Oldest known ant fossils discovered.

1 Pages·1998·0.73 MB·English

by  Agosti, D.

' .
known
Oldest
ant discovered
fossils
we
ere report fossil ants, including a abdominal and
segrnents, the apical denticles
new
genus of Ponerinae, about 50 mil- on
* the genae, 'indicate a relationship with
lion years (Myr) older than the previous old-
ants of the pdhefine tribe Amblyoponini.
t
specimens. These amber
est discoveries in Addition of these two new taxa confirms
.
from the Turonian stage (92 Myr ago) of
the basal position of Sphecomyrma^, but
as
New
Jersey in the United States have impor- part of a quadritomy. The position of the
tant implications for estimates dating the new
ponerine within one clade of the Poner-
origin of ants, and extend the age of an
inae demonstrates one major
that lineage of
extant ant subfamily back about 50 Myr.
extant ants was estabHshed well before the
Until now, a specimen of Sphecomyrma formation of amber 'from S^dialin Island
in a piece of amber from ClifRvobd ^_ J _ ' r
freyi (probably Palaeocene)^ and of Eocene
Baltic
New
Beach,. Jersey, was one of the, few non- amber which are about 50 Myr younger
,
compression from
fossil ants the Cretaceous than the Ne\v Jersey amUer,,
,
period showing most morphologicardetails\ A
reasonable estimate would thus place
The metapleural gland the only morpho-
is the origin of the ants into the lowermost
logical trait unique within the Hymenoptera Myr
Cretaceous (about 130 ago), but proba-
that distinguishes ants, and can be seen in no
bly older. This conclusion consistent
is
most embedded
ants in amber. This gland
with the relationship of the Formicidae
to
produces
antibiotic-like substances^, neces- . the wasp families Vespidae and
Scoliidae^
sary to maintain nests underground 6f in and
the phylogenetic position of the Creta-
humid
pieces of wood, where bacteria and On
ceous Vespidae^^. this basis, a hypothesis
-,
r
fungi would otherwise invade immobile
of a Lower Jurassic origin of ants^\. based on
broods. The gland is seen in modern species, estimated divergence time of mitochondrial
opening above the hind coxae. Development
cytochrome
h sequences,
unlikely.
is
of the gland and eusociality were probably
Although
ants originated in the Creta-
and
correlated are involved in the great eco- ceous, it was not until the Tertiary^ period
logical success of the ants. In an Amazonian that they became so dominant and
diverse in
rainforest, for example, ants make up more
terrestrial ecosystems, as documented in
25%
than of the total animal biomass^. and Dominican amber^l We
Baltic^ are
still
aV
Wilson
et described an almost per- examining why
the radiations were delayed
'-W'-r^-rtf-Tc-^-4-r,-^^iutn^u,^c^tnynnifiai=jtis^apT^r^^7zWf^
fecdy preserved worker of but the r New
S. freyi, Figure 1 Photomicrographs of Jersey ant until the Tertiary.
,
debate remained whether this fossil is an ant fossils, a, Alitrunk and portion of the gaster of Donat Agosti, David Grimaldi,
because the presence of the metapleural new
the S. frey/ worker with a drawing showing James M. Carpenter
gland was uncertain. Sphecomyrma was thus the position and structure of metapleural Department Entomology, American Museum
its of of
excluded from a recent phylogenetic analysis gland (IVIGO). b, Lateral view of the new Creta- Natural History Central Park West at 79th
Street,
of the Formicidae*, and its relatively short ceous ponerine genus (m, mandible in frontal New York, New York 10024-5192, USA
first antennal segment in workers was A
view), detailed description will be provided e-mail: [email protected]
assumed
to prevent the basic social behav- elsewhere^ (http://research.amnh.org/entomol-
&
iour of trophallaxis^ ogy/socialjnsects). 1. Wilson, E. O., Carpenter, F. M. Brown, W. L. Jr. Psyche 74, 1-19
(1967).
Our new
specimens include three worker
&
2. Beattie, A. Turnbull, C. L., Hough, T. Knox, R. B. Ann.
J.,
and four male ants. One complete, well- third male belongs to a genus as yet undeter-^ Entomol Soc. Am. 79, 448-450.
preserved worker was the second discovery mined. The fourth male tentatively 3. Fittkau,E.J. &KIinge,H.Biofrop(ca5,2-14(I973).
is
&
of S. freyi. Among other well-preserved traits assigned to Sphecomyrma and would be the 4. Baroni Urbani, C, Bolton, B. Ward, P. S. Syst. Entomol. 17,
301-329(1992).
specimen and known
in this are the external even male
first of that genus.
Dlussky, G.M.Pa/eonfJ. 1983 65-78
5. (3), (1983). "!i
.
part of the internal anatomy of the meta- Another worker new
represents a genus, 6. Grimaldi, D. et at. J.M. Am. Mus. Novit. (in the press).
pleural gland. The gland has a circular open- distinguished by clubbed antennae, pro- 7. Dhissky, G. M. Paleont. 1988 (1), 50-61 (1988).
its J.
ing and a very large subcuticular atrium (Fig. portions of the antennal articles, thin man- 8. Wheeler, W. M. Schr. Phys.-Okon. Ges.Konigsh. 55, 1-142 (1915).
&
Sphecomyrma 9. Brothers, D. J. Carpenter, J. M. /. Hymenopt. Res. 2, 227-304
la). is thus an ant. dibles that lack teeth and cross extensively
(1993).
Two
of the males are a new species of the when closed, and a girdling constriction of 10. Carpenter, M. Sc Rasnitsyn, A. R Psyche 97, 1-20 (1990).
J.
Cretaceous genus Baikuris, known previous- the gaster typical of the large modern sub- 1 1 Crozier, R., Jermitn, L. S. & Chiotis, M. Naturwissenschaften 84,
22-23
(1997).
ly only troxa Upper Cretaceous (Santonian) family, the Ponerinae Furthermore, .
(Fig. lb).
&
12. Holldobler, B. WUson, E. O. The Ants (Harvard Univ. Press,
amber from
Taymyr, northern Siberia. The''"^ the broad attachment of the third and fourth
Boston, 1990).
s^>;M^wi^<y??^J
Climate change and tionship where a 1 °C fall in diurnal temper- tributed litde. In our view, Nicholls's results
ature range increased Australian wheat yield need qualification and should be interpreted
Australian wheat by 0.52 t ha~\ This efr'ect, taken with the with caution. They are only estimates, and
yield
trend in diurnal range, accounted for 45% of do not include standard
errors to indicate
the yield increase between 1952 and 1992. In their precision.
30-50%
Nicholls^ reported that of the an extended model with three climate vari- The analytical challenge to separate the
is
increase in AustraHan wheat yields in the ables, Nicholls found that changes in mini- effects of climate change from other factors
mum
period 1952-92 from
resulted climate temperature had had most impact on
affecting Australian wheat Non-
yields.
He
change. estimated a simple linear rela- wheat yield and that rainfall change had con- climate factors include total wheat area, the
n
I
NATURE VOL
JANUARY
391 29 1997 447