Cabo Corrientes Research Articles

A New Species of Hedyotis (Rubiaceae) from Jalisco, Mexico

Hedyotis macvaughii, a new species from Jalisco, Mexico, is described and compared with related taxa. It is a small wiry-stemmed perennial herb with filiform leaves, small funnelform flowers, and non-crateriform seeds. Among specimens lent by MICH was a previously unnamed species collected by Rogers McVaugh in Jalisco, Mexico. It is here described as a new species of Hedyotis. Hedyotis macvaughii Terrell, sp. nov. TYPE: Mexico. Jalisco: steep mountain sides 3-10 km generally E on the road to Mina del Cuale from the junction 5 km NW of El Tuito, Mpio. de Cabo Corrientes, elev. 850-1150 m, 16-19 Feb. 1975, R. McVaugh 26426 (holotype, MICH). Figures 1, 2. Herba perennis rhizomata. Caules 15-20 cm alti erecti. Folia filiformia. Inflorescentia diffusissima. Corolla alba infundibuliformis 3.0--4.5 mm longa. Capsulae subglobosae 1-2 mm longae. Semina 0.3-0.5 mm longa compressa ellipsoidea hilo punctiformi in crista ventrali. Perennial herbs with slender rhizomes. Stems 15-20 cm tall, subterete, erect, very slender, wiry, glabrous, widely and diffusely branched, internodes numbering ca. 5-6. Leaves 6-20 mm long, 0.3-0.7 mm wide, filiform, with 2 inconspicuous grooves beneath, obtuse, glabrous above and beneath. Stipules to 1 mm long and wide, inconspicuous, entire or few-toothed. Inflorescences widely spreading, diffuse, to ca. 15 cm wide, with many filiform branches, flowers heterostylous, in many 2-5-flowered cymes, pedicels filiform, to ca. 15 mm long. Calyces glabrous; lobes 4, 0.4-0.8 mm long, 0.20.5 mm wide, broadly lanceolate, obtuse. Corollas 4-lobed, 3.0-4.5 mm long, funnelform, white; tubes 2.0-2.7 mm long, 0.5-0.6 mm wide at base; lobes 1-2 mm long, 0.5-1.5 mm wide, ovate. Anthers 4, ca. 0.5-0.8 mm long. Pollen colporate type A. Stigmas 2-branched, ca. 0.5 mm long, linear. Pin flowers with stigmas slightly exserted at corolla throat, anthers located at /3-1J2 point of corolla tube. Thrum flowers with anthers slightly exserted at corolla throat, stigma not seen. Capsules 1-2 mm long and wide, subglobose, thin-walled, straw-colored, ?-7/s inferior, apices rounded or truncate, dehiscence loculicidal. Seeds several per capsule, 0.3-0.5 mm long, 0.2-0.35 mm wide, brown, dorsiventrally moderately compressed, in outline broadly elliptic, blong, or ovoid, sometimes irregularly angulate, non-crateriform, dorsal side almost smooth or obscurely reticulate, convex, ventral side finely reticulate, hilum punctiform on acentric hilar ridge, ridge obtuse or acutish, low to rather high, testa with areoles single or double walled. Chromosome number unknown. Hedyotis macvaughii (spelling in accordance with Greuter et al., 1994: Rec. 60 C.4.(a)) is somewhat geographically isolated from related species that occur to the eastward in Mexico, as there are no records of Hedyotis or Houstonia species occurring in Jalisco, Colima, Michoacin, or Nayarit (Standley, 1918; Terrell, 1991). The new species is distinct in its morphology. It is a small wiry-stemmed perennial herb with filiform leaves and small funnelform flowers (Fig. 1). The seeds (Fig. 2) lack any kind of ventral depression or cavity, hence are non-crateriform. They are moderately dorsiventrally compressed and have a punctiform hilum on a low to rather high hilar ridge. These seed characters ally the new species with Hedyotis rather than Houstonia, which has crateriform seeds, or Oldenlandia, which has distinctive 3-angled (trigonal) or conic seeds (Terrell, 1991). Lewis (Terrell et al., 1986) recognized three types of pollen aperture structure, based on the extent of thinning of the nexine in the equatorial region. Two of these types, colpororate and colporate type B, occur in Houstonia, whereas Hedyotis and Oldenlandia have predominantly colporate type A. For Hedyotis macvaughii, Lewis (pers. comm., May 1995) reported the occurrence of colporate type A pollen. There are three species that superficially resemble or might be confused with Hedyotis macvaughii: Hedyotis asperuloides Bentham, Houstonia palmeri A. Gray, and Houstonia longifolia Gaertner. Hedyotis asperuloides of Baja California, Mexico, is a small annual with corollas 3-11 mm long, anthers 1.0-1.3 mm long, stigma branches 1.0-1.4 mm long, capsules 1.3-5.0 mm long that are turbinate, NovoN 6: 128-130. 1996. This content downloaded from 157.55.39.215 on Wed, 31 Aug 2016 04:44:24 UTC All use subject to http://about.jstor.org/terms Volume 6, Number 1 1996 Terrell Hedyotis macvaughii from Mexico 129

