Background - Many plants use others for structural support. These are typically assigned to different categories such as epiphyte, hemiepiphyte, climber, or mistletoe, which is based on sites of germination, growth and nutritional independence from the host. Unfortunately, such a seemingly unambiguous categorization is not consistently applied in individual studies, and intraspecific biological variation, which actually precludes a neat categorization in many cases, is typically ignored. This has led to a rather confusing situation, in which it is even doubtful whether one form, “secondary hemiepiphytes”, exists at all. I present several analyses of the literature and results from field studies that highlight the problem.
Objective - There are many ways to be a structurally dependent plant. The current scheme of grouping and the use of terminology does not appropriately reflect biological reality and needs to be revised.
Methods - As a first step we can analyse what information is already available, e.g. by compiling life form information from the literature (floras, annotated species lists, vouchers). Unfortunately, data are not necessarily reliable and different sources often provide inconsistent information. Thus, there is no way around field studies that document intra- and interspecific variation and in the best of cases, understand the underlying mechanisms.
Results – 1) Terminological chaos: I present data documenting that many researchers have developed an idiosyncratic terminology, which obviously impedes unambiguous communication. 2) Biological variation: I present data from both literature studies and field studies that document that the neat assignment of plant species to either the group of “epiphytes”, “climbers”, “lithophytes” or “terrestrials” is frequently not justified. The magnitude of the problem is unclear because there are few reliable data.
Conclusions - The way we categorize biological variation shapes our perception of reality. Emphasizing clear-cut categories (= discontinuity) instead of gradients (transitions and continuity) may easily lead to erroneous conclusions and misunderstandings of biological processes. For example, many studies in the fields of ecology, evolution and physiology compare “epiphytes” with “terrestrials” without acknowledging intraspecific variation in this trait. Thus, many of the patterns we identified are possibly incorrect. There is clear need for pertinent studies and for the creation of awareness in the research community – we need an unambiguous use of terminology. The goal is clear: we want to understand biological variation and must avoid terminological chaos.
Epiphytes Biodiversity Hemiepiphytes Climbers Mistletoes facultative_epiphytes nomadic_vines Variation