Lack of allozyme variation in the Spanish Imperial Eagle Aquila adalberti

The breeding population of the Spanish Imperial Eagle Aquila adalberti is reduced to 126 pairs located in the southwestern quadrant of the Iberian Peninsula. Protein electrophoresis was used to determine levels of genetic variation in the seven extant subpopulations of the species. Seventeen proteins encoded by 22 putative loci showed no variation among all the individuals which were analysed. The population crashed at the beginning of this century, but the long generation time of the species makes it improbable that a population bottleneck was the only cause of the lack of genetic variation. As an alternative explanation, a natural background of low variation cannot be discounted.     

Identification of Precystic Stages and Encystment Kinetics Analysis of Colpoda inflata by Using an Immunofluorescent Method

ABSTRACT. The application of an immunocytochemical method to identify precystic stages and to analyse the encystment kinetics, by using a polyclonal antiserum against isolated cyst walls from the ciliate Colpoda inflata , is reported for the first time. Three different precystic phases were chosen on the basis of morphological changes and degree of cyst wall formation. By using this procedure a better identification of mature resting cysts with regard to precystic cells or young cysts is provided. An average consensus encystment kinetics of C. inflata , by using an accumulated class frequency analysis, is reported.     

Does daylength explain the latitudinal variation in clutch size of Pied Flycatchers Ficedula hypoleuca?

Geographical trends in breeding parameters were studied in the Pied Flycatcher Ficedula hypoleuca in the western Palaearctic. Predictions arising from the hypothesis that daylength and/or energy requirements of the brood explain latitudinal clutch size variation were tested. The nestling period decreased with latitude, but nestling mass on day 13 after hatching did not show a trend with latitude. The length of the daily activity period (working day) at the time of peak brood demand showed a quadratic relationship with latitude and did not increase linearly with daylight hours. The present study supports the hypothesis that latitudinal clutch size variation is influenced by the duration of the working day and the energy requirements of the brood. The balance between the energy requirements of the brood and the parents, in relation to the duration of working day and ambient temperature, are proposed to explain the latitudinal variation in clutch size in the Pied Flycatcher.     

Four new species of Typhlocharis (baetica group) (Coleoptera: Carabidae: Anillini) from southwestern Iberian Peninsula with notes on their biogeographical and morphological implications

Four new species of Typhlocharis (Carabidae: Anillini) are described from the southwest of the Iberian Peninsula, assigned to the baetica species group. T. prima sp.n. , T. secunda sp.n. and T. tertia sp.n. (from La Palma del Condado, Huelva, Spain) are syntopic, and T. quarta sp.n. (from Barrancos, Beja, Portugal) is the first species of the group with umbilicate series 4 + 4. They represent, respectively, the southernmost and westernmost distribution data for the group. The baetica group remains well defined and includes ten species. The diagnosis is simplified, with the confirmation that many morphological features characteristic of this group are widespread within the genus. The defining character is the presence of denticles in apical margin of elytra, not associated to the seventh stria or to the elytral suture. The new species provide morphological data that suggest the baetica and silvanoides groups are closely related. Distribution of both groups in the south of the Iberian Peninsula and the presence of morphological characters that are considered plesiomorphic are coherent with the hypothesis of betic‐riffain origin of the genus. They also support the hypothesis of easy alteration of the umbilicate pattern between closely related species and the independent origin of apical denticles in the group compared with those present in other species of the genus. The presence of three well‐differentiated size ranges in syntopic populations suggest ecological diversification to avoid interspecific competition.     