Satellite-derived estimates of phytoplankton biomass off Southern Baja California

All available estimates of photosynthetic pigment concentration derived from data generated during I978-1986 by the sensor Coastal Zone Color Scanner (CZCS) were used to interpret the spatial and temporal variations of phytoplankton biomass in a transept from Punta San Hipólito (27ºN, 114º30’W) to Cabo Corrientes (20º30’N. 105º30’W) off southern Baja California, Mexico. Highest pigment concentrations were present in areas near the coast. We suggest that they were due to upwelling and to interaction between the marine currents and local physiography. A recurrent front was observed off Cabo San Lucas. with the strongest pigment concentration gradients at the end of spring and beginning of summer, during non-El Niño years. There was a clear seasonal variation near the coast. immediately west of Baja California. high pigment values (3 to 8 mg m–3) were observed from February through August. Off Cabo Corrientes, high values occurred from January through May (5 to 8 mg m–3). These areas experience strong seasonal upwelling. El Niño had a clear effect on pigment concentration, hut it was not the only cause of interannual variation. There were relatively low pigment concentrations throughout the whole transept starting in September 1982, with values often lower than 20% of those during the previous period. These low concentrations were maintained through August 1984 at the entrance to the gulf, and through December 1985 off the west coast of Baja California.

Shelf-sea response to tropical storms along the west coast of Mexico

The shelf-sea response to tropical storms along the west coast of Mexico is investigated using a layered ocean model forced by a travelling circular storm. Simulations using a straight coastline with a narrow continental shelf show that the response is typified by a cyclonic eddy along the storm track with inertial oscillations in the deep ocean and a trapped wave pulse at the coast. The coastal wave has typical phase speeds of 1.5–2.0 m s −1, alongshore scales of 500–1000 km, and cross-shore scales of 100–200 km. Test runs indicate that the coastal response is a function primarily of the intensity and duration of alongshore winds near the coast, and of the propagation speed of the storm relative to the free coastal-trapped wave phase speed. Atmospheric pressure anomalies appear to play a minor role in generating the coastal wave. Model runs using realistic bathymetry and storm parameters for two hurricanes during the summer of 1984 are compared with current, temperature and pressure observations in the Gulf of California. The model results are in good agreement with observed wave properties with typical surface displacements of 20 cm, alongshore current speeds of 0.5 m s −1, and upper interface displacements of 30 m. Wave generation for the two 1984 storms occurs primarily in the vicinity of Cabo Corrientes where storm winds are reported to be the strongest. The cape geometry in this region may also contribute to the enhanced response.

