276:, needles, leaves, buds, and a host of other forms. The size of macrofossils and the depositional material in which they are preserved can similarly vary. The sporophyte phase of plants is morphologically distinct between different species, which permits species-level identification of macrofossil specimens and thus provides information about past vegetation with "high taxonomic resolution". To glean species-level data, macrofossil specimens must be carefully studied for distinct morphological and anatonomical features that permit their definitive assignment to a particular species, whether extant or extinct. The specificity and distinctiveness of macrofossil deposits of cones, seeds, and needles were paramount to the identification of the not-previously-known spruce
455:
37:
228:
666:, pollen and macrofossil specimens from a variety of species present during the Late Quaternary have been collected and studied across the globe. Such specimens are tied to specific locations that can be assigned accurate historical dates, which can then be linked to past climate data that has been independently gleaned from other sources such as
674:. Pairing records of past biota with climate data allows paleoecologists to reconstruct past vegetational landscapes. Given the rich spatial and temporal data embedded in the geologic record of the Late Quaternary, changes in the vegetational composition and structure of the landscape can be studied with great detail.
444:, the careful analysis of plant macrofossils was paramount to the description of the species and the documentation of its extinction. The interpretation of morphologically distinct pollen, in conjunction with this fossil evidence, has helped further characterize its former presence and distribution on the landscape.
409:
within the same genus. In some cases, pollen grains are morphologically indistinct even among different genera within the same plant family. As a result, fossil pollen often results in "taxonomic smoothing" that inhibits fine-scale resolution of past vegetation to the species level. However, examples of
818:
and its presumed linkage to climatic changes during the Last
Glacial Maximum, ecologists conjecture that consideration of this species “is potentially sobering in view of the likelihood of future climate changes, which could be of similar or greater rapidity, abruptness, and magnitude as those of the
798:
Paleoecological evidence supports a tendency for plant species to historically pursue the ‘migration’ route. The fossil record and the general lack of documented plant extinctions suggests that plant species have migrated far distances across continents in response to past environmental changes. Data
658:
The Late
Quaternary is well-represented in the geologic record at globally-distributed sites. Sites representative of the Late Quaternary that contain records of flora, fauna, and climates past can be dated with high degrees of accuracy through a variety of methods that allow observational inferences
291:
had cylindrical ovulate cones with “scales narrowly fan-shaped with rounded margins” that were somewhat irregular. The dimensions of a cone in its entirety varied between approximately 60–100 mm in length and 14–20 mm in diameter. The dimensions of the rounded, fan-shaped cone scales varied
777:
is the only species to go extinct during the Late
Quaternary, scientists suggest that “taxonomic smoothing” within collected pollen data and insufficient collections of plant macrofossils could be camouflaging other potential plant extinctions. Further discovery and examination of plant macrofossils
769:
These extinctions are largely attributed to a complementary role of human exploitation and rapid environmental change during the last deglaciation. A myriad of hypotheses have been proposed to explain these mammalian extinctions, but the current scientific consensus ascribes a role for both climate
408:
stage in the plant life cycle and ranges in size from 5-150 micrometers. Fossil pollen data is used to infer past vegetation, but pollen grains, unlike macrofossils, are often unable to be distinguished beyond the genera level given morphological similarities among pollen grains of distinct species
830:
Patterns of vegetational change are commonly used to infer future scenarios. Fossil records from the Late
Quaternary, when the magnitude and rate of climate change mirrored that which is predicted for the future, are often used to inform how biota of the present might respond to ongoing global
735:, which differs from the presumed cause of contemporaneous mammal extinctions. Given dramatic climatic changes occurring during the Late Quaternary at the time the plant extinction was recorded, it is postulated that the extinction is at least broadly linked to changing climatic regimes.
794:
The Late
Quaternary was a time of continuous climatic changes of varying rates and magnitudes. As Late Quaternary climates changed, plant species responded as individuals in a variety of ways, including toleration, migration, habitat shift, extinction, and altered population densities.
799:
from the fossil record also provides evidence that plant species have been able to respond to changing conditions by altering their population densities, transitioning between phases of rarity and abundance while nonetheless persisting on the landscape.
