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High Plant Diversity in Eocene South America: Evidence from Patagonia

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Tropical South America has the highest plant diversity of any region today, but this richness is usually characterized as a geologically recent development (Neogene or Pleistocene). From caldera-lake beds exposed at Laguna del Hunco in Patagonia, Argentina, paleolatitude approximately 47 degrees S, we report 102 leaf species. Radioisotopic and paleomagnetic analyses indicate that the flora was deposited 52 million years ago, the time of the early Eocene climatic optimum, when tropical plant taxa and warm, equable climates reached middle latitudes of both hemispheres. Adjusted for sample size, observed richness exceeds that of any other Eocene leaf flora, supporting an ancient history of high plant diversity in warm areas of South America.
Selected plant taxa representing the excellent preservation and taxonomic and morphological diversity of the Laguna del Hunco flora (33, 36). Scale bars, 1 cm. Parentheses indicate Museo Egidio Feruglio (MEF) specimen number and locality (Fig. 2). (A) Attached foliage of callitroid Cupressaceae similar to extant Austrocedrus (South America ) and to several Australasian genera (MEF 971, loc. 13). (B) Attached compound leaf of " Lomatia " preferruginea (Proteaceae), part and counterpart, with lobed and toothed leaflets (972, 15). (C) Shoot and attached foliage of Podocarpaceae (973, 15). At least three other species of podocarps were found. (D) Complete , pinnatifid leaf of Lomatia occidentalis (Proteaceae) (974, float specimen). (E) " Myrica " mira, leaf (affinity unknown), with distinctive paired teeth along margin (975, 13). (F) Myrtaceae, leaf, showing prominent intramarginal vein (976, 13). (G) Attached infructescence and leaf of Gymnostoma sp. (Casuarinaceae, extant in Australasia). Note exserted bracts of infructescence and grooved surface of the nodular leaf (977, 22). (H) Propeller-like fruit, with four persistent sepals, of an unknown dicot species (?Cunoniaceae), with constricted sepal bases and thickened central disk (978, 6). (I) Cycad leaf similar to extant Dioon, with toothed margin (470, 4). ( J) Malvales, three-lobed leaf, with basally actinodromous primary veins (979, 11). (K) Leaf-margin detail of unknown dicot species " TY62, " showing compound, sharp-pointed teeth with flexuous or convex flanks and chevroned, opposite-percurrent tertiaries (980, 15). (L) Myrtaceae, infructescence (981, float specimen). (M) Araucaria sp. (Araucariaceae), attached seed and cone scale (982, 13). Araucaria foliage and a second type of cone scale were also found.
… 
Rarefied richness of dicot leaf species at Laguna del Hunco and quantitatively sampled sites from the Eocene of North America. Left column in key and LH flora are lacustrine assemblages ; right column is fluvially deposited floras. Dashed gray lines, 95% confidence intervals. Leaf-count data (33): Republic (61); Green River (62); Florissant (63); Puget Group (42, 64); Chalk Bluffs (65); Wyoming EECO (66, 67). (A) Single-quarry collections, labeled with abbreviations corresponding to the key, shown up to 500 specimens for detail and including all four principal localities for Laguna del Hunco (Fig. 2, asterisks). Wy-N and Wy-S label samples from northern (66) and southern (67) Wyoming , respectively. For North American floras with data from more than one locality, only the most diverse quarry is shown, and confidence intervals are given , for readability, only for the most diverse samples from LH and North America (Florissant ). (B) Lumped counts of three or more quarries from a single area, as labeled and shown up to 5000 specimens. For LH, rarefactions are shown for all 25 quarries, for the four principal quarries as in (A), and for the three uppermost principal quarries (LH-2, 4, and 6). Rarefactions computed using Analytic Rarefaction 1.3, by S. Holland (68). Ages, geologic settings, and estimated MATs and MAPs (if available) from leaf-margin and leaf-area analysis; climatic estimates are adjusted from published values in some cases so that all MATs and MAPs in this paper are derived using the identical formulae (34): Republic, Washington, 49 to 50 Ma lake in volcanic highlands, 13°C (61, 69); Green River flora (sample from Bonanza, Utah), 43 to 48 Ma intermontane lake, 15°C, 84 cm (47, 70–72); Florissant, Colorado, 34 Ma montane lake, 12° to 13°C (37, 63, 73, 74); Puget Group flora, Washington, middle to late Eocene delta plain, 16°C (42); Chalk Bluffs, California, 49 to 50 Ma fluvial system, 17°C, 160 cm (47, 65, 72, 75); Wyoming EECO, 53 Ma swamps and distal splays, 21° to 22°C, 140 cm (18, 66, 67).
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High Plant Diversity in Eocene
South America: Evidence from
Patagonia
Peter Wilf,
1,2,3
* N. Rube´n Cu´neo,
4
Kirk R. Johnson,
5
Jason F. Hicks,
5
Scott L. Wing,
6
John D. Obradovich
7
Tropical South America has the highest plant diversity of any region today, but
this richness is usually characterized as a geologically recent development
(Neogene or Pleistocene). From caldera-lake beds exposed at Laguna del Hunco
in Patagonia, Argentina, paleolatitude 47°S, we report 102 leaf species.
Radioisotopic and paleomagnetic analyses indicate that the flora was deposited
52 million years ago, the time of the early Eocene climatic optimum, when
tropical plant taxa and warm, equable climates reached middle latitudes of both
hemispheres. Adjusted for sample size, observed richness exceeds that of any
other Eocene leaf flora, supporting an ancient history of high plant diversity in
warm areas of South America.
There is little evidence but much debate re-
garding how long the exceptional plant diver-
sity of tropical South America has existed (1,
2). Most explanations have emphasized the
late Neogene or Pleistocene (37 ), although
the mechanisms and relative importance of
geologically recent speciation are disputed
(812). Evidence for or against earlier diver-
sity is sparse (1317). During the early Eo-
cene, when maximum global temperatures
for the Cenozoic occurred (18, 19), plants
with tropical affinities grew at middle and
high latitudes (2023). From quantitative
sampling of a middle-latitude flora, we
present evidence for extraordinary plant di-
versity in early Eocene South America.
