The year is 2042, Oprah Winfrey is president of the United States, the balance between man and Earth has been rightfully restored, and it has been a long two years since you graduated from university. Only one of these statements seems unrealistic, and I can tell you it is NOT the one about Oprah. Your mother is recently very proud of you because you aren't sleeping on your twin-sized Buzz Lightyear sheets at home anymore. You have secured a respectable job that allows you to pay back those hefty student loans in addition to putting some cash towards a proper vacation once the summer rolls around. A lot of hard work and sleepless nights have gone into the past few years of trying to get to where you are now, so you want to take a vacation to relax and unwind. A national park camping trip in California sounds nice, but so does a tropical beach trip in Cambodia. Getting away from the never-ending stress of everyday life to the serene outdoors sounds like the sweetest- and most rewarding- dream. However, the sad truth about the year 2042 is that many vacation destinations have fallen victim to steady habitat fragmentation and destruction due to growing popularity of Earth's natural wonders. So, while you wanted to zip-line through a tropical forest in the middle of July, you could potentially just be zip-lining over: log cabins, winding roads, themed restaurants, and the tiny remnants of what is left of that tropical forest.
Anthropogenic habitat fragmentation, as I discussed in my first post, is happening at a more rapid rate than effected populations can adapt to (Lienert, J. 2004) and has major impacts on plant-pollinator interactions. Fragmentation can put a major damper on the health and biodiversity most ecosystems are trying to maintain. This has been shown especially true when reviewing the important interactions between pollinators and their plants. So, throughout this paper I will discuss how fragmented habitats impact pollination patterns.
LONG DISTANCE RELATIONSHIPS
Long distance relationships are hard. Whether your (human) partner lives halfway across the country or (your plant partner) is just across I-40 and Turkey Creek. When I think of pollinators and land disruption, the first thing that pops into my mind is the increase in distance that the pollinator will have to travel to get these plants. Three of the studies relayed that bees, butterflies, and moths can fly over long distances to food sources. However, there was a study that noted male bees could not make it across a fragmented landscaped of 100 meters, so the data really varies from study to study (Didham et al. 1996). Below the graph on the left depicts pollinator visits in two different areas of a forest (Valdivia 2011). We can see that in this study there were far less visits at the edges of the fragmented forest than in the connected mainland. On the right we can see lack of fruit and seed growth in plants depending on their location in a fragmented forest (Valdivia 2011).
Likewise, three of the papers showed a decrease in "the most common pollinator" and as you got closer to the edges of these fragmented landscapes, the plants there were visited less often and in one study these plants exhibited a smaller fruit and seed set (Steffan-Dewenter, Ingolf and Teja, Tscharntke. 2002). Carlos Valdivia noted from his study that plants at the edges of the forest patch have larger petals and foliar displays than flowers on the mainlands, and even with a larger display, they still receive less traffic. The effects of fragmentation and lack of pollination over patches of habitat do not bode well for plant-pollinator interactions.
SPECIALIZATION IN PLANT + POLLINATOR INTERACTION
Plants are pollinated in many different ways. They can cross-pollinate by wind, water, or use animals for fertilization. Wind and water pollination make up a much smaller percentage by which plants reproduce, but they are worth mentioning. The reason that animal or insect pollination is particularly cardinal is because plants and their pollinators have co-evolved as long as plants and animals have interacted, and in this fact, many plants have intricate structures made especially for a particular type of pollinator. Plants are often visited by multiple species of pollinator, "but a critical level of pollinator species richness is needed for successful pollination and maintenance of diverse plant communities" (Steffan-Dewenter, Ingolf and Teja, Tscharntke. 2002). And according to one of the studies, if a plant is thriving from the pollination of a small set of species, it would be more difficult for that plant and that pollinator to survive in a fragmented environment (Skogen et al. 2016).
