Restoring phylogenetic diversity through facilitation

Phylogenetic diversity enhances ecosystem functioning but restoration ecology has not taken advantage of this knowledge. We propose plant facilitation as a mechanism to promote phylogenetic diversity in restoration practices. We planted three functionally different species (Gypsophila struthium, Sedum album, and Limonium sucronicum) in a degraded gypsum ecosystem in Spain and found that after 7 years, the species with nurse traits (G. struthium) survived longer and facilitated the establishment of new species forming phylogenetically diverse neighborhoods. These facilitation‐driven phylodiverse communities may potentially produce a cascade of benefits on ecosystem functioning.     

The MMS22L–TONSL heterodimer directly promotes RAD51‐dependent recombination upon replication stress

Homologous recombination (HR) is a key pathway that repairs DNA double‐strand breaks (DSBs) and helps to restart stalled or collapsed replication forks. How HR supports replication upon genotoxic stress is not understood. Using in vivo and in vitro approaches, we show that the MMS22L–TONSL heterodimer localizes to replication forks under unperturbed conditions and its recruitment is increased during replication stress in human cells. MMS22L–TONSL associates with replication protein A (RPA)‐coated ssDNA, and the MMS22L subunit directly interacts with the strand exchange protein RAD51. MMS22L is required for proper RAD51 assembly at DNA damage sites in vivo, and HR‐mediated repair of stalled forks is abrogated in cells expressing a MMS22L mutant deficient in RAD51 interaction. Similar to the recombination mediator BRCA2, recombinant MMS22L–TONSL limits the assembly of RAD51 on dsDNA, which stimulates RAD51‐ssDNA nucleoprotein filament formation and RAD51‐dependent strand exchange activity in vitro. Thus, by specifically regulating RAD51 activity at uncoupled replication forks, MMS22L–TONSL stabilizes perturbed replication forks by promoting replication fork reversal and stimulating their HR‐mediated restart in vivo.     

Sedentary life style of Neotropical sedge wrens promotes song imitation

To what extent has the style of song development among songbirds coevolved with other life history strategies? Among Cistothorus wrens in North America, it seems that sedentary or site-faithful habits of marsh wrens, C. palustris, favour song imitation, but seminomadic habits of sedge wrens, C. platensis, favour song improvisation, whereby each male generates a large but unique song repertoire. In this study, we tested whether more sedentary populations of sedge wrens in the Neotropics would imitate songs. At our primary study site near Cartago, Costa Rica, breeding birds were colour-banded during 1995 and 1996, and follow-up surveys revealed that the birds remained at this site the year round. Extensive tape recording and analysis of songs showed that males had large song repertoires (200-300+ songs), and that many songs were shared among neighbouring males. In addition, males only 27 km distant, at La Pastora, used different songs. Furthermore, matched countersinging, in which two males answer each other with identical song types, was recorded near Brasilia, in Brazil. The sharing of songs among permanent neighbours, microgeographical variation in song, and matched countersinging can be achieved only through song imitation, thus revealing a striking difference in the style of song development among different populations of the sedge wren. In the Neotropics, having predictable neighbours throughout life appears to have favoured song imitation, so that individuals can interact using a common, learned code typical of the local population; among more mobile populations in North America, however, individuals improvise large repertoires of species-typical songs, thereby enabling singing males to communicate with any individual, no matter what the population of origin. Strategies of song development must correlate with life history features, and further surveys are needed to make sense of the great diversity of singing behaviours among songbirds. Copyright 1999 The Association for the Study of Animal Behaviour.     

Pollination ecology and breeding system of the very narrow coastal endemic Seseli farrenyi (Apiaceae). Effects of population fragmentation

The reproductive biology of Seseli farrenyi (Apiaceae), a very narrow endemic to Cape Creus (Catalonia, Spain), including flowering timing patterns, quantity and quality of pollination services (type and frequency of pollinators, pollen carryover, pollen deposition on stigmas and reproductive success measured as fruit set), and breeding system was studied. Given the decline of population size detected in the last twenty years, we also analyzed the effects of fragmentation on pollination mechanisms. Protandry along with strong synchrony of floral development within umbels and sequential inflorescence emission within individual stalks, produces sexual phase alternation that promotes a strong outcrossing despite its non-specific pollination system and its (at least partial) self-compatibility. This pronounced xenogamy is supported by results of the insect exclusion test, hand-pollination experiments, and high P/O ratio. S. farrenyi flowers received visits from at least 28 species of insects, including wasps, small bees, ants, flies, syrphid flies, beetles and stink bugs, with different pollen carry-overs. Heterospecific pollen on stigmas decreased notably during the season (50% to 2.5%), averaging 12%. In the small population the stigmatic pollen loads and seed set decreased, but there was no effect of pollinator visitation rates. It was more affected by the composition of pollinators and their efficiency. The wind had a considerable effect on the plant. Some conservation measures are proposed.     

