Do the elongated eye stalks of Diopsid flies facilitate rival assessment?

The elongated eye span of male Diopsid flies is a sexually selected character that scales positively with body size. Previously, the duration of agonistic contests was found to increase as rival body size and eye span disparities decreased. Hence, along with its role in mate choice, eye span seems to facilitate mutual assessment of rival size. However, such results are also expected in the absence of rival assessment, when each individual persists according to its own size-dependent internal threshold. Here, we reanalyze these contests to distinguish between these two hypotheses using two measures of size: body length and eye span. Mutual assessment predicts that contest duration should increase with loser size and decrease with winner size. In contrast, our results were more consistent with self-assessment: We found a positive relationship between loser size and contest duration, whereas winner size did not affect contest duration. Thus, flies did not appear to assess the size of their rivals, indicating that the mutual assessment function of eye span elongation may be less important than previously suspected. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Scale dependency of conservation outcomes in a forest-offsetting scheme

Offset schemes help avoid or revert habitat loss through protection of existing habitat (avoided deforestation), through the restoration of degraded areas (natural regrowth), or both. The spatial scale of an offset scheme may influence which of these 2 outcomes is favored and is an important aspect of the scheme's design. However, how spatial scale influences the trade-offs between the preservation of existing habitat and restoration of degraded areas is poorly understood. We used the largest forest offset scheme in the world, which is part of the Brazilian Forest Code, to explore how implementation at different spatial scales may affect the outcome in terms of the area of avoided deforestation and area of regrowth. We employed a numerical simulation of trade between buyers (i.e., those who need to offset past deforestation) and sellers (i.e., landowners with exceeding native vegetation) in the Brazilian Amazon to estimate potential avoided deforestation and regrowth at different spatial scales of implementation. Allowing offsets over large spatial scales led to an area of avoided deforestation 12 times greater than regrowth, whereas restricting offsets to small spatial scales led to an area of regrowth twice as large as avoided deforestation. The greatest total area (avoided deforestation and regrowth combined) was conserved when the spatial scale of the scheme was small, especially in locations that were highly deforested. To maximize conservation gains from avoided deforestation and regrowth, the design of the Brazilian forest-offset scheme should focus on restricting the spatial scale in which offsets occur. Such a strategy could help ensure conservation benefits are localized and promote the recovery of degraded areas in the most threatened forest landscapes.     

Sequential analysis of aggressive interactions in the stalk-eyed fly Teleopsis dalmanni

Understanding the mechanisms and determinants of conflict resolution is of great theoretical and practical importance because the outcome of contests between males over limited resources such as mates, territories, and food has profound fitness consequences. Despite the large literature on the theory of conflict resolution, relatively few empirical studies explicitly test predictions related to contest structure for these models. In sexually dimorphic species of stalk-eyed flies (Diopsidae), males engage in characteristic aggressive interactions over both females and food resources. We used sequential analysis of aggressive interactions between dyads of male stalk-eyed flies to investigate patterns of escalation, behavioral matching, and physical contact in order to distinguish between three common models of conflict resolution: the sequential assessment model, the cumulative assessment model, and the energetic war of attrition. Stalk-eyed flies were shown to engage in both low- and high-intensity behaviors during interactions with patterns of escalation and no de-escalation. Aggressive interactions did not demonstrate behavioral matching between winners and losers. Stalk-eyed flies also escalated to behaviors that included physical contact without injuries. Our results provide support for the sequential assessment model based on patterns of escalation with no de-escalation, behavioral mismatching, and behaviors which include physical contact but no injuries.     

Decoupling fragmentation from habitat loss for spiders in patchy agricultural landscapes

Habitat loss reduces species diversity, but the effect of habitat fragmentation on number of species is less clear because fragmentation generally accompanies loss of habitat. We compared four methods that aim to decouple the effects of fragmentation from the effects of habitat loss. Two methods are based on species-area relations, one on Fisher's alpha index of diversity, and one on plots of cumulative number of species detected against cumulative area sampled. We used these methods to analyze the species diversity of spiders in 2, 3.2 × 4 km agricultural landscapes in Southern Judea Lowlands, Israel. Spider diversity increased as fragmentation increased with all four methods, probably not because of the additive within-patch processes, such as edge effect and heterogeneity. The positive relation between fragmentation and species diversity might reflect that most species can disperse through the fields during the wheat-growing season. We suggest that if a given area was designated for the conservation of spiders in Southern Judea Lowlands, Israel, a set of several small patches may maximize species diversity over time.     

