In situ or ex situ seed conservation: which is the more effective way to maintain seed longevity of an endangered cactus?

Abstract

With restricted populations and a small number of individuals, Discocactus bahiensisBritton & Rose (Cactaceae) is an endangered species in Brazil and its capacity for the formation of seed banks in the soil and the maintenance of seed viability remains unknown. Thus, the aim of the present study was to determine the most efficient way to maintain viability during storage of seeds of D. bahiensis. Seeds were stored in paper bags and either kept in a cold chamber (7 AE 2 C) in the dark (ex situ conservation) or buried in the soil to a depth of 5 cm in an area of natural occurrence of the species (in situ conservation). Germinability of the seed banks was evaluated monthly for 20 months. During the first 10 months of storage, germinability of the seeds conserved in situ and ex situ was similar to that of recently collected seeds. After this period, a 70% reduction in germinability was found for the seeds maintained in situ and there was nearly complete loss of viability after 12 months of storage in the field (germinability < 10% in the last 8 months of the experiment), indicating the ability to form persistent soil seed banks. In contrast, the seeds stored in the cold chamber maintained greater than 70% germinability throughout the entire analysis period, demonstrating that ex situ conservation is the most efficient way to maintain the viability of the seeds of this endangered species.

Seed storage of Brazilian cacti species in different threat categories

“…The results we obtained in this study showed that storage techniques at low temperatures, especially in a cold chamber and freezer, were efficient in maintaining seed viability for all the studied taxa during the evaluation time (13 months). However, these techniques could perhaps preserve the seeds of these species for a longer time (see, for example, the results of Nascimento et al 2015;Nascimento & Meiado 2017). We hope that our results will encourage the formation of seed banks and therefore bolster seed conservation, especially in developing countries, where most of the endangered plant species occur.…”

“…However, these techniques could perhaps preserve the seeds of these species for a longer time (see, for example, the results of Nascimento et al . ; Nascimento & Meiado ). We hope that our results will encourage the formation of seed banks and therefore bolster seed conservation, especially in developing countries, where most of the endangered plant species occur.…”

“…; Meiado et al . ; Nascimento & Meiado ), an interval that is standard to species with orthodox seeds (Roberts ; Probert et al . ; Walters ; Visscher et al .…”

“…After dehydration, funicular pulp was manually removed and seeds were washed in distilled water, dried at room temperature and stored in paper bags for less than 2 months until the start of the experiments. According to the literature, the moisture content of the seeds of the taxa we studied in this work is 9-12% (Rojas-Aréchiga & Vázquez-Yanes 2000; Veiga- Barbosa et al 2010;Marchi et al 2013;Nascimento et al 2015;Meiado et al 2016;Nascimento & Meiado 2017), an interval that is standard to species with orthodox seeds (Roberts 1973;Probert et al 2009;Walters 2015;Visscher et al 2016).…”

“…The main purpose of a seed bank is to maintain the viability of seeds for a long time, which as an ex situ conservation approach can be applied to protect biodiversity by allowing, for example: the reintroduction of endangered/extinct species into their native habitats; the cultivation of these species of interest in living collections such as botanical gardens; and the use of the preserved seeds for environment restoration (Walsh et al 2003;Maunder & Byers 2005;Assis et al 2011;Nascimento et al 2015;Nascimento & Meiado 2017).…”