Plantago trinitatis Rahn ( Plantaginaceae ) : New sites of occurrence and altitudinal variation at Trindade Island , Brazil

Plantago trinitatis, endemic plant of Trindade Island, a small oceanic island (9.28 km2) apart about 1,140 km from the coast of the city of Vitória (Espírito Santo, southeastern Brazil), until now had only been located on the island at altitudes greater than 500 meters, in a dry environment and rocky soil. In April 2013, we observed several individuals of the species at altitudes varying from 80 to 240 meters, along a small watercourse in the northeast portion of the island. This record, in addition to confirming the occurrence of the species at lower altitudes than 500 meters, also confirms the recovery of the species, which, until 1998, was considered extinct.

The genus Plantago Linnaeus is cosmopolitan, with over 250 species concentrated in temperate or tropical regions.In general, the species of this genus are presented as herbs or, less commonly, as subshrubs and can be perennial or annual.Some species have a wide distribution, others with a more restricted distribution are habitat specialists; many of the latter occur only in small oceanic islands (Rahn, 1996;Rønsted et al., 2002;Dunbar-Co et al., 2008;Tay et al., 2010;Hefler et al., 2011;Meudt, 2012).
The species P. trinitatis is endemic to the Trindade Island (Hassemer et al., 2016), a small oceanic island (9.28 km 2 ) apart about 1,140 km from the coast of the city of Vitória (Espírito Santo, southeastern Brazil, Figure 1).Its onshore portion reaches 620 meters above sea level and the ocean depths around the island reach 5,500 m (Alves, 1998;Castro, 2009).Since 1984, the administration of the island is under the jurisdiction of the Brazilian Navy (1 st Naval District) that maintains an Oceanographic Station with a weather station in the area (Brasil, 1984;Alves, 1998).Access to the island is restricted, and scientific researches in the region are supported by PROTRINDADE program, linked to the Secretariat of the Inter-ministerial Commission for Sea Resources (Mohr et al., 2009).
The first sample of P. trinitatis was collected by Johann Becker on December 13, 1965, who found only "a dozen individuals" on the rocky slopes of the locality known as "Fazenda".The species was considered extinct until 1998, when one relictual population was rediscovered in the "Pico Trindade" at 590 meters of altitude (Alves, 1998;Alves et al., 2011;Clemente et al., 2011).All records of P. trinitatis, until now, occurred at elevations ≥ 500 m, in a dry environment and rocky soil (Alves, 1998;Alves et al., 2011;Hassemer, 2013).
On April 11, 2013 we recorded the first specimens of P. trinitatis in altitude less than 500 m along a small watercourse, in the northeastern portion of the island (Figure 3), this being the first record for the species less than 500 meters of altitude.The specimens registered on this occasion were located between 80 and 240 meters above sea level (Figure 1).
Both records (03 and 11 April 2013) are extremely important as they demonstrate the recovery of the species, which after being considered extinct was rediscovered in 1998 and currently is expanding, occupying environments where previously there had been registered (below 500 m asl).The eradication of feral goats on the Trindade Island, completed in 2004 (Alves et al., 2011) was crucial to the recovery of the species, which in nine years managed to establish new populations on the island.Despite the recovery of the P. trinitatis populations on Trindade Island, according to Hassemer et al. (2016) this species should be classified as "critically endangered" by the IUCN criteria.However the species is not yet in the Red List of the Flora of Brazil (MMA, 2008).Thus, we recommend more studies of this endemic species, which had its population reduced in the period they suffered pressure from feral goats, almost reaching extinction.The current population of the species must be accompanied and monitored, because a new threat may come to harm its expansion, as is the case of invasive plants such as Guilandina bonduc L. (Fabaceae), which is already colonizing the Trindade Island (Carvalho-Silva et al., 2013).

Figure 1 .
Figure 1.(A) Location of the Trindade Island (island size unscaled) and (B) records of Plantago trinitatis in the island.

Figure 2 .
Figure 2. Individuals of Plantago trinitatis registered near the area known as "Fazendinha" (altitude ≥ 500 m) in a dry environment and rocky soil.

Figure 3 .
Figure 3. Individuals of Plantago trinitatis registered in the northeast portion of the Trindade Island (altitude <500 m) along a small watercourse.