Individual heterogeneity in fitness in a long-lived herbivore

Heterogeneity in the intrinsic quality and nutritional condition of individuals affects reproductive success and consequently fitness. Understanding differences in energy allocation towards survival and reproduction within and among years might help explain variability in individual fitness. Black brant (Branta bernicla nigricans) are long-lived, migratory, specialist herbivores. Long migratory pathways and short summer breeding seasons constrain the time and energy available for reproduction, thus magnifying life-history trade-offs. These constraints, combined with long lifespans and trade-offs between current and future reproductive value, provide a model system to examine the role of individual heterogeneity in driving life-history strategies and individual heterogeneity in fitness. We used hierarchical Bayesian models to examine reproductive trade-offs, modeling the relationships between within-year measures of reproductive energy allocation and among-year demographic rates of individual females breeding on the Yukon-Kuskokwim Delta, Alaska using capture-recapture and reproductive data from 1988 to 2014. We provide evidence for relationships between breeding probability and clutch size (posterior mean of β = 0.45, 95% CRI = 0.33 – 0.57, SD = 0.06), breeding probability and nest initiation date (posterior mean of β = -0.12, 95% CRI = -0.2 ¬– -0.04, SD = 0.04), and an interaction between clutch size and initiation date (posterior mean of β = -0.12, 95% CRI = -0.2 – -0.04, SD = 0.04). Average lifetime clutch size also had a weak positive relationship with survival probability (posterior mean of β = 0.03, 95% CRI = -0.01 – 0.7, SD = 0.02). Our results support the use of demographic buffering strategies for black brant; reductions in reproductive energy allocation preserve high adult survival rates during years with poor environmental conditions, maximizing future reproductive value. We also indirectly show links among environmental conditions during growth, fitness, and energy allocation, highlighting the effects of early growth conditions on individual heterogeneity, and subsequently, reproductive investment.

ОЦЕНКА ВОЗМОЖНОСТЕЙ ПРИМЕНЕНИЯ СУБОРБИТАЛЬНЫХ РАКЕТ-НОСИТЕЛЕЙ ДЛЯ ВЫВЕДЕНИЯ СРЕДСТВ УВОДА ОБЪЕКТОВ КОСМИЧЕСКОГО МУСОРА С НИЗКИХ ОКОЛОЗЕМНЫХ ОРБИТ

The article is devoted to an actual problem of clearing of low earth orbits from space objects of a technogenic origin. Existing versions of struggle against space debris, in particular, removal of technogenic objects with help of the special means for deorbiting delivered into a target orbit by launch vehicles that are especially actual for bulky space debris are considered. Recognizing that the ascent of such means for deorbiting by orbital launch vehicles demands large financial expenses, for an increase of efficiency of delivery the means for deorbiting on a low earth orbit widely known sub-orbital launch vehicles are offered: MAXUS, TEXUS (VSB-30), REXUS (Improved Orion), SS-520, MH-300, Black Brant 12А and the estimation of a capability of their application also is conducted. Are considered the use of sub-orbital launch vehicles for the ascent the means for deorbiting on altitudes of a concentration of space debris on a low earth orbit on a trajectory, close to vertical, with the subsequent operations of interception of demanded space objects, and also modernization of launch vehicles by addition of an additional stage. Results of calculations of an injection trajectory of the means for deorbiting in weight in a layer of space debris in altitude 600 … 1200 km showed of 150 kg that sub-orbital launch vehicles MAXUS, SS-520, Black Brant 12A allow executing delivery the means for deorbiting to altitudes from 770 km to 1200 km and to supply time of its presence in a layer of space debris 420 … 850 s. The most perspective sub-orbital rocket is MAXUS. It possesses higher power and a capability of installation of an additional stage by a decrease in weight of a payload with small losses the power of the first stage. It is shown that the given configuration of the rocket with engine thrust specific impulse in vacuum 300 s and engine thrust in vacuum 16 кН is capable to inject into an elliptical orbit with an altitude of apogee 600 km and altitude of a perigee 130 km with a corner of an inclination 5,5 degrees payload in weight of 55 kg. For orbit short circuit in apogee at the altitude, the upper stage should supply 600 km increase the speeds, equal 133 m/s. Mass characteristics of the second stage are induced.

