Why are so few island bryophytes endemic?
Mirolo S, Ledent A, González-Mancebo JM, Gabriel R, Sim-Sim M
Island Biogeography
Those velvety green mosses carpeting the rocks and logs in shaded ravines or ancient woodlands are ancient travelers — more cosmopolitan than the rarest orchid — and understanding why they resist becoming unique island treasures reframes how we read biodiversity in any moss-rich corner you explore.
Mosses and liverworts are champion long-distance travelers — their tiny spores drift on wind across oceans — so island populations stay genetically connected to mainland relatives and rarely evolve into fully separate species. When they do slowly diverge on islands, they often spread back to the continent before the split is complete, erasing their 'found only here' status. Flowering plants, by contrast, tend to explode into many new species once stranded on an island, which is why places like the Canary Islands are packed with unique wildflowers but not unique mosses.
Key Findings
More than one-third of Macaronesian bryophyte species showed genetic signals of incipient speciation, but speciation proceeds slowly via long-distance dispersal and allopatry rather than in-place radiation.
At least 50% of Macaronesian endemic bryophytes originated from outside Europe, compared to over 90% of endemic flowering plants tracing back to European/Mediterranean ancestors — indicating very different colonization histories.
Sympatric radiation, which drives 56% of all Macaronesian flowering-plant endemics, virtually never occurs in island bryophytes, making endemism rates an unreliable proxy for speciation rates in this group.
chevron_right Technical Summary
Island mosses and liverworts have far fewer species found nowhere else on Earth compared to flowering plants, and this study explains why: they spread too easily between continents to stay isolated long enough to evolve into new species, and when they do speciate on islands, they often spread back to the mainland and lose their 'endemic' status.
Abstract Preview
Endemism, a hallmark of island biodiversity, reaches its lowest levels among bryophytes compared with other land plants. Whether this pattern reflects low diversification rates, and why, or whether...
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Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta sensu stricto. Bryophyta may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hornworts. Mosses typically form dense green clumps or mats, often in damp or shady locations. The in...