Oligotrophic spring vegetation in Spanish mountain ranges

Montio-Cardaminetea syntaxa occurring in the siliceous mountains of the Iberian Peninsula are reviewed. At the highest altitudes three associations are recognized in Spanish mountain ranges: one in the Pyrenees,Montio-Bryetum schleicheri (alpine-subalpine); another in the Ibero-Atlantic ranges,Stellario alsines-Saxifragetum alpigenae (oromediterranean); and a third in the Sierra Nevada,Sedo melanantheri-Saxifragetum alpigenae (oromediterranean). At slightly lower altitudes two other associations have been identified:Myosotidetum stoloniferae (supramediterranean), located in the western ranges; andSaxifragetum aquaticae (subalpine), located in the central and eastern Pyrenees. Syntaxonomically the Pyrenean associations are classified in theCardamino-Montion alliance, the Ibero-Atlantic associations in theMyosotidion stoloniferae alliance, and the Sierra Nevada association in a hypothetical Nevadan-North African alliance. A western European framework is suggested for the Spanish mountain associations which mainly show an E-W distribution pattern.     

Bear historical ranges revisited: Documenting the increase of a once-extirpated population in Nevada

Black bears (Ursus americanus) were once abundant in Nevada and distributed throughout the state, yet recognition of the species' historical occurrence in the state is uncommon and has therefore been ignored in published distribution maps for North America. The lack of representation on distribution maps is likely due to the lack of any scientific data or research on bears in Nevada until 1987. Historical records dating back to the 1840s compiled by Nevada Department of Wildlife (NDOW) biologist Robert McQuivey indicate presence of black bears throughout the state in the 1800s through about 1930. The paucity of historical references after 1931 suggest extirpation of black bears from Nevada's interior mountain ranges by this time. We report on historical records of black bears in the state of Nevada and the results of a current population estimate of black bears derived from a sample of marked bears (n = 420) captured 707 times between 1997 and 2008. Using Pradel and Cormack–Jolly–Seber models in Program MARK, we estimated overall population size, finite rate of growth (λ = 1.16), quarterly and annual survival rates for males and females, seasonal capture probabilities, and recruitment rates. Our results indicate an overall population size of 262 ± 31 adult black bears in western Nevada. These results suggest that the once abundant, then extirpated population of black bears in Nevada is increasing at an annual average rate of 16%. Although the current distribution is limited to the western part of the state, our findings suggest possible expansion of the population into historical habitat within the interior and eastern portions of the state that have been absent of bears for >80 years. Finally, based on historical records, we present suggested revised historical distribution maps for black bears that include the Great Basin ranges in Nevada. © 2013 The Wildlife Society.     

Grimmia serrana (Bryopsida,Grimmiaceae), a new species from California,U.S.A.

Abstract

Grimmia serrana, a new endemic species for California, is described and illustrated. The new species is readily distinguished by the presence of multi-stratose marginal bands that are rounded in cross-section. The leaf morphology displayed by Grimmia serrana is unique within the genus. The distribution of Grimmia serrana is along the western foothills of the Sierra Nevada and in the northern Coast Range.     

A revision of the salvia dorrii complex (Lamiaceae)

Expressions of theSalvia dorrii (Kellogg) Abrams complex, a member of subg.Audibertia Benth., are distributed over much of the western United States. The complex consists of two species,S. dorrii andS. pachyphylla Epling ex Munz.Salvia dorrii is divided into subsp.dorrii and subsp.mearnsii (Britton) McClintock, the latter endemic to central Arizona. Subspeciesdorrii is composed of four varieties: var.carnosa (Douglas ex Greene) Cronq., a large-leaved erect shrub of Washington and Idaho southward through Oregon into extreme north-central California: var.dorrii, a small-leaved erect shrub of southern Oregon and Idaho southward through the Great Basin of Nevada and western Utah to southeastern California and northern Arizona: var.pilosa (A. Gray) Strachan & Reveal, a small-leaved erect shrub differing from var.dorrii by pilose bracts and calyx, in southern California and western Arizona with disjunct populations in the Lahontan Basin of northwestern Nevada and northestern California; and var.clokeyi Strachan, var. nov., a low mat-forming subshrub of the high mountains of Clark Co., Nevada.Salvia pachyphylla ranges from southern California southward to the high mountains of Baja California Norte, Mexico, and eastward across extreme southern Nevada to (as a disjunct) northeastern Arizona. Each entity is described in detail, mapped and illustrated.     

