An effective method for ecosystem‐scale manipulation of bird abundance and species richness

Manipulation experiments are a cornerstone of ecological research, but can be logistically challenging to execute—particularly when they are intended to isolate the ecological role of large, vagile species, like birds. Despite indirect evidence that birds are influential in many ecosystems, large‐scale, multi‐year bird manipulation experiments are rare. When these studies are conducted, they are typically realized with caged or netted exclosures, an approach that can be expensive, risky for wildlife, and difficult to maintain. In cases where caged exclosures are not appropriate, alternate approaches are needed to allow rigorous empirical studies on the ecological role of birds. Here, we present and validate a method for experimentally increasing the abundance and richness of birds at the scale of entire aquatic ecosystems. Unlike bird exclusion, this approach is experimentally tractable, appealing to land managers, and possible to deploy over large spatial scales. We tested the efficacy of our approach for increasing bird abundance and species richness at 16 central California ponds. Based on bird visitation data obtained by summer camera trapping, our approach significantly increased bird species richness and abundance at manipulated ponds compared to control ponds. Attractant treatments mitigated the negative effects of a major drought on bird species richness and generated a near doubling of bird abundance in the presence of attractants. Treatments had no effect on most mammal species, with the exception of ground squirrels, which increased in abundance in the presence of attractants. These results suggest that attractants are effective in increasing bird abundance and richness. We encourage researchers to consider this approach for experimentally isolating the ecological role of birds in aquatic and open terrestrial ecosystems, especially in cases where cost or logistical constraints preclude the use of caged or netted exclosures.     

Toward a better understanding of the "Transverse Range break": lineage diversification in southern California

The Transverse Ranges in southern California have been identified as having a prominent phylogeographic role. Numerous studies have identified distinct north-south and/or east-west lineage breaks involving the Transverse Ranges. However, in evaluating their findings, most authors have regarded this complex system somewhat simplistically. In this study we more deeply investigate these breaks using two approaches: first we examine the phylogeographic history of Sepedophilus castaneus (Coleoptera: Staphylinidae) and then implement a comparative phylogeography approach applying Brooks parsimony analysis to the topologies of nine additional taxa. Phylogenetic analysis, nested clade analysis, and AMOVAs for S. castaneus agree that there is a major lineage break between the eastern and western Transverse Ranges, localized between the Sierra Pelona and the San Gabriel Mountains. The comparative phylogeographic analysis supports a generally strong concordance of area relationships with geographic proximity. It is notable, however, that the Transverse Ranges as a group do not show phylogenetic cohesion, but rather they are split into three main regions: an eastern region (San Gabriel, San Bernardino, and San Jacinto Mountains), a central region (central Transverse Ranges and Sierra Pelona) that is often grouped with the Tehachapi and Sierra Nevada populations, and a western region (northwestern Transverse Ranges and Santa Ynez Mountains) that is consistently grouped with coast range areas to the north. The lineage break between east and west Transverse Ranges is attributable to the presence of a marine embayment in what is now the Santa Clara River valley 5-2.5 million years ago.     

Blooms of Pseudo-nitzschia and domoic acid in the San Pedro Channel and Los Angeles harbor areas of the Southern California Bight, 2003–2004

Abundances of Pseudo-nitzschia spp. and concentrations of particulate domoic acid (DA) were determined in the Southern California Bight (SCB) along the coasts of Los Angeles and Orange Counties during spring and summer of 2003 and 2004. At least 1500 km² were affected by a toxic event in May/June of 2003 when some of the highest particulate DA concentrations reported for US coastal waters were measured inside the Los Angeles harbor (12.7 μg DA L⁻¹). Particulate DA levels were an order of magnitude lower in spring of 2004 (February and March), but DA concentrations per cell at several sampling stations during 2004 exceeded previously reported maxima for natural populations of Pseudo-nitzschia (mean = 24 pg DA cell⁻¹, range = 0–117 pg DA cell⁻¹). Pseudo-nitzschia australis dominated the Pseudo-nitzschia assemblage in spring 2004. Overall, DA-poisoning was implicated in >1400 mammal stranding incidents within the SCB during 2003 and 2004. Ancillary physical and chemical data obtained during our regional surveys in 2004 revealed that Pseudo-nitzschia abundances, particulate DA and cellular DA concentrations were inversely correlated with concentrations of silicic acid, nitrogen and phosphate, and to specific nutrient ratios. Particulate DA was detected in sediment traps deployed at 550 and 800 m depth during spring of 2004 (0.29–7.6 μg DA (g sediment dry weight)⁻¹). The highest DA concentration in the traps was measured within 1 week of dramatic decreases in the abundances of Pseudo-nitzschia in surface waters. To our knowledge these are the deepest sediment trap collections from which DA has been detected. Sinking of the spring Pseudo-nitzschia bloom may constitute a potentially important link between DA production in surface waters and benthic communities in the coastal ocean near Los Angeles. Our study indicates that toxic blooms of Pseudo-nitzschia are a recurring phenomenon along one of the most densely populated coastal stretches of the SCB and that the severity and magnitude of these events can be comparable to or greater than these events in other geographical regions affected by domoic acid.     

