The coastal salt marshes of California and Baja California

A comparative study of the North American salt marshes between Magdalena Plain (Baja California, 24° N)_and the north of San Francisco (California 38° N) is made in order to establish relationships between floristic and zonal gradients. The sigmatistic-phytosociological method along with Average Linkage Clustering are used to describe the zonation of these salt marshes and to define the optimum zone of several halophilous plants and communities.Abbreviations (As) Arthrocnemum subterminalis - (Ds) Distichlis spicata - (Fg) Frankenia salina - (Jc) Jaumea carnosa - (MI) Monanthochloe littoralis - (S1) Sarcocornia pacifica, prostrate biotype - (S2) Sarcocornia pacifica, erect biotype - (Sp) Spartina foliosa     

Frond elongation rates of shallow waterMacrocystis pyrifera (L.) Ag. In northern Baja California,Mexico

Macrocystis pyrifera (L.) Ag.frond elongation rates were measured during autumn-winter, spring and summer in a shallow water (7.5 m depth) kelp bed in Bahía Papalote, northern Baja California. Frond elongation was maximum during spring and minimum during winter. Frond growth was significantly correlated with solar radiation, and was highest in the smallest size fronds (0–2 m). Average frond elongation rate varied between 0.3–11% d^–1 during the study period. The relationship between average frond length and elongation rate followed an exponential curve with a negative slope during autumn-winter and summer, but was best described by a straight line during spring. Standard growth rates were obtained by a graphic method. Standard growth rates had intermediate values between those reported for southern California and southern Baja California.M. pyrifera growth cycle shows a different trend from what has been previously reported.     

A new species of Sanicula L. (Umbelliferae/Apiaceae) endemic to Baja California, Mexico

A new species of the genusSanicula (sect.Sanicoria) endemic to the southern Sierra Juárez of Baja California, Mexico, is described and illustrated.Sanicula moranii resemblesS. deserticola andS. bipinnatifida, but has thicker basal leaves, with broader petioles and rachises, and shorter fruit prickles that are confined to the apical part of the mericarps. The taxonomic relationships of these species are discussed, along with aspects of their distribution and habitat.

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Resumen  Una neuva especie del géneroSanicula (secciónSanicoria) endémica de la Sierra Juárez de Baja California, México, es descrita e ilustrada.Sanicula moranii presenta similitud conS. deserticola yS. bipinnatifida, no obstante tiene gruesas hojas basales con pecíolos y raquis anchos, y espínulas del fruto más cortas que se distribuyen únicamente en la parte apical de los mericarpos. Además, se comentan las relaciones taxonómicas de las tres especies, así como algunos aspectos de sus distribuciones y hábitats.

     

Two new Marina (Leguminosae) from the southern Baja California peninsula, Mexico

Marina victoriae andM. brevis are newly described species from the southern Baja California peninsula, Mexico. The former is a perennial herb locally abundant in the eroded hillsides at the foothills of Sierra de la Victoria, where an oak woodland and a dry tropical forest meet. The latter is an elusive ephemeral inhabiting a narrow strip of land between the mangroves and the desert scrub on an island in the Gulf of California. These two new species belong to the seriesChrysorrhizae, a group native to the Gulf of California basin.     

Genetic isolation and evolutionary history of oases populations of the Baja California killifish,Fundulus lima

The Baja California killifish, Fundulus lima, is found in six desert oases of the southern Baja California Peninsula, Mexico. The recent introduction of exotic fishes, particularly redbelly tilapia, have impacted the ecology of Fundulus lima such that it is now endangered. Plans of relocating F. lima to bodies of freshwater that are free of exotics have been proposed, however little is know about the genetic identity of the current populations. In this study, we examined the mitochondrial control region of F. lima samples from 4 oases, and in addition, compared these samples to their sister species, the California killifish F.␣parvipinnis. Using a combination of phylogenetic and coalescent approaches, we were able to determine that the two subspecies of the California killifish, F. p.␣brevis, and F. p. parvipinnis, and F. lima form an unresolved trichotomy that diverged between 200,000 years and 400,000 years ago. The one F. lima individual that we were able to collect in the southernmost oasis grouped with the southern subspecies of the California killifish, F. parvipinnis brevis. In contrast, we found that the 3 northern oases grouped together in a “Fundulus lima” clade. Each oasis is genetically distinct, yet there is no evidence of a␣marked genetic bottleneck in any populations (Haplotype diversity between 0.5 and 0.8). Future relocation plans will therefore need to be done cautiously to preserve the genetic identity of the original populations.     

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.     

