Negative fire feedback in a transitional forest of southeastern Amazonia

Anthropogenic understory fires affect large areas of tropical forest, particularly during severe droughts. Yet, the mechanisms that control tropical forests' susceptibility to fire remain ambiguous. We tested the widely accepted hypothesis that Amazon forest fires increase susceptibility to further burning by conducting a 150 ha fire experiment in a closed-canopy forest near the southeastern Amazon forest–savanna boundary. Forest flammability and its possible determinants were measured in adjacent 50 ha forest plots that were burned annually for 3 consecutive years (B3), once (B1), and not at all (B0). Contrary to expectation, an annual burning regime led to a decline in forest flammability during the third burn. Microclimate conditions were more favorable compared with the first burn (i.e. vapor pressure deficit increased and litter moisture decreased), yet flame heights declined and burned area halved. A slight decline in fine fuels after the second burn appears to have limited fire spread and intensity. Supporting this conclusion, fire spread rates doubled and burned area increased fivefold in B3 subplots that received fine fuel additions. Slow replacement of surface fine fuels in this forest may be explained by (i) low leaf litter production (4.3 Mg ha⁻¹ yr⁻¹), half that of other Amazon forests; and (ii) low fire-induced tree and liana mortality (5.5±0.5% yr⁻¹, SE, in B3), the lowest measured in closed-canopy Amazonian forests. In this transitional forest, where severe seasonal drought removed moisture constraints on fire propagation, a lack of fine fuels inhibited the intensity and spread of recurrent fire in a negative feedback. This reduction in flammability, however, may be short-lived if delayed tree mortality or treefall increases surface fuels in future years. This study highlights that understanding fuel input rate and timing relative to fire frequency is fundamental to predicting transitional forest flammability – which has important implications for carbon emissions and potential replacement by scrub vegetation.     

The histological structure of the calcified lung of the fossil coelacanth Axelrodichthys araripensis (Actinistia: Mawsoniidae)

Abstract: The palaeohistological study of the calcified internal organ of Axelrodichthys araripensis Maisey, 1986, a coelacanthiform from the Lower Cretaceous of Brazil (Crato (Aptian) and Santana (Albian) formations of the Araripe Basin), shows that the walls of this organ consist of osseous blades of variable thickness separated from each other by the matrix. This indicates that, in the living individuals, the walls were reinforced by ossified plates, probably separated by conjunctive tissue. This calcified sheath present in Axelrodichthys, as well as in other fossil coelacanths, lies in ventral position relative to the gut and its single anterior opening is located under the opercle, suggesting a direct connection with the pharynx or the oesophagus. The calcified organ of Axelrodichthys, like that of other fossil coelacanths, is here regarded as an ‘ossified lung’ and compared with the ‘fatty lung’ of the extant coelacanth Latimeria. The reinforcement of the pulmonary walls by the overlying osseous blades could be interpreted as a means of adapting volumetric changes in the manner of bellows, a necessary function for ventilation in pulmonary respiration. Other functional hypotheses such as hydrostatic and/or acoustic functions are also discussed.     

Laser‐assisted microdissection of polytene chromosomes from Diptera for the development of molecular markers

The structural details visible under the light microscope have made polytene chromosomes from Diptera much used in studies of the taxonomy, evolution and genetics of important biological models such as Drosophila and Chironomus, and the medical entomology of important disease vectors such as blackflies and mosquitoes. This paper describes the isolation of sections of polytene chromosomes from preserved wild‐caught blackflies using off‐the‐shelf laser microdissection microscopy and subsequent analysis of the DNA using polymerase chain reaction. This allows a direct link between the visible structure of the genome and the unknown DNA sequence, facilitating the development of molecular markers for population cytogenetics and cytotaxonomy.     

Phylogeny of the World Anthophorini (Hymenoptera: Apoidea: Apidae)

Abstract.  The phylogenetic relationships of members of the long-tongued bee tribe Anthophorini were investigated. Twenty-six ingroup taxa, representing all known genera and the most common subgenera of the Anthophorini, were included in a cladistic analysis of the tribe based on 51 morphological characters. The analysis yielded the generic relationships: (( Habrophorula , Elaphropoda ) ( Habropoda ( Deltoptila ( Pachymelus ( Amegilla , Anthophora ))))). The monophyly of the Anthophorini and each of its genera was confirmed. A second tribe, Habropodini, as postulated by some authors, is paraphyletic. On the basis of the results of the cladistic analysis and the biogeographical data of Anthophorini, an evolutionary scenario is postulated in which all genera of Anthophorini probably evolved in the Late Cretaceous, except Amegilla and Anthophora , which originated in the Oligocene. The northern part of south-east Asia (India to south-east China) is regarded as the most probable place of origin and radiation of the Anthophorini. The New World was probably colonized three times independently by Habropoda (upper Cretaceous to Tertiary), by an ancestral lineage of Deltoptila (upper Cretaceous to Tertiary) and by Anthophora (Tertiary to Quaternary).     

