Phylloclade anatomy in Phyllanthus section Choretropsis (Phyllanthaceae)

The phylloclade anatomy of nine Brazilian species of the genus Phyllanthus section Choretropsis was studied, and its systematic significance was analysed. The arrangement of epidermal cells varied according to the species, with the guard cells of the stomatal apparatus distributed randomly or with the longitudinal axis parallel to the branch. In both branch types, the stomata were distributed on the phylloclade surface, except in P. gladiatus which showed hypostomatic branches. In most of the species, phylloclades developed a vascular system surrounded by clusters of fibres and cortical parenchyma, which could differentiate into palisade‐like tissue and ground tissue like a true leaf blade. The distribution of the vascular system followed the cylindrical or flattened diameter shape of the branch. In subsection Choretropsis, the cylindrical branches of P. choretroides, contrary to other species, developed a second ring formed by clusters of fibres surrounded by large parenchymal cells. In subsection Applanata, the palisade‐like cells of P. flagelliformis phylloclades acquired an isodiametric shape. The highest level of specialization was observed in P. gladiatus, which developed phylloclades with a dorsiventral structure, a main vein, and small sets of lateral vascular bundles like a typical leaf blade. The tissue arrangement of different species showed a gradual pattern, which was correlated with the different branch morphology and plant architecture. Despite the transitional pattern, it was suggested that some of the phylloclades had an independent origin and convergent evolution in the Choretropsis section. The anatomy of different branch types was shown to be useful, either in isolation or in association with other morphological characters, to delimit the species and to further understand their relationships and phylogeny. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157 , 91–102.     

Growth and development of larval northern cricket frogs (Acris crepitans) in relation to phytoplankton abundance

SUMMARY. 1. Tadpoles of Acris crepitans were collected from two ponds in central Illinois, Depth, water temperature, distance from shore and water samples were taken at each sample site. The potential for food limitation and non-random habitat selection were examined.
2. Algal densities from water samples averaged over 1.0× 10⁶ cells ml⁻¹ in Scott's pond hut only 4.6×10³ cells ml⁻¹ in Vic's pond.
3. Guts of tadpoles from Scott's pond contained more algal cells than did guts of tadpoles from Vic's pond. Tadpoles from Scott's pond were consistently larger and more advanced in development than tadpoles collected from Vic's pond at the same lime. Therefore, tadpoles of Scott's pond were able to utilize the higher algal densities whereas tadpoles of Vic's pond may be food-limited, causing reduced growth and development.
4. Canonical discriminant analysis was used to test whether sites with different numbers of tadpoles could be distinguished based on environmental variables. Canonical function I was primarily a measure of water depth at a sample site. This function was significant in Scott's pond only. Sites containing one or more tadpoles were not easily distinguished from each other, but were found in consistently shallower water than sites where no tadpoles were found.     

Isolation and characterization of the mating type locus of Mycosphaerella fijiensis, the causal agent of black leaf streak disease of banana

Idiomorphs mat1-1 and mat1-2 from Mycosphaerella fijiensis , the causal agent of black leaf streak disease of banana, were isolated. Degenerate oligos were used to amplify the HMG box of the mat1-2 idiomorph from M. fijiensis , showing homology with the HMG box of Mycosphaerella graminicola. Using a DNA walking strategy, anchored on the DNA lyase gene towards the HMG box, a 9-kb-long region of mat1-2 was obtained. A 5-kb fragment from the mat1-1 region was obtained by long-range PCR using primers on the flanking regions, which have close to 100% identity between both idiomorphs. High-identity (77–89%), inverted regions within both idiomorphs were found, which suggest unique inversion events, which have not been found before, and that could have been significant in the evolution of this species. The predicted genes showed the conserved introns in both idiomorphs as well as an additional intron within the alpha box. The implications for the evolution of species in the Mycosphaerella complex on banana are discussed.     

A NEW SPECIES OF THE SPHENODONTIAN REPTILE CLEVOSAURUS FROM THE LOWER JURASSIC OF SOUTH WALES

Abstract:  Small reptiles from the Early Jurassic Pant 4 fissure fill in Glamorgan, South Wales (St. Bride's Island, Pant Quarry), were formerly provisionally attributed to three species of sphenodontian lepidosaurs. A re-analysis, aided by new material, has found this herpeto-fauna to consist almost exclusively of a single new species, Clevosaurus convallis sp. nov . , with only one specimen referable to Sphenodontia incertae sedis . Clevosaurus is known from the Upper Triassic and Lower Jurassic in various parts of the world, but C. convallis represents the first occurrence of the genus in the Jurassic of Britain. The material is fragmentary but includes numerous premaxillae, maxillae, dentaries and palatines, and the new species is distinguished by the unique combination of six large additional dentary teeth and a very short nasal process of the premaxilla, along with the diagnostic Clevosaurus features.     

