Global characterization of fire activity: toward defining fire regimes from Earth observation data

There is interest in the global community on how fire regimes are changing as a function of changing demographics and climate. The ground-based data to monitor such trends in fire activity are inadequate at the global scale. Satellite observations provide a basis for such a monitoring system. In this study, a set of metrics were developed from 6 years of MODIS active fire data. The metrics were grouped into eight classes representing three axes of fire activity: density, season duration and interannual variability. These groups were compared with biophysical and human explanatory variables on a global scale. We found that more than 30% of the land surface has a significant fire frequency. The most extensive fire class exhibited high fire density, low duration and high variability and was found in boreal and tropical wet and dry environments. A high association was found between population distribution and fire persistence. Low GDP km⁻² was associated with fire classes with high interannual variability and low seasonal duration. In areas with more economic resources, fires tend to be more regular and last longer. High fire duration and low interannual variability were associated with croplands, but often with low fire density. The study was constrained by the limited length of satellite data record but is a first step toward developing a comprehensive global assessment of fire regimes. However, more attention is needed by the global observing systems to provide the underpinning socio-economic observations to better quantify and analyze the human characteristics of fire regimes.     

Simulated glacial and interglacial vegetation across Africa: implications for species phylogenies and trans-African migration of plants and animals

The paleoenvironmental context of plant and animal species evolution (including glacial migrations and population separations) is based on a very patchy and incomplete paleo‐phytogeographic record. It was our objective, therefore, to provide an additional source for paleovegetation comparison by presenting simulations from a state‐of‐the‐art fully coupled earth system model (HadCM3LC). We simulated potential paleovegetation distributions following pre‐Industrial and last glacial maximum (LGM) climate forcing for the continent of Africa. Our LGM simulations indicate that tropical broadleaf forest was not severely displaced by expanding grasslands within central Africa, although the outer extent of closed forest decreases, particularly in the north. Our simulations indicate that the structure of glacial forests may have been much different from today, in that LGM simulations indicate that forests were likely characterized by lower leaf area indexes, lower tree heights and lower vegetation carbon content. On the other hand, warmer interglacial climate (like our pre‐Industrial climate scenario) results in simulated expansion of tropical forest from coast to coast across central Africa that we postulate could have acted as a barrier to plant and animal species migrations. We suggest that our modeling experiments have implications for the interpretation of phylogenetic data, including that of our own species, Homo sapiens sapiens.     

Widespread mito‐nuclear discordance with evidence for introgressive hybridization and selective sweeps in Lycaeides

We investigated the extent and potential cause(s) of mitochondrial introgression within the polytypic North American Lycaeides species complex (Lepidoptera). By comparing population genetic structure based on mitochondrial DNA (COI and COII) and nuclear DNA (251 polymorphic amplified fragment length polymorphism markers), we detected substantial mito‐nuclear discordance, primarily involving a single mitochondrial haplotype (h01), which is likely due to mitochondrial introgression between differentiated Lycaeides populations and/or species. We detected reduced mitochondrial genetic diversity relative to nuclear genetic diversity in populations where mitochondrial haplotype h01 occurs, suggesting that the spread of this haplotype was facilitated by selection. We found no evidence that haplotype h01 is associated with increased fitness (in terms of survival to eclosion, fresh adult weight, and adult longevity) in a polymorphic Lycaeides melissa population. However, we did find a positive association between mitochondrial haplotype h01 and infection by the endoparasitic bacterium Wolbachia in one out of three lineages tested. Linkage disequilibrium between mitochondrial haplotype h01 and Wolbachia infection status may have resulted in indirect selection favouring the spread of haplotype h01 in at least one lineage of North American Lycaeides. These results illustrate the potential for introgressive hybridization to produce substantial mito‐nuclear discordance and demonstrate that an individual's mitochondrial and nuclear genome may have strikingly different evolutionary histories resulting from non‐neutral processes and intrinsic differences in the inheritance and biology of these genomes.     

