Algal communities in phytotelmata: A comparison of native Collospermum and exotic bromeliads (Monocotyledonae) in New Zealand

Abstract

Plants that grow epiphytically are often adapted to hold water in a central cup or leaf axils to maintain hydration given that they cannot access soil water. These bodies of water, called phytotelmata, are temporary miniature aquatic ecosystems. This water frequently contains a variety of microorganisms. The New Zealand native Collospermum hastatum is known to hold water within the leaf axils, however an assessment of algal communities within this habitat has never been undertaken. To remedy this lack of knowledge, water samples were obtained from the leaf axils of Collospermum hastatum, with exotic bromeliads for comparison. Freycinetia banksii and Astelia solandri were also investigated, but excluded from further analysis due to inadequate supply of axil water. Samples were investigated using a light microscope for algae, in particular desmids and diatoms, and other biological material. Urban bromeliads investigated had a wide range of organisms within the phytotelmata, including four genera of diatoms. No desmids were identified. Forest-sourced bromeliad and Collospermum water held a comparatively less diverse range of biota, with a complete lack of algal presence. We propose two possible explanations for this, low background levels of algae for dispersal within native forest environments, and the phytotelmic conditions being unsuitable for algal growth