Competition between the native and the introduced hornets Vespa crabro and Vespa velutina: a comparison of potentially relevant life‐history traits

1. Invasive alien species are a major threat to biodiversity. In addition to predation and parasitism, native species might suffer from competition when invasive alien species occupy a similar ecological niche. 2. This study focused on the potential interspecific interaction between two hornets: the Asian yellow‐legged hornet, Vespa velutina, a high‐concern invasive alien species recently arrived in Europe; and the native European hornet, Vespa crabro. The two species share a similar ecological niche and V. velutina is rapidly expanding across Europe, which suggests that V. crabro might suffer from competition. 3. Under laboratory‐controlled conditions, two life‐history traits that might cause the two species to compete were investigated: (i) the ability of workers to find food sources and their flexibility in exploiting them (through individual food item choice tests and exploration assays); and (ii) the worker resistance to pathogens (through immune challenge tests). 4. The results show that trophic preference of both species highly overlaps, with a marked dietary preference for honeybees compared with other insect prey and non‐prey protein items. No differences were observed in the exploratory behaviour of both species. Finally, constitutive antibacterial activity was greater in workers of the native species than in workers of the invasive hornet. 5. This laboratory study provides a first assessment under controlled conditions of the factors affecting competition between workers of two hornet species and proposes a framework to assess, in wild contexts, the magnitude of the competition and the impact of the introduced V. velutina on the native V. crabro.     

Song mimicry and species associations of west African indigobirds Vidua with Quail-finch Ortygospiza atricollis, Goldbreast Amandava subflava and Brown Twinspot Clytospiza monteiri

The brood-parasitic indigobirds Vidua spp. mimic the songs of their foster species, which for many species of indigobirds are Lagonosticta firefinches. We report additional associations of indigobirds with estrildid finches in west Africa. Quail-finch Indigobirds Vidua nigeriae in northern Cameroon mimic the songs of Quail-finch Ortygospiza atricollis . Gold-breast Indigobirds Vidua raricola in Cameroon and Sierra Leone mimic the songs of Gold-breast Amandava subflava . Both indigobirds are distinct in male breeding plumage from other indigobirds. Also, a population of blue indigobirds Vidua sp. in Cameroon mimics the songs of Brown Twinspot Clytospiza monteiri . They are similar in colour and size to blue indigobirds associated with Dark Firefinch L. rubricata and Black-bellied Firefinch L. rara . Mouth patterns of fledged young Quail-finch Indigobirds and Goldbreast Indigobirds resemble those of their song-model and presumed foster species, but the mouth pattern of a fledged young associated with the Brown Twinspot mimic was not distinct from the mouth of young Black-bellied Firefinch. The field observations show associations of certain species of indigobirds with finches other than the firefinches. The results are consistent with mitochondrial DNA estimates of greater genetic similarity among indigobirds than among their foster species. The field observations support the hypothesis of evolutionary associations of the brood parasite and foster species by colonization with switching from one foster to another rather than by cospeciation.     

Raccoon Density and Movements After Population Reduction to Control Rabies

ABSTRACT Population reduction (PR) and trap-vaccinate-release (TVR) were used to control an outbreak of the raccoon (Procyon lotor) variant of rabies in Ontario, Canada, during 1999. Raccoon density declined significantly following PR; however, density increased significantly 9–10 months post-PR. Recolonization of PR areas with raccoons marked in TVR areas was very low with only 1.8% (32/1,759) of those raccoons dispersing into PR areas during 1999–2000. In addition, the number of raccoons dispersing from TVR areas into PR areas was not significantly greater than the number of raccoons dispersing into treatment areas where population reduction had not been implemented during 1999–2000. Raccoon movements in this study, determined by mark-recapture, averaged < 4.0 km during 1999–2000 and did not differ among treatments (with or without PR). In summary, there was not a mass exodus of raccoons from TVR areas to PR areas during 1999–2000, suggesting there was not an immediate, dramatic, vacuum effect drawing raccoons into areas devoid of raccoons due to PR. However, one year post-PR, raccoon populations were near or above pre-PR densities (due to a high reproductive rate of resident raccoons), suggesting that PR would have to be an annual event if rabies is not eliminated from an area.     

Nuclear Structure and Mitosis in the Dinoflagellate Gonyaulax monilata*

SYNOPSIS. Nuclear structure and mitosis in Gonyaulax monilata were studied. Between the arms of the U-shaped interphase nucleus is a band of material which, it is suggested, is homologous with the “central body” of G. tamarensis. Histochemical studies of whole cells, extruded nuclei and Epon-embedded sections indicate that the band is composed at least in part of protein, phospholipid and possibly RNA. The chromosomes of interphase nuclei are attached to the ends of the band. The band is also attached to a proteinaceous, extra-chromosomal matrix which pervades the nucleus. Studies on material treated with trypsin indicate that the matrix may be a factor in maintaining chromosomal integrity and orientation and nuclear form. During mitosis the band acts as a point of attachment for the chromosomes, and appears to control anaphase and telophase movements. It is suggested that the band is a component of the mitotic apparatus in G. monilata.     

Nectar dispersion patterns in three Australian plant species

Standing crops of floral nectar were measured from three species of plants: Dampiera stricta, Goodenia bellidifolia and Aotus ericoides. The amount of nectar in nearest neighbour blossoms in nine of the 10 samples were significantly correlated with one another suggesting that patches of high and low reward quality exist in these species. The patterns further suggest that the pollinators of these species employ arearestricted searching behaviour. The range of variability in standing crops for all three species was quite high. The nature of that variability suggests that A. ericoides is less variable in its rate of nectar production than are the other two species and, therefore, that it has the potential to be more tightly co-evolved with its pollinators.