Modeling population connectivity by ocean currents,a graph-theoretic approach for marine conservation

The dispersal of individuals among marine populations is of great importance to metapopulation dynamics, population persistence, and species expansion. Understanding this connectivity between distant populations is key to their effective conservation and management. For many marine species, population connectivity is determined largely by ocean currents transporting larvae and juveniles between distant patches of suitable habitat. Recent work has focused on the biophysics of marine larval dispersal and its importance to population dynamics, although few studies have evaluated the spatial and temporal patterns of this potential dispersal. Here, we show how an Eulerian advection–diffusion approach can be used to model the dispersal of coral larvae between reefs throughout the Tropical Pacific. We illustrate how this connectivity can be analyzed using graph theory—an effective approach for exploring patterns in spatial connections, as well as for determining the importance of each site and pathway to local and regional connectivity. Results indicate that the scale (average distance) of dispersal in the Pacific is on the order of 50–150 km, consistent with recent studies in the Caribbean (Cowen, et al. 2006). Patterns in the dispersal graphs highlight pathways for larval dispersal along major ocean currents and through island chains. A series of critical island ‘stepping stones’ are discovered providing potential pathways across the equatorial currents and connecting distant island groups. Patterns in these dispersal graphs highlight possible pathways for species expansions, reveal connected upstream/downstream populations, and suggest areas that might be prioritized for marine conservation efforts.

     

Transmission of Anaplasma marginale Theiler by males of Dermacentor andersoni Stiles fed on an Idaho field-infected, chronic carrier cow

The role of ticks and carrier cattle in epizootics of bovine anaplasmosis was further clarified by demonstrating unequivocally, for the first time, that male ticks fed on a chronic carrier cow naturally infected with Anaplasma marginale can transmit this parasite intrastadially and biologically when subsequently fed on susceptible cattle. These data indicate that field epizootics of acute anaplasmosis may be initiated by males of tick vector species that feed on carrier cattle and subsequently transfer to susceptible cattle.     

Nitrogen and water use efficiency of zucchini squash for a plastic mulch bed system on a sandy soil

Zucchini squash (Cucurbita pepo L.) is an economically important vegetable crop in Florida. Typically, it is intensively managed with high inputs of fertiliser and irrigation water. Our objectives were to evaluate the interaction between fertilisation rates and irrigation treatments, and to quantify nitrate leaching in a plastic mulched/drip irrigated zucchini squash production systems. Three studies were carried out. The first study evaluated different depth placement of drip and fertigation lines on plant growth and fruit yield. Treatments included SUR (both irrigation and fertigation drip lines placed on the surface); S&S (both lines buried 0.15 m deep); and SDI (irrigation line placed 0.15 m below the fertigation line on the surface). The second and third studies compared three different N-rates and different soil moisture sensor-based irrigation strategies. Nitrate-N leaching was monitored by zero tension drainage lysimeters and soil samples. N leaching increased when irrigation and N-rates increased, with values ranging from 2 to 45 kg ha⁻¹ of N. Use of SDI increased yields by 16% compared to the S&S treatment, and reduced nitrate leaching by 93% while increasing the water use efficiency by 75% compared to a fixed 2-h irrigation event per day treatment. Application of N above the standard recommended rate of 145 kg ha⁻¹ did not increase yield, although yields were reduced at the lowest N-rate. The use of soil moisture sensors for automatic irrigation control reduced irrigation application and minimized nitrogen leaching. In addition, combining the soil moisture controlled SDI system that had surface applied fertigation resulted in similar or higher yields, while reducing both water use and potential N leaching because of improved nutrient retention in the root zone.     

Teaching Tolerance? Effects of Conservation Education Programs on Wildlife Acceptance Capacity for the American Alligator

Growing populations of American alligators (Alligator mississippiensis) in human-dominated landscapes present a challenge to wildlife managers concerned with promoting coexistence between humans and alligators. Where structural fixes such as direct removal of animals are not viable options, cognitive fixes such as conservation education programs should be considered. We evaluated the effectiveness of two conservation education programs (classroom-based program, field excursion) on three outcome variables that help define wildlife acceptance capacity for American alligators: beliefs and attitudes, perceived risk, and potential for coexistence. We found respondents who took part in both education programs had more positive beliefs and attitudes toward alligators, and believed in a greater potential for coexistence than individuals in a control group who did not undergo either intervention. Control group respondents also perceived higher risk from alligators. These data suggest that conservation education programs can impact stakeholder beliefs, attitudes, and perceptions, ultimately influencing acceptance capacity for predators.     

Do birdwatchers buy the duck stamp?

Bird watchers (birders) are stakeholders in wildlife conservation; yet, few federal programs provide formal mechanisms for birders to contribute economically to conservation. One exception is the Migratory Bird Hunting and Conservation Stamp (duck stamp), a unique conservation tool historically aimed at waterfowl hunters that generates revenue to acquire and protect wetland habitat. This article examined duck stamp purchasing behavior among birders participating in the National Audubon Society’s annual citizen science project, the Christmas Bird Count (CBC) (n = 3,072). Twenty percent of CBC participants had purchased a duck stamp between 2013 and 2015, and about 40% of those purchasers were also hunters. Birding specialization was a key predictor of duck stamp purchasing behavior, with highly specialized nonhunting birders purchasing stamps at rates approximately equal to hunters. Future research should continue to explore reasons birders buy (or do not buy) duck stamps and the broader implications on wildlife conservation.     

Impacts of rising atmospheric carbon dioxide on model terrestrial ecosystems

In model terrestrial ecosystems maintained for three plant generations at elevated concentrations of atmospheric carbon dioxide, increases in photosynthetically fixed carbon were allocated below ground, raising concentrations of dissolved organic carbon in soil. These effects were then transmitted up the decomposer food chain. Soil microbial biomass was unaffected, but the composition of soil fungal species changed, with increases in rates of cellulose decomposition. There were also changes in the abundance and species composition of Collembola, fungal-feeding arthropods. These results have implications for long-term feedback processes in soil ecosystems that are subject to rising global atmospheric carbon dioxide concentrations.