Receiver discriminability drives the evolution of complex sexual signals by sexual selection

A hallmark of sexual selection by mate choice is the evolution of exaggerated traits, such as longer tails in birds and more acoustic components in the calls of birds and frogs. Trait elaboration can be opposed by costs such as increased metabolism and greater predation risk, but cognitive processes of the receiver can also put a brake on trait elaboration. For example, according to Weber's Law traits of a fixed absolute difference will be more difficult to discriminate as the absolute magnitude increases. Here, we show that in the Emei music frog (Babina daunchina) increases in the fundamental frequency between successive notes in the male advertisement call, which increases the spectral complexity of the call, facilitates the female's ability to compare the number of notes between calls. These results suggest that female's discriminability provides the impetus to switch from enhancement of signaling magnitude (i.e., adding more notes into calls) to employing a new signal feature (i.e., increasing frequency among notes) to increase complexity. We suggest that increasing the spectral complexity of notes ameliorates some of the effects of Weber's Law, and highlights how perceptual and cognitive biases of choosers can have important influences on the evolution of courtship signals.     

Invasion of novel habitats uncouples haplo‐diplontic life cycles

Baker's Law predicts uniparental reproduction will facilitate colonization success in novel habitats. While evidence supports this prediction among colonizing plants and animals, few studies have investigated shifts in reproductive mode in haplo‐diplontic species in which both prolonged haploid and diploid stages separate meiosis and fertilization in time and space. Due to this separation, asexual reproduction can yield the dominance of one of the ploidy stages in colonizing populations. We tested for shifts in ploidy and reproductive mode across native and introduced populations of the red seaweed Gracilaria vermiculophylla. Native populations in the northwest Pacific Ocean were nearly always attached by holdfasts to hard substrata and, as is characteristic of the genus, haploid–diploid ratios were slightly diploid‐biased. In contrast, along North American and European coastlines, introduced populations nearly always floated atop soft‐sediment mudflats and were overwhelmingly dominated by diploid thalli without holdfasts. Introduced populations exhibited population genetic signals consistent with extensive vegetative fragmentation, while native populations did not. Thus, the ecological shift from attached to unattached thalli, ostensibly necessitated by the invasion of soft‐sediment habitats, correlated with shifts from sexual to asexual reproduction and slight to strong diploid bias. We extend Baker's Law by predicting other colonizing haplo‐diplontic species will show similar increases in asexuality that correlate with the dominance of one ploidy stage. Labile mating systems likely facilitate colonization success and subsequent range expansion, but for haplo‐diplontic species, the long‐term eco‐evolutionary impacts will depend on which ploidy stage is lost and the degree to which asexual reproduction is canalized.     

Is optimal foraging a realistic expectation in orb‐web spiders?

Abstract 1. Explanations for web relocation invoking optimal foraging require reliable differentiation between individual sites and overall habitat quality. We characterised natural conditions of resource variability over 20 days in artificial webs of the orb‐web spider Gasteracantha fornicata to examine this requirement. 2. Variability in catch success was high. Day‐to‐day catch success in 90% (18/20) catch sites fitted negative binomial distributions, whereas 10% fitted Poisson distributions. Considered across trap sites (overall habitat), variance in catch success increased proportionally faster than the mean (i.e. Taylor’s Power Law, variance = 0.54mean^1.764). 3. We compared the confidence intervals for the expected cumulative catch in randomly drawn sequential samples from a frequency distribution representing the overall habitat (based on the parameters for Taylor’s power law) and the frequency distribution of expected cumulative catch within each individual catch site [via randomisation based on the mean and negative binomial exponent (k)]. 4. In all cases and across all sample sizes, median values for the power to differentiate habitat and catch sites never exceeded 0.2, suggesting that principles involved in optimal foraging, if operating, must be accompanied by a very high degree of uncertainty. 5. Under conditions of high resource variability, many days must be spent in a single catch site if movement decisions are based on an ability to differentiate current catch site from overall habitat. Empirical evidence suggests this is never met. This may explain why proximal mechanisms that illicit quickly resolved behavioural responses have been more successful in describing web relocation patterns than those associated with optimal foraging.     

The Other Abortion Myth—the Failure of the Common Law

The 2006 trial of Suman Sood put criminal abortion on the public agenda for the first time in 25 years in NSW. Response to the case highlights tenacious myths about abortion law in Australia; namely that the common law “is an ass” that allows for abortion only by way of a lack of application of the law. By briefly explaining the history of abortion in Australia, I argue that the Sood case does not represent a general failure of the common law to allow abortion, nor does it support the popular myth that abortion is “technically” illegal, or that doctors who perform abortions have historically been the target of the criminal law in Australia. I show that contrary to myths promoted particularly around the 1998 Western Australian reforms, abortion has long been lawful in Australia, and the common law has merit compared to other regulatory regimes. Hence, arguments for alternative abortion regimes should not depend on myths which are shown to be unrepresentative of the political and legal situation in Australia.