The flora we studied comes from the vicinity
of Laguna del Hunco (LH) in northwestern
Chubut Province, Patagonia, Argentina (24, 25).
It is derived from tuffaceous caldera-lake depos-
its, known as the Tufolitas Laguna del Hunco, of
the middle Chubut River volcanic-pyroclastic
complex (25, 26). Previous K/Ar analyses of
associated volcanic rocks have indicated a late
Paleocene to middle Eocene age for the flora
(27, 28). Marine sediments in nearby basins and
tectonic evidence suggest that elevation was low
and that the climate had a maritime influence
(29, 30). The site is near the southern limit of the
Paleogene Neotropical flora (20, 21, 23), and it
also contains a number of taxa that are extinct in
South America today but have living relatives in
Australasian floras (3133) (Fig. 1).
We measured and correlated stratigraphic
sections through the Tufolitas LH that contained
25 fossil localities, three datable tuffs, and six
paleomagnetic reversals (Fig. 2) (34). We iden-
tified 1536 specimens of compression-impres-
sion plant macrofossils; nearly all (98%) were
found between the 37- and 99-m levels of the
aggregate systems (Fig. 2). Four quarries were
selected for intensive sampling (64% of speci-
mens) (Fig. 2).
Results from
40
Ar/
39
Ar analyses of the
tuffs indicated ages near 52 Ma (million years
ago) (Fig. 2) (34). The two youngest ages are
at odds with superposition, but their confi-
dence intervals either overlap or nearly over-
lap each other’s means. From paleomagnetic
results, we assign the most fossiliferous strata
to the upper portion of magnetic polarity
subchron (C) 23n.2r and the lower half of
C23n.2n (Fig. 2) (34). These data place the
flora within the early Eocene climatic opti-
mum (EECO), an 2-million-year interval
that is known for the warmest sustained tem-
peratures of the Cenozoic (19). At 52 Ma, the
latitude of LH was 47° to 48°S (35).
In the flora, we recognize 102 leaf species
(includes described species and undescribed
morphospecies) of dicots, monocots, conifers,
ginkgophytes, cycads, and ferns and an addi-
1
Department of Geosciences, Pennsylvania State Uni-
versity, University Park, PA 16802, USA.
2
Museum of
Paleontology, University of Michigan, Ann Arbor, MI
48109, USA.
3
Department of Earth and Environmental
Science, University of Pennsylvania, Philadelphia, PA
19104, USA.
4
Museo Paleontolo´gico Egidio Feruglio,
Trelew, Chubut 9100, Argentina.
5
Department of
Earth Sciences, Denver Museum of Nature & Science,
Denver, CO 80205, USA.
6
Department of Paleobiol-
ogy, Smithsonian Institution, Washington, DC 20560,
USA.
7
U.S. Geological Survey, Lakewood, CO 80225,
USA.
*To whom correspondence should be addressed. E-
mail: pwilf@geosc.psu.edu
Fig. 1. Selected plant
taxa representing the ex-
cellent preservation and
taxonomic and morpho-
logical diversity of the La-
guna del Hunco flora (33,
36). Scale bars, 1 cm. Pa-
rentheses indicate Museo
Egidio Feruglio (MEF)
specimen number and
locality (Fig. 2). (A) At-
tached foliage of cal-
litroid Cupressaceae
similar to extant Aus-
trocedrus (South Amer-
ica) and to several Aus-
tralasian genera (MEF
971, loc. 13). (B) At-
tached compound leaf
of Lomatia preferrug-
inea (Proteaceae), part
and counterpart, with
lobed and toothed leaf-
lets (972, 15). (C) Shoot
and attached foliage of
Podocarpaceae (973,
15). At least three other
species of podocarps
were found. (D) Com-
plete, pinnatifid leaf of
Lomatia occidentalis
(Proteaceae) (974, float specimen). (E)“Myrica mira, leaf (affinity unknown), with distinctive paired
teeth along margin (975, 13). (F) Myrtaceae, leaf, showing prominent intramarginal vein (976, 13). (G)
Attached infructescence and leaf of Gymnostoma sp. (Casuarinaceae, extant in Australasia). Note
exserted bracts of infructescence and grooved surface of the nodular leaf (977, 22). (H) Propeller-like
fruit, with four persistent sepals, of an unknown dicot species (?Cunoniaceae), with constricted sepal
bases and thickened central disk (978, 6). (I) Cycad leaf similar to extant Dioon, with toothed margin
(470, 4). ( J) Malvales, three-lobed leaf, with basally actinodromous primary veins (979, 11). (K)
Leaf-margin detail of unknown dicot species “TY62,” showing compound, sharp-pointed teeth with
flexuous or convex flanks and chevroned, opposite-percurrent tertiaries (980, 15). (L) Myrtaceae,
infructescence (981, float specimen). (M) Araucaria sp. (Araucariaceae), attached seed and cone scale
(982, 13). Araucaria foliage and a second type of cone scale were also found.
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4 APRIL 2003 VOL 300 SCIENCE www.sciencemag.org122
tional 22 reproductive species from these
groups (Fig. 1) (33, 34, 36). Dicots were the
most diverse group, with 88 leaf species.
To evaluate species diversity relative to
sample size, we derived rarefaction curves
from relative abundance data of dicot leaves
for the four most heavily sampled quarries,
both individually (Fig. 3A) and in combina-
tion (Fig. 3B), as well as for the bulk flora
(Fig. 3B). For comparison, we rarefied leaf
counts for six Eocene floras from lacustrine
and fluvial settings at middle paleolatitudes
of western North America (Fig. 3). These six
are diverse, well studied, and quantitatively
sampled in a manner similar to the sampling
at LH. The total known diversity of some of
the North American floras is much greater
than indicated by rarefaction analyses, but
this reflects selective sampling of unknown
numbers of specimens over years or decades
(3739).
