Vitamin C (L-ascorbic acid) has important antioxidant and metabolic functions in both plants and animals, but humans, and a few other animal species, have lost the capacity to synthesize it Plant-derived ascorbate is thus the major source of vitamin C in the human diet Although the biosynthetic pathway of L-ascorbic acid in animals is well understood, the plant pathway has remained unknown-one of the few primary plant metabolic pathways for which this is the case L-ascorbate is abundant in plants (found at concentrations of 1-5 mM in leaves and 25 mM in chloroplasts) and may have roles in photosynthesis and transmembrane electron transport We found that D-mannose and L-galactose are efficient precursors for ascorbate synthesis and are interconverted by GDP-D-mannose-3,5-epimerase We have identified an enzyme in pea and Arabidopsis thaliana, L-galactose dehydrogenase, that catalyses oxidation of L-galactose to L-galactono-1,4-lactone We propose an ascorbate biosynthesis pathway involving GDP-D-mannose, GDP-L-galactose, L-galactose and L-galactono-1,4-lactone, and have synthesized ascorbate from GDP-D-mannose by way of these intermediates in vitro The definition of this biosynthetic pathway should allow engineering of plants for increased ascorbate production, thus increasing their nutritional value and stress tolerance

The biosynthetic pathway of vitamin C in higher plants

New World frogs recently placed in a single, enormous family (Brachycephalidae) have direct development and reproduce on land, often far away from water. DNA sequences from mitochondrial and nuclear genes of 344 species were analyzed to estimate their relationships. The molecular phylogeny in turn was used as the basis for a revised classification of the group. The 882 described species are placed in a new taxon, Terrarana, and allocated to four families, four subfamilies, 24 genera, 11 subgenera, 33 species series, 56 species groups, and 11 species subgroups. Systematic accounts are provided for all taxa above the species level. Two families (Craugastoridae and Strabomantidae), three subfamilies (Holoadeninae, Phyzelaphryninae, and Strabomantinae), six genera (Bryophryne, Diasporus, Haddadus, Isodactylus, Lynchius, and Psychrophrynella), and two subgenera (Campbellius and Schwartzius) are proposed and named as new taxa, 13 subspecies are considered to be distinct species, and 613 new combinations are formed. Most of the 100 informal groups (species series, species groups, and species subgroups) are new or newly defined. Brachycephalus and Ischnocnema are placed in Brachycephalidae, a relatively small clade restricted primarily to southeastern Brazil. Eleutherodactylidae includes two subfamilies, four genera, and five subgenera and is centered in the Caribbean region. Craugastoridae contains two genera and three subgenera and is distributed mainly in Middle America. Strabomantidae is distributed primarily in the Andes of northwestern South America and includes two subfamilies, 16 genera, and three subgenera. Images and distribution maps are presented for taxa above the species level and a complete list of species is provided. Aspects of the evolution, biogeography, and conservation of Terrarana are discussed.

/pdf/new-world-direct-developing-frogs-anura-terrarana-molecular-3t73l13ttm.pdf

New World direct-developing frogs (Anura: Terrarana): Molecular phylogeny, classification, biogeography, and conservation

Crabs of the family Grapsidae are abundant organisms in most intertidal communities. However, relatively few species live in complete independence of the sea1. Of those species that do, Jamaica's nine endemic species of land crabs are unique in their exceptional adaptations to terrestrial life, which include the only active brood-care for larvae and juveniles known in crabs2,3,4,5,6. These adaptations, and the morphological similarity to a group of southeast Asian land-dwelling crabs, have raised the question of the number and age of land invasions of the Jamaican species. Here we present molecular evidence that Jamaican land crabs represent a single adaptive radiation from a marine ancestor that invaded terrestrial habitats only 4 million years (Myr) ago. A Late-Tertiary origin has also been found for lizards and frogs of Jamaica7,8,9 and probably reflects the Mid-Tertiary inundation of that island10.

