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.

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.

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