Myrmicine ants (Hymenoptera: Formicidae) in Miocene amber of Zhangpu, China
Abstract
The middle Miocene (Langhian) Fotan Group of Zhangpu County
(Fujian Province, SE China) contains a rich paleoflora including
leaves and fruits of dipterocarp trees, reflecting a northern expansion
of tropical dipterocarp forests during the mid-Miocene Climatic
Optimum. A highly fossiliferous amber of dipterocarp origin also occurs,
containing a remarkable ant fauna with more than 1 000 individuals
from 9 subfamilies found to date. Myrmicinae are prevalent (65% of
the total ants), followed by Dolichoderinae (9%), Ponerinae (8%), and
Formicinae (6%). Myrmicines comprise more than 30 extinct species
distributed in 17 extant genera, among which Carebara and Pheidole
are largely dominant (33% and 28%, respectively). Lophomyrmex,
Crematogaster, and Tetramorium are also well represented (ca 7%
each), and several occurrences are the first fossil records of extant
genera (e.g., Cardiocondyla, Gauromyrmex, Lordomyrma, Meranoplus,
Proatta). The specific richness is rather high within most genera, with
distinct morphological features reflecting various ecological lifestyles
from hypogaeic to arboreal species and supporting the hypothesis of
a well-developed mature forest. Some specimens are also fossilized in
behavioral position, just as their living relatives, notably the typical
repelling posture of the “acrobat ants” Crematogaster with the sting
overcoming the mesosoma and suggesting that the ecological behavior
is highly conservative through time. Then, the presence of Yunodorylus
(Dorylinae) in colonies of Pheidole would suggest a possible association
of these genera nesting in soils, which has not been observed among
the current species. Overall, the ant fauna of Zhangpu amber is mostly
similar to the present-day fauna that is found in tropical rainforests
from SE Asia and eastern Australia, particularly the dipterocarp forests
of Borneo, Philippines or Malaysia. Our findings highlight a closely
related geographical distribution of some Australasian ant genera and
dipterocarp forest ecosystems