Colonization and processing of leaf litter by macroinvertebrate shredders in streams of contrasting pH

• 1 Leaf litter processing rates and macroinvertebrate shredder assemblages in leaf packs were compared in four streams on the Allegheny plateau in the central Appalachian Mountains, U.S.A.; these streams were characterized by different bedrock geology and streamwater pH.
• 2 Leaf litter processing rates were fastest in the neutral streams, slowest in the acidic stream, and intermediate in the most alkaline stream.
• 3 Slower processing rates in the acidic stream were associated with lower total shredder biomass, made up predominantly by small leuctrid and nemourid stoneflies.
• 4 The differences in processing rates between the more alkaline stream and the neutral streams were not associated with differences in shredder biomass, but appeared to be related to taxonomic differences in the shredder assembiages. Insects were dominant in the neutral streams, and amphipods were dominant in the more alkaline stream.

     

Use of Stable Isotope Methodology to Determine Natal Origins of Mallards at a Fine Scale Within the Upper Midwest

Abstract: Waterfowl managers often attempt to protect local breeding stocks of mallards (Anas platyrhynchos) from hunting pressure, but presently they cannot identify natal origins of birds shot during fall hunting seasons with certainty, unless recovered birds are banded before fledging. Accordingly, we examined whether stable isotope methodology could accurately delineate natal origins of mallards at a fine scale within the upper Midwest (USA). We determined δ¹³C, δD, and δ¹⁵N values from feather samples of 102 flightless mallard ducklings collected in Minnesota, North Dakota, South Dakota, and Wisconsin, USA, from 7 July to 9 September 2002. We detected inverse relationships between latitude and δ¹³C(R² = 0.223) and δD(R² = 0.210). We also detected a weak positive relationship between easterly shifts in longitude and δ¹³C(R² = 0.067) and a weak negative relationship between easterly shifts in longitude and δ¹⁵N(R² = 0.076). The ¹³C and deuterium values differed (P < 0.02) among states: North Dakota was most depleted in ¹³C, and South Dakota was least depleted in deuterium. Discriminant function analysis delineated natal origins of mallard ducklings in Minnesota, North Dakota, South Dakota, and Wisconsin with low-to-moderate accuracy (47%), whereas we predicted natal origins of ducklings among subregions (Prairie [ND, SD] vs. Great Lakes [MN, WI] states) with moderate accuracy (72%). We conclude that stable isotope methodology has a limited ability to determine natal origins of migratory birds along a longitudinal corridor at fine scales but that it improves across ecoregions. However, the ability of deuterium to determine natal origins of migratory birds may vary as hydrological conditions, within and among areas, change throughout time. Researchers should account for annual variation in deuterium found in surface waters when investigating natal origins of migratory birds that use food derived primarily from these waters.     

Other faces in the mirror: a perspective on schizophrenia

A patient with schizophrenia may generate an action (whether manual or verbal), but not attribute the generation of that action to himself. We distinguish self-monitoring and attribution of agency, relating only the former to forward models and the mirror system. We suggest that alien hand experiences occur when an action progresses through hand control pathways with no record of disinhibition having been kept and is then seen but dismissed as external. Analogously, auditory pathways are active during verbal hallucinations and produce a subvocal verbal process, but since no record is kept of the words being created, they are treated as external. The subject then proceeds to confabulate, to provide an account for the agency.     

Development of 22 new microsatellite loci for fishers (Martes pennanti) with variability results from across their range

We developed 22 new microsatellite loci for the fisher (Martes pennanti), a North American mesocarnivore. The loci were developed with samples from the southern Sierra Nevada Mountains in California, and were screened with samples from this population and four other populations. We observed a range of six to 21 polymorphic loci per population, with the Sierra Nevada population exhibiting markedly lower levels of variation compared to the other four.     

Can we bring Madagascar's critically endangered palms back from the brink? Genetics,ecology and conservation of the critically endangered palm Beccariophoenix madagascariensis

Madagascar has a highly distinctive flora and is one of the world biodiversity hot spots. There are more than 170 species of palms, the majority of which are vulnerable, endangered or critically endangered endemics. Palms are utilized for many human uses, many of which lead to plant death or seed harvesting. Combined with reduced populations resulting from extensive forest clearing, those species which are harvested from the wild are under additional threat of extinction. Species recovery programmes have the potential to save some of the most iconic species before it is too late. This study documented the current known populations of the critically endangered palm Beccariophoenix madagascariensis, a species utilized for both local and international purposes. The study specifically investigated the genetic diversity and inbreeding within populations and the potential differentiation between populations and with the newly described species B. alfredii . We found that despite critically small population sizes there was considerable genetic diversity within populations. We also found that ecologically and or geographically distinct populations were genetically distinct. Populations within 3 km of each other exhibited considerable gene flow, probably owing to seed dispersal. The populations were inbred but reproductive viability had been maintained. Conservation and recovery options are discussed. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 154 , 589–608.     

