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Context Tall fescue (Schedonorus arundinaceus ) is one of the most important cultivated forage grasses in temperate regions but its association with some Epichloë fungal endophytes usually makes it unsuitable for livestock feeding due to toxic alkaloids. However, re-inoculation of plants with non-toxic endophytes can result in positive effects for livestock feeding. Aims Assess the effects of the non-toxic AR584 endophyte on seed viability and germination in two tall fescue cultivars. Methods The effects of AR584 endophyte (presence/absence) and tall fescue cultivar (INIA Aurora/Taita) were evaluated on seed viability and germination responses across a range of temperature and water availability regimes. Response to constant temperature and water availability was characterised by the thermal-time and hydro-time models, respectively. Key results Under accelerated aging conditions, endophyte presence reduced seed viability in cultivar Taita. For both cultivars, endophyte-infected seeds showed a lower germination rate than endophyte-free seeds, except for INIA Aurora under low incubation temperatures. Also, endophyte-infected seeds in both cultivars displayed lower germination rates and final germination as the water potential was lowered. Conclusions A strong cultivar-by-endophyte interaction for seed germination indicates the need to understand how specific cultivar-endophyte combinations best fit a given environmental condition, as defined by temperature and water availability. Implications The information we present can be valuable not only for farmers who have to decide what to cultivate but also for seed companies that have to preserve seed quality.

Context Tall fescue (Festuca arundinacea Schreb.) is a valuable temperate forage grass. Tall fescue plants associated with Epichloë fungal endophytes are successfully spreading in grassland regions that are recurrently exposed to flooding. Aims We asked whether the association with fungal endophytes increases plant performance under water excess. Methods In a greenhouse experiment, we evaluated the differential performance of young endophyte-infected and endophyte-free tall fescue plants in response to 14days of partial and total submergence. We included a wild local population and a cultivar, each with their respective fungal endophyte: the common endophyte and a safe (non-toxic) endophyte (AR584). Key results Relative to control (non-submerged) plants, and regardless of endophyte status, total submergence resulted in a significant growth reduction. At the end of the partial submergence period, the number of leaves per plant increased (21%) in the presence of the safe endophyte AR584 but decreased (18%) in the presence of the wild endophyte. Moreover, under partial submergence, the presence of wild endophyte decreased pseudostem dry weight by 10%. Conclusions Our results show that the presence of either the wild or the safe endophyte did not increase the performance of young tall fescue plants under submergence conditions. Implications Although all endophyte-free and endophyte-infected tall fescue plants survived submergence treatments, we cannot rule out that Epichloë endophytes might improve plant fitness under longer stressful submergence conditions. Future research should explore how endophytes modulate host performance under water excess, considering different phenological plant phases and/or co-occurrence with other stress factors (e.g. high temperatures).

Forecasts of species range shifts as a result of climate change are essential, because invasions by exotic species shape biodiversity and therefore ecosystem functions and services. Ecologists have focused on propagule pressure (for example, the number of individuals and invasion events), the characteristics of an invading species, and its new abiotic and biotic environment to predict the likelihood of range expansion and invasion. Here, we emphasize the role of photoperiodic response on the range expansion of species. Unlike temperature, the latitudinal gradient of seasonal changes in day length is a stable, abiotic environmental factor that does not change with local or global climate. Predicting range expansions across latitudes and the subsequent consequences for native communities requires a more comprehensive understanding of how species use day length to coordinate seasonal growth, reproduction, physiology and synchronization of life cycles with interacting individuals and species.

Tree establishment can have multiple effects on the production and biodiversity of rangelands. In mixed (C3–C4) grasslands, winter deciduous trees could favor cold-season species in the understory, improving forage availability in the most critical time of the year. Yet, they could also promote local extinctions and invasions, risking native biodiversity. We evaluate the effect of poplar planting on the structure, composition, and diversity of native grasslands in the Flooding Pampas of Argentina using a network of 9 pairs of adjacent nonafforested and afforested stands (age: 23–25 years, density: 625–1 111 plants ha−1) located in different topographic positions. Phytosociological surveys, basal cover measurements, and tree volume were performed at all stands. Live plant cover was 42% lower under poplars (P< 0.05). Litter cover followed an opposite trend leaving bare soil proportions unchanged with afforestation. Afforested stands had a higher proportion of C3 species compared with nonafforested ones. Little evidence of local extinctions or invasions with afforestation was found. Poplar understories had significantly higher nonnative species cover but similar numbers and lower species diversity (Shannon–Weaver index) yet similar species richness when compared with their nonafforested counterparts. Beyond the diversification of ranch outputs, deciduous tree plantations in the Flooding Pampas can offer a good forage source in their understory that complements nonafforested natural grasslands in quality and seasonality.