Pollinator-flower interactions in gardens during the COVID-19 pandemic lockdown of 2020

During the main COVID-19 global pandemic lockdown period of 2020 an impromptu set of pollination ecologists came together via social media and personal contacts to carry out standardised surveys of the flower visits and plants in gardens. The surveys involved 67 rural, suburban and urban gardens, of various sizes, ranging from 61.18° North in Norway to 37.96° South in Australia, resulting in a data set of 25,174 rows, with each row being a unique interaction record for that date/site/plant species, and comprising almost 47,000 visits to flowers, as well as records of flowers that were not visited by pollinators, for over 1,000 species and varieties belonging to more than 460 genera and 96 plant families. The more than 650 species of flower visitors belong to 12 orders of invertebrates and four of vertebrates. In this first publication from the project, we present a brief description of the data and make it freely available for any researchers to use in the future, the only restriction being that they cite this paper in the first instance. The data generated from these global surveys will provide scientific evidence to help us understand the role that private gardens (in urban, rural and suburban areas) can play in conserving insect pollinators and identify management actions to enhance their potential

Pollinator-flower interactions in gardens during the covid 19 pandemic lockdown of 2020

During the main COVID-19 global pandemic lockdown period of 2020 an impromptu set of pollination ecologists came together via social media and personal contacts to carry out standardised surveys of the flower visits and plants in gardens. The surveys involved 67 rural, suburban and urban gardens, of various sizes, ranging from 61.18° North in Norway to 37.96° South in Australia, resulting in a data set of 25,174 rows, with each row being a unique interaction record for that date/site/plant species, and comprising almost 47,000 visits to flowers, as well as records of flowers that were not visited by pollinators, for over 1,000 species and varieties belonging to more than 460 genera and 96 plant families. The more than 650 species of flower visitors belong to 12 orders of invertebrates and four of vertebrates. In this first publication from the project, we present a brief description of the data and make it freely available for any researchers to use in the future, the only restriction being that they cite this paper in the first instance. The data generated from these global surveys will provide scientific evidence to help us understand the role that private gardens (in urban, rural and suburban areas) can play in conserving insect pollinators and identify management actions to enhance their potential

Pollinator-mediated selection and the evolution of floral traits in orchids

In this thesis, I combined manipulations of traits and pollination environment with analysis of phenotypic selection to examine causes of variation in strength and mode of selection on floral traits, and I conducted a reciprocal sowing experiment to test for local adaptation in germination success. I tested the following predictions (1) the opportunity for selection, and the strength of pollinator-mediated and net selection increase with increasing pollen limitation, (2) the effects of traits affecting pollinator attraction and traits affecting pollination efficiency are non-additive and this leads to pollinator-mediated correlational selection, (3) the effects of spur length on pollen removal, pollen receipt, and female fitness differ between populations with short-tongued and populations with long-tongued pollinators, and (4) local adaptation at the stage of germination contributes to the maintenance of ecotypes growing in grasslands and woodlands, respectively. A study including natural populations of 12 orchid species that varied widely in pollen limitation showed that opportunity for selection, pollinator-mediated selection and net selection were all positively related to pollen limitation, whereas non-pollinator-mediated selection was not. In the moth-pollinated orchid Platanthera bifolia, experimental reductions of plant height and spur length decreased pollen removal, pollen receipt and fruit production, but non-additive effects were not detected. Effects of plant height translated into pollinator-mediated selection for taller plants via female fitness, but there was no current pollinator-mediated selection on spur length. An experiment using artificial nectar spurs demonstrated that in P. bifolia pollen receipt saturated at shorter spur length in a population with short-tongued pollinators than in a population with a long-tongued pollinator. Effects of spur length on pollen receipt did not translate into current pollinator-mediated selection indicating that also plants with the shortest spurs for the most part received sufficient pollen for full seed set. Reciprocal sowing of seeds from grassland and woodland populations detected no evidence of local adaptation at the germination stage between ecotypes of P. bifolia. Taken together, the results illustrate how a combination of trait manipulation and analysis of strength and causes of selection can throw light on both the functional and adaptive significance of trait variation within and among natural populations

Pollinator-mediated selection and the evolution of floral traits in orchids

In this thesis, I combined manipulations of traits and pollination environment with analysis of phenotypic selection to examine causes of variation in strength and mode of selection on floral traits, and I conducted a reciprocal sowing experiment to test for local adaptation in germination success. I tested the following predictions (1) the opportunity for selection, and the strength of pollinator-mediated and net selection increase with increasing pollen limitation, (2) the effects of traits affecting pollinator attraction and traits affecting pollination efficiency are non-additive and this leads to pollinator-mediated correlational selection, (3) the effects of spur length on pollen removal, pollen receipt, and female fitness differ between populations with short-tongued and populations with long-tongued pollinators, and (4) local adaptation at the stage of germination contributes to the maintenance of ecotypes growing in grasslands and woodlands, respectively. A study including natural populations of 12 orchid species that varied widely in pollen limitation showed that opportunity for selection, pollinator-mediated selection and net selection were all positively related to pollen limitation, whereas non-pollinator-mediated selection was not. In the moth-pollinated orchid Platanthera bifolia, experimental reductions of plant height and spur length decreased pollen removal, pollen receipt and fruit production, but non-additive effects were not detected. Effects of plant height translated into pollinator-mediated selection for taller plants via female fitness, but there was no current pollinator-mediated selection on spur length. An experiment using artificial nectar spurs demonstrated that in P. bifolia pollen receipt saturated at shorter spur length in a population with short-tongued pollinators than in a population with a long-tongued pollinator. Effects of spur length on pollen receipt did not translate into current pollinator-mediated selection indicating that also plants with the shortest spurs for the most part received sufficient pollen for full seed set. Reciprocal sowing of seeds from grassland and woodland populations detected no evidence of local adaptation at the germination stage between ecotypes of P. bifolia. Taken together, the results illustrate how a combination of trait manipulation and analysis of strength and causes of selection can throw light on both the functional and adaptive significance of trait variation within and among natural populations

