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.

     

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.     

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.     

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.     

Biogeography and endemism of ants (Hymenoptera: Formicidae) in Baja California, Mexico: afirst overview

Abstract Aims Ants (Hymenoptera: Formicidae) of the Baja California peninsula are poorly known, with information based largely on scattered museum and literature records. We provide the first comprehensive account of ant species occurring on the peninsula, we examine distribution patterns, and we assess the ‘peninsular effect’ which predicts that species richness declines from the base to the tip of a peninsula. Location Peninsula of Baja California, Mexico. Methods Data collection involved examining, identifying and recording label data from c. 2350 series of ants. These records provide a provisional, if incomplete, species list. We applied the incidence‐based estimator, Chao‐2, to our data base of specimen records to estimate the total number of ant species on the peninsula. We assessed endemism by comparing our peninsular species list to those from adjacent states. The peninsular effect was tested by comparing genus and species level richness between the two states of Baja California, and across five latitudinal blocks. Results We document 170 native ant species in thirty‐three genera, plus six non‐native species, in Baja California. It seems likely that additional species remain to be discovered: the Chao‐2 estimator of species richness, at 206.0 species, is about 20% higher than our observed species richness. About 30% of the species and 20% of the genera are restricted within Baja California to the relatively mesic California Floristic Province of north‐western Baja California. Nearly all of these species also occur in California. Forty‐seven species (27.6%) are peninsula endemics. Using our entire data set, the peninsular effect appears to be strong, with about twice as many species in the northern state of Baja California than are recorded from the southern state of Baja California Sur; the ratio of genera is 33 to 24. However, this effect becomes weak at the species level and absent at the genus level when minimizing habitat effects by omitting species restricted to the California Floristic Province. At a finer scale, across latitudinal blocks of about 1.9°, the number of species declines towards central portions of the peninsula and then increases in the Cape Region. Nine ant species display strongly disjunct distributions, and these occur in two general patterns: peninsula disjuncts and peninsula–mainland disjuncts. Main conclusions The Baja California peninsula supports a diverse and distinctive ant fauna, with the proportion of endemic species similar to that displayed by plants. Patterns of species and genus richness across the five latitudinal blocks provide poor support for the peninsular effect. Moreover, habitat diversity, especially that related to topographic relief, appears to be the most important factor affecting the gradient of ant species richness in Baja California. Additional collections are needed to develop a more complete species list and to determine the boundaries and status of many species. Nevertheless, the present data base provides a useful starting point for understanding the evolution of ant assemblages in Baja California and for comparison with peninsular patterns in other taxa.     

Land use changes affect distributional patterns of desert birds in the Baja California peninsula, Mexico

Reliable plans for desert bird conservation will depend on accurate prediction of habitat change effects on their distribution and abundance patterns. Predictive models can help highlight relationships between human‐related and other environmental variables and the presence of desert bird species. Presence/absence of 30 desert bird species of Baja California peninsula was modelled on the basis of explanatory variables taken from the field, maps, and digital imagery. Generalized linear models were fit to each bird species using both variables representing human activity and other environmental factors as predictors that might influence distribution. Probability of species presence was used as a habitat suitability index to evaluate the effect of human activity when the model contained a significant human activity variable. No differences were found in bird species richness between natural sites and those transformed by agriculture or urbanization. Of 59 bird species recorded in surveys, 34% were positively or negatively associated with human‐transformed habitats. Fourteen species seem to benefit from transformation of natural vegetation by agriculture or urbanization, while six were negatively affected. Sensitivity analyses of final models indicated all were robust. Results suggest that the occurrence of a large percentage of bird species inhabiting scrub habitats is sensitive to human habitat transformation. This finding has important conservation implications at regional scale as fragmentation and conversion of desert ecosystems into agricultural and urban areas affect the distribution of species that are highly selective for scrub habitat. Land use and anthropogenic activities seem to change ecological patterns at large spatial scales, but other factors could drive species richness distribution too (i.e. individual species response, species–energy relationships). The spatial modelling approach at regional scale used in this study can be useful for designing natural resource management plans in the Sonoran desert scrub.     

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.     

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.     

