Lucas C. Majure

Are polyploids really evolutionary dead-ends (again)? A critical reappraisal of Mayrose et al. (2011)

Throughout the past century, hybridization and polyploidization have variously been viewed as drivers of biodiversity (e.g. Arnold, 1997) or evolutionary noise, unimportant to the main processes of evolution (e.g. Stebbins, 1950; Wagner, 1970). Wagner (1970) argued that while polyploids have always existed, they have never diversified or played a major role in the evolution of plants, and that the study of polyploidy (as well as inbreeding, apomixis, and hybridization) has led researchers to be ‘carried away with side branches and blind alleys that go nowhere’. However, the use of molecular tools revolutionized the study of polyploidy, revealing that a given polyploid species often forms multiple times (reviewed in Soltis & Soltis, 1993, 1999, 2000, 2009). The realization that recurrent polyploidization from genetically differentiated parents is the rule that shattered the earlier perceptions of polyploids as genetically depauperate (Stebbins, 1950; Wagner, 1970). Because of multiple origins, polyploid species can maintain high levels of segregating genetic variation through the incorporation of genetic diversity from multiple populations of their diploid progenitors (e.g. Soltis & Soltis, 1993, 1999, 2000; Tate et al., 2005). Numerous studies have also shown that polyploid genomes are highly dynamic, with enormous potential for generating novel genetic variation (e.g. Gaeta et al., 2007; Doyle et al., 2008; Leitch & Leitch, 2008; Flagel & Wendel, 2009; Hawkins et al., 2009; Chester et al., 2012; Hao et al., 2013; Roulin et al., 2013). Furthermore, genomic studies have also revealed numerous ancient polyploidy events across the angiosperms (e.g. Vision et al., 2000; Bowers et al., 2003; Blanc &Wolfe, 2004; Paterson et al., 2004; Schlueter et al., 2004; Van de Peer & Meyer, 2005; Cannon et al., 2006; Cui et al., 2006; Tuskan et al., 2006; Jaillon et al., 2007; Barker et al., 2008, 2009; Lyons et al., 2008; Ming et al., 2008; Shi et al., 2010; Van de Peer, 2011; Jiao et al., 2012; McKain et al., 2012; Tayale & Parisod, 2013; reviewed in Soltis et al., 2009); all angiosperms have undergone at least one round of polyploidy (e.g. Jiao et al., 2011; Amborella Genome Consortium, 2013). Polyploidy is now viewed not as a mere side branch of evolution, but as a major mechanism of evolution and diversification.

Phylogeny of Opuntia s.s. (Cactaceae): clade delineation, geographic origins, and reticulate evolution.

PREMISE OF THE STUDY The opuntias (nopales, prickly pears) are not only culturally, ecologically, economically, and medicinally important, but are renowned for their taxonomic difficulty due to interspecific hybridization, polyploidy, and morphological variability. Evolutionary relationships in these stem succulents have been insufficiently studied; thus, delimitation of Opuntia s.s. and major subclades, as well as the biogeographic history of this enigmatic group, remain unresolved. METHODS We sequenced the plastid intergenic spacers atpB-rbcL, ndhF-rpl32, psbJ-petA, and trnL-trnF, the plastid genes matK and ycf1, the nuclear gene ppc, and ITS to reconstruct the phylogeny of tribe Opuntieae, including Opuntia s.s. We used phylogenetic hypotheses to infer the biogeographic history, divergence times, and potential reticulate evolution of Opuntieae. KEY RESULTS Within Opuntieae, a clade of Tacinga, Opuntia lilae, Brasiliopuntia, and O. schickendantzii is sister to a well-supported Opuntia s.s., which includes Nopalea. Opuntia s.s. originated in southwestern South America (SA) and then expanded to the Central Andean Valleys and the desert region of western North America (NA). Two major clades evolved in NA, which subsequently diversified into eight subclades. These expanded north to Canada and south to Central America and the Caribbean, eventually returning back to SA primarily via allopolyploid taxa. Dating approaches suggest that most of the major subclades in Opuntia s.s. originated during the Pliocene. CONCLUSIONS Opuntia s.s. is a well-supported clade that includes Nopalea. The clade originated in southwestern SA, but the NA radiation was the most extensive, resulting in broad morphological diversity and frequent species formation through reticulate evolution and polyploidy.

