Understanding the environmental drivers of demographic rates and population dynamics over space and time is critical for anticipating how species will respond to climate change. While the influence of temporal environmental variation and large environmental gradients are well recognized, less is known about how local topography and landscape position influence demography over small spatial scales. Here, we investigate how local landscape position (north-vs. south-facing aspects) influence the demographic rates and population growth of a common bunchgrass in western North America, bluebunch wheatgrass (Pseudoroegneria spicata), using 6 annual censuses measuring growth, survival, and reproductive output. We found notably lower survival on south-facing slopes, particularly among smaller individuals. In contrast, south-facing slopes maintained comparatively high reproductive output in most years, measured both as spikes per plant and spikelets per spike. When we combined these data in demographic models, we found that lower survival among small individuals and greater reliance on reproduction mean south-facing slopes would generally have to maintain higher recruitment for a stable population. Our results highlight the important influence that landscape position and local topography can have in driving population trends. As conditions warm and dry with climate change (north-faces becoming similar to current south-facing slope conditions), bluebunch wheatgrass may become more reliant on reproduction to maintain viable populations and more sensitive to variability in recruitment.

Understanding the environmental drivers of demographic rates and population dynamics over space and time is critical for anticipating how species will respond to climate change. While the influence of temporal environmental variation and large environmental gradients are well recognized, less is known about how local topography and landscape position influence demography over small spatial scales. Here, we investigate how local landscape position (north- vs. south-facing aspects) influence the demographic rates and population growth of a common bunch grass in western North America, bluebunch wheatgrass (Pseudoroegneria spicata), using 6 years of annual censuses measuring growth, survival, and reproductive output. We found notably lower survival on south facing slopes, particularly among smaller individuals. In contrast, south-facing slopes maintained comparatively high reproductive output in most years, measured both as spikes per plant and spikelets per spike. We also found that lower survival among small individuals and greater reliance on reproduction mean south-facing slopes should also be more sensitive to changes in the recruitment rate, and would generally have to maintain higher recruitment for stable population growth. Taken together, our results highlight the important influence that landscape position and local topography can have in driving populations. As conditions warm and dry with climate change (similar to south facing slopes), bluebunch wheatgrass may become more reliant on reproduction to maintain viable populations and more sensitive to variability in recruitment.

Population manipulations such as translocation and head-starting are increasingly used as recovery tools for chelonians. But evaluating success of individual projects can require decades of monitoring to detect population trends in these long-lived species. Furthermore, there are often few benchmarks from stable, unmanipulated populations against which to compare demographic rates, particularly for the immature stages. We used 8 years of mark-recapture data to estimate apparent survival of immature gopher tortoises (Gopherus polyphemus) recruited into an introduced population of gopher tortoises first established on St. Catherines Island, Georgia, USA, in 1987. During 2006-2013, we conducted targeted trapping of immature gopher tortoises and compared survival of the hatchling, juvenile and subadult stages among treatments: individuals released shortly after hatching from eggs obtained from gravid female founders (direct releases), individuals reared in captivity for 6-9 months following hatching (head-starts), and individuals first encountered as free-ranging, wild-recruited offspring (wild recruits). Among the candidate models we examined, the best fit model included additive effects of tortoise stage and treatment; however, overlapping 95% credible intervals among treatments (CrI) suggested that survival did not vary significantly among treatments. Annual apparent survival increased over the immature period, highlighting the importance of calculating separate estimates for the different immature stages. Across all treatments, the additive model estimated annual apparent survival probability to be 0.37 (CrI = 0.25-0.48) for hatchlings, 0.71 (CrI = 0.61-0.81) for juveniles, and 0.83 (CrI = 0.74-0.94) for subadults. Our study, in combination with previous monitoring efforts at St. Catherines Island, provides strong evidence that the translocation and subsequent population augmentation efforts have been successful in establishing a robust population of gopher tortoises. Additionally, our results provide estimates of demographic rates for life stages that are poorly understood but critical to understanding population dynamics of this imperiled species.

Line‐transect distance sampling (LTDS) surveys are commonly used to estimate abundance of animals or objects. In terrestrial LTDS surveys of gopher tortoise (Gopherus polyphemus) burrows, the presence of ground‐level vegetation substantially decreases detection of burrows of all sizes, but no field or analytical methods exist to control for spatially heterogeneous vegetation obstruction as a source of variation in detection. We propose the addition of a simple measurement of ground‐level vegetation that serves as a covariate for the detection function. We present a Bayesian hierarchical model in which covariates burrow width and nearby vegetation height help to account for detection bias and improve precision of estimated density. We investigate the performance of this covariate by simulation and by using real LTDS data collected before and after application of prescribed fire. We collected data in 2018 at the Jones Center at Ichauway in Newton, Georgia, USA. Across all simulations, our model including both covariates produced the most accurate density point estimates of any of the models tested. For our case study, our Bayesian model with vegetation covariates tended to produce similar estimates of density before and after burns. Our study indicates that any level of spatial variation in vegetation obstruction decreases detection of burrows and may lead to underestimation in population size (≤68%) and proportion of individuals with small burrow sizes (≤32%) when not considered during analysis. Our work is extensible to other terrestrial sampling efforts where systematic measurement of a spatially distributed obstructing feature is feasible during the LTDS survey.

Because of their large size, colorful flowers, and insectivorous habit, butterworts (genus Pinguicula) are desirable ornamental plants among hobbyists and botanical conservatories. Propagation via leaves is a popular propagation method for the genus, especially for tropical species. P. gigantea, a species found approximately 700m above sea level in Oaxaca, Mexico, was selected to evaluate its preference for various blends of soilless media. This study found that number of leaves produced by plantlets is significantly impacted by soil type. However, there was no significant difference in biomass, plantlet diameter or average number of plantlets produced between soil treatments. These results suggest that soils with high nitrogen content may promote increased leaf number, but do not significantly affect plant biomass.