Biodiversity Findings | MARINe

Pacific Coast Biogeographic Patterns

Cladogram of Biogeographic Patterns

Channel Islands Biodiversity Groups

Voucher Collection

Last updated December 6th, 2016

Pacific Coast Biogeographic Patterns

The initial findings of the Biodiversity Surveys are striking. The surveys reveal distinct groups, where the composition of the intertidal communities is similar. Within some of the groups, smaller regions of similarity are found. Each region is represented by a different color on the map below.

In some cases, the results confirm previously known biogeographic boundaries, such as Point Conception. Point Conception is the northern/southern limit of many species of invertebrates and algae along the coast. In other cases, the results reveal new biogeographic boundaries such as Point Reyes, California.

Pacific Coast Biogeographic Patterns

Group 1 RED

Group 1 is made up of sites found in southeast Alaska and northern British Columbia. These four sites are less diverse and are dramatically different from any other sites to the south.

Group 2 BLUE

The largest region of similarity ranges from northern British Columbia to Point Reyes, California. Northern species of algae and invertebrates dominate this region.

The boundary between Group 1 and 2 has yet to be fully defined. Sites have been set up in southeast Alaska and British Columbia to investigate this.

Group 3 GOLD

The next largest span of similarity, Group 3, extends from Point Reyes, California to Point Conception, California. It is characterized by a combination of northern and southern invertebrate and algal species. High larval recruitment in this region also affects the composition of intertidal communities.

Group 4 PINK

Group 4 ranges from the southern part of Point Conception into Baja California Norte, Mexico and includes the Channel Islands. The Channel Islands are located south of Point Conception but are bathed by the cool waters of the California Current, giving them a unique mixture of northern and southern invertebrate and algal species. This same mixture of northern and southern species are found at the Baja California Norte, Mexico sites where upwelling occurs seasonally, exposing these sites to cold water.

Group 5 GREEN

Group 5 is situated in the middle of Group 4 and composed of sites in San Diego County and on Santa Catalina Island. This region is dominated by southern invertebrate and algal species that are found in the warm waters of the California Bight, which hugs the coastline in this area. Offshore islands also decrease the amount of wave impact. See Channel Islands Biodiversity for more information.

Group 6 PLUM

Group 6 is made up of the three southern sites in Baja California Mexico. Many species found at these sites are also found in the Gulf of California and are distinctly different from sites to the north.


Group 7, light blue line, is located in the Gulf of California along the coast of the Mexican state of Sonora. This Group represents an entirely different suite of species than the pacific coast. Four sites were surveyed here in 2002. Future plans for the Biodiversity Surveys include establishing new sites on various islands in the Gulf of California.

Cladogram of Biogeographic Patterns

Biodiversity patterns were based on the results of a cluster analysis using the Bray Curtis Similarity Index to look for similarities/differences among sites. The biogeographic groups were determined by the clustering patterns of the cladogram. The colored circles on the chart below represent different biogeographic groups.

Note that some sites in the middle of the diagram are not circled into groupings. These sites are each a sort of anomaly compared with the larger groupings. The reasons for their differences are not completely understood, but appear to be related to either:
1. Geographic characteristics; Mussel Flat is located on the remote and isolated Southeast Farallon Island; Lucia and Partington Point are both very steep, short and exposed benches or,
2. Sand scouring influence, evident at Sandhill and Terrace Point.

Pacific Coast Cladogram

The cladogram above shows the degree of relatedness between sites based on species composition and abundance. One can think of a cladogram like a family tree. Sites closer together on the tree are more similar in species composition and/or relative abundance than sites that are further apart. For example, sites found in the blue cluster are more similar to each other than they are to sites found in the purple or green clusters.

The length of the branch is also important when comparing sites. The shorter the branch, the more similar the species composition. For example, within the blue cluster the British Columbia sites have a species composition more similar to each other than to other sites in Washington, Oregon, or Northern California. There is a high degree of structure found within each branch. The structure of the Channel Islands is examined in more detail below.