Short-rib polydactyly syndrome (SRPS) type III diagnosed during routine prenatal ultrasonographic screening. A case report

The prenatal diagnosis of skeletal dysplasias is often initiated by the finding of a shortened extremity during a routine sonographic examination. Second-trimester diagnosis of these anomalies allows the couple to consider the option of terminating a pregnancy when a lethal anomaly is detected. A 21-year-old Bedouin woman underwent routine ultrasonographic screening at 20 weeks' gestation. Severe micromelia, a narrow thorax with shortened ribs, and postaxial polydactyly were detected. The patient delivered a male dwarf at 20 weeks' gestation following prostaglandin induction of labour for a diagnosis of short-rib polydactyly syndrome type III. The prenatal ultrasonographic diagnosis of short-rib polydactyly syndrome type III was made at 20 weeks' gestation, allowing termination of the pregnancy. A proper sonographic approach to skeletal dysplasias allows both early detection and differentiation between lethal and non-lethal anomalies.     

Variation in sperm morphometry and sperm competition among barn swallow (Hirundo rustica) populations

Spermatozoa vary greatly in size and shape among species across the animal kingdom. Postcopulatory sexual selection is thought to be the major evolutionary force driving this diversity. In contrast, less is known about how sperm size varies among populations of the same species. Here, we investigate geographic variation in sperm size in barn swallows Hirundo rustica, a socially monogamous passerine with a wide Holarctic breeding distribution. We included samples from seven populations and three subspecies: five populations of ssp. rustica in Europe (Czech, Italy, Norway, Spain, and Ukraine), one population of ssp. transitiva in Israel, and one population of ssp. erythrogaster in Canada. All sperm traits (head length, midpiece length, tail length, and total length) varied significantly among populations. The variation among the European rustica populations was much lower than the differences among subspecies, indicating that sperm traits reflect phylogenetic distance. We also performed a test of the relationship between the coefficient of between-male variation in total sperm length and extrapair paternity levels across different populations within a species. Recent studies have found a strong negative relationship between sperm size variation and extrapair paternity among species. Here, we show a similar negative relationship among six barn swallow populations, which suggests that the variance in male sperm length in a population is shaped by the strength of stabilizing postcopulatory sexual selection.     

Persistence of individually distinctive display patterns in fatigued side-blotched lizards ( Uta stansburiana)

Iguanian lizards perform conspicuous species-typical push-up displays, which are used in territory advertisement, threat, and courtship contexts. Subtle individually distinctive differences in push-up characteristics have been suggested to play a role in the recognition of social partners. However, if the structure of push-ups is responsive to changing physiological states then their capacity to promote recognition may be limited. The current study evaluated whether the push-ups performed while in an experimentally imposed state of fatigue by male side-blotched lizards (Uta stansburiana), retain the individually distinctive characteristics apparent in rested lizards. We found repeatable among-individual differences in the duration and the relative height of push-up components. Repeatability values did not change consistently between the rested and fatigued conditions, nor when both conditions were pooled, indicating that these push-up characteristics do not change with fatigue. Similarly, discriminant functions that were generated using push-ups from one state assigned push-ups performed in an alternate state to the correct individuals. Furthermore, when analyzed independently of individual identity, the values of display parameters examined in the current study did not change significantly between states, and discriminant function analysis could not reliably classify push-ups to the correct state. Taken together the results show that individually distinctive push-up characteristics are robust to effects of fatigue, consistent with their suggested role in social recognition. In the future, video playback experiments can test whether lizards utilize the signature-like characteristics of push-ups to discriminate among individuals.Communicated by T. Czeschlik