was not conducted in the original 2002 survey, uncorrected estimates from this survey are the appropriate metric to be used for comparison to the 2002 data. Our estimates demonstrated a 29% increase (SE = 6.3) in area occupied since surveys were conducted in 2002. These results are useful to state and federal agencies and other conservation partners in determining the condition of the species when conducting status reviews.     

Assessment of ecological status in U.K. rivers using diatoms

1. The European Union's Water Framework Directive requires all water bodies to achieve ‘good ecological status’ by 2015 and this paper describes a rationale for defining ‘good ecological status’ based on diatoms, a significant component of the biological quality element ‘macrophyte and phytobenthos’. 2. A database of benthic diatom samples collected over the past 20 years was assembled. New sampling, specifically for this project, was undertaken during 2004 to supplement these data. In total 1051 samples were included in the database with matching environmental data. 3. ‘Reference sites’, relatively unimpacted by human activity, were selected from this database by a series of screening steps and these sites were used to develop a site‐specific reference typology. 4. Environmental variables not related to the pressure gradient were used to predict the ‘expected’ Trophic Diatom Index (TDI) values at each site. Site‐specific TDI predictions were used to generate ecological quality ratios (EQRs) ranging from ≥1, where the diatom assemblage showed no impact, to (theoretically) 0, when the diatom assemblage was indicative of major anthropogenic activities. 5. The boundary between ‘high’ and ‘good’ status was defined as the 25th percentile of EQRs of all reference sites. The boundary between ‘good’ and ‘moderate’ status was set at the point at which nutrient‐sensitive and nutrient‐tolerant taxa were present in equal relative abundance. An ecological rationale for this threshold is outlined in the paper.