Synthetic polyploids of Tragopogon miscellus and T. mirus (Asteraceae): 60 Years after Ownbey’s discovery

In plants, polyploidy has been a significant evolutionary force on both recent and ancient time scales. In 1950, Ownbey reported two newly formed Tragopogon allopolyploids in the northwestern United States. We have made the first synthetic lines of T. mirus and T. miscellus using T. dubius, T. porrifolius, and T. pratensis as parents and colchicine treatment of F(1) hybrids. We also produced allotetraploids between T. porrifolius and T. pratensis, which are not known from nature. We report on the crossability between the diploids, as well as the inflorescence morphology, pollen size, meiotic behavior, and fertility of the synthetic polyploids. Morphologically, the synthetics resemble the natural polyploids with short- and long-liguled forms of T. miscellus resulting when T. pratensis and T. dubius are reciprocally crossed. Synthetic T. mirus was also formed reciprocally, but without any obvious morphological differences resulting from the direction of the cross. Of the 27 original crosses that yielded 171 hybrid individuals, 18 of these lineages have persisted to produce 386 S(1) progeny; each of these lineages has produced S(2) seed that are viable. The successful generation of these synthetic polyploids offers the opportunity for detailed comparative studies of natural and synthetic polyploids within a nonmodel system.

Taxonomic studies in the Miconieae (Melastomataceae). XI. A revision of Miconia sect. Calycopteris on Hispaniola

A new section, Miconia sect. Calycopteris, is described and characterized. It includes 15 species previously recognized within Calycogonium, Clidemia, Henriettella, Leandra, Miconia, and Ossaea. Species descriptions, nomenclatural information, specimen citations, and eco-geographical characterization for each of the eight species occurring on Hispaniola are presented, along with an identification key. Section Calycopteris likely represents a monophyletic group within the Caribbean clade of tribe Miconieae (Melastomataceae) and is restricted to Hispaniola and Cuba. The section is characterized by strongly 4-lobed ovaries and hypanthia, calyx teeth that are flattened parallel to the floral radii, and seeds with a distinctive, dark-colored and expanded raphe. The following new combinations and new names are presented: Miconia hispidula, M. calycopteris, M. tetragonoloba, M. formonensis, M. nanophylla, M. reticulato-venosa, M. vegaensis, and M. maculata.

Miconia cineana (Melastomataceae: Miconieae), a New Species from the Massif de la Hotte, Haiti, Based on Morphological and Molecular Evidence

Abstract We describe a new species, Miconia cineana (Melastomataceae: Miconieae), from the Massif de la Hotte, Haiti. Although this species has been known from sterile collections since the early 1980s, its phylogenetic position was unknown, although it was presumed to be closely related to species of Pachyanthus s. l. The phylogenetic reconstruction presented here, based on a recent collection of the species, clearly places M. cineana in a clade comprised of Cuban species of the polyphyletic genera Tetrazygia s. l. and Pachyanthus s. l. Thus, M. cineana represents the sole Hispaniolan member of an otherwise Cuban clade, and an uncommon biogeographic pattern in melastomes. Miconia cineana, although described here from sterile specimens, is easily distinguished from the other species of this clade using vegetative morphology, as well as phylogenetic placement. This study highlights the utility of molecular data when coupled with morphology, allowing for the discovery of an unrecognized species in a region of high diversity and endemism, i.e. the Massif de la Hotte.

Miconia bullotricha and M. hirtistyla, two new species of Miconia sect. Lima (Miconieae, Melastomataceae) from eastern Cuba

Abstract We describe two new species in Miconia sect. Lima, Miconia bullotricha Bécquer & Majure and Miconia hirtistyla Majure & Judd, from eastern, Cuba. We also provide illustrations and distribution maps for the two species, as well as a key to members of the Lima clade on Cuba.

Miconia becqueri , a new species of Miconia (Melastomataceae) with strongly four-lobed ovaries from the Sierra Maestra, Cuba

A new species of Miconia belonging to a clade diagnosed by strongly four-lobed ovaries/hypanthia and elongated calyx teeth flattened parallel to the floral radii, i.e., the Calycogonium hispidulum complex, endemic to the Sierra Maestra of eastern Cuba, is described, illustrated, and compared with related Cuban species. The discovery of Miconia becqueri brings to 15 the number of recognized species of this complex, seven of which occur in Cuba (if Clidemia barbeyana is conspecific with C. wrightii).