Element Concentrations in Some Species of Seaweeds from La Paz Bay and La Paz Lagoon, South-Western Baja California, Mexico

La Paz Bay and La Paz Lagoon are water bodies of the Gulf of California that are influenced by waste water discharges from the City of La Paz and from activities of the phosphorite mining company “Rofomex”. Because seaweeds concentrate elements from the water and are used as effective indicators of contamination by metals, we investigated their usefulness in this region. Concentrations of certain major elements (Ca, Fe, K and Na) and trace elements (As, Ba, Co, Cr, Cs, Hf, Rb, Sb, Sc, Se, Sr, Ta, Th, U, Zn and Zr) were determined in 12 species of seaweeds from La Paz Bay and La Paz Lagoon using instrumental neutron activation analysis. The contents of trace elements of environmental importance (As, Co, Cr, Fe, Sb, Se and Zn) in all studied samples are within the range of typical levels for a pristine environment not subjected to anthropogenic impact. Somewhat higher concentrations of Cr (81mg kg⁻¹), Hf (4mg kg⁻¹), Rb (48mg kg⁻¹), Sc (6.3mg kg⁻¹), Ta (0.95mg kg⁻¹), Th (6.8mg kg⁻¹), U (33mg kg⁻¹) and Zn (90mg kg⁻¹) were found in the green seaweed species Ulva (formerly Enteromorpha) intestinalis, whereas such elements as As (77mg kg⁻¹), Sb (1.4mg kg⁻¹) and Se (1.8mg kg⁻¹) were mainly concentrated in the species Sargassum sinicola, Codium cuneatum and Padina mexicana respectively. Because of their higher abundance and heterogeneity in elemental composition the seaweeds species Ulva intestinalis and Caulerpa sertularioides seem to be more suitable for further biomonitoring of heavy metal pollution of the coastal waters in this zone.     

Endemic regions of the vascular flora of the peninsula of Baja California,Mexico

Question: Can we recognize areas of high endemism and high endemic richness, using data from collections, and what are the ecological variables that best explain these areas? Location: Peninsula of Baja California, Mexico. Methods: We analysed the distribution of 723 endemic vascular plants species along the peninsula of Baja California and neighbouring islands distributed in 218 cartographic cells 15’ x 20’ in size. By means of a residual analysis, we identified areas of significantly high endemic species richness, and we calculated the degree of endemicity (or rarity) in each cell by giving to each species a weight factor inversely proportional to the land area it covers. Results: Nine regions of high‐endemicity and/or high endemic species richness were found. Discussion and conclusions: The analyses of rarity and endemic species richness showed two contrasting scenarios: High endemicity values in oceanic and sky islands accounts for a high number of species with a restricted distribution, promoted most likely by genetic isolation and high environmental heterogeneity. High endemic richness along the peninsular coast is related to ecotonal transition along vegetation types. After correcting for collection effort (i.e. the number of specimens collected within a cell), we found the phytogeographic region and altitudinal heterogeneity to be the variables that best predicted endemic richness. Both high endemism and high endemic richness have distinct geographic patterns within our study region. The nine endemic regions provide elements for priority definitions in future conservation programs.     

Contributions toward understanding the biodiversity of Passiflora in North America: Updates and a new combination from the Baja California Peninsula,Mexico and vicinity

The Baja California Peninsula and surrounding landmasses harbor an abundant flora in an otherwise harsh and arid environment. Of the many plant groups native to this peninsular and insular region, passionflowers (Passiflora, Passifloraceae) are represented by several conspicuous taxa that all belong to a single lineage, section Dysosmia. Basic questions remain regarding this group, particularly the taxonomic status among the Passiflora arida complex. Therefore, we investigated the claims of endemism, habitat characteristics, and taxon boundaries with in section Dysosmia in the Baja California region using extensive sampling of herbarium specimens and iNaturalist observations. We confirmed that only one of the native Passiflora taxa (P. fruticosa) was endemic to the Baja California Peninsula, with an additional taxon (P. palmeri) considered near‐endemic. Environmental data revealed significant distinctions between the habitats of many of the native taxa as well as within the P. arida complex, especially with respect to precipitation and temperature tolerances. Geometric morphometric analyses of leaf shape were largely not successful at separating taxa, indicating leaf shape may not be a good indicator of taxon identity in this particular group. Based on ecological differences and discrete macro‐ and micromorphological features, a varietal name is here synonymized and a new combination is proposed: Passiflora pentaschista.     