None of the North American floras pro-
vides a precise temporal and depositional an-
alog to the LH flora, but they represent sim-
ilar age (Wyoming floras), topographic and
depositional setting (Republic, Green River,
Florissant), or maritime climate (Puget
Group, Chalk Bluffs) (legend to Fig. 3). The
Green River and Florissant floras are known
for preservation of attached plant organs
(37). No Eocene North American floras are
available from caldera lakes, a setting that
might favor the preservation of plant diversi-
ty because of steep surrounding topography
(38, 40). However, topography surrounding
the caldera lake at LH was more subdued
than it was to the south (25), and even in lake
basins with high relief, remains of plants
from elevated areas are rare (41). The most
reliable comparisons are those with single
quarries from fossil lakes (Fig. 3A, Republic,
Green River, and Florissant). The combined
quarries (Fig. 3B) introduce varying amounts
of temporal and spatial mixing that may in-
crease diversity artifactually, with perhaps
the greatest effect in the Puget Group (42).
The rarefaction analyses show that the LH
flora is significantly more rich for its sample
size than any Eocene leaf flora from North
America (Fig. 3). Three of the four principal
quarries from LH plot above (quarry 2) or
within the 95% confidence limits of the most
diverse North American localities (Fig. 3A).
The same high diversity is apparent in rar-
efactions of the bulk flora and for subsets of
the principal quarries (Fig. 3B). Nearly the
same rarefaction curves result if the most
diverse LH locality is removed (not shown).
Thus, the elevated diversity observed at LH
does not depend on a single locality or on the
aggregation of numerous localities. Total
richness also significantly exceeds that
known from Eocene leaf floras of Germany
(43), Australia (44), and Tanzania (45).
The mean annual temperature (MAT) esti-
mated from leaf-margin analysis (34, 46)ofthe
bulk flora is 15.6° 2.0°C (Fig. 2). Individual
sampling levels suggest an overall warming of
6°C (from 12° to 18°C), although we place
the greatest confidence in the bulk estimate
because of the large number of species used
(Fig. 2). Mean annual precipitation (MAP) is
estimated from leaf-area analysis (47 ) as 100 to
120 cm, with no evidence of significant change
within the sampled interval (Fig. 2) (34 ). This
estimate should be taken as a minimum: The
high diversity of the flora suggests that the
upper ranges of leaf size for many rare species
are not yet sampled, and transport into lakes
generally selects against large leaves (48). The
combined presence of palms, cycads, araucar-
ian conifers, diverse podocarps, and Gymnos-
toma (Fig. 1), along with the absence of Notho-
fagus, provide evidence of an equable climate,
with winter temperatures warmer than 10°C
and abundant rainfall (20, 22, 32, 4951).
The precipitation proxies indicate that
the Patagonian Andes to the west of LH did
not cast a significant rain shadow, support-
ing other evidence for their low elevation
(29, 52). Our temperature data are corrob-
orated by estimated sea-surface temperatures
of 16° to 17°C during the EECO at four
deep-sea sites from similar paleolatitudes in
the South Atlantic (53). Marine and terrestrial
proxy data from the Antarctic and from areas
north of LH indicate temperatures that brack-
et our results latitudinally (5355). Our
estimated paleotemperatures for LH are
Fig. 2. Stratigraphic section of the Tufolitas Laguna del Hunco, aggregate thickness 170 m, showing
principal lithologies; six local sections; correlations (yellow) along marker beds for the five
continuous sections (B to F); plant localities; radiometrically dated samples, with 95% confidence
intervals; virtual geomagnetic pole latitudes (VGP lat.); intervals of reversed and normal polarity
(R1, N1, etc.), assignments to magnetic polarity subchrons (we interpret the single-site reversals,
N1 and R3, as unidentified cryptochrons of short duration); and climatic results from leaf-margin
(MAT ) and leaf-area (MAP) analyses (34). The base of the Tufolitas LH was found only in section
A, which could not be traced accurately across a fault to continuous sections B to F; these sections
were measured on outcrops extending 1.3 km along a single drainage and were correlated by bed
tracing. Section A is placed at an artificially high position in the figure (34). Most plant fossils
occurred in tuffaceous mudrocks (34). Asterisks, the four principal quarries (see text and Fig. 3A).
Red circles with connecting line, means of three individually measured, oriented paleomagnetic
samples per site for which circular standard deviation was 35°. Open circles, paleomagnetic
sample means calculated by principal components analysis (59). Open triangles, sample means
calculated by Fisher statistics (60). Labels show the number of species used in the estimates for
both MAT and MAP. MAT error bars indicate 1 of binomial error or 2°C, whichever is greater
(46); MAP error bars are 1 (47). Climatic results for the “best levels” include species from
principal quarries and ancillary quarries excavated along strike (34). Bulk estimates include four
species found only in float rocks not assignable to a precise stratigraphic level (34). Plant locality
19, not in a measurable position, is not shown.
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www.sciencemag.org SCIENCE VOL 300 4 APRIL 2003 123
less than or approximately equal to most of
the North American sites, and precipitation
estimates are also mostly comparable (leg-
end to Fig. 3). Thus, climate biases against
or is neutral with regard to our observation
of relatively high species richness at LH
(56, 57 ).
Other evidence also is consistent with el-
evated floral diversity in Paleogene South
America. The Eocene flora of Rı´o Pichileufu´,
from 160 km NNW of LH, contains many
of the same species as the LH flora and
appears to be as diverse (33, 58), which
suggests that rich, subtropical vegetation ex-
isted over a large portion of Eocene Patago-
nia. Palynological data from the Paleocene
and Eocene of Colombia and Venezuela
show significant diversification in association
with warming temperatures and increased
rainfall across the Paleocene-Eocene bound-
ary, which suggests in situ speciation (16,
17). Finally, numerous plant families that are
now speciose in South America have Paleo-
cene and Eocene fossil records there (13, 15,
21), demonstrating persistence and suggest-
ing early diversification.
The current richness of South American
floras has resulted from many factors, which
include immigration, isolation, low extinction
rates, and natural selection related to climate
change and orogeny. These have been used to
hypothesize a late Cenozoic origin of high
Neotropical diversity, but our results suggest
that elevated plant diversity is an ancient
feature of South America.
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Fig. 3. Rarefied richness
of dicot leaf species at
Laguna del Hunco and
quantitatively sampled
sites from the Eocene
of North America. Left
column in key and LH
flora are lacustrine as-
semblages; right col-
umn is fluvially depos-
ited floras. Dashed gray
lines, 95% confidence
intervals. Leaf-count
data (33): Republic
(61); Green River (62);
Florissant (63); Puget
Group (42, 64); Chalk
Bluffs (65); Wyoming
EECO (66, 67). (A) Sin-
gle-quarry collections,
labeled with abbrevia-
tions corresponding to
the key, shown up to
500 specimens for de-
tail and including all
four principal localities
for Laguna del Hunco
(Fig. 2, asterisks). Wy-N
and Wy-S label sam-
ples from northern (66)
and southern (67) Wy-
oming, respectively. For
North American floras
with data from more
than one locality, only
the most diverse quar-
ry is shown, and confi-
dence intervals are giv-
en, for readability, only
for the most diverse
samples from LH and
North America (Floris-
sant). (B) Lumped
counts of three or more
quarries from a single
area, as labeled and
shown up to 5000
specimens. For LH, rarefactions are shown for all 25 quarries, for the four principal quarries as in (A), and
for the three uppermost principal quarries (LH-2, 4, and 6). Rarefactions computed using Analytic
Rarefaction 1.3, by S. Holland (68). Ages, geologic settings, and estimated MATs and MAPs (if available)
from leaf-margin and leaf-area analysis; climatic estimates are adjusted from published values in some
cases so that all MATs and MAPs in this paper are derived using the identical formulae (34): Republic,
Washington, 49 to 50 Ma lake in volcanic highlands, 13°C (61, 69); Green River flora (sample
from Bonanza, Utah), 43 to 48 Ma intermontane lake, 15°C, 84 cm (47, 7072);
Florissant, Colorado, 34 Ma montane lake, 12° to 13°C (37, 63, 73, 74); Puget Group flora,
Washington, middle to late Eocene delta plain, 16°C (42); Chalk Bluffs, California, 49 to 50
Ma fluvial system, 17°C, 160 cm (47, 65, 72, 75); Wyoming EECO, 53 Ma swamps and
distal splays, 21° to 22°C, 140 cm (18, 66, 67).
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4 APRIL 2003 VOL 300 SCIENCE www.sciencemag.org124
inspection of type material from the Eocene ´o
Pichileufu´ flora (58) confirms the reported taxonomic
similarity to the LH flora (26), and our preliminary
field data from ´o Pichileufu´ suggest a diversity
comparable to LH. Formal taxonomic knowledge of
the LH flora is not yet sufficient to allow rigorous
analysis of familial and generic diversity (34, 36). All
1215 voucher specimens for this study are housed at
MEF, including exemplar specimens of each species.
Fieldwork reported here took place in November
1999. We do not attempt to integrate our data with
previous collections in the United States and Argen-
tina, which would be inappropriate for our strati-
graphic methodology.
34. Supporting methods, data, and analyses are available
on Science Online.
35. W. W. Hay et al., Geol. Soc. Am. Spec. Pap. 332,1
(1999).
36. The most abundant leaf taxa in the bulk flora were
Celtisameghenoi (?Celtidaceae, 233 specimens),
Myrcia chubutensis (Myrtaceae, 183), cf. Schmide-
liaproedulis (Sapindaceae, 113), Leguminosae sp.
“TY117” (110), Tetracera patagonica (?Cunoni-
aceae, 89), Myrica mira (unknown affinity, 65), and
Lauraceae sp. “TY84” (52 specimens). Also present
are Ginkgo patagonica, Akania patagonica, and sev-
eral other leaf species of Sapindales; Leguminosae
pods and leaves; Orites bivascularis fruits; and several
leaf species of Proteaceae. Additional groups that are
probably present include Clusiaceae, Escalloniaceae,
Euphorbiaceae, Flacourtiaceae, Monimiaceae, and Rh-
amnaceae.
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137 (2001).
38. High Eocene richness in the Northern Hemisphere is
known from fruit, seed, and pollen floras, but these
are not directly comparable to leaf floras because
they represent fundamentally different taphonomic
pathways and increased temporal averaging (39)as
well as selective collecting in many cases. The most
comparable leaf assemblage from a caldera lake is
the late Oligocene Creede flora, Colorado, which is
much less diverse than LH (40).
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Paleobiology 26S, 103 (2000).
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76. Supported by the University of Pennsylvania Re-
search Foundation, the Andrew W. Mellon Founda-
tion, the Petroleum Research Fund, the National Geo-
graphic Society, and the Michigan Society of Fellows
(P.W.); the Smithsonian Scholarly Studies Program
(S.L.W.); and the Denver Museum of Nature & Sci-
ence (K.R.J.). We thank P. Dodson and A. Johnson for
expediting funding and P. Puerta, E. Ruigomez, R.
Horwitt, and L. Canessa for field and laboratory as-
sistance. Paleomagnetic analyses took place in the
Paleomagnetic Laboratory of the Scripps Institution
of Oceanography with assistance from L. Tauxe and J.
Gee. R. Burnham, A. Dutton, R. Horwitt, B. Huber, K.
MacLeod, J. Trapani, and four anonymous reviewers
contributed useful critiques; E. Arago´n, K. Bice, R. Hill,
B. Jacobs, D. Greenwood, and R. Squires provided
helpful discussions. We are indebted to the Nahuel-
tripay family for land access.