/pdf/rapid-evolution-to-terrestrial-life-in-jamaican-crabs-37mx0h61nd.pdf

Rapid evolution to terrestrial life in Jamaican crabs

Approximately one-half of all species of amphibians occur in the New World tropics, which includes South America, Middle America, and the West Indies. Of those, 27% (801 species) belong to a large assemblage, the eleutherodactyline frogs, which breed out of water and lay eggs that undergo direct development on land. Their wide distribution and mode of reproduction offer potential for resolving questions in evolution, ecology, and conservation. However, progress in all of these fields has been hindered by a poor understanding of their evolutionary relationships. As a result, most of the species have been placed in a single genus, Eleutherodactylus, which is the largest among vertebrates. Our DNA sequence analysis of a major fraction of eleutherodactyline diversity revealed three large radiations of species with unexpected geographic isolation: a South American Clade (393 sp.), a Caribbean Clade (171 sp.), and a Middle American Clade (111 sp.). Molecular clock analyses reject the prevailing hypothesis that these frogs arose from land connections with North and South America and their subsequent fragmentation in the Late Cretaceous (80–70 Mya). Origin by dispersal, probably over water from South America in the early Cenozoic (47–29 million years ago, Mya), is more likely.

http://www.redciencia.cu/geobiblio/paper/2007_Heinicke_etal_Major%20Caribbean%20and%20Central%20American%20frog%20faunas.pdf

Major Caribbean and Central American frog faunas originated by ancient oceanic dispersal

http://safarmer.com/indo-eurasian/snakes.brain.pdf

Snakes as agents of evolutionary change in primate brains

We present an initial evaluation of relationships among a diverse sample of 215 species of snakes (8% of the world snake fauna) representing nine of the 16 commonly-recognized families. Allelic variation at four slow-evolving. protein-coding loci, detected by starch-gel electrophoresis, was found to be informative for estimating relationships among these species at several levels. The numerous alleles detected at these loci [Arp-2 (42 alleles). Ltlh-2 (43), Mdh-1 (29), Pgm (Z)] provided unexpected clarity in partitioning these taxa. Most congeneric species and several closely-related genera have the same allele at all four loci or differ at only a single locus. At thc other extreme are those species with three or four unique alleles; these taxa cannot be placed in this analysis. Species sharing two or three distinctive alleles are those most clearly separated into clades. Typhlopids, pythonids, viperids, and elapids were resolved into individual clades. whereas bods were separated into boincs and erycines, and colubrids appeared as scveral distinct clades (colubrines, natricines, psammophines, homalopsines, and xenodontines). Viperids were recognized as a major division containing three separate clades: Asian and American crotalines. Pabearctic and Oriental viperines, and Ethiopian causines. The typhlopids were found to be the basal clade, with the North American erycine boid Chrrrino and the West Indian woodsnakes Tropidophi, Y near the base. A number of species and some small clades were not allocated because of uninformative (common, unique, or conflicting) alleles. Of the 21 S species examined, five to eight appear to have been misplaced in the analysis of these electrophoretic data.

Snake relationships revealed by slow-evolving proteins: a preliminary survey

Antisera to serum albumins from five West Indian species of the frog genus Eleutheroductylus were prepared, and the reciprocal immunological distances (IDs) obtained were used to provide a time frame for the evolution of this group in the West Indies. One-way IDS were obtained to 25 additional species within the genus, with emphasis on those from the West Indies. These immunological data support both a recent classification of Eleutheroductylus based on an analysis of slow-evolving allozyme loci, and the monophyly of the 17 native Jamaican species as indicated by a more comprehensive electrophoretic study. This is in contrast to the results of morphological studies supporting multiple invasions of Jamaica by Eleutherodactylus. Within the subgenus Euhyas, IDS ranged from6–27 between Jamaican species, whereas between species on different islands the range was29–67. The subgenus Syrrhophus in southern North America was found to be the sister group to the subgenus Euhyus, a western Caribbean clade. Pelorius, a subgenus restricted to Hispaniola, was found to be the sister group of the subgenus Eleutheroductylus in the West Indies. The largest IDs obtained for West Indian species were those between the two major groups, the subgenera Eleutheroductylus and Euhyas.



The albumin immunological clock for Eleutheroductylus was calibrated with three events in the geologic history of the Caribbean: the breakup of the proto-Antilles (65-75 million years before present [mybp]), the emergence of Jamaica (20-30 mybp), and the uplift of the Blue Mountains in Jamaica (5-10 mybp). Immunological distances corresponding to those events yield a calibration of 1 ID=0.60 million years (my), the same as that previously obtained for other groups of amphibians and thus supports the use of albumin immunological distance as a molecular chronometer in the genus Eleutherodactylus

/pdf/albumin-evolution-in-west-indian-frogs-of-the-genus-38a265shen.pdf

Albumin evolution in West Indian frogs of the genus Eleutherodactylus (Leptodactylidae): Caribbean biogeography and a calibration of the albumin immunological clock

S. Blair Hedges

Papers

Snake relationships revealed by slow-evolving proteins: a preliminary survey

Albumin evolution in West Indian frogs of the genus Eleutherodactylus (Leptodactylidae): Caribbean biogeography and a calibration of the albumin immunological clock