《野生动物保护法》再修订: 背景、争点与建议

《野生动物保护法》的修订已纳入全国人大2020年年度立法计划。现行《野生动物保护法》虽然经过多次修改, 但仍存在野生动物保护范围较窄、监管体制不顺、执法标准不科学、法律制度不完善等问题, 不能适应新时代“健康中国”、“美丽中国”战略协同规制的新需求。全国人大常委会通过的《关于全面禁止非法野生动物交易、革除滥食野生动物陋习、切实保障人民群众生命健康的决定》, 为修订《野生动物保护法》带来了良好机遇。目前各方面对于修订《野生动物保护法》既有共识, 也有争议, 呈现出不同利益诉求与立法思维的差异性, 以及立法过程中利益选择、利益表达、利益协调的复杂性。为此, 建议《野生动物保护法》的修订在完善立法目的、合理界定保护范围、健全“黑白”名单制度和许可证制度、优化野生动物保护监管体制、完善激励机制和法律责任制度等方面认真加以研究, 为促进环境治理体系和治理能力现代化“立良法”。     

Revisiting the Freedom of Fishing and Legal Obligations on States Not Party to Regional Fisheries Management Organizations

For decades, states have cooperated through regional fisheries management organizations (RFMOs) on the conservation and management of living marine resources on the high seas. Nonmembers, or third states not bound by their decisions, have been an Achilles’ heel. In this article, the legal status of RFMO nonmembers and the freedom of fishing are examined. It is concluded that RFMO nonmembers have concrete obligations with respect to established fisheries subject to RFMO regulation.     

Vietnam's national interests and the law of the sea

This article explores the relationship between Vietnam's national interests and the international law of the sea. Vietnam's national interests in the marine sphere include defense (the maintenance of a maritime buffer); international relations (enhancing its regional position through joint development and favorable resolution of boundary and fisheries disputes); and economics (stimulating development of its maritime resources). Although ratification of the 1982 Law of the Sea Convention would be somewhat disadvantageous to Vietnam's maritime defense strategy, many provisions would promote Vietnam's interests. Moreover, ratification and implementation of the Convention would signal Vietnam's support for international law and its desire to “rejoin”; the community of Southeast Asian nations. It might also encourage resolution of its boundary disputes, thus opening new areas to resource exploration and development by foreign companies.     

Precautionary Coastal States’ Jurisdiction

Throughout the life of the 1959 Antarctic Treaty there has been considerable development in the law of the sea. Negotiated following the 1958 First United Nations Conference on the Law of the Sea, at which the customary international law concepts of the territorial sea and continental shelf were codified into treaty law, the law of the sea has since developed through state practice and most importantly through the 1982 United Nations Convention on the Law of the Sea. Whatever the merits of examining the interaction between Antarctica and the law of the sea have been in the past, there is much to suggest that the general significance of such issues is growing, especially as states seek to determine the outer limits of their continental shelf claims and in doing so determine Antarctic baselines. This article examines these issues from a general law of the sea perspective, taking into account the impact of the Antarctic Treaty while reviewing Australian practice in particular.     

Evaluation and implications of Andean potato weevil infestation sources for its management in the Andean region

The Andean potato weevil Premnotrypes suturicallus Kuschel (Coleoptera: Curculionidae) is one of the most damaging potato (Solanum spp.) pests in the Andes. The objective of this study was to get a better understanding of weevil infestation sources and its distribution in potato fields as well as on the effect of potato cropping intensity and farmers’ harvest practices on weevil infestation to provide better clues for its management. For this purpose, a methodology was developed to assess weevil field densities in potato. A Taylor’s power law indicated that 177 and 69 samples are necessary to assess low (0.5 weevils/m²) and high (5 weevils/m²) weevil densities for a moderate reliability or precision level (D = 0.5). In potato fields, overwintering weevil densities were highest at field borders with 3.5 weevils/m² at a distance of <2.5 m compared to 0.7 weevils/m² at distances >10 m from the field border. No effects of time of harvest could be detected on soil overwintering weevil densities. The quantification of the larval density per potato plant after harvest showed that fields after 2‐year potato rotations had eight times more overwintering weevils compared to 1‐year rotations. Weevil infestation sources were mainly potato fields with the highest infestation (89%) followed by olluco (Ullucus tuberosus) and oat (Avena sativa) fields having volunteer potato plants (35%). The results confirm and support previous assumptions about the importance of the cropping systems for Andean potato weevil infestation and management. The confirmation that weevils do not occur or only in neglected numbers on fallow fields supports the use of plastic barriers to effectively exclude migrating flightless adult weevils to potato fields cultivated after fallow. The distribution of overwintering weevils indicates that farmers could concentrate efforts to control adult weevils mainly to the first meters of potato fields.