Phylogeography of Xiphorhynchus fuscus (Passeriformes, Dendrocolaptidae): vicariance and recent demographic expansion in southern Atlantic forest

Knowledge of the evolutionary processes that shaped a biota is important for both academic and conservation purposes. The objective of the present study is to analyse the mitochondrial genetic variation of Xiphorhynchus fuscus (Aves: Dendrocolaptidae) from the southern Atlantic forest in Brazil and Argentina, and to discuss whether the results support different hypotheses regarding the local intraspecific diversification of this species . We sequenced 575 bp of the control region of 114 specimens collected in the Brazilian states of Bahia, Minas Gerais, Rio de Janeiro, São Paulo, Paraná, and Santa Catarina, and in the province of Misiones in Argentina. We studied the population genetic structure with analysis of molecular variance and the demographic history with multiple regression analysis, coalescence simulations, and demographic tests. Xiphorhynchus fuscus presented a significant population genetic structure (Φ_st = 0.57). Three mitochondrial lineages were described, one associated with Xiphorhynchus fuscus tenuirostris and the others with Xiphorhynchus fuscus fuscus. The data did not support the primary influence of geographical barriers or rivers in the intraspecific diversification of X. fuscus in the southern Atlantic forest. Instead, the data supported the influence of isolation by geographical distance, recent vicariance events, and demographic expansions apparently related to Pleistocene and Holocene forest dynamics.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 73–84.     

The chemical strategies used by Polistes nimphus social wasp usurpers (Hymenoptera Vespidae)

Polistes foundresses can behave as facultative social parasites when, instead of founding their own nest, they usurp colonies of the same or a different species and temporary use the host workforce to raise their own brood. Conspecific usurpation appears to be common among Polistes wasps, but nothing is known about the mechanisms that these facultative social parasites use to have themselves accepted within usurped colonies. Using behavioural tests, we studied the chemical strategies employed by females of Polistes nimphus when they behave as facultative social parasites in colonies of the same or of a different species. We hypothesized that usurpers would mark host nests with their own odours and/or acquire host nest odours in order to camouflage their real identity from host workers. Our results indicated that P. nimphus usurpers used different chemical strategies depending on host nest species: they acquired conspecific host odours but marked heterospecific host combs with their own odours.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 505–512.     

Effects of solar radiation on the endemic Mediterranean red alga Rissoella verruculosa: photosynthetic performance, pigment content and the activities of enzymes related to nutrient uptake

The effects of full-spectrum solar radiation and of solar radiation deprived of total u.v. radiation (λ<395 nm) on the endemic Mediterranean red alga Rissoella verruculosa (Bertoloni) J. Agardh were studied in situ in early summer, from sunrise to sunset. Photosynthetic performance, pigment content and the activities of enzymes related to nutrient uptake, were monitored under both radiation conditions throughout a daylight period.
The doses of solar radiation, measured on the day during which the experiments were carried out (24 June 1997), were 9228·25, 1109·70 and 13·03 kJ m⁻² for PAR (λ=400–700 nm), u.v.-A (λ=315–400 nm) and u.v.-B (λ=280–315 nm), respectively. Under these conditions, a clear daily variation in photosynthetic performance was found. However, no significant differences were detected between the two radiation conditions. At noon, strong sunlight impaired O₂ evolution by 75%, but complete recovery occurred during the afternoon, reaching similar values to those measured in the early morning. By contrast, photoinhibition of optimal quantum yield ( F _v/ F _m), and the relative electron transport rate was followed by only a slight recovery during the afternoon. The rate of photosynthesis in air (simulating emersion conditions), estimated by CO₂ exchange, showed a negative balance at noon, which was accentuated in plants exposed to the full-solar spectrum.
Significant changes in the activities of nitrate reductase and carbonic anhydrase were found throughout the day under both radiation conditions. In thalli receiving solar radiation deprived of u.v., total CA activity decreased throughout the day. However, in thalli exposed to full-spectrum solar radiation, the activity of the enzyme tended to increase in the afternoon, correlating with an increase in NR activity.     

Differential visual predation on morphs of Timema cristinae (Phasmatodeae:Timemidae) and its consequences for host range

Timema cristinae is a herbivorous insect that exhibits polymorphism for body coloration (green, red and grey morphs) and for pattern (striped, expressed only in the green morph, and unstriped). The striped green morph is associated with ceanothus ( Ceanothus spinosus ) and the unstriped green morph is associated with chamise ( Adenostoma fasciculatum ). This study examines the relative vulnerabilities to predation of the different pattern and colour morphs on their natural backgrounds. The vulnerabilities of the striped and unstriped morphs on their two food plants were tested using uncaged wild birds (Scrub Jays) and captive western fence lizards. Strong differential predation was observed suggesting that each morph is most cryptic on the food plant on which it is most common. Furthermore, in a mark-recapture experiment in a patch of ceanothus the unstriped and red morphs were recaptured in higher proportion than the other morphs. The vulnerabilities of the grey and green morphs on the ground and foliage were tested using lizards. The grey morph was more vulnerable on the plants than the green morph, but the inverse was observed on the ground (where they drop after a disturbance). This may be why the grey morph is not associated with specific food plants. The striped and colour polymorphisms in T. cristinae appear to be an evolutionary consequence of differential predation on different backgrounds. The implications of differential predation to food-plant utilization are discussed.     

INDIVIDUAL VARIATION IN THE DISTRIBUTION OF LENS POTENCY IN WOLFFIAN LENS REGENERATION

After lentectomy in newts, lens regeneration originates from the iris. The regenerant was externally observed with a stereomicroscope as a depigmented area (DA) of the iris, and the extent of DA up to 15 days after lentectomy was measured. The extent of DA was found to differ among individuals, whereas it was the same in both eyes of each animal. In a number of animals one eye was used for lentectomy. After measuring the DA, two groups of animals were selected; a "W-group" with an extremely wide DA that deviated from the standard value, and "N-group", with an extremely narrow DA. Six iris sectors obtained from the animals of the W-group or N-group were implanted into lentectomized eyes of other animals to investigate the difference in the distribution of lens potency in these two groups. Animals of the W-group possessed a wider distribution of lens potency than animals of the N-group. Pulse-labelling with ³H-thymidine on lentectomized eyes of both groups was done 0, 3, 5, 7 and 12 days after lentectomy. DNA-synthesis began earlier and continued longer in the dorsal part of the iris of the W-group than in that of the N-group. The distribution of lens potency in the iris is discussed on the basis of these findings.     

Self or Non--self Recognition in Compound Ascidians

SYNOPSIS. Certain species of compound ascidians have an abilityto distinguish self colonies from non—self colonies withinthe same species. This ability, called colony specificity, ismanifested by the fusibility between colonies. The fusibilityamong colonies of Japanese Botryllus is genetically controlledby a series of multiple alleles at a single locus. The fusibilityis determined by a factor(s) in blood, so that the fusibilitycan be altered by the exchange of blood. It is suggested thatrejection, called "nonfusion" reaction, may occur from the interactionbetween blood cells and blood humoral factor(s).