Haematobia irritans parasitism of F1 yak × beef cattle (Bos grunniens × Bos taurus) hybrids

The horn fly Haematobia irritans (Diptera: Muscidae) is a blood obligate ectoparasite of bovids that causes annual losses to the U.S. beef cattle industry of over US$1.75 billion. Climate warming, the anthropogenic dispersion of bovids and the cross‐breeding of beef cattle with other bovid species may facilitate novel horn fly–host interactions. In particular, hybridizing yaks [Bos grunniens (Artiodactyla: Bovidae)] with beef cows (Bos taurus) for heterosis and carcass improvements may increase the exposure of yak × beef hybrids to horn flies. The present paper reports on the collection of digital images of commingled beef heifers (n = 12) and F1 yak × beef hybrid bovids (heifers, n = 7; steers, n = 5) near Laramie, Wyoming (～ 2200 m a.s.l.) in 2018. The total numbers of horn flies on beef heifers and F1 yak × beef heifers [mean ± standard error (SE): 88 ± 13 and 70 ± 17, respectively] did not differ significantly; however, F1 yak × beef steers had greater total horn fly abundance (mean ± SE: 159 ± 39) than female bovids. The present report of this experiment is the first such report in the literature and suggests that F1 yak × beef bovids are as susceptible as cattle to horn fly parasitism. Therefore, similar monitoring and treatment practices should be adopted by veterinarians, entomologists and producers.     

Linking micromorphism,brooding, and hermaphroditism in brachiopods: Insights from Caribbean Argyrotheca (Brachiopoda)

In extant brachiopods, parental brooding of the larvae occurs exclusively within Rhynchonelliformea. Methods of larval protection range from simple retention of the larvae within the mantle cavity, to sophisticated brood care within highly specialized brood pouches found in Argyrotheca and Joania (Terebratulida, Megathyridoidea), Gwynia (Terebratulida, Gwynioidea), and all Thecideoidea (Thecideida). Previous studies on the reproductive biology of Argyrotheca yielded contrasting results on the epithelial origin of the brood pouches in this genus. Here, representatives of different species of Argyrotheca from the Belize Barrier Reef were examined using histological section series. Brood pouches of four species, A. cf. schrammi and Argyrotheca sp. 1–3, are of the same basic structure, formed by invaginations of the anterior body wall and connected to the visceral cavity via the metanephridia. The same four species are simultaneously hermaphroditic, suggesting that fertilization is achieved, at least partly, through selfing. One species, Argyrotheca rubrocostata, differs significantly from all others as it has no brood pouch and gonochoric gonads. Thus, the presence of brood pouches and simultaneous hermaphroditism are concluded to be correlated within Megathyridoidea and proposed to be homologous traits of Joania and several but not all species of Argyrotheca, questioning the monophyletic status of both genera. In contrast to the brood pouches of Thecideoidea, lophophoral epithelium is not involved in the formation of the pouches of Argyrotheca and Joania. Therefore, megathyridoid and thecideoid brood pouches are not homologous but evolved independently within rhynchonelliform brachiopods. All brachiopods with brood pouches share a micromorphic form and a short life span, limiting the space and time available for gamete and larval development. We suggest that the brood pouches and the hermaphroditic gonads of Argyrotheca spp. and Joania compensate these limitations by minimizing the loss of gametes and larvae, and by maximizing the chances of successful fertilization. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.     

Striking difference in response to expanding brood parasites by birds in western and eastern Beringia

Two species of obligate brood‐parasitic Cuculus cuckoos are expanding their ranges in Beringia. Both now breed on the Asian side, close to the Bering Strait, and are found in Alaska during the breeding season. From May to July 2017, we used painted 3D‐printed model eggs of two cuckoo host‐races breeding in northeastern Siberia to test behavioral responses of native songbirds on both sides of the Bering Strait, with particular attention to species that are known cuckoo hosts in their Siberian range. Each host nest was tested after the second egg was laid and, if possible, again 4 days later with a model of a different type. Although our Siberian study site was also outside the known breeding ranges of the cuckoos, we found that Siberian birds had strong anti‐parasite responses, with 14 of 22 models rejected. In contrast, birds in Alaska had virtually no detectable anti‐parasite behaviors, with only one of 96 models rejected; the rejecters were Red‐throated Pipits (Anthus cervinus). Such differences suggest that the cuckoos might successfully parasitize naïve hosts and become established in North America whether or not their historic host species are widely available.     

