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

Abstract

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 continentwide 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 (Mya) 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 to 9 Mya during the 'Hill Gap' and accelerated from ~4 Mya 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.

Historical and future climate change fosters expansion of Australian harvester termites, Drepanotermes

“…This is consistent with the position of Drepanotermes as a crown group within Australian Amitermes (Heimburger et al. 2022), which are primarily soil dwellers (Gay 1968, Gay and Calaby 1970). Many early‐branching lineages are subterranean and occur near the northwest cap in western Australia, the likely origin of the genus (Watson and Perry 1981, Heimburger et al.…”

“…Relationships within Drepanotermes showed lower nodal support values, consistent with the rapid diversification over the past five million years (see below and Heimburger et al. 2022).…”

“…Similarly, Drepanotermes radiated in concert with the formation and diversification of arid habitats from the Pliocene onward (Heimburger et al. 2022). This study, covering the most Drepanotermes taxa to date, shows considerable species divergence in the past 1 million years ago.…”

“…We used the best partitioning scheme of ASAP (based on the lowest asap-score of 5.50) to divide the data set into 54 mOTUs and then selected representative sequences for each to use in downstream phylogenetic inference and divergence dating. To make our phylogenetic reconstructions as robust as possible, we selected representative mOTU sequences for which whole mitochondrial genome sequences were available from the same colony (Heimburger et al 2022) or individuals for which at least two of the three targeted genes had been sequenced. Thus, our supermatrix alignment consisted of mitochondrial coding sequences (CDS), COX2 mtDNA, and ITS1 and ITS2 nDNA sequences (Heimburger et al 2022).…”

“…2011), including the endemic termite genus Drepanotermes Silvestri, which is a prime example of explosive radiation coinciding with intensifying arid conditions in the Plio‐Pleistocene (Heimburger et al. 2022). The 23 described species primarily occur in arid and semiarid regions of the continent (Watson and Perry 1981).…”