Supporting Online Material
www.sciencemag.org/cgi/content/full/300/5616/122/
DC1
Materials and Methods
Figs. S1 to S6
Tables S1 to S7
References and Notes
14 November 2002; accepted 11 February 2003
Carotenoid Modulation of
Immune Function and Sexual
Attractiveness in Zebra Finches
Jonathan D. Blount,
1
* Neil B. Metcalfe,
1
Tim R. Birkhead,
2
Peter F. Surai
3
One hypothesis for why females in many animal species frequently prefer to
mate with the most elaborately ornamented males predicts that availability of
carotenoid pigments is a potentially limiting factor for both ornament expres-
sion and immune function. An implicit assumption of this hypothesis is that
males that can afford to produce more elaborate carotenoid-dependent dis-
plays must be healthier individuals with superior immunocompetence. How-
ever, whether variation in circulating carotenoid levels causes variation in both
immune function and sexual attractiveness has not been determined in any
species. In this study, we show that manipulation of dietary carotenoid supply
invokes parallel changes in cell-mediated immune function and sexual attrac-
tiveness in male zebra finches (Taeniopygia guttata).
Females in many animal species frequently
prefer to mate with the most elaborately
ornamented males (1), but how such dis-
plays reveal a males worth is a contentious
issue (2–5). For a signal to honestly reveal
an individuals quality, it must be costly to
produce (6, 7). The expression of many
ornamental traits depends on carotenoids,
red and yellow pigments that animals can-
not synthesize de novo and ultimately must
obtain through their diet (2–5). Carotenoids
are antioxidants and immunostimulants (8,
9), and it has recently been hypothesized
that a trade-off exists in carotenoid alloca-
tion between maintaining health and orna-
mentation: Males in better condition should
require fewer carotenoids for immune func-
tion and could therefore use more of this
resource to enhance ornamental display,
thereby advertising their superior health
(10, 11). However, whether variation in
1
Division of Environmental and Evolutionary Biology,
Institute of Biomedical and Life Sciences, University
of Glasgow, Glasgow G12 8QQ, UK.
2
Department of
Animal and Plant Sciences, University of Sheffield,
Sheffield S10 2TN, UK.
3
Avian Science Research Cen-
tre, Scottish Agricultural College, Auchincruive, Ayr
KA6 5HW, UK.
*To whom correspondence should be addressed. E-
mail: j.blount@bio.gla.ac.uk
R EPORTS
www.sciencemag.org SCIENCE VOL 300 4 APRIL 2003 125
... The taxa described in this paper are based on fossil infructescences collected from five of 32 quarried localities of the Tufolitas Laguna del Hunco, Huitrera Formation, Chubut Province, Patagonia, Argentina, paleolatitude~47°S (Wilf et al., 2003(Wilf et al., , 2005; Figure 1). The Tufolitas Laguna del Hunco are fossiliferous caldera-lake deposits within a volcaniclastic depositional sequence consisting of tuffaceous mudstones to sandstones (Wilf et al., 2003(Wilf et al., , 2005Gosses et al., 2021). ...
... The taxa described in this paper are based on fossil infructescences collected from five of 32 quarried localities of the Tufolitas Laguna del Hunco, Huitrera Formation, Chubut Province, Patagonia, Argentina, paleolatitude~47°S (Wilf et al., 2003(Wilf et al., , 2005; Figure 1). The Tufolitas Laguna del Hunco are fossiliferous caldera-lake deposits within a volcaniclastic depositional sequence consisting of tuffaceous mudstones to sandstones (Wilf et al., 2003(Wilf et al., , 2005Gosses et al., 2021). The fossils of interest here occur throughout the most densely sampled and fossiliferous 60-m interval of the 170-m local stratigraphic section (Wilf et al., 2003(Wilf et al., , 2005Hermsen and Gandolfo, 2016). ...
... The Tufolitas Laguna del Hunco are fossiliferous caldera-lake deposits within a volcaniclastic depositional sequence consisting of tuffaceous mudstones to sandstones (Wilf et al., 2003(Wilf et al., , 2005Gosses et al., 2021). The fossils of interest here occur throughout the most densely sampled and fossiliferous 60-m interval of the 170-m local stratigraphic section (Wilf et al., 2003(Wilf et al., , 2005Hermsen and Gandolfo, 2016). The horizon that yielded the youngest of the fossils (containing localities LH6, LH22, LH25, and LH27) sits 23.05 m above, and in the same paleomagnetic polarity interval as, Ash 2211A, which yielded an 40 Ar-39 Ar age on sanidine of 52.22 ± 0.22 million years (Ma) (early Eocene) (Wilf et al., 2003;Wilf, 2012). ...
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Premise: Two distinct types of fossil infructescences from the early Eocene Laguna del Hunco flora, Chubut Province, Patagonia, Argentina, preserve features of the family Cunoniaceae. The goal of the study is to assess their affinities within Cunoniaceae and to interpret their evolutionary and biogeographical significance. Methods: Specimens were collected from the Tufolitas Laguna del Hunco, Huitrera Formation. They were prepared, photographed, and compared morphologically with similar extant and fossil fruits and infructescences using published literature and herbarium material. Results: The fruit and infructescence morphology place the fossil taxa within Cunoniaceae. They do not conform to any extant genus, supporting the erection of two new fossil genera. Racemofructus gen. nov. shares diagnostic features of the tribe Cunonieae, especially Weinmannia s.l., and exhibits two tribal morphological synapomorphies: a racemose inflorescence and a replum composed of a single column. Cunoniocarpa gen. nov. specimens are paniculate inflorescences with basipetally dehiscent, bicarpellate capsules that have persistent styles and calyces. Its replum morphology suggests possible affinity to the tribe Caldcluvieae, particularly to the genus Ackama. Conclusions: The new Patagonian fossils described herein constitute the oldest record of cunoniaceous capsules globally, supplementing a significant body of fossil evidence from pollen, wood, and reproductive structures from southern South America and Antarctica that suggests that the Cunoniaceae were diversified and widely distributed in the Southern Hemisphere by the early Eocene. Racemofructus and Cunoniocarpa are, respectively, the first fossil records from South America of reproductive structures with affinity to tribes Cunonieae and Caldcluvieae. This article is protected by copyright. All rights reserved.
