Mycosphaerella coussapoae F.B. Rocha & R.W. Barreto is a phytopathogenic fungus found in leaf spots on Coussapoa floccosa Akkermans & C.C. Berg, an endengered plant species. The specificity presented between its host reflects the dependence on conservation of its rare host individuals. The host’s extent of occurrence (EOO) is 4,277 km2 and its area of occupancy (AOO) is restricted to 24 km2 distributed across five locations. It is endemic to primary fragments of forests in the Atlantic Forest of Brazil. The population of M. coussapoae is exposed to negative influences fire occurrence, the presence of agriculture and the exploitation of other natural resources around the area of occupation of this fungus. Therefore, the loss of habitat quality is a predominant factor to be considered for the conservation of this species. It is necessary to recognize its threat status in the Endangered category under the B1+B2ab(i, ii, iii) criterion.
Mycosphaerella coussapoae F.B. Rocha & R.W. Barreto, Mycologia 102(6): 1243 (2010).
Mycosphaerella coussapoae inhabits a rare and threatened host (Coussapoa floccosa) present only in primary forests of Brazilian Atlantic Forest.
The fungus Mycosphaerella coussapoae, typically phytopathogenic, has always been found associated with the leaves of the plant Coussapoa floccosa (Rocha et al. 2010), but has never been found associated with other plant species, including other checked members of the Urticaceae (Coussapoa microcarpa, Pourouma guianensis and Cecropia sp.), so we can infer that its geographic distribution is related to the geographic distribution of its rare host. Therefore, M. cousapoae can be found in five locations in primary forest fragments of the Atlantic Forest in Minas Gerais state and Espírito Santo state, Brazil. To understand the extent of occurrence (EOO) and area of occupancy (AOO) of this species, the locations mentioned in reports of the occurrence of its host were considered (Bachman et al. 2011). It was found that its extent of occurrence (EOO) is 4,277 km2 and its area of occupancy (AOO) is restricted to 24 km2 distributed across five locations.
Extent of occurrence (EOO) by GeoCAT = 4,277 km2
Area of occupancy (AOO) by GeoCAT = 24 km2
N° of locations= 5
Although it is not possible to estimate population size, it is notable that populations are fragmented due to geographic separation, mainly due to the presence of valleys and mountains, frequently covered by land used in agricultural practices or cities. Additionally, the number of mature individuals in subpopulations fluctuate as hosts shed leaves annually. Apparently, the population trend is stagnant, but at risk of decline due to a projected continuing decline of habitat quality since most locations are in small fragments of semi-deciduous forest in the Atlantic Forest located on private properties surrounded by agricultural production fields. The possibility of fires can also lead to a sudden decline in the population due to loss of substrate.
Population Trend: Uncertain
Mycosphaerella coussapoae occurs in lesions found on living leaves of Coussapoa floccosa, an Endangered plant species (Fernandes & Moraes 2019). This fungus belongs to the Mycosphaerellaceae family, which are typically phytopathogens that cause located symptoms on the leaves and are not associated with other tissues of their hosts. Several species in this family have some level of specificity with their hosts (Crous, 2009), and as M. coussapoae has never been reported on another host, we can assume that this fungus presents host specificity. To further clarify its specificity, searches were carried out on plant species from the Urticaceae (Coussapoa microcarpa, Pourouma guianensis and Cecropia sp.), which coexist with M. coussapoe in the location where there is a greater concentration of its host (Gastauer el al. 2015). During these searches, M. coussapoe was not found causing symptoms in other plant species, corroborating with the hypothesis of coextinction with the threatened host. Furthermore, M. coussapoae may fluctuate annually in its population, as its host is deciduous, and the lesions caused by the fungus do not appear on young leaves or on other plant tissues. This indicates that its life cycle involves annual fluctuation between active mature individuals in the canopy and dormant spores in the leaf litter, exposing M. coussapoae to the risk of extinction if burning occurs within the forest during the dry season, when its only substrate is on the ground and capable of serving as fuel for fire.
The threats leading M. coussapoae host to extinction are the same that could cause the co-extinction of the fungus due to its species-specific relationship. Along with this, the loss of habitat quality is also worrying since this species was only found in fragments of primary forest in the Brazilian Atlantic Forest (Rezende et al. 2018). It has already been demonstrated that habitat fragmentation can lead to the loss of 13% to 75% of biodiversity (Haddad et al. 2015).
The occurrence of fires becomes a major threat, since during one phase of its cycle, M. coussapoae is found in the dry leaf litter until it finds the leaves of the next annual shoot, since its host is a deciduous plant. Furthermore, its occurrence in small fragments of forest surrounded by agricultural fields predisposes its population to suffer negative influences caused by pesticide drift. Another important threat is related to climate change, which can also interfere with the life cycle of phytopathogens (Burdon and Zhan, 2020). Additional information about plausible threats to M. coussapoae are in mentioned in Fernandez & Moraes (2019) and the references therein.
Recognize all areas where the host can be found as a permanent protection area. Expansion of vegetated areas by native forests, including the formation of corridors between forest fragments to facilitate the crossing of possible seed disseminators of the M. coussapoae host. Creation of a host recovery program through the production of seedlings and distribution to reforestation areas. Combat fires by raising awareness among the population that lives surrounding areas where the fungus is found.
It is necessary to have a better understanding about the specificity of M. coussapoae in relation to its host. It should be carried out studies that better identify the geographic distribution of its host and also the population trends of the fungus. After that, it will be possible to outline strategies for managing the habitat where M. coussapoae is found and expand the distribution of this fungus in natural ecosystems.
No known uses.