Demography of an alpine population of Savannah Sparrows

ABSTRACT.   Although Savannah Sparrows ( Passerculus sandwichensis ) have been well studied across their North American range, few data are available for populations that breed in high-elevation habitats. We collected data over six years on the demography of a population of Savannah Sparrows ( P. s. anthinus ) breeding in alpine tundra and sub-alpine meadows in northern British Columbia, Canada. The mean duration of the breeding season at our site was 45.5 d, and pairs produced a maximum of one brood per season. Clutch sizes varied annually (mean = 4.37, range = 3.90 – 4.71 eggs). Nest fate also varied among years (range = 33 – 92%) due to variation in abiotic (weather) and biotic (predators) conditions. Uncorrected return rates of banded birds were 68% for adults and 17% for juveniles ( N = 22 and 102, respectively). However, when resighting probability was taken into account, apparent annual survival was 75% for adults and 34% for juveniles. Compared to populations at lower elevations, Savannah Sparrows in our study had shorter breeding seasons, fewer broods per season, larger clutches, and higher adult and juvenile return rates. Our results suggest that Savannah Sparrows that breed in high-elevation habitats have adopted a low fecundity, high survival life history strategy that enables their persistence in these challenging environments.     

PRTFDC1 is a genetic modifier of HPRT-deficiency in the mouse

Lesch-Nyhan disease (LND) is a severe X-linked neurological disorder caused by a deficiency of hypoxanthine phosphoribosyltransferase (HPRT). In contrast, HPRT-deficiency in the mouse does not result in the profound phenotypes such as self-injurious behavior observed in humans, and the genetic basis for this phenotypic disparity between HPRT-deficient humans and mice is unknown. To test the hypothesis that HPRT deficiency is modified by the presence/absence of phosphoribosyltransferase domain containing 1 (PRTFDC1), a paralog of HPRT that is a functional gene in humans but an inactivated pseudogene in mice, we created transgenic mice that express human PRTFDC1 in wild-type and HPRT-deficient backgrounds. Male mice expressing PRTFDC1 on either genetic background were viable and fertile. However, the presence of PRTFDC1 in the HPRT-deficient, but not wild-type mice, increased aggression as well as sensitivity to a specific amphetamine-induced stereotypy, both of which are reminiscent of the increased aggressive and self-injurious behavior exhibited by patients with LND. These results demonstrate that PRTFDC1 is a genetic modifier of HPRT-deficiency in the mouse and could therefore have important implications for unraveling the molecular etiology of LND.     

Use of simultaneous pressure and velocity measurements to estimate arterial wave speed at a single site in humans

It has not been possible to measure wave speed in the human coronary artery, because the vessel is too short for the conventional two-point measurement technique used in the aorta. We present a new method derived from wave intensity analysis, which allows derivation of wave speed at a single point. We apply this method in the aorta and then use it to derive wave speed in the human coronary artery for the first time. We measured simultaneous pressure and Doppler velocity with intracoronary wires at the left main stem, left anterior descending and circumflex arteries, and aorta in 14 subjects after a normal coronary arteriogram. Then, in 10 subjects, serial measurements were made along the aorta before and after intracoronary isosorbide dinitrate. Wave speed was derived by two methods in the aorta: 1) the two-site distance/time method (foot-to-foot delay of pressure waveforms) and 2) a new single-point method using simultaneous pressure and velocity measurements. Coronary wave speed was derived by the single-point method. Wave speed derived by the two methods correlated well (r = 0.72, P < 0.05). Coronary wave speed correlated with aortic wave speed (r = 0.72, P = 0.002). After nitrate administration, coronary wave speed fell by 43%: from 16.4 m/s (95% confidence interval 12.6-20.1) to 9.3 m/s (95% confidence interval 6.5-12.0, P < 0.001). This single-point method allows determination of wave speed in the human coronary artery. Aortic wave speed is correlated to coronary wave speed. Finally, this technique detects the prompt fall in coronary artery wave speed with isosorbide dinitrate.     

Impact of short-term temperature challenges on the larvicidal activities of the entomopathogenic watermold Leptolegnia chapmanii against Aedes aegypti, and development on infected dead larvae

The oomycete Leptolegnia chapmanii is among the most promising entomopathogens for biological control of Aedes aegypti. This mosquito vector breeds in small water collections, where this aquatic watermold pathogen can face short-term scenarios of challenging high or low temperatures during changing ambient conditions, but it is yet not well understood how extreme temperatures might affect the virulence and recycling capacities of this pathogen. We tested the effect of short-term exposure of encysted L. chapmanii zoospores (cysts) on A. aegypti larvae killed after infection by this pathogen to stressful low or high temperatures on virulence and production of cysts and oogonia, respectively. Cysts were exposed to temperature regimes between ?12 °C and 40 °C for 4, 6 or 8 h, and then their infectivity was tested against third instar larvae (L3) at 25 °C; in addition, production of cysts and oogonia on L3 killed by infection exposed to the same temperature regimes as well as their larvicidal activity were monitored. Virulence of cysts to larvae and the degree of zoosporogenesis on dead larvae under laboratory conditions were highest at 25 °C but were hampered or even blocked after 4 up to 8 h exposure of cysts or dead larvae at both the highest (35 °C and 40 °C) and the lowest (?12 °C) temperatures followed by subsequent incubation at 25 °C. The virulence of cysts was less affected by accelerated than by slow thawing from the frozen state. The production of oogonia on dead larvae was stimulated by short-term exposure to freezing temperatures (?12 °C and 0 °C) or cool temperatures (5 °C and 10 °C) but was not detected at higher temperatures (25 °C–40 °C). These findings emphasize the susceptibility of L. chapmanii to short-term temperature stresses and underscore its interest as an agent for biocontrol of mosquitoes in the tropics and subtropics, especially A. aegypti, that breed preferentially in small volumes of water that are generally protected from direct sunlight.     

Revisiting the particular role of host shifts in initiating insect speciation

The notion that shifts to new hosts can initiate insect speciation is more than 150 years old, yet widespread conflation with paradigms of sympatric speciation has led to confusion about how much support exists for this hypothesis. Here, we review 85 insect systems and evaluate the relationship between host shifting, reproductive isolation, and speciation. We sort insects into five categories: (1) systems in which a host shift has initiated speciation; (2) systems in which a host shift has made a contribution to speciation; (3) systems in which a host shift has caused the evolution of new reproductive isolating barriers; (4) systems with host‐associated genetic differences; and (5) systems with no evidence of host‐associated genetic differences. We find host‐associated genetic structure in 65 systems, 43 of which show that host shifts have resulted in the evolution of new reproductive barriers. Twenty‐six of the latter also support a role for host shifts in speciation, including eight studies that definitively support the hypothesis that a host shift has initiated speciation. While this review is agnostic as to the fraction of all insect speciation events to which host shifts have contributed, it clarifies that host shifts absolutely can and do initiate speciation.     

Increasing oxytocin receptor expression in the nucleus accumbens of pre-pubertal female prairie voles enhances alloparental responsiveness and partner preference formation as adults

Oxytocin receptors (OXTR) in the nucleus accumbens (NAcc) promote alloparental behavior and partner preference formation in female prairie voles. Within the NAcc there is significant individual variation in OXTR binding and virgin juvenile and adult females with a high density of OXTR in the NAcc display an elevated propensity to engage in alloparental behavior toward novel pups. Over-expression of OXTR in the NAcc of adult female prairie voles using viral vector gene transfer facilitates partner preference formation, but has no effect on alloparental behavior, even though OXTR antagonists infused into the NAcc blocks both behaviors. We therefore hypothesized that long-term increases in OXTR signaling during development may underlie the relationship between adult OXTR density in the NAcc and alloparental behavior. To test this hypothesis, we used viral vector gene transfer to increase OXTR density in the NAcc of prepubertal, 21 day old female prairie voles and tested for both alloparental behavior and partner preference formation as adults. Consistent with a developmental impact of OXTR signaling, adults over-expressing OXTR from weaning display both increased alloparental behavior and partner preference formation. Thus, the relatively acute impact of elevated OXTR signaling in the NAcc on partner preference formation previously reported appears to be dissociable from the effects of longer term, developmentally relevant OXTR signaling necessary for modulating alloparental behavior. These results are consistent with the hypothesis that oxytocin can have both long-term “organizational” effects as well as acute “activational” effects on affiliative behaviors.     

