The woolly flying squirrel and gliding: does size matter?

The woolly flying squirrelEupetaurus cinereus! Thomas, 1888 is the longest sciurid and most massive mammalian glider in the world. Because of this, there has been some question about the squirrel’s gliding ability. I document three glide events performed by this species. These glide events, coupled with comparisons of glide ratios, ponderal ratios, and a log-log plot of head + body length versus body mass with other flying squirrels, demonstrates that the woolly flying squirrel, despite its size, is a capable glider and is no more robust than other flying squirrels. Predation attempts that were observed during glide events are discussed within an evolutionary context.     

Benign prostatic hyperplasia: does prostate size matter?

Recent studies and analyses have confirmed that baseline prostate volume is related to progression of benign prostatic hyperplasia (BPH) as well as to negative outcomes related to BPH, such as acute urinary retention (AUR) and need for surgery, and can also predict response to therapy. Other investigations have determined that prostate-specific antigen (PSA) level has good predictive value for assessing prostate volume. Strong evidence exists that baseline serum PSA level, like baseline prostate volume, predicts future prostate growth. Randomized placebo-controlled finasteride trials have shown that men with larger prostate volumes and higher PSA levels experience a clinically significant response to therapy compared with those with smaller prostate volumes and lower PSA levels. It has also been demonstrated that men with larger prostate glands and higher PSA levels are at increased risk for AUR and BPH-related surgery but that finasteride reduces these risks. Moreover, doxazosin and finasteride, alone and in combination, have been shown to significantly reduce BPH clinical progression.     

Measuring diversity of endophytic fungi in leaf fragments: does size matter?

Endophytic fungi inhabit living plant tissues without causing disease symptoms. Although abundant, the extent of their contribution to fungal biodiversity remains unclear. Since endophytic fungi are poorly known, especially in the tropics, current estimates of fungal species are probably conservative. Here we tested strategies for sampling endophytic fungi in tropical plants. We compared the number of fungi isolated from 400 mm2 leaf pieces that were divided into increasingly small fragments. Leaf pieces were surface-sterilized, cut into fragments and plated on culture media. For a given area, cutting leaf pieces into smaller fragments significantly increased the number of fungal morphospecies recovered. There was a strong linear relationship between size of fragments and number of fungi isolated. By extrapolation, an estimated 16 +/- 3 fungi could be recovered from a 2 x 2 cm leaf piece, using infinitely small fragments. This represents a large part of the fungal diversity estimated to exist in leaf endophytes in a population. We conclude that reducing the size and increasing the number of leaf fragments will increase the number of fungal species isolated. This strategy will help to estimate real values of endophytic fungal diversity.     

Genetics of recent habitat contraction and reduction in population size: does isolation by distance matter?

Fragmentation and loss of natural habitats are recognized as major threats to contemporary flora and fauna. Detecting past or current reductions in population size is therefore a major aim in conservation genetics. Statistical methods developed to this purpose have tended to ignore the effects of spatial population structure. However in many species, individual dispersal is restricted in space and fine-scale spatial structure such as isolation by distance (IBD) is commonly observed in continuous populations. Using a simulation-based approach, we investigated how comparative and single-point methods, traditionally used in a Wright-Fisher (WF) population context for detecting population size reduction, behave for IBD populations. We found that a complex 'quartet' of factors was acting that includes restricted dispersal, population size (i.e. habitat size), demographic history, and sampling scale. After habitat reduction, IBD populations were characterized by a stronger inertia in the loss of genetic diversity than WF populations. This inertia increases with the strength of IBD, and decreases when the sampling scale increases. Depending on the method used to detect a population size reduction, a local sampling can be more informative than a sample scaled to habitat size or vice versa. However, IBD structure led in numerous cases to incorrect inferences on population demographic history. The reanalysis of a real microsatellite data set of skink populations from fragmented and intact rainforest habitats confirmed most of our simulation results.     

Tree-ring growth and intra-annual density fluctuations of Pinus pinaster responses to climate: does size matter?