Coccolithophorids from the west coast of Baja California, Mexico

Studies on coccolithophorids in Mexico are rather scarce, probably due to the use of traditional methods for studying marine phytoplankton (e.g. collection, preservation and analysis). This is the first study of the coccolithophorid flora from west coast of Baja California, Mexico. Bottle samples (4 l) were taken at various depths (5, 25 and 50 m), at fixed stations located on perpendicular transects along the west coast of Baja California, considering three different zones: North, Central and South. A total of 32 samples were studied by optical and scanning electron microscopy, yielding 24 taxa identified (17 species and 5 nominal varieties, plus 2 different varieties). The coccolithophorid assemblages are considered subtropical and coastal (with many cosmopolitan taxa). Emiliania huxleyi and Gephyrocapsa oceanica were the most abundant (relative abundance) and widespread species in the study area. We report 15 new records for the Mexican Pacific. The zonal and vertical distribution of some taxa are briefly discussed, as well as the taxonomy of Rhabdosphaera claviger, Helicosphaera carteri, H. hyalina and related taxa.     

Seasonality of mycorrhizae in coastal sand dunes of Baja California

 Populations of arbuscular mycorrhizal fungi were estimated from spores associated with seven plant species in coastal dunes at El Socorro, near Ensenada, Baja California, during six months in 1992. The seasonal patterns of percent root colonization were also described in the same species during the wet season (January–March) and the dry season (April–July). Comparisons were made between the pioneer species (Abronia maritima) in the mobile dunes and six species (Abronia umbellata, Atriplex julacea, Camissonia californica, Haplopappus venetus, Helianthus niveus and Lotus spp.) in the fixed dunes. Mycorrhizal colonization in Abronia maritima was slight (<1%) and we observed few spores (<1/g soil). All of the species in the fixed dune formed mycorrhizae with up to 80% colonization in early summer, and no more than 4 spores/g soil by late summer. The highest percentages of total colonization and abundance of spores did not coincide temporally for any of the seven species, but the percentages were higher in summer than in spring. Arbuscules were more abundant when the soil was moist, and vesicles more abundant when it was dry. Accepted: 16 August 1995     

Vicariance and dispersal across Baja California in disjunct marine fish populations

Abstract.— Population disjunctions, as a first step toward complete allopatry, present an interesting situation to study incipient speciation. The geological formation of the Baja California Peninsula currently divides 19 species of fish into disjunct populations that are found on its Pacific Coast and in the northern part of the Gulf of California (also called the Sea of Cortez), but are absent from the Cape (Cabo San Lucas) region. We studied the genetic makeup of disjunct populations for 12 of these 19 fish species. Phylogeographic patterns for the 12 species can be separated into two major classes: a first group (eight species) showed reciprocal monophyly and high genetic divergence between disjunct populations. A second group (four species) displayed what appeared to be panmictic populations. Population structure between Pacific Coast populations, across the Punta Eugenia biogeographic boundary, was also evaluated. While dispersal potential (inferred by pelagic larval duration) was a poor predictor of population structure between Gulf of California and Pacific populations, we found that population genetic subdivision along the Pacific Coast at Punta Eugenia was always positively correlated with differentiation between Pacific and Gulf of California populations. Vicariant events, ongoing gene flow, and ecological characteristics played essential roles in shaping the population structures observed in this study.     

Tempo and mode of speciation in the Baja California disjunct fish species Anisotremus davidsonii

The Baja California region provides a natural setting for studying the early mechanisms of allopatric speciation in marine systems. Disjunct fish populations from several species that occur in the northern Gulf of California and northern Pacific coast of Baja California, but are absent from its southern shores, were previously shown to be genetically isolated, making them excellent candidates for studying allopatry. In addition, one of these species, the sargo Anisotremus davidsonii, has two pairs of congeneric Panamic trans-isthmian geminate species that allow for internal molecular clock calibration. Phylogeographic and demographic approaches based on mitochondrial (cytochrome b) and nuclear (S7 ribosomal protein) sequences showed that A. davidsonii entered the gulf from the south, and later colonized the Pacific coast, approximately 0.6-0.16 million years ago. Pacific coast colonization may have used a route either around the southern cape of Baja California or across the peninsula through a natural seaway. However, while several seaways have been described from different geological times, none matches the dates of population disjunction, yet much geological work remains to be done in that area. At the present time, there is no evidence for dispersal around the southern tip of the Baja California Peninsula. Signatures of incipient allopatric speciation were observed, such as the reciprocal monophyly of disjunct populations for the mitochondrial marker. However, other characteristics were lacking, such as a strong difference in divergence and coalescence times. Taken together, these results suggest that disjunct populations of A. davidsonii may be consistent with the earliest stages of allopatric speciation.     

