Plasticity of flower longevity in alpine plants is increased in populations from high elevation compared to low elevation populations

Abstract

Flower longevity is an adaptive trait, optimized to balance reproductive success against the costs of flower maintenance. The trait is highly plastic in response to pollination success, and numerous studies report increased flower longevity in high elevation environments, where diversity, abundance, and activity of pollinators are low. However, few studies have experimentally investigated how flower longevity varies with pollination intensity within and among populations. We studied flower longevity of six alpine species under three pollination intensity treatments (hand-pollination, natural pollination, pollinator exclusion) at 1600 m vs. 2600 m a.s.l. at the Furka Pass, Central Swiss Alps. We hypothesized, (1) that flower longevity is generally increased in population at high elevation, and (2) that the increase in flower longevity when pollination fails is stronger in populations at high elevation compared to low elevation. Hand-pollination did not decrease flower longevity in any of the studied populations and rarely increased natural seed production suggesting no pollination limitation at both elevations. This was supported by similar pollinator visitation rates, pollinator efficiency, and pollination effectivity. Pollinator exclusion significantly increased flower longevity, but only in populations of three species at low elevation, whereby in all populations of the six species at high elevation, indicating a higher plasticity of flowers in populations at high elevation compared to populations from lower elevation. We suggest that the higher plasticity of flower longevity in alpine populations is of advantage in their unpredictable pollination environment: Increased flower longevity compensates for low pollination in unsuitable periods guaranteeing a minimum reproduction, while the capacity to senescence rapidly after successful pollination saves redundant floral costs in suitable periods.

Plastic Responses Contribute to Explaining Altitudinal and Temporal Variation in Potential Flower Longevity in High Andean Rhodolirion montanum

“…Finally the literature reveals a number of cases where flower longevity has been studied in pollinator-excluded flowers over an altitudinal gradient that show no or very little altitudinal increase in potential flower longevity [17,36,37]. Including our results in R .…”

“…First, pollination rates decline with decreasing temperatures and more unpredictable weather conditions at higher altitudes [1–11]. Second, flower longevity often increases with altitude [5,6,12–17], there being outstanding cases of nival plants with extremely long-lived stigmas [18,19]. The above two trends are considered to be functionally linked, with longer-lived flowers compensating for lower pollination rates at higher elevations [5,6,13].…”

Ovule bet‐hedging at high elevation in the South American Andes: Evidence from a phylogenetically controlled multispecies study

“…Present knowledge, based on a relatively small and geographically biased sample of species, suggests around 50% of alpine species are pollen‐limited García‐Camacho and Totland (). However, very few studies have measured pollen limitation across the alpine gradient over the entire flowering season (Arroyo et al, ; Straka, & Starzomski, ; Trunschke & Stöcklin, ). Moreover, the alpine gradient involved are often fairly short leading to the risk of confounding effects of slope/aspect and local topography on elevational trends.…”

Context‐dependency of resource allocation trade‐offs highlights constraints to the evolution of floral longevity in a monocarpic herb

“…Floral longevity also can be influenced by abiotic conditions such as water availability, altitude and temperature (e.g. Vesprini & Pacini, 2005;Arroyo et al, 2013;Jorgensen & Arathi, 2013;Spigler & Kalisz, 2013;Trunschke & Stocklin, 2017). Consideration of the plasticity of floral longevity in response to resource availability may be particularly important regarding the evolution of floral longevity as a type of resource allocation strategy.…”