Etyid crabs (Crustacea,Decapoda) from mid‐Cretaceous Reefal strata of Navarra,northern Spain

Abstract: All known etyid crabs (Crustacea, Decapoda) from the upper Albian – lower Cenomanian Aldoirar coralgal‐dominated patch reef (Albeniz Unit, Eguino Formation), as exposed at the disused Koskobilo quarry in Navarra, northern Spain, are described, discussed and illustrated. A new species, Xanthosia koskobiloensis, the first member of the genus on record from southern Europe, is erected, and a variety that appears closely related to this, Xanthosia cf. X. koskobiloensis, is recognised. This new taxon could be a forerunner of the early Palaeocene (Danian) Xanthosia gracilis from Fakse (Sjælland, eastern Denmark), with which it shares a morphologically closely similar carapace. On the basis of a revised overview here of all species assigned to it, the genus Xanthosia may have evolved in an environment dominated by deposition of siliciclastics, rather than chalks. In addition, Etyxanthosia fossa has been collected at Koskobilo, and as the distribution of all known specimens demonstrates, E. fossa inhabited various environments. Another new species, Caloxanthus paraornatus, is closely similar as well to a species from Fakse, Caloxanthus ornatus, and constitutes the first record of the genus for southern Europe.     

Pollination biology of Prunus mahaleb L.: deferred consequences of gender variation for fecundity and seed size

This study describes the reproductive biology of Prunus mahaleb, a rosaceous treelet, in a southeastern Spanish population. The species is gynodioecious with 55.4% of the plants being male-fertile and 44.6% presenting non-functional, shrunken anthers with no pollen, and behaving as functional females. Individual trees produced the same flower morph in four consecutive study years. Fruit set in bagged inflorescences was absent in male-sterile trees and was very reduced in male-fertiles. Open-pollinated flowers of male-fertiles showed greater fruit set (x?= 29.1%) than male-steriles (x?= 25.3%). Average fruit set in three experimental treatments (control, selfed, and crossed) were 29.05%, 41.9% and 38.6%, respectively, for male-fertile trees; those for male-steriles were 25.3%, 0% and 39.2%, respectively. Seeds from male-sterile plants were heavier (71.33 mg) than those of male-fertile plants (66.05 mg) but did not differ in germination ability. Male-fertile and male-sterile trees differ significantly in average nectar concentration (73.5% and 55.9%, respectively) and nectar volume secreted/flower and day (0.142 μl and 0.171 μl, respectively). A total of 41 species of insect flower visitors were recorded. Calliphorid and tachinid flies (41.97% of total visits), and andrenid bees (30.30%), were the most frequent visitors. The diversity of insect visitors was greater in male-fertile trees. Bees and flies accounted for 50.5% and 49.5%, respectively of total visits to male-fertile trees. Flies were far more frequent than bees at male-sterile flowers (76.9% and 23.1%, respectively). Male-sterile trees received higher average visitation (47 insects/census) than male-fertile trees (32 insects/census). Individual trees. showed a relative constancy of the fecundity rankings between years. Fruit production was significantly higher in male-sterile trees, with a four-year average of 6558 fruits, in contrast with male-fertile trees which yielded 4670 fruits. This 1.77-fold difference in favour of male-sterile trees over malefertiles was not compensated by the greater fruit set of the latter. This is attributable to the lower outcrossing rate of male-fertiles, estimated as 52.68% from seed mass data. In addition, greater seed mass of female progeny, and higher visitation rate by insects might explain the maintenance of this polymorphism. These results have far-reaching implications for the demography and seed-dispersal ecology of this endozoochorus species.     

An artificial chimeric derivative of Citrus viroid V involves the terminal left domain in pathogenicity

The recently described Citrus viroid V (CVd-V) induces, in Etrog citron, mild stunting and very small necrotic lesions and cracks, sometimes filled with gum. As Etrog citron plants co-infected with Citrus dwarfing viroid (CDVd) and CVd-V show synergistic interactions, these host–viroid combinations provide a convenient model to identify the pathogenicity determinant(s). The biological effects of replacing limited portions of the rod-like structure of CVd-V with the corresponding portions of CDVd are reported. Chimeric constructs were synthesized using a novel polymerase chain reaction-based approach, much more flexible than those based on restriction enzymes used in previous studies. Of the seven chimeras (Ch) tested, only one (Ch5) proved to be infectious. Plants infected with Ch5 showed no symptoms and, although this novel chimera was able to replicate to relatively high titres in singly infected plants, it was rapidly displaced by either CVd-V or CDVd in doubly infected plants. The results demonstrate that direct interaction(s) between structural elements in the viroid RNA (in this case, the terminal left domain) and as yet unidentified host factors play an important role in modulating viroid pathogenicity. This is the first pathogenic determinant mapped in species of the genus Apscaviroid .     