Dendroclimatology generally assumes that climate–growth relationships are age and size independent. However, there is evidence that climate response can be unstable across different age/size classes. In addition, the occurrence of some anatomical features, such as intra-annual density fluctuations (IADFs), is age dependent. The present study investigates whether the climate–growth responses and the occurrence of IADFs in an even-aged stand of Pinus pinaster Ait., growing under Mediterranean climate, are also size-dependent. We randomly selected 60 P. pinaster trees falling within two stem diameter classes: small (<27 cm) and large (>35 cm). Tree rings were crossdated, measured and IADFs identified according to their position within the ring. The residual chronologies of both size classes were strongly correlated, suggesting a common signal. In fact, similar growth–climate relationships were observed in large and small trees. The frequency of IADFs was higher in large than in small trees, suggesting that IADFs were more likely to occur in wider rings of fast-growing trees. In both size classes, most of the IADFs were found in latewood. Latewood IADFs were triggered by the combination of dry June, wet September, and warm December, whereas IADFs located at the end of earlywood were triggered by previous winter precipitation and favorable conditions before summer (high precipitation for large trees and lower temperature for small trees). Our results suggest that IADFs can be a mechanism used at the individual level for adaptation to drought in P. pinaster. The climatic signal of IADFs between earlywood and latewood was mediated by stem size suggesting that future tree-ring studies should include trees stratified by size to better estimate the sensitivity of IADFs to climate.     

Contest behavior in territorial male butterflies: does size matter?

Although intrasexual contests generally favor bigger or stronger individuals, the relevance of body size to war of attrition-typedisputes between weaponless animals such as butterflies isunclear. In this study I aimed to investigate the significanceof size in this context by studying territorial contests inHypolimnas bolina (L.), a species that exhibits consistentseasonal plasticity in body size. In this species adult ageis positively correlated with large size in spring but withsmall size in autumn. This shift allowed independent evaluationof the relevance of each variable (size and age) to intrasexualcontest success. Observation of a population of marked individualsindicated that only age appeared important, with the winnersof pair-wise contests significantly older than losers in both seasons, and with contests lasting longer when the age differencebetween the combatants was small. Age was also linked to residency;residents won 99% of all contests. This study suggests thatsize does not matter in these aerial disputes, but age andresidency do. It is not yet possible to determine whether olderbutterflies are intrinsically better competitors, or whether they simply have greater opportunity to find a vacant territory.     

Sex allocation and nestling survival in a dimorphic raptor: does size matter?

Fisher's theory predicts equal sex ratios at the end of parentalcare if the costs and benefits associated with raising eachsex of offspring are equal. In raptors, which display variousdegrees of reversed sexual size dimorphism (RSD; females thelarger sex), sex ratios biased in favor of smaller males areonly infrequently reported. This suggests that offspring ofeach sex may confer different fitness advantages to parents.We examined the relative returns associated with raising eachsex of offspring of the brown falcon Falco berigora, a medium-sizedfalcon exhibiting RSD (males approximately 75% of female bodymass) and subsequent sex ratios. Female nestlings hatched eitherfirst or second did not receive more food nor did they hatchfrom larger eggs or remain dependent on parents for longer periodsthan male offspring from these hatch orders. Together with previousstudies this result indicates that even in markedly dimorphicspecies, the required investment to raise the larger sex islikely to be less than that predicted by body size differencesalone. Moreover, among last-hatched nestlings, both sexes faceda reduced food allocation and suffered a slower growth rateand thus final body size, with a concurrent increased probabilityof mortality. For last-hatched females the reduction in foodallocation was more marked, with complete mortality of all last-hatchedfemale nestlings monitored in this study. Once independent,males of any size but only larger females are likely to be recruitedinto the breeding population. The sex-biased food allocationamong last-hatched offspring favoring males thus reflects therelative returns to parents in raising a small member of eachsex.     

The trophic state ‘chain of relationships’ in ponds: does size matter?