Genetic structure of mountain lion (Puma concolor) populations in California

Analysis of 12 microsatellite loci from431 mountain lions (Puma concolor)revealed distinct genetic subdivision that wasassociated with geographic barriers andisolation by distance in California. Levels ofgenetic variation differed among geographicregions, and mountain lions that inhabitedcoastal areas exhibited less heterozygositythan those sampled inland. The San FranciscoBay and Sacramento-San Joaquin River Delta, theCentral Valley, and the Los Angeles Basinappeared to be substantial barriers to geneflow, and allele frequencies of populationsseparated by those features differedsubstantially. A partial barrier to gene flowappeared to exist along the crest of the SierraNevada. Estimated gene flow was high amongmountain lions inhabiting the Modoc Plateau,the western Sierra Nevada, and northern sectionof the eastern Sierra Nevada. SouthernCalifornia mountain lion populations mayfunction as a metapopulation; however, humandevelopments threaten to eliminate habitat andmovement corridors. While north-south geneflow along the western Sierra Nevada wasestimated to be very high, projected loss andfragmentation of foothill habitat may reducegene flow and subdivide populations. Preservation of existing movement corridorsamong regions could prevent population declinesand loss of genetic variation. This studyshows that mountain lion management andconservation efforts should be individualizedaccording to region and incorporatelandscape-level considerations to protecthabitat connectivity.     

Significance of Middle Cambrian mixed carbonate-siliciclastic units for global correlation: southern Nevada, USA

Sequence-stratigraphic analysis of the Middle Cambrian Highland Peak, Bonanza King, Swasey, and Wheeler formations in the Great Basin refines platform-to-basin correlations and distinguishes local tectonic events from eustasy. This analysis provides a reliable sea-level history through the Ptychagnostus gibbus and Ptychagnostus atavus trilobite intervals and confirms that the Global Stratotype Section and Point (GSSP) at the first appearance datum (FAD) of P. atavus was deposited during an overall sea-level rise. Deposition during the Middle Cambrian Ehmaniella/Bolaspidella biozones in the western U.S. is represented by two lithologically distinct successions: (1) a poorly fossiliferous, shallow-water, mixed carbonate-siliciclastic succession that is widespread across southern Nevada and southeastern California and (2) a highly fossiliferous, deeper water, fine-grained, siliciclastic succession in central Nevada and western Utah. The deeper water succession was deposited within the fault-controlled House Range Embayment and contains the P. atavus GSSP. Correlation of these disparate successions had been hampered by a lack of high-resolution biostratigraphic data, and limited chemostratigraphy and sequence stratigraphy. In this study, sequence-stratigraphic analysis indicates that the Condor Member of the Highland Peak Formation and the “mixed unit” of the Bonanza King Formation are the shallow-water platform equivalents of the basal Wheeler Formation encompassing the P. gibbus and lower P. atavus zones. The deepening event that is recorded in the P. gibbus Zone represents a major flooding surface that may be used as an important event marker for regional and global correlation. The overlying P. atavus GSSP, however, is within the later stage of transgression and may represent a globally synchronous event that can be correlated from platform to basin.     