Temporal variation of flower scent in Silene otites (Caryophyllaceae): a species with a mixed pollination system

Floral scent composition and emission are often related to olfactory abilities, preferences and activity times of pollinating agents. However, most studies have focused on species with one pollinator type, and little is known about species with mixed pollination systems. We investigated the temporal variation in flower visitor activity and flower scent emission of Silene otites (Caryophyllaceae), a species regarded as being nocturnal and pollinated by moths and mosquitoes. We found, however, that S. otites is not only visited at night by moths and mosquitoes, but also by a wide range of day‐active insects. Furthermore, both the intensity and composition of floral scent change during the course of the day. Total scent emission reached its maximum in the early hours of the night when compounds known to be attractants for moths and/or mosquitoes, such as lilac aldehyde, benzaldehyde, phenylacetaldehyde and 2‐phenylethanol, dominated the scent. However, although less intensive, emission continued during the day. In the early morning, α‐pinene, hotrienol, 2‐phenylethanol and δ‐3‐carene were the dominant scent compounds. (E)‐β‐Ocimene, hotrienol and benzyl alcohol contributed proportions of at least 10% before midday when flies, such as syrphids, were abundant flower visitors, whereas linalool and hotrienol contributed to the scent with at least 10% each in the afternoon when bees also contributed to flower visits. We conclude that, in S. otites, the changing emission patterns are ‘in tune’ with the olfactory abilities, preferences and activity times of its day‐ and night‐active potentially pollinating flower visitors. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 447–460.     

Retinoic Acid-Induced Cartilage Resorption

The addition of retinoic acid to fetal rat bones in culture induces the release of proteoglycans followed by cartilage resorption. In this system retinoic acid markedly suppressed ³H-leucine and ³H-mannose incorporation into acid-precipitable macromolecules, and specifically changed the ³H-leucine incorporation pattern as revealed by gel electrophoresis. Tunicamycin, which selectively inhibits glycosylation of the asparagine residues in proteins, prevented the cartilage cell degradation in response to retinoic acid. Inhibitors of DNA synthesis did not affect the retinoic acid-induced changes indicating that cell division was not required for the cartilage degradation processes induced by retinoic acid. In consideration of our previous and present demonstrations that retinoic acid-induced cartilage resorption required RNA, protein, and glycoprotein synthesis and specifically changed the protein synthesis pattern, we suggest that retinoic acid may exert its action by altering gene expression.     

Further progress on the phylogeny of Noctuoidea (Insecta: Lepidoptera) using an expanded gene sample

Major progress has been made recently toward resolving the phylogeny of Noctuoidea, the largest superfamily of Lepidoptera. However, numerous questions and weakly supported nodes remain. In this paper we independently check and extend the main findings of multiple recent authors by performing maximum‐likelihood analyses of 5–19 genes (6.7–18.6 kb) in 74 noctuoids representing all the families and a majority of the subfamilies. Our results strongly support the six family system of Zahiri et al., with the former Lymantriidae and Arctiidae subsumed within the huge family Erebidae, and Noctuidae restricted largely to the subfamilies with so‐called trifine hindwing venation. Our data also strongly corroborate monophyly of the set of four families with quadrifid forewing venation, to the exclusion of Notodontidae, and removal from the latter of Oenosandridae. Other among‐family relationships, however, remain unsettled. Our evidence is equivocal on the position of Oenosandridae, which are sister group to either Notodontidae alone or to all other noctuoids. Like other recent nuclear gene studies, our results also provide no strong support for relationships among the four quadrifid forewing families. In contrast, within families our analyses significantly expand the list of robustly resolved relationships, while introducing no strong conflicts with previous molecular studies. Within Notodontidae, for which we present the largest molecular taxon sample to date, we find strong evidence for polyphyly for some, or all, recent definitions of the subfamilies Thaumetopoeinae, Pygaerinae, Notodontinae and Heterocampinae. Deeper divergences are incompletely resolved but there is strong support for multiple ‘backbone’ nodes subtending most of the subfamilies studied. Within Erebidae, we find much agreement and no strong conflict with a recent previous study regarding relationships among subfamilies, and somewhat stronger support. Although many questions remain, the two studies together firmly resolve positions for over half the subfamilies. Within Noctuidae, we find no strong conflict with previous molecular studies regarding relationships among subfamilies, but much stronger resolution along the ‘backbone’ of the phylogeny. Combining information from multiple studies yields strongly resolved positions for most of the subfamilies. Finally, our results strongly suggest that the tribes Pseudeustrotiini and Prodeniini, currently assigned to the largest subfamily, Noctuinae, do not belong there. In sum, our results provide additional corroboration for the main outlines of family‐level phylogeny in Noctuoidea, and contribute toward resolving relationships within families.     

Myrmecophilous butterflies utilise ant–treehopper associations as visual cues for oviposition

1. Selection of a safe oviposition site is important for herbivorous insects whose immature stages have limited mobility. Female herbivores rely on environmental cues for this choice, and presence of natural enemies or mutualistic partners may be important in this process. 2. Some butterflies have mutualistic interactions with ants (myrmecophily), in which caterpillars offer a nutritional liquid and gain protection against natural enemies. Participants in butterfly–ant mutualisms may utilise signals to initiate interactions, but the use of visual cues by ovipositing myrmecophilous butterflies remains uncertain. 3. Larvae of facultatively myrmecophilous Parrhasius polibetes (Lycaenidae) feed on Schefflera vinosa, and females prefer to oviposit near aggregations of the ant‐tended treehopper Guayaquila xiphias, where caterpillars survive better due to increased ant attendance. Given the conspicuousness of ant–treehopper associations, it was investigated whether butterflies use them as visual cues for oviposition and, if so, which participants of the association are used as cues: ants, treehoppers, or both. 4. Experiments using dried insects on paired branches revealed that females visually recognise ants and ant–treehopper associations, using them for egg‐laying decisions. However, presence of a treehopper aggregation alone had no effect on oviposition choices. 5. This is a first insight into the importance of visual discrimination for ovipositing myrmecophilous butterflies. The results show that facultative mutualisms can be important enough to promote a behavioural adaptation (visual detection of ants) reinforcing the interaction. Our research highlights the importance of the behavioural interface within complex multispecies systems.