Mycorrhizal characterization of the boojum tree, <Emphasis Type="Italic">Fouquieria columnaris</Emphasis>, an endemic ancient tree from the Baja California Peninsula,Mexico

The mycorrhizal association with the boojum tree, Fouquieria columnaris (=Idria columnaris), was studied. This unusual tree is almost exclusively endemic to granite and volcanic soils in highly arid areas of the Baja California Peninsula of Mexico. Soil and root samples from ten sites, covering the extent of geographic distribution of the tree on the peninsula, were analyzed. The roots of the boojum tree contained all structures of an arbuscular mycorrhizal (AM) association. Morphologically different species, 23 in number, were identified in close vicinity to the boojum tree indicating that F. columnaris is associated with a high number of AM species of several AM genera and families.     

Deep genealogies and the mid-peninsular seaway of Baja California

Geological forces and long-term climate changes can have profound effects on species. Such effects may be manifested in the pattern and magnitude of genealogical diversity, as revealed by mitochondrial DNA (mtDNA) lineages. The relative importance of the different forces on a regional biota must be evaluated along with a good understanding of geological and climatological history. The peninsula of Baja California of north-western Mexico is one area where both geology and climate have affected the historical biogeography of the regional biota. Molecular studies based on the genealogical relationships among mtDNA lineages have contributed greatly towards elucidating the historical biogeography of Baja California. Perhaps most noticeably, numerous concordant breaks in mtDNA genealogies half-way along the peninsula suggest a vicariant history in which the mid-peninsula was temporarily submerged. This vicariant explanation has recently been criticized, as no conclusive geological evidence exists for a continuous submergence of the mid-peninsula. As an alternative, a scenario based on climatological factors has been suggested. Here we discuss the validity of the hypothesized mid-peninsular vicariance event and the climate-based alternative in explaining the concordant genealogical breaks. We argue that, despite the significant changes in climate brought about by the glacial cycles throughout the Quaternary, a vicariant history involving a mid-peninsular seaway remains the most parsimonious explanation of the observed patterns in mtDNA genealogies.     

Heavy Metal Accumulation in Four Species of Sea Turtles from the Baja California Peninsula, Mexico

Heavy metals were assessed in four species of sea turtles from the Baja California Peninsula, Mexico, representing the first report of heavy metal concentrations in tissues of post-yearling sea turtles from the Eastern Pacific. Concentrations of Cd measured in C. mydas kidney (653 μg/g dry wt) were the highest ever reported for any sea turtle species. Cd accumulated preferentially in kidney and the ratios of kidney to liver Cd in Baja California turtles were among the highest reported for sea turtles globally. Zn, Ni, and Mn concentrations were also significantly higher in kidney than other tissues, while Cu and Fe were greatest in liver, and all metals were lowest in muscle. With the exception of one value (69.9 μg/g in kidney of C. caretta), Pb was low in all tissues from Baja California. In comparisons across species, kidney of C. mydas had greater Zn and Ni concentrations as compared to other species, although there was no difference in liver metal levels among the species. Positive correlations were detected in the concentrations of Cd, Cu and Ni with the straight carapace length of C. caretta.     

Shrubland formations and associations in mediterranean-desert transitional zones of northwestern Baja California

The area between Ensenada and EI Rosario (Baja California, Mexico) has long been considered as a transitional zone in which two great ecoclimatic regions (Mediterranean and Tropical-Desert) overlap. The floristic and biotypical diversity of this area was evaluated by analyzing its shrubland formations from a phytosociological point of view. This phytosociological study, carried out according to the Braun-Blanquet method and supported by cluster analysis, describes sixteen shrubland associations from Northwestern Baja California.Floristic diversity of the transitional zone was evaluated using two indices, endemic value (EV) and endemic community value (ECV), which are related to the degree of endemism in the flora and plant associations. The phytosociological analysis showed that the high number of shrubland associations found in this area reflected its transitional character. The closer the associations are to the transitional zone, the higher their biotypical and floristic diversity.Abbreviations ADE Adenostoma fasciculatum - AES Fraxinus trifoliata-Aesculus parryi - BER Bergerocactus emoryi-Agave shawii - DES Echinocereus engelmannii-Agave deserti - ENC Viguiera deltoidea-Encelia asperifolia - EUR Eurotia lanata-Yucca schidigera - FOU Agave cerulata-Fouquieria columnaris - FRA Atriplex julacea-Frankenia palmeri - HYM Baccharis glutinosa-Hymenoclea monogyra - KEC Clematis lasiantha-Keckiella antirrhinoides - LAR Ambrosia chenopodifolia-Larrea tridentata - LYC Ephedra californica-Lycium brevipes - MAH Malosma laurina-Heteromeles arbutifolia - MUN Salvia munzii-Artemisia californica - ROS Rosa minutifolia-Aesculus parryi - SAL Salvia apiana-Viguiera laciniata     

