Range size in North American Enallagma damselflies correlates with wing size

1. Cross-species macroecological comparisons in freshwater invertebrates have been restricted by a lack of large-scale distributional data, and robust phylogenies. Here, we use data from the OdonataCentral database to explore body length–range size and wing length–range size relationships in damselflies from the genus Enallagma ; the recent publication of a phylogeny for this group meant that, as well as a cross-species analysis, we were able to assess relationships in a phylogenetically controlled manner.
2. For cross-species comparisons, only wing length showed significant (positive) regression relationships with range size and occupancy, although the inclusion of body length in multiple regressions increased the fit of the models. Damselflies with larger wings relative to their body length had larger distributions, a result confirmed by a significant positive relationship between range size and residuals from the regression of wing size on body size.
3. For the phylogenetically controlled analyses, only wing length contrast scores were significantly related to distribution patterns and entered into regression models; the significant positive relationships between wing length contrasts and both range size and occupancy contrasts suggested that evolutionary increases in wing length had occurred alongside range expansions.
4. Together these results suggest that species of Enallagma with larger wings (both absolute and relative to body length) tend to be more widely distributed in North America and that the evolution of wing size may have played a role in range expansion. No such relationships were evident for body size. We discuss the potential importance of wing morphometrics for studying the evolutionary ecology of freshwater insects.     

Observations of gynoecial structure in Philodendron (Araceae)

MAYO, S. J., 1989. Observations of gynoecial structure in Philodendron (Araceae). The gynoecial morphology and anatomy of 15 species of the genus Philodendron , representing all the subgenera and a majority of the sections, are described and illustrated. The study emphasizes the morphology of the style, compitum and stylar canals; gynoecial vasculature is only superficially treated. Variation of gynoecial morphology in P . subgenus Meconostigma is described and illustrated and a pilot study of gynoecial ontogeny in this subgenus is presented. Ideas on phylogenetic trends in style and stylar canal morphology, ovary locule number, placentation and ovule number are discussed. Gynoecial characters are shown to be taxonomically useful at the subgeneric and sectional level in Philodendron. The following taxonomic and nomenclatural changes are made: P. section Pteromischum is raised to subgeneric rank. In P. subgenus Philodendron sections Polyspermium and Oligospermium are reduced to the synonymy of sections Philodendron and Calostigma respectively, and the following new names and combinations are made at subsectional rank: subsections Canniphyllum, Oligocarpidium, Bulaoanum and Eucardium.     

The regional variation of aboveground live biomass in old-growth Amazonian forests

The biomass of tropical forests plays an important role in the global carbon cycle, both as a dynamic reservoir of carbon, and as a source of carbon dioxide to the atmosphere in areas undergoing deforestation. However, the absolute magnitude and environmental determinants of tropical forest biomass are still poorly understood. Here, we present a new synthesis and interpolation of the basal area and aboveground live biomass of old‐growth lowland tropical forests across South America, based on data from 227 forest plots, many previously unpublished. Forest biomass was analyzed in terms of two uncorrelated factors: basal area and mean wood density. Basal area is strongly affected by local landscape factors, but is relatively invariant at regional scale in moist tropical forests, and declines significantly at the dry periphery of the forest zone. Mean wood density is inversely correlated with forest dynamics, being lower in the dynamic forests of western Amazonia and high in the slow‐growing forests of eastern Amazonia. The combination of these two factors results in biomass being highest in the moderately seasonal, slow growing forests of central Amazonia and the Guyanas (up to 350 Mg dry weight ha^?1) and declining to 200–250 Mg dry weight ha^?1 at the western, southern and eastern margins. Overall, we estimate the total aboveground live biomass of intact Amazonian rainforests (area 5.76 × 10⁶ km² in 2000) to be 93±23 Pg C, taking into account lianas and small trees. Including dead biomass and belowground biomass would increase this value by approximately 10% and 21%, respectively, but the spatial variation of these additional terms still needs to be quantified.     

