Invasive plants and water availability mediate outcomes of plant-pollinator interactions

Animal pollination occurs in more than three quarters of all flowering plants. These plant-pollinator interactions can be greatly affected by the environment. The increasing presence of invasive species and changes to abiotic conditions could change the outcomes of plant-pollinator interactions. This dissertation focused on identifying how invasive plants and changes to water availability influence seed production and pollinator-mediated selection. The first chapter demonstrated how water availability to pollen recipient plants (Phacelia parryi) as well as conspecific and heterospecific pollen (the invasive plant, Brassica nigra) donors interacted to influence seed production. In this experiment, water availability to recipient plants did not influenced seed production. High-water availability to conspecific pollen donors led to higher seed production. Water availability to heterospecific pollen donors set the context for how water given to conspecific donors and recipient plants impacted seed production. These results show the potential impacts that environmental heterogeneity has on post-pollination events that lead to seed production. The second chapter explored how water availability influences the shape of the relationship between seeds and pollen received. Water availability influenced the pollen-to-seed relationship and the degree to which seed production is limited by pollen quantity. Data for chapters one and two were collected through a series of hand-pollination experiments done in a pollinator-free greenhouse. The third chapter documented the impacts that the presence of an invasive plant (Linaria vulgaris) across years had on pollinator visitation and pollinator-mediated selection on floral traits in a native plant species (Penstemon strictus). This was done through a multi-year field experiment in Colorado, USA. The presence of Linaria increased pollinator visits to Penstemon. Both pollinator preferences and the relationship between pollinator visits and seed production changed across years. Together, this work documents two previously-unknown mechanisms on how seed production can be influenced by water to pollen donors and to a change in the pollen-to-seed relationship. This work also illustrates how year-to-year variation in plant-pollinator interactions and the presence of a plant invader affects pollinator visitation and pollinator-mediated phenotypic selection

Invasive plants and water availability mediate outcomes of plant-pollinator interactions

Animal pollination occurs in more than three quarters of all flowering plants. These plant-pollinator interactions can be greatly affected by the environment. The increasing presence of invasive species and changes to abiotic conditions could change the outcomes of plant-pollinator interactions. This dissertation focused on identifying how invasive plants and changes to water availability influence seed production and pollinator-mediated selection. The first chapter demonstrated how water availability to pollen recipient plants (Phacelia parryi) as well as conspecific and heterospecific pollen (the invasive plant, Brassica nigra) donors interacted to influence seed production. In this experiment, water availability to recipient plants did not influenced seed production. High-water availability to conspecific pollen donors led to higher seed production. Water availability to heterospecific pollen donors set the context for how water given to conspecific donors and recipient plants impacted seed production. These results show the potential impacts that environmental heterogeneity has on post-pollination events that lead to seed production. The second chapter explored how water availability influences the shape of the relationship between seeds and pollen received. Water availability influenced the pollen-to-seed relationship and the degree to which seed production is limited by pollen quantity. Data for chapters one and two were collected through a series of hand-pollination experiments done in a pollinator-free greenhouse. The third chapter documented the impacts that the presence of an invasive plant (Linaria vulgaris) across years had on pollinator visitation and pollinator-mediated selection on floral traits in a native plant species (Penstemon strictus). This was done through a multi-year field experiment in Colorado, USA. The presence of Linaria increased pollinator visits to Penstemon. Both pollinator preferences and the relationship between pollinator visits and seed production changed across years. Together, this work documents two previously-unknown mechanisms on how seed production can be influenced by water to pollen donors and to a change in the pollen-to-seed relationship. This work also illustrates how year-to-year variation in plant-pollinator interactions and the presence of a plant invader affects pollinator visitation and pollinator-mediated phenotypic selection

Water availability affects the relationship between pollen intensity and seed production.

Seed production can be affected by water availability and also depend on the amount (pollen intensity) and quality of pollen deposited. The way pollen receipt on the stigma translates into seeds produced follows that of a saturating dose-response. Not only can water availability and pollen intensity each influence seed production, these factors could interact in their effects on seed production. Changes to the relationship between seed production and pollen intensity can in turn influence pollinator effectiveness and pollinator-mediated selection. We asked how water availability affected indices of plant fitness (seed set, fruit set and seed mass) and the relationship between pollen intensity and seed production in Phacelia parryi. We conducted a greenhouse experiment where we manipulated water availability (either high- or low-water) to pollen recipient plants and hand-pollinated each plant with a range of pollen intensities. We conducted 703 hand-pollinations on 30 plants. For each hand-pollinated flower we measured pollen deposited, seed production and seed mass. We then generated a piecewise regression of the relationship between pollen intensity and seed production, and determined average effects of water on plant fitness measures. This experiment was paired with a field observational study aimed to document natural variation in pollen deposition. Average seed production per fruit was 21 % higher in the high-watered plants. The relationship between pollen intensity and seed production differed between the two water treatments. Plants under high-water exhibited a wider range in which pollen deposition increased seed production. Average natural pollen intensities fell within different regions of the piecewise regression for low- and high-water plants. Water availability can alter the efficiency by which pollen received is translated into seeds produced. Our greenhouse data suggest that only under certain pollen intensity environments will water availability affect how pollen received is translated into seeds produced

