a) Harlequin toad: The rediscovery of the nearly extinct harlequin toad in Costa Rica raises many ecological questions. What environmental factors limit their geographic distribution? What factors (i.e., food, pathogens) affect population size? In your response, be sure to include information from the reading to support your answer.
Solution
Anthropogenic climate changes acted as the major environmental factor involved and acted as a major cause for extinction of harlequin toads. The changing climatic conditions involving sea-surface and air temperatures acted as another reason for mass extinction of toads. The chytrid fungus acted as the most primitive cause for extinction of toads as these fungi is capable of degrading chitin and keratin and act as a pathogen for toads by infesting them. These fungal species growth gets enhanced when the temperature of the earth rises that tends to enhance cloud cover on tropical mountains, ultimately ending up in cooler day and warmer night, most favorable situation for chytrid fungus to thrive. Many species of chytrid fungus are found to be involved in manifesting infection in toads thereby paving way for its extinction. Global warming act as a clear threat to the local ecosystem prevailing in region like Costa Rica. Changing climate modifies the temperature pattern, mist and rainfall, causing cloudbanks to form at increasing elevations like Costa Rica and compressing the possible range for cloud forests thereby leading to extinction of toads. Global warming appears to hold direct as well as indirect effect on extinction of toad population. Global warming can either act directly by narrowing the cloud forests or can force the amphibian population to arrive at a particular habitat and live together thereby increasing their susceptibility to gain pathogenic infection. These conglomerations of toad population also s found to be under stress that could have acted as another reason for extinction. Increased rain and higher temperatures are considered as the major cause for extinction of harlequin toads (Global greenhouse warming.com, n.d.).