South American Forms Research Articles

A new basal sauropod dinosaur from the middle Jurassic of Niger and the early evolution of sauropoda.

BackgroundThe early evolution of sauropod dinosaurs is poorly understood because of a highly incomplete fossil record. New discoveries of Early and Middle Jurassic sauropods have a great potential to lead to a better understanding of early sauropod evolution and to reevaluate the patterns of sauropod diversification.Principal FindingsA new sauropod from the Middle Jurassic of Niger, Spinophorosaurus nigerensis n. gen. et sp., is the most complete basal sauropod currently known. The taxon shares many anatomical characters with Middle Jurassic East Asian sauropods, while it is strongly dissimilar to Lower and Middle Jurassic South American and Indian forms. A possible explanation for this pattern is a separation of Laurasian and South Gondwanan Middle Jurassic sauropod faunas by geographic barriers. Integration of phylogenetic analyses and paleogeographic data reveals congruence between early sauropod evolution and hypotheses about Jurassic paleoclimate and phytogeography.Conclusions Spinophorosaurus demonstrates that many putatively derived characters of Middle Jurassic East Asian sauropods are plesiomorphic for eusauropods, while South Gondwanan eusauropods may represent a specialized line. The anatomy of Spinophorosaurus indicates that key innovations in Jurassic sauropod evolution might have taken place in North Africa, an area close to the equator with summer-wet climate at that time. Jurassic climatic zones and phytogeography possibly controlled early sauropod diversification.

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DDT is back: let us spray!

Relationships among subspecies of New World octoploid strawberry species, Fragaria virginiana and Fragaria chiloensis, based on simple sequence repeat marker analysis

Simple sequence repeat (SSR) markers, developed from Fragaria ×ananassa Duchesne ex Rozier ‘Earliglow’, were used to assess diversity among all of the proposed taxa of Fragaria virginiana Mill. and Fragaria chiloensis (L.) Mill. to facilitate strawberry germplasm utilization and conservation and to help resolve taxonomic relationships. DNA was obtained from 111 individuals representing F. chiloensis subsp. pacifica Staudt, F. chiloensis subsp. lucida (E. Vilm. ex Gray) Staudt, F. virginiana subsp. virginiana Mill., F. virginiana subsp. glauca (S. Watson) Staudt, F. virginiana subsp. grayana (Vilm. ex J. Gay) Staudt, and F. virginiana subsp. platypetala (Rydb.) Staudt from North America, F. chiloensis subsp. chiloensis f. chiloensis and F. chiloensis subsp. chiloensis f. patagonica from South America, F. chiloensis subsp. s andwicensis (Decne.) Staudt from Hawaii, as well as F. ×ananassa subsp. cuneifolia (Nutt ex Howell), and F. ×ananassa subsp. ananassa . A total of 108 bands were scored among all accessions using the five SSR primer pairs, for a mean of 21.6 bands per primer pair with 3–8 bands in individual accessions. Cluster analysis and principal coordinate analysis using Jaccard similarity coefficients based on presence or absence of bands supported the separation of F. virginiana and F. chiloensis as distinct species. The various F. virginiana subspecies were not distinguishable. The two South American forms of F. chiloensis subsp. chiloensis are very similar to each other and distinct from the North American subspecies. The F. chiloensis subsp. sandwicensis accessions were distinct from other taxonomic classes. The F. ×ananassa cultivars clustered most closely with the South American F. chiloensis supporting the origin of F. ×ananassa primarily from South American rather than North American F. chiloensis. While the North and South American F. chiloensis subspecies should remain separated based on their molecular distinction, consideration should be given to classifying F. chiloensis subsp. pacifica and subsp. lucida as different forma of a single North American F. chiloensis subspecies, rather than as separate subspecies. This is similar to the current classification of the two South American forma of F. chiloensis subsp. chiloensis (L.) Mill. Similarly, the F. virginiana subspecies should be reclassified as forms of a single subspecies, F. virginiana subsp. virginiana, rather than separate subspecies.