Phylogeography of the parasitic fly Batrachomyia in the Wet Tropics of north-east Australia, and susceptibility of host frog lineages in a mosaic contact zone

Parasites could differentially impact intraspecific host lineages due to genetic, phenotypic, ecological, or behavioural differences between the lineages, or the development of reproductive isolation between them. Batrachomyia (Diptera: Chloropidae) are flies that exclusively parasitize Australian frogs, and in the Wet Tropics rainforest of north‐east Australia larvae are largely restricted to the green‐eyed tree frog Litoria genimaculata (Anura: Hylidae). This frog species consists of two highly divergent genetic lineages that overlap in two nearby, but independent, contact zones. At one contact zone there has been extensive phenotypic divergence and speciation between the lineages whereas, at the other contact relatively lower levels of phenotypic divergence and reproductive isolation suggest that speciation has not occurred. In the present study we tested: (1) whether the deep phylogeographic divergence between northern and southern host populations is mirrored by congruent genetic structuring in the parasite populations and (2) whether the host lineages are differentially impacted by parasitism. We found that the two divergent frog lineages are parasitized by a single lineage of Batrachomyia, which exhibits strikingly little phylogeographic structuring. We found a significant difference in Batrachomyia prevalence between the host lineages at mixed lineage sites in both contact zones, with the magnitude and direction of this effect being consistent in both. The pattern did not differ between the two contacts even though recent phenotypic divergence and speciation has occurred between the lineages at one contact but not the other. Taken together, this suggests a fundamental difference in susceptibility between the genetically divergent host lineages. Using weight relative to body length as a measure of body condition, we found no differential impact of parasitism on the body condition of each host lineage, and no evidence that parasitism impacts the body condition of the host in general. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 92 , 593–603.     

Sociality in the phylogenetically basal allodapine bee genus Macrogalea (Apidae: Xylocopinae): implications for social evolution in the tribe Allodapini

Recent phylogenetic studies based on DNA sequence data indicate that the tropical African bee genus Macrogalea is the sister group to the remaining extant allodapine fauna, whereas previously it was thought to be a distal group. This leads to some fundamental changes in our understanding of social evolution in the allodapines. Earlier studies suggested that Macrogalea showed only weak forms of social behaviour and these were not well characterized. However, large samples of Macrogalea zanzibarica presented here show that this species exhibits marked social behaviour. Nearly half of nests collected contained two or more adult females, with up to 10 females per nest. Brood are reared progressively and brood ages within colonies are staggered, giving rise to colonies with very mixed age structures and therefore frequent opportunities for alloparental care. Ovarian dissections indicate non‐simple forms of reproductive partitioning within colonies and most multi‐female colonies show evidence that more than one female has contributed to egg production, though reproductive episodes among colony members are frequently asynchronous. Some females show signs of much higher wing wear than their nestmates, but always show signs of previous reproduction. Reproductive division of labour appears to be temporally marked, ovarian differentiation among nestmates is linked to relative body size, but permanent worker‐like or queen‐like castes appear to be absent. This is similar to the communal, continuously brooded and multivoltine behaviour of some tropical halictine species and may be due to the aseasonal nature of brood development in tropical regions. Patterns of per capita brood production indicate large benefits to multi‐female nest occupancy, and sex allocation is strongly female biased. These findings strongly suggest that the capacity for complex social interactions and alloparental care is an ancestral trait for all of the extant allodapine lineages. Therefore comparisons among extant allodapines are unlikely to throw light on the initial origin of social behaviour, though they may uncover origins of true caste behaviour and reversals to solitary nesting. Sex ratios in Macrogalea and most other allodapine genera, spanning a broad phylogenetic and ecological range, suggest that one or more allodapine traits have provided persistent selection for female‐biased sex allocation.     

