Is stomatal conductance optimized over both time and space in plant crowns? A field test in grapevine (Vitis vinifera)

Crown carbon gain is maximized for a given total water loss if stomatal conductance (g_s) varies such that the marginal carbon product of water (?A/?E) remains invariant both over time and among leaves in a plant crown, provided the curvature of assimilation rate (A) versus transpiration rate (E) is negative. We tested this prediction across distinct crown positions in situ for the first time by parameterizing a biophysical model across 14 positions in four grapevine crowns (Vitis vinifera), computing optimal patterns of g_s and E over a day and comparing these to the observed patterns. Observed water use was higher than optimal for leaves in the crown interior, but lower than optimal in most other positions. Crown carbon gain was 18% lower under measured g_s than under optimal g_s. Positive curvature occurred in 39.6% of cases due to low boundary layer conductance (g_bw), and optimal g_s was zero in 11% of cases because ?A/?E was below the target value at all g_s. Some conclusions changed if we assumed infinite g_bw, but optimal and measured E still diverged systematically in time and space. We conclude that the theory's spatial dimension and assumption of positive curvature require further experimental testing.     

The effect of Tropical Cyclone Larry on tooth‐billed bowerbird Scenopoeetes dentirostris court attendance and decoration

Abstract The effect of Severe Tropical Cyclone Larry on tooth‐billed bowerbird court attendance and decoration was assessed for 32 courts located on the southern Atherton Tablelands. Numbers of active courts and the number of leaves on courts were compared with the two previous court attendance seasons. Compared with the 2004/2005 and 2005/2006 seasons, when court attendance was well established by mid‐September, tooth‐billed bowerbirds commenced court attendance late in the 2006/2007 season that followed Cyclone Larry. There were no courts active in mid‐September, and few were active in the first week of October. Twenty‐five percent fewer courts were active over the course of the 2006/2007 season than in the 2005/2006 season. For most of the 2006/2007 season, the average number of leaves on courts was significantly lower than in the previous two seasons. The 2006/2007 tooth‐billed bowerbird court attendance season appears to have been affected by direct disturbance to court sites and by the fruit shortage that followed the cyclone.     

The impact of Tropical Cyclone Larry on bird communities in fragments of the endangered rainforest Type 5b

Abstract Bird surveys were conducted to assess the impact of a severe cyclone on bird communities in three fragments of the endangered rainforest Type 5b on the Atherton Tablelands of far north Queensland. Bird communities were surveyed using timed area searches in three sites in each of the three fragments and were undertaken prior to and following Tropical Cyclone Larry. Cyclone Larry caused short‐term changes in the abundance of some species of birds in Type 5b rainforest fragments. Two weeks after the storm, in two of three fragments surveyed, abundance of the frugivorous wompoo fruit‐dove (Ptilinopus magnificus) and figbird (Sphecotheres viridis) had decreased while the omnivorous Macleay's honeyeater (Xanthotis macleayana) and Lewin's honeyeater (Meliphaga lewinii) decreased in abundance in all three locations. Most insectivorous species increased in some sites and decreased in others following Cyclone Larry. Rapid recovery of bird communities to approximately their pre‐cyclone state after only 7 months appeared to reflect the capacity of species to either modify their foraging behaviour, switch foods, or to move within or between fragments or to other food sources in the landscape.     

Female‐biased size dimorphism in a diapausing caddisfly,Mesophylax aspersus: effect of fecundity and natural and sexual selection

1. The effect of mating success, female fecundity and survival probability associated with intra‐sex variation in body size was studied in Mesophylax aspersus, a caddisfly species with female‐biased sexual size dimorphism, which inhabits temporary streams and aestivates in caves. Adults of this species do not feed and females have to mature eggs during aestivation. 2. Thus, females of larger size should have a fitness advantage because they can harbour more energy reserves that could influence fecundity and probability of survival until reproduction. In contrast, males of smaller size might have competitive advantages over others in mating success. 3. These hypotheses were tested by comparing the sex ratio and body size of individuals captured before and after the aestivation period. The associations between body size and female fecundity, and between mating success and body size of males, were explored under laboratory conditions. 4. During the aestivation period, the sex ratio changed from 1 : 1 to male biased (4 : 1), and a directional selection on body size was detected for females but not for males. Moreover, larger clutches were laid by females of larger size. Finally, differences in mating success between small and large males were not detected. These results suggest that natural selection (i.e. the differential mortality of females associated with body size) together with possible fecundity advantages, are important factors responsible of the sexual size dimorphism of M. aspersus. 5. These results highlight the importance of taking into account mechanisms other than those traditionally used to explain sexual dimorphism. Natural selection acting on sources of variation, such as survival, may be as important as fecundity and sexual selection in driving the evolution of sexual size dimorphism.     

Diffusion of TCE Through Soil-Bentonite Slurry Walls

Diffusion experiments performed using both a dissolved solution of trichloroethylene (TCE) and a pool of free phase TCE adjacent to a simulated soil-bentonite (SB) wall are described. These tests examine a multi-layer system that includes both contaminated sand and a SB barrier. Results obtained from experiments with dissolved TCE as the primary source are shown to be consistent with those obtained with free-phase TCE as the source of contaminant. Diffusion and sorption coefficients of a soil-bentonite slurry wall are reported to be 3.5 × 10^?10 m ² /s and 0 cm ³ /g, respectively. These diffusion and sorption coefficients were used to evaluate the effectiveness of a hypothetical SB slurry wall located adjacent to a TCE spill.     

Distribution,host specificity,and the potential for cryptic speciation in hoverfly Microdon myrmicae (Diptera: Syrphidae), a social parasite of Myrmica ants

1. In 2002 Microdon myrmicae, a social parasite of Myrmica ants, was taxonomically separated from Microdon mutabilis. The original study in the U.K. found Microdon myrmicae to be specific to one ant species, Myrmica scabrinodis, yet it became apparent that the range of Microdon myrmicae includes at least the western Palaearctic. 2. Current knowledge of the European distributions of both Microdon myrmicae and Microdon mutabilis in Europe is reviewed. Also, in detailed studies of two Polish populations, Microdon myrmicae was found to survive equally well with two Myrmica ant species. We examine, however, the possibility that this reflects the presence of two separate Microdon species, each connected to one species of Myrmica. 3. Forty populations of Microdon myrmicae and 37 populations of Microdon mutabilis are currently known in Europe. All the populations in central and southern Europe that were visited after the separation of the two species were identified as Microdon myrmicae, while Microdon mutabilis’ recognised range is now restricted to the British Isles and Scandinavia. Myrmica scabrinodis was found to host Microdon myrmicae in 26 out of 31 populations investigated. Four other Myrmica species were identified to the host Microdon myrmicae: Myrmica gallienii (eight populations), Myrmica rubra (four), Myrmica vandeli (one), and Myrmica sabuleti (one). Microdon myrmicae occurs in waterlogged grassland habitats, mainly of the ‘Molinietum’ type, resulting in a patchy distribution relative to its host ants. 4. In two populations Myrmica scabrinodis and Myrmica gallienii are both abundant and rear Microdon myrmicae in equal proportions. Microdon myrmicae pupae from Myrmica gallienii nests were heavier and the anterior respiratory organs were of significantly different shape. In contrast, the comparisons of Microdon myrmicae pupae among all other populations showed no significant differences, suggesting only one species throughout the European range.