Testing phylogenetic implications of eggshell characters in side-necked turtles (Testudines: Pleurodira)

Amniote egg and eggshell morphology is a rich source of characters to link aspects of reproductive biology with systematics. Extensive work concerning both anatomy and phylogenetic assignability has been done on fossil bird and dinosaur eggs, but little is known for extant sauropsids. The utility of eggshell characters for phylogenetic analyses is tested and discussed for extant side-necked turtles (Pleurodira), and the diversity of egg ultrastructure is examined in several species. Egg gross morphology and eggshell ultrastructure of 12 species of extant side-necked turtles was documented using scanning electron microscopy. Thirteen eggshell characters were scored and mapped on a composite phylogeny and ancestral character states were reconstructed. Many of the characters do not show a phylogenetic signal according to a test comparing the number of steps on the chosen phylogeny with that on randomly generated trees. The presence of conservative, clade-supporting features could be demonstrated, and the following clades are supported by several characters: the Elseya– Emydura entity, short-necked Australasian chelids, is backed by two characters, and two additional characters could potentially support this group. Three characters support the monophyly of South American chelids, whereas two characters argue for the exclusion of Hydromedusa, a long-necked form resembling Australian chelids rather than South American forms, from this clade.

Molecular cloning and differential IgG responses to a histidine-rich antigen (OvL3.C1) of Onchocerca volvulus by selected residents of onchocerciasis endemic regions in Cameroon and Ecuador

In order to further investigate host-parasite interactions in onchocerciasis, a major Onchocerca volvulus histidine rich antigen termed OvL3.C1 was isolated from an O. volvulus cDNA library using antibodies from putatively immune subjects living in onchocerciasis endemic communities in Cameroon. Analysis of its sequences predicted the protein to be helix-rich with a single transmembrane region. Recombinant OvL3.C1 antigen induced from pBAD-TOPO/Thio vector in Escherichia coli was purified as inclusion bodies and further by a combination of Ni 2+ chelate chromatography and electroelution. Anti-OvL3.C1 immunoglobulin G (IgG) subclass levels were assessed by ELISA in 15 pairs and 18 pairs of selected and cross-matched infected and putatively immune subjects from Cameroon and Ecuador, respectively. IgG3 and IgG4 levels were shown to be significantly higher in putatively immune (immune protected) subjects. A higher IgG3 level in endemic normal subjects is implicated in parasite killing and the development of the putative immune status while IgG4 has been shown to block onchocercal pathology. OvL3.C1 is a dominant antigen in onchocerciasis which elicits strong responses in subjects expose to both African and South American forms of onchocerciasis. It is therefore an important player in mechanisms of resistance or allergy attenuation in onchocerciasis. Keywords: Onchocerciasis, immunoglobulin G, putative immunity

Ferns from the Cretaceous of Alexander Island, Antarctica: Implications for Cretaceous phytogeography of the Southern Hemisphere

Six new records of ferns from the late Albian flora of Alexander Island, Antarctic Peninsula, provide further evidence for a widespread Cretaceous Austral flora. Phyllopteroides antarctica sp. nov. is the first record of this genus from Antarctica, extending its range from Australia, New Zealand, and India. It appears that Phyllopteroides forms an important component of eastern Gondwana mid-Cretaceous floras. Further floristic affinities with Australia are supported by the presence of Sphenopteris warragulensis, Microphyllopteris and Coniopteris sp. cf. C. frutiformis. Few southern South American forms can be recognized and these include Sphenopteris sanjuliensis. The Alexander Island flora comprises a mixture of endemic, eastern Gondwanan, and rare South American elements that reflect its position close to a major floristic boundary.