Long‐distance abscisic acid signalling under different vertical soil moisture gradients depends on bulk root water potential and average soil water content in the root zone

To determine how root‐to‐shoot abscisic acid (ABA) signalling is regulated by vertical soil moisture gradients, root ABA concentration ([ABA]_root), the fraction of root water uptake from, and root water potential of different parts of the root zone, along with bulk root water potential, were measured to test various predictive models of root xylem ABA concentration [RX‐ABA]_sap. Beans (Phaseolus vulgaris L. cv. Nassau) were grown in soil columns and received different irrigation treatments (top and basal watering, and withholding water for varying lengths of time) to induce different vertical soil moisture gradients. Root water uptake was measured at four positions within the column by continuously recording volumetric soil water content (θ_v). Average θ_v was inversely related to bulk root water potential (Ψ_root). In turn, Ψ_root was correlated with both average [ABA]_root and [RX‐ABA]_sap. Despite large gradients in θ_v, [ABA]_root and root water potential was homogenous within the root zone. Consequently, unlike some split‐root studies, root water uptake fraction from layers with different soil moisture did not influence xylem sap (ABA). This suggests two different patterns of ABA signalling, depending on how soil moisture heterogeneity is distributed within the root zone, which might have implications for implementing water‐saving irrigation techniques.     

A retrospective,dual‐isotope approach reveals individual predispositions to winter‐drought induced tree dieback in the southernmost distribution limit of Scots pine

Winter‐drought induced forest diebacks in the low‐latitude margins of species' distribution ranges can provide new insights into the mechanisms (carbon starvation, hydraulic failure) underlying contrasting tree reactions. We analysed a winter‐drought induced dieback at the Scots pine's southern edge through a dual‐isotope approach (Δ¹³C and δ¹⁸O in tree‐ring cellulose). We hypothesized that a differential long‐term performance, mediated by the interaction between CO₂ and climate, determined the fates of individuals during dieback. Declining trees showed a stronger coupling between climate, growth and intrinsic water‐use efficiency (WUEi) than non‐declining individuals that was noticeable for 25 years prior to dieback. The rising stomatal control of water losses with time in declining trees, indicated by negative Δ¹³C‐δ¹⁸O relationships, was likely associated with their native aptitude to grow more and take up more water (suggested by larger tracheid lumen widths) than non‐declining trees and, therefore, to exhibit a greater cavitation risk. Freeze‐thaw episodes occurring in winter 2001 unveiled such physiological differences by triggering dieback in those trees more vulnerable to hydraulic failure. Thus, WUEi tightly modulated growth responses to long‐term warming in declining trees, indicating that co‐occurring individuals were differentially predisposed to winter‐drought mortality. These different performances were unconnected to the depletion of stored carbohydrates.     

Seasonal decline in provisioning effort and nestling mass of Blue Tits Cyanistes caeruleus: experimental support for the parent quality hypothesis

A common feature of many birds breeding in seasonal environments is that fitness‐related parameters such as nestling mass or survival decline as the breeding season progresses. Consequently, there is a tendency for early breeders to have better reproductive performance than individuals breeding later in the season. This variation could be caused by factors associated with the date of laying, such as changing environmental conditions (date hypothesis), or by differences in parental quality between early and late breeders (parent quality hypothesis). To evaluate the relative importance of both hypotheses, we manipulated hatch dates of Blue Tits Cyanistes caeruleus by exchanging clutches with different incubation stages and assessed the impact on nestling mass, nestling diet and provisioning rates. Mean nestling mass declined significantly over the season. This was the combined result of differences in parental quality, which dominated in the early part of the season, and the influence of hatching date (date effect per se), which prevailed later in the season. Nestling diet composition was apparently uninfluenced by the manipulation, suggesting that deteriorating food supplies are the primary reason for the seasonal variation in the nestling diet. Counter to the date hypothesis, delayed parents did not feed their young less than control pairs did, but in fact exhibited higher provisioning rates. Our results suggest that in this population, parental quality seems to constrain post‐hatching reproductive performance and such intrinsic limitations may help to explain why certain individuals breed later.     

