28 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 304 Fig. 20. Distribution records <strong>of</strong> <strong>the</strong> Paramblynotus species occurring in Africa. Species underlined are those without detailed information on collecting locality; <strong>the</strong>refore, <strong>the</strong>y are placed in approximately <strong>the</strong> center <strong>of</strong> <strong>the</strong> country where <strong>the</strong>y were collected. Exact collecting localities for three species from Zaire, that is, P. zairensis (14), P. kekenboschi (16), and P. carianus (18), have not been located. However, judging from <strong>the</strong> altitude records (between 1,800 and 2,300 m), <strong>the</strong>y have certainly been collected from <strong>the</strong> highlands <strong>of</strong> eastern Zaire.
2007 LIU ET AL.: REVISION OF PARAMBLYNOTUS (HYMENOPTERA) 29 migration route, probably existing intermittently during <strong>the</strong> Quaternary or even before, connected East Africa with Angola and <strong>the</strong>n continued to Cameroon (Maley, 1991, and references <strong>the</strong>rein). The montane forest could ei<strong>the</strong>r have formed a more-or-less continuous belt connecting <strong>the</strong> mountains or have formed a series <strong>of</strong> ‘‘stepping stones’’ in a generally more arid environment (Sosef, 1994, and references <strong>the</strong>rein). The distribution <strong>of</strong> Paramblynotus in Africa apparently supports such a scenario. The diversity <strong>of</strong> <strong>the</strong> <strong>genus</strong> Paramblynotus in <strong>the</strong> eastern mountain ranges is probably <strong>the</strong> result <strong>of</strong> topographic diversity and frequent climatic oscillations. The tectonic uplift and tilting <strong>of</strong> major portions <strong>of</strong> <strong>the</strong> continent from <strong>the</strong> early Miocene through <strong>the</strong> Quaternary, especially in eastern and sou<strong>the</strong>rn Africa, created significant topographic diversity. With global change toward decreasing temperature and moisture, this diverse topography apparently had an increased role in moderating continental climates (Potts and Behrensmeyer, 1992). The effect on <strong>the</strong> African biota was <strong>the</strong> fragmentation <strong>of</strong> closed forests and <strong>the</strong> subdivision <strong>of</strong> habitats into complex mosaics <strong>of</strong> moist and dry zones, including forests, woodlands, grasslands, wetlands, and various montane zones (Potts and Behrensmeyer, 1992). The montane forests occupy <strong>the</strong> higher parts <strong>of</strong> <strong>the</strong> mountain ranges and have probably existed in <strong>the</strong> east and sou<strong>the</strong>ast since <strong>the</strong> Paleogene, when mountains in <strong>the</strong> area were sufficiently high and cool to enable certain tropical rainforest taxa to disperse upwards and radiate in <strong>the</strong> temperate montane zone (Axelrod and Raven, 1978). The climate <strong>of</strong> Africa has been characterized by frequent oscillations in terms <strong>of</strong> temperature and moisture since <strong>the</strong> late Miocene, particularly in <strong>the</strong> late Neogene and <strong>the</strong> Quaternary, when glaciations frequently alternated with warmer interglacial periods (Hamilton and Taylor, 1991; Potts and Behrensmeyer, 1992). The climatic oscillations, particularly between <strong>the</strong> glacial and interglacial periods, would have caused <strong>the</strong> montane forest to become restricted to <strong>the</strong> higher mountains during certain periods, causing <strong>the</strong> local populations <strong>of</strong> associated taxa to become extinct at relatively low locations and isolated at higher altitudes. During o<strong>the</strong>r periods, <strong>the</strong>se forests invaded <strong>the</strong> lowlands, facilitating migration between <strong>the</strong> areas. Because <strong>of</strong> <strong>the</strong> local instability <strong>of</strong> <strong>the</strong> montane forest caused by <strong>the</strong> interaction between climatic oscillations and topographical complexity, most <strong>of</strong> <strong>the</strong> current distributions <strong>of</strong> Paramblynotus in Africa are probably ra<strong>the</strong>r recent expansions from a few refugia where montane forest persisted. The lack <strong>of</strong> endemic monophyletic groups in any area strongly supports such a scenario. Refugia for montane forests are found in <strong>the</strong> Cameroon highlands, <strong>the</strong> Tanganyika-Malawi highlands, <strong>the</strong> highlands <strong>of</strong> eastern Zaire, and in nor<strong>the</strong>rn Kenya and nor<strong>the</strong>rn Ethiopia as impoverished islands (Potts and Behrensmeyer, 1992). The basal branch <strong>of</strong> <strong>the</strong> African Paramblynotus (i.e., members <strong>of</strong> <strong>the</strong> former Decellea) is distributed in <strong>the</strong> Cameroon highlands, <strong>the</strong> highlands <strong>of</strong> eastern Zaire, and in Kenya. The highlands <strong>of</strong> eastern Zaire also host <strong>the</strong> greatest diversity <strong>of</strong> <strong>the</strong> group in Africa, comprising one-third <strong>of</strong> <strong>the</strong> known Paramblynotus species on that continent. Apparently, <strong>the</strong> area has served as <strong>the</strong> prime refugium for <strong>the</strong> African Paramblynotus. The major splits in <strong>the</strong> Liopteridae phylogeny can be dated by using <strong>the</strong> historical biogeography reconstruction <strong>of</strong> <strong>the</strong> Mayrellinae presented above and data from Ronquist (1995a) (fig. 21). Ronquist (1995a) observed that <strong>the</strong> historical biogeography <strong>of</strong> <strong>the</strong> Liopteridae corresponds fairly closely to <strong>the</strong> breakup <strong>of</strong> <strong>the</strong> Pangaea during <strong>the</strong> Mesozoic as inferred from geological data, and he dated all o<strong>the</strong>r major divergent events within <strong>the</strong> family except <strong>the</strong> split between <strong>the</strong> Mayrellinae and <strong>the</strong> o<strong>the</strong>r subfamilies. The divergence between Paramblynotus and Kiefferiella has probably been caused, as discussed above, by <strong>the</strong> formation <strong>of</strong> <strong>the</strong> Rocky Mountains in <strong>the</strong> latest Paleocene and early Eocene (ca. 56–40 Ma), which created a dispersal barrier between southwestern North America and <strong>the</strong> rest <strong>of</strong> <strong>the</strong> continuous Asiamerican landmass. As for <strong>the</strong> more basal events within <strong>the</strong> Liopteridae, <strong>the</strong> Mayrellinae, as discussed above, most probably originated in Laurasia, and its sister clade, consisting <strong>of</strong> <strong>the</strong> o<strong>the</strong>r subfamilies, apparently originated in Gondwana (Ronquist,