Evolutionary rates in "living fossils" across the Tree of Life
- 1University of Sydney
Abstract
Lineages that have undergone little apparent evolutionary change over long geological intervals are often described as "living fossils", with iconic examples including the coelacanth, tuatara, and Ginkgo. However, studies of morphological and molecular data have produced mixed evidence regarding whether living fossils have evolved more slowly than their relatives. We tested for reduced evolutionary rates using a sister-pairs approach, analysing a comprehensive set of morphological and molecular data for 45 living-fossil lineages and their close relatives across the Tree of Life. Living-fossil lineages showed substantially reduced rates of morphological evolution, whereas evidence for reduced molecular rates was weaker. To test whether this pattern could be explained by species poverty, we also analysed other depauperate lineages (species-poor clades contrasted with species-rich sister clades) and found a weak tendency towards reduced molecular rates but without a corresponding slowdown in morphological evolution. Our study reveals that the living-fossil concept captures a quantifiable pattern of prolonged morphological conservatism, but also suggests that living fossils lack other shared biological or life-history characteristics that might unite them as a group.
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BibTeX
@misc{cascini2026evolutionary,
title = {{Evolutionary rates in "living fossils" across the Tree of Life}},
author = {M. Cascini and E. K. Lopez Estrada and D. A. Duchene and S. Ho},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.03.756400},
url = {https://www.biorxiv.org/content/10.64898/2026.10.03.756400v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Evolutionary rates in "living fossils" across the Tree of Life
AU - M. Cascini
AU - E. K. Lopez Estrada
AU - D. A. Duchene
AU - S. Ho
PY - 2026
DA - 2026/10/03
PB - bioRxiv
DO - 10.64898/2026.10.03.756400
UR - https://www.biorxiv.org/content/10.64898/2026.10.03.756400v1
AB - Lineages that have undergone little apparent evolutionary change over long geological intervals are often described as "living fossils", with iconic examples including the coelacanth, tuatara, and Ginkgo. However, studies of morphological and molecular data have produced mixed evidence regarding whether living fossils have evolved more slowly than their relatives. We tested for reduced evolutionary rates using a sister-pairs approach, analysing a comprehensive set of morphological and molecular data for 45 living-fossil lineages and their close relatives across the Tree of Life. Living-fossil lineages showed substantially reduced rates of morphological evolution, whereas evidence for reduced molecular rates was weaker. To test whether this pattern could be explained by species poverty, we also analysed other depauperate lineages (species-poor clades contrasted with species-rich sister clades) and found a weak tendency towards reduced molecular rates but without a corresponding slowdown in morphological evolution. Our study reveals that the living-fossil concept captures a quantifiable pattern of prolonged morphological conservatism, but also suggests that living fossils lack other shared biological or life-history characteristics that might unite them as a group.
ER -