Fruits and foliage of Pueraria (Leguminosae, Papilionoideae) from the Neogene of Eurasia and their biogeographic implications

Abstract

Pueraria (Leguminosae, Papilionoideae) is native in East Asia, South Asia, Southeast Asia, and Oceania and is well known as a rampant invasive weed in the southeastern United States (P. montana; better known as kudzu), but relatively little is known about its early evolution and biogeographic origin. • On the basis of comparative analyses of the fruit and leaflet architecture of closely related extant and fossil taxa, we studied the fossil history and biogeography of Pueraria. • Fossil Pueraria is recognized on the basis of distinctive fruit and foliage from the Mio-Pliocene of middle latitudes in China, Japan, Abkhazia, and Croatia. Recognition of P. miothunbergiana from the Mio-Pliocene of China and Japan is reinforced by a trifoliolate leaf as well as isolated lateral and terminal leaflets. Pueraria shanwangensis sp. nov. represents the first recognition of fossil Pueraria fruits. This fruit species co-occurs with P. miothunbergiana in the Middle Miocene Shanwang flora and possibly represents the same population. Pueraria maxima (Unger) comb. nov., previously named as Dolichites maximus or Desmodium maximum, is recognized on the basis of leaflets from the Miocene of Croatia and Abkhazia. Other prior fossil reports of Pueraria and Dolichites are reevaluated. • Pueraria had begun to diversify by at least the Middle Miocene and had spread into the Mio-Pliocene subtropical and temperate floras of the Balkan Peninsula, the Caucasus, and eastern Asia, which suggests the present diversity of this genus in tropical Asia and Oceania might have originated from the mid-latitudes of Eurasia.