Tripp, Erin A., James C. Lendemer, and Christy M. McCain. “Habitat quality and disturbance drive lichen species richness in a temperate biodiversity hotspot.” Oecologia 190.2 (2019): 445-457.
What is a lichen?
A lichen is actually two organisms functionating as one in an intimate relationship scientists call, symbiosis. One of these organisms is photosynthesizing plant (usually an alga or cyanobacteria), while the other is a fungus. This intimate relationship can be obligate (one or both members of the relationship are found only together and never alone, i.e. they need eachother to survive), or facultative (they may be found together or survive apart). When together, both partners form specialized structures called thalli (singular- ‘thallus’), in which the fungal partner provides a home for the plant partner. By working together, these two partners help one another survive; the plant, providing the capability to photosynthesize and the fungus providing a structure to protect against harsh environmental conditions. This structure is often found in the form of an epiphyte, geophyte, lithophyte, or cryptophyte (an organism that uses another organism, or physical structure as a substrate on which to grow).
Ecosystem pioneers, but to what extent can they stand disturbance?
Disturbance is a natural process, necessary for all ecosystems to function. Some ecosystems are particularly adapted to deal with certain natural disturbance regimes, such as wildfire, flood, landslides, or harsh seasonal conditions. Within each ecosystem, the different species in that community respond in different ways to each agent of disturbance. However, things begin to change when the natural disturbance regime of an ecosystem changes as a result of human induced interventions.
Lichens have long been described as ruderal organisms, often referred to as pioneer species. These individuals are of extreme importance in ecosystem development, as they are often the first to colonize after disturbance events. Still, there is little we know about how resilient they may be towards these different disturbance regimes. To address this knowledge gap, the team of researchers surveyed lichen biodiversity in the Southern Appalachian mountains, USA, across a series of different ecosystem disturbance and habitat types.
Lichen conservation, why does it matter?
Results from this experiment suggest that lichens are negatively impacted by disturbance and decreased habitat quality. The researchers then chose to posit why this observed pattern was found across the entire diversity of lichens surveyed in the study. The team found that the greatest limitations for lichens to colonize appear to be impacted by the ability for the plant and fungi to find each other in the right place at the right time. Partner and substrate availability are two necessary components for the lichen symbiosis to assemble. This studies findings raises concerns for conservation and management practices, as lichens are an often overlooked component an ecosystems biodiversity, and could be possible red-flag indicators of disturbance in an ecosystem.
In conservation, charismatic species such as certain mammals and birds often warrant greater protection, than other less charismatic species. These under-protected groups of organisms, like fungi and insects, serve numerous, essential roles in an ecosystem that cannot be ignored. Lichens can absorb pollutants in their environment, they also aid in the breakdown of rock, and development of soil, and even provide nitrogen to an ecosystem. Additionally, they serve as food, and shelter for numerous organisms, and have even been used by people for the creation of pharmaceuticals and other products. This study is novel in that it looks at the impacts of ecosystem changes on a diverse and less commonly regarded group of species.
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