Characterization of seven polymorphic microsatellite loci in the Baja California endemic black‐tailed brush lizard Urosaurus nigricaudus

Seven microsatellite loci were developed for the Baja California endemic black‐tailed brush lizard Urosaurus nigricaudus, using an enriched genomic DNA library. All loci were polymorphic and overall presented high levels of variation. Number of alleles ranged from five to 16 (average 12.14), and observed heterozygosities from 0.535 to 0.923 (average 0.752). Cross‐species amplification was successful and polymorphism was detected for all the loci using the congeners Urosaurus lahtelai and Urosaurus ornatus. These markers will be useful to study fragmented populations of U. nigricaudus on agricultural landscape of the Baja California Peninsula.     

Characterization of nine microsatellite loci on endemic kangaroo rats Dipodomys simulans peninsularis from southern Baja California Peninsula

Nine polymorphic microsatellite loci were isolated to investigate the effects of habitat fragmentation on gene flow and genetic variation of the peninsular kangaroo rat Dipodomys simulans peninsularis on agricultural landscape from the Baja California Peninsula. The markers had an average of 9.11 alleles per locus (range 2–14), with mean observed and expected heterozygosities 0.646 (range 0.333–0.900) and 0.788 (range 0.284–0.932), respectively. No evidence of linkage disequilibrium was found across pairs of loci, and only one locus exhibited evidence of null alleles.     

Population genetic structure of annual and perennial populations of Zostera marina L. along the Pacific coast of Baja California and the Gulf of California

The Baja California peninsula represents a biogeographical boundary contributing to regional differentiation among populations of marine animals. We investigated the genetic characteristics of perennial and annual populations of the marine angiosperm, Zostera marina, along the Pacific coast of Baja California and in the Gulf of California, respectively. Populations of Z. marina from five coastal lagoons along the Pacific coast and four sites in the Gulf of California were studied using nine microsatellite loci. Analyses of variance revealed significant interregional differentiation, but no subregional differentiation. Significant spatial differentiation, assessed using θ_ST values, was observed among all populations within the two regions. Z. marina populations along the Pacific coast are separated by more than 220 km and had the greatest θ_ST (0.13–0.28) values, suggesting restricted gene flow. In contrast, lower but still significant genetic differentiation was observed among populations within the Gulf of California (θ_ST = 0.04–0.18), even though populations are separated by more than 250 km. This suggests higher levels of gene flow among Gulf of California populations relative to Pacific coast populations. Direction of gene flow was predominantly southward among Pacific coast populations, whereas no dominant polarity in the Gulf of California populations was observed. The test for isolation by distance (IBD) showed a significant correlation between genetic and geographical distances in Gulf of California populations, but not in Pacific coast populations, perhaps because of shifts in currents during El Niño Southern Oscillation (ENSO) events along the Pacific coast.     

Using Endemic Plant Species to Establish Critical Habitats in the Sierra de La Laguna Biosphere Reserve, Baja California Sur, Mexico

The Sierra de La Laguna, in the southern part of the state of Baja California Sur, Mexico, was decreed a biosphere reserve in 1994. It harbors relict plant communities with a high level of endemism. Floristic research has established that the two main communities, the oak–pine woodland (OPW) and the dry tropical forest (TDF), harbor 43 and 33 endemic species, respectively. We segregate the reserve surface into seven major habitats and each endemic species were assigned a hierarchic value into an abundance-distribution scale, useful as dominance ranking. Using such scale, we found that almost half of the species are in the lowest rank (low abundance and aggregate distribution). Using GIS, we obtain the surface for each habitat, where mountainsides represent the largest in the reserve area. We obtained an index of importance from the proportion of endemic species by habitat and its surface occupied, founding that, in spite of the small and fragmented nature of the upland riparian habitats, they have the greatest index value. Consequently, for future conservation plans in the reserve, these habitats should be considered remarkable sites, meriting better attention to ensure endemic plant preservation. Also, since 86% of the endemic species appear in one, two or three habitats, a high dependency on particular environmental conditions is suggested for them.     

Ecological effects of seaweed harvesting in the Gulf of California and Pacific Ocean off Baja California and California

The ecological effects of harvesting were investigated for two species, the giant kelp Macrocystis pyrifera and Eucheuma uncinatum, by using harvest records and aerial surveys that show yield changes and by using studies of recruitment, survivorship and community interactions. There were no ecological effects found for M. pyrifera harvested with contemporary methods, and there are no recommendations for changing current management practices for this species. It is recommended that E. uncinatum, which on occasion produces commercially significant standing crops, not be harvested unless special precautions are taken to leave some plants for regeneration of the harvested populations.