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Our objective was to infer the climate drivers of regionally synchronous fire years in dry forests of the U.S. northern Rockies in Idaho and western Montana. During our analysis period (1650-1900), we reconstructed fires from 9245 fire scars on 576 trees (mostly ponderosa pine, Pinus ponderosa P. & C. Lawson) at 21 sites and compared them to existing tree-ring reconstructions of climate (temperature and the Palmer Drought Severity Index [PDSI]) and large-scale climate patterns that affect modern spring climate in this region (El Niño-Southern Oscillation [ENSO] and the Pacific Decadal Oscillation [PDO]). We identified 32 regional-fire years as those with five or more sites with fire. Fires were remarkably widespread during such years, including one year (1748) in which fires were recorded at 10 sites across what are today seven national forests plus one site on state land. During regional-fire years, spring-summers were significantly warm and summers were significantly warm-dry whereas the opposite conditions prevailed during the 99 years when no fires were recorded at any of our sites (no-fire years). Climate in prior years was not significantly associated with regional- or no-fire years. Years when fire was recorded at only a few of our sites occurred under a broad range of climate conditions, highlighting the fact that the regional climate drivers of fire are most evident when fires are synchronized across a large area. No-fire years tended to occur during La Niña years, which tend to have anomalously deep snowpacks in this region. However, ENSO was not a significant driver of regional-fire years, consistent with the greater influence of La Niña than El Niño conditions on the spring climate of this region. PDO was not a significant driver of past fire, despite being a strong driver of modern spring climate and modern regional-fire years in the northern Rockies.

Premise of research. Recently diverged taxa may not exhibit strong morphological or DNA sequence differences, making evaluating species boundaries difficult. Finer-scale markers and alternate analytical methods can be used to address species status in these closely related taxa. The dwarf milkweeds have been variably treated as including between one and four species, but no comprehensive assessment of this group has been conducted. Little is known regarding the population genetics of these four putative species, three of which are of conservation concern. Methodology. We used microsatellite markers, population genetic and genetic structure analyses, ecological niche modeling, and approximate Bayesian computation to explore species circumscription and relationships in the group. Pivotal results. Moderate genetic differentiation was detected among four putative species of Asclepias. Genetic clustering revealed four distinct clusters corresponding to the allopatric distributions of the four previously described morphological species. The ecological niche of each of the four dwarf milkweed species is strongly influenced by different sets of bioclimatic variables. Projections of potential suitable habitat in the past indicated that there might have been suitable habitat for all four species by the mid-Holocene, but projections of potential suitable habitat during the Last Glacial Maximum suggest that the current ecological niche of two of the four species was not present at that time. A coalescent scenario of a simultaneous four-way divergence event best fits the data. Conclusions. Multiple lines of evidence reinforce the hypothesis that the dwarf milkweed clade is composed of four morphologically similar but genetically and ecologically distinct species.

Background Prairie–forest ecotones are ecologically important for biodiversity and ecological processes. While these ecotones cover small areas, their sharp gradients in land cover promote rich ecological interaction and high conservation value. Our objective was to understand how historical and current fire occurrences and human development influenced the Palouse Prairie–forest ecotone. We used General Land Office survey field notes about the occurrence of bearing trees to locate historical (1870s to 1880s) prairie, pine savanna, and forest at the eastern edge of the bioregion. We combined LANDFIRE Existing Vegetation classes to contrast historical land cover with current land cover. We reconstructed historical fire occurrence (1650 to 1900) from fire-scarred trees. We used fire and lightning records from 1992 to 2015 to interpret the role of people and lightning. Results Historically, the ecotone was a matrix of prairie with extensive savanna and some forest. More than half of the ecotone area was prairie, which is now dominated by agriculture, with some residential development. The 16% of the landscape that was pine savanna is now forest or shrubs, agriculture, perennial vegetation under the Conservation Reserve Program, or developed; no savanna now exists. Forests covered 12% of the ecotone and these are still mostly forest. Fires were historically frequent, occurring on average every 5 to 8 years at most sites. Lightning was not frequent but could likely have been sufficient to ignite fires that could spread readily given the rolling terrain and long fire season. Conclusions Fire was far more frequent historically than currently. Conservation, restoration, and other ongoing land-use changes will likely result in more continuous vegetation and hence fuel for fires. Lightning and people may ignite fires that therefore spread readily in the future. Understanding the past and potential future of fire in the Palouse Prairie bioregion may help us live with fire while conserving ecological values here and in similar prairie–forest ecotones.

