Leigh Johnson

Brigham Young University - Provo Main Campus | BYU · Department of Biology

The taxonomic concept for Navarretia minima, when treated as a species or as a subspecies of N. leucocephala, has drifted dramatically from the protologue and original material on which the name is based. Taxonomic concepts from regional floristic works are reviewed to understand the historical context of this drift. Navarretia minima is re-establi...

Calyceraceae is a small South American family sister to Asteraceae. Previous phylogenetic analyses revealed that Calyceraceae genera are para‐ or polyphyletic. Fruit and inflorescence characters used historically as diagnostic in Calyceraceae taxonomy have proven unreliable in defining natural groups. Surprisingly, flower morphology does not appear...

Chorizanthe angustifolia var. eastwoodiae was named by Goodman in 1934, but has since generally been ignored as a taxon. A limited number of C. angustifolia var. angustifolia collections available for comparison and lack of clearly defined characters differentiating the two varieties likely account for the taxonomic concept for C. angustifolia that...

Shared genetic patterns within a community of ecologically distinct species may reflect the role of past geoclimatic events imprinting species evolutionary history. Although Pleistocene glaciations are the most important processes evoked as drivers of these shared patterns, in some regions Quaternary volcanic activity should also be considered as a...

Congruence among different sources of data is highly desirable in phylogenetic analyses. However, plastid and nuclear DNA may record different evolutionary processes such that incongruence among results from these sources can help unravel complex evolutionary histories. That is the case of Nassauvia subgenus Strongyloma (Asteraceae), a taxon with f...

Habitat fragmentation due to anthropogenic activities is the major cause of biodiversity loss. Endemic and narrowly distributed species are the most susceptible to habitat degradation. Penstemon scariosus is one of many species whose natural habitat is vulnerable to industrialization. All varieties of P. scariosus (P. scariosus var. albifluvis, P....

Convergence is a pervasive phenomenon in the Tree of Life, and evolution of similar phenotypes sharing the same environmental conditions is expected in phylogeneti-cally closely related species. In contrast, contingent factors are probably more influential in shaping phenotypic diversity for distantly related taxa. Here, we test putative convergent...

The Calyceraceae (47 spp.) is a small family of plants that is sister to the Asteraceae (∼ 25,000 spp.), one of the largest families of angiosperms. Most members of Calyceraceae are endemic to the Andes and Patagonia, representing an excellent model within which to study diversification patterns in these regions. The single phylogenetic study of Ca...

A key to understanding the origin and identity of young species lays on the knowledge of the Quaternary climatic oscillations’ effect on gene flow and vicariance. Even though the effect of climatic fluctuations is relatively well understood for southern hemisphere plant species, little is known about their effect on the evolutionary histories of sp...

A new species narrowly endemic to the extremely arid western portion of the San Joaquin Desert, California, Navarretia panochensis, is here described. This species belongs to the N. pubescens group of Navarretia section Mitracarpium, sharing several features including the presence of three cotyledons. It is distinguished from these near relatives b...

Geologic events promoting the aridization of southern South America contributed to lineage divergences and species differentiation through geographic (allopatric divergence) and biotic and abiotic factors (ecological divergence). For the genus Anarthrophyllum, which is distributed in arid and semi-arid regions of Patagonia, we assessed how these fa...

Navarretia divaricata , endemic to western North America and most recently considered a single species with two subspecies, was re-examined in light of field work, DNA sequences, comparative morphology, and a review of herbarium specimens including types. From these studies, we lectotypify the material on whichN. divaricatais based, elevate N. diva...

Premise of the study: Following establishment after long-distance dispersal, species may experience stasis, accumulate changes leading to new species identity, diversify into multiple species, interact with related species to form novel species, and even become extirpated. We examined each species of temperate Polemoniaceae in South America via th...

PREMISE OF THE STUDY: Historical patterns and processes of plants with an American amphitropical disjunct (AAD) distribution have long interested botanists and biogeographers. Here we update examples of AAD vascular plants, their biogeographic history, and aspects of their biology elucidated by recent studies to make inferences about common pattern...

Effects of Pleistocene climatic oscillations on plant phylogeographic patterns are relatively well studied in forest, savanna and grassland biomes, but such impacts remain less explored on desert regions of the world, especially in South America. Here, we performed a phylogeographical study of Monttea aphylla, an endemic species of the Monte Desert...

Internal primer sequences designed for trnQ–rpL16 region. (DOC)

Outgroup species, locality, coordinates, and voucher number in CORD. (DOC)

Document. Permission to publishmap shapefiles. (DOC)

Sampling sites, geographical coordinates, sample size, elevation, and molecular diversity indexes of the sampled Monttea aphylla populations in the South American Arid Diagonal for each data set. (DOC)

Location for each set of primers in the trnQ–rpL16 sequence. (DOC)

Summary of the results from the species-specific tuning of the ecological niche modelling carried out with 10 replicated runs under the current climatic conditions. (DOC)

Curetted database of the presence points for M. aphylla and the associated absence data used in the potential distribution models. (DOC)

Percentage contribution of climatic variables to the past (LIG and LGM) and current potential distributions of Monttea aphylla. (DOC)

Calyceraceae is a small family with six traditionally recognized genera and 47 species from southern South America. Most species grow along the Andes (of both Argentina and Chile) and in arid regions of the Patagonian steppe. This family belongs to the well-supported MGCA clade within Asterales, which includes Menyanthaceae + Goodeniaceae + Calycer...

