Retrotransposon-gene associations are widespread among D. melanogaster populations

We have surveyed 18 natural populations of Drosophila melanogaster for the presence of 23 retrotransposon-gene-association alleles (i.e., the presence of an LTR retrotransposon sequence in or within 1,000 bp of a gene) recently identified in the sequenced D. melanogaster genome. The identified associations were detected only in the D. melanogaster populations. The majority (61%) of the identified retrotransposon-gene associations were present only in the sequenced strain in which they were first identified. Thirty percent of the associations were detected in at least one of the natural populations, and 9% of the associations were detected in all of the D. melanogaster populations surveyed. Sequence analysis of an association allele present in all populations indicates that selection is a significant factor in the spread and/or maintenance of at least some of retroelement-gene associations in D. melanogaster.     

Positive selection at reproductive ADAM genes with potential intercellular binding activity

Many genes with a role in reproduction, including those implicated in fertilization and spermatogenesis, have been shown to evolve at a faster rate relative to genes associated with other functions and tissues. These survey studies usually group a wide variety of genes with different characteristics and evolutionary histories as reproductive genes based on their site of expression or function. We have examined the molecular evolution of the ADAM (a disintegrin and metalloprotease) gene family, a structurally and functionally diverse group of genes expressed in reproductive and somatic tissue to test whether a variety of protein characteristics such as phylogenetic clusters, tissue of expression, and proteolytic and adhesive function can group fast evolving ADAM genes. We found that all genes were evolving under purifying selection (d(N)/d(S) < 1), although reproductive ADAMs, including those implicated in fertilization and spermatogenesis, evolved at the fastest rate. Genes with a role in binding to cell receptors in endogenous tissue appear to be evolving under purifying selection, regardless of the tissue of expression. In contrast, positive selection of codon sites in the disintegrin/cysteine-rich adhesion domains was detected exclusively in ADAMs 2 and 32, two genes expressed in the testis with a potential role in sperm-egg adhesion. Positive selection was detected in the transmembrane/cytosolic tail region of ADAM genes expressed in a variety of tissues.     

Modifications of the falciform process in the eye of beloniformes (Teleostei: Atherinomorpha): evolution of a curtain-like septum in the eye

In order to comparatively analyze curtain-like septa in the eyes of visually orientated "close-to-surface-predators" among atherinomorph teleosts, we examined the eyes of 24 atherinomorph species under a binocular microscope with regard to the falciform process and related structures in the vitreous cavity. Additionally, falciform process samples were analyzed by transmission electron microscopy. All the studied representatives of the Cyprinodontiformes and Atheriniformes, and of one of the beloniform suborder, Adrianichthyioidei, possess a "typical" processus falciformis. In the eyes of the representatives of the other beloniform suborder, Belonoidei, however, pigmented structures that originate in the region of the optic disc and protrude into the vitreous cavity were noted. In the Hemiramphidae (halfbeaks) and Exocoetidae (flying fishes) these pigmented structures have a more cone-like shape, whereas in the Belonidae (needlefishes) and Scomberesocidae (sauries) horizontally oriented heavily pigmented curtain-like septa occur that divide the vitreous cavity dorsoventrally. It is suggested that the "typical" processus falciformis represents a plesiomorphic feature within the Atherinomorpha, whereas the pigmented modifications of the falciform process must be seen as a synapomorphic character state of the Belonoidei. The curtain-like septum of the Belonidae and Scomberesocidae might have evolved from the cone-like structures that are found in the Exocoetoidea. The functional significance of the pigmented structures in the eye is as yet not clear, except for the curtain-like septum found in Belonidae. It might play a role in visual orientation near the water surface at Snell's window.     

Marsupial relationships and a timeline for marsupial radiation in South Gondwana

Recent marsupials include about 280 species divided into 18 families and seven orders. Approximately 200 species live in Australia/New Guinea. The remaining species inhabit South America with some of these secondarily ranging into North America. In this study, we examine marsupial relationships and estimate their divergences times using complete mitochondrial (mt) genomes. The sampling, which includes nine new mtDNAs and a total number of 19 marsupial genomes, encompasses all extant orders and 14 families. The analysis identified a basal split between Didelphimorphia and remaining orders about 69 million years before present (MYBP), while other ordinal divergences were placed in Tertiary times. The monotypic South American order Microbiotheria (Dromiciops gliroides, Monito del Monte) was solidly nested among its Australian counterparts. The results suggest that marsupials colonized Australia twice from Antarctica/South America and that the divergence between Microbiotheria and its Australian relatives coincided with the geological separation of Antarctica and Australia. Within Australia itself, several of the deepest divergences were estimated to have taken place close to the Eocene/Oligocene transition.     

