Using population characteristics to evaluate the conservation status of endangered grassland species - The case of Herbertia zebrina in southern Brazil

- Abundance and reproduction of the endemic Herbertia zebrina are favourable.
- The species is not in an extinction vortex but endangered due to land-use change.
- The Red List classification as 'critically endangered' should be maintained.

Many plant species listed as endangered by IUCN do not have information on population characteristics and reproductive traits, although such data are needed for conservation classification. This paper revisits the conservation status of a 'critically endangered' species in fragmented grasslands of southern Brazil. We present the case of Herbertia zebrina (Iridaceae), a geophyte first described in grasslands on granitic outcrops in 2010. We identified 18 populations within an estimated range of about 5000 km2. Data on population size, plant size, fruit production and germination were recorded for three representative populations with repeated sampling of labelled flowering plants over a period of two years. Population size was 1869-14,555 flowering plants (2.2-3.5 plants m−2) with considerable turnover between years. Among populations, 11-61% new flowering individuals emerged in the second year, while 27-46% of the first-year plants were not observed in the following year. The plants emerged in early spring in both years and flowered over a period of four months. The number of fruits was positively correlated with plant size and vegetation height, while germination was about 86%. Thus, the number of populations, area of occupancy and plant reproduction indicate a more favourable conservation status than previously assumed. Nonetheless, due to population fragmentation and the rapid loss of natural ecosystems in the region because of land-use change, the overall classification of the species as 'critically endangered' should be maintained. Future research has to focus on implications of fragmentation on genetic variation among populations.