... BCR flora is among the richest local compression fossil assemblages of any time or place, with a total of 122 morphotypes from the ;400 m 2 of excavated area. This is more species than were found at two sites famous for their diversity: the early Paleocene Castle Rock ''rain forest'' in Colorado (;104 leaf taxa Ellis 2002, Ellis et al. 2003]), and the subtropical early Eocene site at Laguna del Hunco, Argentina (102 leaf taxa [Wilf et al. 2003]). We are not able to correct for differences in sampling effort because the other sites were censused by leaf count rather than line intercept, but all three floras have been intensively sampled by paleobotanical standards, meaning many person-weeks of collecting. ...
... The mean richness of BCR collecting sites (16.6 morphotypes in ;3-4 m 2 ) is also high compared with many fossil compression assemblages representing warm, wet vegetation (e.g., Wing and DiMichele 1995, Wilf et al. 2003). Richness at BCR is not particularly high, however, compared with modern herbaceous wetland vegetation. ...
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... Taken together, our results and the scarce Palaeogene palm fossil record (one taxon) led to rejection of our null hypothesis that Central American understorey palms mostly diversified during the Eocene (Table 1). Recent, late-Miocene radiations in South America have been detected in phylogenies of other taxa (e.g., Kay et al., 2005;Koenen et al., 2015;Richardson et al., 2001), although it is known from the local fossil record that Eocene Amazonian TRFs were even more diverse than extant TRFs (Jaramillo et al., 2006(Jaramillo et al., , 2010Wilf et al., 2003). ...
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Aim: Central America is largely covered by hyperdiverse, yet poorly understood, rain forests. Understorey palms are diverse components of these forests, but little is known about their historical assembly. It is not clear when palms in Central America reached present diversity levels and whether most species arrived from neighbouring regions or evolved locally. We addressed these questions using the most species-rich American palm clades indicative of rain forests. We reconstructed and compared their phylogenomic and biogeographical history with the diversification of 54 other plant lineages, to gain a better understanding of the processes that shaped the assembly of Central American rain forests. Location: Central America. Time period: Cretaceous to present. Major taxa studied: Arecaceae: Arecoideae: Bactridinae, Chamaedoreeae, Geonomateae. Methods: We sampled 218 species through fieldwork and living collections. We se-quenced their genomic DNA using target sequence-capture procedures. Using 12 calibration points, we reconstructed dated phylogenies under three approaches (mul-tispecies coalescent, maximum likelihood and Bayesian inference), conducted biogeo-graphical analyses (dispersal-extinction-cladogenesis) and estimated phylogenetic diversity metrics. Results: Dated phylogenies revealed intense diversification in Central America from 12 Ma. Local diversification events were four times more frequent than dispersal events, and we found strong phylogenetic clustering in relationship to Central America. Main conclusions: Our results suggest that most understorey palm species that characterize the Central American rain forests today evolved locally after repeated This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
... The material is currently species inquirenda and should be revised. (Wilf et al. 2003). Taxon and material: Shelania pascuali was described by Casamiquela (1960) based on a juvenile incomplete specimen (holotype PVL 2186). ...
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... Major contributions to the general collection are briefly listed here for paleobotanists, with additional taxonomic and occurrence references listed in Appendix 1. The fossils come from (1) a suite of latest Cretaceous (late Maastrichtian, Hell Creek Formation) and early Paleocene (early Danian, Fort Union Formation) sites from western North Dakota and South Dakota USA that have been used extensively for studies of the end-Cretaceous extinction (e.g., Johnson et al. 1989;Johnson 2002;Wilf and Johnson 2004); (2) the early Paleocene Salamanca Formation (early Danian) and Las Flores (late Danian) floras of Chubut, Argentina, known for diverse and well-preserved fossil plants and insect-feeding damage following the end-Cretaceous extinction (e.g., Iglesias et al. 2007Iglesias et al. , 2021Clyde et al. 2014;Donovan et al. 2017;Stiles et al. 2020); (3) the early Paleocene (Danian, Fort Union Formation) Mexican Hat site in southeastern Montana, USA, known for diverse insect herbivory traces preserved in its fossil leaves (Wilf et al. 2006;Winkler et al. 2010;Donovan et al. 2014); (4) the middle-late Paleocene (Selandian-Thanetian, Cerrejón Formation) Cerrejón flora from the Guajira Peninsula, Colombia and Bogotá Formation flora of Sabana de Bogotá, central Colombia, together preserving the remains of the oldest known Neotropical rainforests (e.g., Doria et al. 2008;Herrera et al. 2008Herrera et al. , 2019Gómez-Navarro et al. 2009;Wing et al. 2009;Carvalho et al. 2011Carvalho et al. , 2021aCarvalho et al. , 2021b; (5) a suite of sites spanning the late Paleocene (Fort Union Formation) through early Eocene (Wasatch Formation and Little Mountain locality of the Green River Formation) of southwestern and northwestern Wyoming that have been used in many studies of floristic and plant-insect associational responses to climate change (e.g., Gemmill and Johnson 1997;Wilf et al. 1998Wilf et al. , 2006Wilf and Labandeira 1999;Wilf 2000;Donovan et al. 2014); (6) the early Eocene Laguna del Hunco Lagerstätte in Chubut, Argentina (Huitrera Formation), known for its outstanding diversity of fossil plants and animals, varied biogeographic connections, and large number of unique taxon occurrences for South America (e.g., Wilf et al. 2003Wilf et al. , 2013Wilf et al. , 2019Gandolfo et al. 2011); (7) the late early Eocene flora of Republic, Washington (Wolfe and Wehr 1987;DeVore et al. 2005;Greenwood et al. 2016; Klondike Mountain Formation) and the middle Eocene Green River Formation flora (MacGinitie 1969;Smith et al. 2008) of Bonanza, Utah, specifically using images of field-censused collections at DMNH from both sites led by K. Johnson that were used previously for analyses of insect herbivory, fossil-leaf economics, and digital leaf physiognomy (Wilf et al. 2001(Wilf et al. , 2005bCariglino 2007;Royer et al. 2007;Peppe et al. 2011). ...
