Results I) Regional Survey

1
Factors Explaining Botrylloides violaceus Success
in Washington St. Fouling Communities
Erin Grey Department of Ecology Evolution,
University of Chicago, Chicago, IL 60637
Introduction In terrestrial and marine
habitats, it is generally accepted that species
diversity inhibits invasion success at small
scales because diverse communities fully utilize
resources1. In terrestrial habitat, at larger
spatial scales abiotic factors that favor
diversity also favor invasive success, thus
leading to an overall positive correlation of
diversity and invasive success at the regional
level2. Such larger studies are lacking for
marine habitats. The purposes of this study were
to I) document a large scale pattern of a marine
invasion and II) use smaller scale observation
and experimental studies to quantify the relative
contribution of biotic factors like competition
and predation to the success of the invader on
settlement plates.
II) Spatial Pattern

• Results I) Regional Survey
• Rarefaction curves leveled off across sites,
  suggesting that the sample effort was sufficient
  to capture differences between sites (Figure 2).
• Mean cover B. violaceus
• negatively correlated with
• measures of richness
• diversity (Table 1).
• Free space did not correlate

• Results II) Plate Dynamics
• Competition for Free Space
• Mean percent free space and B. violaceus cover on
  plates at each site
• Was calculated for each census date. No
  statistical analysis has been
• performed yet, but it is clear that free space is
  rarely limiting and that the
• abundance of B. violaceus cannot be well-explain
  by free space.
• Chiton Effect

Materials Methods I) Regional Survey 12
2424cm random photos were taken underneath docks
at 10 marinas with concrete floating docks in
early Sept, 2005. Photos were scored for species
identity, abundance free space. Salinity and
temperature were also recorded. II)
Plate Dynamics 2424cm acrylic plates were
deployed underneath docks at 4 local sites.
Plates were censused biweekly from May-Sep
2005-6 for species identity, species abundance,
free space and predators. The chiton index was
calculated by summing the number of hitons
found on a plate during the summer of 2006, then
dividing by the number of census dates.
Figure 2. Species Richness Rarefaction Curves
Sites
Figure 1. Map of Study Region
Species
Sample
Table 1. Spearmans ? for Site Means (plt.01,
plt..001)
An analysis of variance was performed to look at
the effect of chiton abundance (chiton index-
see Methods) on both cover B. violaceus (Fig.
5) and free space on plates (Fig. 6). Plates
were nested within sites, as there were
significant differences in chiton abundance among
sites. Chitons had no significant effect on B.
violaceus abundance but had a significant effect
in creating free space on plates (Fig. 6).
B S Alpha Free
B -0.88 -0.85 -0.16
S 0.95 0.17
Alpha .0.01
Washington, USA

• Temperature negatively correlated with richness
  and positively with cover of B. violaceus
  (Figure 3).
• B. violaceus R2 0.71, p 0.022
• Species Richness R2 -0.52, p 0.125

B. violaceus
chiton
Plate from John Wayne Marina

• Conclusions
• At the regional scale of this study, and in
  contrast to terrestrial studies, no positive
  correlation between diversity and invasion
  success was found.
• Free space is not correlated with either
  invasion success or diversity, implying that
  space-competition is not an important factor.
• Temperature appears to explain most of the
  variation in B. violaceus abundance in the
  region.
• Settlement plates observations also fail to find
  an obvious relationship between free space and B.
  violaceus abundance.
• Chiton abundance differs significantly among
  sites and effects the amount of free space, but
  has no effect on B. violaceus success.

Acknowledgements Special thanks to the Makah
Tribe, Pleasant Harbor Marina, John Wayne Marina,
Lopez Island Center for allowing me to conduct
surveys on their property for 3 years. Research
was funded by the EPA-STAR fellowship
(FP-91631001) and NSF-DDIG Grant (DEB-0608217)

• Literature Cited
• Stachowicz, J. J., et al. (2002). "Biodiversity,
  invasion resistance, and marine ecosystem
  function Reconciling pattern and process."
  Ecology 83(9) 2575-2590.
• Levine, J.M. (2000). Species diversity and
  biological invasions relating local processes to
  community pattern. Science 288 761-763