Givnish T J, Evans T M, Zjhra M L, Patterson T B, Berry P E, Sytsma K J
Department of Botany, University of Wisconsin, Madison 53706, USA.
Evolution. 2000 Dec;54(6):1915-37. doi: 10.1111/j.0014-3820.2000.tb01237.x.
Rapateaceae (16 genera, approximately 100 species) is largely restricted to the tepuis and sandplains of the Guayana Shield in northern South America, with Maschalocephalus endemic to West Africa. The family has undergone extensive radiation in flower form, leaf shape, habit, and habitat. To analyze the evolution of these distributions and traits, we derived a molecular phylogeny for representatives of 14 genera, based on sequence variation in the chloroplast-encoded ndhF gene. The lowland subfamily Rapateoideae is paraphyletic and includes the largely montane subfamily Saxofridericioideae as a monophyletic subset. Overall, the morphological/anatomical data differ significantly from ndhF sequences in phylogenetic structure, but show a high degree of concordance with the molecular tree in three of four tribes. Branch lengths are consistent with the operation of a molecular clock. Maschalocephalus diverges only slightly from other Monotremae: it is the product of relatively recent, long-distance dispersal, not continental drift--only its habitat atop rifted, nutrient-poor sandstones is vicariant. The family appears to have originated approximately 65 Mya in inundated lowlands of the Guayana Shield, followed by: (1) wide geographic spread of lowland taxa along riverine corridors; (2) colonization of Amazonian white-sand savannas in the western Shield; (3) invasion of tepui habitats with frequent speciation, evolution of narrow endemism, and origin of hummingbird pollination in the western Shield; and (4) reinvasion of lowland white-sand savannas. The apparent timing of speciation in the Stegolepis alliance about 6-12 Mya occurred long after the tepuis began to be dissected from each other as the Atlantic rifted approximately 90 Mya. Given the narrow distributions of most montane taxa, this suggests that infrequent long-distance dispersal combined with vicariance accounts for speciation atop tepuis in the Stegolepis alliance.
裂药花科（16属，约100种）主要分布于南美洲北部圭亚那地盾的特普伊山和沙原，马氏裂药花属仅分布于西非。该科在花形、叶形、习性和生境方面经历了广泛的辐射演化。为分析这些分布和性状的演化，我们基于叶绿体编码的ndhF基因的序列变异，构建了14个属代表种的分子系统发育树。低地亚科裂药花亚科是并系群，包括主要分布于山地的亚科石竹裂药花亚科作为单系子集。总体而言，形态学/解剖学数据在系统发育结构上与ndhF序列有显著差异，但在四个族中的三个族中与分子树显示出高度一致性。分支长度与分子钟的运行一致。马氏裂药花属与其他单型类群的差异仅略微明显：它是相对近期远距离扩散的产物，而非大陆漂移——只是其生长在裂隙发育、养分贫瘠的砂岩上的生境是替代分布。该科似乎起源于约6500万年前圭亚那地盾被淹没的低地，随后经历了以下过程：（1）低地类群沿着河流廊道广泛地理扩散；（2）在西部地盾的亚马逊白沙稀树草原定殖；（3）侵入特普伊生境，伴随频繁物种形成、窄域特有种的演化以及西部地盾中蜂鸟传粉的起源；（4）再次侵入低地白沙稀树草原。约600 - 1200万年前Stegolepis类群明显的物种形成时间，是在约9000万年前大西洋裂开、特普伊山开始彼此分离之后很久才发生的。鉴于大多数山地类群分布狭窄，这表明不频繁的远距离扩散与替代分布共同导致了Stegolepis类群在特普伊山上的物种形成。