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Leaves are the most abundant and visible plant organ, both in the modern world and the fossil record. Identifying foliage to the correct plant family based on leaf architecture is a fundamental botanical skill that is also critical for isolated fossil leaves, which often, especially in the Cenozoic, represent extinct genera and species from extant families. Resources focused on leaf identification are remarkably scarce; however, the situation has improved due to the recent proliferation of digitized herbarium material, live-plant identification applications, and online collections of cleared and fossil leaf images. Nevertheless, the need remains for a specialized image dataset for comparative leaf architecture. We address this gap by assembling an open-access database of 30,252 images of vouchered leaf specimens vetted to family level, primarily of angiosperms, including 26,176 images of cleared and x-rayed leaves representing 354 families and 4,076 of fossil leaves from 48 families. The images maintain original resolution, have user-friendly filenames, and are vetted using APG and modern paleobotanical standards. The cleared and x-rayed leaves include the Jack A. Wolfe and Leo J. Hickey contributions to the National Cleared Leaf Collection and a collection of high-resolution scanned x-ray negatives, housed in the Division of Paleobotany, Department of Paleobiology, Smithsonian National Museum of Natural History, Washington D.C.; and the Daniel I. Axelrod Cleared Leaf Collection, housed at the University of California Museum of Paleontology, Berkeley. The fossil images include a sampling of Late Cretaceous to Eocene paleobotanical sites from the Western Hemisphere held at numerous institutions, especially from Florissant Fossil Beds National Monument (late Eocene, Colorado), as well as several other localities from the Late Cretaceous to Eocene of the Western USA and the early Paleogene of Colombia and southern Argentina. The dataset facilitates new research and education opportunities in paleobotany, comparative leaf architecture, systematics, and machine learning. Keywords Angiosperms, cleared leaves, data science, fossil leaves, leaf architecture, paleobotany
... plants, Palazzesi and Barreda, 2007;mammals, Woodburne et al., 2014) or quantitatively (e.g. plants, Wilf et al., 2003;Palazzesi et al., 2014;Ruiz et al., 2021;mammals, Kay et al., 2021). Here we review terrestrial and marine fossil records of selected plants and animals with the aim of providing a more complete picture of how ecosystems responded to the major climatic events of the last 66 Ma. ...
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The early Eocene (56.0 to 47.8 million years ago) was characterized by a series of transient episodes of rapid global warming superimposed on the long-term early Cenozoic warming trend, culminating in the early Eocene Climatic Optimum (EECO; 53.3 to 49.1 million years ago). Details of the hydroclimate regime operating during the EECO are poorly constrained, especially for continental interior sites. The Green River Formation (GRF) of Utah and Colorado was deposited in a suite of large, unusually productive lakes that offer an ideal opportunity to study the hydrological response to warming. Here we report the hydrogen isotopic composition (δ²H) of leaf wax (long-chain n-alkanes) and algal (phytane) lipids preserved in the organic-rich Mahogany Zone (49.3 to 48.7 Ma) and use these data to reconstruct precipitation and lake water δ²H records, respectively. We observe large inter-site variations in algal and leaf wax δ²H values (~50 to 75‰), suggesting that additional local controls influence precipitation and/or lake water δ²H (e.g., salinity). Intriguingly, leaf wax and algal lipid δ²H values show little variation through the Mahogany Zone, implying a relatively stable hydrological regime during the latter phase of the EECO. This contrasts with the more variable hydrological regime that prevailed during early Eocene hyperthermals. Unlike the EECO, the early Eocene hyperthermals in the Uinta region do not coincide with the deposition of organic-rich sediments. This suggests that a stable hydrological regime during the EECO may enable the preservation of organic matter within continental-interior lake systems, potentially leading to an important negative climate feedback during the early Eocene and other greenhouse climates.
Thesis
In this doctoral thesis, I reconstruct continental paleoclimate from the early Cenozoic, when the Earth’s surface experienced a long-term warming trend punctuated by a series of shortlived global warming (hyperthermal) events that culminated in an extended interval of elevated CO2 and extreme warmth, the Early Eocene Climatic Optimum (EECO, 53.26 to 49.14 Ma). The hydrological cycle’s response to climate perturbations is thought to be highly variable, and can promote feedbacks that induce further warming or cooling, thus serving as critical lessons for future warm worlds. However, the response of the hydroclimate regime operating during the EECO is poorly constrained, especially for the mid-to-low latitudes and particularly from continental interior sites. Here, I adopt a multi-proxy approach, integrating geochemical, organic petrographic, and sedimentological perspectives from organic-rich sediments from the Green River Formation of the Uinta Basin, Utah and the Piceance Basin, Colorado, U.S.A., which were deposited in long-lived, large lakes at ~40ºN. I observed a wide range of organic matter types and distribution, with accumulation of organic matter at the lamination scale controlled by longer term sub-orbital cycles suggesting decadal periodicities in large organic-matter fluxes and associated carbon drawdown. Spatial and temporal variations in salinity conditions were the result of long-term tectonic controls driving the water balance between fresher and brinerich inputs into the Uinta Basin, increasing ecological stress on biota living in the water column and leading to the cessation of conditions favouring prodigious organic accumulation in the Mahogany Zone, a regionally extensive marker unit. Lastly, hydrogen isotopes from organic molecules indicate that the hydrological cycle operates differently during gradual vs. transient warming events, and that a stable hydrological regime may have supported deep lake development and promoted organic matter preservation. These organic-rich lake systems acted as an important negative feedback during the termination of the EECO, sequestering at least ~76 Gt of organic carbon over the ~400 kyr history of the Mahogany Zone.