Taxonomic revision of the Greater Antillean Pseudolima clade of Miconia (Miconia sect. Krugiophytum: Miconieae: Melastomataceae)

The Pseudolima clade (Miconia sect. Krugiophytum) consists of two Puerto Rican species, M. karlkrugii and M. krugiana and one Hispaniolan species, M. inaequipetiolata. All three species display morphological characters (e.g., bulla-based hairs) that resemble those found in Miconia sect. Lima, and for that reason had been considered to be putative members of the Lima clade. Molecular phylogenetic analyses, presented here, suggest that these taxa actually are not most closely related to members of the Lima clade, and thus it appears likely that the characters seemingly linking these species with the Lima clade either are symplesiomorphic or convergent. These three species are representative of the taxonomic difficulties regarding determination of clade affinities (and generic limits) using morphological characters, which is a common problem in Miconieae. We provide a taxonomic revision of these three species including illustrations, distribution maps and descriptions.ResumenEl clado Pseudolima (Miconia secc. Krugiophytum) consta de dos especies de Puerto Rico, M. karlkrugii y M. krugiana, y una de La Española, M. inaequipetiolata. Las tres especies muestran caracteres morfológicos (e.g., tricomas expandidos en la base) que se asemejan a los que se encuentran en Miconia sect. Lima y por esa razón han sido considerado como miembros putativos del clado Lima. Los análisis de filogenética molecular presentados aquí sugieren que estas especies están más relacionados a otros clados que al clado Lima, por lo que los caracteres semejantes a los del clado Lima probablemente son plesiomórficos o convergentes. Estas tres especies demuestran las dificultades taxonómicas con la delimitación de las afinidades de clados (y límites genéricos) tomando en cuenta solo la morfología, un problema muy común en la tribu Miconieae. Proveemos una revisión taxonómica de estas tres especies que incluye ilustraciones, mapas de distribución y descripciones.

Miscellaneous Chromosome Numbers in Opuntieae Dc. (Cactaceae) with a Compilation of Counts for the Group

Abstract: Chromosome counts of members of the Opuntieae were carried out to further our understanding of ploidal levels, species boundaries, and evolutionary patterns within this group of stem succulents, which has been well-studied cytologically and is well known for hybridization and polyploidy. Here we counted chromosomes of 53 taxa in 4 genera (Consolea Lem., Nopalea Salm-Dyck, Opuntia Mill., and Tacinga Britton & Rose). Thirty of these counts are the first for a given taxon, and six counts represent a different ploidy for a taxon than has been reported previously. We also present a review of chromosome counts reported for Opuntieae. Ploidy in these taxa ranged from diploid, 2n = 2x = 22, to 20-ploid, 2n = 20x = 220. Of the 164 species in the Opuntieae for which chromosome counts have been carried out, including our new counts, 26.2% are diploid, 13.4% are both diploid and polyploid, and 60.4% are polyploid reiterating that the frequency of genome duplication in the group is far more common than diploidy.

Evolution of the Sandpaper Clade (Miconieae, Melastomataceae)

Premise of research. The Sandpaper clade comprises a group of taxa endemic to the Greater Antilles and forms a subgroup of a larger Caribbean assemblage of Miconieae. Numerous species within this monophyletic group share striking morphological characters and thus traditionally have been considered close relatives. Recent phylogenetic work has shown that not all of these species are each other’s closest relatives, and they actually form three distinct clades: the Lima, Paralima, and Pseudolima clades. We reconstructed a phylogeny of these poorly known species to test patterns of morphological evolution and the biogeographic history of the clade. Methodology. We reconstructed a phylogeny of the Sandpaper clade using two plastid intergenic spacers (accD-psaI, psbK-psbL) and two nuclear ribosomal spacers (ITS, ETS) and then sequenced three more plastid spacers for the Lima clade (rpl32-trnL, trnV-ndhC, trnH-psbA) to provide better resolution among those species. The biogeographic history and the evolution of morphological traits were tested using maximum parsimony based on 12 mountain ranges in the Greater Antilles and 48 morphological characters, respectively. Pivotal results. The Sandpaper clade most likely originated in eastern Cuba, with subsequent dispersals to other parts of the island, as well as to Jamaica, Hispaniola, and Puerto Rico. In general, morphological characters shared by the Lima, Paralima, and Pseudolima clades evolved independently. All subclades of the Sandpaper clade can be recognized by suites of characters; however, unique synapomorphies for clades are rare. Conclusions. Eastern Cuba formed the starting point for the diversification of the Sandpaper clade, likely as a result of the diverse topography and associated ecological diversity (e.g., serpentine soils). This clade represents only a moderate-sized radiation of the Caribbean clade; however, the convergent nature of character evolution and the lack of unique synapomorphies for subclades underscore the lability of morphological characters in this group and the difficulty in recognizing these clades from a purely morphological standpoint.