SAUGEEN Introduction 2011.08
A pictorial guide to Saugeen is provided in 06B.10-15.
This locality has the longest management history and the fewest species (because of the limited range of borewidth diameters and competition for cavities), and interesting polymorphisms for the small Potter Wasp Symmorphus canadensis.
1. ISSUES SPECIFIC TO SAUGEEN
1a. Bicultures of sibling Potter species. The peculiarity of the Saugeen field site is that only the 2 smallest bore widths (Z=3.2 mm and A=4.8 mm) of the 5 available sizes have been deployed there 2002-6 (the few B = 6.4 mm BW blocks put out in 2007 were little used). The equipment has sooner or later been filled by bicultures of Symmorphus Potter Wasps (S. canadensis and S. cristatus, abbreviated as the species labels scA and scB). . I have been much interested in separating these 2 close species so as to record nest (spreadsheets) or sex ratio in relation to bore width (Ancilliary Data). I have used adult characters of Cummings (1989) and Matthias Buck (communications) and my own adult and prepupal characters. The workbook LABELS_TAXA in 03.02 has a page that keys an extensive range of nest labels to species names and labels.
1b. Separating the sibling species. The Potters in A (4.8 mm borewidth) cavities are almost entirely the generally larger species scB with stereotyped nests identifiable by diet (which is restricted to large black chunky greasy chrysomelid larvae) and overwintering prepupal colour (NBS colour names: vivid or brilliant Yellow). Very occasionally an old scB nest is used by scA. Small individuals of species scB can also be recognized in Z (3.2 mm BW) cavities.
The more frequent Potter in Z cavities is the generally smaller species scA whose nests can be identified by variable diet (small yellow weevil larvae or various mixtures of small and thin lepidopterous or coleopterous leaf miners) and variable prepupal colour, provided this is whitish ( NBS colour names: pale Yellow, yellowish White or pale Orange).
LABELS_TAXA attempts to be very conservative. Certain combinations of diet, prepupal colour and bore width identify species unambiguously (scA or scB), some are “forcibly” split with high confidence (e.g., species abbreviations scAf, scBf) while others are lumped into the arbitrary species group sAB. Similar treatment has been applied to nests where the diet is known but the prepupal colours could not be determined, e.g., because of early nest death, and to nests where the provisions are unknown because they had been totally consumed before inspection. For details see the key. Because the nest descriptors are always attached to the species abbreviation (e.g., whitish prepupae in mud nests with chrysomelid beetle provisions are entered in the records as sAB_wmb or scAf_wmb, depending on bore width) any marginal identifications can, if necessary, be reassigned to different species names as, e.g., part of a sensitivity analysis.
Nests with morphologically identified pinned emergent adults are labeled as scAp (scAp means pinned scA specimen in the Collection). A number of scA nests are now known with two or more prepupal colours within the same nest (05.04 ancilliary_data). Analysis of sex order in 15 “colour banded” nests does suggest that these are due to a succession of scA, or sometimes scA and scB, mothers, so intraspecific competition for nest space is a definite possibility, but because of the labour and difficulty of recognizing small colour differences in the field I no longer attempted to split such nests into a sequence of small nests after generation 2003.
As a vision scientist I know that naming the colours of small pale objects is difficult, particularly when the visual background is complex (References). Consequently more colours can be recognized in the laboratory, by extracting prepupae from their cocoons and sorting and massing them into large colour patches on a white ground, than can be recognized when the prepupae are left in largely intact cocoons in the nest block. Thus the number of nest descriptors that correspond to the single species name scA varies from year to year.
1c. Continuity of data. Because the Saugeen experience goes back to 1997 (see data in workbook SAUGEEN_Information) a special attempt has been made to improve the continuity between recent and early records. The sheets for generations 2001-3 offer good spatial records of hosts and parasitoids, a fair impression of the stage of nest death, and helpful counts of stage survivals. The records for generation 2004 have complete stage survival data, but some issues of nest competition are hard to judge because of the lack of dates within nest records prior to generation 2005.
1d. Summary analyses. The SOURCE data sheets for generations 2001-7 contain succinct details of the management of each stack of nest blocks and run to many data columns per nest cavity. The SUMMARY workbooks are basic counts (e.g., nest starts, nests harvested, that are pooled by species, generation and stand. It is hoped to add more of these.
2. LOCAL CIRCUMSTANCES
Prior to 2001 there was a changing configuration of hive stands (WES, MID, EAS, NOR, SOU and ESC, see early pages in WES spreadsheets) and nest block sizes, none of the stands more than 50 m from the current MID and WES stands.
MID and WES, woody swamp behind/open in front. PIO much the same but open front only 5-10 m before next woody swamp.
Both are at N44 12' W80 32', altitude 482m, Saugeen near Flesherton, Dundalk Highlands, S. Ont., at about a 100 m separation. MID and WES were founded respectively in 1998 and 2000 by pooling and culling the earlier nearby stands.
Prior to 2002 there was a varied mixture of nest blocks of all bore width sizes in the different hive stands. Since 2002 the MID and WES stands have contained equal numbers of 3.2 mm and 4.8 mm bore width (Z and A type) nest blocks stacked in an alternating pattern identical across the usually 6 hive boxes (apart from nest block face colourings).
3. DIFFERENCES BETWEEN THE WES AND MID HIVE STANDS
In general the two stands were treated identically except in generation 2004.
WES differs from MID (an equipment replicate) in the ratio of scA to scB in Z cavities, and in the relative frequencies of the sparse non-Potter species.
The WES and MID hive stands were harvested to roughly the same extent in Spring 2005 but in spatially different ways. About 2/3 of Potters were taken and 1/3 of the other species. At MID the harvest was close to a "clearcut", replacing all blocks in box 1XX, sparing 2XX and leaving only nonPotters in 3XX. At the WES stand the harvest was more locally selective. In box 1XX only nonPotters were spared in the A blocks and whitish Potter prepupae and nonPotters in the Z blocks. In 2XX all A blocks were replaced by empty blocks and only yellow Potter prepupae and non Potters spared in the Z blocks. In 3XX all Z blocks were replaced and all A blocks were spared.
In 2007 the stand was reduced to two boxes of nest block and data collection finished in 2008.
The accompanying document 'information' has an overview page that shows these general arrangements pictorially for generations 2001-8. Other pictorial pages give more detail for the individual stands. There are also species totals for 1997-2000, diagrams for polymorphisms, and a diary.
GPS: WES N44.20144 W80.53706, altitude 479m,
MID N44.20249 W80.53623, altitude 482m.
Separate estimate ; <135 m separation.
4. SPECIAL PROBLEM
Record spreadsheets, without the expansion of column W field records, are available for PIO hive stand generation 2001 and the terminal generation 2002 --and are included nearby. A special problem is that it is hard to avoid underestimating the numbers of failed Osmia tersula nests (species abbreviation otA_ma) and overestimating the count of nests emerged. This is because the parasitoid Sapyga martini dominated a forcefully hatched sample of generation 2001 otA, and the subsequent generation 2002 otA was much reduced. I.E., as it was not known in 2001-2 how to recognize sapygized nests, the numbers of overwintering cocoons is a poor guide as to the numbers of likely emerged or failed otA nests.
Although the dense field code in the PIO spreadsheets may eventually be expanded it is not thought urgent to include it in the major summary workbooks, e.g., SUMMARY_OF_NEST_COUNTS_BY_FATE.