701:
is dated to approximately 15,000 years ago and represents the only documented tree species extinction of the Late
Quaternary. This extinction dates to approximately the time when the Earth was transitioning out of the Last Glacial Maximum and into the
1072:
Jackson, Stephen T.; Webb, Robert S.; Anderson, Katharine H.; Overpeck, Jonathan T.; Webb III, Thompson; Williams, John W.; Hansen, Barbara C.S. (February 2000). "Vegetation and environment in
Eastern North America during the Last Glacial Maximum".
479:
mostly originate from stream cut exposures composed of fluvial silt and clay soils from the Late
Quaternary. Other documented collection sites occur in western Tennessee, southwestern Georgia, and northwestern Georgia. The geographic range of
191:
period of Earth's history. At present, this is the only documented plant extinction from this geologic era. Hypotheses as to what specifically drove the extinction remain unresolved, but rapid and widespread climatic changes coincided with
209:
1125:
MANDER, L.; RODRIGUEZ, J.; MUELLER, P. G.; JACKSON, S. T.; PUNYASENA, S. W. (October 2014). "Identifying the pollen of an extinct spruce species in the Late
Quaternary sediments of the Tunica Hills region, south-eastern United States".
254:
as a new and distinct species, carefully analyzed plant macrofossil specimens of fossilized spruce needles and cones were assessed. After close examination, these specimens could not be assigned to any extant species of
714:
During the transition between the Last
Glacial Maximum and the Holocene, the Earth was experiencing exceptional warming. During this deglaciation, the climate underwent rapid and abrupt changes. The discovery of
655:
Period, that encompasses approximately the last 25,000 years of Earth's history. During this time, continuous climate change has occurred across varying timescales with different degrees of magnitude.
624:
species given past assemblages, other fossil collection sites where the plant has been found to occur with cool-temperate conifers suggests some degree of overlap in the environmental tolerances of
224:
William B. Critchfield. The plant was named to honor Critchfield and his longstanding "advocacy of understanding the role of Quaternary history in shaping genetic structure of conifer populations."
393:
pollen has yet to be collected specifically within fossilized reproductive structures of the plant to confirm association; scientists nonetheless hypothesize that the pollen is most likely that of
831:
changes. However, scientists suggest that “history is better suited to providing cautionary tales rather than specific images of future climate and vegetation change.” The demise and discovery of
207:
was first described by Stephen T. Jackson and Chengyu Weng in a 1999 paper titled, "Late Quaternary Extinction of a Tree Species in Eastern North America" published in the journal
765:
In contrast to this one known plant extinction during the Late Quaternary, significant numbers of mammalian extinctions took place during the same period in what is known as the
475:
have been collected from the Tunica Hills region in Louisiana and Mississippi, which maps to 31°N, 91°29'W. The fossil specimens that aided in the discovery and description of
425:
has been characterized, classified, and assessed with relative accuracy based on distinct morphological attributes of each species. Similarly, close analysis of hypothesized
631:
Eastern North American spruce species that remain extant have boreal and montane affinities and are entirely confined to cool climates. However, the affinities of extinct
731:
remains largely unresolved and is not currently tied to a specific, historical event or cause. There is no known linkage between human exploitation and the extinction of
261:
given distinctive morphological and anatomical features of their needles and cones. Fossil evidence thus supports the former existence of a distinct species of spruce:
272:
stage in the plant life cycle. Given significant variability among the sporophyte stage for different plant species, macrofossil specimens can exist as seeds, fruits,
608:
has been found to co-occur reveal information about its presumed environmental and habitat tolerances. The fossil collections that demonstrate an association between
303:
had ovate, winged seeds. The seeds varied in size from about 3.5-4.5 mm in length and 2.6-2.8 mm in width with wings spanning about 8–11 mm in length.
1172:
Birks, H. J. B.; Peglar, Sylvia M. (1980-10-01). "Identification of Picea pollen of Late Quaternary age in eastern North America: a numerical approach".
