Oligocene Termite Nests with In Situ Fungus Gardens from the Rukwa Rift Basin, Tanzania, Support a Paleogene African Origin for Insect Agriculture

Abstract

Based on molecular dating, the origin of insect agriculture is hypothesized to have taken place independently in three clades of fungus-farming insects: the termites, ants or ambrosia beetles during the Paleogene (66–24 Ma). Yet, definitive fossil evidence of fungus-growing behavior has been elusive, with no unequivocal records prior to the late Miocene (7–10 Ma). Here we report fossil evidence of insect agriculture in the form of fossil fungus gardens, preserved within 25 Ma termite nests from southwestern Tanzania. Using these well-dated fossil fungus gardens, we have recalibrated molecular divergence estimates for the origins of termite agriculture to around 31 Ma, lending support to hypotheses suggesting an African Paleogene origin for termite-fungus symbiosis; perhaps coinciding with rift initiation and changes in the African landscape.

Know your farmer: Ancient origins and multiple independent domestications of ambrosia beetle fungal cultivars

“…The evolution of agriculture has resulted in colony sizes numbering in the millions for leaf‐cutter ants, making them the dominant herbivore in the New World Tropics (Holldobler & Wilson, ). Insect fungiculture also evolved with a single origin 40–25 Ma (Roberts et al., ) in the Macrotermitinae termites, which subsequently diversified and spread through Africa and Asia (Mueller & Gerardo, ; Aanen & Boomsma, ). The third insect–fungal agricultural symbiosis is between ambrosia beetles of the weevil family Curculionidae and (primarily) “Ophiostomatoid” fungi of the orders Ophiostomatales and Microascales.…”

Diversity of fungus‐growing termites (Macrotermes) and their fungal symbionts (Termitomyces) in the semiarid Tsavo Ecosystem, Kenya

“…, Roberts et al . ). Since then, the fungus‐growing Macrotermitinae have radiated into 11 genera with ca 330 described species (Kambhampati & Eggleton , Aanen et al .…”

Morphological diversification of ampullariid gastropods (Nsungwe Formation, Late Oligocene, Rukwa Rift Basin, Tanzania) is coincident with onset of East African rifting

“…, , , ; Roberts et al . , ; Blackburn et al . ) and the ampullariid fauna allows further exploration of palaeoenvironmental conditions during deposition in the Nsungwe Formation of the Rukwa Rift Basin.…”

“…Radiotopic dating of volcanic tuffs, palaeomagnetic investigations and biostratigraphy all indicate that the Songwe Member is late Oligocene in age with the timing of deposition constrained to between 26 and 24 million years ago (Roberts et al . , ; Stevens et al . ).…”

“…Abundant trace fossils, including fungus‐farming termite nests, are found in this facies, yet body fossils are rare and are dominated by dense accumulations of gastropods with few microvertebrate elements (Roberts et al . , ). FA5 is interpreted as representing subaqueous deposition in floodbasin lakes and wetlands which consist of numerous ecosystems including low‐energy lake bottom, delta‐marsh and a marginal sandy delta and shoreline regions.…”