Dynamics of Dispersed-Nesting Black Brant on the Yukon-Kuskokwim Delta

The number of black brant Branta bernicla nigricans nests within major breeding colonies on the Yukon-Kuskowkim Delta has declined since 1992. It has been hypothesized that these declines are partially explained by increased numbers of black brant breeding outside of these colonies. To assess this hypothesis, we analyzed spatiotemporal patterns in numbers of black brant nests occurring outside major colonies. Nesting densities of black brant vary among three strata: 1) peripheral to major colonies, 2) other coastal habitats, and 3) inland habitats. We sampled some substrata within each stratum type only between 1986 and 1999 (historical strata), whereas we sampled others over the period 1986–2016 (long-term strata). We fit regression models with number of nests on a plot as a response variable, a log link, and year as the explanatory variable. We allowed each stratum (e.g., historical peripheral) to have its own intercept to account for variation in mean nest density but constrained linear and quadratic regression coefficients to be the same for strata in similar habitats (e.g., historical and long-term peripheral). We used a negative binomial distribution for nests to allow for substantial variation in nests per plot. We fit models using Markov Chain Monte Carlo methods in JAGS. Ninety-five percent credible intervals for both linear and quadratic coefficients for the peripheral and coastal strata, where most nests occurred, broadly overlapped zero, indicating modest trends in numbers of nests in these strata. We estimated there were 6,584 (95% credible interval: 4,221−11,269) dispersed nests in 1986, increasing to 11,051 (95% credible interval: 7,450−17,460) in 2016. Our results indicated that increases in dispersed nests were unable to replace declines in colony nests. Furthermore, quadratic trends indicated that potential earlier annual increases in dispersed nests have declined to zero. We conclude that total numbers of black brant nests on the Yukon-Kuskokwim Delta are likely declining, consistent with the trend in fall age ratios over the same period. Uncertainty about trends in areas not sampled since 1994 adds to the uncertainty about the precise magnitude of the decline. We recommend that the area sampled by the random plot program be expanded to include strata sampled only before 1995.

Development of Microsatellite Loci Exhibiting Reverse Ascertainment Bias and a Sexing Marker for use in Emperor Geese (Chen Canagica)

The Alaskan population of Emperor Geese ( Chen canagica) nests on the Yukon–Kuskokwim Delta in western Alaska. Numbers of Emperor Geese in Alaska declined from the 1960s to the mid-1980s and since then, their numbers have slowly increased. Low statistical power of microsatellite loci developed in other waterfowl species and used in previous studies of Emperor Geese are unable to confidently assign individual identity. Microsatellite loci for Emperor Goose were therefore developed using shotgun amplification and next-generation sequencing technology. Forty-one microsatellite loci were screened and 14 were found to be polymorphic in Emperor Geese. Only six markers – a combination of four novel loci and two loci developed in other waterfowl species – are needed to identify an individual from among the Alaskan Emperor Goose population. Genetic markers for identifying sex in Emperor Geese were also developed. The 14 novel variable loci and 15 monomorphic loci were screened for polymorphism in four other Arctic-nesting goose species, Black Brant ( Branta bernicla nigricans), Greater White-fronted ( Anser albifrons), Canada ( B. canadensis) and Cackling ( B. hutchinsii) Goose. Emperor Goose exhibited the smallest average number of alleles (3.3) and the lowest expected heterozygosity (0.467). Greater White-fronted Geese exhibited the highest average number of alleles (4.7) and Cackling Geese the highest expected heterozygosity (0.599). Six of the monomorphic loci were variable and able to be characterised in the other goose species assayed, a predicted outcome of reverse ascertainment bias. These findings fail to support the hypothesis of ascertainment bias due to selection of microsatellite markers.