A tree covered with leafy foliose lichens and shrubby fruticose lichens
Letharia vulpina, wolf lichen, grows like a multiple-branched tuft or leafless mini-shrub, so it has a fruticose growth form.
Collema nigrescens is gelatinous, without internal structure for its parts.
Lichens considered to be example of mutualistic symbiosis
Mycobiont
Some lichens, like the foliose Lobaria pulmonaria, are sensitive to air pollution.
Lichen
A lichen is a hybrid colony of algae or cyanobacteria living symbiotically among filaments of multiple fungus species, along with bacteria embedded in the cortex, in a mutualistic relationship.
A Crowded Miniature Ecosystem in Place of an Individual
Long understood as a simple binary partnership, a lichen is actually a composite micro-ecosystem that first introduced the concept of symbiosis to biological science. Many macrolichens incorporate an essential third partner: basidiomycete yeasts from the order Cyphobasidiales. These embedded yeasts help synthesize the protective cortex and maintain the structural shape of the thallus, demonstrating that lichens function as complex holobionts rather than single discrete organisms.
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Blastophaga psenes female
Female (left, with long ovipositor) and male Blastophaga psenes
Pleistodontes sp. female
![Ceratosolen species are pollinators of the Sycomorus, Sycocarpus and Neomorphe sections of Ficus.[12]](https://nwjvzop1xgplmzvt.public.blob.vercel-storage.com/wikifeed/fig-wasp/3-05b98b6363.webp)
Ceratosolen species are pollinators of the Sycomorus, Sycocarpus and Neomorphe sections of Ficus.[12]
Non-pollinating parasitoid wasps Apocrypta ovipositing on Ficus sur in South Africa
Fig wasp
Fig wasps are wasps of the superfamily Chalcidoidea that spend their larval stage inside fig syconia, with some acting as pollinators and others simply feeding off the plant.
Aristotle's Spontaneous Psenes
In his History of Animals, Aristotle documented that wild fig fruits held tiny insects called psenes that prevented cultivated figs from dropping. He mistakenly concluded that these creatures arose through spontaneous generation rather than recognizing sexual reproduction in the plant. His ancient observations captured the ecological bond long before modern science understood pollination biology.
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Mixotricha paradoxa color and
Mixotricha paradoxa
Mixotricha paradoxa is a species of protozoan that lives inside the gut of the Australian termite species Mastotermes darwiniensis.
The 1933 Classification Paradox
Australian biologist J.L. Sutherland first described the organism in 1933, bestowing a name that translates to the paradoxical being with mixed-up hairs. Sutherland observed both cilia and flagella projecting from the single cell, an anatomical combination previously thought impossible for protists. What appeared to be a single anomalous eukaryote was later revealed to be an intricate multispecies partnership.
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Buchnera aphidicola in a host cell
Buchnera aphidicola
Buchnera aphidicola is a bacterium and the primary endosymbiont of aphids, being the only species in the genus Buchnera.
Shedding Outer Defenses for Host Life
Buchnera evolved from a free-living ancestor related to Enterobacterales, yet it discarded essential bacterial structural components. Despite maintaining a 3 μm diameter and a Gram-negative cell wall, it lacks the genes needed to assemble lipopolysaccharides in its outer membrane. Long-term vertical transmission also eliminated the machinery for synthesizing complex carbohydrates and fatty acids. This continuous reductive evolution transformed a typical bacterium into a specialized, stripped-down cellular partner.
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Yellow-brown zooxanthellae
Cross section of the mantle tissue of a giant clam showing the symbiotic protozoa
A ciliate with green zoochlorellae living inside it endosymbiotically
Diagram of radiolarian containing zooxanthellae (z)
FFS Table bottom
Zooxanthellae
Zooxanthellae is a colloquial term for single-celled photosynthetic organisms that live in symbiosis with diverse marine invertebrates, including corals, jellyfish, demosponges, and nudibranchs.