• Premise of Study: A monophyletic group composed of five genera of the Cleomaceae represents an intriguing lineage with outstanding taxonomic and evolutionary questions. Generic boundaries are poorly defined, and historical hypotheses regarding the evolution of fruit type and phylogenetic relationships provide testable questions. This is the first detailed phylogenetic investigation of all 22 species in this group. We use this phylogenetic framework to assess generic monophyly and test Iltis’s evolutionary “reduction series” hypothesis regarding phylogeny and fruit type/seed number.• Methods: Maximum likelihood and Bayesian analyses of four plastid intergenic spacer region sequences (rpl32-trnL, trnQ-rps16, ycf1-rps15, and psbA-trnH) and one nuclear (ITS) region were used to reconstruct phylogenetic relationships among the NA cleomoid species. Stochastic mapping and ancestral-state reconstruction were used to study the evolution of fruit type.• Key Results: Both analyses recovered nearly identical phylogenies. Three of the currently recognized genera (Wislizenia, Carsonia, and Oxystylis) are monophyletic while two (Cleomella and Peritoma) are para- or polyphyletic. There was a single origin of the two-seeded schizocarp in the ancestor of the Oxystylis–Wislizenia clade and a secondary derivation of elongated capsule-type fruits in Peritoma from a truncated capsule state in Cleomella.• Conclusions: Our well-resolved phylogeny supports most of the current species circumscriptions but not current generic circumscriptions. Additionally, our results are inconsistent with Iltis’s hypothesis of species with elongated many-seed fruits giving rise to species with truncated few-seeded fruits. Instead, we find support for the reversion to elongated multiseeded fruits from a truncate few-seeded ancestor in Peritoma.

Premise of the study: Microsatellite primers were developed to characterize genetic diversity and structuring in the genus Phacelia (Hydrophyllaceae) and to further conservation efforts for P. formosula. Methods and Results: Fifteen novel microsatellite primers were developed for P. formosula. These were characterized for genetic variation in three separate P. formosula populations. Two to nine alleles were found per locus. Overall observed heterozygosity and expected heterozygosity ranged from 0.000 to 0.800 and 0.000 to 0.840, respectively. Additionally, these loci were successfully amplified and showed polymorphism in P. gina-glenneae and a potential new Phacelia species. Conclusions: These microsatellite markers will be useful in assessing genetic diversity, structuring, and gene flow within and among populations of the rare P. formosula, in addition to related Phacelia species. These markers will provide important genetic data needed for appropriate conservation and management of these rare plants.

Western North American physiography is characterized by considerable habitat heterogeneity accompanied by temporal environmental changes associated with climate fluctuations during the recent Pleistocene. This heterogeneity is a major driver the process of diversification, especially when distributions become allopatric or parapatric. Processes related to recently diverged taxa such as incomplete lineage sorting and hybridization are a challenge to species-level and above-species level studies of the evolution of the western North American flora. The North American cleomoids (Cleomaceae), a monophyletic group composed of five genera, poorly defined generic boundaries although species are reasonably well delimited. This detailed phylogenetic investigation generated a phylogenetic framework to assess generic monophyly and test historical evolutionary hypotheses regarding phylogeny and evolution of fruit type in this group. Four diminutive species of Asclepias found in western North America, termed the dwarf milkweed group, exhibit observable, but subtle, morphological differences corresponding to their allopatric distributions. I analyzed microsatellite markers to explore species boundaries in this group. Bayesian genetic structuring, approximate Bayesian computation, assessments of genetic distance discontinuities, and ecological niche modeling were used to explore species boundaries and inform taxonomic choices regarding the species status of these four dwarf milkweeds.