Genomic footprints of repeated evolution of CAM photosynthesis in a Neotropical species radiation.

The adaptive radiation of Bromeliaceae (pineapple family) is one of the most diverse among Neotropical flowering plants. Diversification in this group was facilitated by shifts in several adaptive traits or "key innovations" including the transition from C <sub>3</sub> to CAM photosynthesis associated with xeric (heat/drought) adaptation. We used phylogenomic approaches, complemented by differential gene expression (RNA-seq) and targeted metabolite profiling, to address the mechanisms of C <sub>3</sub> /CAM evolution in the extremely species-rich bromeliad genus, Tillandsia, and related taxa. Evolutionary analyses of whole-genome sequencing and RNA-seq data suggest that evolution of CAM is associated with coincident changes to different pathways mediating xeric adaptation in this group. At the molecular level, C <sub>3</sub> /CAM shifts were accompanied by gene expansion of XAP5 CIRCADIAN TIMEKEEPER homologs, a regulator involved in sugar- and light-dependent regulation of growth and development. Our analyses also support the re-programming of abscisic acid-related gene expression via differential expression of ABF2/ABF3 transcription factor homologs, and adaptive sequence evolution of an ENO2/LOS2 enolase homolog, effectively tying carbohydrate flux to abscisic acid-mediated abiotic stress response. By pinpointing different regulators of overlapping molecular responses, our results suggest plausible mechanistic explanations for the repeated evolution of correlated adaptive traits seen in a textbook example of an adaptive radiation

Phylogenetic relationships within Tillandsia subgenus Diaphoranthema (Bromeliaceae, Tillandsioideae) based on a comprehensive morphological dataset

Tillandsia subgenus Diaphoranthema (Tillandsioideae, Bromeliaceae) includes 29 epiphytic species distributed widely from southern North America to central Argentina and Chile. The species of Diaphoranthema are characterized by few small flowers, and most species are differentiated by phyllotaxy, leaf shape, flower number, and by the morphology and number of bracts. In addition to the highly variable vegetative characters, most species of subgenus Diaphoranthema possesses polyembryonic seeds (rare in Bromeliaceae) and an autogamous breeding system with a few number of species having cleistogamous flowers. In order to clarify relationships within Diaphoranthema and to understand the evolution of polyembryony, the breeding system, and diagnostic characters, a cladistic analysis of all known species using 85 morphological characters was conducted. Phylogenetic results suggest that Diaphoranthema is monophyletic if some species from the closely related subgenus Phytarrhiza are included. These two subgenera can only be distinguished from each other by the shape and size of their petals. A complete sampling of Phytarrhiza is still needed to test these hypotheses. None of the six informal groups as previously recognized are monophyletic. Vegetative characters such as phyllotaxy and the shape, length, and width of leaves were the most useful for distinguishing four major clades within Diaphoranthema. Flower number, scape development, exocarp and endocarp fusion at fruit ripening, and absence of endosperm in mature seeds were also used to distinguish some clades. Evolutionary trends favour a distichous phyllotaxy, linear shape leaf blades, and a reduction in flower number and bracts per inflorescence. In addition, capsules with disaggregating exocarp and endocarp at ripening, and polyembryonic seeds are also derived states within subgenus Diaphoranthema.Fil: Donadío, Sabina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Pozner, Raul Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Giussani, Liliana Mónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; Argentin

Within-population spatial genetic structure in four naturally fragmented species of a neotropical inselberg radiation, Alcantarea imperialis, A. geniculata, A. glaziouana and A. regina (Bromeliaceae)

Studies of organisms on 'terrestrial islands' can improve our understanding of two unresolved issues in evolutionary genetics: the likely long-term effects of habitat fragmentation and the genetic underpinnings of continental species radiations in island-like terrestrial habitats. We have addressed both issues for four closely related plant species of the adaptive radiation Bromeliaceae, Alcantarea imperialis, A. geniculata, A. regina and A. glaziouana. All four are adapted to ancient, isolated inselberg rock outcrops in the Brazilian Atlantic rainforest and are thus long-term fragmented by nature. We used eight nuclear microsatellites to study within-population spatial genetic structure (SGS) and historical gene dispersal in nine populations of these species. Within-population SGS reflected known between-species differences in mating systems. The strongest SGS observed in A. glaziouana (Sp = 0.947) was stronger than literature estimates available for plants. Analysis of short- and long-distance components of SGS identified biparental inbreeding, selfing and restricted seed dispersal as main determinants of SGS, with restricted pollen dispersal by bats contributing in some localities. The ability of Alcantarea spp. to colonize isolated inselbergs probably stems from their flexible mating systems and an ability to tolerate inbreeding. Short-ranging gene dispersal (average sigma = 7-27 m) is consistent with a loss of dispersal power in terrestrial island habitats. Population subdivision associated with sympatric colour morphs in A. imperialis is accompanied by between-morph differences in pollen and seed dispersal. Our results indicate a high potential for divergence with gene flow in inselberg bromeliads and they provide base-line data about the long-term effects of fragmentation in plants. © 2008 Macmillan Publishers Limited All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe