Landscapes differ in the composition and configuration of habitats, and this heterogeneity can influence the manner in which invasive species spread in complex ways. To understand this complexity, we outline a framework that identifies how landscape heterogeneity influences spread by causing dispersal behaviour and local population growth to vary across the landscape. We use this framework to review progress over the last 5 years in understanding landscape effects on invasive spread, focussing on the role of interactions between landscape heterogeneity, dispersal and population processes.

Imperfect detection can bias estimates of site occupancy in ecological surveys but can be corrected by estimating detection probability. Time‐to‐first‐detection (TTD) occupancy models have been proposed as a cost–effective survey method that allows detection probability to be estimated from single site visits. Nevertheless, few studies have validated the performance of occupancy‐detection models by creating a situation where occupancy is known, and model outputs can be compared with the truth. We tested the performance of TTD occupancy models in the face of detection heterogeneity using an experiment based on standard survey methods to monitor koala Phascolarctos cinereus populations in Australia. Known numbers of koala faecal pellets were placed under trees, and observers, uninformed as to which trees had pellets under them, carried out a TTD survey. We fitted five TTD occupancy models to the survey data, each making different assumptions about detectability, to evaluate how well each estimated the true occupancy status. Relative to the truth, all five models produced strongly biased estimates, overestimating detection probability and underestimating the number of occupied trees. Despite this, goodness‐of‐fit tests indicated that some models fitted the data well, with no evidence of model misfit. Hence, TTD occupancy models that appear to perform well with respect to the available data may be performing poorly. The reason for poor model performance was unaccounted for heterogeneity in detection probability, which is known to bias occupancy‐detection models. This poses a problem because unaccounted for heterogeneity could not be detected using goodness‐of‐fit tests and was only revealed because we knew the experimentally determined outcome. A challenge for occupancy‐detection models is to find ways to identify and mitigate the impacts of unobserved heterogeneity, which could unknowingly bias many models.

Kentucky bluegrass (Poa pratensis L.) is one of the most aggressive grasses invading Northern Great Plains (NGP) grasslands, resulting in substantial native species losses. Highly diverse grasslands dominated by native species are gradually transforming into rangelands largely dominated by non-native Kentucky bluegrass. Several factors potentially associated with Kentucky bluegrass invasions, including high propagule pressure, thatch formation, climate change, and increasing nitrogen deposition, could determine the future dominance and spread of Kentucky bluegrass in the NGP. Because atmospheric CO2 is amplifying rapidly, a C3 grass like Kentucky bluegrass might be photosynthetically more efficient than native C4 grasses. As this exotic species shares similar morphological and phenological traits with many native cool-season grasses, controlling it with traditional management practices such as prescribed fire, grazing, herbicides, or combinations of these practices may also impair the growth of native species. Thus, developing effective management practices to combat Kentucky bluegrass spread while facilitating the native species cover is essential. Modifying traditional techniques and embracing science-based adaptive management tools that focus on the ecological interactions of Kentucky bluegrass with the surrounding native species could achieve these desired management goals. Enhancement of the competitiveness of surrounding native species could also be an important consideration for controlling this invasive species.

Smooth brome (Bromus inermis Leyss.) is an invasive cool-season grass that has spread throughout the Great Plains of North America. The species is considered one of the most widespread exotic grasses that has successfully invaded both cool-season and warm-season native prairies. In the prairies where it has invaded, there has often been a total elimination of native species and an overall homogenization of ecosystems. Smooth brome has greater competitive abilities compared to many native grasses and can foster their total elimination in many instances. The greater competitiveness can be partially attributed to its ability to alter the soil and hydrological properties of a site. It is a deep-rooted rhizomatous grass species that thrives in nitrogen-enriched soil, and since its leaf tissue decomposes faster than native species, it in turn increases the soil nitrogen level, causing positive plant–soil feedback. Moreover, smooth brome is able to transport the required nutrients from older plants to the newer progenies invading new nutrient-depleted areas, making it a potent invader. However, the impact of smooth brome is not limited to soil biochemistry alone; it also affects other ecosystem components such as the movement and behavior of many native arthropods, thereby altering the overall population dynamics of such species. Thus, smooth brome invasion poses a serious threat to the remnant prairies of the Great Plains, and efficient management strategies are urgently needed to control its invasion. Control measures such as mowing, grazing, burning, and herbicide application have been effectively used to manage this species. However, due to the widespread distribution of smooth brome across North America and its adaptability to a wide range of environmental conditions, it is challenging to translate the management strategies from one area to another.

Plains rough fescue (Festuca hallii [Vasey] Piper) is an important forage grass species in the Northern Great Plains of Canada. Its seed is in demand for forage production and habitat restoration, but erratic seed production limits supply. A comprehensive understanding of factors influencing flowering and seed production in this species is needed. This study evaluated the morphological and phenological variation among six ecotypes of F. hallii from Saskatchewan and Manitoba. Seeds were germinated, and seedlings were grown in the field and then transplanted to a greenhouse in November. Plants not flowering in the greenhouse were vernalized under 5°C and 8‐h light for 11 weeks. In a separate experiment, plants were subjected to temperature regimes of 15/5°C, 10/0°C and 5/−5°C with day‐length treatments of 12 h, 8 h and a gradually changing daylength from 12 to 8 h respectively. This study demonstrated the existence of considerable variation in morphological and phenological characteristics, and in growth and vernalization requirements among ecotypes of F. hallii. Vernalization requirements were not met for the ecotype from the Moist Mixed Grassland Ecoregion when it was grown under common conditions, whereas ecotypes from other ecoregions were vernalized in at least one of the 2 years in the field experiment. Northern ecotypes tended to flower earlier after artificial vernalization treatments. Overall, 15/5 to 5/−5°C d per night temperature regimes with photoperiods between 12 and 8 h were effective in inducing flowering. The seed source of F. hallii should be regarded as an important consideration affecting its use, both for habitat restoration and for forage production.