Title

Dispersal, Recruitment and Habitat Invasibility in Shallow Epifaunal Communities of Southern New England

Date of Completion

January 2011

Keywords

Biology, Ecology|Biology, Oceanography

Degree

Ph.D.

Abstract

I use the shallow hard-substrate marine epifaunal community as a model system to explore how dispersal and recruitment processes influence community development. In particular I examine processes of invasion, priority effects, recruitment timing, propagule pressure and competition as important components of community structure. ^ First I addressed the influence of initial community composition on the development of communities by assessing the conditions when invasive species are likely to achieve dominance. I then examined the influence of temperature in altering community niche overlap and changing the timing of recruitment of both non-native and resident species in chapter 2. Our analysis showed that there is greater than or not significantly different community niche overlap than expected by chance and it is likely that recruits within the epifaunal community have strong interspecific competitive interactions because of high overlap in their seasonal recruitment patterns. Chapter 3 examines the timing of recruitment from a species richness point of view. Here we evaluate at what time of season species recruitment richness is the highest and compare resident species richness to non-native species richness. We utilized the mid-domain effect to understand its contribution to pattern formation. Mid-domain models show the potential to match empirical patterns of species recruitment diversity. Resident and invasive species show distinct differences in their agreement with the respective null models. In chapter 4 I described an experiment where we manipulated distance between epifaunal communities to examine the effect of community connectivity on species richness patterns. I reported on the changes of both regional and local patterns of community composition of the course of a season. In conclusion distance between local communities affects patterns of local species richness, and community similarity. ^ In chapter 5, I reported on the material properties of a recent invader to the New England coast. High elastic modulus relative to other colonial tunicates may be a primary mechanism that enables D. vexillum to inhabit and over grow pebble-cobble substrates; a substrate type that generally prevents other colonial ascidians from colonizing. The stiffness of D. vexillum could allow it to stabilize the sediments and prevent shiftingsediments to damage colonies. ^