If a species of plant is pollinated by a specialized insect or animal, then the problem of separation and decline in plant number can elicit a significant change in pollinator population number. These pollinators require a certain amount of pollen, nectar, and nesting sites to be provided by their environment in order to survive, and if their environment is being disturbed or destroyed, some of their previously supplied resources may be in limited amounts (Steffan-Dewenter, Ingolf and Teja, Tscharntke. 2002). Oftentimes, a generalist can swoop in and take over for the previous pollinator, but new pollinators may not be as effective (Kwak et al. 1998). If the insect or animal is not a generalist species, then it will have two choices: the pollinator can look for a new species of plant to feed from, or it can die off.
Pollinators are important drivers of diversity in the ecosystem by providing a mutualistic relationship to crops and wild plants all around the globe (Potts et al. 2010). Two out of eight papers noted, roughly 80% of all flowering plants reproduce with the help of an animal pollinator. So naturally, in a fragmented habitat, the loss of plants and plant diversity can lead to a major change in pollinator abundance and diversity. Lots of insects are tied to specific plants, for instance the monarch butterfly and milkweed plants. Monarchs use these plants to feed on in order to grow. If there is no milkweed, there is no monarch. These interactions are important to take note of because the effects can impact all humans on many levels. We depend on plants as a source of oxygen, for nutrients, to feed animals that we eventually eat, and we also depend on plants for recreational purposes. I mean, what would the back porch of a cabin be without a full forest to drink your morning coffee to?
Four of the eight sources explicitly note that more research needs to be done on the topic of plant-pollinator interactions specifically in disturbed habitats. Much of the literature shows that both variables are affected, but a lot of the results are varied and it is also possible that some of the results are due to abiotic factors inhibiting plant growth.
TAKEAWAYS
The major takeaways that I got from my research is that: 1. we should do our best to preserve the natural land that we still have and come up with plans to help communities impacted by fragmentation, 2. more experiments need to be conducted on plant-pollinator interactions in these disturbed environments, and 3. we should take a pledge to elect Oprah as president in 2040.
WORKS CITED
Didham, Raphael K., Jaboury Ghazoul, Nigel E. Stork, and Andrew J. Davis. "Insects in fragmented forests: a functional approach." Trends in Ecology & Evolution 11.6 (1996): 255-60.
Ferreira, Patrícia Alves, Danilo Boscolo, and Blandina Felipe Viana. "What do we know about the effects of landscape changes on plant–pollinator interaction networks?" Ecological Indicators 31 (2013): 35-40.
Kwak, Manja M., Odilia Velterop, and Jelte Van Andel. "Pollen and gene flow in fragmented habitats." Applied Vegetation Science 1.1 (1998): 37-54. JSTOR.
Lienert, J. 2004. Habitat fragmentation effects on fitness of plant populations – a review. Journal for Nature Conservation 12:53–72.
Potts, Simon G., Jacobus C. Biesmeijer, Claire Kremen, Peter Neumann, Oliver Schweiger, and William E. Kunin. "Global pollinator declines: trends, impacts and drivers." Trends in Ecology & Evolution 25.6 (2010): 345-53.
Skogen, K. A., T. Jogesh, E. T. Hilpman, S. L. Todd, M. K. Rhodes, S. M. Still, and J. B. Fant. "Land-use change has no detectable effect on reproduction of a disturbance-adapted, hawkmoth-pollinated plant species." American Journal of Botany 103.11 (2016): 1950-963.
Steffan-Dewenter, Ingolf, and Teja Tscharntke. "Insect communities and biotic interactions on fragmented calcareous grasslands—a mini review." Biological Conservation 104.3 (2002): 275-84.
Valdivia, Carlos. "Negative effects of forest fragmentation and proximity to edges on pollination and herbivory of Bomarea salsilla (Alstroemeriaceae)." Plant Ecology and Evolution 144.3 (2011): 281-87.
Picture: https://abinashpadhi.wordpress.com/2011/06/30/butterflies-in-hobbs-state-park-arkansas/