<Emphasis Type="Italic">Theba pisana</Emphasis> (Müller, 1774) (Gastropoda,Helicidae) and other alien land molluscs species in Argentina

The presence and distribution in Argentina of the invasive snail species Theba pisana is presented on the basis of a survey carried out in 10 beach resorts along the Atlantic coast of Buenos Aires Province. Additionally, complementary information and complete revision of material of other exotic terrestrial gastropods housed in museum collections was carried out, reporting herein seven new species for Argentina (Otala punctata, Hawaiia minuscula, Paralaoma servilis, Opeas goodalli, Vallonia pulchella, Vertigo ovata and Pupisoma dioscoricola), one for Colombia (Subulina octona), and two for Peru (S. octona and P. dioscoricola). At present, 42 introduced species of terrestrial gastropods have been recorded in nine countries of South America (Argentina, Bolivia, Brazil, Chile, Colombia, Paraguay, Peru, Uruguay and Venezuela). The most likely pathways for introduction of terrestrial gastropods, at least in Argentina, are horticultural development and urban and suburban transformation of original natural habitats.     

Nucleotide sequence analysis of the lemur beta-globin gene family: evidence for major rate fluctuations in globin polypeptide evolution

Lemur beta-related globin genes have been isolated and sequenced. Orthology of prosimian and human epsilon-, gamma-, and beta-related globin genes was established by dot-matrix analysis. All of these lemur globin genes potentially encode functional beta-related globin polypeptides, though precisely when the gamma-globin gene is expressed remains unknown. The organization of the 18-kb brown lemur beta-globin gene cluster (5' epsilon-gamma-[psi eta-delta]-beta 3') is consistent with its evolution by contraction via unequal crossing-over from the putative ancestral mammalian beta-globin gene cluster (5' epsilon-gamma- eta-delta-beta 3'). The dwarf lemur nonadult globin genes are arranged as in the brown lemur. Similar levels of synonymous (silent) nucleotide substitutions and noncoding DNA sequence differences have accumulated between species in all of these genes, suggesting a uniform rate of noncoding DNA divergence throughout primate beta-globin gene clusters. These differences are comparable with those observed in the nonfunctional psi eta pseudogene and have therefore accumulated at the presumably maximal neutral rate. In contrast, nonsynonymous (replacement) nucleotide substitutions show a significant heterogeneity in distribution for both the same gene in different lineages and different genes in the same lineage. These major fluctuations in replacement but not silent substitution rates cannot be attributed to changes in mutation rate, suggesting that changes in the rate of globin polypeptide evolution in primates is not governed solely by variable mutation rates.      

Testa Structure and Histochemistry Related to Water Uptake in Leucaena leucocephala Lam. (De Wit)

The testa structure and histochemistry of Leucaena leucocephalaLam. (De Wit) seed were investigated by bright-field and fluorescencelight microscopy, and scanning electron microscopy. The testaconsisted of several separate layers. Externally there was anon-cellular layer made up of two parts differing in histochemicalcharacteristics: an "outer strip" rich in hydrophilic substances,and a "thicker part" showing the occurrence of phenolics, involvedin water impermeability control. A second underlying thin layerwas formed by the palisade cell caps, joined one to another.This layer, which we called the "cap film ", became metachromaticreddish-blue with Toluidine O pH 4·4 and reacted positivelywith Alcian blue pH 2·5, revealing the presence of polysaccharidehydrophilic material. The palisade cells consisted of two parts,having different structures and histochemical features. Thefurrowed upper part revealed the simultaneous presence of hydrophilicand hydrophobic substances in the furrows and in the ribs respectively.The corresponding periclinal section showed a central daisy-likepattern (made up of hydrophilic material) with a small chainof tiny spots (made up of hydrophobic material) all around it.The inner part of the palisade cells was also furrowed, butshowed only hydrophobic substances of lipidic nature, detectedby Auramine O and Phosphine 3R. The light line was found tobe rich in callose as shown by the strong fluorescence inducedby Aniline Blue. These findings add supporting evidence of thecomplex structure and composition of the Leucaena leucocephalatesta.Copyright 1994, 1999 Academic Press Leucaena leucocephala, testa, structure, histochemistry, water entry