Distribution of land hermit crabs and gastropod shell usage in mainland Puerto Rico (Project by JUAN NIEVES and ZUANIA COLON)
My first work as a technician for a big project was part of a grant from the SEEDS program, which lasted two years.
Very Brief Summary: Coenobita clypeatus is a land hermit crab found in coastal forest and rocky shores all over Puerto Rico. Gastropod shells are important for the growth of the crabs. Evidence that shows that the removal of shells from the habitat had caused the populations size structure to decrease. The objectives of the study were to describe the demography of C. clypeatus, to determine and compare densities of hermit crabs among rocky shores and coastal forest and to study gastropod shell use by hermit crabs. Preliminary results showed a difference in size of chelae and gastropod shell use between the two sampling sites. Read more here!
The roles of floral resource proximity to nesting substrate in wild bee nest-site selection
This was part of the NSF program - Research Experiences for Undergraduates. The study was conducted at Blandy Experimental Farm in Northern Virginia, Summer 2008.
Summary: Native bees are seen as an efficient alternative for pollination services in crop agriculture. We need to understand the habitat dynamics of native bees and proper management practices that will ensure their survival. In this study I tried to demonstrate how ground bee nest site selection is influenced by floral availability. The key question in this study is: Does host plant diversity and abundance in three abandoned field localities influence the decision of ground bees to nest on those sites?
Results Summary: Despite different species compositions between localities, we found localities to have similar levels of species diversity (p=.2924). Overall, floral species diversity was not correlated with the abundance of nesting bees per plot (Spearman; r>0.50 p=0.1995). Nevertheless, when broken down by field type, we found that the shrubland locality was positively correlated with abundance of nesting bees (r>0.50 p= .017) and could possibly reflect the characteristic vegetation structure of a shrub habitat. Although we could not sustain the idea that floral diversity was an important factor for nesting site selection per plot, the numbers of nesting bees per plot were positively correlated with the floral abundance of attractive flower species. These results support the theory that the proximity of nesting resources to abundant floral resources is important for ground-nesting bees even at small scales (plot) while the importance of floral diversity can only be seen at larger scales (locality).
Physicochemical effects on community structure in intertidal pools at the Western Cape Province, South Africa
By: Diana GC, Erin Wilkus and Amanda Frankel
Summary: Tidal pools occurring in the intertidal zone of rocky shores support a wide range species. The distribution of these species within the intertidal zone is strongly controlled by intense parameters set by their habitats (temperature range and percent oxygen in the water). These are believed to greatly impact the colonization of tidal pools. Pool size and distance from the shoreline may strongly affect the temperature and oxygen conditions in the tidal pools. Small pools that are further from the shore line are less susceptible to wave action are predicted to have extreme temperature ranges and lower percent oxygen in the water resulting in occupation by specialized organisms. Conversely, larger pools closer to the shoreline are predicted to support a wider range of species as they do not experience the harsh environments of smaller pools. Tidal pools occurring on the rocky shore of the southeastern coast of South Africa were sampled to assess whether this model provides an accurate description of physiochemical effects on intertidal pool species. Distribution of algae, sessile, slow moving, medium moving, and fast moving organisms across twenty tidal pools was analyzed to find differences in species composition, we measured conditions of large and small pools (size, distance from oceas, temprerature and oxygen). We predicted that how close or far a pool is from the ocean and the pool size will affect the physicochemical conditions of the pool and therefore the species within it.
Results Summary: Results support the postulations suggested by the island biogeography theory which states that larger pools are made up of more niches and can therefore support more species they are also easier to colonize due to their proximity to the ocean. The effects of oxygen, salinity, temperature, and pH on the number of species that colonized pools consistently affected each of the functional groups present. Our study shows that at this
temporal scale there are fluctuations in oxygen levels between night and day.
Therefore, organisms inhabiting the pools are likely adapted for extreme shifts in
oxygen in a short period of time. To see methods and complete results, click.
Elephant utilization of riparian tree species and the use of TPCs in Mapungubwe National Park
By: Diana GC, Matthew Nielsen, Elizabeth T. Kane, Taylor Gullet
Summary: Faidherbia albida, Ficus sycomorus, and Acacia xanthophloea occur in the gallery forest near the Limpopo river of Mapungubwe National Park (MNP). These tree species are being heavily impacted (consumed and or toppled) by elephants. Because of the increased impact, MNP has established “Tresholds for Potential Concern” (TPC) measurement for riparian tree species. Annual surveys of the trees are conducted to determine whether or not they are reaching a TPC level. These trees are impacted by elephants differently as well as respond differently to the detriment caused by elephant. Mainly elephant stripping and breakage are the causes of decreased health within these species populations. Also, the forest canopy is becoming thinned. This change is capable of changing the species
composition of the gallery forest system; canopy cover is also used as an
indicator of forest degradation that arises from the shift from closed canopy
to open canopy forest. In this study we evaluated the TPC established for elephant damage: 10% of trees of the indicator species
are 50% ring-barked over any one year period, the TPC for that certain species
is reached .
Results Sumary: Similar to previous surveys F. albida has reached the upper limits of the TPC due to stripping, while the others seem to be sustaining a stable level of population health despite stripping. In addition to determining if the TPC is being reached by any of these species, the cause of death for these trees needs to be determined. Along with the impact of elephants, other pressures exist and could be contributing to ultimate mortality of the trees, and we believe should be incorporated into the TPC. We found that the presence of borers greatly adds to the mortality of the trees once the bark has been stripped by elephants, and there is a direct association between borers and percent stripping. Check out the poster for the study here!
Historic land likely affects ground-dwelling ant community structure in longleaf pine savannas
By: Diana GC, Nick Reif, Brett Mattingly and John L. Orrock
Ants are widespread, influential organisms in terrestrial ecosystems. Although the impact of contemporary disturbances (e.g. habitat alteration and changing land use patterns) on ant species diversity and composition is well understood, historic disturbances (e.g. former agricultural practices) may also alter ant community structure due to legacy effects on soil characteristics and plant communities. Agricultural abandonment and subsequent forest regeneration is a widespread phenomenon in many terrestrial ecosystems. However, the manner in which this agricultural legacy affects present-day ant communities remains poorly understood. We evaluated ground-dwelling ant species abundance, diversity, and composition across a landscape mosaic of afforested agricultural fields and relict stands comprising upland longleaf pine savannas in the sandhills of North Carolina. At this study location, agriculture was abandoned ca. 1919.
We captured 2,917 individuals from 432 pitfalls open for 14 total days. Among the 10 species observed,Pheidole dentata,Pheidole morrisii, and Prenolepis imparis were the most abundant. Rarefaction curves indicated greater species richness in sites that lacked a history of agricultural land use. Furthermore, the steeper curve for these sites suggests a more even distribution among species on forested sites. Our results provide evidence that the legacy of agricultural land use could impact contemporary ant communities. Although agriculture was abandoned in this system ~90 yrs prior to this study, ant communities still exhibited significant differences in abundance and composition. Our results demonstrate that the structure of present-day ant communities can also be shaped by historic activities. Understanding the mechanisms underlying these legacy effects (e.g. changes in vegetation structure) will be important for fully characterizing the impact of past human activities on present-day ant communities.