In contrast to shallow lakes, factors affecting trophic state in ponds are not well described, and may include unique effects related to pond size. We examined the interdependence of ambient N and P, phytoplankton biomass, light penetration and stratification in 13 ponds of varying area and mean depth in Chester County, PA (USA) during March, May and July of 2002. Seven of the ponds had primarily residential watersheds, and six were farm ponds. The ponds were all eutrophic or hypereutrophic based on Carlsons Trophic State Index, but varied widely in nutrient content (from 20 to 179 g total P/L and from 683 to 3895 g total N/L) and size (surface areas from 0.1 to 1.7 ha, mean depths from 0.6 to 1.8 m). Although total N (TN) typically declined while total P (TP) rose from March to July, the ratio TN/TP remained sufficiently high that algal growth was probably limited by P during the study period. Phytoplankton biomass (as chlorophyll-a) was positively correlated with TP and negatively correlated with Secchi depth on all three sampling dates. Despite their shallow nature, the ponds were frequently stratified with near-anoxic hypolimnia later in the study period; mixing depth was greater in ponds with greater light penetration. Residual variation in chlorophyll-a unexplained by TP, and in Secchi depth unexplained by chlorophyll-a, was related to either mean depth or surface area, suggesting that trophic state in ponds may be controlled differently than in much larger, shallow lakes.     

Costs of secondary parasitism in the facultative hyperparasitoid Pachycrepoideus dubius: does host size matter?

Although hyperparasitism frequently occur in parasitic insects, many aspects of this strategy remain unknown. We investigated possible fitness costs of hyperparasitism as influenced by host size. Our study was conducted with the facultative hyperparasitoid Pachycrepoideus dubius Ashmead (Hymenoptera: Pteromalidae), which parasitizes host species differing greatly in size. We compared some fitness traits (level of successful parasitism, development time, sex ratio and offspring size) of P. dubius developing on large secondary/primary (Delia radicum L. (Diptera: Anthomyiidae)/Trybliographa rapae Westwood (Hymenoptera: Figitidae)) or small secondary/primary host species (Drosophila melanogaster L./Asobara tabida Nees (Hymenoptera: Braconidae)). In no-choice and choice experiments, P. dubius was able to develop on different stages of T. rapae (L2 (endophagous), L4 (ectophagous), and pupae) but that it preferred to parasitize unparasitized D. radicum pupae over pupae parasitized by T. rapae. Furthermore, in P. dubius, hyperparasitism was associated with fitness costs (lower level of successful parasitism, smaller adult size) and these costs were greater on the smallest host complex. We hypothesize that the size of D. melanogaster pupae parasitized by A. tabida may be close to the suboptimal host size for P. dubius beneath which the costs of hyperparasitism make this strategy nonadaptive. Hyperparasitism in terms of trade-offs between host quality and abundance of competitors is discussed.     

Does size matter?

For 40 years, the debate has raged. Do mammalian cells monitor cell size when deciding whether to divide? More recent models suggest an indirect solution, but the field is far from reaching a final verdict.     

Cell size: a matter of life or death?

Proper growth and development of multicellular organisms require the tight regulation of cell growth, cell division and cell death. A recent study has identified a novel regulatory link between two of these processes: cell growth and cell death.     

Insect declines and agroecosystems: does light pollution matter?

Drastic declines in insect populations, ‘Ecological Armageddon’, have recently gained increased attention in the scientific community, and are commonly considered to be the consequence of large‐scale factors such as land‐use changes, use of pesticides, climate change and habitat fragmentation. Artificial light at night (ALAN), a pervasive global change that strongly impacts insects, remains, however, infrequently recognised as a potential contributor to the observed declines. Here, we provide a summary of recent evidence of impacts of ALAN on insects and discuss how these impacts can drive declines in insect populations in light‐polluted areas. ALAN can increase overall environmental pressure on insect populations, and this is particularly important in agroecosystems where insect communities provide important ecosystem services (such as natural pest control, pollination, conservation of soil structure and fertility and nutrient cycling), and are already under considerable environmental pressure. We discuss how changes in insect populations driven by ALAN and ALAN itself may hinder these services to influence crop production and biodiversity in agricultural landscapes. Understanding the contribution of ALAN and other factors to the decline of insects is an important step towards mitigation and the recovery of the insect fauna in our landscapes. In future studies, the role of increased nocturnal illumination also needs to be examined as a possible causal factor of insect declines in the ongoing ‘Ecological Armageddon’, along with the more commonly examined factors. Given the large scale of agricultural land use and the potential of ALAN to indirectly and directly impact crop production and biodiversity, a better understanding of effects of ALAN in agroecosystems is urgently needed.     