Water relations of stem succulent trees in north-central Baja California

Summary Water relations of several stem succulent trees were measured in north-central Baja California in comparisons to other growth forms in the same habitat. Our research concentrated on three stem succulent species (Idria collumnaris, Pachycormus discolor and Bursera microphylla) each with a different succulent stem morphology. The stem succulent trees had 1 to 4 kg H₂O/m³ of trunk while the other trees and shrubs in the same habitat had 0.6 to 0.8 kg H₂O/m³. The diurnal and seasonal variation in leaf water potential was small for the stem succulent species in comparison to deciduous and evergreen species as a consequence of the stem-water, buffering capacity. In addition, the leaf conductance of the stem succulent species was low (60 mmol m^–2 s^–1) and yet, the leaf conductance decreased through the day similar to adjacent evergreen and deciduous species. The leaves of the stem succulent trees lost turgor at low saturated water deficits (0.06 to 0.14), had comparatively high osmotic potentials, and high values of elastic modulus in comparison to adjacent evergreen and deciduous species. The stem acts as an important buffering mechanism allowing for the maintenance of leaf turgor in these stem succulent trees. The low transpiration rates of the stem succulent trees may be a mechanism to minimize leaf saturated water deficit and extend leaf longevity.     

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.     

Palynological record (1483–1994) of Gymnodinium catenatum in Pescadero Basin, southern Gulf of California, Mexico

This paper presents the stratigraphic record of Gymnodinium catenatum during the last ~ 500 years, in Pescadero Basin, southern Gulf of California. Our aim is to help clarify the relation between abundances of cysts of G. catenatum and regional changes in the sea surface temperature and nutrient availability at a decadal scale. The record was obtained from core samples of laminated sediments dated with ¹⁴C, representing conditions in the area from 1483 to 1967 (PCM99-74C-5) and from 1907 to 1994 (PCM00-61C-4). Samples were treated with normal palynological processing, without oxidation, and using Lycopodium spores for quantification. The palynological assemblages observed contain varied and abundant terrestrial and marine components. However, we focus on the abundance of G. catenatum, due to its toxicity and the resulting impact in the area. This species is currently common in the area, and according to our results has been present there since ~ 1483. Cysts of G. catenatum are generally abundant in the 20th century, with maximum concentrations observed from 1888 to 1920, and from 1945 to 1965, but they show a steady decrease in the latter part of the century (1965–1994). Before 1830, abundances of G. catenatum were low because of increased upwelling conditions, probably related to a higher variability of the winter sea surface temperatures in the area. Both our data in the 20th century and the actual reports in the area, indicate a close relation with sea surface temperature. From 1907 to 1994 cyst abundances seem to increase during cool La Niña conditions in the area, and decrease during warmer El Niño events. They also show an evident decrease in cyst abundance from 1970 to 1994, while the sea surface temperature in the area increased during the same period. This inverse relation is also indicated by the low abundances of G. catenatum observed during red tide events, combined with high sea surface temperatures in Mazatlan. Additionally, our results do not show any relation of G. catenatum blooms and anthropogenic activity in the area.     

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.     

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.     

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.     

Dry vegetation in relation to the physical environment in the Baja California Peninsula,Mexico

Abstract. An ordination analysis of vegetation and flora of Los Cabos Region, Baja California Peninsula, Mexico and its relationships with their environment and geomorphic characteristics was studied at 38 sites, selected based on ecoregion mapping units (EMU) previously delineated for the study area. Multivariate methods were used to analyse the relationship between physical characteristics of the environment and the two primary vegetation types, the Dry tropical forest (DTF) and the Xerophilous scrubland (XS), which together represent 83% of the vegetation cover in the study area. Sites were grouped based on both physical characteristics and relative abundance of plant species. The results of the statistical analysis suggest that altitude, rainfall, temperature, and lithology can help explaining differences between these important vegetation types. In the case of XS, the morpho‐physiognomic characteristics of vegetation in each site discriminated between two scrub types.     

Morphology of Pyrodinium bahamense Plate (Dinoflagellata) near Isla San José, Gulf of California, Mexico

The morphology of Pyrodinium bahamense south of Isla San José in the Gulf of California, Mexico was described using light and scanning electron microscopy. Morphological and dimensional examination of whole cells and thecal patterns were conducted to discriminate between P. bahamense var. compressum and P. bahamense var. bahamense. Microscopic examinations confirmed that specimens of P. bahamense from Isla San José are closely related to P. bahamense var. bahamense. The main average dimensions were: cells 41.9 μm long, 43.8 μm wide, 55.6 μm amplitude, apical horn 7.2 μm long, and the left antapical spine 19.5 μm long. The highest cell concentration was 240 cells l⁻¹ and occurred with a bloom of Pseudo-nitzschia spp. The presence of this dinoflagellate off the east coast of the Baja California Peninsula had not been previously reported. Recently, P. bahamense from Florida tested positive for saxitoxins. Paralytic shellfish poisoning from this species has occurred in Mexican waters. Here, significant aspects of taxonomy, toxicology, life cycle, and ecology are discussed.