MOLECULAR EVOLUTION, ADAPTIVE RADIATION, AND GEOGRAPHIC DIVERSIFICATION IN THE AMPHIATLANTIC FAMILY RAPATEACEAE: EVIDENCE FROM ndhF SEQUENCES AND MORPHOLOGY

Abstract

Abstract. Rapateaceae (16 genera, ϳ100 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.

Gondwanan Origin of Major Monocot Groups Inferred from Dispersal-Vicariance Analysis

“…A number of biogeographical analyses of particular monocot groups have already been published (Linder 1987;Seberg 1988;Simpson 1990;Conran 1995;Givnish et al 1999;Vinnersten and Bremer 2001;Bremer 2002). Several of these studies indicate that commelinid groups, Commelinales and Poales in particular, evolved in the Southern Hemisphere, corroborating earlier hypotheses by Raven and Axelrod (1974).…”

“…Chase et al (2000) proposed a first phylogeny including all orders, based on a large data set including three DNA regions (rbcL,atpB,and 18S rDNA [ribosomal DNA]), however with a comparatively limited taxon sampling. More detailed treatments are available for several orders (papers in Rudall et al 1995 andin Wilson et al 2000;Givnish et al 1999;Kress et al 2001;Vinnersten and Bremer 2001;Bremer 2002;Caddick et al 2002). With the results of the available studies taken together we have at present a rather wellsupported phylogeny resolved down to the family level.…”

Rapateaceae in the state of Pará, Brazil

“…Maguire (1958;1962;1965;1979) refi ned the taxonomy of the family, and these studies remain the most important about the group. In addition, Givnish et al (2000;2004) published the first phylogeny of the family, based on molecular data and morphological characters, which confi rmed the suprageneric taxa proposed by Maguire (1958;1962;1965;1979).…”

“…Rapateaceae comprises approximately 19 genera and 131 species distributed in the Neotropics, with exception to the monotypic genus Maschalocephalus that is endemic to West Africa (Givnish et al 2000). In Brazil, there are nine genera and 38 recorded species, which are distributed in every region except the South Region of the country (BFG 2015).…”

Phylogenetic Structure of Floridian Plant Communities Depends on Taxonomic and Spatial Scale

“…(e.g., Schluter 2000) and adaptive radiation (e.g., Givnish et al 2000) are well documented. To the extent that evolutionary stasis predominates, close relatives are likely to occur in similar habitats, given that plants will track environments for which they are adapted (Ackerly 2003).…”