Preferences and predispositions of female canaries (Serinus canaria) for loud intensity of male sexy phrases

In the present study, we tested the effect of song amplitude on intersexual relationships. To evaluate preferences and predispositions of female canaries for amplitude levels of male song, we conducted two experiments using both females raised in acoustic isolation and females raised in an aviary under 'normal' acoustic conditions. The songs used in both experiments followed the same pattern: one reactive phrase surrounded by two nonreactive phrases. The first experiment consisted of testing female preferences for weak, normal, or loud amplitudes of the reactive phrase (i.e. these reactive phrases provoke sexual stimulation in females). In a second experiment, we tested female preferences for weak, normal, or loud amplitudes of the nonreactive phrases. These two experiments allowed us to evaluate female preferences for intensity levels of reactive and nonreactive phrases. In the first experiment, all females significantly prefered loud and normal reactive phrases, whereas the second experiment showed that loud nonreactive phrases do not necessarily provoke more responses than other nonreactive phrases. Female canaries were, thus, more stimulated by the intensity level of a particular part of the song. Both females raised in acoustic isolation and in normal acoustic conditions responded in the same way. We can therefore suppose that learning, through acoustic experience, has little influence on preference development for amplitude levels.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 808–814.     

Leaf physiological responses to extreme droughts in Mediterranean Quercus ilex forest

Global climate change is expected to result in more frequent and intense droughts in the Mediterranean region. To understand forest response to severe drought, we used a mobile rainfall shelter to examine the impact of spring and autumn rainfall exclusion on stomatal (S_L) and non‐stomatal (NS_L) limitations of photosynthesis in a Quercus ilex ecosystem. Spring rainfall exclusion, carried out during increasing atmospheric demand and leaf development, had a larger impact on photosynthesis than autumn exclusion, conducted at a time of mature foliage and decreasing vapour pressure deficit. The relative importance of NS_L increased with drought intensity. S_L and NS_L were equal once total limitation (T_L) reached 60%, but NS_L greatly exceeded S_L during severe drought, with 76% NS_L partitioned equally between mesophyll conductance (MC_L) and biochemical (B_L) limitations when T_L reached 100%. Rainfall exclusion altered the relationship between leaf water potential and photosynthesis. In response to severe mid‐summer drought stress, A_n and V_cmax were 75% and 72% lower in the spring exclusion plot than in the control plot at the same pre‐dawn leaf water potential. Our results revealed changes in the relationship between photosynthetic parameters and water stress that are not currently included in drought parameterizations for modelling applications.     

Queen execution in the Argentine ant, Iridomyrmex humilis

ABSTRACT. Field censuses and laboratory experiments show that in the Argentine ant, Iridomyrmex humilis (Mayr), c. 90% of the queens are executed by workers in May, at the beginning of the reproductive season. The reduction in the number of queens probably decreases the inhibition exerted by queens on the differentiation of sexuals and thus allows the production of new queens and males shortly thereafter. In the laboratory, there was no correlation between the percentage of queens executed and their weight or fecundity. At the time of execution of queens, nearly all queens were of the same age; less than 1 year. Therefore it is not likely that the age of queens plays any role in the choice that workers make in the queens they executed. Execution of these queens results in a heavy energetic cost for the colony which amounts c. 8% of the total biomass. This behaviour of workers executing nestmate queens is discussed with regard to possible evolutionary significance at the queen and worker level.     

Phylogeography of spiny mice (genus Acomys, Rodentia: Muridae) from the south-western margin of the Sahara with taxonomic implications

The present study aims to depict the overall pattern of Acomys history in south-western Sahara. We tested the specific predictions that: (1) several mitochondrial clades can be identified and that they coincide with the described species; (2) successive phases of desert expansion and contraction during the last 3 Myr have resulted in several phases of demographic expansion and population fragmentation in Acomys ; and (3) isolation-by-distance occurs. The extent of phylogeographic patterns and molecular genetic diversity (cytochrome b gene and D-loop) were addressed in a survey of 90 individuals of Acomys from 38 localities. Our phylogeographical analyses show a strong genetic structure within western Saharan Acomys , with several phylogroups displaying non-overlapping geographic distributions. Restricted gene flow with isolation-by-distance was recorded and a signal of population expansion was detected within several clades. We suggest that during arid or semi-arid paleoclimatic periods, when large sandy areas were present, Acomys was restricted to rocky massifs, whereas, in more humid periods, when savannah and/or steppe habitat prevailed, this species was able to disperse and to survive outside rocky areas because food resources were abundant. Based on a comprehensive sampling and the use of an integrative approach (i.e. combining cytogenetic, molecular and morphological data), we firmly propose that Acomys airensis should be considered as a junior synonym of Acomys chudeaui .  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 29–46.     

Transmission of Surface Pattern Through a Dedifferentiated Stage in the Ciliate Paraurostyla. Evidence from the Analysis of Microtubule and Basal Body Deployment

ABSTRACT. During conjugation of the hypotrich ciliate Paraurostyla weissei , the two partners fuse to form a transient dedifferentiated stage, the zygocyst, which later redifferentiates into a vegetative cell. Immunocytochemical studies have been performed to follow the deployment of microtubules and basal bodies during the entire cycle of conjugation. They show that a superficial lattice persists during the whole zygocyst stage, after most of the infraciliature of the exconjugants has been disassembled. These superficial microtubules display different immunocytochemical properties in the mature zygocyst and during its morphogenesis, suggesting that some transient chemical modifications of the microtubules are associated with the morphogenetic activity. In the zygocyst, the superficial microtubules retain the specific orientation characteristic of the ventral and the dorsal sides of the recipient cell, respectively. In the course of subsequent morphogenesis of the zygocyst, these specific cellular territories differentiate into the ventral and dorsal sides of the new cell. Although our experiments do not resolve the question of whether superficial microtubules play an active or merely a passive role in the transmission of surface pattern, they show that no complete breakdown in cell polarity occurs, even through a profound dedifferentiated stage. Thus, the overall surface pattern appears to be retained, in a simplified form, through the conjugation cycle.