Morphological stasis in an old and widespread group of species: Contribution to the taxonomy and biogeography of the genus Girardia (Platyhelminthes, Tricladida, Paludicola)

Material is described that contributes to our understanding of the anatomy of 11 species of the genus GirardiaBall, 1974 and the taxonomy of one species of RomankenkiusBall, 1974. Apart from recently collected specimens, the study for the first time details old syntype material that was recovered for the species G. anceps and G. andina, resulting in the first modern description of the last-mentioned species. Relatively recently collected specimens from new sampling sites are described for G. chilla, G. dorotocephala, G. festae, G. paramensis, and G. tigrina. The new records for G. festae considerably enlarge the known geographic range of this species in South America, particularly east of the Andes. It is shown that contrary to the opinion of earlier workers there is some slight, but invariable, anatomical difference between North and South American specimens of G. tigrina, with the Neotropical animals having a much more muscled bursal canal. This slight anatomical difference suggests that the North and South American forms are actually sibling species. Four new Girardia species are described, three for the South American continent (G. avertiginis, G. capacivasa, G. jugosa) and one from Jamaica (G. bursalacertosa). The study confirms earlier conclusions that generally species of Girardia are anatomically very similar and that therefore species recognition can be difficult. It is striking that taxonomic diversity in the Neotropical Region is low, in that the majority of the freshwater planarians belongs to a single genus, viz. Girardia. It is concluded that Romankenkius michaelseni (Böhmig, 1902) is a junior synonym of R. patagonicus (Borelli, 1901).

Conchostracans and insects from the Upper Triassic of the Biobío river ('Santa Juana Formation'), south-central Chile

En este trabajo se da a conocer el hallazgo de artropodos del Triasico Superior, en estratos que afloran a lo largo del rio Biobio, en el centro sur de Chile. Se describen, por primera vez, para el Triasico de Chile, representantes del orden Coleoptera: Ischichucasyne santajuanaensis gen. et sp. nov. y Ademosyne sp. (Permosynidae). Sobre la base de nuevos materiales recolectados y fotografias de detalle con microscopia electronica de barrido, se reestudiaron los conchostracos Menucoestheria terneraensis Gallego y Polygrapta troncosoi (Gallego) comb. nov. Se destaca la estrecha relacion entre M. terneraensis Gallego y otras especies de Argentina y Antartica. Se menciona la posibilidad de que este genero haya evolucionado a partir de especies de Euestheria Deperet y Mazeran, y que a su vez Menucoestheria Gallego haya dado origen a todos los eosestherideos gondwanicos. Se propone, tentativamente, el empleo de Menucoestheria y Polygrapta como fosiles guias para los niveles continentales del Triasico Superior de Argentina y Chile. La entomofauna registrada muestra estrechas afinidades con las faunas argentinas, con las que comparte los generos Ademosyne e Ischichucasyne, y amplia el conocimiento sobre la diversidad de artropodos durante el Triasico en Sudamerica. La presencia del homoptero dysmorphoptilideo Bandelnielsenia Martins-Neto y Gallego, la mas plesiomorfica de las formas sudamericanas, resulta fundamental para comprender la filogenia de este importante grupo triasico.

Intraspecific Karyotypical Diversity in Brackish Water Fishes of the Eleotridae Family (Pisces, Perciformes)

The Eleotridae family consists of 35 genera and 150 species distributed in freshwaters/brackish waters, estuaries or shores of tropical and subtropical regions. A few species are found in the Central America and South America. Cytogenetic analyses were performed on sympatric species Dormitator maculatus (12 individuals; 9 males and 3 females) and Eleotris pisonis (5 individuals; 2 males and 3 females) collected in the lower course of the Pium River, Northeastern Brazil. Both the species have 2n=46 with striking differences for the chromosome formulas (D. maculatus, 40m-sm+6st-a and E. pisonis, 46a). The two species revealed preferentially centromeric or telomeric heterochromatic regions and absence of structural chromosome heteromorphisms between the sexes. The NORs are located on the short arm of a submetacentric pair (pair 4) in D. maculatus and in intersticial position on a medium acrocentric (pair 21) in the E. pisonis. Meiotic analyses carried out on D. maculatus and E. pisonis showed a modal value of 23 in both MI and in MII. Comparison with cytogenetic data of Mexican populations (D. maculatus, 34m-sm+12st-a; E. pisonis, 2m-sm+42st-a) indicated that the karyotypical changes among the populations from Northeastern Brazil and the Mexican coast are mainly due to pericentric inversion, although translocations, fission and fusion are involved in the karyotypic diversification of the group. The differences observed among the karyotype macrostructure of South and Central American forms suggest the existence of distinct species in these two regions.

