Plant traits and wood fates across the globe: rotted,burned, or consumed?

Wood represents the defining feature of forest systems, and often the carbon in woody debris has a long residence time. Globally, coarse dead wood contains 36–72 Pg C, and understanding what controls the fate of this C is important for predicting C cycle responses to global change. The fate of a piece of wood may include one or more of the following: microbial decomposition, combustion, consumption by insects, and physical degradation. The probability of each fate is a function of both the abiotic environment and the wood traits of the species. The wood produced by different species varies substantially in chemical, micro- and macro-morphological traits; many of these characteristics of living species have 'afterlife' effects on the fate and turnover rate of dead wood. The colonization of dead wood by microbes and their activity depends on a large suite of wood chemical and anatomical traits, as well as whole-plant traits such as stem-diameter distributions. Fire consumption is driven by a slightly narrower range of traits with little dependence on wood anatomy. Wood turnover due to insects mainly depends on wood density and secondary chemistry. Physical degradation is a relatively minor loss pathway for most systems, which depends on wood chemistry and environmental conditions. We conclude that information about the traits of woody plants could be extremely useful for modeling and predicting rates of wood turnover across ecosystems. We demonstrate how this trait-based approach is currently limited by oversimplified treatment of dead wood pools in several leading global C models and by a lack of quantitative empirical data linking woody plant traits with the probability and rate of each turnover pathway. Explicitly including plant traits and woody debris pools in global vegetation climate models would improve predictions of wood turnover and its feedback to climate.     

Esterase Variants in Four Species of the Paramecium aurelia Complex1

One hundred eighty-eight stocks of Paramecium primaurelia, P. biaurelia, P. tetraurelia, and P. octaurelia were grown axenically and tested for five esterases, visualized by starch gel electrophoresis, in a search for variant stocks. The five esterases can be distinguished on the bases of their substrate specificity, sensitivity to an inhibitor, and response to different growth conditions. This paper addresses the nature of the electrophoretic change in mobility of the variant stocks in order that species relationships can be more accurately assessed. Crosses carried out in all four species show that single genes determine the differences in mobility between variant and common subtypes. Extracts of variant stocks that gave similar patterns were run against each other, tested for their sensitivity to the inhibitor, and the pattern was compared to that found in extracts of stocks with variant and common subtypes in other species. The majority of the variants in P. primaurelia, P. tetraurelia, and P. octaurelia show an electrophoretic mobility characteristic of a common subtype, or a variant, in another species. The same proportion of variant subtypes as common subtypes have mobilities similar to esterase subtypes found in other species. Of the four species examined in this paper, P. tetraurelia and P. octaurelia appear to be most closely related on the basis of shared esterase subtypes. In P. biaurelia the mobilities of most of the variants are unique, as are the common esterase subtypes in this species. P. biaurelia stands out as having the greatest number of esterase subtypes, with very few of them homologous to subtypes found in other species. This observation supports the idea of greater diversification of stocks within P. biaurelia than for the other three species.     

Uncovering different parameters influencing florivory in a specialist herbivore

1. It has become increasingly recognised that several herbivores switch from folivory (leaf‐feeding) to florivory (flower‐feeding) during larval development. Yet, it remains poorly understood which cues influence this behaviour, whether a switch to florivory is consistently shown on different hosts, and to what extent florivory could be hindered by plant traits. 2. Using the sawfly Athalia rosae and two Brassicaceae differing in architecture and surface structure, the cues that influence larval movement to the flowers were investigated. A broad set of behavioural assays was employed and physical and chemical plant traits potentially affecting the larvae were analysed. Furthermore, the consequences of folivory versus florivory on insect performance were studied. 3. The larvae preferred flowers over leaves. Consumption of particular flower parts correlated partly with measured plant traits such as glucosinolate distribution. Visual cues were of higher importance than volatile cues. The initial position of newly hatched larvae on plants influenced the probability of the larvae reaching the flowers during development. Trichomes and surface waxes hindered the larvae from moving upwards to the flowers. Larvae developed slower and gained less body mass when feeding on inflorescences of Brassica nigra than when feeding on leaves, in contrast to the patterns observed before on Sinapis alba, where florivory led to an improved performance. 4. This study demonstrates that florivory depends on various host plant traits. It reveals new insights into different parameters influencing this multifaceted phenomenon and into the expected impact on the ecology and fitness of both the attacking herbivores and the plants.     

