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Aims Positive plant interactions can promote higher species density of beneficiary species in deserts. However, there is limited evidence examining the trait sets of seeds from beneficiary species. In this study, we examined the hypothesis that shrubs (benefactors) influence the germination of desert annuals (beneficiaries) and promote ecotypic differentiation by generating distinct microhabitats through abiotic stress amelioration. The following predictions were tested using growth chambers and field-collected seeds: (i) seed mass and viability will be greater and less variable for seeds collected from within shrub understory relative to seeds from open microhabitats, (ii) germination of seeds from shrub and open microhabitats will be greatest under simulated home (source) conditions, (iii) seeds from the shrub microhabitat will adaptively accelerate their germination rate when germinated in simulated home (source) microhabitats relative to their simulated away (reciprocal) microhabitat. Methods Seeds and their associated maternal plants were collected from four annual species found within a shrub understory (Larrea tridentata) and open microhabitats in the Mojave Desert of California (35.30°N, 117.26°W, 793 m. a.s.l.), and then reciprocally germinated in growth chambers simulating both microclimatic conditions. Cumulative germination and germination rate was measured every 4-5 days for 42 days. Important Findings There was no significant difference in the mean or coefficient of variation for seed mass and viability between the shrub and open microhabitats. The source of the seeds did not significantly impact the cumulative germination, and there was no accelerated rate of germination within potential species ecotypes thereby suggesting no ecotypic differentiation. Cumulative germination was significantly higher within the shrub-simulated microhabitat for three out of the four species examined. Cumulative germination and germination rate were significantly different between species. Hence, shrubs influence the germination of desert annuals, and the outcome of this interaction is species specific, but shrub microhabitats do not necessarily alter the more conserved seed biology traits. Future studies should examine the influence of gene flow on beneficiary adaptation and the influence of species-specificity on beneficiary species response to facilitation. [ABSTRACT FROM AUTHOR]

In recent decades, some bumble bee species have declined, including in North America. Declines have been reported in species of bumble bees historically present in Ontario, including: yellow bumble bee (Bombus fervidus) (Fabricus, 1798), American bumble bee (Bombus pensylvanicus) (DeGeer, 1773), and yellow-banded bumble bee (Bombus terricola) (Kirby, 1837). Threats contributing to bumble bee population declines include: land-use changes, habitat loss, climate change, pathogen spillover, and pesticide use. A response to the need for action on pollinator preservation in North America has been to encourage 'bee-friendly' plantings. Previous studies show differences in common and at-risk bumble bee foraging; however, similar data are unavailable for Ontario. Our research question is whether there is a difference in co-occurring at-risk and common bumble bee (Bombus spp.) floral use (including nectar and pollen collection) in protected areas in southern Ontario. We hypothesize that common and at-risk species forage differently, predicting that at-risk species forage on a limited selection of host plants. We conducted a field survey of sites in southern Ontario, using observational methods to determine bumble bee foraging by species. The results of a redundancy analysis show a difference in foraging between common and at-risk bumblebee species. At-risk bumble bee species show a preference for foraging on invasive, naturalized Vicia cracca (tufted vetch). This finding raises the question of how to preserve or provide forage for at-risk bumble bees, when they show an association with an invasive species often subject to control in protected areas. [ABSTRACT FROM AUTHOR]