The phylogeny of the superfamily Coccoidea (Hemiptera: Sternorrhyncha) based on the morphology of extant and extinct macropterous males

Currently, 49 families of scale insects are recognised, 33 of which are extant. Despite more than a decade of DNA sequence‐based phylogenetic studies of scales insects, little is known with confidence about relationships among scale insects families. Multiple lines of evidence support the monophyly of a group of 18 scale insect families informally referred to as the neococcoids. Among neococcoid families, published DNA sequence‐based estimates have supported Eriococcidae paraphyly with respect to Beesoniidae, Dactylopiidae, and Stictococcidae. No other neococcoid interfamily relationship has been strongly supported in a published study that includes exemplars of more than ten families. Likewise, no well‐supported relationships among the 15 extant scale insect families that are not neococcoids (usually referred to as ‘archaeococcoids’) have been published. We use a Bayesian approach to estimate the scale insect phylogeny from 162 adult male morphological characters, scored from 269 extant and 29 fossil species representing 43/49 families. The result is the most taxonomically comprehensive, most resolved and best supported estimate of phylogenetic relationships among scale insect families to date. Notable results include strong support for (i) Ortheziidae sister to Matsucoccidae, (ii) a clade comprising all scale insects except for Margarodidae s.s., Ortheziidae and Matsucoccidae, (iii) Coelostomidiidae paraphyletic with respect to Monophlebidae, (iv) Eriococcidae paraphyletic with respect to Stictococcidae and Beesoniidae, and (v) Aclerdidae sister to Coccidae. We recover strong support for a clade comprising Phenacoleachiidae, Pityococcidae, Putoidae, Steingeliidae and the neococcoids, along with a sister relationship between this clade and Coelostomidiidae + Monophlebidae. In addition, we recover strong support for Pityococcidae + Steingeliidae as sister to the neococcoids. Data from fossils were incomplete, and the inclusion of extinct taxa in the data matrix reduced support and phylogenetic structure. Nonetheless, these fossil data will be invaluable in DNA sequence‐based and total evidence estimates of phylogenetic divergence times.     

Partitioning of temporal activity among desert lizards in relation to prey availability and temperature

Partitioning of activity time within ecological communities potentially reduces interspecific competition and increases the number of species that can coexist. We investigated temporal activity in a highly diverse lizard assemblage in the Simpson Desert, central Australia, to determine the degree of partitioning that occurs. Three periods were defined, daytime (sunrise to sunset), early night (sunset to midnight) and late night (midnight to sunrise), and live captures of lizards were tallied for each period during two sampling months (September and November 2007). We also quantified the activity times of potential invertebrate prey and measured ambient temperatures during the different time periods to investigate any associations between these factors and lizard activity. Some 77% of captures of 13 lizard species were made by day, with Ctenotus pantherinus, Egernia inornata (Scincidae) and Nephrurus levis (Gekkonidae) the only species showing extended nocturnal activity. Activity of both species of skink was recorded at temperatures 4°C lower than those for agamid and varanid lizards early in the night, and at temperatures as low as 18–20°C. Surface‐active invertebrates differed in composition between time periods and were less abundant during the late night period in the drier of the two sample months (September), but were distributed equally over time in the other month. Termites were active in subterranean galleries at night in September and mostly by day in November, but available at all times on surface/subsurface baits. We conclude that activity is distributed unevenly within this lizard assemblage, with partitioning facilitated by the ready availability of invertebrate prey and by lizards having relatively broad temperature tolerances that, in some cases, permit opportunistic exploitation of resources beyond usual times of activity.     

Variation in litter under individual tree crowns: Implications for scattered tree ecosystems

In forest ecosystems litter is usually assessed in terms of the average amount produced by the canopy. In scattered tree ecosystems this approach is problematic because the canopy is discontinuous and the spatial arrangement of litter highly variable. We addressed this problem by quantifying the spatial variation in litter load and litter composition associated with individual trees in a Eucalyptus melliodora – Eucalyptus blakelyi woodland. Litter was sampled under crowns and in grassland adjacent to 10 E. blakelyi and 10 E. melliodora trees ranging in diameter at breast height (dbh) from 14 to 129 cm. A total of 302 L samples were collected from these trees, at distances ranging from 0 to 42 m from main stem. The sampled litter loads ranged from 0.02 to 109.3 t ha^?1 and were significantly higher under tree crowns than in grassland for litter and each component of litter (leaves, bark, fine twigs, coarse twigs). In particular, the mean litter load under tree crowns (12.5 t ha^?1) was an order of magnitude higher than the mean litter load in grassland (1.27 t ha^?1). There was a significant (P = 0.0103) positive relationship between mean litter load under the tree crown and dbh, indicating larger trees produced more litter per unit area of ground than smaller trees. Generalized Linear Modelling produced highly significant (P < 0.0001) models predicting the spatial variation in litter load and litter composition in terms of distance from main stem and dbh. Our models demonstrate gradients in litter load and composition under tree crowns. These gradients were most pronounced for the large trees in our study. The disproportionate input of litter and variety of litter components associated with large trees in our study supports their keystone role in scattered tree ecosystems and highlights the need to maintain these structures in agricultural landscapes.     