Fighting in fig wasps: do males avoid killing brothers or do they never meet them?

1. In many fig wasp species, armoured wingless males regularly engage in lethal fights for access to females inside figs, which act as discrete mating patches. 2. Kin selection generally opposes killing brothers, because their reproductive success provides indirect genetic benefits (inclusive fitness). However, siblicide may be avoided if (i) brothers do not occur in the same figs, or (ii) males avoid fighting brothers in the same fig. Alternatively, (iii) siblicide may occur because intense mate competition between brothers at the local scale overcomes kin selection effects, or (iv) males do not recognise kin. 3. A fig may also contain wasps from other closely related species and it is not known if males also fight with these individuals. 4. Nine microsatellite loci were used in the first genetic analysis of fighting in fig wasps. We assigned species and sibling identities to males and tested alternative fighting scenarios for three Sycoscapter wasp species in figs of Ficus rubiginosa. 5. Approximately 60% of figs contained males from more than one Sycoscapter species and approximately 80% of fights were between conspecifics, but a surprising 20% were between heterospecific males. 6. Within species, few figs contained brothers, suggesting that females typically lay one son per fig. Overall, most males do not compete with brothers and all fights observed were between unrelated males.     

A cyanobacterial bloom prevents fish trophic cascades

1. We experimentally compared the impacts of visually feeding zooplanktivorous fish and filter‐feeding omnivorous fish in shallow tropical Dakar Bango reservoir, Senegal. We provoked a cyanobacterial Anabaena bloom under mesotrophic to eutrophic N‐limited conditions in 18 enclosures assigned to six Nile tilapia life‐stage treatments, at typical biomasses: fishless control (C), zooplanktivorous fry (Z), omnivorous juveniles (O), herbivorous fingerlings (H) and two combinations (OZ, OH). 2. All fish grew well, but as prevalent inedible phytoplankton dampened fish effects, community‐level trophic cascades did not occur. Planktivore types acted independently and affected differentially the biomasses of total zooplankton, cyclopoids, nauplii, cladocerans, invertebrate carnivores, large herbivores, colonial cyanobacteria and Chlorophyta. They neither influenced the total biomass of phytoplankton, nor most water chemistry characteristics. Responses were apparently not fish‐biomass related. The bloom collapsed synchronously in all enclosures, coinciding with enrichment ending, with a return to clear water within 12 days. 3. Our results support the hypothesis that excess nutrients and prevalent inedible cyanobacteria inhibit the cascading effects of natural biomass levels of both visually feeding zooplanktivores and filter‐feeding omnivores. In N‐limited meso‐eutrophic shallow tropical lakes with predominantly small herbivorous zooplankton, neither the type nor the biomass of planktivorous fish present seems likely to prevent the transient outburst of cyanobacterial blooms. Such fragile ecosystems may thus not sustain a trophic state suitable for drinking water production, unless human impacts are restricted. The generality of restoration approaches based on ecological engineering should be further explored.     

Biological and environmental degradation of gorilla hair and microsatellite amplification success

Naturally shed hairs are an important source of genetic material for both conservation and forensics but are notoriously poor sources of DNA. DNA degradation in hair roots is caused by apoptosis as part of the cycle of hair growth and by autolysis in decomposing animals. Shed hairs are additionally exposed to degenerative environmental processes. However, genetic studies rarely examine hair root morphologies or refer to root growth phases prior to analysis, and detailed knowledge of the rapidity of DNA degradation amongst shed hairs is lacking. We examined the effects of biological and environmental processes on western lowland gorilla ( Gorilla gorilla gorilla Savage and Wyman) hair roots with respect to morphological characteristics and polymerase chain reaction (PCR) success at eight nuclear loci. Root type frequencies indicate that gorilla body hairs may exhibit a longer telogen phase than human head hairs. All plucked hair root types amplified more efficiently than shed hairs, and only 41% of shed hairs had root types considered suitable for genotyping. Telogen hairs from fresh nests were four-fold more useful for genotyping if the roots were associated with translucent epithelial tissue, and preselection of these root types doubled the overall data-yield to 58%. Nest age correlated with root morphology and PCR success, and PCR success was almost halved after 3 days of exposure. Finally, an association between postmortem interval, root morphology, and PCR success was observed that was consistent with postmortem changes reported in human head hairs.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 281–294.     

