Distribution of Lilian's Lovebirds in Malawi

Lilian's Lovebird Agapornis lilianae is regarded as a mopane Colophospermum mopane woodland specialist. Its global population is sparse and is spread along the Zambezi valley with little known about its current distribution and status. We explored the current distribution of Lilian's Lovebird in Malawi, and in particular focused on the distribution and habitat associations of the largest resident population in Liwonde National Park (LNP). Local birders and tourist guides provided distribution information from across Malawi. Transect walks were conducted to collect data in LNP. Five new atlas records are reported; three were within 40–56 km of the LNP population and two were over 150 km south and north of LNP, respectively. One of the sites is about 66 km from the Lilian's Lovebird population in Luangwa Valley, Zambia. New national records were evidence of the importance of seasonal movements to the species. Lilian's Lovebirds occurred throughout LNP with the highest abundance in the central section. Seasonal movements to areas outside the park were also recorded. A variety of vegetation types were used by the lovebirds, but the strongest habitat associations were with seasonally wet grasslands and not mopane woodlands as would be expected. Thus, conservation efforts should also include these other habitats.     

Investigating the molecular determinants for substrate channeling in BphI-BphJ, an aldolase-dehydrogenase complex from the polychlorinated biphenyls degradation pathway

BphI-BphJ, an aldolase-dehydrogenase complex from the polychlorinated biphenyls (PCBs) degradation pathway, cleaves 4-hydroxy-2-oxoacids to pyruvate and an aldehyde. The enzyme complex was shown to exhibit substrate channeling, whereby linear aldehydes of up to 6 carbons long and branched isobutyraldehyde were directly channeled from the aldolase to the dehydrogenase with greater than 80% efficiency. BphI variants G322F, G322L, and G323F were created and were found to block aldehyde channeling. The dehydrogenase cofactor NADH was able to activate the catalytic activity of the aldol cleavage reaction in these variants, suggesting that activation of BphI by BphJ cofactors is not solely due to faster aldehyde release. A G323L variant was able to channel acetaldehyde but not the larger propionaldehyde while the G323A variant was able to channel butyraldehyde but not its isomer isobutyraldehyde, confirming that the restricted channeling of aldehydes in these glycine variants are due to steric blockage of the channel. Substitution of His-20 and Tyr-290 in BphI led to significant reductions in aldehyde channeling efficiencies. A mechanism of substrate channeling involving these two gating residues is proposed.     

TEMPERATURE‐DEPENDENT TURNOVERS IN SEX‐DETERMINATION MECHANISMS: A QUANTITATIVE MODEL

Sex determination is often seen as a dichotomous process: individual sex is assumed to be determined either by genetic (genotypic sex determination, GSD) or by environmental factors (environmental sex determination, ESD), most often temperature (temperature sex determination, TSD). We endorse an alternative view, which sees GSD and TSD as the ends of a continuum. Both effects interact a priori, because temperature can affect gene expression at any step along the sex‐determination cascade. We propose to define sex‐determination systems at the population‐ (rather than individual) level, via the proportion of variance in phenotypic sex stemming from genetic versus environmental factors, and we formalize this concept in a quantitative‐genetics framework. Sex is seen as a threshold trait underlain by a liability factor, and reaction norms allow modeling interactions between genotypic and temperature effects (seen as the necessary consequences of thermodynamic constraints on the underlying physiological processes). As this formalization shows, temperature changes (due to e.g., climatic changes or range expansions) are expected to provoke turnovers in sex‐ determination mechanisms, by inducing large‐scale sex reversal and thereby sex‐ratio selection for alternative sex‐determining genes. The frequency of turnovers and prevalence of homomorphic sex chromosomes in cold‐blooded vertebrates might thus directly relate to the temperature dependence in sex‐determination mechanisms.     

Expression of LSLCL, a new C-type lectin, is closely restricted, in bone marrow, to immature neutrophils.

In vitro, LSLCL is expressed by numerous myeloid, promyelocytic, and T or B lymphoblastoid cell lines. In vivo, LSLCL is strongly expressed in bone marrow and only faintly in lymphoid organs. We show here that, in bone marrow, LSLCL is detected: (i) concentrated in the cytoplasm of immature neutrophils but not in myeloblasts nor in mature neutrophils, (ii) in extracellular bone marrow fluid. Besides, numerous cDNAs, similar to LSLCL (identity of 93-99%), are found in 'expressed sequence tags' databases from various origins, mostly fetal and undifferentiated tumour tissues. Since LSLCL and various closely related cDNAs are expressed at definite stages of cellular maturation processes, we hypothesize that this class of proteins could play an important role in the control of cellular differentiation.     