A new frog (Amphibia: Anura) from the Lower Cretaceous of western Liaoning, China

Based on a nearly complete skeleton, an archaic frog is described from the Early Cretaceous Yixian Formation near Yixian, western Liaoning Province, China. The new frog shows several peculiar morphologies including the presence of a co-ossified parahyoid bone with a V-shaped configuration. Such a parahyoid was previously known only for the problematic taxon Neusibatrachus from the Lower Cretaceous of Spain. A phylogenetic analysis was performed with the inclusion of the new taxon and Neusibatrachus. This analysis suggests that the new taxon is a primitive archaeobatrachian closely related to Notobatrachus and Vieraella, while Neusibatrachus is placed as a basal member of the Pipoidea. The suggested relationships of the new frog with South American forms reveal a biogeographic enigma that cannot be resolved until there is more fossil evidence and current phylogenetic hypotheses are further evaluated.

A new species of Eucyclops Claus (Copepoda: Cyclopoida) from Southeast Mexico with a key for the identification of the species recorded in Mexico

Eucyclops torresphilipi sp. nov. is described from samples collected in the state of Chiapas, on the southeastern Pacific coast of Mexico. It belongs to a group of species similar to the presumably cosmopolitan E. agilis (Koch, 1838). The new species is closest to the South American E. delachauxi (Kiefer, 1925); it can be distinguished from its congeners by a combination of characters that include a fifth leg with a particularly slender inner spiniform seta that is as long as the outer seta, the caudal rami has spinules covering up to of the outer margin, caudal rami over 4 times longer than wide, the relative length of the dorsal seta, and the proportion of the terminal spines of the third exopodal segment of the fourth legs. Only nine other nominal species of Eucyclops have been recorded in Mexico; nearly half of them are known also from South America. The new species seems to have a restricted distributional range; however, it could be present also in Guatemala. Its morphological affinity with South American forms confirms the influence of the South American cyclopoid fauna in Mexico. A key for the identification of the species of Eucyclops recorded in Mexico is included.

Historical biogeography and distribution of the freshwater cyclopine copepods (Copepoda, Cyclopoida, Cyclopinae) of the Yucatan Peninsula, Mexico

AbstractAim To determine and analyse the distribution of the freshwater cyclopine copepod fauna of the Yucatan Peninsula (YP) and its relationship with the geological and climatic history of this Neotropical karstic zone.Location The Yucatan Peninsula, Mexico.Methods Plotting of georeferenced sites, analysis of local and regional geological and climatic history, analysis and comparison of regional and local faunistic records.Results Distinct dispersal and/or vicariant processes seem to be linked to the current distributions of the seven genera known in the YP. In general, the endemic hypogean or benthic crevicular forms (i.e. Diacyclops chakan, D. puuc and Mesocyclops chaci), derived from epigean, tropical, widely distributed forms (some of them South American) may have been among the earliest colonizers of the subterranean habitats in the YP. The distribution of these and other endemic forms seem to be related to the Holocene dry periods that desiccated the largest bodies of water and isolated local populations of different species. These vicariant processes resulted in forms with restricted distributional areas; some of these formed sister species that speciated in geographically close localities but related to a common identifiable ancestor. Overall, the processes of cyclopine colonization of the YP show the influence of the South American fauna, as the closest relatives of some species endemic to the YP are South American forms; the Nearctic influence is low. The cyclopine fauna of the YP is formed by a mixture of Nearctic‐derived (species of Acanthocyclops), Neotropical (i.e. M. edax, M. longisetus, A. panamensis, Thermocyclops inversus and T. tenuis), and epigean and hypogean endemic forms. The highly dynamic geomorphology of the YP and the recent climatic changes in the Holocene define the YP as a peculiar subregion that harbours a diverse fauna of cyclopine copepods with a high endemism.Main conclusion The current distribution of cyclopine copepods reflects relatively recent, post‐Pliocene biogeographical patterns; probably older patterns are involved as well. The eastern coast of the Yucatan is the most recently colonized by cyclopine copepods. Most of the genera are linked with South American forms, and the Nearctic influence is weakly represented. This group has no marine relatives, but there is evidence of vicariant events involving cave‐dwelling forms.

