Abstract Detail

Paleobotany

Benca, Jeffrey [1], Duijnstee, Ivo [2], Looy, Cindy [3].

Pollen malformations as indicators of past environmental stress: Comparing background variation with heightened UV-B exposure in modern conifers.

Widespread malformations in fossilized saccate (winged) pollen of gymnosperms have been proposed as a biological stress response during the end-Permian crisis (252 Ma). However, it is not well established how frequently, variably or consistently pollen malformations are expressed across modern gymnosperm lineages under near-optimal conditions or environmental stress. To evaluate the utility of pollen malformations as a paleoenvironmental stress indicator, we compared their frequency and variation in pollen yields spanning 14 conifer genera of Pinaceae and Podocarpaceae sampled from lowland gardens of the United States under near-optimal conditions. Although malformations comprise <3% of pollen yields in 12 of the 13 bisaccate genera studied, they represent >10% of yields in the only trisaccate lineage analyzed, Dacrycarpus dacrydioides under near-optimal conditions. We detected no phylogenetic pattern in the types of malformations expressed between bisaccate lineages in the baseline comparison. Additionally, the baseline pollen yields were compared with those produced by Pinus mugo “Columnaris” grown under an abiotic stress- specifically three experimentally heightened UV-B regimes proposed for the end-Permian crisis. UV-B irradiated P. mugo produced significantly higher frequencies of malformations and the type of malformations expressed deviated from bisaccate lineages under garden settings. These results suggest that (1) bisaccate pollen types maintain a high degree of morphological conservatism under present near-optimal growth conditions while trisaccate pollen types do not, and (2) environmental stress can significantly alter the frequency and expression of malformations in modern conifers relative to near-optimal conditions. Based on these results, malformation frequencies exceeding 3% in bisaccate pollen yields can be used as an indicator of paleoenvironmental stress while trisaccate lineages are not suitable for such assessments.

1 - Burke Museum of Natural History & Culture, Paleobotany, 4300 15th Ave NE, Seattle, WA, 98105, USA
2 - University of California, Berkeley, Integrative Biology, 2033 Valley Life Sciences Building, #3140, Berkeley, CA, 94720, USA
3 - Integrative Biology, 3060 Valley Life Sciences Bldg #3140, Berkeley, CA, 94720, United States

Keywords:
pollen
Abiotic stress
UV-B
Saccate
Conifers
Mass extinctions
End-Permian.

Presentation Type: Oral Paper
Session: PAL5, Paleobotany III: Patterns and trends
Location: Virtual/Virtual
Date: Tuesday, July 28th, 2020
Time: 3:15 PM
Number: PAL5002
Abstract ID:265
Candidate for Awards:None