Germination behavior of the extremely rare Hladnikia pastinacifolia Rchb. (Apiaceae) – a Pleistocene in situ survivor

Abstract

The present-day diversity of European flora in temperate mountain ranges was mainly formed by the negative effects of Pleistocene glaciation, which caused extinctions, restricted survival in situ, and subsequent re-colonization. Only rarely can we find species that have retained the molecular information of in situ survival. One such example is the extremely rare H. pastinacifolia Rchb., a monotypic genus and a narrow endemic of a mountain plateau south-east of the Julian Alps (Slovenia). We investigated the germination behavior and dispersal indications, which are often closely related to rarity and persistence and thus valuable for species conservation. Additionally, results about H. pastinacifolia help us to understand better what kind of species survived glaciations in Europe in situ. Our results show that these seeds have an underdeveloped embryo and require an ecologically relevant moist chilling period of about 100 days. The temperature sequence of the colder period that H. pastinacifolia seeds received in nature was 20/15 °C (52 days), 10/5 °C (40 days), 5/0 °C (65 days), 10/0 °C (45 days), 15/5 °C (21 days). The germination rate was high, significantly increased by scarification, and therefore prevented long-term seed bank establishment. We found cryptic seed differences expressed by two types of dormancy, each related to the order of the umbel: simple and complex morphophysiological dormancy for the lateral and the main umbel, respectively. Seed dispersal was very much influenced by precipitation in autumn. The germination and dispersal characteristics could explain the rarity and at the same time the persistence of H. pastinacifolia.