A New Species of Marathrum (Podostemaceae) from Jalisco, Mexico

A new species of Podostemaceae, Marathrum rubrum, from Jalisco, Mexico, is described and illustrated. Capillaceous leaf divisions and red leaf color distinguish M. rubrum from other species. RESUMEN. Se describe e ilustra una especie nueva de la familia Podostemaceae (Marathrum rubrum) del estado de Jalisco, Mexico. Las divisiones capiliformes y el color rojizo de las hojas distinguen a M. rubrum de las otras especies. The pantropical Podostemaceae are the largest family of aquatic flowering plants. Little taxonomic work has been conducted on New World Podostemaceae since Royen's treatments (1951, 1953, 1954). Currently most species of Podostemaceae in the New World are poorly collected, taxonomic boundaries at both the specific and generic levels are unclear, and factors relating to the unusually high incidence of endemism (e.g., > 45% among New World species) are unresolved. Marathrum, one of the largest genera of Podostemaceae, is composed of 25 species occurring in tropical river rapids and waterfalls. The genus ranges from the West Indies and Mexico through Central America, to northwestern portions of South America (Royen, 1951). During field studies aimed at clarifying the taxonomy of Podostemaceae in Mexico, collections were made from Jalisco that did not correspond to any described species. These collections serve as the basis for the description of a new species, Marathrum rubrum Novelo & Philbrick. Marathrum rubrum Novelo & Philbrick, sp. nov. TYPE: Mexico. Estado de Jalisco: municipio de Cabo Corrientes, Puente Los Horcones sobre el rio, a 27 km al S de Puerto Vallarta rumbo a Chamela, 6 Mar. 1991, Novelo & Philbrick 1003 (holotype, MEXU; isotype, RSA). Figure 1. Herbae caule longo, prostrato, applanato; lamina iterum atque iterum pinnata, divisionibus ultimis capilliformibus, 2-4.5 mm longis, 0.02-0.06 mm latis, rubescentibus, apice acutis. Flores solitarii, axillares, pedicellati; pedicelli apice expanso, cupulato, cupula 1.5-2 mm diametro. Tepala triangularia, filamentis alternantia. Stamina 7-9 in verticillo, libera, pistillum cingentia. Antherae 1.52.8 mm longae. Styli liberi, conici. Fructus 4.5-5(-6) mm longus, 2 valvis, quaque 3-costata. Aquatic herbs usually with a long prostrate and flattened stem up to 1 cm diam., strongly adhering to rocks. Leaves alternate, up to 20 cm long, petiole 2.5-9 cm long, cylindrical, up to 0.8 mm diam., with a broadened base; blade repeatedly pinnate, the later divisions capillaceous, 2-4.5 mm long, 0.02-0.06 mm wide, apex acute. Flowers hermaphroditic, actinomorphic, pedicellate, borne singly, axillary, protected by a spathella; spathella 0.72 cm long, thin, clavate. Pedicels 3-5.5 cm long, elongating during anthesis, with an expanded apex forming a cuplike process around the capsule base, cup 1.5-2 mm diam., with irregular border. Tepals 0.5-0.9 mm long, triangular, alternating with the stamens. Stamens 7-9, free, in a ring surrounding the pistil; filaments 2.3-4(-9) mm long, subulate, flattened, elongating during anthesis, deciduous; anthers 1.5-2.8 mm long, sagittate, basifixed, 2-celled, dehiscing longitudinally by 2 lateral slits. Ovary superior, ellipsoid, 2-locular; styles 2, 0.6-1.5 mm long, free, conical, ovules numerous, placenta axile. Fruit 4.5-5(-6) mm long and 1.7-2.2 mm diam., 2-locular capsule, suture margins thickened; valves 2, subequal, each 3-ribbed, one of them deciduous. Seeds 0.25-0.30 mm long, 0.12-0.18 mm wide, 574 (SD 317, N = 20) per capsule, obovoid. Pollen 14.5 um (SD 0.8, N = 30) diam., tricolpate, tectum spinulose. Paratypes. MEXICO. Jalisco: Municipio de Cabo Corrientes, Rio Horcones, aprox. 17 km S de Puerto Vallarta rumbo a Chamela, 6 Feb. 1991, Novelo 979 (MEXU, RSA); Puente Los Horcones sobre el rio, a 27 km al S de Puerto Vallarta rumbo a Chamela, 6 Feb. NOVON 3: 456-458. 1993. This content downloaded from 207.46.13.111 on Tue, 09 Aug 2016 05:30:22 UTC All use subject to http://about.jstor.org/terms Volume 3, Number 4 1993 Novelo & Philbrick