Ecosystem Services from Keystone Species: Diversionary Seeding and Seed‐Caching Desert Rodents Can Enhance Indian Ricegrass Seedling Establishment

Seeds of Indian ricegrass (Achnatherum hymenoides), a native bunchgrass common to sandy soils on arid western rangelands, are naturally dispersed by seed‐caching rodent species, particularly Dipodomys spp. (kangaroo rats). These animals cache large quantities of seeds when mature seeds are available on or beneath plants and recover most of their caches for consumption during the remainder of the year. Unrecovered seeds in caches account for the vast majority of Indian ricegrass seedling recruitment. We applied three different densities of white millet (Panicum miliaceum) seeds as “diversionary foods” to plots at three Great Basin study sites in an attempt to reduce rodents' over‐winter cache recovery so that more Indian ricegrass seeds would remain in soil seedbanks and potentially establish new seedlings. One year after diversionary seed application, a moderate level of Indian ricegrass seedling recruitment occurred at two of our study sites in western Nevada, although there was no recruitment at the third site in eastern California. At both Nevada sites, the number of Indian ricegrass seedlings sampled along transects was significantly greater on all plots treated with diversionary seeds than on non‐seeded control plots. However, the density of diversionary seeds applied to plots had a marginally non‐significant effect on seedling recruitment, and it was not correlated with recruitment patterns among plots. Results suggest that application of a diversionary seed type that is preferred by seed‐caching rodents provides a promising passive restoration strategy for target plant species that are dispersed by these rodents.     

THE GEOGRAPHY OF MITOCHONDRIAL DNA VARIATION,POPULATION STRUCTURE,HYBRIDIZATION, AND SPECIES LIMITS IN THE FOX SPARROW (PASSERELLA ILIACA)

Geographic variation in mitochondrial DNA (mtDNA) restriction sites was studied in the fox sparrow (Passerella iliaca). Seventy-eight haplotypes were found. Haplotypes fall into four phylogeographic groups that correspond to groups defined by plumage characters. The geographic distribution of these four groups does not appear congruent with mtDNA patterns in other vertebrates. Within each group, there is little geographic variation in mtDNA restriction sites, although there is geographic variation in plumage coloration and body size. The evolution of mtDNA diversity in fox sparrows seems best explained by vicariant events rather than isolation by distance. The mtDNA evidence suggests that Passerella megarhyncha and Passerella schistacea, two nonsister taxa that occur in western North America, have independently undergone bottlenecks. Hybridization is limited between all pairs of taxa except P. megarhyncha and P. schistacea, where mtDNA evidence suggests a narrow contact zone along the interface of the Great Basin and Sierra Nevada/Cascades. Morphometric characters intergrade over a broader area, suggesting that different processes are responsible for the two gradients. The occurrence of limited backcrossing among taxa suggests that cytoplasmic-nuclear incompatibility is lacking. The number of biological species would range from one to four, depending on the degree of hybridization tolerated. The mtDNA and plumage characters suggest four phylogenetic species: P. iliaca, P. megarhyncha, P. unalaschcensis, and P. schistacea.     

Historical and contemporary distributions of carnivores in forests of the Sierra Nevada, California, USA