Penstemon luculentus R.L. Johnson & M.R. Stevens, nom. nov. replaces Penstemon fremontii var. glabrescens Dorn & Lichvar. The varietal name glabrescens was not elevated because it was already occupied by Penstemon glabrescens Pennell, a different species. This new arrangement is supported by molecular and morphological evidence. An analysis of gene...

Two species endemic to California in the western United States, Navarretia crystallina and N. miwukensis, are here described. Both species occur on soils derived from pyroclastic flows. N. crystallina is distributed more widely, generally at higher elevations, and occurs predominantly to the north and east of N. miwukensis. Though similar in habit...

• Premise of the study: The American Cross Timbers forest ecosystem runs from southeastern Kansas to Central Texas and is primarily composed of post oak (Quercus stellata). This old-growth forest currently occupies only about 2% of its ancestral range. To facilitate genetic research on this species, we developed microsatellite primers specific to p...

The Patagonian steppe is an immense, cold, arid region, yet phylogeographical-ly understudied. Nassauvia subgen. Strongyloma is a characteristic element of the steppe, exhibiting a continuum of morphological variation. This taxon pro-vides a relevant phylogeographical model not only to understand how past environmental changes shaped the genetic st...

The coastal deserts of northern Chile show an important latitudinal gradient of aridity with more arid areas to the north of the Atacama Desert than to the south. Several plant species have disjunct distributions that correspond with the extremes of this latitudinal gradient. In this study, using genetic (chloroplast and nuclear DNA), morphological...

Morphological variation among the five species of Nassauvia subgenus Strongyloma was assessed through statistical analyses of morphometric traits in populations throughout the southern Andean-Patagonian region. Uni-and multivariate analyses were used to identify patterns of morphological variation in relation to geography. Additionally, species dis...

Penstemon's unique phenotypic diversity, hardiness, and drought-tolerance give it great potential for the xeric landscaping industry. Molecular markers will accelerate the breeding and domestication of drought tolerant Penstemon cultivars by, creating genetic maps, and clarifying of phylogenetic relationships. Our objectives were to identify and va...

Fungal selectivity (range of potential partners) for algal symbionts has been found to vary in lichen associations. Although a large number of studies have focused on the taxonomy and evolution of fungi in the speciose parmelioid clade (Parmeliaceae, Ascomycota), fungal-algal interactions in this ecologically and evolutionarily diverse group remain...

Two species endemic to California in the western United States, Navarretia paradoxiclara and N. paradoxinota, are here described. Both species occur on serpentine influenced soils and have been previously collected as N. intertexta, with which they are sympatric. However, they vary from N. intertexta subtly, yet consistently, in floral features and...

In order to assess the impact of precipitation changes during Pleistocene glaciations on plant species of the Patagonian steppe, a phylogeographical study of the endemic shrub Anarthrophyllum desideratum was performed. Southern Patagonia: Argentina and Chile. Chloroplast intergenic spacers trnS–trnG and rpoB–trnC were sequenced for 264 individuals...

In order to assess the impact of precipitation changes during Pleistocene glaciations on plant species of the Patagonian steppe, a phylogeographical study of the endemic shrub Anarthrophyllum desideratum was performed. Southern Patagonia: Argentina and Chile. Chloroplast intergenic spacers trnS–trnG and rpoB–trnC were sequenced for 264 individuals...

Amphitropical disjunct distributions between western North America and western South America have intrigued botanists for over a century. Here, specific examples of migration and speciation are investigated using herbaceous species from the phlox family (Polemoniaceae) as a model for considering the timing of dispersal relative to speciation. Compa...

Aim An integrative study of the endemic, yet ubiquitous, Patagonian shrub Mulinum spinosum (Apiaceae) was performed: (1) to assess the historical processes that influenced its geographical pattern of genetic variation; (2) to test hypotheses of its survival in situ or in glacial refugia during glacial cycles; and (3) to model its extant and palaeoc...

Morphological and DNA-based characters distinguish a new diploid species centered in the Intermountain Region of the western United States, Navarretia furnissii, from N. saximontana, which is tetraploid. The two species are reciprocally monophyletic in analyses of chloroplast DNA sequences and nrDNA ITS sequences. Navarretia furnissii, presently kn...

Premise of the study: Phylogenies based on molecular data are revealing that generalizations about complex morphological structures often obscure variation and developmental patterns important for understanding the evolution of forms, as is the case for inflorescence morphology within the well-supported MGCA clade (Menyanthaceae + Goodeniaceae + C...