Comment

Vector BiTE RCN goes live!

Want to participate in a new NSF funded Research Coordination Network on Vector Behavior in Transmission Ecology (Vector BiTE)? Visit our splash page to sign up: http://www.johnson-gramacy.com/vectorbite/

The goal of the RCN is to connect researchers in vector ecology, behavior, and physiology across systems and approaches, and to develop an online database for vector trait data and population time series. We welcome researchers at all stages to participate. Our first meeting will take place in Clearwater, FL on March 23-25 and some travel funds are available!

Comment

Study: With climate change, malaria risk in Africa shifts, grows

Comment

Study: With climate change, malaria risk in Africa shifts, grows

Nov. 24, 2015

GAINESVILLE, Fla. – A larger portion of Africa is currently at high risk for malaria transmission than previously predicted, according to a new University of Florida mapping study.

Under future climate regimes, the area where the disease can be transmitted most easily will shrink, but the total transmission zone will expand and move into new territory, according to the study, which appears in the current issue of the journal Vector-Borne and Zoonotic Diseases.

By 2080, the study shows, the year-round, highest-risk transmission zone will move from coastal West Africa, east to the Albertine Rift, between the Democratic Republic of Congo and Uganda. The area suitable for seasonal, lower-risk transmission will shift north into coastal sub-Saharan Africa.

Most striking, some parts of Africa will become too hot for malaria.

The overall expansion of malaria-vulnerable areas will challenge management of the deadly disease, said lead author Sadie Ryan, an assistant professor of geography at the University of Florida who also is affiliated with UF’s Emerging Pathogens Institute.

Malaria will arrive in new areas, posing a risk to new populations, she said, and the shift of endemic and epidemic areas will require public health management changes.

“Mapping a mathematical predictive model of a climate-driven infectious disease like malaria allows us to develop tools to understand both spatial and seasonal dynamics, and to anticipate the future changes to those dynamics,” Ryan said.

Cerebral malaria, caused by the parasite Plasmodium falciparum transmitted by the Anopheles gambiae mosquito, is the most deadly form of the disease, killing around 584,000 people each year. Malaria can cause organ failure, unconsciousness, and coma, if left untreated, and is a major cause of decreased economic productivity in affected regions.

The study uses a model that takes into account the real, curved, physiological responses of both mosquitoes and the malaria parasite to temperature. This model shows an optimal transmission temperature for malaria that, at 25 degrees Celsius, is 6 degrees Celsius lower than previous predictive models.  

This work will play an important role in helping public health officials and NGOs plan for the efficient deployment of resources and interventions to control future outbreaks of malaria and their associated societal costs, Ryan said.

The collaborative research team includes experts in epidemiology, public health, ecology, entomology, mathematical modeling and geography. In addition to Ryan, other team members are Amy McNally (NASA), Leah Johnson (University of South Florida), Erin A. Mordecai (Stanford University), Tal Ben-Horin (Rutgers), Krijn Paaijmans (Universitat de Barcelona) and Kevin D. Lafferty (University of California, Santa Barbara).

The work expands upon the team’s prior work at the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara.

Comment

Science Pumpkins

Comment

Science Pumpkins

We found a good use for our old fungal cultures, and practiced our knife-wielding skills on some pumpkins last month. Sadly, we did not win any Bio department competitions, but we'll get 'em next year. Fungus Culture pumpkin by Erin Spear, Grass Roots pumpkin by Caroline Daws, and Anopheles gambiae pumpkin by Erin Mordecai.

Comment

Jasper Ridge field experiment up and running

Comment

Jasper Ridge field experiment up and running

With the heroic efforts of Caroline, Erin S., our fantastic undergraduate team (Johannah, Liz, and Songhee), and honorary lab member Joe Sertich, we counted and weighed seeds, glued stuff to other stuff, and dug holes with pitchforks to get our big field experiment deployed in Jasper Ridge! Special thanks to the Jasper Ridge staff for installing our silt fence.

The experiment will measure the demographic rates (survival, germination, reproduction, competition) of five California grassland plant species and how they respond to fungal infection. The plants, two native perennial grasses and three exotic annual grasses, share a lot of foliar fungal pathogens. We will manipulate fungal pathogen abundance using field inoculations and fungicide. Over the course of the year, we will be tracking pathogen abundance and community composition as well as plant demography. With this information, we will parameterize population growth models to ask how pathogens influence plant population growth and the outcome of competition. We'll test the model predictions using other plants that naturally vary in plant composition, where we'll experimentally manipulate pathogens.

Stay posted to see our progress!