Subverting Lysosomal Digestion into Evolutionary Coexistence
The mutualism between zooxanthellae and marine hosts traces back to a cellular subversion of host defenses. When early dinoflagellate cells were engulfed by host lysosomes, they avoided degradation by providing a steady supply of carbon compounds instead. This metabolic contribution allowed the structures to coexist within host cells rather than being broken down. Over evolutionary time, this avoided digestion established one of the ocean's most fundamental endosymbiotic partnerships.
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Pseudomyrmex ferrugineus casent0005785 profile 1
"Horns" of Acacia cornigera
Pseudomyrmex ferruginea Ryan Somma-cropped
An opened A. cornigera thorn containing an adult and immature P. ferruginea
Pseudomyrmex ferruginea
The acacia ant is an arboreal, wasp-like ant species best known for living in symbiosis with the bullhorn acacia throughout Central America.
The Botanical Battle Cry of Trans-2-Hexenal
When an herbivore damages bullhorn acacia foliage, the tree releases the volatile organic compound trans-2-hexenal. Ants immediately recognize this chemical signal and aggressively swarm the site of injury. They attack intruders of all sizes, killing insects like crickets and delivering painful stings to the sensitive mouths and tongues of browsing mammals such as goats.
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Atta colombica queen
Until the first generation of the new colony is born and matures, the queen will have to cultivate the fungus herself. When a queen is establishing a new colony, she brings a fungal cultivar from her previous colony and lays her eggs around it. Once the eggs mature, she retires from cultivating and continues to lay as many as 20,000 eggs to establish the rest of the colony.[5]
Atta, "higher attine" ants and their cultivar fungus
Ant–fungus mutualism
Ant–fungus mutualism is a symbiosis between certain ant and fungal species in which ants actively cultivate fungus as a food source.
Irreversible Genetic Locks in Ancient Amazonia
The ant-fungus partnership originated 50–66 million years ago in the Amazon basin following the K-Pg event. During this ecological shift, ancestral attine ants permanently lost the argininosuccinate lyase gene, eliminating the final step in their arginine biosynthesis pathway. This irreversible genetic loss removed any possibility of reverting to a generalized hunter-gatherer lifestyle. Consequently, the ants became immediately and irrevocably dependent on their fungal cultivars for essential amino acids.
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Flax root cortical cells containing paired arbuscules
A fluorescent microscopy image of a fungal arbuscule stained with WGA and Alexa Fluor
Vesicular arbuscular mycorrhizae in the terminal roots of Horse Gram plant
Bilayered glomoid spore of arbuscular mycorrhizal fungi in the root of Horse Gram
Positive effects of arbuscular mycorrhizal (AM) colonization The hyphal network of arbuscular mycorrhizal fungi (AMF) extends beyond the depletion zone (grey), accessing a greater area of soil for phosphate uptake. A mycorrhizal-phosphate depletion zone will also eventually form around AM hyphae (purple). Other nutrients that have enhanced assimilation in AM-roots include nitrogen (ammonium) and zinc. Benefits from colonization include tolerances to many abiotic and biotic stresses through induction of systemic acquired resistance.[11]
The chemical structure of MycRi-IV (C16:0,S), a Myc factor of Rhizophagus irregularis as indicated in Maillet, F et al. (2011) "Fungal lipochitooligosaccharide symbiotic signals in arbuscular mycorrhiza." Nature 469:58–63.
Arbuscular mycorrhiza
An arbuscular mycorrhiza is a type of mycorrhiza in which symbiont fungi penetrate the cortical cells of the roots of a vascular plant, forming arbuscules.
Silica-Preserved Partnerships in the Rhynie Chert
Early terrestrial flora relied on fungal associations long before modern root architectures evolved. Lower Devonian fossils dating back 400 m.yrs ago from the Rhynie chert contain structures that mirror contemporary Glomus species. These fossilized networks colonized primitive plants like Rhynia and Aglaophyton major, confirming that mycorrhizal relationships accompanied the initial conquest of land.
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