Late Cenozoic subduction and continental margin truncation along the northern Middle America Trench

The narrow inner trench slope and the truncated igneous and metamorphic terrane along the west coast of Mexico between Cabo Corrientes and the Gulf of Tehuantepec indicate that part of the continental margin has in some way been removed during the process of subduction. However, a detailed marine geophysical survey of the inner trench slope near Acapulco indicates that this removal is not occurring now. South-southwest–trending magnetic anomalies produced by the Xolapa metamorphic complex extend seaward only 20 to 30 km. Oceanic magnetic anomalies that trend N50°W extend as much as 30 km landward of the trench. The boundary between these two magnetic patterns lies landward of the trench-slope break and beneath the upper-slope sediment pile. The nonmagnetic material forming the acoustic basement trenchward of the metamorphic rocks is interpreted to consist of late Miocene to Holocene deformed trench-floor turbidites. Deformation associated with subduction has reversed the gradients of several submarine canyons and tilted the seaward edge of the upper-slope sediment pile away from the trench. The morphology and structure of the inner trench slope is typical of accreting trench-arc systems, although the morphotectonic units in this system are smaller than usual. Accretion since late Miocene time is suggested by the age of dredged slope sediments and by analysis of offshore magnetic anomalies, which indicate a change from right-lateral oblique to perpendicular subduction at that time. Removal of the continental margin probably occurred intermittently between Late Cretaceous and late Miocene time. Possible mechanisms include subduction of continental crust (tectonic erosion), left-lateral translation associated with the Caribbean–North American plate boundary, and right-lateral translation associated with oblique subduction between the Farallon or Cocos plates and the North American plate. Geological data favor right-lateral offset and suggest that some of the missing margin may be the slivers of subduction complex found along the west coast of Baja California and possibly even farther north.

Thermohaline Structure and Baroclinic Flow Across the Gulf of California Entrance and in the Revilla Gigedo Islands Region

The thermohaline structure, vertical stability and baroclinic flow between the Gulf of California entrance and the Revilla Gigedo islands are investigated by means of closely spaced salinity and temperature depth profiles (STD's). The outstanding feature of the upper ocean is the 10–30 m thick layer of high stability centered at about 50 m. This layer separates the tropical surface water from the thin shallow salinity minimum below, which is most pronounced between 80 and 130 m. The outstanding feature of the deep water is the marked increase in abyssal temperatures east of Isla Socorro, apparently due to heat flow. Baroclinic flow in the Revilla Gigedo islands region is characterized by high-speed flow near capes and islands. Outflow from the Gulf of California takes place in a narrow high velocity core near its western side. The width of the high-speed core is of the order of 30 km and speeds >30 cm sec−1 occur down to 700 m. The high-speed flow is accomplished by a break in the high stability layer. Inflow into the gulf occurs over a broader area, mainly in the central part. North of Isla Socorro, a strong west-northwestward setting current is observed. It is about 150 km wide, 700 m deep and has maximum speeds of 33 cm sec−1 just above the high stability layer. Near the island, a narrow countercurrent with speeds up to 17 cm sec−1 is found. Off Cabo Corrientes, a strong northwestward setting current is encountered. The current is about 100 km wide, extends to a depth of 700 m, and has a maximum speed of 46 cm sec−1 near the surface.