Assortative mating among Anastrepha fraterculus (Diptera: Tephritidae) hybrids as a possible route to radiation of the fraterculus cryptic species complex

Reproductive isolation among populations of Anastrepha fraterculus has been found acting at the pre‐ and post‐zygotic levels. Differences in timing of sexual activity and male sexual pheromone composition among populations could partially account for prezygotic isolation. Hybrid males were found to produce a novel pheromone, which is a mix of parental pheromones. In the present study, we found that the hybrid females showed a significant preference to mate with hybrid males than with parental males. Male location during pheromone emission is associated with its reproductive success and, thus, differences in the location of males during courtship could also play a role in isolation. We found evidence that reproductive isolation is also related to the location of males during courtship. Hybrid male behaviour regarding location during pheromone release was found to be influenced by the maternal lineage. If these populations hybridized in the field, the hybrid females would tend to mate with hybrid males probably leading to the formation of a new entity within the A. fraterculus complex. This simple and fast process could be one reason explaining the high number of taxonomic entities within this complex. Further studies on other members of the fraterculus species group may reveal whether this can be considered as an example of homoploid hybrid speciation. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 346–354.     

New data on the evolution of the Cretan spiny mouse,Acomys minous (Rodentia: Murinae), shed light on the phylogenetic relationships in the cahirinus group

The karyotype of the Cretan spiny mouse Acomys minous was examined with chromosome banding techniques in 53 individuals from 12 localities of Crete, aiming to gain a more detailed knowledge on the chromosomal constitution and variability of its natural populations. We found that it consists of three Robertsonian (Rb) populations with 2n = 38, 2n = 40 and 2n = 42, respectively, the last one being reported for the first time, and with stable fundamental number (FNa = 66, FN = 68). The G‐banding pattern proves that the Rb populations are closely linked phylogenetically by the many common Rb fusions and the lack of monobrachial homologies. In addition, they appear to freely mate at their contact areas, producing viable and fertile hybrids. No other type of chromosomal rearrangement appears to have played part in the chromosomal evolution of this species, at least in the recent past, as indicated also by the study of the telomeric sequences. Heterochromatin appears to be restricted to the pericentromeric position of all acrocentric and most biarmed autosomes, as well as of the X chromosome, whereas the Y chromosome is uniformly, yet faintly heterochromatic. Chromosome banding comparison of the karyotypes in A. minous with those of the other species in the cahirinus group (i.e. Acomys cahirinus, Acomys cilicicus, and Acomys nesiotes) proves their very close phylogenetic relationship, further reinforced by the study of the cytochrome b sequences, and that A. minous possesses the ancestral karyotype of the group. It is suggested that at least two of the karyotypes that characterize A. minous today, pre‐existed in North Africa before it colonized Crete and that the specific status of the four members in the cahirinus group may need to be revisited. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 498–509.     

The Straits of Gibraltar: barrier or bridge to Ibero‐Moroccan bat diversity?

Genetic divergence in bat communities was assessed on both sides of the Straits of Gibraltar and cryptic diversity was examined. Screening was carried out using partial sequences of the mitochondrial (mt)DNA cytochrome b gene on 399 individual bats belonging to the 18 species found on both sides of the Straits of Gibraltar. For those bats that showed important genetic discontinuities, molecular markers (ND1 and nuclear RAG2 genes) were added to expand the sampling process. Phylogenetic reconstructions were obtained using maximum parsinomy, genetic distances, maximum likelihood, and Bayesian criteria. As an estimate of bats' flight performance, we measured for each species the wing aspect ratio and wing loading indexes, and correlated them with the maximum pairwise genetic distances obtained between southern Iberian and northern Moroccan populations. Genetic mtDNA distances between populations on both continents exceed 5% in seven out of 18 bat species analysed and unknown lineages were uncovered within the species complexes Myotis nattereri and Myotis mystacinus . We did not find a general pattern in the degree of permeability of the Straits of Gibraltar for bats. Genetic distances were not correlated with the ability to cross the Straits. Our study shows that the cryptic diversity uncovered among bats continues to increase as more regions are studied.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 434–450.