Aim Mammalian carnivores are considered particularly sensitive indicators of environmental change. Information on the distribution of carnivores from the early 1900s provides a unique opportunity to evaluate changes in their distributions over a 75‐year period during which the influence of human uses of forest resources in California greatly increased. We present information on the distributions of forest carnivores in the context of two of the most significant changes in the Sierra Nevada during this period: the expansion of human settlement and the reduction in mature forests by timber harvest. Methods We compare the historical and contemporary distributions of 10 taxa of mesocarnivores in the conifer forests of the Sierra Nevada and southern Cascade Range by contrasting the distribution of museum and fur harvest records from the early 1900s with the distribution of detections from baited track‐plate and camera surveys conducted from 1996 to 2002. A total of 344 sample units (6 track plates and 1 camera each) were distributed systematically across c. 3,000,000 ha area over a 7‐year period. Results Two species, the wolverine (Gulo gulo) and the red fox (Vulpes vulpes), present in the historical record for our survey area, were not detected during the contemporary surveys. The distributions of 3 species (fisher [Martespennanti], American marten [M. americana], and Virginia opossum [Didelphisvirginiana]) have substantially changed since the early 1900s. The distributions of fishers and martens, mature‐forest specialists, appeared to have decreased in the northern Sierra Nevada and southern Cascade region. A reputed gap in the current distribution of fishers was confirmed. We report for the first time evidence that the distribution of martens has become fragmented in the southern Cascades and northern Sierra Nevada. The opossum, an introduced marsupial, expanded its distribution in the Sierra Nevada significantly since it was introduced to the south‐central coast region of California in the 1930s. There did not appear to be any changes in the distributions of the species that were considered habitat generalists: gray fox (Urocyon cinereoargenteus), striped skunk (Mephitis mephitis), western spotted skunk (Spilogale gracilis), or black bear (Ursus americanus). Detections of raccoons (Procyon lotor) and badgers (Taxidea taxus) were too rare to evaluate. Contemporary surveys indicated that weasels (M. frenata and M. erminea) were distributed throughout the study area, but historical data were not available for comparison. Main conclusions Two species, the wolverine and Sierra Nevada red fox, were not detected in contemporary surveys and may be extirpated or in extremely low densities in the regions sampled. The distributions of the mature forest specialists (marten and fisher) appear to have changed more than the distributions of the forest generalists. This is most likely due to a combination of loss of mature forest habitat, residential development and the latent effects of commercial trapping. Biological characteristics of individual species, in combination with the effect of human activities, appear to have combined to affect the current distributions of carnivores in the Sierra Nevada. Periodic resampling of the distributions of carnivores in California, via remote detection methods, is an efficient means for monitoring the status of their populations.     

THE GEOGRAPHY OF MITOCHONDRIAL DNA VARIATION IN TWO SYMPATRIC SPARROWS

Geographic variation in mitochondrial DNA (mtDNA) restriction sites was studied in samples of two sympatric passerine birds, fox (Passerella iliaca) and song (Melospiza melodia) sparrows, collected at the same sites in the western United States. Different levels of variation and differentiation were observed in each species. In 46 fox sparrows taken at nine sites, five clones were observed, partitioned into two distinct east-west groups that meet at the Great Basin-Sierra Nevada interface; percent nucleotide divergence was 0.86 between groups and 0.08 within groups. An additional 43 individuals were examined using at least one of seven diagnostic endonucleases, and all supported the east-west groupings. Considering common mtDNA haplotypes as alleles, an F_ST of 0.50 was computed, which is an order of magnitude greater than that computed from allozyme comparisons (0.019); mtDNA analyses suggest little intergroup gene exchange. Compared to allozymic variation, analysis of mtDNA revealed a greater degree of population structuring and greater consistency with broad patterns of morphological variation. Fifteen clones were observed in 27 song sparrows taken at seven of the same sites at which fox sparrows were sampled; the percent nucleotide divergence averaged 0.27. There was no detectable geographic pattern to the variation, and no evidence of an east-west division as in the fox sparrow. However, the mosaic nature of mtDNA variation in song sparrows suggests limited gene exchange. Considering the 15 clones as alleles yielded an F_st of 0.24, which is reduced to 0.039 when corrected for sampling error. In spite of occupying the same geographic area, mtDNA analyses showed that the two species (or at least their mtDNA gene genealogies) have had different evolutionary histories.     

Johanneshowellia (Polygonaceae: Eriogonoideae), a new genus from the Intermountain West

A new genus ofPolygonaceae subfam.Eriogonoideae is established for what has long been known asEriogonum puberulum. NamedJohanneshowellia in honor of the late John Thomas Howell (1903–1994), a new combination,J. puberula, and a new species,J. crateriorum, are established. The common name Howell's-buckwheat is proposed for the group. The new genus differs from other members of the subfamily in having its involucral structure reduced to a spiral of four to seven bracts each of which is associated with a flower-bearing pedicel and a basal bractlet. In bud and early anthesis the outer two (rarely outer three) bracts may be partially connate, but typically become separate at full anthesis. The connate, ternate, foliar bracts at the base of the node act as a traditionalEriogonum-like involucre surrounding the branches of the inflorescence, the involucral bracts, and the flowers. Members of the new genus are found in the arid Intermountain West of the United States from Inyo Co., California, across Nevada to western Utah.     