Extended incubation recesses by alpine‐breeding Horned Larks: a strategy for dealing with inclement weather?

ABSTRACT Incubating birds can incur high energetic costs and, when faced with a trade‐off between incubation and foraging, parents may neglect their eggs in favor of their own somatic needs. Extended incubation recesses are an example of neglect, but they are often treated as outliers and largely overlooked in studies of incubation behavior. We studied incubation rhythms of Horned Larks (Eremophila alpestris) on Hudson Bay Mountain, British Columbia, Canada, during four breeding seasons. Incubation recesses averaged 10.92 ± 0.38 min (N= 4076 2‐h periods), but we observed 70 extended recesses, ranging from 59 to 387 min in duration, at 35 nests. Although rare (<1% of all daytime recesses), extended recesses occurred in all 4 yr, were longer and more frequent in colder years (60% occurred in the two coldest years), and often occurred during inclement weather (39% occurred during three storm events). Extended recesses did not appear to compensate for long attendance periods because extended recess duration was not correlated with the duration of previous on‐bouts (P= 0.10, N= 70) or the mean on‐bout duration of the previous 2‐h period (P= 0.36, N= 70). Rather, extended recesses seemed to reflect a shift in parental investment away from their eggs and toward self‐maintenance when faced with energetically stressful conditions. Extended recesses may have reduced embryo viability; egg‐hatching rates were 91 ± 2.4% for nests where females did not take extended recesses and 81 ± 4.2% for nests where females did take extended recesses (P= 0.02, N= 56 nests). Extended recesses during incubation are rare events, but they may represent an important mechanism that allows birds to breed successfully in energetically challenging conditions.     

Phylogenetic relationships among the Ithomiini (Lepidoptera: Nymphalidae) inferred from one mitochondrial and two nuclear gene regions

Abstract.  A phylogenetic hypothesis for the tribe Ithomiini (Lepidoptera: Nymphalidae: Danainae) is presented, based on sequences of the mitochondrial cytochrome oxidase subunits I and II (COI–COII) region and regions of the nuclear genes wingless and Elongation factor 1-alpha . Branch support for each clade is assessed, and a partition congruence index is used to explore conflict among gene regions. The monophyly of the clade is strongly supported, as are many of the traditionally recognized subtribes and genera. The data imply paraphyly of some genera and tribes, but largely support recent classifications and phylogenetic hypotheses based on morphological characters.     

Simulating the effect of evaluation unit size on eligibility to stop mass drug administration for lymphatic filariasis in Haiti

BackgroundThe Transmission Assessment Survey (TAS) is a decision-making tool to determine when transmission of lymphatic filariasis is presumed to have reached a level low enough that it cannot be sustained even in the absence of mass drug administration. The survey is applied over geographic areas, called evaluation units (EUs); existing World Health Organization guidelines limit EU size to a population of no more than 2 million people.Methodology/Principal findingsIn 2015, TASs were conducted in 14 small EUs in Haiti. Simulations, using the observed TAS results, were performed to understand the potential programmatic impact had Haiti chosen to form larger EUs. Nine “combination-EUs” were formed by grouping adjacent EUs, and bootstrapping was used to simulate the expected TAS results.When the combination-EUs were comprised of at least one “passing” and one “failing” EU, the majority of these combination-EU would pass the TAS 79% - 100% of the time. Even in the case when both component EUs had failed, the combination-EU was expected to “pass” 11% of the time.Simulations of mini-TAS, a strategy with smaller power and hence smaller sample size than TAS, resulted in more conservative “passing” and “failing” when implemented in original EUs.Conclusions/SignificanceOur results demonstrate the high potential for misclassification when the average prevalence of lymphatic filariasis in the combined areas differs with regards to the TAS threshold. Of particular concern is the risk of “passing” larger EUs that include focal areas where prevalence is high enough to be potentially self-sustaining. Our results reaffirm the approach that Haiti took in forming smaller EUs. Where baseline or monitoring data show a high or heterogeneous prevalence, programs should leverage alternative strategies like mini-TAS in smaller EUs, or consider gathering additional data through spot check sites to advise EU formation.