In Costa Rica a viable breeding population of a critically endangered harlequin toad species has recently been discovered. The beautifully colored harlequin toad Atelopus varius, was presumed to be extirpated from Costa Rica with only populations of the species remaining in the western part of Panama. Due to intense survey efforts after discovery of the population in 2008 in a private reserve within La Amistad Biosphere Reserve, it has been determined that more than 200 individuals of this species are surviving and that breeding very likely occurs. Because more than 90% of harlequin toad species, endemic to the Americas, are threatened and more than 75% of species is even critically endangered, it is very important that a previously unknown population of a harlequin toad species has been discovered.
Atelopus varius is generally found in humid lowland premontane and lowland montane forests, typically near small streams. In the last 3 generations or more specific in the last 13 years the species has drastically been reduced in numbers, experiencing a population decline of 90% and deeming it critically endangered. In Costa Rica the situation is particularly severe with the number of populations declining in less than 20 years from 100 to 1 and the species was declared extinct from the country in 1996. Parasitic flies, climate change and above all the chytrid fungus have been held responsible for this decline in numbers. In Panama nine populations are surviving, but this harlequin toad doesn’t fare well there either unfortunately. For Costa Rica good news came in 2004 when a small population of three individuals was found in Fila Chonta and at a subsequent survey in 2005 five individuals were identified (Ryan et al. froglog). In november 2008 Gonzalez-Maya and other researchers discovered a different population of Atelopus varius on the foothills of Talamanca mountains within the La Amistad Biosphere Reserve. This location contains primarily regenerating forests with small streams and is managed as a conservation preserve. More intense survey efforts from September 2011 until February 2013 within this area by the same researchers led to 222 sightings of more than 200 individuals (204 to be precise) that can be recognized by their own unique coloring. Although eggs or froglets have not been sighted, one amplexus (mating behavior) and three calling males were observed in the breeding season and the continuous presence of the population over several years strongly suggests that breeding occurs. The population has been monitored intensely for years to ensure that the chytrid fungus has not affected this population;; luckily no signs of infection in this population have been found. Because the harlequin toads reside within a private reserve, land use change doesn’t threaten them either although water quality seems to be suboptimal in the area.
This discovery of a new population of Atelopus varius is not the first ‘rediscovery’ in Costa Rica of a species presumed to be wiped out by the chytrid fungus: in recent years several species have been sighted again including Incilius holdridgei in central Costa Rica and Isthmohyla rivularis in Monteverde. The rediscoveries are probably due to more intense surveys and greater sampling efforts in poorly explored areas but in previously known localities as well. But the question remains how these species stand up from the dead in areas where chytrid fungus has been shown to occur? Gonzalez-Maya et al. propose two alternative hypotheses: the first assumes that populations were isolated before and had not been in contact with the chytrid fungus. Although the main population might have become extinct because of the chytrid fungus, relict populations remained unaffected and could colonize a larger area once the fungus had vanished. Many small creeks (habitat for these species) are isolated and water flow can be a barrier to up-stream dispersal of species. In that way the fungus as well couldn’t reach these populations, presuming they could only survive in their amphibian host. However not much is known about the persistence of the chytrid fungus once its host has deceased. The second hypothesis is that some individuals from an affected population had the ability to survive the infection and developed resistance to it. These individuals could then become the founding fathers of a new population. To be able to choose between these hypotheses more information is needed on the mechanism of fungus spread, population genetics of the host and the fungus and other factors that influence the spread of the disease. Seeing how many amphibians worldwide are threatened by the chytrid fungus this is a very important research theme for amphibian survival.
Now follows the original article from Mongabay.com
A breeding population of a critically endangered harlequin toad thought to be extinct in Costa Rica has been discovered in a tract of highland forest in the Central American country, reports a paper published in Amphibia-Reptilia.
Atelopus varius, an orange-and-black harlequin toad, was once relatively common from central Costa Rica to western Panama. But beginning in the 1980′s the species experienced a rapid population collapse across most of its range likely due to the spread of the deadly chytrid fungus that has been wiping out amphibian populations around the globe.
“In less than 20 years, known populations in Costa Rica declined from 100 to one,” notes the paper. By 1996, the species was considered extinct in the country.
But in 2004 there was a brief moment of hope when a population was discovered near Quepos, in southwestern Costa Rica. Subsequent surveys however failed to turn up any frogs.
Sustained good news for the frog finally came when researchers stumbled upon a significant population on a private reserve within La Amistad Biosphere Reserve, near the Panamanian border. The new paper describes the population, which numbers over 200 individuals, and documents breeding behavior.
The authors, led by José F. González-Maya of the Sierra to Sea Institute & ProCAT International in Costa Rica and the Universidad Nacional Autónoma de México (UNAM), say the find offers hope for other thought-to-be-extinct species in Costa Rica.
“Our findings fit into the emerging theory that species which have been presumed extinct are beginning to be re-discovered in Costa Rica and elsewhere. After severe declines, often to where zero individuals are detected in the wild, several frog species have been re-discovered in areas of Costa Rica with previous records of chytrid, as well as in areas not sampled previously,” write the authors.
“These findings follow a pattern similar to our finding in that species considered extinct or near-extinct, with recorded massive declines due to chytrid have been rediscovered at previously known locations. Recent analyses suggest that certain areas of Costa Rica have high probabilities of re-discovering populations, and most have not been sampled since 2000.”
Atelopus varius may therefore be just one of many “Lazarus species” whose epitaphs were written a bit too soon.