359:
fossil site known as Tunica Hills reveals that pollen collected here is morphologically distinct from, and thus not attributable to, that of the extant
802:
Despite paleoecological support for migration, toleration, and population density changes as past responses to environmental change, the discovery of
762:
the only plant extinction documented during the Late Quaternary, but it is one of very few plant extinctions known from the entire Quaternary Period.
1283:
Jackson, Stephen T.; Overpeck, Jonathan T. (2000). "Responses of plant populations and communities to environmental changes of the late Quaternary".
351:
pollen found to dominate in locations that coincide with fossil collection sites is likely attributable to the extinct spruce and thus reveals that
315:
were between 7–9 mm in length and 0.6-1.0 mm in diameter. These needles had a cross-section that was quadrangular, an acute apex, and two
1054:
454:
183:
formerly present on the landscape of North America, where it was once widely distributed throughout the southeastern United States. Plant
635:
likely differ from those of extant spruce given the environmental tolerances of the species with which it has been found to co-occur.
484:
spanned the southeastern United States, where it was once widespread. The species has been recorded from several sites dating to the
719:
s extinction at the time of this rapid and continuous climate change suggests that such changes may have contributed to its demise.
738:
Within the context of broader climatic changes, hypothesized factors potentially contributing to the decline and extinction of
571:
and other hardwood species also occurred. The former species assemblages revealed by macrofossil and pollen collections have
680:
existed on the landscape of North America during and directly preceding the Last Glacial Maximum of the Late Quaternary.
1395:
1212:"Morphometric analysis of pollen grains for paleoecological studies: classification of Picea from eastern North America"
766:
770:
and human impacts as driving large numbers of mammalian genera and species to extinction during the Late Quaternary.
563:
taxa. Fossil pollen data from the Tunica Hills region dates to between 24,670 and 17,530 years ago and suggests that
1469:
339:
was once dominant in the region surrounding the macrofossil collection sites now known to represent the extinct
489:
492:
and in Georgia. Considering all fossil collection sites together, paleoecologists suspect the former range of
36:
1423:
Koch, Paul L.; Barnosky, Anthony D. (December 2006). "Late Quaternary Extinctions: State of the Debate".
555:
148:
1352:
1292:
1135:
1082:
966:
567:
was the dominant species in the regional uplands surrounding this area, where smaller populations of
531:
485:
355:
was once widespread in the region. Evidence from morphometric analyses of pollen collected from the
572:
639:
is presumed to have had warmer but still overlapping temperature tolerances as compared to extant
1316:
31:
778:
is needed to determine whether other plant extinctions have occurred in addition to the loss of
436:
glean insight into past vegetation to catalog the historical presence of taxa on the landscape.
1343:
Davis, M. B. (2001-04-27). "Range Shifts and Adaptive Responses to Quaternary Climate Change".
1440:
1376:
1368:
1308:
1244:
1236:
1189:
1151:
1098:
1050:
1002:
984:
537:
1436:
377:. Given the distinctiveness of fossil pollen grains collected from this site of known former
1432:
1360:
1300:
1226:
1181:
1143:
1090:
1042:
992:
974:
413:
pollen being identified as morphologically distinct, species-level units exist. Pollen from
214:
1211:
549:
188:
1356:
1296:
1139:
1086:
970:
1464:
820:
747:
433:
61:
1094:
1458:
1320:
1046:
997:
954:
521:
367:
824:
684:
is currently the only plant extinction documented from the Late Quaternary period.
373:
361:
273:
233:
1364:
440:
pollen identifiable to the species level is particularly useful. In the case of
405:
381:
presence, scientists suggest that "the morphologically distinctive Tunica Hills
227:
184:
180:
210:
Proceedings of the National Academy of Sciences of the United States of America
1304:
671:
652:
401:
269:
74:
1444:
1372:
1312:
1240:
1193:
1155:
1102:
988:
979:
620:
species. Though thought to have an affinity for warmer conditions than other
268:
Plant macrofossils are fossilized deposits that represent the multicellular
1380:
1248:
1006:
1231:
743:
703:
667:
582:
has been found, it is documented as co-occurring with various species of
560:
559:
have also been made at these same sites. These species are all temperate
221:
114:
429:
pollen demonstrates a species-level analysis of spruce pollen granules.
