Latitudinal gradients in benthic community composition in Western Atlantic estuaries

Abstract

Summary AimThe community composition of benthic macroinvertebrates from 295 estuarine sites was examined in order to either confirm or challenge established boundaries of zoogeographical provinces. We also investigated the postulate that, while local distributions were determined by natural habitat characteristics such as salinity, sediment type and depth, distributions on a large geographical scale would be correlated with temperature. LocationThe Atlantic coast of the United States (on a latitudinal gradient from 42° to 25°N). MethodsUsing the descriptive techniques of cluster analysis and nonmetric multi‐dimensional scaling, we determined the similarities in benthic community composition between sites within 1° latitudinal bands and compared the biotic ordinations to natural habitat characteristics such as salinity, sediment type and depth. We then evaluated the overall community composition within each 1° latitudinal band and established whether or not similarities existed between adjacent 1° latitudinal bands. In this manner, we were able to confirm that a latitudinal gradient existed in estuarine benthic community composition along the western Atlantic coast. This latitudinal gradient was demarcated by biogeographical boundaries at (1) Biscayne Bay, Florida, (2) the southern end of the Indian River Lagoon, Florida, (3) St John's River, Florida, (4) Cape Island, South Carolina, (5) the mouth of the Cape Fear River, North Carolina and (6) Cape Cod, Massachusetts, with a subprovince boundary just north of Cape May at Wildwood, New Jersey. ResultsThe major divisions approximated widely recognized biogeographical boundaries. Average summer water temperatures correlated better than sediment type, depth, or salinity with the latitudinal groupings of sites determined by cluster analysis. ConclusionsBased on this relationship, we speculate on the potential impacts of current global climate change scenarios on the distribution of benthic macroinvertebrates along the western Atlantic coast.

Vicariance and Dispersal Effects on Phylogeographic Structure and Speciation in a Widespread Estuarine Invertebrate

“…Focusing only on the northern species, clades N1 and N2 were distributed in formerly glaciated areas and diverged markedly when compared with clades N3 or N4 (both of which occurred in nonglaciated areas). This break coincides with the Acadian-Virginian transition zone, where glaciation and physical gradients have been invoked to explain a similar discontinuity in coastal species (Engle and Summers 1999;reviewed by Wares 2002 ; Fig. 3).…”

“…In contrast, the apparent lack of physical barriers, coupled with high dispersal potential, suggests that evolutionary mechanisms differ in diverse marine communities (Palumbi 1994;Myers 1997). However, as history, mode of development, and biogeographic zones appear to explain population structure in coastal areas, they may also play an important role in the determination of patterns of marine biodiversity (Engle and Summers 1999;Collin 2001;Wares 2002;Graham et al 2003). Indeed, glaciation has caused increased diversification and lineage extinction in northern coastal habitats (Hewitt 2000;Edmands 2001;Wares and Cunningham 2001;Marko 2004).…”

“…First, its direct development should reduce gene flow and increase population differentiation as compared to vagile or planktonic larval dispersers (Myers 1993;Bilton et al 2002;Cristescu et al 2003). Second, its oligomesohaline salinity distribution should preclude propagule dispersal in saline coastal environments, even though its distribution encompasses different zoogeographic zones (Engle and Summers 1999;Avise 2000;Wares 2002). Finally, the species is morphologically similar over its entire Northwest Atlantic range, one that includes formerly glaciated areas (Bousfield 1958(Bousfield , 1973.…”

The relative influence of geographic location and reach-scale habitat on benthic invertebrate assemblages in six ecoregions

“…Corkum (1989) reported that latitude and distance from the Pacific Ocean were important factors in Pacific Northwest invertebrate assemblages. Latitudinal gradients are more well established as a controlling factor for benthic invertebrate assemblages in coastal-marine waters, with Engle and Summers (1999) reporting that local distributions were determined by natural habitat variables, larger geographic distributions were influenced more by water temperature, which is related to latitude.…”

Genetic discontinuity in two high dispersal marine invertebrates in the northwest Atlantic

“…In the northwest Atlantic, biogeographic studies have identified major boundaries at Cape Hatteras, Cape Cod, and the mouth of the Bay of Fundy (Engle and Summers 1999;Wilkinson et al 2009;Hale 2010;Pappalardo et al 2015). Genetic studies of marine invertebrates spanning these boundaries show concordant patterns of population subdivision where coastal currents diverge at Cape Hatteras, and eddy-like currents at Cape Cod and the Bay of Fundy reduce alongshore transport of larvae (see Kelly et al 2006;Altman et al 2013;Govindarajan et al 2015).…”