Age and historical biogeography of the pantropically distributed Spathelioideae (Rutaceae, Sapindales)

Abstract

Aim The family Rutaceae (rue family) is the largest within the eudicot order Sapindales and is distributed mainly in the tropical and subtropical regions of both the New World and the Old World, with a few genera in temperate zones. The main objective of this study is to present molecular dating and biogeographical analyses of the subfamily Spathelioideae, the earliest branching clade (which includes eight extant genera), to interpret the temporal and spatial origins of this group, ascertaining possible vicariant patterns and dispersal routes and inferring diversification rates through time. Location Pantropics. Methods A dataset comprising a complete taxon sampling at generic level (83.3% at species level) of Spathelioideae was used for a Bayesian molecular dating analysis (beast). Four fossil calibration points and an age constraint for Sapindales were applied. An ancestral area reconstruction analysis utilizing the dispersal–extinction–cladogenesis model and diversification rate analyses was conducted. Results Dating analyses indicate that Rutaceae and Spathelioideae are probably of Late Cretaceous origin, after which Spathelioideae split into a Neotropical and a Palaeotropical lineage. The Palaeotropical taxa have their origin inferred in Africa, with postulated dispersal events to the Mediterranean, the Canary Islands, Madagascar and Southeast Asia. The lineages within Spathelioideae evolved at a relatively constant diversification rate. However, abrupt changes in diversification rates are inferred from the beginning of the Miocene and during the Pliocene/Pleistocene. Main conclusions The geographical origin of Spathelioideae probably lies in Africa. The existence of a Neotropical lineage may be the result of a dispersal event at a time in the Late Cretaceous when South America and Africa were still quite close to each other (assuming that our age estimates are close to the actual ages), or by Gondwanan vicariance (assuming that our age estimates provide minimal ages only). Separation of land masses caused by sea level changes during the Pliocene and Pleistocene may have been triggers for speciation in the Caribbean genus Spathelia.

Major Clades of Australasian Rutoideae (Rutaceae) Based on rbcL and atpB Sequences

“…Although our estimated divergence dates (Table 2) align with those from other studies [23], [24], including a recent study of Rutaceae subf. Spathelioideae [88] also based on Bayesian methods, they differ markedly from much younger divergences estimated for Rutaceae subf. Aurantioideae [17] based on non-parametric rate smoothing [89] and a different range of fossil calibrations (all outside Rutaceae).…”

Phylogenetic and Ecological Signals in the Wood of Spathelioideae (Rutaceae)

“…This lack might be explained by the less-seasonal climate of the Canary Islands as compared to the Mediterranean (Juan et al 2000). We hypothesize that Cneorum has a tropical African ancestor (see also ancestral area reconstruction in Appelhans et al 2012) and lacked dendritic vessel patterns, and that C. tricoccon evolved its Mediterranean xylem adaptations upon arrival in Europe after the split from C. pulverulentum.…”

“…Features such as vessel diameter, vessel frequency, and vessel grouping affect the hydraulic efficiency and safety of a tree and shrub in its habitat, in interaction with temperature, drought, and seasonality (Carlquist 1984;Hacke & Sperry 2001;Hacke et al 2006;Lens et al 2011). The ecology of most Spathelioideae is only rather sketchily known (Appelhans et al 2011(Appelhans et al , 2012; almost all grow in dry to mesic vegetation in the tropics. The only exception is Cneorum of which C. tricoccon is chiefly Mediterranean, occurring from Southern Italy towards the Western Mediterranean, while C. pulverulentum grows in the dry parts of the subtropical Canary Islands.…”

Melicope oppenheimeri, section Pelea (Rutaceae), a new species from West Maui, Hawaiian Islands: with notes on its ecology, conservation, and phylogenetic placement

“…Hartley (2001) inferred that Melicope was present in eastern Gondwanaland before about 96 Ma and states that the Hawaiian species represent a radiation that most likely traces back to a single colonization of the archipelago by a species from sect. Pelea. While Hartley’s age estimate of Melicope is doubtful since the oldest fossils of the whole family date to the Late Cretaceous (Knobloch and Mai 1986, Gregor 1989) and molecular dating studies estimated its origin in the Oligocene or Miocene (Muellner et al 2007, Appelhans et al 2012), his suggestion for a single colonization of the Hawaiian archipelago was supported by molecular phylogenetic analyses (Harbaugh et al 2009, Appelhans et al 2014b, c). The most recent molecular phylogenetic studies also indicate that the Hawaiian genus Platydesma H. Mann is nested within Melicope sect. Pelea and that the seven known Marquesan Melicope endemics are a closely related group resultant from two independent colonization events from Hawaiian Melicope (Harbaugh et al 2009, Appelhans et al 2014c).…”