955:"Late Quaternary extinction of a tree species in eastern North America"
593:
515:
404:, represents fossilized deposits of plant pollen grains reflecting the
104:
94:
84:
651:
The Late Quaternary is a time in geologic history, within the broader
1147:
328:
257:
124:
1185:
543:
453:
316:
226:
48:
584:
331:
data was also important to the description and documentation of
496:
spanned over 240,000 km (150,000 mi) in the region.
389:." It remains difficult to conclude this definitively because
292:
between 18–21 mm in length and 11-13.5 mm in width.
1037:
JACKSON, S; BOOTH, R (2007), "Validation of Pollen Studies",
616:
could tolerate warmer climate conditions than other, extant
397:
given its distinctiveness from pollen of other extant taxa.
1210:
Lindbladh, M.; O'Connor, R.; Jacobson, G. L. (2002-09-01).
432:
Pollen data remains one of the primary mechanisms by which
385:
pollen was probably produced by the extinct spruce species
187:
evidence reveals that this tree became extinct during the
789:
509:
At the Tunica Hills sites where many fossil specimens of
575:
to present plant communities in eastern North America.
462:
specimens, based on Figure 1 of Jackson and Weng, 1999.
458:
Map of approximate fossil collection site locations of
806:
reveals that extinction is another possible response.
659:
to be made at timescales between 10 and 10,000 years.
1425:
Annual Review of Ecology, Evolution, and Systematics
790:
Species' responses to change in the late Quaternary
953:Jackson, Stephen T.; Weng, Chengyu (1999-11-23).
750:ability, or a complete loss of suitable habitat.
450:Distribution, habitat, and environmental context
959:Proceedings of the National Academy of Sciences
727:The definitive root cause of the extinction of
1396:"The enduring mystery of Critchfield's spruce"
612:and temperate hardwood tree species suggests
8:
20:
1230:
996:
978:
400:Fossil pollen data, used in the field of
1437:10.1146/annurev.ecolsys.34.011802.132415
844:
1278:
335:. Fossil pollen evidence reveals that
1418:
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1262:
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1258:
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868:
513:have been discovered, collections of
7:
1394:St George, Zach (14 February 2021).
1338:
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1334:
1332:
1330:
1205:
1203:
1167:
1165:
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1118:
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1114:
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1067:
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1016:
866:
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862:
860:
858:
856:
854:
852:
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848:
600:Environmental and habitat tolerances
196:'s decline and ultimate extinction.
347:s presence, it is thought that the
1039:Encyclopedia of Quaternary Science
14:
810:Relation to modern climate change
723:Hypothesized causes of extinction
628:and extant members of the genus.
1041:, Elsevier, pp. 2413–2422,
773:Though it remains possible that
578:In other collection sites where
471:Many of the fossils documenting
35:
1047:10.1016/b0-444-52747-8/00225-8
1:
1128:Journal of Quaternary Science
1095:10.1016/s0277-3791(99)00093-1
835:is one such cautionary tale.
1365:10.1126/science.292.5517.673
767:Quaternary Extinction Event.
754:Contemporaneous extinctions
592:. These are cool-temperate
1486:
1219:American Journal of Botany
1174:Canadian Journal of Botany
1075:Quaternary Science Reviews
706:period of the Quaternary.
200:History and classification
16:Extinct species of conifer
1305:10.1017/s0094837300026932
785:Biodiversity implications
179:is an extinct species of
154:
147:
32:Scientific classification
30:
23:
980:10.1073/pnas.96.24.13847
490:Lower Mississippi Valley
241:were formerly attributed
647:Late Quaternary context
604:The species with which
467:Geographic distribution
220:as a patronym honoring
814:With the discovery of
463:
242:
1232:10.3732/ajb.89.9.1459
457:
230:
140:P. critchfieldii
780:Picea critchfieldii.