Stasipatric speciation: resurrecting a system to bury a hypothesis?

The process of speciation remains a fundamental topic in evolutionary biology. Numerous models of speciation have been proposed and they are as diverse and colourful as the scientists who conceived them ( Coyne & Orr 2004 ). One of the more controversial theories has been the ‘stasipatric speciation’ model, proposed by the pioneering and influential cytogeneticist Michael White and his co‐workers ( White 1968 ; White et al. 1967 ). This is one of a number of speciation models whereby chromosomal rearrangements drive the speciation process. The inspiration for the theory of stasipatric speciation came from White’s karyotypic analyses of a group of Australian grasshoppers of the genus Vandiemenella ( White et al. 1967 ) ( Fig. 1 ). It has been exactly three decades since the last scientific publication on this group of grasshoppers, over which time the molecular revolution dramatically altered the landscape of evolutionary genetics. Kawakami and colleagues have successfully resurrected the Vandiemenella system ( Kawakami et al. 2009a, 2007 ) and in this issue they have applied modern molecular‐based techniques to reassess the validity of the stasipatric speciation model for this historically important group ( Kawakami et al. 2009b ).

Figure 1 Open in figure viewer PowerPoint The grasshopper (Vandiemenella viatica) that inspired Michael White to develop the stasipatric speciation model (photograph by Remko Leijs).     

The land–atmosphere water flux in the tropics

Tropical vegetation is a major source of global land surface evapotranspiration, and can thus play a major role in global hydrological cycles and global atmospheric circulation. Accurate prediction of tropical evapotranspiration is critical to our understanding of these processes under changing climate. We examined the controls on evapotranspiration in tropical vegetation at 21 pan-tropical eddy covariance sites, conducted a comprehensive and systematic evaluation of 13 evapotranspiration models at these sites, and assessed the ability to scale up model estimates of evapotranspiration for the test region of Amazonia. Net radiation was the strongest determinant of evapotranspiration (mean evaporative fraction was 0.72) and explained 87% of the variance in monthly evapotranspiration across the sites. Vapor pressure deficit was the strongest residual predictor (14%), followed by normalized difference vegetation index (9%), precipitation (6%) and wind speed (4%). The radiation-based evapotranspiration models performed best overall for three reasons: (1) the vegetation was largely decoupled from atmospheric turbulent transfer (calculated from Ω decoupling factor), especially at the wetter sites; (2) the resistance-based models were hindered by difficulty in consistently characterizing canopy (and stomatal) resistance in the highly diverse vegetation; (3) the temperature-based models inadequately captured the variability in tropical evapotranspiration. We evaluated the potential to predict regional evapotranspiration for one test region: Amazonia. We estimated an Amazonia-wide evapotranspiration of 1370 mm yr⁻¹, but this value is dependent on assumptions about energy balance closure for the tropical eddy covariance sites; a lower value (1096 mm yr⁻¹) is considered in discussion on the use of flux data to validate and interpolate models.     

Environmental indicator potential of the dominant litter decomposer,Talitriator africana (Crustacea,Amphipoda) in Afrotemperate forests

Abstract Environmental disturbance and condition are complex concepts to define and measure in forested landscapes. The highly fragmented Afrotemperate forests in South Africa are under increasing pressure from the agricultural matrix and resource harvesting. Rapid assessment of forest condition and disturbance would aid their conservation management. The terrestrial amphipod, Talitriator africana, dominates the decomposer guild of Afrotemperate forests and has been previously identified as a potential indicator of forest condition. Using four published studies, we further evaluate this species' suitability as an environmental indicator of forest disturbance and condition. Amphipods were consistently more abundant at highly disturbed forest edges compared to less disturbed interiors, and less abundant in deep litter compared to shallow litter. High amphipod numbers in shallow litter was correlated with low predator abundance. Shallow litter may in turn be caused by more efficient breakdown of litter by amphipods at forest edges. Numbers varied considerably between sites and years, but showed a consistent trend of high abundance with increasing forest disturbance. The latter, and the ease with which it can be surveyed and identified, make a compelling case for the use of T. africana as a single‐species environmental indicator of forest disturbance. However, relatively broad tolerances and the difficulty of calibrating the abundance‐disturbance relationship over a wide region limits the indicator value of this species to the local landscape, where disturbance effects vary only in their intensity (as opposed to type) across forests.