Predator recognition and nest defence by Carolina Wrens Thryothorus ludovicianus in urban and rural environments: does experience matter?

Capsule: Carolina Wrens Thryothorus ludovicianus in urban and rural environments responded most intensely to predators common to their environments.

Aims: To determine the role of experience in predator recognition and response among Carolina Wrens. We predicted that wrens in the urban environment, where domestic cats are common, would respond more intensely to mounts of cats than snakes (a less common nest predator) placed near their nests. In the rural (forested) environment, we predicted a greater response to snakes than cats, because snakes are the more common predator in that environment.

Methods: We placed mounted specimens of a snake and a cat near wren nests at the late nestling stage and quantified responses. We used a Rock Dove Columba livia mount as the control because it is a non-threatening species to the nestlings, and should be familiar to the wrens.

Results: Carolina Wrens in the urban area responded most intensively to the cat mounts, whereas those in the rural environment responded more to the snake, with indications of innate predator recognition and defence. Cats were more common in the urban environment. Wrens used different alarm calls in the two habitats, but further study is needed to understand the significance of this variation.

Conclusions: Birds may have the ability to adapt their responses to local predators, both native and non-native, which may be especially important for their success in urbanized habitats.     

Sex‐specific foraging behaviour in tropical boobies: does size matter?

Sex differences in the foraging behaviour of adults have been observed in a number of sexually size-dimorphic birds, and the usual inference has been that these sex-specific differences are driven primarily by differences in body size. An alternative explanation is that foraging differences result from sex differences unrelated to size, such as sex-specific nutritional requirements. To examine these alternative hypotheses, the foraging behaviour of parents was compared between two sympatric and congeneric species of seabird, the Brown Booby Sula leucogaster , which is highly sexually size-dimorphic (females 38% larger) and the Red-footed Booby S. sula , in which sex differences in body size are less marked (females 15% larger). Using temperature and depth loggers, we found that there were highly significant differences in the foraging trip durations and diving behaviour of male and female Brown Boobies. These sex differences were less marked in Red-footed Boobies. Thus, our interspecies comparison revealed that the magnitude of the difference between the sexes matched the sexual size dimorphism of the species, providing support for the size hypothesis.     

Biological effects of radiofrequency fields: does modulation matter?

This commentary considers modulation as a factor of potential biological importance in assessment of risk of radiofrequency (RF) energy emitted by communications systems and other technologies. Modulation introduces a spread of frequencies into a carrier waveform, but in nearly all cases this spread is small compared to the frequency of the carrier. Consequently, any nonthermal (field-dependent) biological effects related to modulation must result from interaction mechanisms that are fast enough to produce a response at radiofrequencies. Despite considerable speculation, no such mechanisms have been established. While a variety of modulation-dependent biological effects of RF energy have been reported, few such effects have been independently confirmed. Some widely discussed effects, for example a reported modulation-dependent effect of RF fields on the efflux of calcium from brain tissue, remain controversial with no established biological significance. The lack of understanding of the mechanisms underlying such effects prevents any assessment of their significance for communications signals with complex modulation characteristics. Future research should be directed at confirmation and mechanistic understanding of reported biological effects related to modulation. While modulation should be considered in the design of risk studies involving communications-type signals, it should not compromise other aspects of good study design, such as maintaining adequate statistical power and identifying dose-response relationships.