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Abstract BIOGEOGRAPHIC VARIATION IN THE RECRUITMENT OF NATIVE AND INVASIVE MARINE SESSILE INVERTEBRATE SPECIES Richard W. Osman The biogeographic variation in the timing and rates of recruitment
of sessile marine invertebrates is being examined by contrasting
recruitment to panel substrates exposed at sites in southern New
England (Connecticut), Chesapeake Bay (Maryland and Virginia), Indian
River Lagoon (Florida), and Belize. Panels were exposed for 1 week
periods at several sites in Connecticut and for 2 week periods at
all other sites. The general patterns observed were: 1) that recruitment
rates were often inversely correlated with diversity with the highest
rates seen in Chesapeake Bay and the lowest in Belize, 2) seasonal
variability in recruitment varied latitudinally, 3) the timing of
peak recruitment shifted latitudinally for some invasive species
and this timing shift can be related to temperature, 4) annual and
within-region variability in recruitment can be extremely high,
and 5) this variability can be related to temperature for some invasive
species but not for native species. The most dramatic pattern to
date is for the bryozoan Bugula neritina which recruits
in the winter in Florida and the late summer in Connecticut. From
historical data it appears that in recruits in the late spring in
North Carolina. The temperatures at these different recruitment
times are similar among sites, suggesting that recruitment patterns
reflect biogeographic variation in temperature. Within regional
differences in recruitment can also be quite dramatic with sites
separated by <1 km often differing by an order of magnitude in
their recruitment. These differences were seen in all regions. In
addition, differences between sites in species composition were
more prevalent at low-latitude sites. The within-region and biogeographic
variation in recruitment suggest that both invasion success and
the impact of climate change on recruitment and its consequences
will be complex.
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