Genetic connectivity is crucial in rapidly changing environments as it allows exchange and dispersal of adaptive genes among plant populations. Matter et al. study patterns of historic gene flow, flowering phenology and contemporary pollen flow in two common herbs, Ranunculus bulbosus and Trifolium montanum, along an altitudinal gradient of 1200–1800 m a.s.l. among alpine meadows in Switzerland, a habitat type thought to be particularly sensitive to climate change. They determine that pollen-flow along the gradient is extensive, explaining the very low genetic differentiation along the mountain slope. Congruent with this finding, they find that despite the delay in flowering caused by altitude, the overlap in flowering periods is large enough to allow for extensive pollen dispersal between populations.
Co-flowering species can either compete for pollination services, have no effect on one another or facilitate one another by attracting more pollinators. Landry studies two mangrove species with overlapping flowering phenologies, Avicennia germinans and Laguncularia racemosa, in southern Florida and finds that when they co-flower A. germinans out-competes L. racemosa for pollinators. Hermaphrodites of L. racemosa self-pollinate autogamously when not visited by insects, so reduced visitation to their flowers reduces the frequency of outcrossing. Reduced outcrossing limits male reproductive success in this androdioecious species, which could lead to changes in the breeding system. The degree of overlap in flowering phenologies varies between years, so the effect on the mating and breeding system may differ between years.
Delayed reproduction in soils with low phosphorus (P) availability is common among annuals, in contrast to the accelerated reproduction typical of other low-nutrient environments. Nord et al. present a two-resource dynamic allocation model of plant growth and reproduction for Arabidopsis thaliana that incorporates growth, respiration, and carbon and P acquisition of both root and shoot tissue, and considers the reallocation of resources from senescent leaves. The model suggests that delayed reproduction in response to low P availability may be reduced in plants adapted to environments where P mobility is greater.
Damage to cotyledons can have significant effects on subsequent plant growth and reproduction. Studying the annual species Medicago lupulina, Zhang et al. examine the mechanisms linking cotyledon damage and fitness, as measured by growth and reproductive traits. They show how a network of indirect mechanisms links cotyledon damage and fitness, with the strongest effects being from a reduction in plant size that reduces flower number and, in turn, seed number.