Invasion speeds for structured populations in fluctuating environments

We live in a time where climate models predict future increases in environmental variability and biological invasions are becoming increasingly frequent. A key to developing effective responses to biological invasions in increasingly variable environments will be estimates of their rates of spatial spread and the associated uncertainty of these estimates. Using stochastic, stage-structured, integro-difference equation models, we show analytically that invasion speeds are asymptotically normally distributed with a variance that decreases in time. We apply our methods to a simple juvenile-adult model with stochastic variation in reproduction and an illustrative example with published data for the perennial herb, \emph{Calathea ovandensis}. These examples buttressed by additional analysis reveal that increased variability in vital rates simultaneously slow down invasions yet generate greater uncertainty about rates of spatial spread. Moreover, while temporal autocorrelations in vital rates inflate variability in invasion speeds, the effect of these autocorrelations on the average invasion speed can be positive or negative depending on life history traits and how well vital rates ``remember'' the past

Seasonal Migration of Sika Deer in the Oku-Chichibu Mountains, Central Japan

Movements and seasonal home ranges of 6 GPS collared sika deer were investigated at the Oku-Chichibu Mountains, central Honshu, from April 2009 to March 2010. All deer migrated between discrete summer and winter home ranges. The linear migration distance ranged from 2.5 to 31.9 km. Mean elevation during the summer and the winter ranged from 980 to 1,782 m, and from 1,204 to 1,723 m, respectively. Two deer were upward migrants and 4 deer were downward migrants. Taking into consideration of the relatively small snow accumulation in the summer home range, the possibility of autumn migration to avoid deep snow is low. The percentage of steep slope in the winter home range was higher than that in the summer. Bamboo grass was not found in the summer home range, but was predominant in the winter home range. Road density decreased in the winter home range compared to the summer. Only 2 out of 6 deer stayed mainly in the wildlife protection area during the winter. Our results indicate that the autumn migration was affected by winter forage and human disturbance, thereby assured the survival of the deer during winter.ArticleMAMMAL STUDY. 37(2):127-137 (2012)journal articl

Long-term Site Fidelity and Individual Home Range Shifts in Lophocebus albigena

We investigated long-term site fidelity of gray-cheeked mangabey (Lophocebus albigena) groups in Kibale National Park, Uganda. Concurrently, we monitored shifts in home range by individual females and subadult and adult males. We documented home range stability by calculating the area of overlap in successive years, and by recording the drift of each group’s monthly centroid from its initial location. Home ranges remained stable for 3 of our 4 groups (overlap over 10 yr >60%). Core areas were more labile, but group centroids drifted an average of only 530 m over the entire decade. Deviations from site fidelity were associated with dispersal or group fission. During natal dispersal, subadult males expanded their home ranges over many months, settling ≤4 home ranges away. Adult males, in contrast, typically dispersed within a few days to an adjacent group in an area of home range overlap. Adult males made solitary forays, but nearly always into areas used by their current group or by a group to which they had previously belonged. After secondary dispersal, they expanded their ranging in the company of their new group, apparently without prior solitary exploration of the new area. Some females also participated in home range shifts. Females shifted home ranges only within social groups, in association with temporary or permanent group splits. Our observations raise the possibility that male mangabeys use a finder-joiner mechanism when moving into new home ranges during secondary dispersal. Similarly, females might learn new resource locations from male immigrants before or during group fission

VIBRATIONAL SPECTROSCOPY OF NH4+(NH3)NNH_{4^{+}}(NH_{3})_{N} IN THE REGION OF THE AMMONIA ν2\nu_{2} VIBRATION

$^{1.}$ J. M. Price, M. W. Crofton, and Y. T. Lee, J. Phys. Chem. 95, 2182 (1991). $^{2}$. T. J. Selegue and J. M. Lisy, J. Phys. Chem. 96, 4143 (1992); T. J. Selegue, N. Moe, and J. M. Lisy, to be published.Author Institution: School of Chemical Sciences, University of Illinois at Urbana-ChampaignAmmoniated ammonium ions are produced by electron impact of a continuous supersonic expansion of $NH_{3}$ in argon. We have produced $NH_{4}^{+}(NH_{3})_{N}$ with $N \leq 60$. The $\nu_{2}$ mode (umbrella mode) of ammonia is excited with a cw $CO_{2}$ laser to induce vibrational predissociation of a mass selected cluster ion. Infrared spectra have been measured for clusters with N up to 15. Our results are consistent with analogous experiments involving excitation of the $\nu_{3}$ (asymmetric NH stretch) mode of $ammonia^{1}$ in which a first ``solvation'' shell of four ammonia molecules was confirmed. Peak absorption frequencies red shift from an $N = 5$ value of $1077 cm^{-1}$ with increasing cluster size, converging to the bulk phase value of $-1050 cm^{-1}$. Comparison will be drawn to our previous studies of ammonia solvated alkali metal cations.