Seed survival and dispersal of an endemic Atlantic forest palm: the combined effects of defaunation and forest fragmentation

About 45 palm species occur in the Atlantic forest of Brazil, and most of them are affected by loss of seed dispersers resulting from forest fragmentation and hunting. Here we report the effects of habitat loss and defaunation on the seed dispersal system of an endemic palm, Astrocaryum aculeatissimum . We evaluated seed removal, insect and rodent seed predation, and scatter-hoarding in nine sites, ranging from 19 ha to 79 000 ha. We report the seedling, juvenile and adult palm densities in this range of sites. Endocarps remaining beneath the parent palm had a higher probability of being preyed upon by insects in small, mostly fragmented and more defaunated sites. The frequency of successful seed removal, scatter-hoarding and consumption by rodents increased in the larger, less defaunated sites. Successful removal and dispersal collapsed in small (< 1000 ha), highly defaunated sites and frequently resulted in low densities of both seedlings and juveniles. Our results indicate that a large fraction of Atlantic forest palms that rely on scatter-hoarding rodents may become regionally extinct due to forest fragmentation and defaunation. Current management practices including palm extraction and hunting pressure have a lasting effect on Atlantic forest palm regeneration by severely limiting successful recruitment of prereproductive individuals. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 141–149.     

Cladosporium fulvum (syn. Passalora fulva), a highly specialized plant pathogen as a model for functional studies on plant pathogenic Mycosphaerellaceae

Taxonomy:  Cladosporium fulvum is an asexual fungus for which no sexual stage is currently known. Molecular data, however, support C. fulvum as a member of the Mycosphaerellaceae, clustering with other taxa having Mycosphaerella teleomorphs . C. fulvum has recently been placed in the anamorph genus Passalora as P. fulva . Its taxonomic disposition is supported by its DNA phylogeny, as well as the distinct scars on its conidial hila, which are typical of Passalora , and unlike Cladosporium s.s. , which has teleomorphs that reside in Davidiella , and not Mycosphaerella .
Host range and disease symptoms:  The presently known sole host of C. fulvum is tomato (members of the genus Lycopersicon ). C. fulvum is mainly a foliar pathogen. Disease symptoms are most obvious on the abaxial side of the leaf and include patches of white mould that turn brown upon sporulation. Due to stomatal clogging, curling of leaves and wilting can occur, leading to defoliation.
C. fulvum as a model pathogen:  The interaction between C. fulvum and tomato is governed by a gene-for-gene relationship. A total of eight Avr and Ecp genes, and for four of these also the corresponding plant Cf genes, have been cloned. Obtaining conclusive evidence for gene-for-gene relationships is complicated by the poor availability of genetic tools for most Mycosphaerellaceae – plant interactions. Newly developed tools, including Agrobacterium -mediated transformation and RNAi, added to the genome sequence of its host tomato, which will be available within a few years, render C. fulvum attractive as a model species for plant pathogenic Mycosphaerellaceae.
Useful websites:  http://www.sgn.cornell.edu/help/about/index.html ; http://cogeme.ex.ac.uk     

Patterns of diversification on old volcanic islands as revealed by the woodlouse-hunter spider genus Dysdera (Araneae, Dysderidae) in the eastern Canary Islands

Long-term erosion and subsidence cause dramatic alterations in the physical and ecological features of oceanic islands. Although oceanic islands have been extensively used as models for the study of speciation, little attention has been given to investigating evolutionary patterns in old volcanic islands that have suffered severe climatic degradation. The spider genus Dysdera has diversified across the Canary Islands and has evolved endemisms in the low-elevation, xeric eastern islands, which sharply contrast with the younger, higher, and more humid western islands. A combined phylogenetic analysis of seven mitochondrial and nuclear genes reveals that the eastern Canaries were colonized twice, although only one lineage underwent in situ diversification. Origins of the speciose lineage remain obscure, but probably preceded diversification of present-day Iberian and North African species. A second colonization of the eastern Canaries from North Africa has occurred in more recent times. Molecular analyses reveal several instances of geographically coherent cryptic lineages further supported by morphometric evidence. Analyses of diversification rates suggest deceleration of diversification over the course of time, and this is compatible with increasing extinction rates due to drastic yet continuous ecological changes. Extinction may also explain incongruent patterns of morphological differentiation and species coexistence. Despite a general trend towards community impoverishment, there is also evidence for recent speciation events linked to ecological shifts, which may illustrate the origins of nonspeciose relic lineages on islands.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 589–615.