Robustness of close‐kin mark–recapture estimators to dispersal limitation and spatially varying sampling probabilities

1. Close‐kin mark–recapture (CKMR) is a method for estimating abundance and vital rates from kinship relationships observed in genetic samples. CKMR inference only requires animals to be sampled once (e.g., lethally), potentially widening the scope of population‐level inference relative to traditional monitoring programs.
2. One assumption of CKMR is that, conditional on individual covariates like age, all animals have an equal probability of being sampled. However, if genetic data are collected opportunistically (e.g., via hunters or fishers), there is potential for spatial variation in sampling probability that can bias CKMR estimators, particularly when genetically related individuals stay in close proximity.
3. We used individual‐based simulation to investigate consequences of dispersal limitation and spatially biased sampling on performance of naive (nonspatial) CKMR estimators of abundance, fecundity, and adult survival. Population dynamics approximated that of a long‐lived mammal species subject to lethal sampling.
4. Naive CKMR abundance estimators were relatively unbiased when dispersal was unconstrained (i.e., complete mixing) or when sampling was random or subject to moderate levels of spatial variation. When dispersal was limited, extreme variation in spatial sampling probabilities negatively biased abundance estimates. Reproductive schedules and survival were well estimated, except for survival when adults could emigrate out of the sampled area. Incomplete mixing was readily detected using Kolmogorov–Smirnov tests.
5. Although CKMR appears promising for estimating abundance and vital rates with opportunistically collected genetic data, care is needed when dispersal limitation is coupled with spatially biased sampling. Fortunately, incomplete mixing is easily detected with adequate sample sizes. In principle, it is possible to devise and fit spatially explicit CKMR models to avoid bias under dispersal limitation, but development of such models necessitates additional complexity (and possibly additional data). We suggest using simulation studies to examine potential bias and precision of proposed modeling approaches prior to implementing a CKMR program.

     

Bim Mediates the Elimination of Functionally Unfit Th1 Responders from the Memory Pool

Selective clonal deletion in the CD4⁺ T cell compartment during the transition from effector to memory is accompanied by enhanced expression of the pro-apoptotic Bcl-2 family member Bim. Here, we show that Bim deficiency enables the survival of poorly functional Th1 responders that are normally eliminated during contraction. However, rescued bim ^−/− CD4⁺ “memory” T cells continued to demonstrate deficient effector functions, poor sensitivity to antigen and an inability to respond to secondary challenge. Our results demonstrate that Bim activity plays a key role in shaping the CD4⁺ memory T cell repertoire, ensuring the emergence of highly functional CD4⁺ memory T cells and the elimination of Th1 effector cells with sub-optimal function. We propose that Bim is a key mediator of T cell death in the absence of appropriate TCR-driven activation and differentiation.     

Polycations. 19. The synthesis of symmetrical dicationic lipids with internal dimethylazonia functionalities separated by a spacer unit and pendant chains

Herein is reported the preparation of several series of symmetrical polyammonium salts that serve as cationic lipids or precursors thereof, and are structurally based on several series of parent diamines where dimethylazonia functionalities are present, separated by a central structural unit, and pendant terminal chains. The resultant materials are of significant interest for a variety of purposes, such as serving as antihydrophobic species and as transfectins, the details of which are provided in separate reports. Attempts to effect selective alkylation to provide the corresponding unsymmetrical cationic lipids were without success, always leading to relatively useless mixtures of products.     

Toward a Reconstitution of Ethnicity: Capitalist Expansion and Cultural Dynamics in Sudan

In this article I argue that, despite recent advances in anthropology, prevailing images of ethnicity in academic discourse overemphasize units at the expense of interconnections and tend toward ahistorical formalism. Through an examination of the dynamics of ethnic segmentation of the agricultural labor force in Sudan in this century, I seek to show that both the modem character of ethnicity as an organizing principle and the content of particular ethnic identities in Sudan emerged in the process of peripheral capitalist development. Ethnicity in these circumstances is thus fundamentally different from the ethnicity of the Sudanese past and from ethnic principles articulated elsewhere under different social conditions.