Microgeographic genetic structure and intraspecific parasitism in the ant Leptothorax nylanderi

1. Genetic colony structure of the small central European ant Leptothorax nylanderi is affected strongly by ecological constraints such as nest site availability and intraspecific social parasitism. 2. Although L. nylanderi is generally monogynous and monandrous, more than a quarter of all nests collected in a dense population near Würzburg, Germany, contained several matrilines. As shown by microsatellite analysis, the average nest‐mate relatedness in these nests was 0.20. Genetically heterogeneous nests arise from nest take‐over by alien colonies or founding queens, a result of severe competition for nest sites. 3. In summer, more than one‐third of all colonies inhabited several nest sites at a time. Polydomy appears to be rather limited, with two or three nests belonging to a single polydomous colony. 4. Queens appear to dominate male production; only a small fraction (8%) of males was definitively not progeny of the queen present but might have been worker progeny or offspring of another queen. 5. Strong evidence for heterozygote deficiency was found and a total of nine diploid males was discovered in two colonies. These findings suggest deviation from random mating through small, localised nuptial flights.     

Small hosts infrequently disrupt laying by Brown-headed Cowbirds and Bronzed Cowbirds

ABSTRACT Brood parasites often must overcome host defenses that may include behaviors that serve other functions, such as deterrence of predators and nest attendance during laying and incubation. Host use by brood parasites may also be influenced by competitors in areas where more than one parasitic species occurs. We identified the degree to which behavior of potential hosts and potential competitors affected laying by Brown‐headed Cowbirds (Molothrus ater) and Bronzed Cowbirds (M. aeneus) at a site in south Texas where they co‐occur. We watched potential host nests during the presunrise period to record cowbird laying and document nest visitation, laying, cowbird‐host encounters, and nest attentiveness by hosts. Hosts were frequently at their nests when cowbirds laid eggs (83% of 121 watches among nests of five host species) and cowbirds regularly encountered hosts (43–74% and 40–77% of watches per species of host for Brown‐headed and Bronzed cowbirds, respectively). Host nest defense infrequently interfered with cowbird laying and cowbirds rarely interacted with one another during laying. Overall, 12% of the 42 cowbird laying attempts that elicited host nest defense failed, resulting in cowbird eggs either laid atop hosts as they sat in nests or laid outside the nest cup. We clearly documented that relatively small hosts can thwart parasitism by cowbirds. Thus, the potential for successful defense of nests should be considered when assessing the evolution of behaviors to deter the removal of host eggs by cowbirds and mechanisms leading to nest abandonment. Regarding the latter, the presence of a cowbird at a nest would be a poor indicator for parasitism as some laying attempts were thwarted and unparasitized broods were reared at those nests. Despite the potential for nest defense to affect host use by cowbirds, we did not detect an effect of nest defense. Because most host defense was ineffective, we examined hypotheses for the timing of cowbird laying and host nest attendance. Our analysis of time of day of laying by Brown‐headed Cowbirds at our site and data compiled from the literature suggests that laying time is best predicted by the time of civil twilight (first light) rather than sunrise.     

Long-distance dispersal by a parasitoid (Anagrus delicatus,Mymaridae) and its host

Summary We demonstrate that an egg parasitoid, Anagrus delicatus (Mymaridae, Hymenoptera) and its host, Prokelesia marginata (Delphacidae, Homoptera) regularly disperse 1 km or more in a north Florida saltmarsh. Anagrus delicatus were caught on yellow sticky traps on offshore islets and oyster bars throughout the spring, summer, and fall, whereas P. marginata were caught during one pulse in the spring. Parasitism rates were higher on offshore islets than at mainland sites, even though egg densities were higher at the mainland sites. The majority of parasitoids caught offshore were females. Long-distance dispersal by A. delicatus may be a cause of inverse density-dependent or density-independent spatial patterns of parasitism and may represent a risk-spreading strategy.     

The analysis of planktonic rotifer populations: A plea for long-term investigations

Short-term species succession, and long-term community development, of planktonic rotifer populations of the temperate zone and factors influencing species' abundance (ie., physical and chemical limitations, food and exploitative competition, mechanical interference competition, predation, parasitism) are described and discussed. The long-term development of plankton communities in three European lakes is described and the major events are discussed in relation to ecological interactions. Frequently, the shortcomings of our knowledge about population ecology and ecophysiology of rotifers prevent explanations of short-term and, especially, of long-term developments of these plankton organisms. The need for qualitative and quantitative observations in the field and in the laboratory over long periods becomes obvious.