Pollination and Infection through the Lens of a Meta Analysis

Pollination is essential for crops and many other flowering species. Parasites of pollinators could influence the future of pollination and flowering plants. A meta-analysis is a useful strategy to detect patterns across different studies collecting data on a similar subject. I will present results from a meta-analysis to determine how pollination is affected by pollinators infected with parasites.The project’s data collection required keywords, finding, downloading, and reading research articles that discussed the impacts of parasites on insect pollinators. Data needed an infected insect pollinator, compared to an uninfected counterpart. Both entries must display the mean and standard error. Out of the literature papers downloaded, only 3.5 percent contained usable data. Over 1,000 different lines of data were extracted from the literature of 74 papers. The two most common insects were bees in the arthropod genera Apis and Bombus, which accounted for 23.5 percent of the study observations. The affected traits due to parasitization varied from behavioral, density, morphological, and physiological. Meta analysis determined that population density was the trait most impacted by parasitization, making up 53.5 percent of observations. Given the importance of pollinator populations for flowering plants, it is critical to measure the affected changes in pollinator population density. Our results predict that as the pollinator density is negatively affected by parasites, in turn, pollination will be affected, and therefore, important flowering plant species will be impacted. Furthermore, we found correlations that reinforce the importance of parasitism and its effects on flowering plant species

Monarchs, Milkweeds, Modeling: How Climate Change Will Affect Species Distribution in Florida

Monarch Butterflies (Danaus plexippus) are predicted to go quasi-extinct within the next 20 years. Pesticides, pathogens, habitat loss, and the effects of climate change are all driving this charismatic and formerly widespread species towards unsustainably low populations. Climate change is increasingly of concern in terms of Monarch conservation because it exacerbates other factors, particularly, habitat fragmentation and depletion of the Monarch’s host genus, the Asclepias. Monarchs are dependent on Asclepias, commonly known as Milkweeds, for their reproduction and success of multigenerational migrations. Monarch distribution is more limited by Asclepias distribution than by environmental factors; as such, understanding how Asclepias respond to climate change is an important element of Monarch conservation. How climate change will affect Asclepias and Monarch populations in Florida, a major Monarch migratory route, is not fully understood. To investigate this, I built a Species Distribution Model using the modeling program MaxEnt. By modeling the present and future distribution of introduced Asclepias curassavica, Florida natives A. tuberosa and A. perennis, and Monarchs within the state of Florida, I aimed to address how changing environmental conditions would affect the spatial distribution of Monarchs. Preliminary results indicate range reduction for Asclepias species, with the potential for local extinctions of A. currasavica and A. incarnata within Florida. Further analysis will explore questions as to which host plants will be used by future monarch populations and investigate trends in terms of the directionality of range change

Unraveling the ecological and evolutionary impacts of a plant invader on the pollination of a native plant

Interactions between a native plant species and its pollinators, herbivores, or microbiome can be affected by the presence of non-native plant species. Non-native plant species are altering plant-pollinator interactions, yet we know little about how these non-native species influence natural selection. In addition, year-to-year variation in flowering could influence the impacts of non-native species on reproductive success in native plants and the strength and direction of pollinator-mediated selection. We examined whether the presence of the highly invasive plant Linaria vulgaris influenced average pollinator visitation, species composition of floral visitors, or pollinator-mediated selection in the native Penstemon strictus. In the field, we conducted small scale L. vulgaris inflorescence removals, that were repeated through 3 years. Pollinator-mediated selection on the floral trait of platform length was examined by determining the relationships between platform length and visitation, between visitation and seed production, and by calculating net selection based on seed production. We found that the presence of L. vulgaris on a small spatial scale facilitated pollinator visitation rates to P. strictus but did not influence pollinator-mediated selection on platform length. Pollinator visitation varied across years, as did the relationship between seed production and pollinator visitation, and the relationship between pollinator visitation and platform length. Although components of selection varied across years, no net selection on platform length was detected in any of the 3 years. Our results show how the presence of an invasive plant and year-to-year variation in plant-pollinator interactions affect the pollination and components of pollinator-mediated selection in native plants