Laboratory evaluation of the toxic properties of forest anchomanes, Anchomanes difformis against pulse beetle Callosobruchus maculatus （Coleoptera： Bruchidae）

Laboratory experiments were carried out to investigate the efficacy of crude stem extracts of forest anchomanes, Anchomanes difformis （P. Beauv.） a plant occurring in West African forests, against the pulse beetle Callosobruchus maculattts （Fabricius）. Crude stem extracts at 3% concentration showed high contact toxicity to adult beetles within 24 h after application, while it was moderately toxic to the beetles at the lowest （1%） concentration. At the highest application rate, the plant extract provided good protection to grains stored for 90 days. Grain viability and water absorption capacity were not affected by treatments with ethanol extracts ofA. difformis. The significance of these findings is discussed in relation to biopesticide-means of controlling cowpea bruchids.     

Origins and characteristics of Nearctic landbirds in Britain and Ireland in autumn: a statistical analysis

We used data from eastern North America in regressions to explain autumn frequencies of Nearctic landbird species in Britain and Ireland (UK‐IR). The data were: day‐counts of 16 August–15 November from Nova Scotia (NS) on Sable Island 1963–2000 and Seal Island (1963–2002), combined in half‐monthly intervals to account for seasonality; published seasonal totals (10‐ to 11‐day intervals, 20 August–10 November 1955–80) of birds killed at a Florida (FL) TV tower; and published counts following a ‘Fallout’, 11 October 1998, of unseasonal species and southern vagrants in NS, believed to have originated as migrants in the southeast USA that followed a cold front offshore into strong southwest flow beyond. We also used the following species variables: body mass and wing length for size; sd of mass as a proxy for lipid capacity; a five‐level index of migratory span (1 for within North America to 5 for almost totally to South America); latitude of easternmost breeding, and distance to nearest normal range to indicate status in NS; a two‐level index for day vs. night migrants; an index, where pertinent, of significant population change (0 and 2 for a decrease and increase, respectively, 1 for no change). We also used classification and regression trees to cluster the potential transatlantic vagrants into homogeneous groups based on the explanatory variables. Standard generalized linear model regressions using counts from NS islands and FL produced highly positively skewed residuals (many species too common in UK‐IR), but robust regressions eliminated statistical problems, and strengthened effects of non‐count variables. Results using Fallout records, representing a subset of longer‐distance night migrants, were statistically acceptable. The Fallout list, when supplied with counts from the same species from the NS islands and FL, produced highly significant (R² = 0.79–0.93) and statistically acceptable regressions that were not improved by robust versions. Overall, the results indicate that October counts, especially of generally larger, longer‐distance migrants, best represented those reaching UK‐IR. The effect of geographical remoteness was negative – vagrants in NS were less likely to appear in UK‐IR. Population changes were important in predicting the 1956–2003 UK‐IR counts from 1955–80 FL counts. The seasonal characteristics, high explanatory power of the Fallout list and over‐representation of probable over‐ocean migrants in the standard regressions all support suggestions by others that many Nearctic vagrants in UK‐IR originate in flights off southeast USA and are displaced downwind across the North Atlantic.     

Polymorphic microsatellite loci isolated from the great scallop,Pecten maximus (Bivalvia: Pectinidae)

We isolated and characterized nine polymorphic microsatellite loci from the great scallop (Pecten maximus) as part of an attempt to better understand the population–genetic structure of this species. Levels of genetic diversity were assessed in 32 scallops collected from the coastal waters of Port Erin Bay, Isle of Man. The number of alleles ranged from two to 29 and observed and expected heterozygosities varied between 0.031 to 0.906 and 0.062 to 0.973, respectively. Two loci showed significant (P < 0.05) heterozygote deficits, likely because of null (nonamplifying) alleles; one pair of loci was in linkage disequilibrium.