Local Adaptation in Populations of Arabis alpina
(2024) BION03 20231Degree Projects in Biology
- Abstract
- Plant-pollinator interactions are considered one of the primary factors driving the large diversity in floral traits. Adaptive floral trait diversification occurs when different pollinators show preference for different floral phenotypes imposing selection on, and potentially generating local adaptation, of floral traits in populations that interact with different insect communities. Plants in generalized pollination systems, which are very common in nature, are thus likely under a net gradient of selection, which combines the selective effects of several pollinators interacting with the flowers. Further, coevolutionary relationships suggest that the local plant population can exert selective pressures on its insect visitors. Studies... (More)
- Plant-pollinator interactions are considered one of the primary factors driving the large diversity in floral traits. Adaptive floral trait diversification occurs when different pollinators show preference for different floral phenotypes imposing selection on, and potentially generating local adaptation, of floral traits in populations that interact with different insect communities. Plants in generalized pollination systems, which are very common in nature, are thus likely under a net gradient of selection, which combines the selective effects of several pollinators interacting with the flowers. Further, coevolutionary relationships suggest that the local plant population can exert selective pressures on its insect visitors. Studies investigating pollinator-mediated selection have largely focused on visual/morphological floral traits and specialist systems, where local adaptation and divergence of phenotypes are easier to follow. Here, I use the model plant Arabis alpina, which is pollinated by many different kinds of insects, to investigate to what extent seven populations that diverge in floral scent composition show evidence of local adaptation to each local pollinator community. Through pollinator visitation data, I found distinct insect communities across the populations. To examine the possibility of local adaptation to floral fit traits, I compared the proboscis lengths of the local insect communities to the corolla length across seven different populations. The range of proboscis lengths and corolla lengths in each population overlapped to varying extents, showing no significant evidence of trait-matching. Instead, using a translocation experiment, I found that the local insect community showed preference for local A. alpina flowers over foreign flowers. Collectively, my results suggest that there is local adaptation in the A. alpina populations in relation to the local insect community, although floral advertisement traits (i.e. floral scent) show stronger alignment with the local pollinator community than the fit traits. Further research will help to determine the likely direction of selection which has led to the diverging scent profiles, and the importance of isolated olfactory cues in attracting the local pollinator community. (Less)
- Popular Abstract
- Why do they smell different?
Arabis alpina is a small herbaceous plant that grows in mountainous environments all over Europe, and into Africa and Asia. We worked with seven populations in central Italy, which have been shown to have different floral scent compositions. We hypothesized that these differences in floral scent might be a result of pollinator-mediated natural selection. Many studies have shown that pollinators can have specific preferences in floral traits like shape, colour and scent. When they visit flowers with traits matching their preferences, the flowers are pollinated and can produce. So, the different A. alpina populations might have different scents because the local pollinators who visit them might have different... (More) - Why do they smell different?
Arabis alpina is a small herbaceous plant that grows in mountainous environments all over Europe, and into Africa and Asia. We worked with seven populations in central Italy, which have been shown to have different floral scent compositions. We hypothesized that these differences in floral scent might be a result of pollinator-mediated natural selection. Many studies have shown that pollinators can have specific preferences in floral traits like shape, colour and scent. When they visit flowers with traits matching their preferences, the flowers are pollinated and can produce. So, the different A. alpina populations might have different scents because the local pollinators who visit them might have different preferences.
To check my hypothesis, I first conducted pollinator observations. I watched a patch of flowers in each population for an hour at a time, and counted how many flowers each pollinator species visited in the patch. Many bouts of observations helped me calculate a visitation rate for each species in every population. Using this information I statistically compared the visiting insect community composition across the populations. Although there was some overlap between populations, I found that the pollinator communities were distinct across the different regions.
I then investigated if the morphology of the local pollinator community matched with local flower’s morphology. I compared the tongue lengths of different insect species with the flower tube length in each population. I found that overlap between these morphological measurements varied to different extents across populations. Overall, it did not seem like there was much trait matching in terms of the fit between the local pollinators and the flowers.
Shape or smell?
Since the insects did not show local adaptation to the morphology of the flower, I instead checked if they were adapted to the scent. I paired populations with very different scent composition, and exchanged flowering scapes between them. Then, the local insect community was exposed both to local and foreign flowers. I compared the total visitation rate to each category, and found that pollinators visited local flowers
more often than foreign ones, suggesting that they prefer the local floral scent!
Although I did not find that insects match with the morphology of the local flowers, they definitely showed preference for the local floral scent. This could be because the local insect community has learned to associate the local floral scent with nectar rewards, but it could also be that different A. alpina populations have adapted their scent to match the innate preferences of the local insect community. In situations like this, the direction of selection is difficult to ascertain, without targeted studies. Overall, my thesis helps us appreciate how sensitive and locally fine-tuned these ecological interactions may be, especially considering the rapidly changing conditions of our natural world.
Master’s Degree Project in Biology, 60 credits, 2023-24
Department of Biology, Lund University
Advisor: Magne Friberg
SPeciation, Adaptation & Co-Evolution (SPACE) Research Group (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9154642
- author
- Susheel, Aarushi
- supervisor
- organization
- course
- BION03 20231
- year
- 2024
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9154642
- date added to LUP
- 2024-05-27 14:38:03
- date last changed
- 2024-05-27 14:38:03
@misc{9154642,
abstract = {{Plant-pollinator interactions are considered one of the primary factors driving the large diversity in floral traits. Adaptive floral trait diversification occurs when different pollinators show preference for different floral phenotypes imposing selection on, and potentially generating local adaptation, of floral traits in populations that interact with different insect communities. Plants in generalized pollination systems, which are very common in nature, are thus likely under a net gradient of selection, which combines the selective effects of several pollinators interacting with the flowers. Further, coevolutionary relationships suggest that the local plant population can exert selective pressures on its insect visitors. Studies investigating pollinator-mediated selection have largely focused on visual/morphological floral traits and specialist systems, where local adaptation and divergence of phenotypes are easier to follow. Here, I use the model plant Arabis alpina, which is pollinated by many different kinds of insects, to investigate to what extent seven populations that diverge in floral scent composition show evidence of local adaptation to each local pollinator community. Through pollinator visitation data, I found distinct insect communities across the populations. To examine the possibility of local adaptation to floral fit traits, I compared the proboscis lengths of the local insect communities to the corolla length across seven different populations. The range of proboscis lengths and corolla lengths in each population overlapped to varying extents, showing no significant evidence of trait-matching. Instead, using a translocation experiment, I found that the local insect community showed preference for local A. alpina flowers over foreign flowers. Collectively, my results suggest that there is local adaptation in the A. alpina populations in relation to the local insect community, although floral advertisement traits (i.e. floral scent) show stronger alignment with the local pollinator community than the fit traits. Further research will help to determine the likely direction of selection which has led to the diverging scent profiles, and the importance of isolated olfactory cues in attracting the local pollinator community.}},
author = {{Susheel, Aarushi}},
language = {{eng}},
note = {{Student Paper}},
title = {{Local Adaptation in Populations of Arabis alpina}},
year = {{2024}},
}