Rapid diversification of the Australian Amitermes group during late Cenozoic climate change

Late Cenozoic climate change led to the progressive aridification of
Australia over the past 15 million years. This gradual biome turnover
fundamentally changed Australia’s ecosystems, opening new niches and
prompting diversification of plants and animals. One example are termites
of the Australian Amitermes Group (AAG), consisting of the Australian
Amitermes and affiliated genera. Although the most speciose and diverse
higher termite group in Australia, little is known about its evolutionary
history. We used ancestral range reconstruction and diversification
analyses to illuminate (1) phylogenetic relationships of the AAG, (2)
biogeographical processes leading to the current continent-wide
distribution, and (3) timing and pattern of diversification in the context
of late Cenozoic climate change. By estimating the largest time-calibrated
phylogeny for this group to date, we demonstrate monophyly of the AAG and
confirm that their ancestor arrived in Australia ~11-10 million years ago
from Southeast Asia. Ancestral range reconstruction indicates that
Australia’s monsoon region was the launching point for a continental
radiation shaped by dispersal and within-biome speciation rather than
vicariance. We found that multiple arid-zone species diversified from
mesic and tropical ancestors in the Plio-Pleistocene, but also observed
diversification in the opposite direction. Finally, we show that
diversification steadily increased from ~8-9 Ma during the “Hill Gap” and
accelerated from ~4 Ma in concert with major ecological change during the
Pliocene. Consistent with rapid diversification, species accumulation then
slowed down into the present, likely caused by progressive niche
saturation. This study provides a stepping stone for predicting future
responses of Australia's termite fauna in the face of human-mediated
climate change.