717:Picea critchfieldii'
710:Environmental change
693:Timing of extinction
532:Carpinus caroliniana
505:Co-occurring species
486:Last Glacial Maximum
345:Picea critchfieldii'
1357:2001Sci...292..673D
1297:2000Pbio...26S.194J
1140:2014JQS....29..711M
1087:2000QSRv...19..489J
971:1999PNAS...9613847J
965:(24): 13847–13852.
833:Picea critchfieldii
816:Picea critchfieldii
804:Picea critchfieldii
775:Picea critchfieldii
760:Picea critchfieldii
740:Picea critchfieldii
733:Picea critchfieldii
729:Picea critchfieldii
699:Picea critchfieldii
682:Picea critchfieldii
678:Picea critchfieldii
664:Picea critchfieldii
637:Picea critchfieldii
633:Picea critchfieldii
626:Picea critchfieldii
614:Picea critchfieldii
610:Picea critchfieldii
606:Picea critchfieldii
580:Picea critchfieldii
556:Juniperus americana
511:Picea critchfieldii
473:Picea critchfieldii
460:Picea critchfieldii
442:Picea critchfieldii
427:Picea critchfieldii
395:Picea critchfieldii
391:Picea critchfieldii
387:Picea critchfieldii
379:Picea critchfieldii
357:Picea critchfieldii
353:Picea critchfieldii
341:Picea critchfieldii
333:Picea critchfieldii
313:Picea critchfieldii
301:Picea critchfieldii
289:Picea critchfieldii
278:Picea critchfieldii
263:Picea critchfieldii
252:Picea critchfieldii
213:. They coined the
205:Picea critchfieldii
194:Picea critchfieldii
176:Picea critchfieldii
161:Picea critchfieldii
25:Picea critchfieldii
697:The extinction of
464:
243:
167:Jackson & Weng
1470:Prehistoric trees
1351:(5517): 673–679.
1180:(19): 2043–2058.
1056:978-0-444-52747-9
538:Fagus grandifolia
172:
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1225:(9): 1459–1467.
1216:
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1148:10.1002/jqs.2745
1122:
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982:
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494:P. critchfieldii
482:P. critchfieldii
477:P. critchfieldii
239:P. critchfieldii
215:specific epithet
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1291:(S4): 194–220.
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662:As is true for
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550:Ulmus americana
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469:
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434:paleoecologists
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311:The needles of
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189:Late Quaternary
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11:
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1431:(1): 215–250.
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1134:(7): 711–721.
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1081:(6): 489–508.
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75:Gymnospermae
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406:gametophyte
246:Description
237:, to which
185:macrofossil
181:spruce tree
1459:Categories
839:References
742:include a
688:Extinction
672:tree rings
653:Quaternary
402:palynology
270:sporophyte
81:Division:
1445:1543-592X
1373:0036-8075
1321:232398484
1313:0094-8373
1241:0002-9122
1194:0008-4026
1156:0267-8179
1103:0277-3791
989:0027-8424
748:dispersal
668:ice cores
588:and with
573:no-analog
133:Species:
95:Pinopsida
85:Pinophyta
45:Kingdom:
1381:11326089
1249:21665747
1007:10570161
744:pathogen
704:Holocene
561:hardwood
343:. Given
222:botanist
115:Pinaceae
111:Family:
1353:Bibcode
1345:Science
1293:Bibcode
1136:Bibcode
1083:Bibcode
967:Bibcode
821:glacial
594:conifer
569:Quercus
516:Quercus
500:Ecology
488:in the
327:Fossil
319:ducts.
307:Needles
231:Extant
158:†
137:†
121:Genus:
105:Pinales
101:Order:
91:Class:
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371:, and
329:pollen
323:Pollen
1465:Picea
1400:Salon
1317:S2CID
1215:(PDF)
998:24153
819:last
641:Picea
622:Picea
618:Picea
585:Pinus
565:Picea
544:Carya
438:Picea
411:Picea
383:Picea
349:Picea
337:Picea
317:resin
296:Seeds
284:Cones
258:Picea
126:Picea
69:Clade
56:Clade
1441:ISSN
1407:2021
1377:PMID
1369:ISSN
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