Modeling a Neural Oscillator that Paces Heartbeat in the Medicinal Leech

SYNOPSIS. Heartbeat in the medicinal leech is paced by a neuraloscillator comprising two elemental oscillators whose activityis coordinated intersegmental coordinating fibers. The elementaloscillators each consist of a bilateral pair of heart interneuronslinked by reciprocal inhibitory synapses. The activity cycleof each elemental oscillator consists of alternating burstsof action potentials (plateau/burst phase) and periods inhibition(inactive phase). Oscillation ensues in the reciprocally inhibitorypairs because each neuron is able to escape from the inhibitionits contralateral partner and thus move on to the plateau/burstphase. We have identified and described membrane currents thatcontribute to oscillation and studied graded synaptic transmissionbetween the neurons, using discontinuous current clamp and switchingsingle electrode voltage clamp techniques. A hyperpolarization-activatedinward current, Ih, plays a major role in escape from inhibition,and Ca²⁺ currents produce plateau potentials that support burstformation and mediate graded synaptic transmission. To consolidate our knowledge and guide future research, we haveconstructed a first generation computer model of a neural oscillatorbased on reciprocal inhibition, using Hodgkin-Huxley equationsand a synaptic transfer model, derived from our biophysicalstudies, with Nodus software (De Schutter, 1989). This modelhas confirmed an important role for I_h in sustaining oscillationand has implicated a similarly important role for outward currents(particularly I_A), which remain to be studied. Neural oscillatorsbased on reciprocal inhibition appear to be ubiquitous, andour studies, biophysical and computational, provide insightsinto how they may operate.     

Winter field use and habitat selection by Eurasian Golden Plovers Pluvialis apricaria and Northern Lapwings Vanellus vanellus on arable farmland

Eurasian Golden Plovers Pluvialis apricaria and Northern Lapwings Vanellus vanellus winter in large numbers on Britain's farmland. Previous studies in mixed farming areas showed pronounced preferences for permanent pasture, but increasing numbers of plovers winter in eastern Britain where arable farmland dominates. We show that an area of intensive arable farmland supported significant numbers of both species from October to February in the absence of large areas of pasture. Habitat use varied seasonally as the habitats present changed. Throughout winter, use of cereal crops matched their availability: plovers selected harrow in early winter, sugar beet stubbles in midwinter and other crops in late winter. Pastures were rarely used at any time of the year. Flocks occupied only a fraction of the available fields, concentrating most in large fields with open boundaries and where manure had been applied. Daytime feeding was more likely during cold days after nights with a new moon, short duration of moonlight or low-intensity moonlight. These results show that plovers are currently able to utilize intensive arable farmland but future changes in management, such as cessation of manure applications and reductions in sugar beet cropping, could have detrimental effects.     

Between‐species facilitation by male fig wasps in shared figs

1. Facilitation is recorded from diverse plant–insect interactions, including pollination and herbivory. 2. The significance of facilitation resulting from the behavior of males of multiple fig wasp species inside figs was investigated. Female fig wasps emerge from natal figs via exit holes dug by males, especially male pollinators. When no males are present, the females struggle to escape and may die. 3. Ficus microcarpa L. is a widely‐established invasive fig tree from Southeast Asia. Its pollinator is absent in South Africa, so the tree cannot reproduce, but two Asian non‐pollinating fig wasps (NPFW) Walkerella microcarpae and Odontofroggatia galili occupy its figs. Abundance patterns of the two NPFW and the proportion of male‐free figs in South Africa, Spain (where the pollinator is introduced), and in China, where the native fig wasp community is diverse, were compared to determine the consequences of reduced species richness for insect survival. 4. Female fig wasps in male‐free figs were found to be trapped, and small clutch sizes contributed to the absence of males in both species. The presence of pollinators in Spain allowed most NPFW to develop in figs containing males. Far more male‐free figs were present in South Africa, elevating mortality rates among female NPFW. Facilitation of female release by males of other NPFW species nonetheless benefitted the rarer species. 5. Selection pressures in South Africa currently favour greater aggregation of NPFW offspring and/or less female biased sex ratios.     

Incorporating Movement Behavior and Barriers to Improve Kernel Home Range Space Use Estimates

Abstract: Kernel-based utilization distribution (UD) estimates are powerful tools to investigate home range space use and resource selection in many vertebrate species. By ignoring local movement information provided by the serial correlation between successive locations and the constraints to movement imposed by obvious boundaries, the classical kernel method results in loosely estimated UDs that tend to overflow into never-visited areas and eventually in possibly biased estimates of space use and habitat selection. We improved biological relevance of kernel home range space use estimates by incorporating both movement (and activity) information and boundary constraints.