Pollinator-mediated selection and the evolution of floral traits in orchids

In this thesis, I combined manipulations of traits and pollination environment with analysis of phenotypic selection to examine causes of variation in strength and mode of selection on floral traits, and I conducted a reciprocal sowing experiment to test for local adaptation in germination success. I tested the following predictions (1) the opportunity for selection, and the strength of pollinator-mediated and net selection increase with increasing pollen limitation, (2) the effects of traits affecting pollinator attraction and traits affecting pollination efficiency are non-additive and this leads to pollinator-mediated correlational selection, (3) the effects of spur length on pollen removal, pollen receipt, and female fitness differ between populations with short-tongued and populations with long-tongued pollinators, and (4) local adaptation at the stage of germination contributes to the maintenance of ecotypes growing in grasslands and woodlands, respectively. A study including natural populations of 12 orchid species that varied widely in pollen limitation showed that opportunity for selection, pollinator-mediated selection and net selection were all positively related to pollen limitation, whereas non-pollinator-mediated selection was not. In the moth-pollinated orchid Platanthera bifolia, experimental reductions of plant height and spur length decreased pollen removal, pollen receipt and fruit production, but non-additive effects were not detected. Effects of plant height translated into pollinator-mediated selection for taller plants via female fitness, but there was no current pollinator-mediated selection on spur length. An experiment using artificial nectar spurs demonstrated that in P. bifolia pollen receipt saturated at shorter spur length in a population with short-tongued pollinators than in a population with a long-tongued pollinator. Effects of spur length on pollen receipt did not translate into current pollinator-mediated selection indicating that also plants with the shortest spurs for the most part received sufficient pollen for full seed set. Reciprocal sowing of seeds from grassland and woodland populations detected no evidence of local adaptation at the germination stage between ecotypes of P. bifolia. Taken together, the results illustrate how a combination of trait manipulation and analysis of strength and causes of selection can throw light on both the functional and adaptive significance of trait variation within and among natural populations

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

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

Trunschke et al._EcolEvol_2018_PlantHtSpurLManipulation

Trunschke et al._EcolEvol_2018_PlantHtSpurLManipulatio

Manipulation of trait expression and pollination regime reveals the adaptive significance of spur length

Understanding the mechanisms of adaptive population differentiation requires that both the functional and adaptive significance of divergent traits are characterized in contrasting environments. Here, we (a) determined the effects of floral spur length on pollen removal and receipt using plants with artificial spurs representing the species‐wide variation in length, and (b) quantified pollinator‐mediated selection on spur length and three traits contributing to floral display in two populations each of the short‐spurred and the long‐spurred ecotype of the orchid Platanthera bifolia. Both pollen receipt and removal reached a maximum at 28–29 mm long spurs in a short‐spurred population visited by short‐tongued moths. In contrast, pollen receipt increased linearly across the tested range (4–52 mm) and pollen removal was unrelated to spur length in a long‐spurred population predominantly visited by a long‐tongued moth. The experimentally documented effects on pollen transfer were not reflected in pollinator‐mediated selection through female fitness or pollen removal indicating that the natural within‐population variation in spur length was insufficient to result in detectable variation in pollen limitation. Our study illustrates how combining trait manipulation with analysis of causes and strength of phenotypic selection can illuminate the functional and adaptive significance of trait expression when trait variation is limited

Data from: The independent and combined effects of floral traits distinguishing two pollination ecotypes of a moth-pollinated orchid

Identifying traits and agents of selection involved in local adaptation is important for understanding population divergence. In southern Sweden, the moth-pollinated orchid Platanthera bifolia occurs as a woodland and a grassland ecotype that differ in dominating pollinators. The woodland ecotype is taller (expected to influence pollinator attraction) and produces flowers with longer spurs (expected to influence efficiency of pollen transfer) compared to the grassland ecotype. We examined whether plant height and spur length affect pollination and reproductive success in a woodland population, and whether effects are non-additive, as expected for traits influencing two multiplicative components of pollen transfer. We reduced plant height and spur length to match trait values observed in the grassland ecotype and determined the effects on pollen removal, pollen receipt, and fruit production. In addition, to examine the effects of naturally occurring variation, we quantified pollinator-mediated selection through pollen removal and seed production in the same population. Reductions of plant height and spur length decreased pollen removal, number of flowers receiving pollen, mean pollen receipt per pollinated flower, and fruit production per plant, but no significant interaction effect was detected. The selection analysis demonstrated pollinator-mediated selection for taller plants via female fitness. However, there was no current selection mediated by pollinators on spur length, and pollen removal was not related to plant height or spur length. The results show that, although both traits are important for pollination success and female fitness in the woodland habitat, only plant height was sufficiently variable in the study population for current pollinator-mediated selection to be detected. More generally, the results illustrate how a combination of experimental approaches can be used to identify both traits and agents of selection

Trunschke et al._EcolEvol_2018_PlantHtSpurLSelection_pollen removal

Trunschke et al._EcolEvol_2018_PlantHtSpurLSelection_pollen remova