A gleam of hope for the critically endangered Isoëtes malinverniana: Use of small‐scale translocations to guide conservation planning

Abstract

Results of the first documented reintroduction of the endangered endemic quillwort Isoëtes malinverniana are presented 1 year after transplanting. This represents the most complete report of a quillwort translocation globally. A new population of I. malinverniana was established in a protected area in Lombardy (northern Italy) after several years of investigation of the ecology, biology and genetics of this species. The selected site was restored before the trial release in March 2016 of 20 individuals of the target species. Although modelling for the selection of suitable release sites for the target species indicated that the selected site was not suitable for the species, I. malinverniana exhibited a survival of 60% 1 year after reintroduction. This trial indicates that with very rare species, experimental trialling of a few individuals can test the feasibility of translocation at a larger scale. Although the model was constructed using a wide variety of ecological and phenological parameters, it was unreliable because of intrinsically low statistical power, which is a limitation of modelling associated with very rare species. Although mature spores were dispersed in autumn 2016, sporelings have not yet been observed. Ultimately, reintroduction of I. malinverniana will rely on the evidence of self‐recruitment; however, this translocation effort promoted understanding of ecological tolerance and facilitated focused conservation management. For instance, a protocol for in vitro reproduction of the species was successfully developed, resulting in long‐term survival of ex situ collections that exist in two botanical gardens in Pavia and Turin. Considering that many isoëtid species are threatened worldwide, the techniques applied here may have broad applicability to other endangered species.

In Vitro Propagation of Isoëtes sabatina (Isoetaceae): A Key Conservation Challenge for a Critically Endangered Quillwort

“…Several authors accounted for the developmental stage of the megaspores as a critical factor affecting germination in I. coreana [ 14 ], I. malinverniana [ 10 ] and, especially, I. cangae with no germination of immature megaspores [ 18 ]. However, germination results for I. sabatina are only partially in accordance with these results, as no germination was observed exclusively in cultures of spores from beached plants, collected more than one month before maturity, being too small and underdeveloped to germinate.…”

“…Based on this, the main conservation challenge for I. sabatina is to plan and carry out an in situ conservation program, including habitat restoration and reintroduction or reinforcement activities, as recently reported for I. malinverniana [ 10 ], to increase the size of the depleted wild population using innovative solutions able to reduce the negative effects induced by future climatic uncertainty and water level variations.…”

“…1.5 mL per plate) was added monthly to allow fertilization in water-agar cultures. The experiments were conducted under the same culture conditions inside a cooled incubator (Panasonic MIR-154-PE, Osaka, Japan) at a constant temperature (20 °C) and 12/12 h photoperiod according to [ 10 ]. Different temperatures were not tested in this study because of the reduced spore availability and the urgent need to produce plants to reinforce the remnant small population.…”

“…The family Isoëteaceae consists of a single genus, Isoëtes L., which currently includes about 250 species [ 1 , 2 ] occurring in lakes, wetlands, and terrestrial habitats all over the world, from the tropics to the subarctic [ 1 , 3 ]. Some species are widely distributed [ 4 , 5 ], while several others remain restricted to a few sites [ 6 , 7 , 8 , 9 , 10 ]. This genus also shows high local diversification and endemism rate [ 11 ].…”

“…Quillworts and their fragile habitats are known to be highly threatened worldwide and they can be key indicator species of aquatic ecosystem health [ 10 , 12 , 13 ]. An overall decline of Isoëtes populations has been reported for a large part of the extant species that are facing serious risks of extinction [ 6 , 8 , 10 , 14 ]. In particular, 50% of European Isoëtes have been assessed as threatened [ 13 ], and five out of the ten species occurring in Italy are endangered or critically endangered [ 15 , 16 ].…”