Unveiling the Diversification Dynamics of Australasian Predaceous Diving Beetles in the Cenozoic

Abstract

During the Cenozoic, Australia experienced major climatic shifts that have had dramatic ecological consequences for the modern biota. Mesic tropical ecosystems were progressively restricted to the coasts and replaced by arid-adapted floral and faunal communities. Whilst the role of aridification has been investigated in a wide range of terrestrial lineages, the response of freshwater clades remains poorly investigated. To gain insights into the diversification processes underlying a freshwater radiation, we studied the evolutionary history of the Australasian predaceous diving beetles of the tribe Hydroporini (147 described species). We used an integrative approach including the latest methods in phylogenetics, divergence time estimation, ancestral character state reconstruction, and likelihood-based methods of diversification rate estimation. Phylogenies and dating analyses were reconstructed with molecular data from seven genes (mitochondrial and nuclear) for 117 species (plus 12 outgroups). Robust and well-resolved phylogenies indicate a late Oligocene origin of Australasian Hydroporini. Biogeographic analyses suggest an origin in the East Coast region of Australia, and a dynamic biogeographic scenario implying dispersal events. The group successfully colonized the tropical coastal regions carved by a rampant desertification, and also colonized groundwater ecosystems in Central Australia. Diversification rate analyses suggest that the ongoing aridification of Australia initiated in the Miocene contributed to a major wave of extinctions since the late Pliocene probably attributable to an increasing aridity, range contractions and seasonally disruptions resulting from Quaternary climatic changes. When comparing subterranean and epigean genera, our results show that contrasting mechanisms drove their diversification and therefore current diversity pattern. The Australasian Hydroporini radiation reflects a combination of processes that promoted both diversification, resulting from new ecological opportunities driven by initial aridification, and a subsequent loss of mesic adapted diversity due to increasing aridity.

Evolution of Pacific Rim diving beetles sheds light on Amphi‐Pacific biogeography

“…The biogeographic history of the Neotropical clades of Platynectini might therefore represent a mix of an ancient Gondwanan widespread distribution shaped by periods of extinction throughout the Cenozoic and a more recent mid‐Cenozoic LDD event. Extinction in the Australian region has already been documented (Toussaint et al ) illustrating the impact of recent climatic changes on diversity assemblages in the region.…”

“…has already been documented (Toussaint et al 2015a) illustrating the impact of recent climatic changes on diversity assemblages in the region.…”

To what extent do new fossil discoveries change our understanding of clade evolution? A cautionary tale from burying beetles (Coleoptera:Nicrophorus)

“…Said that, We also share Beaulieu & O'Meara ()'s view that we should remain prudent about estimating extinction from molecular phylogenies. Interestingly, our results are not isolated since other phylogenetic studies have evidenced extinction periods in insect clades (Condamine & Hines, ; Toussaint et al ., ).…”

“…In contrast, the second set of calibrations implies a colonization during the early Miocene when both the Sunda and Sahul regions collided (Seton et al, 2012). This geological rearrangement resulted in a massive orogeny in Wallacea (Hall, 2012(Hall, , 2013 and Melanesia responsible for the exchange of biotas between the Oriental and Australian regions (T€ anzler et al, 2014;Toussaint et al, 2014;. Hence, these contrasting results imply either a climatic or a geological factor to explain the biogeographic history of Nicrophorus in Southeast Asia.…”

Phylogenetic placement of the Pacific Northwest subterranean endemic diving beetle Stygoporus oregonensis Larson & LaBonte (Dytiscidae, Hydroporinae)

“…Addressing the mechanisms responsible for the unusual though oft-repeated appearance of the stygobitic fauna and their often unexpected distributions is an active field (Juan et al 2010). Cave faunas are some of the most visually striking examples of convergence, and several recent studies of stygobitic and troglobitic life have used the character-rich information present in molecular sequence data to help place these morphologically similar species into phylogenetic hypotheses (Faille et al 2010; Gómez et al 2016; Leys et al 2003; Miller et al 2013; Ribera et al 2010; Toussaint et al 2015; Wiens et al 2003). …”