Ecology of a rare and endemic Plantago species

摘要

Biodiversity loss and the acceleration on the natural extinction rate are driven by anthropogenic factors. Governments are obliged to elaborate checklists of conservation status, where the knowledge about species' ecology is implied. That is to say, there should be information about the species' relation with the environment and with co-occurring species, for predicting suited conservation measures. The Critically Endangered plant Plantago almogravensis Franco has been included in the Habitats Directive, in Portugal. It is limited to one known population (within an extent of occurrence of less than 3 ha) in the Southwest coast. Its taxonomic position and endemicity have been challenged, though based on incomplete taxonomic criteria and disregard for its particular ecological context. So far, the conservation measures have been insufficient and it has a Bad conservation status (Habitats Directive 2013). The aims of this work were to study the ecology of P. almogravensis, contributing to the theoretical study of rarity and to envisage suited guidelines to improve its conservation status. Also it intends to better understand its taxonomic position among similar taxa. Several morphologic and ecological differences were observed between P. almogravensis and its sister species (Chapters 2 and 7) though not at the molecular level (Chapter 5). The description of P. almogravensis basic morphology and edaphic habitat (Chapter 2) was accompanied by the observation of limitations in pollination, production of seeds and dispersion. The ecological niche was characterized (Chapter 3), establishing the importance of competition and environmental stress (namely Al-toxicity) for the width of the realized niche. The enhanced Al-tolerance (Al-hyperaccumulation) and its refuge in geochemical islands were confirmed (Chapter 4). The hyperaccumulation of aluminium is likely to have a phylogenetic origin (Chapter 5), though the Plantago genus hyper-accumulates also other metals. The ecological niche was associated with specific soil microbial functional groups (Chapter 6), which influence germination and mostly plant survival (Chapter 7). For the life cycle of Plantago spp., light and aluminium impact plant development, in spite of the high aluminium plant resilience (Chapter 7). Limitations in germination and juvenile survival during establishment are critical. Overall, a decrease in the population is envisaged from field population dynamics (Chapter 7). Three conservation priorities were identified (Chapter 8): (i) reduce fragmentation; (ii) identify new suitable habitats and colonize; (iii) assisted reproduction. Conservation efforts could be primarily directed to continue the assisted reintroduction and monitoring, on the Southwest coast, creating new sub-populations, independently of maintaining or improving the ecological conditions of the current population. This work shows that ecological and species evolutionary uniqueness should be incorporated in conservation measures.