AFLP analysis of phylogenetic relationships among myrmecophytic species of Macaranga (Euphorbiaceae) and their allies

The palaeotropic pioneer tree genus Macaranga Thouars (Euphorbiaceae) is characterized by various types of mutualistic interactions with specific ant partners (mainly Crematogaster spp.). About 30 species are obligate ant-plants (myrmecophytes). We used amplified fragment length polymorphism (AFLP) markers to assess phylogenetic relationships among 108 Macaranga specimens from 43 species, including all available taxa from the three sections known to contain myrmecophytes. Eight primer combinations produced 426 bands that were scored as presence/absence characters. Banding patterns were analyzed phenetically, cladistically and by principal coordinates analysis. Monophyly of section Pruinosae is clearly supported. There is also good evidence for a monophyletic section Pachystemon that includes the puncticulata group. The monophyly of section Winklerianae and relationships between the three sections remain ambiguous. Section Pachystemon is subdivided into four well-supported monophyletic subclades that presumably correspond to taxonomic entities.We acknowledge the support by the Deutsche Forschungsgemeinschaft (DFG Fi606/4-1, DFG We1830/2-1, 4-1 and 4-2), which in part was granted in the frame of the DFG-SPP 1127 Radiations: origins of biological diversity. Part of the plant material was kindly supplied by Dr. H. Feldhaar (University of Würzburg), Dr. U. Moog (University of Kassel) and Dr. F. Slik (Leiden University Branch, Nationaal Herbarium Nederland). We thank the University of Malaysia (Dr. Rosli b. Hashim) and Taman Taman Sabah (Datuk Lamri Ali; Dr. J. Nais) for permits and logistic support, and EPU for permission to conduct research in Malaysia.     

Adaptive modifications of the photosynthetic apparatus in Euglena gracilis Klebs exposed to manganese excess

Summary. Asynchronous cultures of wild-type Euglena gracilis were tested for their morphophysiological response to 10mM MnSO₄. Growth was only moderately slowed (15%), while oxygen evolution was never compromised. Inductively coupled plasma analyses indicated that the Mn cell content doubled with respect to controls, but no signs of localised accumulation were detected with X-ray microanalysis. Evident morphological alterations were found at the plastid level with transmission electron microscopy and confocal laser scanning microscopy. An increase in the plastid mass, accompanied by frequent aberrations of chloroplast shape and of the organisation of the thylakoid system, was observed. These aspects paralleled a decrease in the molar ratio of chlorophyll a to b and an increase in the fluorescence emission ratio of light-harvesting complex II to photosystem II, the latter evaluated by in vivo single-cell microspectrofluorimetry. These changes were observed between 24 and 72h of treatment. However, the alterations in the pigment pattern and photosystem II fluorescence were no longer observed after 96h of Mn exposure, notwithstanding the maintenance of the large plastid mass. The response of the photosynthetic apparatus probably allows the alga to limit the photooxidative damage linked to the inappropriately large peripheral antennae of photosystem II. On the whole, the resistance of Euglena gracilis to Mn may be due to an exclusion–tolerance mechanism since most Mn is excluded from the cell, and the small amount entering the organism is tolerated by means of morphophysiological adaptation strategies, mainly acting at the plastid level.Correspondence and reprints: Dipartimento delle Risorse Naturali e Culturali, Università degli Studi di Ferrara, Corso Porta Mare 2, 44100 Ferrara, Italy.     

Climbing and the daily energy cost of locomotion in wild chimpanzees: implications for hominoid locomotor evolution

As noted by previous researchers, the chimpanzee postcranial anatomy reflects a compromise between the competing demands of arboreal and terrestrial locomotion. In this study, we measured the distance climbed and walked per day in a population of wild chimpanzees and used published equations to calculate the relative daily energy costs. Results were used to test hypotheses regarding the arboreal-terrestrial tradeoff in chimpanzee anatomy, specifically whether arboreal adaptations serve to minimize daily locomotor energy costs by decreasing the energy spent climbing. Our results show that chimpanzees spend approximately ten-times more energy per day on terrestrial travel than on vertical climbing, a figure inconsistent with minimizing energy costs in our model. This suggests non-energetic factors, such as avoiding falls from the canopy, may be the primary forces maintaining energetically costly climbing adaptations. These analyses are relevant to anatomical comparisons with living and extinct hominoids.     

Oreopithecus bambolii: an unlikely case of hominid-like grip capability in a Miocene ape

Oreopithecus bambolii, an ape from the late Miocene of Italy, is said to possess a hand capable of a precision grip like that of humans. Relative hand length, proportions of the thumb, and morphological features of the thumb and wrist were adduced to support the idea that Oreopithecus had a hand that closely matched the pattern in Australopithecus. A reappraisal of earlier arguments and comparisons of Oreopithecus with humans, apes, and Old World monkeys, reveals that Oreopithecus had an essentially ape-like hand that emphasized ape-like power grasping over human-like precision grasping.