Author(s): Meredith Hart
Mentor(s): Richard Todd Stafford, Honors College; Joris van de Hamm, Environmental Science and Policy
This project focused on the differences in Formidae species richness, diversity, and composition in rural and urban areas. Taking samples via 24hr pitfall traps from Bull Run Mountain Natural Area Preserve, and 5 different parks in Arlington, the data was analyzed with Kruwaski-Wallis, PERMANOVA, and a permutation test for homogeneity. It was discovered that there was no significant difference in either species richness or beta diversity, but there was a significant difference in ant community between the two sites. The difference in communities displays that ant populations vary between rural and urban landscapes- this means that ecological services vary between each environment, contributing to ecological change. Ants are considered ecological indicators, and as urbanization spreads it is critically important to monitor their presence in urban environments.
Hi everyone my name is Meredith hart and this is my project focusing on adversity in rural and urban areas across northern Virginia. I completed this project over the summer as part of the URSP student scholarship. Here is my abstract, the project focused on the differences in species richness, diversity and composition in rural and urban areas. I took samples by 24-hour pitfall traps in from bull run mountains natural area preserve and five different parks in Arlington and data was analyzed using the Kruskal Wallace, permanova, and a permutation test for homogeneity. I discovered that there was no significant difference in either species richness or beta diversity but there was a significant difference in ant community between the two sites. Because ants are ecological indicators, their presence and communities can indicate different ecological aspects of an environment. This project displayed that populations vary between rural and urban and landscapes, which means the ecological services will vary between each environment, contributing to ecological change. Ants are considered ecological indicators so as urbanization spreads it is critically important to monitor their presence in urban environments. Here is my background and intro: ants are ecological indicators, as I mentioned, which means their presence indicates whether or not an ecosystem will recover from an event of deforestation along with providing valuable resources for an environment the presence of ecological indicators is often a key determinant in whether or not a green space and ecosystem will recover after an event of deforestation. so northern Virginia has experienced a ton of urbanization recently, and examining the environmental impact of continued development has never been more important as we are continuing to see how urbanization affects urban green spaces. Ants are also considered ecosystem engineers; they decompose material, move soil and leaf litter and their density has a positive correlation with other species diversity (until a certain point), so due to their strong influence in their surrounding areas it is really important to monitor communities and species composition across the world and in urban environments to monitor and predict larger environmental trends. This is my methodology um top right we have a map of the Arlington county park system and underneath that is a map of Bull Run Mountains Natural Area Preserve, so you can already see off the bat these areas are pretty ecologically different in that Arlington is super urban and Bull Run mountain it is not- is a natural area preserve. so data was collected once a week from each trapping site and identified five different locations within each trapping site that I would um take from so I left my pitfall traps out for 24 hours and how I did this was each each pitfall trap consisted of three individual sites within the radius of the park so I would take three cups and I would put them about 20 feet apart from each other and then I would use that as my pitfall trap my cup so I compared um sites in Arlington and in Bull Run and I chose pretty ecologically similar sites. I tried to maintain a level of vegetation similarity or if I had a site next to a creek I would choose another site next to a creek um so i used soapy water as the killing agent uh all specimens were cleaned and preserved in ethanol no later than three hours after traps were collected and then i used ants of north America a guide to the genera by Brian fisher and Steven Couvrer to identify them. I used the kruskal-wallis test to determine if there were statistically significant differences between two or more groups of an independent variable, permutation test to see if one or more groups is more variable than the other, permanova to test that um dispersion is the same for all groups. Statistical terms that I’d like to just briefly touch on chi squared if the chi-squared statistic is greater than the degrees of freedom the null hypothesis is rejected um if the p-value is higher than 0.05 we reject the alternative hypothesis, f is the ratio of the two variances so these are my graphs at the top we have Kruskal- wallace graph and at the bottom we have permutation and permanova. So my null hypothesis was that there was no change between the ant communities and species at each level and my alternative hypothesis was that there was a difference, now because I was testing for species composition species richness and um community composition obviously I would have three individual hypotheses for each but that was my overarching hypothesis for the project. so my kruskal-wallis test displayed that there was no significant difference in the species richness so um my chi-squared was only 3.7385 and but we really don’t know if any of that was due to chance so my permutation test for homogeneity has shown no significant difference in beta diversity um but again we don’t know if that’s not just due to chance and then my permanova test displayed that the ant community is significantly different between rural and urban sites. So because there is no significant difference in species richness or species diversity we can conclude that the number of ants on each individual land was the same and they both exhibited the same levels of diversity but the communities were really different meaning that we have different species taking advantage of each of those ecological niches and well that might be something that you would just assume, because of course, you know you’re looking at two different environments this is really important because a lot of the ants studied in the Arlington ecological communities were actually invasives, and they’re doing a lot of work in urban areas where they are more adapted than other species and where they are taking over habitat and they’re kind of taking over that um landscape and because ants are ecosystem engineers this is going to result in a level of ecological terraforming so the presence of tetramorium immigrans ants a (common invasive species in urban locations) far outweighed their presence in rural locations however as tetramorium ants become more prevalent in urban locations they will make their way to rural locations and they are already predisposed to succeed there and drive out other native species. Based on these results I think it is incredibly important to monitor our communities in northern Virginia as urbanization increases so that we can continue to predict environmental and ecological trends in our environment future implications for this research include analyzing and biodiversity in connection with vegetation testing to see which ant species could be considered ecological indicators for biotemperate regions and long-term observations of ant community dynamics as urbanization increases, and here’s my citations and references