Channel Islands Biodiversity Groups

When you compare species composition among sites, our 21 island sites separate out into three distinct groups. What is the driving force behind these biodiversity patterns? We looked at sea surface temperature, rock type, bathymetry, wave exposure, slope of bench, and the island on which a site was located. Preliminary results suggest that, the only factor that is consistant with the grouping pattern found by the cluster analysis was water temperature.

  1. The cold group represented by blue circles is made up of San Miguel Island, San Nicolas Island, Santa Rosa Island, the west end of Santa Cruz Island, and Frenchy's Cove on Anacapa Island.
  2. The mixed group represented by purple circles is made up of Santa Barbara Island, the east end of Santa Cruz Island and Middle on Anacapa Island.
  3. The warm group represented by red circles is the two sites on Santa Catalina Island.

Channel Islands Cladogram

A- Crook Point SMI, B- Cuyler Harbor, SMI, C- Fraser Point SCI, D- Trailer SCI, E- Johnson's Lee SRI, F- Ford Point SRI, G- Fossil Reef SCI, H - Marker Poles SNI, I- East Point SRI, J- Forney SCI, K - Frenchy's Cove AI, L- NW Talcott SRI, M- Thousand Springs SNI, N- Landing Cove SBI, O-Sea Lion Rookery SBI, P- Prisoners SCI, Q- Willows SCI, R- Valley SCI, S- Middle AI, T- Bird Rock CI, U- Little Harbor CI

Channel Islands Water Temperatures

Water temperature appears to be the driving force behind the biodiversity patterns seen on the Channel Islands. Islands that are continuously bathed by the cool California Current are represented by blue dots on the above map and the water around these sites is cooler than other sites within the Channel Islands. Sites denoted by purple have mixed current temperature. Part of the year the waters around these islands are cool while other times they are warm. The two sites on Santa Catalina Island in red are continuously bathed by the California Counter Current and have a much warmer ocean temperature.

Water temperature appears to play a significant role in biodiversity patterns at sites on the Channel Islands. The water temperature varies as little as one degree Celsius between cold and mixed sites. The effects of climate change may be reflected by changes in species composition found within the intertidal zone.

The map below shows the water temperature around the Channel Islands on 31 August 2003 ( Sea Surface Temperature image courtesy NOAA).

Example of water temperatures around the Channel Islands from 2003

Biodiversity Patterns within the Channel Islands

The biodiversity patterns were determined by comparing species composition between sites. The following analysis looks at why sites separate into three distinct groups. The relative abundance of both algae and invertebrate taxa varies greatly among the three temperature groups.

Fleshy red algae make up half of the algae found at cold-water sites, while coralline red algae make up a quarter of the algae found at cold-water sites. Brown and green algae make up the final quarter of algae found at cold-water sites. At mixed-water sites, brown and green algae continue to make up a quarter of the algae found at a site, but the relative abundance of red algae is more evenly distributed between coralline reds and fleshy reds. As you move to warm-water sites, the relative abundance of red algae remains evenly distributed between coralline reds and fleshy reds, but there is a dramatic increase of brown algae.

The relative abundance of sessile invertebrates also varies among the three groups. At cold-water sites, the composition of invertebrate community is comprised mostly by mussels (green), barnacles (orange), and colonial worms (yellow). In contrast, the community at the mixed-water sites is dominated by mussels (green), and at the warm-water sites by barnacles (yellow).

Relative abundance of algae on the Channel Islands Relative abundance of invertebrates on the Channel Islands

Voucher Collection

Pressing of a red alga

Voucher specimens were collected from 12 survey sites between November 2002 and July 2003. The purpose of the collection was to confirm the identification of species included in the Biodiversity Surveys and to increase the opportunity for future genetic and morphological research. Sites sampled between 2001-2002 were sorted into regional groups based on biological similarity. (See  Pacific Coast Biogeographic Patterns for more on the regional groups.) One representative site from each region was chosen for the voucher collection.

A sample of each species included in the survey data was collected. Samples of algae were pressed and are housed at the University of California Berkeley's University and Jepson Herbaria. Invertebrates collected are preserved in 95% ethanol and are housed at the California Academy of Sciences. Sensitive species were not collected.