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Mountainous areas host a disproportionately large fraction of Earth's biodiversity, suggesting a causal relationship between mountain building and biological diversification. Mountain clade radiations are generally associated with changes in environment, climate, and the increase in heterogeneity therein during mountain building. However, examining the causal relationship between mountain building and diversification is a complex challenge, because isolating the effects of surface uplift from other abiotic (climate) or biotic variables is not straightforward. In this study, we investigate the relative contributions of abiotic climate-driven (temperature) and geology-driven (elevation) drivers on evolutionary rates of ancient groups of organisms in the South American Andes. We present regional curves of Andean elevation based on a recent compilation of paleo-elevational data back to the Late Cretaceous, and analyse the diversification history of six Andean frog and lizard families that originated equally far back in time. For two clades (Aromobatidae and Leptodactylidae), we find that they diversified most rapidly during the early phase of mountain building (Late Cretaceous - Paleogene), when the first high-elevation habitats emerged in South America. The diversification of one clade (Centrolenidae) is correlated with Cenozoic temperature variations, with higher speciation rates during warm periods. The last three clades (Dendrobatidae, Hemiphractidae and Liolaemidae) are best explained by environment-independent diversification, although for Liolaemidae, an almost equally strong positive correlation was found between speciation and Andean elevation since the late Eocene. Our findings imply that throughout the long-lived history of surface uplift in the Andes, mountain building drove the diversification of different clades at different times, while not directly affecting other clades. Our study illustrates the importance of paleogeographic reconstructions that capture the complexity and heterogeneity of mountain building in our understanding of the effects that a changing environment plays in shaping biodiversity patterns observed today.
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Integrated analysis of the ichnology, sedimentology, geo-chemistry, and fossil content of three trace fossil-bearing calcareous paleosols from the early Eocene Gran Salitral Formation is used to reconstruct the detailed paleoenvironmental and paleoecological setting of this insect-dominated ichnofossil association. This continental sequence, located in southwestern La Pampa province (Argentina), is composed of palustrine marls and minor lacustrine mudstones and sandstones arranged in shallowing-upward cycles. The ichnologic association is the first comprehensively described from a palustrine sequence and could be used for future comparisons with other similar assemblages. The ichnofauna is dominated by bee cells, Celliforma germanica, C. roselli, and Rosellichnus isp.; Teisseirei barattinia, an insect trace fossil that is redescribed and recorded for the first time outside its type locality; Taenidium barretti; and Skolithos linearis. The ichnologic association also includes ovoid structures, ornamented burrow fillings, and plant trace fossils (rootlets, rhizoliths, and a tree / shrub stump). Abundant freshwater (Pomacea sp.) and terrestrial gastropods (Plagiodontes spp., Bostryx sp., and Bulimulus sp.) are used to characterize the paleoenvironmental setting. The weakly developed paleosols are interpreted as Inceptisols, developed in a low-gradient lake margin periodically exposed to pedogenesis with low (probably saline) vegetation and sparse shrubs. They developed under a semi-arid and warm climate (mean annual temperature higher than 20°C). Short saline / alkaline conditions were prevalent during lake lowstands, accompanied by incipient karst development. The association of trace fossils is attributed provisionally to the Coprinisphaera ichnofacies, although its distinctive features and recurrence in time and space may deserve recognition as a separate ichnofacies.
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The three southern conifer families, Araucariaceae, Cupressaceae and Podocarpaceae, have a long history and continue to be an important part of the vegetation today. The Araucariaceae have the most extensive fossil record, occurring in both hemispheres, and with Araucaria in particular having an ancient origin. In the Southern Hemisphere Araucaria and Agathis have substantial macrofossil records, especially in Australasia, and Wollemia probably also has an important macrofossil record. At least one extinct genus of Araucariaceae is present as a macrofossil during the Cenozoic. Cupressaceae macrofossils are difficult to identify in older sediments, but the southern genera begin their record in the Cretaceous (Athrotaxis) and become more diverse and extensive during the Cenozoic. Several extinct genera of Cupressaceae also occur in Cretaceous and Cenozoic sediments in Australasia. The Podocarpaceae probably begin their macrofossil record in the Triassic, although the early history is still uncertain. Occasional Podocarpaceae macrofossils have been recorded in the Northern Hemisphere, but they are essentially a southern family. The Cenozoic macrofossil record of the Podocarpaceae is extensive, especially in south-eastern Australia, where the majority of the extant genera have been recorded. Some extinct genera have also been reported from across high southern latitudes, confirming an extremely diverse and widespread suite of Podocarpaceae during the Cenozoic in the region. In the Southern Hemisphere today conifers achieve greatest abundance in wet forests. Those which compete successfully with broad-leaved angiosperms in warmer forests produce broad, flat photosynthetic shoots. In the Araucariaceae this is achieved by the planation of multiveined leaves into large compound shoots. In the other two families leaves are now limited to a single vein (except Nageia), and to overcome this limitation many genera have resorted to re-orientation of leaves and two-dimensional flattening of shoots. The Podocarpaceae show greatest development of this strategy with 11 of 19 genera producing shoots analogous to compound leaves. The concentration of conifers in wet forest left them vulnerable to the climate change which occurred in the Cenozoic, and decreases in diversity have occurred since the Paleogene in all regions where fossil records are available. Information about the history of the dry forest conifers is extremely limited because of a lack of fossilisation in such environments. The southern conifers, past and present, demonstrate an ability to compete effectively with angiosperms in many habitats and should not be viewed as remnants which are ineffectual against angiosperm competitors.
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