Comparative Postnatal Ontogeny of the Skull in Dromiciops gliroides (Marsupialia: Microbiotheriidae)

Dromiciops gliroides is the single extant representative of the marsupial family Microbiotheriidae. The importance of D. gliroides stems from its peculiar cranial anatomy (specifically the configuration of the tympanic region) and dentition and from its controversial position in the phylogenetic tree of marsupials—a South American form more closely related to Australasian marsupials. We studied the postnatal ontogeny of the skull in D. gliroides by analyzing qualitative and allometric aspects of the development of cranial structures. We compared recently weaned young individuals with adults and described the bivariate and multivariate allometric trends of 14 cranial dimensions for a sample of 37–51 specimens. Most cranial components develop in a way similar to didelphids studied so far. However, some trends (e.g., growth of the orbit) seem particular to D. gliroides. The microbiotheriid bulla of D. gliroides, a structure to which five basicranial bones contribute parts, is already present in its highly derived condition in the youngest specimens of our series. We conclude that except for the bulla, most of the cranial development in D. gliroides is highly conservative and that some peculiarities may be shared with other marsupials of similarly small body size. Data on australidelphians and small-size didelphids are needed to contrast these patterns.

Presencia de palaeolama sp. (artiodactyla: camelidae) del Pliopleistoceno en la costa sur del Perú

We report the oldest record of the genus Palaeolama in Peru; its constitutes one of the oldest records for the genus in South America. The shape and size of the fossil material is comparable to South American forms P. (Hemiauchenia) paradoxa and the smallest forms of P. (Palaeolama) weddellii. The bones were found within unnamed littoral marine deposits near Atiquipa, on the south coast of Peru. The occurrence of the extinct bivalve mollusk, Chlamys vidali, at the base of the section and coquinas of exclusively extant mollusks in the highest marine terrace capping the section indicates an age of about two million years. This age is slightly older or equal to the oldest records of P. (Palaeolama) in North America. The present report confirms that the Lamini were no strangers to Andean ecosystems prior to the Holocene.

One origin for maize

Phylogenetic studies that use many rapidly evolving genes provide great opportunity to address several questions about the domestication of plants and animals, including the timing, location and numbers of domestication events. An excellent example of such a study is Matsuoka et al.'s [1xA single domestication for maize shown by multilocus microsatellite genotyping. Matsuoka, Y.Y. et al. Proc. Natl. Acad. Sci. 2002; 99: 6080–6084Crossref | PubMed | Scopus (571)See all References][1] examination of the origin of maize (Zea mays) using microsatellite data. The land races of maize, domesticated from teosinte, exhibit striking morphological, karyotypic and genetic diversity. This diversity has led some researchers to the conclusion that maize, like many other domesticated plants and animals, had been cultivated several times independently. The results of Matsuoka et al., however, reject the hypothesis of multiple origins and instead show that maize arose via a single domestication event that most likely occurred ∼9000 years ago in Mexico.The authors sampled 193 maize accessions across its entire range prior to Columbus from northern Chile to southeastern Canada, 67 accessions from two subspecies of Mexican teosinte (Z. mays ssp. parviglumis and ssp. mexicana), as well as an outgroup. These were genotyped at 99 microsatellite loci scattered across the genome. All domesticated maize clustered into a monophyletic lineage within spp. parviglumis that had very strong bootstrap support. A contrasting pattern, where different cultivated ‘forms’ cluster with forms of wild relatives, has been found in several crops including cotton, rice and beans. Maize was probably first domesticated in Mexico because the most basal domesticated forms were those from the highlands of Mexico. The data also suggest that maize was first domesticated in the highlands and subsequently spread to the lowlands. This pattern is also consistent with the archaeological evidence.With a few exceptions, geographically similar forms of maize clustered with each other in the microsatellite tree. Population structure analyses identify three major clusters: US maize (with long and slender ears, particularly in the east), Andean maize (often with hand-grenade-shaped ears), and a group that included Mexican and South American forms. Despite the strong support for maize being derived solely from ssp. parviglumis, population structure analyses suggest that there has been modest yet measurable gene flow from ssp. mexicana into the maize of Mexican highlands.Provided the microsatellites have known mutation rates and evolve in accordance with a stepwise mutation model, they can be used to date the divergence of wild and cultivated forms. Based on data from the 33 (of 99 total) loci that fit the criteria, Mexican maize and teosinte diverged 9200 years before present (BP) with 95% confidence intervals spanning 5700 to 13 100 BP. For comparison, the oldest known fossil maize dates to 6250 BP but archaeological evidence suggests maize domestication could have begun as early as 10 000 BP.One major puzzle about maize domestication remains. The most primitive form of maize appears to be from the Mexican highlands, whereas the most likely ancestor of maize (ssp. parviglumis) is currently restricted to the lowlands. There are a number of possible explanations. Perhaps ssp. parviglumis had a larger range at the time when it was domesticated. Another possibility is that the inhabitants first transported ssp. parviglumis to the highlands to domesticate it. Solving this puzzle will most likely require a multidisciplinary effort involving archaeology, ecology, and molecular phylogenetic studies.

