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Regrowth of Little Ice Age bryophytes exhumed from a polar glacier: the relevance of totipotency to biological refugia

La Farge, Catherine 1 ; Williams, Krista H 2 ; England, John H 3

1 University of Alberta
2 University of Alberta
3 University of Alberta

Across the Canadian Arctic Archipelago, widespread ice retreat during the 20th century has sharply accelerated since 2004 1,2. The retreat of Teardrop Glacier, central Ellesmere Island, Nunavut (Fig. 1), is exposing intact plant communities overridden during the Little Ice Age (LIA, 1550-1850 AD). Bryophyte populations exhumed from beneath the cold-based ice margin show remarkable preservation, including unexpected signs of regrowth (in vivo). To test their viability, these populations were collected along the ice margin for growth chamber experiments (in vitro). Based on measured rates of ice retreat spanning the past several decades populations within 5 m of the ice margin have been exposed recently in the last several years. These LIA populations are distinct from modern colonizing species in both population size and species diversity. Results include the first successful regeneration of several moss species from subglacial vegetative material, including Aulacomnium turgidum. The regeneration of presumably dead, land-plant tissue significantly expands our understanding of modern glacial ecosystems as biological reservoirs. It also challenges the traditional concept of Ice Age refugia that confines land plant recolonization to populations that survived above and beyond glacier margins3,4. Most living bryophyte cells have the capacity to reprogram the developmental pathway into a meristematic state (totipotency) in response to interruption. This cellular feature has been compared recently to faunal stem cells5. Our data indicates that bryophytes can be reactivated from 400 yr old, subglacial populations. Resilience of these extremophiles aligns bryophytes with bacteria, fungi, cyanobacteria and green algae, rather than other land plants (lycopods, ferns, gymnosperms, angiosperms). Bryophytes have a critical role in the establishment, colonization, and maintenance of polar terrestrial ecosystems, otherwise inhospitable for many land plants.

  1. Overpeck, J. et al. Arctic environmental change of the last four centuries. Science 278, 1251– 1256 (1997).

  2. Gardner, A. S. et al. Sharply increased mass loss from glaciers and ice caps in the Canadian Arctic Archipelago. Nature 473, 357-360 (2011).

  3. Brochmann, C., Gabrielsen, T. M., Nordal, I., Landvik J. Y., Elven, R. Glacial survival or tabula rasa? The history of North Atlantic biota revisited. Taxon 52, 417-450 (2003).

  4. Fernald, M. L. Persistence of plants in unglaciated areas of boreal America. Mem. Am. Acad. Arts Sci. 15, 239-342 (1925).

  5. Ishikawa, M. et al. Physcomitrella cyclin-dependent kinase a links cell cycle reactivation to other cellular changes during reprogramming of leaf cells. Plant Cell 23, 2924–2938 (2011).

 

Fig 1.

Teardrop Glacier, Sverdrup Pass, central Ellesmere Island, Nunavut. Note: Little Ice Age trimline ~ 200 m beyond the ice margin. Measured ice retreat has rapidly accelerated since 2004 exposing pristine LIA plant communities composed of bryophytes and vascular plants.

 

 

 

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