KNOWN SECONDARY CONTACT AND RAPID GENE FLOW AMONG SUBSPECIES AND DIALECTS IN THE BROWN-HEADED COWBIRD

We analyze geographic variation in morphology for Sierra Nevadan populations of Brown-headed Cowbirds (Molothrus ater) in relation to two levels of geographic structure of populations: 1) subspecies and 2) vocal dialects. Two morphologically distinct subspecies occupy opposite slopes of the Sierra Nevada: M. a artemisiae on the east slope is larger than M. a. obscurus on the west slope, and its juveniles have predominantly white versus yellow rictal (bill) flanges. Populations of obscurus moved into California from the lower Colorado River around 1900 and invaded the western Sierra during the 1930's. A relatively constant type of flight whistle occurs in obscurus populations up to 700 km apart, but east-slope artemisiae are divided into many distinct dialects. The means of seven morphological measurements and of principal component 1 (i.e., body size) for 2,287 individuals show similar clinal patterns for adult males, yearling males, and females over a 60-km north–south transect along the eastern Sierra Nevada: large sizes occur at the southernmost study site at Bishop, decrease clinally to the north to Mammoth Lakes, and then increase clinally to the north from Mammoth Lakes to the northernmost site at Lee Vining. This reversal in cline slope is reiterated for variation in the frequency of white-flanged juveniles. Our data do not support adaptive explanations for the clines. Rather, the most parsimonious explanation is that there has been flow of obscurus genes into artemisiae from the west slope across the crest of the Sierra Nevada into the Mammoth Lakes area. Concordantly, the Sierran crest at Mammoth Lakes is considerably lower than any other point within about 80 km to the north or 180 km to the south. Two other findings strongly support this interpretation. First, wing lengths of our longest-winged samples (at Bishop and Lee Vining) are significantly shorter than those of cowbirds collected in the same region between 1912 and 1922. Second, the wing lengths of Mammoth Lakes adult males and females during 1978–1981 are significantly larger than those of the 1982–1985 period. This putative hybridization must have been rapid, as there have been fewer than 50 years since secondary contact could have occurred. Calculation of the gene-flow parameter Ι of Endler (1977) indicates that the gene-flow rate reported here is higher than for nearly all of the species he surveyed. This gene flow occurs between two subspecies with different flight whistles and across several cowbird flight-whistle dialects within artemisiae. Therefore, vocal differences among these dialects do not appear to be a strong deterrent to gene flow.     

Evaluating Sierra Nevada Yellow-Legged Frog Distribution Using Environmental DNA

Genetic tools that identify species from trace DNA samples could supplement traditional survey methods to clarify distributional limits of rare species. For species with legal habitat protection, elevational limits of distributions are used to determine where management actions may affect endangered species. The endangered Sierra Nevada yellow-legged frog (Rana sierrae) generally is found down to 1,370 m, but in the Plumas National Forest, California, USA, there are a number of historical records below this elevation, resulting in protections extending to 1,067 m. This species is phenotypically similar to the foothill yellow-legged frog (R. boylii), with which it occasionally hybridizes. We used a combination of genetic methods to investigate the fine-scale distribution of the Sierra Nevada yellow-legged frog in the Plumas National Forest. We collected and analyzed environmental DNA (eDNA) samples from all accessible lower elevation sites with records of Sierra Nevada yellow-legged frog (n = 17) and swabbed 220 individuals for genetic identification from 2016–2018 to clarify the distribution of this endangered species. We created a climatic suitability model using the validated Sierra Nevada yellow-legged frog records and current (1970–2000) climate models to assess additional highly suitable localities for Sierra Nevada yellow-legged frog presence using eDNA capture. We did not confirm detection of Sierra Nevada yellow-legged frog eDNA at any historical sites and identified all swabbed individuals from below 1,370 m (n = 144) as foothill yellow-legged frogs. We located a new Sierra Nevada yellow-legged frog site (at 1,919 m) during surveys guided by the climatic suitability model. It does not appear after extensive eDNA and genetic sampling that the Sierra Nevada yellow-legged frog occurs below 1,370 m in this portion of their range at present. Our results show that eDNA sampling can be used as an effective management tool to evaluate historical locations and previously unknown suitable localities for current presence of a species of interest. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.     

