Clumps Including More Than One Pollen Type

Clumps of pollen are often interpreted as the remains of anther fragments by archeological palynologists. Because of their greater mass per surface-area, these single-type clumps are used as indicators of short dispersal distance from the parent plant; i.e., the plant was growing near the site of sedimentation. However, the anther-fragment interpretation cannot be true from clumps of pollen containing more than one pollen type. These mixed-type clumps occur in various kinds of aquatic and terrestrial sediment. They are similar in size and shape to more common clumps of unidentifiable organic debris (FIGURE AT LEFT). The origin of the debris clumps and the mixed-type clumps is not known, but they may be fecal pellets of small arthropods.

Davis (1988) has noted clumped pollen in microscopic fecal pellets from Blackwater Draw, New Mexico, and has recovered them in 7 other archeological sites. This "fecal" type of pollen clump is easily differentiated from other pollen aggregates by its uniform size and shape. They are small (40 - 100 µm), oval pellets (LEFT) containing pollen or unidentifiable organic matter. About 5% contain identifiable pollen (OTHER FIGURES).

The pellets are particularly abundant in the surface sediment of dry caves (Davis, 1990), but they also are present in open, stratified archaeological sites (Davis, 1991). At an open site in coastal Orange County, California (CA-Ora-225), the pellets are more abundant than pollen (Davis, 1990). The pellets are less common, but present in aquatic sites (Davis 1992).

(From letter to E.J. Cushing dated 10/18/96)
The clumps are CLEARLY not artifacts of processing. Although the two- and several- type clumps sometimes fragment to have only five or six grains, they ordinarily have more. MORE IMPORTANTLY, they have a consistent form. They are oval, with the grains "packed" into a streamlined shape. Conifer grains in the "pack" are usually broken, and nearly all the grains are crumpled. . . .

I believe they are the feces of leaf-gleaning insects, pollinating flies, ground-dwelling mites, or termites. I believe they are most abundant below the surface, based on stratigraphic archaeological samples. I asked for illustrations of the feces of pollinating flies from the (polpal) list, but have received no response.

(From letter to E.J. Cushing dated 10/18/96) The pollen clumps are "stuck together" somehow. I look at intermediate steps in the pollen process sometimes, and the clumps are larger and "fluffy" before acetolysis, KOH, and dehydration. By the way, the larger (1-2 mm), wood-termite feces are preserved in aquatic sediments. Perhaps the termite's gut enzymes break down the cellulose and it forms a "glue." Or, maybe their enzymes can partially break down sporopollenin. Or, maybe the cohesion is largely due to the physical compaction in the gut. Regardless, the pellets are more compact and denser than the aquatic-organism pellets I've seen.

The pellets I'm seeing have passed through acetolysis, (and perhaps through an organism's digestive tract) and so must be comprised of more resistant compounds than cellulose.

By they way, there are lots of nice illustrations -- some in color!! -- of fecal pellets in Robbins et al. (1996).

 1988     Sources of pollen clumps found in archeological
     samples.  Abstract, American Association of
     Stratigraphic Palynologists.  November 10-12, Houston,

DAVIS, O.K. 1990 Pollen analysis of archeological sites. pp. J1 - J37 IN de Barros, P. and Koerper, H.C. (editors) Final test investigation report and request for determination of eligibility for 23 sites along the San Joaquin Hills transportation Corridor. Report by the Chambers Group, Inc., to Transportation Corridor Agencies, Costa Mesa, California.

DAVIS, O.K. 1991 Preliminary pollen analysis of ethnobotanical samples from Grasshopper Pueblo. Report to J. Welch, Anthropology, University of Arizona.

DAVIS, O.K. 1992 Rapid climatic change in coastal southern California inferred from pollen analysis of San Joaquin Marsh. Quaternary Research, 37:89-100.

DAVIS, O.K. and BUCHMANN, S.L. 1994 Insect sources of pollen clumps in archeological sites in Southwestern U.S.A.: ground-nesting bees and mites. AASP Contribution Series. 29:63-74

GOERTZ, A. 1992. On Parasitus coleopterorum - the Hitchhiker, in: YES Quarterly 9: 4-6.

ROBBINS, E.I., CUOMO, M.C., HABERYAN, K.A., MUDIE, P.J., CHEN, Y.-Y., AND HEAD E. 1996 Chapter 27. Fecal pellets; in: Jansonius, J. and McGregor, D.C. (ed.), Palynology: principles and applications; American Association of Stratigraphic Palynologists Foundation, vl. 3, p. 1085-1097.

Arthropods that eat feces [LINK]

Owen Davis 3/03