A new species of Araripesuchus (Crocodylomorpha, Mesoeucrocodylia) from the lower Cretaceous of Patagonia (Argentina)

ABSTRACT A new species of the genus Araripesuchus from the Albian-Cenomanian locality of the El Chocón (Neuquén Province, Argentina) is described. The diagnosis of the genus is reviewed and its phylogenetic placement within Crocodylomorpha discussed. Araripesuchus is proposed here as being the sister taxon of Neosuchia, corroborating previous phylogenetic analysis. The new species, Araripesuchus patagonicus, differs from the type species, A. gomesii in the relationships of the prefronto-nasal and lachrymo-nasal sutures, the dermal placement of the postorbital bar on the medial side of the jugal, and the greater extension of the squamosals in the skull dorsum. The African species, “Araripesuchus” wegeneri, does not share the diagnostic traits of the genus, and its reassignment to a new genus needs to be considered. The phylogenetic context of Araripesuchus and “A.” wegeneri permits a reanalysis of the role played by their amphiatlantic distribution in the Aptian-Albian. “Araripesuchus” wegeneri and the South American forms might share a pre-Aptian common ancestor, and have been already differentiated and isolated in the African and South American continents by the time of the Aptian-Albian.

Phylogeography of the bushmaster (Lachesis muta: Viperidae): implications for neotropical biogeography, systematics, and conservation

We used mitochondrial gene sequences to reconstruct phylogenetic relationships among subspecies of the bushmaster, Lachesis muta. These large vipers are widely distributed in lowland tropical forests in Central and South America, where three of four allopatric subspecies are separated by montane barriers. Our phylogeny indicates that the four subspecies belong to two clades, the Central American and South American lineages. We use published molecular studies of other taxa to estimate a ‘reptilian mtDNA rate’ and thus temporal boundaries for major lineage divergences in Lachesis. We estimate that the Central and South American forms diverged 18-6 Mya, perhaps due to the uplifting of the Andes, whereas the two Central American subspecies may have diverged 11-4 Mya with the uprising of the Cordillera de Talamanca that separates them today. South American bushmasters from the Amazon Basin and the Atlantic Forest are not strongly differentiated, perhaps due to episodic gene flow during the Pleistocene, when suitable habitat for this species was at times more continuous. Our results agree with previous evidence that genetic divergence among some neotropical vertebrates pre-dated Pleistocene forest fragmentation cycles and the appearance of the Panamanian Isthmus. Based on morphological, behavioral, and molecular evidence, we recognize three species of Lachesis. In addition to L. muta, the widespread South American form, the Central American forms are treated as distinct species (L. meknocephak and L. stenophrys), each deserving of special conservation status due to restricted distribution and habitat destruction.