Comment

Mordecai Lab goes to Santa Cruz

Comment

Mordecai Lab goes to Santa Cruz

We had such a great time with our undergraduate Johannah Farner and interns Divya Ramani and Ryan Tabibi this summer that we went to the Santa Cruz Boardwalk to celebrate. Unfortunately Ryan had already left for school in Asheville, North Carolina, but future Banana Slug Divya was left to show us around her new college town. We all enjoyed riding the Giant Dipper, and we rode the Fireball but only Erin M. enjoyed it. The ocean was so warm from El Nino and The Blob that we waded around in the water for awhile. Good times were had by all, especially when we recovered from the Fireball. Divya celebrated with a lab selfie.

Comment

Comment

Former undergraduate Joe Napier's paper accepted at Oecologia

Wake Forest graduate Joe Napier worked on a summer project with Erin M. and Rob Heckman last summer at the University of North Carolina. His project asked how drought and herbivory (clipping) affected competition between two common grass species. He found that clipping ameliorated the effect of drought for one species. Using a model parameterized with the greenhouse experiment data, he asked whether environmental fluctuation in water availability and herbivory could stabilize coexistence of the two grass species and found that it did not. The paper is provisionally accepted at Oecologia. Joe is now a PhD student with Feng-Sheng Hu at the University of Illinois.

Comment

Comment

Mordecai speaking at Stanford November 2

Check out Erin Mordecai's talk at the Center for International Security and Cooperation, on November 2 at 11:30 am. Location: CISAC Central Conference Room, Encina Hall, 2nd Floor, 616 Serra St., Stanford, CA 94305. Here's what she'll be talking about:

Concerns are mounting that changes in climate, land use, species invasions, and connectivity are changing the global landscape of infectious diseases. Ecological complexity makes these anthropogenic effects on infectious disease difficult to predict. Using data-driven mathematical models, I will show how mosquito-transmitted diseases such as malaria, dengue, and chikungunya may shift with changing climate. I will then discuss sources of uncertainty and how ecological understanding can help to mitigate future shifts in disease risk. Finally, I will introduce the new Center for Disease Ecology, Health, and Development based at Stanford University, which will work to improve human health and well-being through ecological solutions to infectious disease.

Comment

Comment

Virus coexistence paper accepted in American Naturalist

Our paper on the community ecology of plant viruses was accepted in American Naturalist! In it, we use a three-virus, two-vector, one-plant model parameterized with tons of empirical data on Barley Yellow Dwarf Viruses to study the mechanisms that maintain virus coexistence. It turns out that multiple virus species coinfecting individual plants is critical: without coinfection, viruses couldn't coexist, but even very rare coinfections (8% success rate) strongly promote coexistence. But coinfection alone isn't enough. A tradeoff between vector generality (using more than one vector species) and specialization (transmitting efficiently in a single vector) sustains the coexistence of two closely related BYDV species that strongly compete. Finally, competitive exclusion or coexistence depends on aphid density in interesting ways; for example, vector specialist virus MAV can exclude vector generalist PAV when their shared vector is common, unless a second vector is also abundant. And even when long-term competitive exclusion occurs, we observe a lot of coinfected plants en route to exclusion. This work tells a lot about what kinds of pathogen coexistence and life history tradeoffs can sustain diverse pathogen communities in the face of strong competition for hosts and vectors.

Mordecai, E.A., Gross, K., Mitchell, C.E. Within-host niche differences and fitness tradeoffs promote coexistence of plant viruses. in press. American Naturalist.

Comment

Comment

Mathematica Demonstration

Back in grad school, I put together this visualization of a model based on the world's most charismatic plant pathogen: Black Fingers of Death! The model explores how Black Fingers of Death might affect the outcome of competition between to grass host species, based on the biology of transmission and tolerance (unknown at the time). Check out the Mathematica Demonstration here.

 

Comment

Comment

New papers!

Keep your eye out for some new papers coming out in the next few months! In our Ecology paper, we show that native California grasses are hovering at the edge of coexistence and competitive exclusion by exotic grasses. In our PLoS ONE paper, we infect two grass species--one native and one introduced in California--with up to three viruses and show that infection reduces biomass much more severely in the exotic grass.

Mordecai, E.A., Molinari N.A., Stahlheber, K., Gross, K., D’Antonio, C. Controls over native perennial grass exclusion and persistence in annual-invaded California grasslands. Ecology.

Mordecai, E.A., Hindenlang, M., Mitchell, C.E. Differential impacts of virus diversity on biomass production of a native and an exotic grass host. PLoS ONE.

 

Comment