Host responses to interspecific brood parasitism: a by-product of adaptations to conspecific parasitism?

Background: Why have birds evolved the ability to reject eggs? Typically, foreign egg discrimination is interpreted as evidence that interspecific brood parasitism (IP) has selected for the host’s ability to recognize and eliminate foreign eggs. Fewer studies explore the alternative hypothesis that rejection of interspecific eggs is a by-product of host defenses, evolved against conspecific parasitism (CP). We performed a large scale study with replication across taxa (two congeneric Turdus thrushes), space (populations), time (breeding seasons), and treatments (three types of experimental eggs), using a consistent design of egg rejection experiments (n = 1057 nests; including controls), in areas with potential IP either present (Europe; native populations) or absent (New Zealand; introduced populations). These comparisons benefited from the known length of allopatry (one and a half centuries), with no gene flow between native and introduced populations, which is rarely available in host-parasite systems. Results: Hosts rejected CP at unusually high rates for passerines (up to 60%). CP rejection rates were higher in populations with higher conspecific breeding densities and no risks of IP, supporting the CP hypothesis. IP rejection rates did not covary geographically with IP risk, contradicting the IP hypothesis. High egg rejection rates were maintained in the relatively long-term isolation from IP despite non-trivial rejection costs and errors. Conclusions: These egg rejection patterns, combined with recent findings that these thrushes are currently unsuitable hosts of the obligate parasitic common cuckoo (Cuculus canorus), are in agreement with the hypothesis that the rejection of IP is a by-product of fine-tuned egg discrimination evolved due to CP. Our study highlights the importance of considering both IP and CP simultaneously as potential drivers in the evolution of egg discrimination, and illustrates how populations introduced to novel ecological contexts can provide critical insights into brood parasite-host coevolution.Peter Samas, Mark E Hauber, Phillip Cassey and Tomas Gri

The evolutionary causes of egg rejection in European thrushes (Turdus spp.): a reply to M. Soler

Peter Samas, Mark E Hauber, Phillip Cassey, and Tomas Gri

Egg rejection in blackbirds Turdus merula: a by-product of conspecific parasitism or successful resistance against interspecific brood parasites?

Traditional theory assumes that egg recognition and rejection abilities arise as a response against interspecific brood parasitism (IBP). However, rejection also appears in some species that are currently not exploited by interspecific parasites, such as Turdus thrushes. Recent evidences suggest that rejection abilities evolved in these species as a response to conspecific brood parasitism (CBP). To test these two alternative hypotheses, we performed an experimental study by parasitizing nests of the common blackbird (Turdus merula) with conspecifics or heterospecific eggs under different risk of parasitism (presence of interspecific or conspecific parasites near the nest). Common blackbird is a potential host of the common cuckoo (Cuculus canorus) but suffers low levels of CBP too. Results: We found that blackbirds were able to recognize and eject heterospecific eggs at high rates whereas most of conspecifics eggs were not recognized and, therefore, accepted. Ejection rates of conspecific eggs did not exceed 13 %, even in situations of high risk of CBP (blackbird female placed near the nest), which contradict the main prediction derived from the CBP hypothesis. Conversely, ejection rates of experimental eggs simulating IBP were much higher (80–100 %). Furthermore, female blackbirds were more aggressive towards cuckoos than towards blackbird dummies. Conclusions: Our results considered together support the IBP hypothesis, indicating that recognition and rejection of parasitic eggs in blackbirds have probably evolved due to previous cuckoo parasitism. The current absence of IBP in blackbirds may be due to the highly efficient rejection abilities in this species. Thus, these abilities have been retained in absence of brood parasitism as a consequence of the low costs involved for blackbirds, resulting in a successful resistance against interspecific brood parasitism.Financial support has been provided by the Consejería Economía, Innovación, Ciencia y Empleo. Junta de Andalucia (research project CVI-6653)

Cigarette butts form a perceptually cryptic component of song thrush (Turdus philomelos) nests

Bird nests often contain objects produced and manipulated by other animals, including human rubbish. The function, if any, of these items remains unclear, and it is unknown whether they might serve a signalling role to increase the conspicuousness of the nest lining or contribute to its crypsis. We located several nests of the introduced song thrush (Turdus philomelos) in New Zealand containing discarded cigarette butts. These items were embedded into the dried mud-matrix of the nest and appeared visually inconspicuous to the human observer. However, human and avian visual sensitivities are dramatically different. We used full-spectrum reflectance spectrophotometry, combined with perceptual modelling of the avian visual system to assess the contrast between mud lining, garbage, and the colours of thrush eggs. Our analyses confirmed that, when perceived by birds, cigarette butts were similar in appearance to the nest lining and showed sharp contrast with the eggs. We suggest that cigarette butts form an opportunistic structural component of the song thrush nest. It remains to be determined whether human-made objects in song thrush nests serve anti-predator or an olfactory signalling function. This study illustrates the application of avian perceptual modelling to test signalling based hypotheses for the extended phenotype of birds, including nest architecture.Branislav Igic, Phillip Cassey, Peter Samas, Tomas Grim and Mark E. Haube

Egg rejection behavior and clutch characteristics of the European Greenfinch introduced to New Zealand

Animal populations, with a known history of introduction events, provide opportunities to study the dynamics of how rapid shifts in ecological context affect behavioral (e.g., responses to brood parasitism) and life-history (e.g., clutch and egg parameters) traits. We studied the European Greenfinch (Carduelis chloris) introduced to New Zealand, regarding foreign-egg rejection behaviors and also compared their clutch characteristics with data from the source populations in the United Kingdom. Although previously this species had been considered an unsuitable host for the Common Cuckoo (Cuculus canorus), and not impacted by selection pressure associated with brood parasitism, we found that Greenfinches in our study population were able to eject experimental eggs at low frequencies. In contrast, nest desertion rates were similar in experimentally parasitized and control unmanipulated nests, implying that nest desertion is not an antiparasite adaptation in this species. Contrary to previous studies, we did not find significant differences in clutch and egg sizes between introduced and source populations. This study emphasizes (1) the importance of using control treatments in studies of host responses to experimental parasitism, (2) including apparently unsuitable hosts of brood parasites, and (3) meta-replicating prior studies to further the process of gaining and validating scientific knowledge.Peter Samaš, Lenka Polačiková, Mark E. Hauber, Phillip Cassey, Tomáš Gri

Two Routes to 4‑Fluorobenzisoxazol-3-one in the Synthesis of a 5‑HT₄ Partial Agonist

A potent 5-HT₄ partial agonist, <b>1</b> (PF-04995274), targeted for the treatment of Alzheimer’s disease and cognitive impairment, has been prepared on a multi-kilogram scale. The initial synthetic route, that proceeded through a 4-substituted 3-hydroxybenzisoxazole core, gave an undesired benzoxazolinone through a Lossen-type rearrangement. Route scouting led to two new robust routes to the desired 4-substituted core. Process development led to the efficient assembly of the API on a pilot plant scale under process-friendly conditions with enhanced throughput. In addition, crystallization of a hemicitrate salt of the API with pharmaceutically beneficial properties was developed to enable progression of clinical studies

Алгоритм расчета необходимого продовольственного потенциала региона и его реализация

У роботі викладено необхідність розробки стратегії забезпечення населення продовольством на основі аналізу сучасного економічного стану сільськогосподарського виробництва та випуску продукції в регіоні.The need for the strategy of the population provision with food considering modern economic situation with agricultural production is shown. Analysis of food production in the region is conducted