Final stretch: o nordeste

April 13, 2016

By Thomas S. Jenkinson

The Brazilian Atlantic Forest chytridiomycosis sampling transect is complete! Our collaborative team has finished a full, north-south survey of Bd infection in the Brazilian Atlantic Forest. Over the three years since its inception, our research team has collected and analyzed skin swabs from over 2400 individual amphibians, and isolated over 120 Bd cultures for genetic and phenotypic studies. To complete the last segment of the Atlantic Forest transect in 2015, we sampled the northeastern states of Rio Grande do Norte, Paraiba, Pernambuco, Sergipe, and northern Bahia. This last stretch of the transect was completed in collaboration with Dr. Tamí Mott’s research group from the Federal University of Alagoas (UFAL) and again with our collaborator Dr. Felipe Toledo from the Universidade Estadual de Campinas (UNICAMP). This trip, the team drove over 1000 km across the Nordeste region of Brazil in June of 2015 adding six new sample localities.

Transect Map
Above. Sampling locations and field seasons of the Brazilian Atlantic Forest chytridiomycosis study

The Nordeste is a fascinating part of Brazil with a different flora and herpetofauna than we are used to from our time in the southern and southeastern Atlantic Forest states. Here, the Atlantic Forest bioregion forms a mosaic, intermingling with the arid rangelands of the Brazilian Caatinga. It is an area infused with rich Brazilian history replete with lavish stories; from those telling of the folk-hero, frontier bandit Lampião who roamed the dry hinterlands of the region robbing aristocrats to provide charity to poor settlers, to the slave rebellion leader Zumbi dos Palmares of Alagoas who headed Brazil’s largest self-governing colony of escaped African slaves (a quilombo). In addition to boasting the most beautiful beaches in Brazil, the Nordeste is dotted with great historical cities like Salvador, the first colonial capital of Brazil making it both a biologically and culturally captivating part of the country to visit.

Group Photo
Above: The Northeast Bd survey team: Carolina Lambertini, Tommy Jenkinson, Bira Gonçalves, Anyelet Valencia-Aguilar, and Marcos Dubeux

We started our expedition in the northern beach city of Natal, Rio Grande do Norte where we collected amphibians in one of the northernmost remnant patches of Atlantic Forest habitat, the Mata da Estrela Reserve. After two nights in Rio Grande do Norte, and a few dolphin sightings off the Atlantic shore, we headed to the Mata do Buraquinho Reserve in João Pessoa, Paraíba, and then to the Caetés Reserve just north of the major city of Recife, Pernambuco. The Caetés Reserve was a particularly interesting because this reserve contained both intact Atlantic Forest habitat as well as restoration areas dedicated to regenerating the forest after the land was reclaimed from human land-use and disturbance.

Above. View from the Caetés Reserve, Pernambuco

It was in the Caetés Reserve where our team was lucky enough to spot a sloth in the treetops. In addition to the dozens of amphibian species we collected in the reserve, we also got to see some great macrofungi for the mycologists on the team, including a beautiful Cantharellus pictured below.
Above. A few mushrooms of the northern Atlantic Forest. Marasmius cf. amazonicus from Mata da Estrela, and Cantharellus cf. aurantioconspicuus from the Caetés Reserve

After a quick pit-stop at our northern home base (UFAL) in Maceió, Alagoas to unload field specimens and resupply, we continued heading south, passing by Anyelet and Tami’s high elevation, Muraci sample site. We ended up next at Serra de Itabaiana National Park in the hills northwest of Aracaju, Sergipe, where we were joined by Professor Daniel Mesquita from the Federal University of Paraiba. We spent much of our time collecting amphibians near a central river punctuated with waterfalls and isolated pools, which are great for tadpoles. In the afternoons, while processing specimens we were visited by a playful group of marmoset monkeys curious about our work. Finally, we finished by sampling at our final transect point, Sapiranga Forest Reserve in Bahia just north of the state capital, Salvador.
Itabaiana Stream
Above: Itabaiana Stream. Searching for stream tadpoles in the Serra de Itabaiana National Park, Sergipe

Above. Marmosets visiting the field lab in Serra de Itabaiana National Park (left), and sloth spotted in the Caetés Reserve (right).

After three field seasons of intensive sampling, we reflect on the great deal of work the entire team has put into this project, and anticipate what a full analysis of the data will tell us. It is amazing to think that just a few years ago this project was initiated through an NSF/FAPESP Catalyzing New International Collaborations Grant to strengthen research ties between Brazilian and American institutions studying Bd in Brazil. In 2012 the new Bd lineage, Bd-Brazil, had just been discovered along with a hybrid strain between the global pandemic lineage, or Bd-GPL (Schloegel et al. 2012). At the time, however, we did not know the range of Bd-Brazil nor the extent of hybridization between lineages in the Atlantic Forest.

Above. Frogs encountered during the trip to the nordeste.

In fact, little was known about the scale of Bd infection or how it varied across the Atlantic Forest region. At its inception, project leaders from University of Michigan, the State University of Campinas (UNICAMP), Cornell University, University of Maine, and the Federal University of Alagoas envisioned a comprehensive transect survey across the north-south length of the Atlantic Forest. In 2013, our team started the project by sampling the southern portion of the Atlantic Forest closest to São Paulo. Then in 2014, we moved on to sample the middle section of the forest from Espirito Santo to southern Bahia. With this last segment the transect has grown to over 4000 km, spanning 11 Brazilian states, with intensive sampling from almost 20 collection sites.

A survey like this was important for as few reasons. As mentioned before in this blog, the Atlantic Forest is home to a staggering diversity of amphibian species, and their habitat has been increasingly fragmented threatening their existence. Bd in the Atlantic Forest is also important to understand because this is only one of a few global regions which have multiple divergent Bd lineages coexisting within native amphibian communities, and the only hybridizing populations of Bd known in the world. Understanding the infection dynamics of this region will provide insight into how multi-strain interactions shape the epidemiology and evolution of virulence in Bd. A study of these Atlantic Forest lineages could be a valuable opportunity to piece together how these lineages came into contact, and what consequences that contact will have on their ecology. Finally, our team was also very excited to see how well infection patterns across the Atlantic Forest transect matched the latest habitat suitability predictions we recently proposed in James et al. (2015).

The initial look at our data from the full transect is already proving to be very interesting. We are beginning to see a broad trend for infection to drop as amphibian populations reside at latitudes closer to the equator, and as predicted in our habitat suitability model, elevation seems to be playing an influential role in promoting infection especially at warmer latitudes. We are still interested to examine how infection varies across the broad range of amphibian species sampled, and to better understand the population genetics of Bd in the Nordeste region. If the invasive, global pandemic strain of Bd has recently expanded across the northern Atlantic Forest as we hypothesize based off of our population genetic analyses using cultures (Jenkinson et al., in press), we should be able to observe a pattern of lowest genetic diversity in the most recently expanded populations. Much remains to be learned from a full analysis of out Atlantic Forest data. We are now working to finish piecing together the Brazilian Bd story, and hope to have more to share with the amphibian disease community about this region soon.