# The ecology of lichenicolous lichens: a case-study in Italy

## TL;DR

This study explores the ecology of lichenicolous lichens in Italy, finding they thrive in dry, well-lit habitats and may not be true parasites.

## Contribution

The study provides new ecological insights into lichenicolous lichens, suggesting they may not be parasites but rather ecologically adaptive.

## Key findings

- Lichenicolous lichens show higher incidence of coccoid algae, crustose growth, and sexual reproduction.
- They occupy a distinct ecological niche in dry, well-lit, rocky habitats across all altitudes.
- The findings suggest lichenicolous lichens may acquire adapted photobionts from hosts rather than parasitizing them.

## Abstract

This paper, with Italy as a case-study, provides a general overview on the ecology of lichenicolous lichens, i.e. those which start their life-cycle on the thallus of other lichens. It aims at testing whether some ecological factors do exert a positive selective pressure on the lichenicolous lifestyle. The incidence of some biological traits (photobionts, growth-forms and reproductive strategies) in lichenicolous and non-lichenicolous lichens was compared, on a set of 3005 infrageneric taxa potentially occurring in Italy, 189 of which are lichenicolous. Lichenicolous lichens have a much higher incidence of coccoid (non-trentepohlioid) green algae, crustose growth-forms and sexual reproduction. A matrix of the 2762 species with phycobionts and some main ecological descriptors was subjected to ordination. Lichenicolous lichens occupy a well-defined portion of the ecological space, tending to grow on rocks in dry, well-lit habitats where a germinating spore is likely to have a short life-span, at all altitudes. This corroborates the hypothesis that at least some of them are not true “parasites”, as they are often called, but gather the photobionts - which have already adapted to local ecological conditions - from their hosts, eventually developing an independent thallus.