MATING SYSTEM IN NATURAL POPULATIONS OF JEFFREY PINE

The mating system and allozyme variation at 20 loci in three Klamath Mountains and two Sierra Nevada populations of Jeffrey pine (Pinus jeffreyi Grev. & Balf.) were investigated. On average, multilocus estimates of the proportion of viable progeny due to outcrossing (t_m) were high in all populations (mean t_m = 0.935, range 0.881 to 0.971). Despite differences in stand structure, t_m did not differ (P > 0.05) between the Klamath (mean t_m = 0.933) and Sierra Nevada (mean t_m = 0.937) populations. At all but one locus in one population and at two in another, genotype frequencies fit (P > 0.05) Hardy-Weinberg expectations. Mean estimates of observed heterozygosity in Klamath (0.182) and Sierra Nevada (0.327) populations were comparable to values reported for other conifers.     

Landscape-Level Assessment of Brood Rearing Habitat for Greater Sage-Grouse in Nevada

Abstract: Loss of quality brood rearing habitat, resulting in reduced chick growth and poor recruitment, is one mechanism associated with decline of greater sage-grouse (Centrocercus urophasianus) populations. Low chick survival rates are typically attributed to poor-quality brood rearing habitat. Models that delineate suitability of sage-grouse nesting or brood rearing habitat at the landscape scale can provide key insights into the relationship between sage-grouse and the environment, allowing managers to identify and prioritize habitats for protection or restoration. We used Southwest Regional Gap landcover types to identify early and late greater sage-grouse brood rearing in east-central Nevada. We conducted an Ecological Niche Factor Analysis to 1) examine the effect these landcover types and other ecogeographical variables have on sage-grouse selection of brood rearing habitat, and 2) generate landscape-scale suitability maps. We also evaluated if incorporating a fitness component (brood survival) in landscape spatial analyses of habitat quality influenced our assessment of habitat suitability. Because 36% of our 6,500-km² study area was identified as early brood rearing habitat, we believe this habitat may not be limiting greater sage-grouse populations in east-central Nevada, USA, at least in wet years. We found strong selection for particular landcover types (e.g., higher elevation, moist sites with riparian shrubs or montane sagebrush) during late brood rearing. Late brood rearing habitat on which broods were successfully reared represented only 2.8% of the study area and had a restricted distribution, suggesting the potential that such habitat could limit sage-grouse populations in east-central Nevada.     

Collections from the mesophytic zone off Bermuda reveal three species of Kallymeniaceae (Gigartinales,Rhodophyta) in genera with transoceanic distributions

A molecular survey of red algae collected by technical divers and submersibles from 90 m in the mesophotic zone off the coast of Bermuda revealed three species assignable to the Kallymeniaceae. Two of the species are representative of recently described genera centered in the western Pacific in Australia and New Zealand, Austrokallymenia and Psaromenia and the third from the Mediterranean Sea and the eastern Atlantic, Nothokallymenia. A phylogenetic analysis of concatenated mitochondrial (COI‐5P) and chloroplast (rbcL) genes, as well as morphological characteristics, revealed that two are shown to be new species with distant closest relatives (N. erosa and Psaromenia septentrionalis), while the third represents a deep water western Atlantic species now moved to an Australasian genus (A. westii).     