Phylogeography of the bushmaster (Lachesis muta: Viperidae): implications for neotropical biogeography, systematics, and conservation

We used mitochondrial gene sequences to reconstruct phylogenetic relationships among subspecies of the bushmaster,Lachesis muta. These large vipers are widely distributed in lowland tropical forests in Central and South America, where three of four allopatric subspecies are separated by montane barriers. Our phylogeny indicates that the four subspecies belong to two clades, the Central American and South American lineages. We use published molecular studies of other taxa to estimate a «reptilian mtDNA rate» and thus temporal boundaries for major lineage divergences inLachesis. We estimate that the Central and South American forms diverged 18–6 Mya, perhaps due to the uplifting of the Andes, whereas the two Central American subspecies may have diverged 11–4 Mya with the uprising of the Cordillera de Talamanca that separates them today. South American bushmasters from the Amazon Basin and the Atlantic Forest are not strongly differentiated, perhaps due to episodic gene flow during the Pleistocene, when suitable habitat for this species was at times more continuous. Our results agree with previous evidence that genetic divergence among some neotropical vertebrates pre-dated Pleistocene forest fragmentation cycles and the appearance of the Panamanian Isthmus. Based on morphological, behavioral, and molecular evidence, we recognize three species ofLachesis. In addition toL. muta, the widespread South American form, the Central American forms are treated as distinct species (L. melanocephalaandL. stenophrys), each deserving of special conservation status due to restricted distribution and habitat destruction.

Isoenzymatic variability in seeds of some spanish common beans ( Phaseolus vulgaris L. Leguminosae): Relation to their domestication centers

Phaseolus vulgaris is an important crop species. The cultivated common bean derives from wild forms in two independent domestication centers in Mesoamerica and South America. We report a study of electrophoretic patterns of seven isoenzymatic systems in 29 samples of P. vulgaris seeds. Nineteen of them are from northern Spain, four are from Mesoamerican and six are South American forms. The isoenzymatic activity of esterases, cytochrome c oxidase, acid phosphatase, alkaline phosphatase, alcohol dehydrogenase, shikimate dehydrogenase and glutamate oxaloacetic transaminase were studied. On the basis of electrophoretic patterns of seed isoenzymes, four groups can be recognized using clustering procedures (UPGMA). Comparing this biochemical information with previous morpho-agronomic studies, the possible primary domestication centers of the cultivars are discussed.

Towards an Ammonite zonation for the Toarcian of North America

Toarcian deposits in North America occur on the craton from southwestern Alberta to northern Alaska and the Canadian Arctic, and on the accreted terranes of the Cordillera from east-central Oregon to southern Alaska. The complicated tectonic history of the Cordillera and the incomplete nature of much of the ammonite fauna have precluded a comprehensive analysis of the Toarcian biostratigraphy. Recent studies in the Queen Charlotte Islands however, have uncovered a diverse and well preserved fauna from a relatively uncomplicated section, which is providing the base for a North American zonation. The Toarcian of North America can be divided into six zones. The base is defined by the first appearance of Dactylioceras above the last occurrence of Amaltheus.. Zone 1 contains such forms as Dactylioceras kanense Mclearn,, Tiltoniceras propinquum ( Whiteaves)) and Taffertia sp. Zone 2 includes Harpoceras cf. exaratum ( Young & Bird)), Harpoceras chrysanthemum ( Yokoyama)) and Hildaites levisoni ( Simpson)). Zone 3 is marked by the appearance of species of Phymatoceras, Rarenodia and Peronoceras and also includes the Tehyan Leukadiella,, the first report of this genus in North America. Rare and poorly preserved specimens of Hildoceras? are found in this zone as well. Zone 4 contains a diverse Phymatoceras and Peronoceras fauna, together with rare species of Mercaticeras, Pseudomercaticeras, Paroniceras and Denckmannia.. Zone 5 contains Grammoceras, Podagrosites,, and Phymatoceras copiapense ( Moericke)). Zone 6 includes species of the genera Hammatoceras, Sphaerocoeloceras, “Atacamiceras”, “Phlyseogrammoceras”, Dumortieria, Pleydellia and a new genus from the Phymatoceratinae. The Toarcian/Aalenian boundary is defined by the last occurrences of the above forms and by the appearance of Tmetoceras scissum ( Benecke)), Troitsia westermanni Poulton & Tipper and Leioceras sp.. The Toarcian fauna of North America shows marked affinities to western Pacific, South American and Mediterranean forms.