Loureirophonte psammophila,a new species of Laophontidae T. Scott, 1904 (Copepoda: Harpacticoida) from Baja California,Mexico

Loureirophonte psammophila n. sp. was collected from coarse sediments of a beach near La Paz, Baja California, Mexico. The species belongs to the subterranea-group as defined by Fiers (1993). It differs from the other representative of the group, L. subterranea (Lang, 1965) in the presence of an outer dentiform process on 2nd segment of the antennula, the chaetotaxy of P.2–P.5 and the 1-segmented male endopodite P.4. A map with the distribution of the eleven species known so far is provided.     

Phylogeography of the California mountain kingsnake, Lampropeltis zonata (Colubridae)

The phylogeography of the California mountain kingsnake, Lampropeltis zonata, was studied using mitochondrial DNA sequences from specimens belonging to the seven recognized subspecies and collected throughout the range of the species. Maximum parsimony and maximum likelihood methods identified a basal split within L. zonata that corresponds to southern and northern segments of its distribution. The southern clade is composed of populations from southern California (USA) and northern Baja California, Mexico. The northern clade is divided into two subclades, a 'coastal' subclade, consisting of populations from the central coast of California and the southern Sierra Nevada Mountains of eastern California, and a 'northeastern' subclade, mainly comprised of populations north of the San Francisco Bay and from the majority of the Sierra Nevada. We suggest that past inland seaways in southwestern California and the embayment of central California constituted barriers to gene flow that resulted in the two deepest divergences within L. zonata. Throughout its evolutionary history, the northern clade apparently has undergone instances of range contraction, isolation, differentiation, and then expansion and secondary contact. Examination of colour pattern variation in 321 living and preserved specimens indicated that the two main colour pattern characters used to define the subspecies of L. zonata are so variable that they cannot be reliably used to differentiate taxonomic units within this complex, which calls into question the recognition of seven geographical races of this snake.     

Acarologic risk of exposure to Borrelia burgdorferi spirochaetes: long-term evaluations in north-western California, with implications for Lyme borreliosis risk-assessment models

Over a 5-year period (1997-2001) the population densities of Ixodes pacificus Cooley & Kohls (Acari: Ixodidae) nymphs infected with spirochaetes of Borrelia burgdorferi sensu lato (s.l.) were evaluated in areas of 2000 ha at two localities (CHR, nine sites; HREC, seven sites) 25 km apart in Mendocino County, north-western California. The 5-year median density of infected nymphs was significantly higher at CHR than at HREC (0.51 vs. 0.09 per 100 m(2) and site-specific yearly densities exceeding one infected nymph per 100 m2 were 10-fold more likely to occur at CHR than at HREC. The importance of long-term data in acarologic risk assessment was demonstrated by significantly higher median yearly densities of infected nymphs at CHR from 1997 to 1999, whereas both areas had similar densities during 2000-2001. Overall, the causative agent of Lyme borreliosis in North America, B. burgdorferi Johnson et al. sensu stricto (s.s.) accounted for 76% of 46 genetically characterized B. burgdorferi s.l. infections from I. pacificus nymphs. Tremendous variability in acarologic risk was recorded within both areas: yearly densities of infected nymphs varied 11-97-fold between sites at CHR and 8-30-fold at HREC. Part of this variation could be explained by environmental traits, most notably deer usage. However, correlations between environmental factors and density of infected nymphs (for CHR and HREC combined) did not necessarily apply when these areas were considered separately. Thus, a Lyme borreliosis ecology model developed in one of these areas needs testing in the other area.     

Cloning and tissue distribution of the human B3GALT7 gene, a member of the β1,3-Glycosyltransferase family

We report here the cloning and tissue distribution of the human B3GALT7 gene, a member of the beta1,3-Glycosyltransferase family, structurally related to the beta1,3-Galactosyltransferase family and beta1,3- N -acetylglucosaminyltransferase family, isolated from a human lung cDNA library. B3GALT7 is mapped to chromosome 19q13.2 by browsing the UCSC genomic database. It contains an ORF with length of 1191bp, encoding a protein with a signal peptide sequence and galactosyl-T domain, and its molecular weight and isoelectric point is predicted to be 43.3 kDa and 8.67 respectively. The molecular weight of the protein when expressed in E. coli corresponded to that expected. Northern blotting showed that B3GALT7 was highly expressed in lung, throat and ileum, whereas the expression level was low in tongue, breast, uteri, testis. In addition, it was also demonstrated that B3GALT7 is differentially transcribed in human tumor cell lines.     

Ion permeation of pores in model membranes: selectivity,fluctuations and the role of surface charge

Fluctuation of surface charge on pore walls provides a realistic, additional mechanism for generating fluctuation of ionic current and ionic selectivity in narrow pores.     

Edaphic races and phylogenetic taxa in the Lasthenia californica complex (Asteraceae: Heliantheae): an hypothesis of parallel evolution

Lasthenia californica sensu Ornduff consists of two races that differ in their flavonoid pigments and edaphic tolerances. Recent phylogenetic studies of Lasthenia have revealed that members of L. californica sensu Ornduff belong to two phylogenetic species. The relationship of the edaphic races to these new species and to each other is the focus of this study. Characterization of flavonoid profiles and phylogenetic placement of 33 populations demonstrates that races and phylogenetic taxa are not concordant, suggesting that one or both edaphic races evolved in parallel in the two clades. We hypothesize an edaphically linked ecological role for flavonoid differences that first revealed the existence of two races.