Observer Bias in Anuran Call Surveys

ABSTRACT Amphibian monitoring programs rarely question the quality of data obtained by observers and often ignore observer bias. In order to test for bias in amphibian call surveys, we sampled 29 clusters of wetlands from the Rainwater Basin, Nebraska, USA, totaling 228 functionally connected wetlands. Sampling consisted of 3-minute stops where volunteers recorded species heard and made digital recordings. Based on 627 samples, we examined 3 types of observer bias: omission, false inclusion (commission), and incorrect identification. Misidentification rates ranged from 4.2% to 18.3%. Relatively high and unquantified error rates can negatively affect the ability of monitoring programs to accurately detect the population or abundance trends for which most were designed.     

The effect of environmental parameters on growth,cholinesterase activity and glutathione S-transferase activity in the earthworm (Apporectodea caliginosa)

The effect of age and environmental parameters on growth, cholinesterase (ChE), and glutathione S-transferase (GST) activities were assessed in juvenile Apporectodea caliginosa earthworms. Earthworms were maintained in three types of soil- loam, sandy, and clay- at a range of moisture contents (15-30%), and temperatures (5-20 C). Earthworm age (1-3 months) had no significant affect on ChE activity. Growth rates were influenced by all environmental parameters tested and these effects were interrelated. Optimum conditions for growth appeared to be in loam or sandy soil with 25-30% moisture at 10-15 C. The GST activity was influenced by soil temperature and activity was significantly higher at 15 C than at 5 C and 10 C. Soil type also influenced GST activity and this influence was dependent on moisture content. In sandy soil GST activity was significantly lower at 30% moisture than at lower moisture contents, in loam soil GST activity was significantly higher at 15% moisture than at higher moisture contents, while in clay soil GST activity was not affected by moisture content. These results indicate that in field experiments when evaluating GST activity soil temperature and soil type need to be consistent between control and 'contaminated sites'. ChE activity was only affected by temperature, so this should be considered when comparing control and treatedareas.     

Correlation Between Nest and Duckling Survival of Mallards Breeding in Saskatchewan

Abstract: Few studies have estimated reproductive and survival parameters of breeding ducks simultaneously, although such efforts can reveal relationships among vital rates. We estimated survival of mallard (Anas platyrhynchos) nests and duckling on 8 study sites in south-central Saskatchewan during spring and summer 2000 and 2001. We observed a strong positive correlation between these parameters (r = 0.914) and through analysis of residual values found 14% of the relationship was explained by a predator-removal treatment, 26% by year effects, 44% by spatial variation, and 16% unexplained. Potential mechanisms include similar environmental factors influencing both parameters (e.g., predators) and positive density dependence. Information regarding covariation among vital rates is important in construction and interpretation of population growth models describing population dynamics of mallards and other upland-nesting ducks.     

Changes in Agriculture and Abundance of Snow Geese Affect Carrying Capacity of Sandhill Cranes in Nebraska

ABSTRACT The central Platte River valley (CPRV) in Nebraska, USA, is a key spring-staging area for approximately 80% of the midcontinent population of sandhill cranes (Grus canadensis; hereafter cranes). Evidence that staging cranes acquired less lipid reserves during the 1990s compared to the late 1970s and increases in use of the CPRV by snow geese (Chen caerulescens) prompted us to investigate availability of waste corn and quantify spatial and temporal patterns of crane and waterfowl use of the region. We developed a predictive model to assess impacts of changes in availability of corn and snow goose abundance under past, present, and potential future conditions. Over a hypothetical 60-day staging period, predicted energy demand of cranes and waterfowl increased 87% between the late 1970s and 1998–2007, primarily because peak abundances of snow geese increased by 650,000 and cranes by 110,000. Compared to spring 1979, corn available when cranes arrived was 20% less in 1998 and 68% less in 1999; consequently, the area of cornfields required to meet crane needs increased from 14,464 ha in 1979 to 32,751 ha in 1998 and 90,559 ha in 1999. Using a pooled estimate of 88 kg/ha from springs 1998–1999 and 2005–2007, the area of cornfields needed to supply food requirements of cranes and waterfowl increased to 65,587 ha and was greatest in the eastern region of the CPRV, where an estimated 54% of cranes, 47% of Canada geese (Branta canadensis), 45% of greater white-fronted geese (Anser albifrons), and 46% of snow geese occurred during ground surveys. We estimated that a future reduction of 25% in available corn or cornfields would increase daily foraging flight distances of cranes by 27–38%. Crane use and ability of cranes to store lipid reserves in the CPRV could be reduced substantially if flight distance required to locate adequate corn exceeded a physiological maximum distance cranes could fly in search of food. Options to increase carrying capacity for cranes include increasing accessibility of cornfields by restoring degraded river channels to disperse roosting cranes and increasing wetland availability in the Rainwater Basin to attract snow geese using the CPRV.     

Strong population structure characterizes weediness gene evolution in the invasive grass species Brachypodium distachyon

Mediterranean annual grasses have invaded California and have replaced vast areas of native grassland. One of these invasive grasses is Brachypodium distachyon , a new model species for the grasses with extensive genomic resources and a nearly completed genome sequence. This study shows that the level of genetic variation in invaded California grasslands is lower compared to the native range in Eurasia. The invaded regions are characterized by highly differentiated populations of B. distachyon isolated by distance, most likely as a result of founder effects and a dearth of outcrossing events. EXP6 and EXP10 encoding α-expansins responsible for rapid growth, and AGL11 and AGL13 encoding proteins involved in vegetative phase regulation, appear to be under purifying selection with no evidence for local adaptation. Our data show that B. distachyon has diverged only recently from related Brachypodium species and that tetraploidization might have been as recent as a few thousand years ago. Observed low genetic variation in EXP10 and AGL13 appears to have been present in Eurasia before tetraploidization, potentially as a result of strong selective pressures on advantageous mutations, which are most likely responsible for its fast growth and rapid completion of its life cycle.     

Response of Deer to Containment by a Poly-Mesh Fence for Mitigating Disease Outbreaks

Abstract: Rapidly deployable and effective methods are needed to contain free-ranging deer (Odocoileus spp.) during acute disease outbreaks. We evaluated efficacy of a 2.1-m-tall polypropylene mesh (poly-mesh) fence for containing ≥15 free-ranging white-tailed deer (O. virginianus) within a 42-ha area in eastern Nebraska, USA. We observed a 99% decrease in deer leaving the enclosure area after we installed fencing (1 deer jumped; 0.02 deer/hr) compared with prefence rates (5.26 deer/hr). However, 8 deer (53% of censused population) escaped the enclosure during a census drive after our study. Poly-mesh fencing may be effective in temporarily containing free-ranging deer during minimally disruptive deer removal actions such as trapping or sharpshooting.     

A field survey of dioecious plants in Israel: sex ratio in seven rare species

Sex ratio was tested in seven rare dioecious species in Israel. This was in order to complete a previously published sex ratio survey of the other 41 dioecious species in Israel, and to examine further the hypothesis that sex ratio in natural populations is usually 1:1. One population was tested in each of five rare wild species. In addition, one rare feral population was tested in each of two non-native, naturalized tree species. Sex ratio in all seven species tested was not different from the expected 1:1. These results strengthen the suggestion that in natural populations of dioecious plants sex ratio is usually 1:1.