Evidence of taxon cycles in an Indo-Pacific passerine bird radiation (Aves: Pachycephala )

Abstract

Many insular taxa possess extraordinary abilities to disperse but may differ in their abilities to diversify and compete. While some taxa are widespread across archipelagos, others have disjunct (relictual) populations. These types of taxa, exemplified in the literature by selections of unrelated taxa, have been interpreted as representing a continuum of expansions and contractions (i.e. taxon cycles). Here, we use molecular data of 35 out of 40 species of the avian genus Pachycephala (including 54 out of 66 taxa in Pachycephala pectoralis (sensu lato), to assess the spatio-temporal evolution of the group. We also include data on species distributions, morphology, habitat and elevational ranges to test a number of predictions associated with the taxon-cycle hypothesis. We demonstrate that relictual species persist on the largest and highest islands across the Indo-Pacific, whereas recent archipelago expansions resulted in colonization of all islands in a region. For co-occurring island taxa, the earliest colonists generally inhabit the interior and highest parts of an island, with little spatial overlap with later colonists. Collectively, our data support the idea that taxa continuously pass through phases of expansions and contractions (i.e. taxon cycles).

Phylogeography of a ‘great speciator’ (Aves:Edolisoma tenuirostre) reveals complex dispersal and diversification dynamics across the Indo‐Pacific

“…Such evolutionary cycles of shifting range and dispersal ability have been inferred in various island taxa (e.g. Jønsson et al., , ; Ricklefs & Cox, ; Wilson, ). Here, we draw on patterns of elevational distribution, dispersal ability and species age of Edolisoma taxa to discuss the diversification dynamics of this radiation in the context of taxon cycles.…”

“…The E. tenuirostre complex ranges east of Wallace's line into the Near‐Pacific, with migratory and sedentary populations of E. t. tenuirostre occurring almost along the entire Australian north and east coast (Taylor, ; Figure ). Few molecular studies have explored intraspecific patterns of diversification with a dense sampling across the range of a great speciator (but see Garcia‐Ramirez & Trewick, ; Garcia‐Ramirez et al., ; Irestedt et al., ; Jønsson et al., ; Moyle et al., ). In this study, we initially reconstruct phylogenetic relationships and colonization history of the genus Edolisoma and in particular the hyperdiverse E. tenuirostre subspecies complex.…”

Mixed patterns of morphological adaptation to insularity in an aerial displaying bird, the Common Snipe Gallinago gallinago

“…Recent colonizers tend to occupy all islands of an archipelago, whereas the lineages of the earliest colonists persist on the larger islands, after going through phases of expansions and contractions (Jønsson et al . ), which seem to occur coupled with changes in dispersal ability (Kennedy et al . ).…”

Determinants of bird species richness, endemism, and island network roles in Wallacea and the West Indies: is geography sufficient or does current and historical climate matter?

“…In Wallacea this may be attributable to islands in the center, currently and for millions of years, being drier and climatically more unstable than those at the western and southern fringe (Hall et al 2011; Appendix S2). Additionally, the region has a highly complex geological history, and linked complex species dispersal histories and intra-archipelago species-pumps (Jønsson et al 2012, 2014), which may potentially obscuring any simple measure of isolation. For instance, the southern Moluccas are geologically linked with New Guineas Vogelkop peninsula (Hall 2002), and the large and geologically highly complex island of Sulawesi in the north-western fringe of Wallacea has high in situ speciation (Lohman et al 2011) and could therefore have served as an intra-archipelago species-pump for the surrounding islands.…”