Analysis of the ionization constants and heats of ionization of reduced and oxidized horse heart cytochrome c

Simultaneous curve fitting for the ionization parameters of oxidized and reduced horse heart cytochrome c in 0.15M KCl and 20°C yields values for the ionization constants (as pK′) and the heats of ionization (ΔH_i) which can reconstruct either the potentiometric or thermal titration curves. Reduced cytochrome c requires 8 sets of groups, whereas oxidized cytochrome c requires 10 sets of groups. The additional groups in the oxidized preparation appear to involve the ferriheme (pK′, 9.25; ΔH_i, 13.7 kcal/mol) and a tyrosine (pK′ ? 10.24) that is not present in the reduced form. The potentiometric and thermal difference curves (reduced – oxidized) involve the appearance of 17 kcal/mol centered at pH 9.7 and 5.8 kcal/mol centered at pH 4.9. The carboxyl groups in both species appear to be normal for the hydrogen-bonded form. Only one histidine has normal ionization properties (pK′, 6.7; ΔH_i, 7.5 kcal/mol), as do 17 of the lysine residues (pK′, 10.8; ΔH_i, 11.5 kcal/mol).     

Re-evaluation of morphological and chloroplast DNA variation in Juniperus osteosperma Hook and Juniperus occidentalis Torr. Little (Cupressaceae) and their putative hybrids

Relationships between variation in cpDNA and morphology were examined to test the hypothesis of hybridization between Juniperus osteosperma and Juniperus occidentalis. Principal components analysis of 11 taxonomically-important characters distinguished individuals collected from eastern Nevada and Utah from those of southern Oregon. In contrast, many individuals collected from sympatric populations in western Nevada were morphologically intermediate to these two groups. Comparative sequencing of the trnS-trnG intergenic spacer and restriction site analysis of a trnL-trnF PCR product revealed nine haplotypes, and examination of haplotype-morphology associations allowed identification of species-specific genetic markers as well as those that transcend species limits. The confinement of morphological intermediacy and transcendent haplotypes to zones of sympatry, the discovery of haplotypes characteristic of one species in the morphological background of the other, and determination that the character intermediacy encountered is of the type expected under interspecific gene flow are marshaled in support of introgressive hybridization between J. osteosperma and J. occidentalis.     

Endemism,palaeoendemism and migration: the case for the ‘European endemic’, Mallomonas intermedia

The Synurophyceae is a well-supported clade of ecologically important heterokont algae found largely in freshwater planktonic habitats worldwide, whose members have cell coverings consisting of species-specific siliceous scales overlapped in a highly organized manner. Many synurophytes have been described as endemic and are found only in specific regions of the world. A thriving population of the European endemic, Mallomonas intermedia, was discovered in a remote desert pond situated in the Virgin Valley, Nevada, USA and in a stratigraphic sequence from the middle Eocene fossil locality known as Horsefly in British Columbia, Canada. Both North American finds were closely compared with populations from Europe, confirming the identifications. Before these discoveries, this species was recorded from numerous waterbodies exclusively in Europe, but was lacking from hundreds of sites examined from other continents. Its presence in western North America during the warm middle Eocene confirms that historically this species had a significantly wider distribution and may be best classified as a palaeoendemic. Additional species uncovered from a second fossil locality that are closely related to M. intermedia further support the presence of this lineage in North America during the Eocene. The living population in northern Nevada presents an enigma. Does this remote desert population represent a remnant population that has gone undetected until now, or is it a recent arrival from an unknown region by an unknown vector?     

POLLEN OF BOERLAGIODENDRON: A UNIQUE TYPE IN THE ARALIACEAE

The pollen of Boerlagiodendron, one of the most distinct genera of Araliaceae, is unique within the family in its remarkable degree of differentiation of sexine into pertectate and intectate patterns and in its reduced apertures. The unexpanded mesocolpia and the inconspicuous apertures have apparently caused misinterpretation of the pollen morphology of B. pectinatum in recent literature. A comparative study of several pollen features, together with the meristic characters of carpels and stamens, has demonstrated some significant correlations among them. It appears that the origin of the genus may have been centered around the New Guinea and Solomons areas.