Rampant drift in artificially fragmented populations of the endangered tidewater goby (Eucyclogobius newberryi)

Habitat fragmentation and its genetic consequences are a critically important issue in evaluating the evolutionary penalties of human habitat modification. Here, we examine the genetic structure and diversity in naturally subdivided and artificially fragmented populations of the endangered tidewater goby (Eucyclogobius newberryi), a small fish restricted to discrete coastal lagoons and estuaries in California, USA. We use five naturally fragmented coastal populations from a 300‐ km spatial scale as a standard to assess migration and drift relative to eight artificially fragmented bay populations from a 30‐ km spatial scale. Using nine microsatellite loci in 621 individuals, and a 522‐base fragment of mitochondrial DNA control region from 103 individuals, we found striking differences in the relative influences of migration and drift on genetic variation at these two scales. Overall, the artificially fragmented populations exhibited a consistent pattern of higher genetic differentiation and significantly lower genetic diversity relative to the naturally fragmented populations. Thus, even in a species characterized by habitat isolation and subdivision, further artificial fragmentation appears to result in substantial population genetic consequences and may not be sustainable.     

Climate change and cattle nutritional stress

Owing to the complex interactions among climate, plants, cattle grazing, and land management practices, the impacts of climate change on cattle have been hard to predict. Predicting future grassland ecosystem functioning relies on understanding how changes in climate alter the quantity of forage produced, but also forage quality. Plant protein, which is a function of plant nitrogen concentrations, and digestible energy limit the performance of herbivores when in short supply; moreover, deficiencies can be expensive to mitigate. To better understand how changes in temperature and precipitation would affect forage protein and energy availability, we analyzed over 21 000 measurements of cattle fecal chemistry acquired over 14 years in the continental US. Our analysis of patterns in forage quality among ecologically defined regions revealed that increasing temperature and declining precipitation decreased dietary crude protein and digestible organic matter for regions with continental climates. Within regions, quality also declined with increased temperature; however, the effects of precipitation were mixed. Any future increases in precipitation would be unlikely to compensate for the declines in forage quality that accompany projected temperature increases. As a result, cattle are likely to experience greater nutritional stress in the future. If these geographic patterns hold as a proxy for future climates, agriculture will require increased supplemental feeds or the consequence will be a decrease in livestock growth.     

Use of Lethal Control to Reduce Habituation to Blank Rounds by Scavenging Birds

Abstract Scavenging bird deterrence frequently fails due to habituation. We demonstrated such habituation by gulls and corvids to blank rounds used in a dawn-to-dusk regime at a landfill site in southern England. We then combined blank rounds with live rounds and shot birds whenever they attempted to land. Gull numbers declined significantly despite only 1.9% of the population being shot. Corvid numbers returned to precontrol levels despite 52.7% of the population being shot. We suggest that shooting reduces gull habituation to blank rounds but is ineffective at reducing habituation by corvids.     

Simulated climate change: are passive greenhouses a valid microcosm for testing the biological effects of environmental perturbations?

This paper considers the use of passive greenhouse apparatus in field experiments investigating the biological consequences of climate change. The literature contains many accounts of such experiments claiming relevance of greenhouse treatment effects to global change scenarios. However, inadequacies in microclimate monitoring, together with incomplete understanding of greenhouse modes of action, cast doubt upon such claims. Here, treatment effects upon temperature (magnitude, range, variation, rates of change), moisture (humidity, precipitation, soil water content), light (intensity, spectral distribution), gas composition, snow cover, and wind speed are reviewed in the context of Intergovernmental Panel on Climate Change (IPCC) predictions. It is revealed that greenhouses modify each of these potentially limiting factors in a complex and interactive manner, but that the relationship between this modification and forecast conditions of climate change is poor. Interpretation of biological responses, and their extrapolation to predictive models, is thus unreliable. In order that future greenhouse experiments may overcome criticisms of artefact and lack of rigour, two amendments to methodology are proposed: (1) objective-orientated design of greenhouse apparatus (2) multiple controls addressing individual environmental factors. The importance of a priori testing of microclimate treatment effects is stressed.     

The use of digital video recorders in pollination biology

1. Digital video recording (DVR) devices, such as the GoPro Hero, have the potential to greatly benefit pollination ecology, but the advantages of digitally recording pollinator activity over direct human observation have not been formally assessed. 2. Two plant taxa, Lavandula angustifolia and Canna ‘sp.’, with differing floral morphology, were used to compare the value of DVR and direct observations in estimating honeybee (Apis mellifera) visitation, flower density and number of flowers visited per foraging bout. 3. The two methods yielded identical results when observing the structurally simple L. angustifolia at both high (10.54 ± 0.52 per plant) and low honeybee density (2.24 ± 0.20 per plant). However, DVR underestimated the number of flowers scored in the field of view (28.7 ± 1.8 direct vs. 22.7 ± 0.9 DVR), the number of honeybees observed (5.3 ± 0.8 direct vs. 3.7 ± 0.7 DVR) and the number of flowers visited during foraging bouts (8.3 ± 1.2 direct vs. 5.5 ± 1.0 DVR) on the more complex Canna ‘sp.’ 4. It is concluded that portable weatherproof DVR devices such as the GoPro Hero are valuable tools for pollination biologists, allowing a single researcher to make simultaneous observations of multiple plants in one or more sites, whilst also allowing the footage to be reviewed. However, DVR devices are limited by their depth and field of view when target plants are large or structurally complex.     

Dynamics of Competition in Populations of Carrot (Daucus carota)

Populations of carrot (Daucus carota) were raised over a widerange of densities (79–5763 plants m^-2) to examine thedynamics of competition in terms of yield–density relationshipsand size variability, and to investigate the effects of nutrientsupply on competition. While the relationship between shootyield and density was asymptotic, the relationship between rootand total yield and density tended to be parabolic. For a giventime and density series the relationship between yield per unitarea and density could best be described by the model: y=w_mD_(1+aD)^b wherey is the yield per unit area,D is density,w_m, a andb arefitted parameters. The parametersw_m anda increased over timebut nutrient availability affected onlyw_m. An extension of thebasic yield-density model is proposed to describe the dynamicsof the yield–density relationship over time: y=kD_{[1+cexp(-rt)]{1+}