Cyclone damage sustained by riparian revegetation sites in the Tully‐Murray floodplain,Queensland, Australia

Abstract Cyclones have been instrumental in shaping the structural and floristic composition of tropical forests, including tropical rainforests of north Queensland, Australia. The response of tropical riparian rehabilitation sites to cyclonic wind damage, however, is currently unknown. This lack of knowledge may severely hamper long‐term success of riparian restoration efforts, particularly in light of predictions that cyclones in north Queensland may become less frequent but more severe. In this study, we examined the extent, type and magnitude of damage inflicted on revegetation works in the Tully‐Murray floodplain of north Queensland by Severe Tropical Cyclone Larry. We compared wind damaged in 20 paired revegetated and associated rainforest remnant sites, using (i) gross community damage scores, (ii) mean weighted damage scores, and (iii) type of damage sustained by individual plants. Overall, wind damage due to Severe Tropical Cyclone Larry was surprisingly similar in revegetated and remnant sites. Both gross community damage scores and mean weighted damage scores did not differ between paired revegetated and remnant sites. In contrast, the type of damage sustained by individual plants was not independent of site, with a larger proportion in revegetated sites sustaining severe damage compared with remnant sites. This larger proportion of severely damaged individuals in revegetated sites was at least in part due to the significantly higher proportion of pioneers at these sites. The pioneer species Homalanthus novoguineensis was particularly susceptible to wind damage. The potential effects of spatial differences, such as consistent bias due to size, shape or exposure between the remnants and revegetated sites, on our results are discussed. In light of our results, we recommend that future revegetation sites include fewer pioneer species that are highly susceptible to wind damage, more pioneer species that are resistant to wind damage, and alteration of pioneer species distribution within planting matrices.     

Altered kelp (Laminariales) phlorotannins and growth under elevated carbon dioxide and ultraviolet-B treatments can influence associated intertidal food webs

Due to the importance of brown algae, such as kelp (Laminariales, Phaeophyta), within most cool nearshore environments, any direct responses of kelp to multiple global changes could alter the integrity of future coastal marine systems. Fifty-five-day manipulation of carbon dioxide (CO₂) and ultraviolet light (UVB) within outdoor sea-tanks, approximating past, present and two predicted future levels, examined the direct influences on Saccharina latissima (= Laminaria saccharina ) and Nereocystis luetkeana development and biochemistry, as well as the indirect influences on a marine herbivore ( Tegula funebralis ; Gastropoda, Mollusca) and on naturally occurring intertidal detritivores. Kelp species displayed variable directional (negative and positive growth) and scale responses to CO₂ and UVB manipulations, which was influenced by interactions. Kelp phlorotannin (phenolic) production in blade tissues was induced by elevated UVB levels, and especially enhanced (additively) by elevated CO₂, further suggesting that some actively growing kelp species are carbon limited in typical nearshore environments. Negative indirect effects upon detritivore consumers fed CO₂-manipulated kelp blade tissues were detected, however, no statistical relationships existed among UVB-treated tissues, and test herbivores did not distinguish between phlorotannin-altered CO₂: UVB-treated kelp blade tissues. Results suggest that past and future conditions differentially benefit these kelp species, which implies a potential for shifts in species abundance and community composition. Higher CO₂ conditions can indirectly impede marine decay processes delaying access to recycled trace nutrients, which may be disruptive to the seasonal regrowth of algae and/or higher trophic levels of nearshore ecosystems.