Mosaic patterns of diversification dynamics following the colonization of Melanesian islands

Abstract

The fate of newly settled dispersers on freshly colonized oceanic islands is a central theme of island biogeography. The emergence of increasingly sophisticated methods of macroevolutionary pattern inference paves the way for a deeper understanding of the mechanisms governing these diversification patterns on lineages following their colonization of oceanic islands. Here we infer a comprehensive molecular phylogeny for Melanesian Exocelina diving beetles. Recent methods in historical biogeography and diversification rate inference were then used to investigate the evolution of these insects in space and time. An Australian origin in the mid-Miocene was followed by independent colonization events towards New Guinea and New Caledonia in the late Miocene. One colonization of New Guinea led to a large radiation of >150 species and 3 independent colonizations of New Caledonia gave rise to about 40 species. The comparably late colonizations of Vanuatu, Hawaii and China left only one or two species in each region. The contrasting diversification trajectories of these insects on Melanesian islands are likely accounted for by island size, age and availability of ecological opportunities during the colonization stage.

Stream flow alone does not predict population structure of diving beetles across complex tropical landscapes

“…Following the habitat constraints hypotheses (Ribera, ), one can predict that New Guinean lotic lineages should exhibit high levels of local endemism and population structure between watersheds and geological terranes on the island because of low dispersal in stable environments. Such a pattern has been previously suggested by several studies involving large time‐calibrated molecular phylogenies, including lotic Exocelina diving beetles (Toussaint, Hendrich, Shaverdo, & Balke, ; Toussaint et al., ), rainbowfishes (Unmack et al., ) and the New Guinea snapping turtle Elseya novaeguineae (Georges et al., ). However, there are no studies to date that focus on fine‐scale phylogeographic patterns among populations of aquatic lineages across the island (but see Lam et al., ; Georges et al., for Miocenic divergence of regional populations).…”

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

“…In clade CVI, New Guinea was colonized out‐of‐Australia, in the mid‐Miocene, which agrees with the proposed onset of more significant formation of land and altitude in the region of present day New Guinea (Hall ,, , synopsis in Toussaint et al ). Toussaint et al (, ) also found a similar pattern in Exocelina diving beetles (Copelatinae) suggesting this was a time when large‐scale environmental change initiated major clade formation and species‐level diversification in New Guinea.…”

Historical biogeography of Polyura butterflies in the oriental Palaeotropics: trans‐archipelagic routes and South Pacific island hopping

“…More sophisticated phylogenetic methods and molecular clock divergence time estimation have greatly improved our understanding of the biogeography of several taxa (Lohman et al ., ; de Bruyn et al ., ). In particular, the study of evolutionary patterns and processes in insect clades of the IAA has recently experienced remarkable progress (Braby & Pierce, ; Balke et al ., ; Müller & Beheregaray, ; Müller et al ., , ; Condamine et al ., , ; Toussaint et al ., , , ,c,d; Tänzler et al ., , ; Clouse et al ., ). Most of the clades studied are widespread in the IAA and therefore provide a window into the impact of geological and climatic factors on lineage diversification.…”