Multiple origins of invasive and ‘native’ water frogs (Pelophylax spp.) in Switzerland

The marsh frog (Pelophylax ridibundus) has been introduced in many areas in Central and Western Europe as a result of commercial trade with Eastern Europe, and is rapidly replacing the native pool frog (P. lessonae). A large number of Pelophylax species are distributed in Eastern Europe and the strong phenotypic similarity between these species is rendering their identification hazardous. Consequently, alien populations of Pelophylax might not strictly be composed of P. ridibundus as previously suspected. In the present study, we analysed the cytochrome‐b and NADH dehydrogenase subunit 3 genes of introduced and native Pelophylax species from Switzerland (299 individuals) in order to properly identify the source populations of the invaders and the genetic status of the native species. Our study highlighted the occurrence of several genetic lineages of invasive frogs in western Switzerland. Unexpectedly, we also showed that several populations of the native pool frog (P. lessonae) cluster with the Italian pool frog P. bergeri from central Italy (considered by some authors as a subspecies of P. lessonae). Hence, these populations are probably also the result of introductions, meaning that the number of native P. lessonae populations is fewer than expected in Switzerland. These findings have important implications concerning the conservation of the endemic pool frog populations, as the presence of multiple alien species could strongly affect their long‐term subsistence. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 442–449.     

Directional fixation of mutations in vertebrate evolution

Summary We have made pairwise comparisons between the coding sequences of 21 genes from coldblooded vertebrates and 41 homologous sequences from warm-blooded vertebrates. In the case of 12 genes, GC levels were higher, especially in third codon positions, in warm-blooded vertebrates compared to cold-blooded vertebrates. Six genes showed no remarkable difference in GC level and three showed a lower level. In the first case, higher GC levels appear to be due to a directional fixation of mutations, presumably under the influence of body temperature (see Bernardi and Bernardi 1986b). These GC-richer genes of warm-blooded vertebrates were located, in all cases studied, in isochores higher in GC than those comprising the homologous genes of cold-blooded vertebrates. In the third case, increases appear to be due to a limited formation of GC-rich isochores which took place in some cold-blooded vertebrates after the divergence of warm-blooded vertebrates. The directional changes in the GC content of coding sequences and the evolutionary conservation of both increased and unchanged GC levels are in keeping with the existence of compositional constraints on the genome.     

Feeding ecology of Lilian’s Lovebird Agapornis lilianae in Liwonde National Park,Malawi

Lilian's Lovebird Agapornis lilianae is a small, near-threatened parrot resident in mopane Colophospermum mopane woodlands. We investigated its diet and foraging behaviour in Liwonde National Park, Malawi. We expected that Lilian's Lovebirds would show little specialisation for a particular food source but generally feed on available seeds, fruits, flowers and other items as observed in other lovebirds. Lilian's Lovebirds fed on 30 different plant species. Lilian's Lovebirds were observed feeding in six habitat types in Liwonde National Park and adjacent areas during the wet season, and four in the dry season. In the wet season lovebirds (23% of observations) foraged in grassy wetland (dambo) areas the most, whilst in the dry season they foraged in grasslands with tree cover (18%) the most. In mopane woodland, foraging flock sizes differed significantly between the wet (mean = 19.8 ± 1.0 lovebirds) and dry season (mean = 33.6 ± 2.3 lovebirds). Grass seeds were lovebirds’ main food source from December to June. The nutritional analysis of preferred foods showed that grass seeds have a relatively high protein and energy content. Grass seed availability is reduced with savanna burning and so early season burning (before May–June) in areas in and outside the park is not recommended.     

Dominance in a ground‐dwelling ant community of banana agroecosystem

In tropical ecosystems, ants represent a substantial portion of the animal biomass and contribute to various ecosystem services, including pest regulation and pollination. Dominant ant species are known to determine the structure of ant communities by interfering in the foraging of other ant species. Using bait and pitfall trapping experiments, we performed a pattern analysis at a fine spatial scale of an ant community in a very simplified and homogeneous agroecosystem, that is, a single‐crop banana field in Martinique (French West Indies). We found that the community structure was driven by three dominant species (Solenopsis geminata, Nylanderia guatemalensis, and Monomorium ebeninum) and two subdominant species (Pheidole fallax and Brachymyrmex patagonicus). Our results showed that dominant and subdominant species generally maintained numerical dominance at baits across time, although S. geminata, M. ebeninum, and B. patagonicus displayed better abilities to maintain dominance than P. fallax and N. guatemalensis. Almost all interspecific correlations between species abundances, except those between B. patagonicus and N. guatemalensis, were symmetrically negative, suggesting that interference competition prevails in this ground‐dwelling ant community. However, we observed variations in the diurnal and nocturnal foraging activity and in the daily occurrence at baits, which may mitigate the effect of interference competition through the induction of spatial and temporal niche partitioning. This may explain the coexistence of dominant, subdominant, and subordinate species in this very simplified agroecosystem, limited in habitat structure and diversity.