Assessment Notes

Justification

Mycosphaerella coussapoae is a host specific fungus found in leaf spots on Coussapoa floccosa, a threatened plant species. The specificity presented reflects its dependence on conservation of its rare host. It has an extent of occurrence (EOO) of 4,278 km² and its area of occupancy (AOO) is restricted to 24 km² distributed across five threat-based locations. It is endemic to primary fragments of forests in the Atlantic Forest of Brazil. The population of M. coussapoae is exposed to threats from fire occurrence, the presence of agriculture and the exploitation of other natural resources around its range. Therefore, the loss of habitat quality is a predominant factor to be considered for the conservation of this species. Its threat status is assessed as Endangered under criteria B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v).

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Geographic range

The fungus Mycosphaerella coussapoae, as a host specific species, has always been found associated with the leaves of the plant Coussapoa floccosa (Rocha et al. 2010), and never been found associated with other plant species, including other checked members of the Urticaceae (e.g. Coussapoa microcarpa, Pourouma guianensis and Cecropia sp.). Therefore, it is possible to infer that its geographic distribution is related to the geographic distribution of its rare host. M. cousapoae can be found in five sites 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 4,278 km² and its area of occupancy (AOO) is restricted to 24 km² distributed across five locations.

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Population and Trends

Although it is not possible to estimate the population size, it is notable that the population is fragmented due to its geographic disjunct distribution, mainly due to the presence of valleys and mountains, frequently covered by land used for agricultural practices or cities. Additionally, the number of mature individuals in subpopulations fluctuate as hosts shed leaves annually. The population trend is decreasing due to a 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: decreasing

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Habitat and Ecology

Mycosphaerella coussapoae is a host specific species occurs in lesions found on living leaves of Coussapoa floccosa, a threatened plant species (Fernandes and 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 occur in the site 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 host-specificity. 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, creating a natural check on the species. This indicates that its life cycle involves annual fluctuations 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.

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Threats

The threats leading Mycosphaerella coussapoae's 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 has become 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 and Moraes (2019) and the references therein.

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Conservation Actions

It is important to assign all areas where the host can be found as permanent protection areas, and there should be expansion of vegetated areas with native forests, including the formation of corridors between forest fragments to facilitate the crossing of possible seed disseminators of the host. Creation of a host recovery programme through the production of seedlings and distribution to reforestation areas will also aid this species, while awareness should be raised among the population that lives surrounding areas where the fungus is found to reduce the risk of fires.

It is necessary to have a better understanding about the specificity of Mycosphaerella coussapoae in relation to its host. This 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.

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Use and Trade

There are no known uses.

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Source and Citation

Branco Rocha, F., Komura, D., Costa-Rezende, D.H. & Barreto, R. 2024. Mycosphaerella coussapoae. The IUCN Red List of Threatened Species 2024: e.T74848109A74848112. .Accessed on 31 October 2024

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• Country occurrence